Report 68-04-0020
BRAKE EMISSIONS: EMISSION MEASUREMENTS
FROM BRAKE AND CLUTCH LININGS
FROM SELECTED MOBILE SOURCES
M. G. Jacko
R. T. DuCharme
Bendix Research Laboratories
Bendix Center
Southfield, Mich. 48076
March 1973
Final Report for Period May 1971 - March 1973
Prepared for
ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Water Programs
Ann Arbor, Mich. 48105
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BRAKE EMISSIONS: EMISSION MEASUREMENTS
FROM BRAKE AND CLUTCH LININGS
FROM SELECTED MOBILE SOURCES
M. G. Jacko
R. T. DuCharme
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FOREWORD
The work described herein, "Emissions Measurements from Powered
Brake and Clutch Linings From Selected Mobile Sources," was performed
for the Office of Air and Water Programs, Environmental Protection
Agency, Ann Arbor, Michigan. This work was carried out under EPA Con-
tract 68-04-0020 from May 10, 1971 to March 31, 1973. The EPA Project
Technical Officer was Dr. Joseph H. Somers.
The program was contracted to Bendix Research Laboratories,
Southfield, Michigan. The work was performed in the Materials and Pro-
cesses Department, Dr. William M. Spurgeon, Manager, of the Mechanical
Sciences and Controls Laboratory, Mr. L. B. Taplin, Director. The program
was under the supervision of the Principal Investigator, Dr. Michael G.
Jacko.
Sections 4, 5, and 6 of this report were prepared by Mr. R. T.
DuCharme. The data base of Section 10 was prepared by Mr. A. R. Spencer.
All other portions were prepared by Dr. Michael G. Jacko.
Other contributors to the program were as follows: Mr. R. D.
Stapleton (sample collection, sample processing, calculations, and numer-
ous other tasks); Dr. R. M. Rusnak and Mr. D. G. Jones (microscopy analy-
ses); Mr. L. Smith (vehicle test driving); Mr. H. M. Danbert (vehicle
preparation and test driving); Mr. P. R. Stewart (fabrication of collec-
tors); Mr. T. N. Vinson (technical writer); Mr. J. Gulvezan, Mr. A. Tomala,
and Mr. W. R. Kee of Machine Systems Department (rotating seals designs),
and Mr. C. Cowan and Mr. C. Morton of Bendix Automotive Controls Systems
Group (information on vehicle testing and friction materials). Computer
programming and processing of computer data were performed by Miss J.
Lindsay. Mr. C. L. Gray and Mr. W. H. Houtman of EPA are acknowledged
for their suggestions incorporated into the brake emissions collectors.
Special thanks go to Dr. W. M. Spurgeon, Manager of the Materials
and Processes Department, for his encouragement and suggestions through-
out the program.
ii
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ABSTRACT
In order to define the extent of gas and particulate emissions from
automotive brakes (and clutches), a combination separation and storage
collection system was devised. Unique emissions collectors for both disc
and drum brakes and for a clutch were conceived, designed, and built as
the main embodiment of this instrumentation. The hardware was installed
on a vehicle which was then driven through various test cycles to deter-
mine the extent and type of brake emissions generated at low and high
operating temperatures. Typical driving conditions, such as the Detroit
Traffic Test, as well as more abusive driving conditions such as fade
tests, were included.
Typical original equipment and aftermarket friction materials for
both disc and drum brakes were used in the tests. Brake relines were
made to simulate typical consumer-type practices. The brake emissions
generated were removed from the various collectors and mass balances
were performed. The particulates were processed and analyzed by a com-
bination of optical and electron microscopy to ascertain the asbestos
content and the asbestos particle size distribution in the wear debris.
Comparisons of emissions from new and used friction materials, disc and
drum brakes, and original equipment and aftermarket materials were made.
Finally, an estimate was made of the total emission of asbestos by all
of the vehicles in the country: on the average, more than 99.7 percent
of the asbestos is converted; the contribution to the atmosphere is 5060
pounds, or 3.2 percent of the total asbestos emissions.
iii
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TABLE OF CONTENTS
Page
SECTION 1 - INTRODUCTION AND BRIEF SUMMARY 1~1
SECTION 2 - OBJECTIVES AND BACKGROUND 2~1
2.1 Objectives 2~1
2.1.1 Objectives of this Program 2~1
2.1.2 Bendix Technical Approach 2~1
2.1.2.1 Select Suitable Vehicle and Friction
Materials 2~1
2.1.2.2 Conceive, Design, and Build Brake
and Clutch Emissions Collectors 2-1
2.1.2.3 Test a Typical Collector and Instrument
the. Vehicle 2-1
2.1.2.4 Select and Run Suitable Driving Test
Schedules
2.1.2.5 Collect and Analyze Emissions 2-2
2.1.2.6 Estimate Asbestos Emissions for Cars
and Trucks 2-2
2.2 Prior Work 2~2
2.2.1 Published Data 2~2
2.2.2 Unpublished Data 2~3
2.3 Background 2~3
2.3.1 Energy Absorption by Friction Materials 2-3
2.3.1.1 Brakes 2~3
2.3.1.2 Clutches 2~3
2.3.2 Compositions of Friction Materials 2~4
2.3.2.1 Generalized Classifications 2~4
2.3.2.2 Asbestos 2-4
2.3.2.3 Resin Binders 2-5
2.3.2.4 Property Modifiers 2-5
2.3.2.4.1 Non-Abrasive Modifiers 2-8
2.3.2.4.2 Abrasive Modifiers 2-8
2.3.3 Friction Material Reactions 2-8
2.3.3.1 Absorption and Conversion of Energy 2-8
2.3.3.2 Physical and Chemical Changes in
Linings During Use 2-9
2.3.4 Brake Lining Wear Mechanisms and Generation
of Emissions 2—13
2.3.4.1 Types of Wear Mechanisms 2-13
v
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Page
2.4
2.3.4.1.1 Thermal Wear
2.3.4.1.2 Abrasive Wear
2.3.4.1.3 Adhesive Wear
2.3.4.1.4 Fatigue Wear
2.3.4.1.5 Macroshear Wear
2.3.4.2 Predominant Wear Mechanisms
2.3.4.3 Wear Equation
2.3.5 Emissions of Particulate and Gaseous Emissions
2.3.5.1 Drum Brakes
2.3.5.2 Disc Brakes
2.3.5.3 Clutches
2.3.6 Distribution and Changes in Brake and Clutch
Emissions
References
SECTION 3 - MATERIALS SELECTIONS
3.1
3.2
Background
Materials Selections for Program
3.2.1 Friction Material Selections
3.2.2 Contents of the Friction Materials
SECTION 4 - VEHICLE AND INSTRUMENTATION
4.1
4.2
Vehicle Description
Brake Test Instrumentation
SECTION 5 - EMISSIONS COLLECTION SYSTEMS
5.1
5.2
5.3
5.4
Operation Requirements
5.1.1 Operation and Design Criteria
5.1.2 Emission Expected
Overall Design Concept
5.2.1 Air Flow of a Typical Collection System
5.2.2 Collection Systems Used
5.2.3 Electrical System
Particulate Filters
5.3.1 Filter Holders
5.3.2 Filter Flow Characteristics
Gas Collection Systems
5.4.1 Design and Fabrication of Traps
5.4.2 Operation
2-13
2-16
2-16
2-19
2-19
2-21
2-21
2-23
2-23
2-23
2-24
2-24
2-25
3-1
3-1
3-1
3-1
3-3
4-1
4-1
4-2
5-1
5-1
5-1
5-2
5-2
5-2
5-5
5-5
5-5
5-5
5-9
5-9
5-9
5-14
vi
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Page
5.5 Disc Brake Collector 5-14
5.5.1 Shroud Design and Construction 5-14
5.5.2 Rotating Seal 5-14
5.5.2.1 Initial Design and Problems 5-14
5.5.2.2 Final Design 5-22
5.5.3 Thermal Control Aids 5-22
5.6 Drum Brake Collector 5-27
5.6.1 Initial Designs and Rotating-Seal Problems 5-27
5.6.2 Final Design 5-31
5.7 Clutch Collector 5-31
SECTION 6 - INERTIA DYNAMOMETER TESTING OF THE DISC-BRAKE
COLLECTOR SYSTEM 6-1
6.1 Objectives 6-1
6.1.1 Demonstration of Collection System Operation 6-1
6.1.2 Thermal Response 6-1
6.1.3 Rotating Seal Durability 6-1
6.2 Dynamometer Test Results 6-1
6.2.1 Sealing Practices for Disc Brake Collector 6-1
6.2.2 Thermal Response Results 6-2
6.2.3 Rotating Seal Operation 6-2
6.2.4 Emission Collections 6-7
6.2.5 System Integrity 6-10
SECTION 7 - VEHICLE TEST SCHEDULES 7-1
7.1 Rationale 7-1
7.1.1 Brakes 7-1
7.1.2 Clutches 7-1
7.2 Typical Test Cycles 7-1
7.2.1 Burnish 7-1
7.2.2 Baseline 7-2
7.2.3 Detroit Traffic Test 7-2
7.2.4 10-Stop Fade and Recovery 7-4
7.2.5 15-Stop Fade and Recovery 7-4
7.2.6 Reburnish 7-4
7.3 Selected Vehicle Driving Schedule 7-5
7.3.1 Burnish 7-5
7.3.2 After-Burnish (A.B.) Baseline 7-5
7.3.3 Detroit Traffic Test 7-5
vii
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7.3.4 10-Stop Fade and Recovery 7~^
7.3.5 After-Fade (A.F.) Baseline ~7
7.3.6 15-Stop Fade and Recovery 7 7
7.3.7 Final Baseline
SECTION 8 - SAMPLING AND ANALYTICAL PROCEDURES 8~1
8.1 Rationale Based on Collector Designs
8.1.1 Particulate Emissions Collection
8.1.2 Gaseous Emissions Collection
8.2 Particulate Emissions Removal From Collectors 8~1
8.2.1 Collection of Particulate Emissions 8~1
8.2.2 Disc Brake Samples 8~1
8.2.3 Drum Brake Samples 8~3
8.2.4 Clutch Samples 8~3
8.2.5 Improved Friction Material Weighing Procedure 8~3
8.3 Analytical Problem Definition 8~3
8.3.1 Composition of Wear Debris 8~3
8.3.2 Analytical Methods for Asbestos and Their
Rationale 8~4
8.3.3 Microscopy Methods for Asbestos 8~°
8.4 Bendix Analytical Method for Analysis of Asbestos
in Brake Emissions 8~7
8.4.1 Criteria and Flow Chart 8~7
8.4.2 Analysis of Brake Emissions 8-7
8.4.3 Representative Sampling and Low Temperature
Ashing (LTA) 8~7
8.4.4 Sample Distribution for Microscopy 8-12
8.4.5 Selected Microscopy Methods 8-15
8.4.5.1 Initial Studies and Rationale 8-15
8.4.5.2 Optical Microscopy Analysis for
Asbestos 8-16
8.4.5.3 Transmission Electron Microscopy
Analysis for Asbestos 8-16
8.4.6 Calculations From Microscopy Results 8-18
8.4.6.1 Rationale and Microscopy Count Sheet 8-18
8.4.6.2 Sample Calculation 8-19
8.4.6.3 Computerization of Calculations and
Particle Size Distribution 8-26
8.4.7 Possible Sources of Error 8-26
viii
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8.5 Analysis of Gaseous Emissions
8.5.1 Method of Analysis 8~28
8.5.2 Gas Handling System 8"30
8.5.3 Calibration of Gas Chromatograph 8~33
8.5.4 Problems and Interferences 8-33
8.6 References 8~36
SECTION 9 - VEHICLE TEST RESULTS 9~1
9.1 Vehicle Operations 9-1
9.1.1 Test Scheduling and Problems Encountered 9-1
9.1.2 Mileage Accumulations 9-5
9.1.3 Reporting of Vehicle Test Data 9-5
9.2 Performance of Emissions Collection Systems 9-5
9.2.1 Rotating Seal Life 9-5
9.2.2 Operating Temperatures 9-8
9.2.2.1 Normal Brake Stops 9-8
9.2.2.2 Heavy-Duty Fade Stops 9-12
9.2.3 Collection Efficiencies 9-15
9.2.3.1 Recovery of Brake. Particulate Emission 9-15
9.2.3.2 Mass Balance 9-19
9.2.3.2.1 Amount of Emissions 9-19
9.2.3.2.2 Distribution of Emissions 9-19
9.3 Percent Asbestos Contents 9-24
9.3.1 Program Results 9-24
9.3.2 Battelle Analyses 9-28
9.3.3 Johns-Manville Analyses 9-28
9.3.4 Comparison of Asbestos Analytical Results 9-28
9.4 Asbestos Emissions Factors 9-30
9.5 Asbestos Emissions Trends 9-37
9.5.1 New versus Burnished Materials 9-37
9.5.2 Disc versus Drum Brake Materials 9-37
9.5.3 Heavy (Abusive) versus Moderate Duty 9-39
9.5.4 Effects of Friction Materials 9-41
9.5.5 Airborne versus Sump versus Surfaces Samples 9-43
9.6 Changes in Lining Wear Rate After Use at Higher
Temperatures 9-46
9.7 Results of Gaseous Emissions Analyses 9-46
9.7.1 Summary of Analytical Methods Attempted 9-46
9.7.2 Gaseous Emissions Detected 9-48
9.7.3 Shroud Extract Analysis 9-53
ix
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SECTION 10 - ESTIMATED EMISSIONS FOR CARS AND TRUCKS
10.1 Approach
10.2 Supplementary Data Base
10.2.1 Number of Vehicles in Use
10.2.2 Motor Vehicle Usage
10.2.3 Estimates of Brake Usage and Abuse
10.2.4 Asbestos in Friction Materials
10.2.5 Amount of Friction Material Actually Worn
10.3 Interpretation of Test Results
10.4
10.3.1
10.3.2
Factors Influencing Rate of Emissions
Weighting Factors
10.3.2.1 Distribution Weighting Factors
10.3.2.1.1 Location of Wear Debris
10.3.2.1.2 Comparison of Normal versus
Shrouded Brakes
10.3.2.1.3 Summary
10.3.2.2 Severity Weighting Factors
10.3.2.2.1 New versus Burnished
Friction Materials
10.3.2.2.2 Severe or Abusive Braking
10.3.2.2.3 Renewal of Friction Surface
10.3.2.2.4 Normal Brake Operation
10.3.2.3 Summary
10.3.3 Asbestos Emissions Per Vehicle
10.3.3.1 Total Asbestos Emissions Estimate
10.3.3.2 Asbestos Emissions and Their Fate
Estimated Asbestos Emissions
10.4.1 Passenger Vehicles
10.4.1.1 Total Asbestos Emissions
10.4.1.2 Distribution of Asbestos Emissions
10.4.2 Trucks and Buses
10.4.2.1 Estimated Severity Factors
10.4.2.2 Estimated Emissions Factors
10.4.2.3 Calculations of Total Asbestos
Emissions for Trucks and Buses
10.4.2.4 Total Truck Asbestos Emissions
10.4.2.5 Distribution of Truck Asbestos
Emissions
Page
10-1
10-1
10-1
10-1
10-4
10-4
10-9
10-15
10-16
10-16
10-18
10-18
10-18
10-19
10-22
10-23
10-23
10-23
10-24
10-24
10-24
10-24
10-24
10-25
10-25
10-25
10-25
10-25
10-28
10-28
10-28
10-29
10-31
10-32
x
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Page
10.4.2.5.1 Estimated Distribution
Weighting Factors 10-32
10.4.2.5.2 Truck Asbestos Emis-
sions and Their Fate 10-32
10.4.3 Estimated Asbestos Emissions 10-32
10.4.4 Alternate Estimate for Total Asbestos Emissions 10-34
10.5 Summary of Asbestos Emissions 10-37
10.6 References 10-38
SECTION 11 - SUMMARY 11-1
APPENDIX A - WEAR DEBRIS CALCULATIONS A-l
APPENDIX B - NUCLEPORE FILTER FLOW CHARACTERISTICS FOR
BRAKE LINING WEAR DEBRIS B-l
APPENDIX C - COLLECTION OF BRAKE AND CLUTCH EMISSIONS C-l
APPENDIX D - ANALYSIS OF BRAKE AND CLUTCH EMISSIONS D-l
APPENDIX E - ELECTRON MICROSCOPY ANALYSIS OF BRAKE
EMISSION SAMPLES E-l
APPENDIX F - COMPUTER PROGRAM FOR COMPUTATION OF ASBESTOS
CONTENT USING ANALYTICAL MICROSCOPY TECHNIQUES F-l
APPENDIX G - VEHICLE TEST DATA REPORTS G-l
APPENDIX H - ASBESTOS EMISSIONS ANALYSIS REPORTS FROM
BATTELLE COLUMBUS LABORATORIES AND JOHNS-
MANVILLE RESEARCH AND ENGINEERING CENTER H-l
xi
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LIST OF ILLUSTRATIONS
Figure No. Title Page
2-1 Schematic Structure of Chrysotile Asbestos 2-6
2-2 DTA and TGA Thermograms for Chrysotile Asbestos
(Bendix Data) 2-6
2-3 X-Ray Diffraction Patterns of Heated Chrysotile
Asbestos (Bendix Data) 2-7
2-4 Photomicrograph of Brake Lining Cross Section
after 8550 Miles of Test-Track Service 2-10
2-5 Electron Micrograph of Friction Material Wear
Debris (Made during 1966 studies.) - 10,OOOX 2-10
2-6 Close-Up View of Bendix Drag Dynamometer
Showing Wear Debris Collector 2-11
2-7 Photomicrograph of Cross Section of Friction
Material Test Specimen after More than 10
Successive Stops from 100 mph on Bendix1
Full-Brake Dynamometer 2-11
2-8 Changes Occurring in the Friction Material as
the Temperature Rises 2-12
2-9 Changes Occurring in the Rotor as the Temperature
Rises 2-12
2-10 Mechanism of Explosive Thermal Wear 2-15
2-11 Mechanism of Two-Body Abrasive Wear 2-17
2-12 Mechanism of Three-Body Abrasive Wear 2-17
2-13 Scanning Electron Photomicrograph Showing
Abrasive Wear Tracks on Friction Material
Surface and Adherent Wear Debris Particles 2-18
2-14 Mechanism of Adhesive Wear 2-18
2-15 Mechanism of Fatigue Wear 2-20
2-16 Mechanism of Macroshear Wear 2-20
2-17 Predominant Wear Mechanisms of Friction
Materials 2-22
2-18 Variation of Friction Material Wear with
Temperature 2-22
4-1 Vehicle Instrumentation for Friction Material
Testing 4-3
5-1 Schematic Diagram for Air Flow of Typical
Particulate and Gas Emission Collection System 5-3
5-2 Air Pump Installation in Engine Compartment 5-4
5-3 Vehicle Instrumentation (Front Seat Area) 5-6
5-4 Vehicle Instrumentation (Rear Seat Area) 5-7
5-5 Electrical Schematic for Particulate Trap and
Transfer Line Heaters 5-8
5-6 Condensable-Gas Trap 5-10
5-7 Activated-Charcoal Gas Trap - Sectional View 5-11
xiii
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Figure No. Title
5-8 Activated-Charcoal Gas Trap - Top View 5-11
5-9 Activated-Charcoal Gas Trap 5~12
5-10 Exploded View of Activated-Charcoal Gas Trap 5-13
5-11 Gas Collection System 5~15
5-12 Sectional View of Disc Brake Shroud 5-16
5-13(a) Major Portions of Disc Brake Emission Collector
S 1 7
Assembly J--L/
5-13(b) Major Portions of Disc Brake Emission Collector
Assembly
5-14 Disc Brake Emission Collector Assembly -
Exploded View 5 9
5-15 Front Disc Brake Emission Collector Installed
on Vehicle 5~20
5-16 Back View of Front Disc Brake Emissions Collector
S—21
Showing Instrumentation J
5-17 Initial Design (Mkl) for Rotating Seal of Disc
Brake Collector 5-22
5-18 Rotating Seal for Disc Brake Emission Collector 5-23
5-19 Details of Disc Brake Collector Rotating Seal 5-24
5-20 Front Disc Brake Emissions Collector Showing
Thermal Control Aids 5-25
5-21 Right Front Wheel of Test Vehicle 5-26
5-22 First Seal Design (Mkl) for Drum Brake) 5-27
5-23 Mkll Rotating Seal for Drum Brake Emission
Collector 5-28
5-24 Details of Mkll Rotating Seal 5-29
5-25 Rear Drum Brake Emission Collector 5-30
5-26 Rear View'of Rear Drum Brake Emissions Collector
Showing Instrumentation 5-32
5-27 Completely Worn Seal from MKII Rear Drum Brake
Collector 5-32
5-28 Sectional View of Drum Brake Shroud (MKIII) 5-33
5-29 Outboard View of Rear Drum Brake Emissions
Collector Interior 5-34
5-30 Assembled Rear Drum Brake Emissions Collector 5-35
5-31 Inboard View of Assembled Rear Drum Brake
Emissions Collector 5-36
5-32 Emission Collection System for Clutch 5-37
5-33 General View of Covered Clutch 5-38
6-1 Disc Brake and Emissions Collector Assembly
Installed on Dynamometer 6-3
6-2 Disc Brake Comparative Thermal Response Time
(Static Air) 6-4
6-3 Comparative Thermal Response Tests on a
Disc Brake 6-4
6-4 Seal Leakage versus Flow for Disc Brake Emissions
Collector Showing Differences between Dry and
Lubricated Seals 6-5
xiv
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Figure No. Title
6-5 Seal Leakage Rate versus Speed Showing
Differences between New and Used Seal 6-5
6-6 Seals from Disc Brake Emissions Collector
Showing Normal and Abnormal Wear 6-6
6-7 Rotating Seal Leakage Rate versus Wheel Speed
for Disc Brake Emissions Collector 6-8
6-8 Disc Brake Emission Collector Temperature 6-9
8-1 Thermal Analysis of Wear Debris 8-5
8-2 Flow Chart for Particulates Analyses 8-9
8-3 Representative Sampling for Analysis 8-10
8-4 Wear Debris Collected on 8u Nuclepore Filter 8-10
8-5 Low Temperature Ashing 8-11
8-6 SEM Photomicrographs of LTA Wear Debris Samples 8-13
8-7 Uniform Sample Distribution onto Filter 8-14
8-8 Phase Contrast Optical Microscopy at 400X 8-17
8-9 Phase-Contrast Photomicrograph of Wear
Debris - 400X 8-17
8-10 Transmission Electron Microscope 8-18
8-11 Asbestos Fiber in Brake Emission 8-20
8-12 Microscopy Count Sheet 8-21
8-13 Fiber Volume Calculations 8-22
8-14 Computer Printout of Asbestos Analytical Results 8-23
8-15 Variation of Maximum Deviation of Asbestos
Analytical Results with Asbestos Percent Found 8-30
8-16 Gas Handling System 8-31
8-17 Gas Handling System and Gas Chromatograph 8-32
8-18 Detector Response for Carbon Dioxide 8-34
8-19 Typical Calibration Chromatogram for Low
Molecular Weight Gas 8-35
9-1 Brake Temperature Data - Vehicle Test 1,
10-Stop Fade 9-13
9-2 Brake Temperature Data - Vehicle Test 1,
15-Stop Fade 9-14
9-3 Decrease in Clutch Airborne Asbestos Emissions
with Continued Normal-Duty Service 9-39
9-4 Variation of Asbestos Emissions During Moderate
Duty with Asbestos Content of Disc Pads 9-42
10-1 Frequency Distribution of Braking Decelerations 10-11
10-2 Variation of Wear Debris Retention with Mileage
(for Rear Drum Brakes) 10-22
xv
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LIST OF TABLES
Table No. Title
2-1 Composition of Typical Automotive Friction
Materials (Volume Percent)
2-2 Wear Mechanisms in Friction Materials
3-1 Vehicle Configurations and Lining Selections
3-2 Surface Roughness Measurements on Turned Discs
and Drums for Vehicle Test 3
3-3 Estimated Asbestos Content
4-1 Test Vehicle Description
6-1 Summary of Dynamometer Test Results
7-1 Detroit Traffic Test Route (Modified)
7-2 Vehicle Test Schedule
8-1 Comparison of Disc Brake versus Drum Brake
Operating Conditions
8-2 Samples Produced by Brake Emissions Collection
8-3 Estimated Chemical Composition Characteristics
of Wear Debris
8-4 Transmission Electron Microscopy Methods
8-5 Sample Calculation
8-6 Possible Sources of Error
8-7 Extent of Error in Asbestos Emissions
Analytical Results
9-1 Actual versus Estimated Test Schedules for
Vehicle Test 1
9-2 Actual versus Estimated Test Schedules for
Vehicle Test 2
9-3 Actual versus Estimated Test Schedules for
Vehicle Test 3
9-4 Summary of Vehicle Mileage Accumulations
9-5 Running Log of the Rotating Seals Mileages
Obtained in the Vehicle Test Program
9-6 Rotating Seal Life (Miles)
9-7 Brake Temperatures During Burnish Tests (°F)
(Vehicle Test 1)
9-8 Brake Temperatures During Detroit Traffic Circuits
(Vehicle Test 2 - A.B. Baseline)
9-9 Weights of Brake Particulate Wear Debris
Collected (Vehicle Test 1) (gm)
9-10 Weights of Particulate Wear Debris Collected
(Vehicle Test 2) (gm)
9-11 Weights of Brake Particulate Wear Debris
Collected (Vehicle Test 3) (gm)
9-12 Brake Friction Material Initial Weights and
Weight Losses (gm)
9-13 Material Percent Recovery as Particulate
Emissions (Vehicle Test 1)
xvii
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Table No. Title Page
9-14 Material Percent Recovery as Particulate Emissions
(Vehicle Test 2) 9-22
9-15 Material Percent Recovery as Particulate Emissions
(Vehicle Test 3) 9-23
9-16 Summary of Asbestos Analytical Restuls (Vehicle
Test 1) (Weight Percent) 9-25
9-17 Summary of Asbestos Analytical Results (Vehicle
Test 2) (Weight Percent) 9-26
9-18 Summary of Asbestos Analytical Results (Vehicle
Test 3) (Weight Percent) 9-27
9-19 Comparison of Analytical Results for Asbestos 9-29
9-20 Weight of Asbestos Generated During Braking
(Vehicle Test 1) (mg) 9-31
9-21 Weight of Asbestos Generated During Braking
(Vehicle Test 2) (mg) 9-32
9-22 Weight of Asbestos Generated During Braking
(Vehicle Test 3) (mg) 9-33
9-23 Weight of Asbestos Generated During Braking
(Vehicle Test 1) (pg/mile) 9-34
9-24 Weight of Asbestos Generated During Braking
(Vehicle Test 2) (yg/mile) 9-35
9-25 Weight of Asbestos Generated During Braking
(Vehicle Test 3) (yg/mile) 9-36
9-26 Summary of Clutch Asbestos Emissions 9-38
9-27 Comparison of Asbestos Emission from New and
Burnished Materials 9-38
9-28 Asbestos Emissions from Heavy-Duty Tests 9-40
9-29 Comparison of Asbestos Emissions Generated by
Different Friction Materials 9-42
9-30 Comparison of Asbestos Emissions for Various
Sample Locations (yg/mile) 9-44
9-31 Summary Comparison of Surfaces, Sump, and Airborne
Samples 9-45
9-32 Change in Lining Wear Rate after Operation at
Increased Temperatures (Vehicle Test 2) 9-47
9-33 Data Analysis of Gaseous Emissions (Vehicle Test 1) 9-49
9-34 Data from Analysis of Gaseous Emissions
(Vehicle Test 2) 9_50
9-35 Elution Order from Poropak Q 9-51
9-36 Elution Order from W-98 9-52
10-1 U. S. Braked Motor Vehicle Population in 2
10-2 U. S. Braked Trailer Population ' -,« ?
10-3 U. S. Motor Vehicles with Dry Clutches 103
10-4 Yearly Additions to U. S. Braked Vehicle Population inl*
10-5 Motor Vehicle Usage by Vehicle Type and Roadway Tn s
10-6 Type and Usage of Public Roads 10-5
10-7 Motor Vehicle Usage by Purpose of Trip 10-6
10-8 Motor Vehicle Usage by Length of Trip 1Q-6
kviii
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Table No.
Title
10-9 Results of Cross-Country Brake Test Trip 10-8
10-10 Where Vehicles Are Used 10-8
10-11 Some U. S. Driving Characteristics 10-10
10-12 Brake Applications Per Mile 10-10
10-13 Asbestos Content of Automotive Friction Materials 10-11
10-14 Brake Friction Material Weights for Test Vehicle 10-12
10-15 Number of Newly Surfaced Rotors Used Each Year 10-12
10-16 Compilation of Annual Motor Vehicle Brake Friction
Material Usage 10-13
10-17 Compilation of Annual Clutch Friction Material
Usage 10-14
10-18 Relative Brake Relining Frequency 10-14
10-19 Total Asbestos Emissions Calculated from the Test
Vehicle (Average for the Three Vehicle Tests) 10-26
10-20 Distribution-Weighted Asbestos Emissions from the
Test Vehicle 10-27
10-21 Estimate for Total Asbestos Emissions Expected for
a Light Truck 10-29
10-22 Estimate of Total Asbestos Emissions Expected for
a Medium Truck 10-30
10-23 Estimate of Total Asbestos Emissions Expected for
a Heavy Truck 10-30
10-24 Distribution-Weighted Asbestos Emissions from a
Light Truck 10-31
10-25 Summary of All Brake and Clutch Emissions
(Ibs per year) 10-31
10-26 Calculation of Weighted Average Unconverted
Asbestos Percent for Sump Sample 10-34
10-27 Calculation of Weighted Average Asbestos Percent
for Surfaces Sample 10-34
10-28 Calculation of Weighted Average Asbestos Percent
for Airborne Samples 10-36
10-29 Data and Calculation of Weighted Asbestos Percent
for All Vehicles. 10-36
xix
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SECTION 1
INTRODUCTION AND BRIEF SUMMARY
The chrysotile form of asbestos is a major constituent in automo-
tive brake linings and disc pads, and in the friction materials used in
clutches. These components are expendable. In typical passenger car
service, drum linings wear out in about 40,000 miles, disc pads in about
30,000 miles, and clutch facings in about 70,000 miles. There are, of
course, wide variations in the service lives of these components, which
depend on the nature of the friction materials used, on driver habits,
and on driving conditions.
The expendable members of the common automotive friction couples
contain not only asbestos, but also various organic and inorganic fric-
tion and property modifiers. These constituents are bound together by
phenolic resins. Because of their high content of organic substances,
such friction materials are classified as "organic." Asbestos-free
friction materials with a high content of metallic substances are classi-
fied as "semi-metallic." Over 99 percent of the automotive friction ma-
terials used today are organics.
The mechanisms by which organic friction materials wear can be
classified under five headings: thermal, abrasive, adhesive, macroshear,
and fatigue. Thermal, abrasive, and adhesive wear are considered to be
the most important mechanisms, thermal wear predominating above 450°F,
abrasive and adhesive wear predominating below 450°F (the temperature
being measured by a thermocouple in the rotor, about 0.050 inch from
the sliding interface). The organic constituents pyrolyze or oxidize,
and are emitted to the air as carbonaceous solid particles or gaseous
reaction products. The asbestos fibers are pulverized into small parti-
cles which are trapped in the brake (or clutch) housing, or fall to the
road, or are emitted to the air. Disc brakes do not trap as much as
drum brakes. Most of the asbestos is heated to temperatures high enough
to cause chemical conversion, and is therefore trapped or emitted as
olivine or forsterite particles.
When the large number of existing cars and trucks is considered,
each with eight or more pieces of friction material in the brake system,
plus more in the clutch mechanism, it becomes apparent that an air pollu-
tion problem may exist. Considered in another light, there are perhaps
one billion pieces of friction material in vehicles in the United States,
gradually being pyrolyzed and ground to dust. The brake systems in the
vehicles utilizing these friction materials can thus be considered as
chemical reactors, each emitting organic and inorganic compounds, includ-
ing asbestos and its decomposition products, to the atmosphere. The com-
positions of the gaseous and solid emissions have not been well known,
1-1
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and the particle sizes and shapes of the solid emissions have not been
well known. Because of the possible damage which these emissions can
produce in human respiratory systems, it is desirable to identify and
quantify them, with particular regard to asbestos. That is the purpose
of the program described in this report.
The amount of asbestos emitted is a function of many variables:
the number of vehicles on the road,
the number of miles driven per year by each,
vehicle size,
the number of vehicles using manual clutches,
conditions of driving (city, expressway, mountain;
driver habits, etc.),
brake system design, and
brake type (drum or disc),
rotor condition (surface roughness, scoring, cracking,
pitting, etc.),
rotor design (e.g., solid or ventilated discs, finned
drums, etc.),
rotor metallurgy (cast iron or aluminum),
volume percent of asbestos in the friction material, and
inherent wear resistance of the friction material.
In this program a passenger car of medium weight (test weight: 4800
pounds), produced in high volume, was used. It was equipped with a
manual transmission and clutch, ventilated cast iron disc brakes on the
front, and standard cast iron drum brakes on the rear.
A passenger car was selected for testing because of the following
factors:
(1) vehicle braking cannot be simulated realistically on
small-scale friction test-machines with the present
state of the art;
(2) full-scale brake and clutch dynamometers provide fairly
good simulation, and can be used for checking out the
emissions collection system; separate tests for brakes
and clutches would be required, however, thus increasing
program costs, whereas on the vehicle, disc and drum
brakes and clutches can be tested simultaneously;
(3) air flow in the dynamometers differs from that in vehicles,
and emissions from drum brakes will therefore be different
in the two cases.
1-2
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Three series of tests were run, using friction materials as tabulated
below:
Vehicle . Friction ,, ,
T . Simulation „ . . n Remarks
Test Materials
1 Original OEM1 Disc Front Class A organic disc pads
Equipment „„„ „
M y OEM Drum Rear
2 Partial AM2 Disc Front No metallic chips;
Used OEM Drum Discs and drums not
Rears turned
3 Full AM Disc Front Disc pads and secondaries
Reline AM Drum Rear contain brass chips
Discs and drums turned
This selection has several features. It provides a replication of one
test, thus giving an estimate of repeatability. It includes a primary/
secondary combination that serves both OEM and aftermarkets. It includes
one combination (two materials) of widely used OEM materials. It includes
one combination (two materials) from one of the larger aftermarket sup-
pliers. It includes a set of used linings (about 3,000 miles) to give
data on the emissions at various stages of lining life. It includes two
different disc pad materials from two of the larger aftermarket suppliers.
Five different manufacturers were represented in the friction material
selections.
The collection of particulate and gaseous emissions from any vehicle
friction couple has never before, to the authors' knowledge,been reported
in the literature. To define the extent of these emissions, a combination
separation and storage collection system was devised. Unique emissions
collectors for both disc and drum brakes, and for a clutch, were conceived,
designed, and built as the main embodiment of this instrumentation. The
collectors separated the wear debris into three different fractions: a
sump sample which included the wear debris on the lining surfaces, in the
rivet holes, and on the brake drum; a surfaces sample which included
the wear debris on the brake and collector shroud surfaces; and an airborne
sample collected on membrane filters.
The vehicle was equipped with standard brake test instrumentation.
A front disc brake collector and a rear drum brake collector were installed
on the right side of the vehicle. The clutch was sealed by closing the
•'•OEM - Original Equipment Manufacturers
2AM - aftermarket
1-3
-------
holes in its casing. The left wheel brakes were left in their normal
configuration and were used to monitor the operation of the shrouded
brakes. Wear debris was also taken from the left brakes; the amounts of
debris collected and its composition were used to demonstrate that the
brake shrouding did not significantly affect the operation of the brakes
within the emissions collectors.
Although there are many acceptable original equipment manufacturers
brake and friction material tests for measuring a specific collection or
combination of collections, no one test adequately matches driving con-
ditions which would be representative of all vehicles. Consequently, it
became necessary to devise a rational and meaningful vehicle test. A
total of seven schedules were chosen and each was followed by a measure-
ments procedure (take emissions samples, measure wear, inspect systems,
and replace worn parts). The first three schedules - Burnish, After
Burnish (A.B.) Baseline, and Detroit Traffic - Represented low-temperature
testing. The final four schedules - 10-Stop Fade, After Fade (A.F.) Base-
line, 15-Stop Fade, and Final Baseline - represented high-temperature and
abrusive testing.
The mileage accumulations for each schedule of each vehicle test
verified the possible test mileage reproducibility. A critical component
of the front disc brake collector was a unique rotating seal. For the
8100 miles of testing, only eight rotating seals were required — an ex-
ceptional improvement over the anticipated need at the start of the
program.
Prior to vehicle test 1, a Burnish schedule was performed and the
temperatures for the right front disc brake were found to be near 400°F.
The temperature difference, AT, between the right and left front brakes
ranged from 200 to 250°F. This was unacceptable. The addition of several
thermal control aids reduced the AT to a range of 115 to 160°F. Most import-
ant was the reduction of the right front brake operating temperature from
about 400°F to about 300°F. The brake shrouding did not present any pro-
blems on hot days. During the Detroit Traffic Test, the AT between the
front brakes remained between 100 and 140°F while that for the rear drum
brake remained between 10 and 30°F.
The range of asbestos content in the brake emissions for vehicle
tests 1 and 2 went from a high of 1.65 percent to a low of 0.03 percent
for the 90 analyses; only three were above 1.00 percent. The overall
average for vehicle test 1 was 0.40 percent and for vehicle test 2 was
0.25 percent. For vehicle test 3, the range of asbestos content was
from a high of 0.51 percent to a low of 0.003 percent. The overall aver-
age was 0.07 percent. In this work, all values for heavy-duty (abusive)
braking were less than one percent, which is significantly less than the
15 percent asbestos content reported by Lynch of the U.S. Public Health
Service.
To provide a systematic, independent check on the asbestos analyses,
the EPA Project Officer arranged a second contract for Battelle Columbus
Laboratories to analyze twenty-four samples generated by Bendix Research
1-4
-------
Laboratories. Johns-Manville also provided three analyses. The Johns-
Manville and Battelle data agreed very well. In 19 of the 24 analyses,
the Bendix results were slightly higher than the corresponding Battelle
results. The Bendix average was 0.25 percent, while the Battelle aver-
age was 0.17 percent, or 68 percent of the Bendix average. The Bendix
data were expected to be higher for the following reasons: all fibers
found were assumed to be cylinders of projected diameter and length, and
a fiber with an elliptical cross section was actually smaller in volume
than reported; and all fibers were assumed to be pure asbestos, (partially
degraded asbestos or olivine fibers were mechanically reduced to non-
fibrous material by the other analytical techniques, so only the stronger
asbestos fibrils that remained were counted).
Analysis of the gaseous emissions was made difficult by the large
quantities of water and carbon dioxide which by-passed the gas condition-
ing trap and entered through the rotating seals. Most samples showed
traces of C^ to 63 hydrocarbons only as lower concentrations of higher
molecular weight gases could not be detected. When the gases were con-
centrated from the fade tests, C^ to Cg compounds such as butanes, ben-
zene, toluene, phenol, and cresols were detected in the gas traps. The
corresponding shroud extracts showed C^2 to ^30 materials, including
cardanol.
To compare the generation of asbestos emissions properly, it was
found necessary to calculate the emissions factors for each sample in
micrograms/mile (yg/mile). These values were obtained by multiplying
the weight of generated brake debris by the appropriate asbestos percent,
followed by dividing by the miles per test schedule. Thus, either a
high asbestos content or a large sample gave a high factor.
The following observations were made:
• Asbestos emissions were higher for new friction surfaces
and decreased with use.
• Initially the drum brake produced more asbestos emissions than
the disc brake. The difference decreased as the materials
continued to be used.
• Heavy (abusive) duty did not necessarily give a higher percent
asbestos, however, the large amount of debris produced gave
a significant rise in asbestos emissions.
• The order of decreasing asbestos emissions from brakes was
found to be:
Fade or heavy-duty stops . ^
1 Decreased
Burnish | asbestos
Moderate braking
J
1-5
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For the disc pads only, there was an increase in asbestos
emissions with increased asbestos content in the friction
material (there was no such trend for the drum brake
materials) .
Both the front disc pads and the drum linings of vehicle
test 3 had wear comparable to that of the other two vehicle
tests, yet the asbestos emissions were significantly lower.
Both pads and linings contained brass chips which may have
been in part responsible for the more complete conversion
of the asbestos in the brake emissions, possibly because
of better heat transfer to the asbestos.
For both disc and drum brakes, the surfaces sample was
the largest of the three (^92 percent), the sump sample
was next ('W percent) , and the airborne sample was the
smallest (^1 percent).
Two series of weighting factors were developed. The distribution
weighting factors were calculated from the material recoveries in the
shrouded and unshrouded brakes as indicated earlier. Estimates were made
for both disc and drum brakes from the test vehicle for the amounts of
the different samples distributed from the brakes. These estimates were
made for the Burnish schedule, for the end of a complete vehicle test,
and for the end of all three vehicle tests. For the drum brake, estimates
were made up to 40,000 miles. The severity weighting factors were cal-
culated from the percentages of different braking modes: for new versus
burnished friction materials, for severe (or abusive) versus moderate
braking, and for the renewal of friction surfaces (A.F. Baseline).
The total asbestos emissions estimate for the test vehicle was
calculated from the asbestos emissions factors and the severity weighting
factors. The average asbestos emissions factor for the disc brakes, drum
brakes, and clutch were used along with the Burnish (new surfaces), A. B.
Baseline (surface preparation) , Detroit Traffic (moderate braking) , 10-
Stop Fade (severe braking) and A. F. Baseline (surface renewal) weighting
factors. The value obtained for the test vehicle was 28.51 yg/mile.
The fate of the asbestos emissions was calculated with the use of
the distribution weighting factors as follows:
Road Drop-out 81.9%
Airborne: 3.7%
Brake Retention: 14.4%
The annual total asbestos emissions estimate for 96,400,000 pass-
enger vehicles travelling an average of 9,978 miles per year was found
to be 60,400 pounds, distributed as follows:
Road Drop-out: 49,470 Ibs
Airborne: 2,230 Ibs
Brake Retention: 8,700 Ibs
60,400 Ibs
1-6
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The annual total asbestos emissions estimates for light trucks,
medium trucks (and buses), and heavy trucks were found to be:
Light trucks
Medium trucks
(and buses)
Heavy trucks
32,300 Ibs
16,300 Ibs
22,900
81,500 Ibs
The distribution of the total asbestos emissions estimate for trucks was
calculated to be as follows:
Road Drop-Out: 87.9%
Airborne: 2.9%
Brake Retention: 9.2%
The estimated asbestos emissions for all vehicles in pounds/year
is summarized as follows:
Total Asbestos
Emissions (Ibs)
Distribution (Ibs)
Drop-Out Airborne Retention
Passenger Cars
Light Trucks
Medium Trucks (and
buses)
Heavy Trucks
Miscellaneous
(motorcycles,
trailers, etc.)
Distribution by
percent:
60,400
32,300
16,300
32,900
16,300
158,200
49,470
28,420
14,330
28,920
14,330
135,470
2,230
940
470
950
470
5,060
8,700
2,940
1,500
3,030
1,500
17,670
85.6%
3.2%
11.2%
These estimates are considered to be maximum values.
1-7
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SECTION 2
OBJECTIVES AND BACKGROUND
2.1 OBJECTIVES
2.1.1 Objectives of this Program
The objectives of this program, as stated in the Request
for Proposal and in the Contract, were as follows:
"In order to define the extent of non-engine asbestos
emissions, the Office of Air Programs of the Environmental
Protection Agency is seeking the assessment of these emis-
sions on a single vehicle basis. The efforts are to include
emissions measurements from several different types of brakes
as well as a clutch assembly. The end objective of the work
will be the documentation of these emissions to assess their
overall contribution to the atmosphere."
2.1.2 Bendix Technical Approach
2.1.2.1 Select Suitable Vehicle and Friction Materials
For the results to be representative of the average
consumer-type vehicle usage, it was necessary to select a vehicle inter-
mediate between the compacts and luxury vehicles. Moreoever, it was
desirable to select a vehicle with original-equipment friction materials,
produced by more than one supplier, and equipped with a clutch. After-
market friction materials, produced by several manufacturers, were also
selected.
2.1.2.2 Conceive, Design, and Build Brake and Clutch
Emissions Collectors
Since only 100-percent collection could give a mass
balance, it was necessary to conceive, design, and build brake and clutch
emissions collectors which could collect all the emissions and differen-
tiate among wear debris remaining on the friction materials, debris re-
maining on the local surfaces of the foundation brakes, and debris entering
the atmosphere. Moreoever, provision was necessary for the collection and
storage of gaseous decomposition products.
2.1.2.3 Test a Typical Collector and Instrument the Vehicle
To ensure that the concepts and hardware were technically
sound, it was necessary to install the most critical collector on an
inertial dynamometer to verify its operation. Once proven, that collector
and the others, along with brake test instrumentation, could be installed
on the vehicle.
2-1
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2.1.2.4 Select and Run Suitable Driving Test Schedules
Because of the wide variety of driving which takes place
throughout the various regions of the country, it was necessary to select
a vehicle test program in which brake emissions could be collected for
new brake linings and rotor combinations. The program included typical
consumer-type driving on flat terrain, and heavier-duty braking as en-
countered in hilly areas.
2.1.2.5 Collect and Analyze Emissions
As the main goals were to determine the asbestos content
of the emissions and their particle-size distributions, it was necessary
to select an analytical method which would not disturb the particle size
distribution and yet be sensitive to very small amounts of asbestos.
Further, it was necessary to collect and separate very low concentra-
tions of gaseous emissions from extremely large quantities of air and
other molecules present in large concentrations.
2.1.2.6 Estimate Asbestos Emissions for Cars and Trucks
Because of funding and time limitations, only a few
selected tests could be run. Based on the measurements taken and a
knowledge of the overall vehicle population, it was possible to prepare
estimates for total emissions from cars and trucks operating in the
United States.
2.2 PRIOR WORK
2.2.1 Published Data
The only known published data on asbestos emissions were
those reported by Jermiah Lynch of the U.S. Public Health Service,
Department of Health, Education, and Welfare.(2-1)*
The paper discusses tests which were performed with brake
test machines, using one-inch-square samples, and tests performed on an
inertial dynamometer where a complete brake and clutch were used. Emis-
sions samples were collected on membrane filters and analyzed by electron
microscopy. In all but a few tests, the drum brake linings showed less
than 1 percent free fiber in the decomposition product. In some tests
reported, where the lining temperatures were extremely high and accompanied
by a rapid drop in coefficient of friction (fade), a significant mass of
free fiber was released - approximately 10 to 15 percent. The clutch
test gave no asbestos fiber.
*
Numbers in parentheses designate References at end of section.
2-2
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2.2.2 Unpublished Data
At the time of writing of this report, there were three
known works which had been completed or were in progress. The amount
of brake wear debris and its composition were determined on a full-brake
inertial dynamometer using a duo-servo drum brake in 1968-69.'^ ' The
determination of the amount of asbestos in airborne brake debris sampled
downwind of a disc brake installed on an inertial dynamometer was in
progress.(2~3) The determination of asbestos content in airborne brake
debris sampled downwind of vehicle-mounted disc and drum brakes was also
in progress.(2-4)
2.3 BACKGROUND
2.3.1 Energy Absorption by Friction Materials
2.3.1.1 Brakes
During a stop, the automobile brake converts the kinetic
energy of the moving vehicle into heat, absorbs the heat, and gradually
dissipates it to the atmosphere. The sliding friction couple in the
brake consists of a cast-iron rotor (drum or disc) and a stator on which
is mounted a friction material or lining consisting of asbestos fiber,
property modifiers, and an organic resin binder. Lining is considered
expendable. Over a long period of time and many miles of service, much
of it is converted to dust and gases. Smaller amounts of the rotor are
also converted to wear debris. Particulate debris is partially retained
and partially emitted from the vehicle in normal service.
2.3.1.2 Clutches
The "manual" automobile clutch transfers the kinetic
energy of the engines rotating crankshaft smoothly to the transmission
and wheels. Any slippage results in generation of heat, which is ab-
sorbed and eventually dissipated to the atmosphere by the clutch. Thus
the clutch is basically a dry-running static friction couple (which
slides momentarily during gear shifts). The mating materials are usually
cast-iron or steel and a friction material or lining which is frequently
organic-bound. Organic-bound friction materials consist of asbestos
fiber reinforcement, property modifiers, and an organic resin binder.
The composition is qualitatively similar to that of brake linings.
Clutch linings are also expendable, gradually wearing away in use. The
wear debris can escape from manual clutches. Wear debris from friction
materials in automatic transmissions is retained almost completely in
the transmission fluid.
2-3
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2.3.2 Compositions of Friction Materials
2.3.2.1 Generalized Classifications
Table 2-1 gives typical compositions of drum lining, disc
pad,(2~5) and clutch facing friction materials. The foundation, or major
constituent, of practically all organic friction materials is asbestos
fiber. Asbestos is chosen because of its thermal stability, its relatively
high friction level, and its reinforcing properties. Since asbestos alone
does not offer all of the desired friction properties, other materials
called friction modifiers are added. Modifiers are varied in type and
content to provide desired levels of effectiveness, wear, fade, recovery,
and noise. A resin binder is also added to hold the other materials
together with adequate strength.
2.3.2.2 Asbestos
The asbestos usually used in friction materials is chry-
sotile from Quebec or Vermont. Chrysotile, the principal mineral of the
serpentine group, has the approximate composition formula
or 3Mg0.2Si02-2H20
Table 2-1 - Composition of Typical Automotive Friction Materials
(Volume Percent)
Resin Binder
Asbestos Reinforcement
Friction Modifiers
• Organic
Friction Dust
Elastomer
• Inorganic
Garb ons /Graphites
Zinc Chips
Oxides
Copper/Brass
Misc. Inorganics
Sulfur
Drum Linings
Primary
20-30
Major
10-15
Secondary
25-35
Major
5-15
5-15
0-5
0-5
5-10
Disc Pads
Class A
Standard
18-22
Major
20-25
10-15
1-2
1-2
0-5
Class B
Heavy-Duty
15-18
Major
0-15
0-10
2-15
2-7
5-10
5-15
Woven Clutch Facings
Standard
20-30
Major
0-5
0-5
5-10
2-5
Heavy-Duty
15-25
Major
0-5
5-10
5-10
2-5
2-4
-------
Structurally, it is a pseudohexagonal network of Si04 tetrahedra forming
a sheet in which all the tetrahedra point one way. A layer of brucite,
Mg(OH)2, is joined to the 8104 network in such a way that, on one side,
two out of every three hydroxyls are replaced by oxygens at the apices
of the tetrahedra (Figure 2-1). The macromolecule consists of parallel
sheets of brucite-silica layers structured in cylindrical lattices in-
volving closed concentric cylinders, spirals, and sometimes helical
arrangements.(2-6)
Bendix Research Laboratories' scientists have been study-
ing asbestos for several years. Figure 2-2 presents the results of dif-
ferential thermal analysis (DTA) and thermogravimetric analysis (TGA)
studies for a common short-fiber grade of chrysotile asbestos.(2-7) The
transition at approximately 700°F (370°C), in both the DTA and the TGA
thermograms represents the dehydration of the brucite (magnesium hydrox-
ide) , the 1.4 percent weight loss corresponding to an approximate con-
centration of 4.5 percent brucite. The transition at 1250°F (680°C) in
both thermograms represents the major dehydroxylation reaction in chrys-
otile asbestos. At 1580°F (860°C), a sharp exotherm, not associated with
any weight change, represents the conversion of the dehydroxylated chrys-
otile to forsterite (2MgO'Si02) or olivine [2(Mgl.oO-xFex)0
-------
H H
H HYDROGEN
• OXYGEN
O MAGNESIUM
0 SILICON
SHEETS ARE CONTINUOUS IN DIRECTION OF CURVATURE AND NORMAL
TO PLANE OF SECTION; FIBER AXIS IS ALSO NORMAL TO PLANE OF SECTION.
Figure 2-1 - Schematic Structure of Chrysotile Asbestos
I
- O.S°C/IN.
:T
,1.0% MOISTURE
1.4% LOSS
20°C/MIN
1 | I
' I I
I I
11.5% LOSS
100 200 300 400 BOO 600 700 800 900 1000 °C
200 400 600 800 1000 1200 1400 1600 1800 °F
TEMPERATURE
Figure 2-2 - DTA and TGA Thermograms for Chrysotile Asbestos
(Bendix Data)
2-6
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CHRYSOTILE
104 96 88 80 72 64 56 48 40 32 24 16
26 ANGLE (DEGREES)
104 96 88 80 72 64 56 48 40 32 24 16
FORSTERITE
Figure 2-3 - X-Ray Diffraction Pattern of Heated Chrysotile Asbestos
(Bendix Data)
2-7
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2.3.2.4.1 Non-Abrasive Modifiers
Nonabrasive friction modifiers can be classified further
as low friction and high friction. The most common and best known of the
high-friction materials is known as friction dust. This is a cured resi-
nous material. The most frequently used variety is derived from cured
or polymerized cashew-nut-shell liquid, chemically a phenolic compound.
When heated with hardening agents, such as hexamethylenetetramine or
formaldehyde, it becomes sufficiently hard or polymerized to be granu-
lated. Many other cured resinous or polymeric materials, some with
fillers, are also used. Certain friction dusts are combinations of these
materials and cashew resin. Ground rubber is normally used in particle
sizes similar to, or slightly coarser than, those of the cashew friction
dusts for noise, wear, and abrasion control.
Carbon black, graphite, petroleum coke flour, or other
carbonaceous materials may also be added as friction modifiers to lower
the friction coefficient or to reduce noise. These materials are normally
used in the form of fine powders or particles, although graphite is some-
times used in coarse particles or pellets. The amount of friction modi-
fier added is dependent upon the properties desired in the final composite.
2.3.2.4.2 Abrasive Modifiers
Abrasive modifiers, such as alumina and the silicas, are
usually used in relatively small amounts and only in very fine particle
sizes (generally 100 mesh or finer). Particle size is limited by the
fact that large particles of such hard materials would groove and wear
the mating surfaces. Minerals are generally added to improve wear resis-
tance at minimum cost. Those most commonly used are ground limestone
(whiting) and barytes (barium sulphate), though various types of clay,
finely divided silicas, and other inexpensive or abundant inorganic
powders may also perform this function. Such materials are inorganic
in nature and tend to detract from noise properties and mating surface
comp at ib ili ty.
Metals or metal oxides may also be added to perform spe-
cific functions. Brass chips are frequently found in heavy-duty friction
materials where, as scavengers, they break up undesirable surface films.
Zinc and aluminum are also used. Zinc chips, in relatively small amounts,
can contribute significantly to recovery of normal performance following
fade.
2.3.3 Friction Material Reactions
2.3.3.1 Absorption and Conversion of Energy
The automobile brake converts the kinetic energy of the
moving vehicle into heat, absorbs the heat, and eventually dissipates
it to the atmosphere. The clutch absorbs the friction energy generated
when the transmission and drive-shaft are engaged or disengaged on manual
2-8
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transmission vehicles. Phenolic-bound brake lining compositions contain-
ing asbestos serve as one of the best classes of low-cost expendable
members of the friction couple for all-around performance. At low energy
absorption rates, the temperature of the friction material, approximately
40 mils from the interface, may rise to 300°F; the interface itself is
hotter. Most of the heat is removed from the interface by convection
and conduction.(2-10) At high energy absorption rates, heat is generated
faster than it can be dissipated and the temperature at the sliding inter-
face reaches a point where chemical reactions occur rapidly. Surface
temperatures up to 1600°F have been observed or calculated; the presence
of olivine in the wear debris confirms that such temperatures have been
reached.
2.3.3.2 Physical and Chemical Changes in Linings During Use
Figure 2-4 illustrates the heterogenous nature of a
typical friction material composed of the following ingredients: phenolic
binder (30 volume percent), asbestos fiber (55 volume percent), and cashew
friction modifier (15 volume percent).
As a result of the energy conversion at the stator-rotor
interface, the composition of the brake lining surface is altered. At
low service temperatures, the phenolic resin and organic friction modi-
fier convert, on the surface, to compositions with slightly higher carbon/
oxygen ratios. At somewhat higher use temperatures, the resin and or-
ganic friction modifier convert to carbon more readily, and this in turn
oxidizes to carbon dioxide. At the same time, the asbestos wears away
more rapidly because of the reduced binder strength and volume at the
surface. Figure 2-5 is a photomicrograph of typical wear debris collected
from Bendix Research Laboratories' dynamometer, operated at 600°F. Asbestos
fibers are prevalent in several of the wear debris particles. Figure 2-6
is a photograph of the improved wear debris collector designed and built
for friction and wear research.(2-11) At still higher temperatures, the
asbestos converts from its fibrous form to an olivine powder with little
or no reinforcing value. Figure 2-7 shows the frictional-heat-affected
layer of lining which had experienced more than 10 successive stops from
100 mph without sufficient cooling between stops.(2-12) (A large piece
of material is about to separate from this sliding interface - an example
of macroshear wear, described later.)
When heat is generated at the sliding interface between
stator and rotor much faster than it can be dis-sipated, the temperature
rises and may reach a point where the lining or pad components decompose,
oxidize, or melt. The stator material then wears rapidly and the fric-
tion coefficient, y, may decrease. This is fade. Fade has been attri-
buted by some to evolution of gas at the sliding interface; on heating,
the gas expands and exerts a force on the lining or pad, tending to
push it away from the rotor. (2~ 13) pa
-------
< Jfr*
*•,« n5 *•
i
«• ^VlHt
ci iniMr; Jfc* .-^3r i?4
Sf'" ?V';
HEAT-AFFECTED LAYER
i
FRICTION MODIFIER
Figure 2-4 - Photomicrograph of Brake Lining Cross Section After
8550 Miles of Test-Track Service
x 9,250
Figure 2-5 - Electron Micrograph of Friction Material Wear Debris
(Made during 1966 studies) - 10,000 X
2-10
-------
Figure 2-6 -
Close-up View of Bendix Drag Dynamometer Showing
Wear Debris Collector
Sliding
Surface
Heat-
Affected
Zone
Unchanged
Material
Figure 2-7 - Photomicrograph of Cross Section of Friction Material
Test Specimen After More Than 10 Successive Stops from
100 mph on Bendix Full-Brake Dynamometer
2-11
-------
ho
PHYSICAL OR CHEMICAL CHANGE
CAST IRON MELTS
CaC03 (CALCITE) DECOMPOSES
CaC03 (ARAGONITE) DECOMPOSES
ASBESTOS PRODUCTS TRANSFORM
TO OLIVINE
ASBESTOS LOSES MORE WATER
IRON POWDER AND FIBERS
BEGIN OXIDIZING
GRAPHITE BEGINS OXIDIZING
ZINC MELTS
PHENOLIC RESINS CHAR
PHENOLIC RESINS OXIDIZE
AMORPHOUS CARBON BEGINS
OXIDIZING
ASBESTOS LOSES WATER
FRICTION DUSTS AND RUBBER CHAR
BRASS BEGINS OXIDIZING
ZINC BEGINS RAPID OXIDIZING
FRICTION DUSTS AND RUBBER
OXIDIZE
TEMPERATURE
op oc
2105 1150
787 419
700 372
500 260 '
>440 >225
*-"/MO ^225
395 200 —
1200- 1
1
»-
800
^
400-
ft
—
PHYSICAL OR CHEMICAL CHANGE
1200-
CASTIRONMELTS
PEARLITE BEGINS TRANSFORMING -
TO MARTENSITE
SEVERE SCALING BEGINS-
GRAPHITE BEGINS -
SPHEROIDIZING
VISIBLE, ADHERENT SURFACE •
OXIDE FORMS
400-
200-
-2000
-1600
-1200
-800
-400
°C
°c
Figure 2-8 - Changes Occurring in the
Friction Material as the
Temperature Rises
Figure 2-9 - Changes Occurring in the
Rotor as the Temperature
Rises
-------
summarizes the physical and chemical changes which take place in the
friction material as the temperature rises.(2-14) Figure 2-9 summarizes
the physical and chemical changes which take place in the cast-iron rotor
as the temperature rises.
2.3.4 Brake Lining Wear Mechanisms and Generation of Emissions
2.3.4.1 Types of Wear Mechanisms
Emissions are generated by wear. To the consumer, wear
is an economic consideration. To the environmentalist, these emissions
are substances to be characterized and, if harmful, to be eliminated.
From the basic friction material engineering standpoint,
wear resistance is inversely related to friction level and other desir-
able performance characteristics. Linings with faster wear rate and
more frequent surface renewal generally have greater frictional sta-
bility. --This circumstance is used to advantage in the development of
primary-type linings for duo-servo brakes, where, because of design,
the stability of frictional properties is of greater significance to
brake performance than is wear resistance; use of primary linings with
too much wear resistance results in poor fade resistance, less fric-
tional stability, and generally poor overall performance.
Except in the case of primary linings, however, one of
the formulator's objectives must be to achieve the highest possible
level of wear resistance. Contrary to the opinion of some, maximum
life does not require a friction material of maximum physical hardness.
What is desirable is a minimum wear rate in normal low-temperature use,
a moderately increased rate at elevated temperatures, and a return to
the original low-temperature wear rates after being subjected to ele-
vated temperatures.
Total emissions generation may be defined as the sum total
of the losses associated with five basic types of wear.(2-15)
• abrasive wear,
• thermal wear,
• adhesive wear,
• fatigue wear, and
• macroshear wear
As shown in Table 2-2, there are several possible mechanisms for each
type of wear.
2.3.4.1.1 Thermal Wear
Thermal wear encompasses a group of physical and chemi-
cal reactions in the course of which interatomic bonds are broken by ther-
mal energy. These reactions include pyrolysis (thermal decomposition),
2-13
-------
Table 2-2 - Wear Mechanisms in Friction Materials
THERMAL WEAR
PYROLYSIS
OXIDATION
THERMOPARTICULATION
MELTING
EVAPORATION
SUBLIMATION
EXPLOSION
ABRASIVE WEAR
TWO-BODY
ASPERITIES
SCORING
CRACK EDGES
PIT EDGES
THREE-BODY
WEAR DEBRIS
ROAD DUST
ADHESIVE WEAR
ORGANIC MATERIAL ADHESION
BINDER
FRICTION DUST
RUBBER
INORGANIC MATERIAL ADHESION
METAL PARTICLES
ICE
FATIGUE WEAR
THERMAL
CYCLING
SHOCK
MECHANICAL
REPEATED BRAKING
DRUMS OUT OF ROUND
DISCS OUT OF PARALLEL
MACRO-SHEAR WEAR
ACROSS THE PAD
AT CORNERS AND EDGES
THROUGH HEAT-AFFECTED LAYERS
oxidation, thermoparticulation, explosion, melting, evaporation, and
sublimation. Their rates increase exponentially with temperature, and
in extreme cases they result in fade.
Pyrolysis probably occurs predominantly at the centers
of linings and pads and to a lesser extent at the corners and edges.
Oxidation, on the other hand, probably predominates at the corners and
edges and is less severe at the center. Explosive reactions occur
under highly abusive braking conditions, where the rate of heat input
is so high that solids are converted to gases well beneath the surface;
because these gases are greater in volume than the solids they displace,
they create a pressure that ruptures the lining in an explosive manner.
Four such reactions are represented in Figure 2-10.
It might be thought that rapid thermal wear occurs only
at high soak temperatures.* In fact, however, thermal wear probably
Soak temperatures are temperatures measured during dynamometer or vehicle
testing, using a thermocouple located in the friction material or in the
rotor, generally at a distance of 20 to 50 mils from the sliding interface
2-14
-------
FRICTION
< MATERIAL
SURFACE
FRICTIOIMAL HEAT
V FRICTION MATERIAL
(T) CaCO3 (s) -»-CaO (s) + CO2 (g) *
@ CASHEW DUST (s) -»CO2 (g) + H2O (g) + C (s)
(3) ASBESTOS-*H2O (g) + OLIVINE (s) + ASBESTOS FIBRILS (s)
(?) PHENOLIC RESIN ^CO2 (g) + H2O (g) + C (s)
(S): SOLID
(G): GAS
*THE BRASS CHIP CONDUCTS HEAT RAPIDLY INTO
THE FRICTION-MATERIAL SURFACE.
Figure 2-10 - Mechanism of Explosive Thermal Wear
occurs at appreciable rates at low soak temperatures as well. It has
been shown that the materials in a sliding friction couple contact each
other at the tops of asperities on their surfaces. There is consider-
able evidence to indicate that the temperature increase at these asperi-
f 9 1 fi 7 I "
ties for low sliding speeds is represented by the equation^ » *-~-
T -
(gyvw/4aJ)[l/(k
where
T is the "flash" temperature
T is the soak temperature
g is the acceleration due to gravity
y is the coefficient of friction
v is the sliding velocity
w is the load on the asperity
2-15
-------
a is the radius of the asperity junction
J is the mechanical equivalent of heat
k.. is the thermal conductivity of the disc
k is the thermal conductivity of the slider
Modifications of this equation have also been developed for high sliding
speeds. Experiments indicate that the flash temperature may be as high
as 1400°F (760°C) if the soak temperature is 650°F (343aC). This flash
temperature is high enough to cause rapid localized pyrolysis of the
organic compounds used in friction materials, as well as conversion of
fibrous asbestos to powdery olivine and transformation of pearlite to
martensite in the cast-iron mating surface.
2.3.4.1.2 Abrasive Wear
Abrasive wear is of two types: two-body wear (Fig-
ure 2-11) and three-body wear (Figure 2-12). Plowing by asperities on
the rotor surface and plowing by edges in rough-machined, scored, cracked,
or corroded (pitted) rotors are examples of two-body wear. Grinding by
wear debris and by foreign particles such as sand, clay, mud, or salt
in the sliding interface is three-body wear.
Abrasive wear would be expected to increase with tem-
perature. It increases also with the braking load and with the concen-
tration, size, and hardness of foreign particles. It may be accompanied
by negative fade.
Figure 2-13 is a Bendix scanning electron photomicro-
graph of a dynamometer-tested friction material showing the abrasive wear
tracks on the surface. Several adherent wear debris particles are
similar in size to the wear track widths.
2.3.4.1.3 Adhesive Wear
Adhesive wear, illustrated in Figure 2-14, involves the
adhesion of organic and/or inorganic materials to the rotor and the sub-
sequent tearing or separation of these materials from the lining or pad.
Organic constituents of friction materials include the
binder, friction modifiers and elastomeric compounds. Inorganic consti-
tuents include zinc powder, brass chips, and asbestos. Little is known
about the tendency of these materials to adhere to the cast iron used
in today's drums and discs, though experience with hot elastomeric com-
pounds suggests that elastomers are very likely to stick. Experiments
at Bendix Research Laboratories indicate that brass chips will alloy
with certain nonferrous rotor alloys.(2-18) men thig occurs^ metal
is transferred from the rotor to the lining, scoring the surface of the
rotor and in turn subjecting the lining to a high rate of two-body abra-
sive wear.
2-16
-------
DIRECTION OF RELATIVE MOTION
A DIRECTION OF
NORMAL
FORCE
ASPERITIES INTERACTING
TO FORM WEAR DEBRIS
FRICTION MATERIAL
ROTOR
WEAR
DEBRIS
Figure 2-11 - Mechanism of Two-Body Abrasive Wear
DIRECTION OF RELATIVE MOTION
DIRECTION OF
NORMAL
FORCE
ROTOR
WEAR
DEBRIS
Figure 2-12 - Mechanism of Three-Body Abrasive Wear
2-17
-------
Figure 2-13 - Scanning Electron Photomicrograph Showing Abrasive Wear
Tracks on Friction Material Surface and Adherent Wear Debris Particles
DIRECTION OF RELATIVE MOTION
\ POINT OF ADHESION
ERECTION OF
NORMAL
FORCE
FRICTION MATERIAL
Figure 2-14 - Mechanism of Adhesive Wear
2-18
-------
Adhesive wear probably increases with temperature,
braking load, and the concentration of adherent components in the friction
material. It is also caused by the presence in the friction material
of metal particles capable of solution in or reaction with the rotor
alloy, increasing with the size and concentration of such particles.
Because this type of wear can cause stick-slip, it may be associated
with brake noise.
2.3.4.1.4 Fatigue Wear
Fatigue wear (Figure 2-15) is most commonly observed
in metal bearings. However, it may also be experienced by organic fric-
tion materials, occurring in two forms, thermal and mechanical.
Thermal fatigue is caused by repeated heating and
cooling. Such repeated temperature changes impose cyclic stresses on
the surface material, which heats and cools more rapidly than the bulk
material and thus expands and contracts to a greater extent. Because
of their low thermal conductivities, the thermal gradients and resultant
thermal stresses in organic friction materials may be higher than those
in metals.
Thermal-shock cracking may be thought of as a special
case of thermal fatigue, occurring as a result of a single abusive
loading.
Mechanical fatigue is caused by repeated mechanical
stressing. Because of the frequency of brake use, friction materials
are subjected repeatedly to both compression and shear forces. Addi-
tional stresses are also applied repeatedly if drums are out-of-round,
if discs are out-of-parallel, or if rotor thickness is not uniform.
Figure 2-13 shows the initiation of fatigue wear around
the large cashew particle. This material swells when heated and thus
the surface wears. After cooling, the particle contracts, cracks, and
pulls away from the edges. When the particle is completely loose, it
can fall out.
2.3.4.1.5 Macroshear Wear
Three types of material removal fall in the category of
macroshear wear, which is illustrated in Figure 2-16.
A fracture, in shear, may occur across the entire brake
pad under extremely heavy loading, especially if the friction material has
previously been weakened by heat. This is a sudden rather than a gradual
type of wear.
Fracture at the edges and corners of a piece of friction
material is another type of macroshear wear. Oxidation of organic com-
ponents weakens the friction material at these locations.
2-19
-------
FRICTION MATERIAL
Figure 2-15 - Mechanism of Fatigue Wear
GENERALIZED
FAILURE THROUGH
HEAT-AFFECTED
ZONE
DIRECTION OF RELATIVE MOTION
DIRECTION OF\
NORMAL
\
\
LOCALIZED
FAILURE AT EDGE
WEAKENED BY
OXIDATION
Figure 2-16 - Mechanism of Macroshear Wear
2-20
-------
Fracture at the edges and corners of a piece of fric-
tion material is another type of macroshear wear. Oxidation of organic
components weakens the friction material at these locations.
A third type of macroshear wear can occur when a fric-
tion material such as that shown in Figure 2-15 is subjected to heavy
loading following thermal abuse. The heat-affected layer in the material
pictured is about 100 mils deep, and from this layer organic material
has been removed by pyrolysis. If sufficiently weakened, such a layer
can be sheared away by a single, heavy brake application.
Whatever the mechanism, macroshear wear is promoted by
nonuniform loading and by oxidation and thermal degradation of the
binder. It is most likely to occur at elevated temperatures and under
severe braking conditions. Its end products are typically large frag-
ments of friction material that leave the surface rough. These frag-
ments subject the remaining friction material to plowing or abrasive
wear, and while they are present in the interface, friction behaviour
will be erratic.
2.3.4.2 Predominant Wear Mechanisms
The predominant wear or emissions-generation mechanisms
may be summarized simply (Figure 2-17):(2-19)
• Below 450°F:
Abrasive and adhesive wear.
• Above 450°F:
Thermal wear.
Figure 2-18 illustrates the wear loss of three different kinds of fric-
tion materials as a function of temperature, illustrating these predomi-
nant wear mechanisms.
2.3.4.3 Wear Equation
Recent work at Bendix Research Laboratories has indicated
that each friction material wears according to a universal wear equa-
tion.(2-20)
AW = k • pa • Vb • tC
or
log (AW) = log k + a log P + b log V + c log t
2-21
-------
0.09
0.08-
0.06
II
0.05-
0.04-
0.03
/A
/P
THERMAL WEAR
- PREDOMINATES
BRASIVE WEAR
PREDOMINATES
300 400
ISOTHERMAL TEMPERATURE
600 °F
Figure 2-17 - Predominant Wear Mechanisms of Friction Materials
100
200
300 400 500
ISOTHERMAL TEST TEMPERATURE (°F)
600
Figure 2-18 - Variation of Friction Material Wear with Temperature
2-22
-------
where
AW is the weight lost
k is the wear factor
p is the load
V is the sliding velocity
t is the time of sliding, and
a,b,c are constants characteristic of a given friction couple.
When further developed, this equation will be useful for
predicting wear (and emissions) under various driving conditions.
2.3.5 Emissions of Particulate and Gaseous Emissions
2.3.5.1 Drum Brakes
Gaseous decomposition products in drum brakes are emitted
from two areas:
• The space between the rotating drum and the stationary
backing plate.
• The small holes in the backing plate itself (e.g.,
clearance holes, brake adjusting slot, etc.)
Particulates are emitted from the same two areas, although
only small particulates would come through the holes in the backing plate.
In drum brakes, some particles are not emitted but remain in the rotating
drum. It is expected that some of these particles would eventually be
emitted through the space between the rotating drum and stationary back-
ing plate. Also, some large particles would be "ground up" and emitted
as a number of smaller particles if they are trapped between the friction
material and drum on subsequent braking or if they are trapped between
the rotating drum and stationary backing plate. If the brake shoes are
of riveted construction, then some particles can be trapped in the rivet
holes and thus retained in the brake.
If convective cooling of drum brakes is improved in the
future, as is desirable for safer operation and longer driving life, it
is likely that fewer particles will remain trapped. The particles
emitted, however, will probably be larger, as they will be subjected
to grinding action for shorter periods of time.
2.3.5.2 Disc Brakes
As the disc brake is essentially an open braking system,
it is expected that all particulate and gaseous decomposition products
2-23
-------
will be emitted. However, a small amount of particulates collect in the
rivet holes of riveted disc brake pads and on some areas of the caliper.
2.3.5.3 Clutches
In the dry clutches commonly in use on "stick-shift" cars,
there are very few openings for gases and particles to escape. The two
main areas are:
• The area around the clutch fork, which generally has a
rubber boot on it for protection of the clutch from
road spray, sand, etc.
• A small opening at the lower front of the clutch to
drain any oil, water, etc., which may get into the
clutch.
Because of the construction, many particulates remain in the clutch
housing.
2.3.6 Distribution and Changes in Brake and Clutch Emissions
Entrapped gases and pyrolysis gases released during braking
or clutch slipping will be hot enough to mix rapidly with the surrounding
air and become part of the air wake of the car. The higher molecular
weight vapors will condense and eventually settle to the ground. The low
molecular weight gases will disperse as part of the local atmosphere.
Some of the condensible vapors may, of course, settle on small, air-borne
dust particles and could be carried into the respiratory system as part
of the breathing air.
The particle emissions will disperse in different ways depend-
ing on their size, shape, and density. Submicrometer-size particles, re-
gardless of shape, will ordinarily remain air-borne until they are
scrubbed out by rainfall or some other separating action. In effect they
become a long-time part of the atmosphere.
Spherical particles in the 1.0 ym to 10 ym diameter range
will settle, under gravity and in still air, at velocities from 12 to
1000 cm/hr, according to Stokes1 law. Irregularly shaped particles of
similar size and in turbulent air will settle at much slower velocities
and could remain air-borne for hours or days. These particles cause the
greatest aggravation in the human respiratory system because they collect
in the tracheo-bronchial regions and, to some extent, in the alveoli.
Particles from 20 ym to 100 ym in diameter will settle as
part of the dust trail left by the car or will collect with any larger
particles in mechanical traps in the car. Eventually these larger-size
particles will fall or be shaken out of the car and become part of the
road dust.
2-24
-------
2.4 REFERENCES
(2-1) J. Lynch, "Brake Lining Decomposition Products," J. Air
Poll. Control Assoc., 18_, No. 12, 824 (1968).
(2-2) S. Spiel, Johns-Mansville Research and Engineering, private
communication, 1971
(2-3) Private Communication, 1972.
(2-4) J. Moran, Environmental Protection Agency, private communica-
tion, 1972.
(2-5) B. W. Klein, "Semi-Metallic Outer Pads for Disc Brakes,
"Bendix Technical Journal", _2, (No. 3), 109-113 (Autumn 1969).
(2-6) A. A. Hodgson, "Fibrous Silicates, "Lecture Series No. 4,
Royal Institute of Chemistry, London, England, 1965.
(2-7) M. G. Jacko, W. M. Spurgeon, R. M. Rusnak, and S. B. Catalano,
"Thermal Stability and Fade Characteristics of Friction
Materials," _SAE Transactions, 77, 1474 (1969).
(2-8) 11. G. Jacko, "Thermal Analysis of Friction Materials,"
presented at the National Meeting of The American Chemical
Society, San Francisco, Calif., April 1968; also S. Porter
(ed.), Analytical Colorimetry, Plenum Press, N.Y., 1968.
(2-9) F. W. Aldrich and M. G. Jacko, "Organic Friction Materials,"
Bendix Technical Journal, (No. 1), 42-54 (Spring 1969.)
(2-10) R. M. Rusnak, H. W. Schwartz, and W. P. Coleman, " A Com-
parison by Thermal Analysis of R.otor Alloys for Automobile
Disc Brakes," SAE Paper 700137, January 1970.
(2-11) A. R. Spencer, W. 11. Spurgeon, and J. L. Winge, "Four Tests
for Consistency of Automotive Brake Linings," SAE Paper
660412, presented at the Mid-year Meeting, Detroit, Michigan,
June 1966.
(2-12) M. G. Jacko and R. M. Rusnak, "Physical Properties of Disc
Pads and Rotors Dynamometers. Tested at 100 mph," Bendix
Progress Report, May 1969.
(2-13) J. M. Herring, "Mechanisms of Brake Fade in Organic Brake
Linings, "SAE Paper 670146, presented at the SAE Annual
Meeting, Detroit, Michigan, January 1967.
(2-14) W. M. Spurgeon, "Increasing the Service Life of Friction
Materials," Bendix Progress Report, June 1969.
(2-15) W. M. Spurgeon and A. R. Spencer, "Reliability and Durability
of Automative Friction Materials," Bendix Technical Journal,
2, (No. 3), 57-66 (Autumn 1969). " ~~
2-25
-------
(2-16) F. P. Bowden and D. Tabor, The Friction and Lubrication of
Solids, Clarendon Press, Oxford, England, p. 53, 1950.
(2-17) E. Rablnowicz, Friction and Wear of Materials, John Wiley
and Sons, New York, p. 89, 1965.
(2-18) S. K. Rhee, J. L. Turak, and W. M. Spurgeon, "An Inertial
Dynamometer Evaluation of Three Alloys for Automotive
Brake Drums," SAE Paper 700138, presented at the SAE
Automotive Engineering Congress, Detroit, Michigan,
January 1970.
(2-19) S. K. Rhee, "Influence of Rotor Metallurgy on the Wear of
Friction Materials in Automotive Brakes," SAE Paper 710247,
presented at the SAE Automotive Engineering Congress,
January 1971.
(2-20) S. K. Rhee, "Wear Equation for Polymers Sliding Against
Metal Surfaces," Journal of Wear. 16^ p. 431 (1970).
2-26
-------
SECTION 3
MATERIALS SELECTIONS
3.1 BACKGROUND
Friction materials and rotor materials vary in composition accord-
ing to their source. There are original equipment manufacturers (OEM)
and aftermarket (AM) friction materials in addition to foreign friction
materials; there are wide variations according to use and origin.
Friction materials are the expendable item of the friction pair. Con-
sequently, friction materials are usually replaced two to five times
during a vehicle's life-time, while rotor materials are seldom replaced.
However, rotor materials are occasionally turned, that is, the rubbing
surface is machined so that fresh metal is exposed as a new rubbing
surface.
The asbestos content of any particular friction material is not
known, as this is information proprietary to the manufacturer. With
the use of modern analytical tools, it is possible to estimate the
asbestos content to the nearest + 2 weight percent. Thermogravimetric
analysis yields the organic/inorganic ratio as well as the inorganic
residue remaining above 800°C. X-ray diffraction indicates the inorganics,
other than asbestos, and their relative amounts.
3.2 MATERIALS SELECTIONS FOR PROGRAM
3.2.1 Friction Material Selections
A completely balanced program would contain friction
materials comparable to most of those in normal customer usage. If a
large number of tests can be run, it is easy to fulfill that requirement.
If only a small number of tests can be run, the selections are less
representative and much more critical. The objective of the program
was to obtain brake emissions from disc and drum friction materials,
OEM and AM friction materials, friction materials from several different
manufacturers, both new and used friction materials, and repeats of at
least one axle set of friction materials. This was a considerable task
since only a limited number of tests were funded. Three vehicle tests
were planned in such a way as to accomplish these goals. It is believed
that the friction materials used are representative of a high proportion
of those on the road today.
A custom-size vehicle was chosen as a median between the
compacts and luxury-size vehicles prevalent in the country. The vehicle
was equipped with the front disc pads and the rear drum primary and
secondary lining combinations, listed in Table 3-1. Each of the front
axle and rear axle friction materials was produced by different manu-
3-1
-------
Table 3-1 - Vehicle Configurations and Lining Selections
Test
Number
1
2
3
Description
Original
Equipment
Aftermarket
Equipment
Aftermarket
Equipment
Lining
Selections
Front Disc: TP-1003
Drum Rear:
Primary: 4641
Secondary: H3133
Front Disc: R-4528-4-FF
Drum Rear:
Used OEM Combination
from Test 1.
Front Disc: WB-60-FF
Drum Rear:
Primary: ABB-249-FF-PRI
Secondary: ABB-250-FF-SEC
Manufacturers
Panelyte Division
Thiokol Corporation
Friction Materials Division
Bendix Corporation
Raysbestos-Manhattan Corp.
Friction Materials Division
Bendix Corporation
Worldbestos Division
Firestone Tire & Rubber Co.
ABEX Division
American Brakeblock Corp.
Remarks
• Class A type
organic disc pads.
• No metallic chips in
any linings
• Discs were not turned
• Drums were not turned
• Disc pads and secondaries
contained brass chips.
• Disc were turned.
• Drums were turned.
-------
facturers. The vehicle was received new with less than 5 miles on the
odometer. Prior to vehicle test 1, all rotors were adjusted to their
OEM condition and unused disc pads and linings were installed to replace
those with partial use. Vehicle test 1 was made with the OEM test con-
figuration.
Vehicle test 2 was a simulation of a typical consumer prac-
tice: the replacement of the front axle friction materials only (Table
3-2). The discs and drums were not turned. The rear lining combination
was considered "a repeat." The rear lining combination was also consider-
ed as an extended test of "used" friction materials to ascertain the
nature of the brake emissions with extended use against their original
rotor. The front disc pads were purchased as aftermarket friction
materials sold in the Detroit area. The manufacturer was among the
larger AM manufacturers.
Table 3-2 - Surface Roughness Measurements on
Turned Discs and Drums for Vehicle Test 3
Specification
As Machined
Front Brakes
Right
(Shrouded)
15-80 micro
28-30
Left
(Normal )
inches
27-32
Rear Brakes
Right
(Shrouded)
60-120 micr
90-95
Left
(Normal)
oinches
75-85
Vehicle test 3 was a simulation of a second consumer prac-
tice: the replacement of friction materials on both axles in addition
to turned discs and drums (Table 3-1). The final conditions of the
rotors and drums are listed in Table 3-2. The front and rear axle fric-
tion materials were produced by manufacturers different from those
for the friction materials used in any other vehicle tests, and both
manufacturers were among the larger AM manufacturers.
Briefly summarizing the three vehicle tests, five different
friction material manufacturers are represented. Both OEM and AM disc
pads and drum linings were selected. The OEM manufacturers represented
supply a large part of the OEM market and the AM manufacturers repre-
sented supply a large part of the aftermarket. All AM friction materials
were purchased over-the-counter at various locations in the Detroit area.
3.2.2 Contents of the Friction Materials
The asbestos content of the friction materials used was
determined by the analytical methods mentioned earlier. The percent of
asbestos estimated for each material is listed in Table 3-3. This infor-
mation was obtained in order to ascertain, in later stages of the program
whether there is any correlation between the asbestos content of a fric- '
tion material and the asbestos content of its wear debris.
3-3
-------
u>
Table 3-3 - Estimated Asbestos Content
Number
No. 1
No. 2
No. 3
Description
ORIGINAL
EQUIPMENT
AFTERMARKET
AFTERMARKET
Lining
Identifications
Front Disc: TP-1003
Inner
Outer
Drum Rear:
Primary: 4641 (EBEF)
Secondary: H3133 (DUGF)
Clutch: US 969
(Used in all tests)
Front Disc: RM R4528-FF
Rear Drum: Used OEM Combination
4641 H3133
Front Disc: WB 60-FF
Rear Drum:
Primary: ABB-249-FF-PRI
Secondary: ABB-250-FF-SEC
Estimated Wt %
Total
Residue*
60
61
68
59
66
63
71
63
66
Olivine
55
56
63
55
30
60
52
63
62
Other**
5
5
2
4
36
3
19
_
4
Asbestos
64
65
76
64
35
70
60
74
73
*By thermogravimetric analysis at 900°C.
**Estimated from x-ray diffraction.
-------
SECTION 4
VEHICLE AND INSTRUMENTATION
4.1 VEHICLE DESCRIPTION
In this program, a passenger car of medium weight (4850 Ibs
test weight), produced in high volume was selected. It was equipped
with a three-speed manual transmission, ventilated cast-iron disc
brakes on the front, and cast-iron drum brakes on the rear. This
vehicle was selected in order that the emissions from clutches and
from disc and drum brakes could be tested simultaneously on a vehicle
size representing a large percentage of the present vehicle popula-•
tion. A detailed vehicle description is given in Table 4-1.
Table 4-1 - Test Vehicle Description
General Description
1971 two-door hardtop
V-8 engine
Three-speed standard-shift transmission
Power brakes (disc front/drum rear)
Power steering
Air conditioning
Vehicle Weight
Curb weight: Approximately 4000 Ibs
Test weight: 4850 Ibs (with driver and passenger)
Tires
H 78-15
Brakes
2
Front Disc: Inner Pad Area: 8.5 in
2
Outer Pad Area: 11.2 in
Rear Drum: 11 inch diameter by 2-1/2 inch
2
Primary Lining Area: 21.0 in
2
Secondary Lining Area: 27.3 in
4-1
-------
4.2 BRAKE TEST INSTRUMENTATION
The vehicle was instrumented with standard brake test instrumentation
(Figure 4-1):
Brake pedal application counter
Front and rear brake hydraulic pressure gages
U-tube decelerometer
Brake lining temperature pyrometers for each wheel (thermocouples
were placed in one lining of each wheel in accordance with the SAE
specification J-843
Twelve-position thermocouple switch and pyrometer to monitor gas
trap and particle trap collector temperatures
4-2
-------
BRAKE
HYDRAULIC
PRESSURE
GAGES
BRAKE PEDAL
APPLICATION
COUNTER
BRAKE
LINING
PYROMETERS
12-PLACE
THERMOCOUPLE
SWITCH
Figure 4-1 - Vehicle Instrumentation for Friction Material Testing
4-3
-------
SECTION 5
EMISSIONS COLLECTION SYSTEMS
5.1 OPERATION REQUIREMENTS
5.1.1 Operation and Design Criteria
Only 100 percent collection can assure a reliable measure
of the total emissions from the clutch, drum and disc brakes. The com-
posite nature of the emissions, including gases, volatile liquids, and
solid particles, makes it impossible to obtain a representative sample on
anything less than a 100 percent collection. The first requirement for
the emissions collector, then, was that it collect all the particle and
vapor emissions from the clutch and brakes. It also had to store these
emissions during a complete test cycle without changing them.
Another important requirement for the emissions collector
was that it should prevent intrusion of contaminants, or at least of
contaminants that could not be positively distinguished from brake emis-
sions. Oxygen and nitrogen had to be excluded from this restriction since
operating in an inert gas atmosphere would seriously change the character
of the emissions.
The collection systemshould not, of course, significantly
change the ordinary operating conditions of the clutch or brakes. This
means it should not materially change the heat flow and that the air flow
rate through clutch and brake chambers had to be similar to that under
ordinary operating conditions. The flow pattern did not need to be iden-
tical since this would not affect the generation of emissions at low tem-
peratures, but only the way in which they were carried out of the brake
and clutch chambers.
The front disc collector had to be capable of operating at
brake temperatures to 650°F (340°C) with the sealing surface operating
up to 400°F (205°C). The rear drum collector had to be capable of operat-
ing at brake temperatures to 500°F (260°C), the sealing surface operating
to approximately 350°F (177°C). The clutch collector had to be capable
of operating at temperatures to 250°F (121°C).
Finally, the collection system had to permit easy separation
and analysis of the different types of emission - large and small parti-
cles down to 0.2 pm size, condensable vapors, and volatile gases. If
expensive preliminary separations had to be carried out in the laboratory,
an already difficult and time-consuming analysis would become even more
extended and costly.
5-1
-------
The major requirements for the emissions sample collection
system may be summed up, therefore, as follows:
o Collect all particulate and gaseous emissions,
« Store collected emissions unchanged,
o Prevent intrusion of contaminants,
o Maintain ordinary braking and clutching conditions,
o Be operable at high temperatures, and
* Permit easy separation and analysis of emissions.
5.1.2 Emission Expected
Appendix A shows a series of wear debris calculations which
included the chemical composition and the amounts of wear debris expected.
This information was necessary to insure proper sizing of the emission
collection hardware.
5.2 OVERALL DESIGN CONCEPT
5.2.1 Air Flow of a Typical Collection System
The basic design concept of each brake emissions collection
system is shown in Figure 5-1. Air from inside the vehicle was pulled
into a bed containing Drierite and calcium oxide pellets which remove
water and carbon dioxide from the air. After passing through the bed,
the air passed through a filter to remove all particles larger than
0.2 ym (8 x 10~6 inches). The filtered air was then routed to the sealed
brake or clutch assembly through clean Teflon tubing. The air stream,
along with wear particles and gases, then passed out of the brake or
clutch through Teflon tubing surrounded by heating coils to keep the gases
at 200°F (93°C) in order to avoid condensation. This stream passed
through two filters to remove the airborne particles and preserve them
for analysis. The stream then passed through three cold traps in order
to condense and trap the gases evolved during braking and preserve them
for analysis. Finally, the air stream passed through a flowmeter, the
vacuum manifold, and an air pump run by the vehicle engine, finally being
expelled to the atmosphere.
Figure 5-2 shows the engine-driven air-pump installation
under the hood. The pump was run by a belt attached to an added pulley
attached to the drive shaft of the alternator. Thus the air pump had
two modes of operation:
9 During engine idle, the pump ran at a low
fixed speed.
• During vehicle operation, the pump ran at
a speed proportional to the engine speed.
5-2
-------
BRAKE
ASSEMBLY
INLET AIR
FILTER
DRIER
CARRIER
" AIR
0.2 ju ,
'QAO.Q.QA!
PARTICLE
FILTERS
HEATER COILS'
•utra
i—R)
:TER VACUUM V X
MANIFOLD I |
9
AIR PUMP
GAS
COLLECTION
SYSTEM
Figure 5-1 - Schematic Diagram for Air Flow of Typical Particulate
and Gas Emission Collection System
U1
OJ
-------
T
--
TUBE CONNECTION TO
VACUUM MANIFOLD
Figure 5-2 - Air Pump Installation in Engine Compartment
-------
5.2.2 Collection Systems Used
Collection systems such as those described above were at-
tched to the following: right front disc brake, right rear drum brake,
and the clutch. The left front and left rear brakes were not modified
in any way but were monitored to insure that the wear on the right side
was not changed significantly by the collectors.
Figure 5-3 shows, mounted in the front seat of the test
vehicle, the front-brake inlet air filter and gas collection system, the
clutch gas collection system, and the twelve-position thermocouple switch
and pyrometer used to monitor gas and filter trap temperatures. Fig-
ure 5-4 shows, as mounted in the rear seat of the test vehicle, the
rear-brake air filter and gas collection system, the clutch air filter,
and the electrical system.
5.2.3 Electrical System
The electrical system mounted in the rear seat consisted
of two batteries, one inverter, and two variable transformers, and was
used to supply AC voltage to the heating coils.
Figure 5-5 shows the schematic for the electrical system.
The inverter was capable of changing 12-volt DC power to
60-Hz, 120-volt power with an output of 400 watts continuously. Two extra
batteries were installed to provide sufficient electrical capacity for 10
hours of testing. The inverter was separated by relays from the batteries
in order that peak voltages occurring during vehicle start up did not
damage the inverter. This system consisted of power and latching relays
and a pushbutton switch. After the vehicle was started, the pushbutton
switch was used to energize the latching relay which in turn energized
the power relay, providing DC power to the inverter. When the vehicle
was shut down for any reason, the power to the latching relay was removed
and thus the power relay was also de-energized. The AC output was regu-
lated to the heater through use of two variable transformers thus allowing
temperature adjustment. The batteries were recharged each night in order
to provide sufficient power for the following day.
5.3 PARTICULATE FILTERS
5.3.1 Filter Holders
Two Gelman 47 mm filter holders joined in series were used
for the collection of airborne particulates. These holders were sealed
with 0-rings, fabricated from stainless steel for protection against
corrosion, and loaded with standard 47 mm diameter filters. Nuclepore
filters were used. These filters were made from a smooth film of poly-
carbonate plastic with a number of circular pores through them. The
pores did not restrict the flow of gases significantly as particle col-
lection proceeded. The filter holders were heated by tape heaters wound
5-5
-------
CLUTCH GAS
COLLECTION SYSTEM
12 PLACE
THERMOCOUPLE SWITCH
GAS COLLECTION
SYSTEM
HOLD-DOWN STRAP
FRONT BRAKE GAS
COLLECTION SYSTEM
THERMOCOUPLE
JUNCTIONS
FRONT BRAKE INLET AIR
DRIER AND FILTER
Figure 5-3 - Vehicle Instrumentation (Front Seat Area)
5-6
-------
DC TO AC
VOLTAGE INVERTER
VARIAC TO CONTROL
VOLTAGE TO HEATERS li
REAR BRAKE
GAS COLLECTION
SYSTEM
CLUTCH INLET
AIR DRIER AND FILTER
I >-
REAR BRAKE
INLET AIR
DRIER AND FILTER
Figure 5-4 - Vehicle Instrumentation (Rear Seat Area)
5-7
-------
VARIABLE
TRANSFORMER
Ln
00
CLUTCH PARTICIPATE
TRAP & LINE HEATERS
VEHICLE
BATTERY
(12VDC)
REGULATOR
VARIABLE
TRANSFORMER
AC
OUTPUT
FRONT BRAKE PARTICULATE
TRAP & LINE HEATERS
REAR BRAKE PARTICULATE-
TRAP & LINE HEATERS
DC/AC
INVERTER
DC INPUT
1
PUSHBUTTON
SWITCH
n
di
o>
Figure 5-5 - Electrical Schematic for Particulate Trap and
Transfer Line Heaters
-------
around the outside and controlled by a variable transformer within the
test vehicle. The same configuration was used in all three collectors
(front brake, rear brake, and clutch).
5.3.2 Filter Flow Characteristics
At the beginning of the program, no data were available
for the flow characteristics for any type of filter when loaded with
brake wear debris. Consequently a series of simple tests was performed;
the results are included as Appendix B. The following results were
noteworthy:
« The pressure drop change across an 8.Op
Nuclepore filter loaded with up to 1.0
gram of wear debris was not high enough
to present problems in the program.
• Wear debris was easily removed from Nuclepore
membranes such that no significant error was
introduced when debris from several membranes
was comb ined.
5.4 GAS COLLECTION SYSTEMS
5.4.1 Design and Fabrication of Traps
To withstand handling and road shocks, it was deemed neces-
sary to design and build rugged gas traps for both condensable and non-
condensable gases.
Figures 5-6 shows the schematic for the condensable-gas
trap. The body of the trap^nd the tubing were made of stainless steel.
The top was threaded so that it seated against an 0-ring to provide a
vacuum-tight seal.
Figure 5-7 shows the schematic for the noncondensable-gas
.traps. The trap was designed so that it could be filled with granular
activated charcoal. The charcoal was held 3/8 inch above the bottom of
the.trap by a stainless steel screen. This allowed a small volume for
the gases to permeate toward the outside walls before they were absorbed
on the charcoal surfaces or passed through the charcoal bed to the exit
port.
Figure 5-8 shows the schematic of the activated-charcoal
trap top and the plug used to fill the trap once the top had been threaded
on. An 0-ring against a 45-degree bevel provided a vacuum seal.
Figure 5-9 shows the complete gasi trap. Figure 5-10 shows
an exploded view of the trap.
5-9
-------
t
1"
1
, FRONT £ I
I ' J
I* ! 5/8" »..*— 1" •]
1/2"
ro.D.
BACK
:; 1/8-
; ; 3/8-
DETAIL "A"
. 304 S.S.
SEAMLESS TUBING
1"O.D. 13 GA.
1/4" O.D.S.S. TUBING
•WELD-AIRTIGHT
0.810" I.D.
(0.095 WALL THICKNESS)
45°
f 0.070"
i
t
PARKER
SIZE 2-019
CLASS AN
O-RING
DETAIL "A"
MATERIAL 316 STAINLESS
STEEL
Figure 5-6 - Condensable-Gas Trap
5-10
-------
MATERIAL: STAINLESS STEEL
t
1"
1
FRONT
1 3/4"
il
2 1/4" DIA. -~ — v
I
4
304 S. S. TUBING
2" O.D. 11GA.
1/4" O.D. _^,
S.S. TUBING
L
3/8"
1
1
ifr
.A
2" O.D.
1.760" I.D.
»•
BACK
) , DETAIL "A"
I
S.S.
/SCREEN
I '
t
1/8"
1/8"
3/8"
a f^— 0.10"
4/4 1
1 IT
PARKER
088(r SIZE 2-031
' ' 1.749" I.D.
DETAIL "A"
0.070"
Figure 5-7 - Activated-Charcoal Gas Trap - Sectional View
1/2"-20 THRU TOP
1/8" WIDE x 3/32" DEEP SLOT
1/8"
1/2"
1/2"
-PARKER
SIZE 2-014
, 0.070"
TOP
-1/2" - 20 THREAD
PLUG
Figure 5-8 - Activated-Charcoal Gas Trap - Top View
5-11
-------
Figure 5-9 - Activated Charcoal Gas-Trap
5-12
-------
FACE FOR
O-RINGSEAL
PLUG FOR
ADDING ACTIVATED
CHARCOAL
Figure 5-10 - Exploded View of Activated Charcoal Gas-Trap
I
I—"
U)
-------
5.4.2 Operation
The gas traps were connected in series such that the gases
flowed through the condensable-gas trap first and then through two
noncondensable-gas traps containing activated charcoal. Valves were in-
stalled at the inlet and exit of each trap. The traps were kept in a
custom-made metal box lined with styrofoam, 1-1/2 inches thick, as shown
in Figure 5-11.
The three gas traps were held at approximately -70°C (-95°F)
with solid carbon dioxide. For the disc brake collector, which had higher
gas flow rates, a 2-foot length of 1/4-inch OD tubing was added,before
the condensable gas trap. This was found necessary to prechill the gases,
or otherwise no condensation would occur in the first trap.
5.5 DISC BRAKE COLLECTOR
5.5.1 Shroud Design and Construction
The brake emissions collector for the right front disc
brake consisted of a sheet-metal duct, or shroud, completely covering
the caliper and disc, and an emission storage unit consisting of particle
filters and gas traps. The shroud is shown in Figure 5-12. It served
as a collector and duct to carry the gaseous emissions into the delivery
tube to the gaseous-emission storage unit.
Figure 5-13(a) and 5-13(b) show the 2 views of major sheet-
metal portions of the disc brake collector (parts were stainless steel
to avoid corrosion) and Figure 5-14 shows the entire collector system
with the disc brake.
Front and rear views of the collector system, as mounted
on the vehicle, are shown in Figures 5-15 and 5-16.
5.5.2 Rotating Seal
5.5.2.1 Initial Design and Problems
The original design of the rubbing seal for the disc brake
shroud was a face seal of Teflon (Figure 5-17). Problems arose with this
design because of difficulty in realigning the seal after dismantling the
shroud for maintenance. When the collector was opened for inspection and
then resealed, the out-board shield was not relocated in the exact same
position each time. The out-board face was usually slightly cocked in
a different manner each time.
The out-board face held the rotating seal. A 1-degree
shift of the face cause a 0.060-inch deflection at the groove where the
Teflon was sealed. A deflection greater than 0.020 inch was found too
great for the seal's Teflon 0-ring to make up and consequently nonrepre-
ducible sealing and leaking occurred.
5-14
-------
STYROFOAM
VALVES TO
SEAL TRAPS
METAL
BOX
NON-CONDENSABLE
GAS TRAPS
AIR OUT
CONDENSABLE
GAS TRAP
GASES & AIR IN
623-71
Figure 5-11 - Gas Collection System
-------
TIRE
BRAKE
PAD
BEARING
DUST
CAP
THERMOCOUPLE
(FOR BRAKE
TEMPERATURE)
SPLASH SHI ELD
(MODIFIED)
ROTATING
SEAL
TO
EMISSION
"- STORAGE
UNIT
Figure 5-12 - Sectional View - Disc Brake Shroud
5-16
-------
INBOARD RING AND
CALIPER COVER
MODIFIED DUST
SHIELD
OUTBOARD
SHIELD
CALIPER TOP
COVER
656-7)
Figure 5-13(a) - Major Portions of Disc Brake Emission Collector Assembly
Ul
-------
_
h->
00
INBOARD RING AND
CALIPER COVER
Figure 5-13(b) - Major Portions of Disc Brake Emission Collector Assembly
-------
Figure 5-14 - Disc Brake Emission Collector Assembly - Exploded View
-------
• BRAKE HYDRAULIC
LINE
BRAKE PAD
THERMOCOUPLE
DRIED AND FILTERED
INLET AIR
Figure 5-15 - Front Disc Brake Emission Collector Installed on Vehicle
-------
BRAKE PAD
THERMOCOUPLE
Figure 5-16 - Back View of Front Disc Brake Emissions Collector
Showing Instrumentation
-------
SLIDING SEAL
RETAINING PLATE
GROOVE MACHINED
INTO OUTBOARD SHIELD
Figure 5-17 - Initial Design (MKI) for Rotating Seal of Disc
Brake Collector
5.5.2.2 Final Design
A new sealing system was designed, using a shaft-type
spring-loaded seal, of commercial manufacture, made of graphite-filled
Teflon. Figure 5-18 shows the drawing of the sealing system and Fig-
ure 5-19 shows the details at the sealing surface.
5.5.3 Thermal Control Aids
During preliminary testing, it was apparent that the shrouded
disc brake was running measureably hotter than the unshrouded disc brake.
Therefore, various cooling aids were devised to reduce this temperature
differential. Three cooling aids were used:
(1) Black oxide coating of the shroud to improve heat radiation.
(2) Water sprinkling system connected to the windshield washer
pump for cooling.
(3) Open or mag-type wheel for improved convective cooling of
the shroud.
These additions are shown in Figures 5-20 and 5-21.
-------
4*8 TWO ./flrt/ip DePTH - HOueS
UOT BcifcOC.! ~THQ.O SOCtc.
-/8 n/U 06PTH- HOUSS
DOT gneaic. Tfteo saeic.
HOLES eO-SPC otJ 7-125 6-C.
§EMO. MUCH FILE j
LIHOP T"
CTION |
-F.D ,»,,d «c.»niiff"
rE: THB IS A BC/RLD INTERNAL DRA*HG.|oe
-------
DISC
--4-
HUB
4340 PR ESS FIT
RING - RUBBING SURFACE
GRAPHITE
FILLED
TEFLON
SEAL
n
di
DISC BRAKE
SHROUD
Figure 5-19 - Details of Disc Brake Collector Rotating Seal
5-24
-------
a SHROUD
•I THERMOCOUPLE
WATER SPRINKLING
SYSTEM
I
to
Ln
Figure 5-20 - Front Disc Brake Emissions Collector Showing Thermal
Control Aids
-------
Ul
r J
SHROUD
THERMOCOUPLE
OPEN WHEEL
(MAG TYPE)
Figure 5-21 - Right Front Wheel of Test Vehicle
-------
5.6 DRUM BRAKE COLLECTOR
5.6.1 Initial Designs and Rotating-Seal Problems
The original concept for the sample collector on the right
rear collector was planned such that the drum and backing plate formed
the shroud along with a rotating seal. This approach was used in order
to minimize changes to the cooling efficiency of the drum.
The first design concept (MKI) was a face seal of Teflon
kept in contact with the polished edge of the backing plate by a silicone
rubber 0-ring (see Figure 5-22). This seal had a short service life, be-
cause of alignment problems and the high rubbing speeds.
The second design concept again attempted, to use the back-
ing plate and drum as the major components of the shroud. However, this
design (MKII) incorporated a shaft-type spring-loaded seal, of commercial
manufacture, made of graphite-filled Teflon. The seal manufacturer in-
dicated that this seal could sustain the rubbing speeds and temperatures
involved (2000 ft/min and 400°F). This seal design is shown in Fig-
ure 5-23. Figure 5-24 shows the modified backing plate and drum made
from this design. Figures 5-25 and 5-26 show front and rear views of
the system as mounted on the vehicle. The seal in this system failed
0.23"
12.37"
DIA.
TEFLON
SEALING
RING
BACKING PLATE
"9
Q.
Figure 5-22 - First Seal Design (MKI) for Drum Brake
5-27
-------
10
S.K W/KING
II.030D.J?6F
ZI8 D.THRU
C'BOEE^-403.
16 HOLES EQUI-SPCD
"-060a
CBOKE-ZOOP.X
10.700 D. .I4ODP. 1C, HOLES
5.F. W/5UPP.PING EQUI-SPCD
PLT
Z-IOO B.C.
I/.905D.
5.F.WITH SUPP.R1NG
WITH RET. RIWG
MINU'CUT — ^
C(.EflR)
3
II.3ZC
3D.
in a
i
7AD
-
-\ i
|v
r
.75C
-»a-3ZU*JCTHOTHRU
16 HOLES E
-------
SEAL RUBBING
SURFACE
SPRING LOADED
TEFLON SEAL
(a) Modified Rear Brake Drum Backing Plate Showing Spring-Loaded
Teflon Seal
HARDENED
STEEL RING
SEAL RUBBING
SURFACE
(b) Modified Rear Brake Drum Showing Hardened Steel Ring for
Rotating Seal
Figure 5-24 - Details of MKII Rotating Seal
-------
BRAKE LINING
THERMOCOUPLE LEAD
EMERGENCY BRAKE
CABLE
SILICONE RUBBER
SEALANT
Figure 5-25 - Rear Drum Brake Emission Collector
-------
after a short time as shown in Figure 5-27. On investigating the failure,
three major problems were found:
(1) High interface speeds (1450 ft/min at 40 mph).
(2) Increase in seal interface pressure because of lack of
concentricity and expansion of the drum.
y
(3) Heat input to the seal from the braking action and dis-
tortion of the drum from the braking action.
5.6.2 Final Design
In order to correct the problems described above, a third
seal design (MKIII) was developed. This design removed the rubbing seal
from the drum to the axle housing area, decreased the diameter (and thus
the rubbing speed) of the seal and improved concentricity by using ac-
curate alignment of components and by modifying the rear axle hub to
align the drum concentric to the axle bearings within 0.001 inch. A
tapered lead was used on the axle hub to facilitate mounting of the drum.
This design is shown in Figure 5-28. An. outboard view of this sytem
without the drum is shown in Figure 5-29. Outboard and inboard views
of the assembled system are shown in Figures 5-30 and 5-31. This is
the system which was used in all testing.
5.7 CLUTCH COLLECTOR
The clutch collector system consisted mainly of a filtered air
inlet and an outlet to the sample storage system with all other external
holes sealed. A schematic of the system is shown in Figure 5-32 and a
photograph of the system installed is shown in Figure 5-33.
5-31
-------
Figure 5-26 - Rear View of Rear Drum Brake Emissions Collector
Showing Instrumentation
RUBBING SURFACE
SEPARATED
FROM SEAL
P-82-196-2
Figure 5-27 - Completely Worn Seal from MKII Rear Drum Brake Collector
-------
DRUM
BRAKE
LINING
GRAPHITE
FILLED
TEFLON
SEAL
Figure 5-28 - Sectional View of Drum Brake Shroud (MKIII)
5-33
-------
-
JL
-
NUT AND SCREW
REPLACING RIVET
BRAKE LIMING
THERMOCOUPLE
Figure 5-29 - Outboard View of Rear Drum Brake Emissions Collector
Interior
-------
U:
I
Ul
PRECISION DRUM
CENTERING HUB
Figure 5-30 - Assembled Rear Drum Brake Emissions Collector
-------
I
u>
AXLE SEAL AND
STATIONARY
SEAL RING
Figure 5-31 - Inboard View of Assembled Rear Drum Brake Emissions
Collector
-------
FIREWALL
AIR FILTER
(TO REMOVE
H20&C02)
TRANSMISSION
EMISSIONS
COLLECTION
DUCT
CLUTCH
Figure 5-32 - Emission Collection System for Clutch
Co
-------
OJ
00
Figure 5-33 - General View of Covered Clutch
-------
SECTION 6
INERTIA DYNAMOMETER TESTING OF THE DISC-BRAKE COLLECTOR SYSTEM
6.1 OBJECTIVES
There were three major objectives for the inertia dynamometer tests.
First, it was necessary to demonstrate that a brake can be completely
enclosed and not change in its mechanical operation. Second, it was nec-
essary to demonstrate that the thermal response would not be seriously
altered compared to the normal brake operation. Finally, the most crit-
ical unknown was the rotating seal operation.
6.1.1 Demonstration of Collection System Operation
The disc brake on the vehicle was designed to operate as a
relatively open brake with a substantial air flow over its component parts.
Shrouding of the caliper and rotor was a radical change from its original
designed operating mode. The shrouded brake for emissions collection was
a unique piece of hardware and thus it required testing on the inertia
dynamometer, where modifications and adjustments could be made rapidly
and rationally.
6.1.2 Thermal Response
It was known that shrouding would change the brake cooling.
However, the effects of pulling air through the brake shroud even while
the vehicle was stationary would negate some of the shielding effect of
the shrouding. Thus it was necessary to determine the thermal response
of the shrouded brake compared with that of its original design and to
ascertain the effects of any thermal differences.
6.1.3 Rotating Seal Durability
At the beginning of the program, it was believed that the
rotating seal life would be the most critical problem. Several questions
arose. Would the initial design be suitable? Was a good back-up design
available? Would any rotating seal survive under the conditions of opera-
tion? Were the claims of the seal manufacturers accurate and reliable?
Thus the most critical objective of the inertia dynamometer test was to
demonstrate the operation of a suitable rotating seal and to demonstrate
its durability.
6.2 DYNAMOMETER TEST RESULTS
6.2.1 Sealing Practices for Disc Brake Collector
Figure 5-14 shows the major portions of the front disc brake
collector. The silicone rubber gaskets form the major portion of the
6-1
-------
seals between the joints of the metal shroud. Once assembled on the wheel
assembly, there were many leaks around the small screws holding the shroud
together.Other leaks appeared at the welds on the outboard shield and the
fittings on the modified dust shield. The leaks around the welds^were
eliminated by returning the parts to the shop for additional welding. The
other leaks were eliminated by the liberal use of cured-in-place silicone
rubber (see Figures 5-15 and 5-16).
6.2.2 Thermal Response Results
The first testing performed was to determine the thermal
response of the shrouded disc brake as compared with that of the unshrouded
disc brake. The inertia dynamometer used was set up to simulate a load
of 1200 Ibs on the brake, which is approximately 25 percent of the vehicle
test weight (Figure 6-1) . Each stop was from 30 mph to 0 mph at 300 psi
line pressure. Stops were made at the rate of one per minute. The tests
were run in still air. Figure 6-2 is a plot of temperature versus time
for a thermocouple located in the outer pad and a thermocouple mounted
on the backing plate. The solid curves are for the regular or unshrouded
system, while the dashed curves are for the shrouded system, with no air
being pumped through the system. Figure 6-2 shows that the shrouded brake
heats faster than the unshrouded brake which was to be expected.
Figure 6-3 is a plot of the data from a series of tests on
the shrouded disc brake system for thermal response of the outer brake pad
under various air flow conditions. The plot shows temperature versus total
energy input to the brake. The lowest curve on the plot is for the un-
shrouded brake and the highest is for the shrouded brake with no air flow
as previously shown in Figure 6-2. The two middle curves are for air
flows of 64 and 110 standard cubic feet/hour. The results show that
increasing the air flow above about 60 SCFH (i.e., doubling the flow)
had little effect on the cooling of the brake. Thus 60 SCFH was chosen
as the flow to be set in the test vehicle.
6.2.3 Rotating Seal Operation
The initial rotating seal design described in Section 5»5.2.1
did not provide a suitable seal. It was therefore replaced with the de-
sign described in Section 5.5.2.2. The following tests were performed
with the second design.
Testing was done to determine rotating seal effectiveness.
The method used to determine the seal leakage rate was to apply air pres-
sure to the closed shroud at 3.5 psi and measure the time required for the
primary pressure regulator reading to drop from 1500 psi to 500 psi while
the tank valve was closed. The total flow through the secondary regulator,
set at 3.5 psi, was about 137 cc during this time. Figure 6-4 shows a
plot of the leakage times versus wheel speed for a new seal, both lubri-
cated and unlubricated. As can be seen, the leakage time increases as
speed increases for both lubricated and unlubricated seals. Since the
6-2
-------
Figure 6-1 - Disc Brake and Emissions Collector Assembly Installed
on Dynamometer
lubricated seal had lower leakage rates, the vehicle tests were all run
with lubricated seals. This leakage test method was used throughout vehi-
cle testing and seals were changed whenever the leakage rate fell below
20 seconds on a cold system.
One seal was then tested for a total of seven hours at 50
mph and the results of the leakage tests versus speed are shown in Fig-
ure 6-5. The seal was removed after testing and inspected. Figure 6-6(a)
shows that most of the seal experienced little wear during the test.
However, one section, approximately one inch long, showed abnormally high
wear to a point of imminent failure (Figure 6-6(b)). This was apparently
caused by spring distortion in this area causing higher pressure. Sub-
sequent seals were inspected for this defect prior to assembly and this
problem was avoided in all subsequent tests.
6-3
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400-r
REGULAR SYSTEM (EOM)
___ — SHROUDED SYSTEM
CHANGE O OUTER PAD TEMPERATURE
BACKING PLATE TEMPERATURE
20 40
60 80 100
TIME (MINUTES)
120 140 160
Figure 6-2 - Disc Brake Comparative Thermal Response Time
(Static Air)
400 -,
<
cc
100-
O O UNSHROUDED 7/22/71
O—O SHROUDED W/NO AIR FLOW 9/29/71
a—£ SHROUDED W/64SCFH AIR FLOW 12/10/71
SHROUDED W/110 SCFH AIR FLOW 12/14/71
6 8 10 12 14
TOTAL ENERGY INPUT (CUMULATIVE STOPS/UNIT TIME)
16
18 20
Figure 6-3 - Comparative Thermal Response Tests on a Disc Brake
6-4
-------
100-
SEAL LUBRICATED
WJTH DUPONT -
—- KRYTOX 24OAC '
V
UNDESIRABLE
20 30
WHEEL SPEED (MPH)
Figure 6-4 - Seal Leakage Versus Flow for Disc Brake Emissions Collector
Showing Differences Between Dry and Lubricated Seals
WHEEL SPEED(MPH)
Figure 6-5 - Seal Leakage Rate Versus Speed Showing Differences
Between New and Used Seal
6-5
-------
(a) Normal Worn Seal
P-8 2-99-3
P-8 2-99-3
(b) Abnormal Wear to the Point of Imminent Seal Failure
Figure 6-6 - Seals From Disc Brake Emissions Collector Showing
Normal and Abnormal Wear
6-*
-------
A new rotating seal was installed at the beginning of the
tests described in the next section. The initial seal integrity was
equivalent to that of the seal used during the durability test runs.
Figure 6-7 shows the data for this seal. The seal integrity was found to
improve as the seal wore in. Moreover, the leakage rate further decreased
as the wheel speed increased. Finally, the data for this seal agreed with
all the trends shown by the earlier seals.
6.2.4 Emission Collections
A series of dynamometer tests were made to check out the
operation of the entire disc brake emissions collection system. Identify-
ing the tests by a year-month-day date code, a total of three tests were
run:
Test 11222: Baseline
Test 20105: Baseline repeat
Test 20108: Baseline plus spray
Test 20108 was similar to the other two tests except that a mixture of
5 percent sodium chloride and 5 percent barium sulphate in water was
periodically sprayed at the emissions collector. The salt and barytes
(50 percent through 200 mesh and 50 percent through 325 mesh) were used
to simulate a fall-winter slushy-wet road condition. Barium sulfate
was used in place of sand so that the barium could be used as a tracer
along with the chlorine in subsequent X-ray fluorescence analyses if
needed.
Each of the tests was run for two hours on the inertia dy-
namometer. Pre-run and post-run time added to the total. During the
two-hour run, 40 brake stops were made from 30 mph at 8ft/sec2 decelera-
tion rate (considered a normal stop). The wheel was run at 30 mph between
stops. The temperature-versus-time plots for both the backing plate and
the outer brake pads are shown in Figure 6-8. The reproducibility of
Tests 11222 and 20105 was good. As expected, Test 20108 ran cooler be-
cause of the cooling spray.
Table 6-1 summarizes the dynamometer test results for flow
rates, temperature control, and particulates collected. A slight decrease
in carrier gas flow rate was seen as the filter picked up wear debris;
this agreed with previous laboratory test data of pressure drop versus
flow rates for Nuclepore membranes. The temperatures of the transfer
line and filter assembly were held at 200 +_ 20°F, the target temperature
range, for the two base-line tests. The transfer-line temperature for
Test 20108 fell below this for a brief period because of cooling effect
of the spray. However, this was not considered a problem.
The particulates data are also given in Table 6-1. The
wear debris on the filter was representative of normal vehicular brake
wear debris found in drum brakes and trapped from previous Bendix sample
6-7
-------
400
300
Test 11222
Test 20105
Test 20108
Prior to Test
A After Test
10
30 40
WHEEL SPEED (MPH)
Figure 6-7 - Rotating Seal Leakage Rate Versus Wheel Speed
for Disc Brake Emissions Collector
60
6-8
-------
300
RUN NO. 11222
20105
20108
60
TIME (MIN.)
(a) BACKING PLATE TEMPERATURE:
120
300
o, 200-
LU
CC
D
CC
UJ
Q.
HI
100-
30 60 90
TIME (MIN.)
(b) PAD TEMPERATURE:
120
Figure 6-8 - Disc Brake Emission Collector Temperature
6-9
-------
dynamometer tests. The shroud samples contained mainly grease and some
Teflon-graphite wear particles from the rotating seal. The amount of
grease required was not known at the start of these tests. A liberal
amount was used initially. Due to the heat of the rotating seal and to the
air flow through the rotating seal (slight vacuum in the shroud), the
grease flowed into the shroud and coated a portion of the inside surface
near the rotating seal. This grease film attracted and held the wear
debris. Assuming that the brake lining wear debris fraction* of the
shroud sample is a constant (VLO weight percent), the total particulates
produced for each of the three tests agreed very well. The mean was
17.4 + 0.3 mg. The air-borne fractions collected on the filters showed
a wider variation with a mean of 12.8 +_ 0.5 mg.
6.2.5 System Integrity
The third test in the preceding section was carried out to
ascertain system integrity under simulated harsh road conditions. This
test was run in same manner as the first two tests except that a mixture
of 5-percent sodium chloride and 5-percent barium sulphate in water was
sprayed at the emissions collector system. A total of two liters of this
mixture, used to simulate fall-winter slush conditions, was sprayed on
the system during the test. No traces of salt or of barium sulphate were
observable on the inside of the collection system after testing. The
temperature data for the heated transfer line and particulate filters and
the particulate collection results for these tests are shown in Table 6-1.
These results show that no salt entered the shroud system, and prove the
integrity of the system used in vehicle testing.
Table 6-1 - Summary of Dynamometer Test Results
RUN
NUMBER
11222
20105
20108
CARRIER AIR FLOW (SCFH)
Initial
36
36
36
Final
31
25
26
TEMPERATURES (°F)
Transfer
Line
190-210
180-190
170-220
Filters
180-205
190-220
190-215
PARTICULATES COLLECTED (mg)
8 V Filter
10.6
9.6
10.2
0.2 |j Filter
1.7
3.6
2.7
Shroud*
48.4
41.8
46.6
Total**
17.1
17.4
17.6
REMARKS
Baseline
Baseline repeat
Salt spray used;
none detected
inside collector
*Includes grease and Teflon-graphite wear particles from seal (probably >90% of amount shown)
*Includes 10% of shroud figure
f\
No assumption as to the actual content of wear debris in the samples
taken from the brakes during the vehicle tests was necessary. Much less
grease was used and practically none of it entered the shroud during these
tests.
6-10
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SECTION 7
VEHICLE TEST SCHEDULES
7.1 RATIONALE
7.1.1 Brakes
For a given vehicle brake system, friction material wear
is primarily a function of the duty cycle. For light duty cycles, where
pad and lining temperatures remain under 350°F, low wear results and is
primarily due to the abrasive and adhesive wear mechanisms. Heavier duty
cycles at higher temperatures give some combination of thermal, abrasive
and adhesive wear. Under severe heavy duty where the use borders on
abusiveness brake fade may occur. The inability of the brakes to hold
the friction level results in part from the formation of gases (and wear
debris) at the interface.
The amounts and types of gaseous and particulate emissions,
as a function of brake duty, are not known. Moreover, as brake linings
age, changes such as "hardening" occur, possibly with changes in the wear
properties. Also, until disturbed, portions of the particulate emissions
are known to be retained inside certain areas of the foundation brakes.
Consequently, it is necessary to select a vehicle test program which will
provide some combination of normal and heavy duty service.
7.1.2 Clutches
For a given vehicle, the friction material wear in the clutch
is primarily a function of the duty performed. However, in most clutch
applications, the energy absorption and temperature rise are usually less
than in normal brake operation. Thus the wear and emission rates in clut-
ches were expected to be very low.
7.2 TYPICAL TEST CYCLES
Several acceptable vehicle test cycles have been established and
used by friction materials and brake system manufacturers. These are
varied according to life and performance requirements, and for various
stages of friction material conditions. The following test cycles appeared
to be suitable for this program.
7.2.1 Burnish
A portion of the SAE Recommended Practice: Brake System
Road Test Code - Passenger Car (SAE J843a) is called the Burnish. This
7-1
-------
test cycle is always used when the brakes are relatively new and thus is
a part of the break-in procedure for new brakes. The test requirements
are:
Stop speed: 40-0 mph
Stop deceleration: 12 fpsps
Stop interval: As required to achieve
250°F initial brake
temperature in a maximum
of one mile.
Cooling speed: 40 mph (moderate acceleration
to cooling speed).
Stops required: 200.
Optional: Inspect and/or adjust brakes
after burnish cycle.
7.2.2 Baseline
Since there was no cycle in SAE J843b comparable to a re-
peated, low duty-type baseline test, it was found necessary to adapt a
portion of some other longer test cycle. This test would be used to
serve as a reference for wear rate and brake emissions after other low
and heavy duty test cycles. The baseline test selected was three days
(12 circuits) of the Detroit Traffic Test schedule described below.
7.2.3 Detroit Traffic Test
The Detroit Traffic Test is used primarily to evaluate
friction, life, and noise of commercial brake products. The normal oper-
ating range for passenger car brakes in the test is 180 to 280°F. This
condition constitutes what a brake engineer calls a low-temperature wear
test, but is actually somewhat more severe than for most driving. Test-
ing is intentionally accelerated to reduce test costs, consequently the
test tends to be more severe than average driving.
Table 7-1 describes the detroit Traffic Test route as modi-
fied for this program. The basic downtown circuit remains the same; only
the starting and finishing routes are slightly altered. Each circuit
begins with elevated brake temperatures. The vehicle merges and flows
with the traffic during the prevailing traffic conditions. The following
variations occur:
Stop speeds: Variable: 45-0 mph maximum.
Snubs*: Variable: 45 mph maximum.
Stop deceleration: Variable: 20 fpsps maximum.
Stop interval: As required to maintain flow
in traffic.
*
Decelerations to lower speeds, but not stops.
7-2
-------
Table 7-1 - Detroit Traffic Test Route (Modified)
A. Drive from Bendlx Research Laboratories (BRL) to 12-Mile Road and Woodward Avenue via the following rout
Left on Civic Center Drive to Greenfield Avenue
Left on Greenfield Avenue to 12-mile Road
Right on 12-Mile Road to Woodward Avenue
Turn right on Woodward Avenue and park on Service Drive to check instrumentation.
B. Detroit Traffic Route:
Starting on Woodward Avenue (just South of 12-Mile Road), drive south to Adams Avenue
(starting point of downtown loop).
Right on Adams Avenue (West) to Park Avenue
Left on Park Avenue to Bagley Avenue
Right on Bagley Avenue to Third Avenue
Left on Third Avenue across Michigan Avenue to Fort Street
Left on Fort Street to Griswold Street
Right on Griswold Street to Jefferson Avenue
West on Jefferson Avenue to Washington Boulevard
Right on Washington Boulevard to Fort Street
Right on Fort Street to Cadillac Square
Right on Cadillac Square to Randolph Street
Left on Randolph Street to East Fort Street
Right on East Fort to Brush Street
Left on Brush Street to Macomb Street
Left on Macomb Street to Randolph Street
Cross Randolph Street to Broadway Avenue
Right on Broadway to Witherell Street
Right on Witherell Street to Adams Avenue
Left on Adams Avenue to Woodward Avenue
This completes one downtown loop. Complete a second downtown loop by continuing west to Park Avenue
and following around and returning to the corner of Adams and Woodward Avenues
After the Second downtown loop, turn right and follow Woodward Avenue (north) to 12-mile Road
Turn left, making U-turn around center island and return south on Woodward Avenue, crossing 12-Mile
to park on Service Drive again to recheck instrumentation
This completes one circuit of the Detroit Traffic Test.
C. Return to BRL from 12-Mile Road and Woodward Avenue by following route:
After checking out instrumentation, drive west on 12-Mile Road to Greenfield Avenue
Left on Greenfield Avenue to Civic Center Drive
Right on Civic Center Drive to BRL
D. Estimated time scheduling:
Time
8:00 -
8:15
8:30
10:15 -
12:00 -
12:45 -
2:30 -
4:15 -
4:30 -
8:15
8:30
10:15
12:00
12:45
2:30
4:15
4:30
4:45
AT
(mln)
15
15
105
105
105
105
15
15
Vehicle preparation
BRL to 12-Mile and Woodward
First circuit
Second circuit
Lunch
Third circuit
Fourth circuit
Return to BRL
Prepare vehicle for overnight layover
E. Estimated Miles:
BRL to route and return 12
Each circuit 26.5 x 4 106
118 miles/8-hour shift.
Estimated total miles: 12 x 118 = 1416 miles.
7-3
-------
Cooling speed: Normal traffic speeds.
Stops required: As required in flow of traffic.
The duration of the Detroit Traffic Test is not fixed for
normal original equipment manufacturers' testing. For the purposes of
this program, a 12-day test duration was chosen. Each day of testing
was expected to provide approximately 118 test miles which, in turn, was
expected to yield a total of approximately 1416 test miles.
7.2.4 10- Stop Fade and Recovery
A portion of SAE J843a is called the fade sequence. This
test cycle is used as the first high- temperature operation of a friction
material. The test is used to simulate a vehicle making repeated heavy-
duty stops. The fade sequence is usually followed by a recovery sequence.
The test requirements are:
Fade:
Initial brake temperature: 150°F before first stop.
Stops required: 10»
Stop speed: 60-0 mph.
Stop deceleration: 15 fpsps (in normal driving gear).
Stop interval: 0.4 mile.
Cooling speed: 60 mph (accelerate at maximum speed).
Recovery:
Cooling speed: 40 mph.
Cooling interval: 1.0 mile.
Stops required: 12.
Stop speed: 30-0 mph.
Stop deceleration: 10 fpsps.
Lining temperatures are recorded before each fade stop and before each
recovery stop.
7.2.5 15-Stop Fade and Recovery
The 15-Stop Fade and Recovery is comparable to the 10-Stop
Fade and Recovery described earlier, except that an additional 5 stops
are made when the brakes are already very hot.
7.2.6 Reburnish
i-n H,e * < 1, Reburnlsh P0"ion of SAE J843a is essentially similar
to the Burnish portion except that only 35 stops are required.
7-4
-------
7.3 SELECTED VEHICLE DRIVING SCHEDULE
Although there are many acceptable original equipment manufacturers'
friction material tests to measure a specific condition or combination of
conditions, there is no one test which adequately matches normal driving
conditions which would be representative of all vehicles. Consequently,
it became necessary to devise a rational and meaningful vehicle test
driving schedule.
Table 7-2 lists the selected vehicle driving schedule for each ve-
hicle test configuration used in the program. A total of seven test
schedules was chosen and each was followed by a measurements procedure
(take emissions samples, measure wear, inspect systems, and replace worn
parts). The first three tests — Burnish, After-Burnish Baseline, and
Detroit Traffic — represent the low-temperature tests. The final four
tests — 10-Stop Fade, After-Fade Baseline, 15-Stop Fade, and Final
Baseline — represent the high-temperature tests.
7.3.1 Burnish
The initial test is the Burnish. The original equipment
and aftermarket linings mate and conform to the initial condition of the
rotor whether it is in its original configuration, as-used condition after
vehicle test 1, or its turned condition prior to vehicle test 3. It was
anticipated that the emissions would be different than those for worn-
in linings.
7.3.2 After-Burnish (A.B.) Baseline
The second test is After-Burnish (A.B.) Baseline. This
three days of Detroit Traffic Test was run at this time so that the other
Baselines run at the later times could be compared to the A.B. Baseline
for the amount and type of emissions.
7.3.3 Detroit Traffic Test
The third and longest test employed was the 12-day Detroit
Traffic Test. This test represents the low-temperature-wear or normal-
duty-wear tests. The results of this test could also be compared to the
A.B. Baseline Test.
The end of the Detroit Traffic Test was the end of the low-
temperature-wear testing.
7.3.4 IP-Stop Fade and Recovery
The 10-Stop Fade and Recovery was the fourth test sequence
and the start of the heavy-duty or high-temperature testing. During
this test, the front brakes experienced temperatures above 500°F, while
the rear brakes experienced temperatures above 350°F. The combination
of increased temperature and increased duty was expected to change the
amount and type of wear debris generated, as compared to the previous
low-duty tests.
7-5
-------
Table 7-2 - Vehicle Test Schedule
Test
Burnish
Measurements*
After Burnish
(A.B.) Baseline
Measurements
Detroit Traffic
(Modified)
Measurements
10-Stop Fade and Recovery
Reburnish
Measurements
After Fade
(A.F.) Baseline
Measurements
15-Stop Fade and Recovery
Reburnish
Measurements
Final
Baseline
Measurements
Estimated
Time
(Days)
2.0
1.5
3.0
—
1.5
12.0
1.5
1.5
1.0
1.5
3.0
_
1.5
1.0
1.0
1.5
3.0
-
1.5
Total
Time
(Days)
3.5
4.5
13.5
4.0
4.5
3.5
4.5
38.0
Estimated
Lining Loss
(Mils)
5
5
10
10
5
10
5
Purpose
Lining
Preparation
Base Line
Data
Low
Temperature
Wear
High
Temperature
Wear
Base Line
Data
Abusive
Wear
Base Line
Data
Take emissions samples, measure wear, inspect systems, and replace
worn parts.
7-6
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The Fade and Recovery were then followed by the Reburnish
sequence.
7.3.5 After-Fade (A.F.) Baseline
This fifth test sequence was identical to the second and
seventh test sequences (and similar to the third), but only the conditions
of the friction materials had changed. This test was expected to deter-
mine the permanent changes in the amount and type of wear debris generated
for friction materials taken through high-temperature and heavy-duty stops.
7.3.6 15-Stop Fade and Recovery
The sixth test sequence was the 15-Stop Fade (and Recovery)
in which the friction materials were taken to even higher temperatures
than for the 10-Stop Fade. The five additional stops performed after
the brakes were already hot produced temperatures above 575°F. This is
abusive braking, and rarely occurs. The emissions generated were expected
to be different again, as compared with the low-duty tests and the 10-
Stop Fade.
The Fade and Recovery were then followed by the Reburnish
sequence.
7.3.7 Final Baseline
The results of this seventh and last test sequence can be
compared with the results of the identical second and fifth test sequences.
This test concluded the determination of the effects that high-temperature
and heavy-duty tests have on brake emissions.
7-7
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SECTION 8
SAMPLING AND ANALYTICAL PROCEDURES
8.1 RATIONALE BASED ON COLLECTOR DESIGNS
8.1.1 Particulate Emissions Collection
During the braking process, particulate emissions are gen-
erated by the rubbing action of the friction materials and the rotors.
The OEM brake configurations (left wheels of test vehicle) release emis-
sions which reside in either of two areas depending on the brake type
(Table 8-1),. The disc brake releases much of the emissions to the atmos-
phere while a small amount remains in the brake. The drum brake releases
a lesser amount to the atmosphere and retains sizeable portions on the
drum rubbing surface and on the brake parts. The brake emissions collec-
tors perform two functions not encountered in normal brake operation:
collect all the debris generated and fractionate the debris. Table 8-2
summarizes the particulate emissions samples produced.
8.1.2 Gaseous Emissions Collection
During the braking process, gaseous emissions are also
generated by the heat associated with the rubbing action of the friction
materials and the rotors. The OEM brake configurations release gaseous
emissions which again reside in either of two areas. Most of the gaseous
emissions are released into the atmosphere; some of the high molecular
weight materials distill from the hot surfaces and condense on the cooler
brake parts. The emission transfer lines used in conjunction with the
collectors therefore were heated so that almost all gaseous emissions
could be transferred to the gas collection traps.
8.2 PARTICULATE EMISSIONS REMOVAL FROM COLLECTORS
8.2.1 Collection of Particulate Emissions
A detailed step-by-step sequence was prepared for the col-
lection of brake and clutch emissions. This information is included
as Appendix C. The weights of each sample collected are reported in
Section 9 under Vehicle Test Results.
8.2.2 Disc Brake Samples
In all cases, three samples were obtained from the right
front disc brake collector: sump sample (including debris in rivet holes,
on lining surfaces, and inside caliper piston), wear debris which remains
in the brake; surfaces sample (including all other debris remaining in
the brake collector); and the airborne sample (debris collected on the
8-1
-------
Table 8-1 - Comparison of Disc Brake Versus Drum Brake Operating
Conditions
Parameter
Type of system
Air flow
Emissions
Third-body
abrasive wear
Disc
Open
High
Relatively
few trapped
Relatively
none
Drum
Closed
Low
Much trapped
in surfaces
and in sump
Some
P-8 2-99-3
Table 8-2 - Samples Produced by Brake Emissions Collection
Sample
Sump
Surfaces
Airborne
Disc Brake
Trapped debris* - includes
that in rivet holes, on
pads and in caliper piston
Accumulated on shroud -
normally road dropout
Airborne samples collected
on filters
Drum Brake
Trapped debris* - includes
that in rivet holes, on
linings , and on drum surf ace+
+Provides third-body wear
Accumulated on brake surfaces*
Airborne samples collected on
filters
*Normally not completely released during brake operation. (This may be a
"controllable" material which could be disposed of properly).
8-2
-------
8.0y and 0.2y Nuclepore filter train). The contract did not require Bendix
Research Laboratories to sample the left front disc brake; however, some
samples were taken so that it would be possible to assess the quantity of
material remaining in an OEM configuration disc brake. These data were
prepared for Section 9.
8.2.3 Drum Brake Samples
In all cases, three samples were obtained from the right
rear drum brake collector: sump sample (including debris in rivet holes,
on lining surfaces, and on drum rubbing surface), wear debris which remains
in the brake; surfaces sample (including all other debris remaining in
the brake collector and on the brake surfaces); and the airborne sample
(debris collected on 8.Op and 0.2p Nuclepore filter train). The contract
required that selected left rear drum brake samples be taken in order to
assess the quantity of material remaining in an OEM configuration drum
brake. These data were prepared for Section 9.
8.2.4 Clutch Samples
Since the airborne samples taken from the clutch for vehicle
test l were extremely small compared to the corresponding airborne samples
from the brakes-, it was decided to accumulate the entire sump and surfaces
samples for all three vehicle tests. These data were prepared for Sec-
tion 9.
8.2.5 Improved Friction Material Weighing Procedure
The original equipment drum brake linings and disc brake
pads were riveted to their corresponding brake shoes. The weight of the
metallic shoe placed the combined weights in excess of 400 gm; the weight
could then be recorded to the nearest 0.1 gm. The anticipated weight
differences of approximately 0.5 gm would have had less than desired
accuracy. By removing the rivets, the weights of the friction materials
alone could be determined. Since all friction material weights were
less than 200 gins in this condition, weighing on an analytical balance
was possible. After the friction materials were dried in a vacuum oven
at 90°C, the weights were recorded to the nearest 0.01 gm, giving the
desired accuracy. The linings were then refastened to the shoes by flat
head nuts and bolts for vehicle installation and testing.
8.3 ANALYTICAL PROBLEM DEFINITION
8.3.1 Composition of Wear Debris
The brake converts the kinetic energy of the moving vehicle
into heat, absorbs the heat, and eventually dissipates it to the atmos-
phere* As a result of the energy conversion at the stator-rotor inter-
face, the compositions and microstructures of the brake lining and rotor
surfaces are altered.
8-3
-------
At low service temperatures, the phenolic resin and organic
friction modifiers in the friction material undergo ploughing and mechani-
cal damage before they convert on the surface to compositions with slightly
higher carbon/oxygen ratios. At somewhat higher use temperatures, the
resin and organic friction modifiers convert to carbon more readily, and
this in turn oxidizes to carbon dioxide. At the same time, the asbestos,
converted asbestos, and other converted materials wear away more rapidly
because of the reduced binder strength and volume at the surface. At
still higher temperatures, the asbestos converts from its fibrous form
to an olivine powder having little or no reinforcing value. When heat
is generated at the sliding interface much faster than it can be dissipated,
the temperature rises and reaches a point where the lining or pad compon-
ents decompose, oxidize, or melt. The region near the sliding surface of
the lining containing these reacted components is called the frictional
heat affected layer (FHAL).
At low service temperatures, the surface asperities of the
rotor are mechanically worked and the surface becomes essentially free
of graphite. Also, the cementite plates in the surface layer are broken
up and distributed as fine particles in a ferrite matrix. When the sur-
face is subjected to very high temperatures, martensite forms at the
rubbing surface, with an accompanying increase in surface hardness.
Consequently, the thermal and mechanical forces which act
at the friction couple interface produce a complex chemically and physi-
cally altered microstructure which cannot be accurately described for the
resultant wear debris. Figure 8-1 shows the thermogravimetric analysis
of typical rear drum brake wear debris. Table 8-3 gives an estimate of
the chemical composition of wear debris.
8.3.2 Analytical Methods for Asbestos and Their Rationale
As pointed out earlier, asbestos is a complex inorganic
material with the approximate composition formula:
Mg3 (S105) (OH)4 or 3MgO • 2Si02 • 2H20
The basic unit has a fibril form. Asbestos is readily identified when
alone or in simple mixtures at high concentrations by the following ana-
lytical methods:
X-Ray diffraction
Thermal methods
Microscopy
Infrared analysis
8-4
-------
100
70
60
50 •
SAMPLE:
1969 VEHICLE
4641/H3133FROM
RIGHT REAR DRUM
40,000 MILES
SIZE.
oo
X-AXIS
TEMP. SCALE.
SHIFT 0
100
inch
inch
~2% MINERAL
DEHYDROXYLATION
Y-AXIS
SCALE 1-0 ma.
inch
(SCALE SETTING X 2)
RUN NO..
DATE 12-14-71
OPERATOR,
RDS
20
HEATING RATE.
ATM OXYGEN 40 CC/RATE
TIME CONSTANT.
100 200 300 400 500 600
TEMPERATURE °C
700
800
900
1000
Figure 8-1 - Thermal Analysis of Wear Debris
-------
Table 8-3 - Estimated Chemical Composition Characteristics
• of Wear Debris
Description
Low Molecular Weight
Degradation Products
Polymeric Components
Carbonaceous Material
Inorganics :
Mineral
Olivine
Oxides (from Lining)
Fe20 (from Rotor)
Asbestos
Percent
2-10 \
12-20 >
1-5 J
VLO-30
^20-40
0-10
5-15
<1
20-30
70-80
However, in complex mixtures, or at very low concentrations, the analysis
for asbestos is very difficult. In brake wear debris, the problem is
compounded because the reaction products of asbestos, forsterite and
olivine, have similar elemental ratios and similar X-ray diffraction pat-
terns. The only sensitive method which can be used is microscopy. In
extremely low concentrations, asbestos is identifiable in the electron
microscope by its physical shape (tubular fibril), which is distinguish-
able from that of other fibers and particles.
8.3.3 Microscopy Methods for Asbestos
At the beginning of this program, there were one optical
and three electron microscopy methods for the determination of asbestos
content. The optical microscopy method was established by the U.S. Public
Health Service with the Asbestos Textile Industry(8-1)* to monitor ambient
air quality for large asbestos fibers in areas of high concentration.
In this method, an asbestos content with more than 90 percent fibers col-
lected on a membrane filter was examined at 400 or 430 diameters magni-
fication with phase contrast optics. The phase contrast rendered the
background filter transparent and enhanced the viewing of the fibers.
Only fibers greater than 0.5u in diameter and 5.0y in length were detected
and reported. No fiber size degradation took place in this analysis.
Two electron microscopy methods (developed by Battelle
Columbus Laboratories(8~2) and Mt. Sinai School of Medicine^8"3)) existed
rv
References appear at the end of this section.
8-6
-------
at the start of the program while the third was just being introduced
(University of California, School of Public Health(8-4)). These methods
are compared in Table 8-4. The Battelle and Mt. Sinai methods are char-
acterized by asbestos fiber size degradation to produce more fibrils.
This size degradation was not desirable for this program, as one of the
objectives was to ascertain the size distribution of the asbestos fibers
in the brake emissions. On the other hand, the University of California
method was desirable because of particle size preservation. However, the
magnification range was found to be low, making it difficult to see the
smaller asbestos fibers and fibrils found in brake wear debris.
8.4 BENDIX ANALYTICAL METHOD FOR ANALYSIS OF ASBESTOS IN BRAKE EMISSIONS
8.4.1 Criteria and Flow Chart
Three important criteria had to be met by the analytical
method used: the very small portion of brake debris used had to be re-
presentative of the much larger sample collected; the analytical steps
could not degrade the particle size distribution of the asbestos fibers
obtained; and the results obtained must be indicative of the actual as-
bestos content of the sample. These criteria were met by the analytical
scheme outlined in Figure 8-2.
8.4.2 Analysis of Brake Emissions
A detailed step-by-step sequence was prepared for the ana-
lysis of brake emissions. This information is included as Appendix D,
The asbestos content of each sample analyzed is reported in Section 9
under Vehicle Test Results.
8.4.3 Representative Sampling and Low Temperature Ashing (LTA)
After desiccating the samples to remove adsorbed water and
weighing for material balance purposes, two representative sampling pro-
cedures were used. In the first sampling, 10 fractions, each approximately
2 to 5 mg, were used to accumulate approximately 20 to 50 mg of wear de-
bris (Figure 8-3). If the total sample weight was less than 100 mg, the
entire sample was used. The large amount of carbonaceous material was
responsible for the fluffy appearance of the wear debris. Figure 8-4
shows a scanning electron photomicrograph of a group of several fibers
greater than 50 microns. Their ends were not visible and their exact
length could only be obtained by LTA or by destroying the wear debris
particle which, in turn, might have reduced fiber length. The LTA process
is described in Figure 8-5.
8-7
-------
oo
00
Table 8-4 - Transmission Electron Microscopy Methods
Magnification
Size Degradation
Size Distribution
Concentration Used
Minimum Detectable Limit
Size Detection (p)
Minimum
Maximum
Statistics
Customer
BATTELLE
40.000X
Yes
Changed Completely
Yes
'x-0. 000001%
0.03 X 0.09
0.20 X 10
20 Grid Openings
(vLOO Fibrils)
EPA
MT. SINAI
42.000X
Partial
Changed Slightly
No
0.03 X 0.09
0.20 X 10
6 Grids X 2 Openings/Grid
(VLO-100 Fibrils)
Asbestos Workers Union
U OF CALIFORNIA
3.000X
No
Unchanged
No
0.01%
0.05 X 1.5
0.50 X 40
Not Known
Asbestos Workers Union
-------
SUMP
SAMPLE
SURFACES
SAMPLE
(WEIGHED)
AIRBORNE SAMPLES
0.2ju FILTER S.Oju FILTER
COMBINE
n
di
01
T
(SAME AS FOR
SURFACES SAMPLE)
WEIGH REPRESENTATIVE
FRACTION
(SAME AS FOR
SURFACES SAMPLE)
LOW TEMPERATURE
ASH (LTA)
WEIGH REPRESENTATIVE
FRACTION
DISTRIBUTE ON
0.2juNUCLEPORE
FILTER
DIVIDE
OPTICAL MICROSCOPY:
(GLASS SLIDE MOUNT)
I
COUNT
(400X PHASE CONTRAST)
ELECTRON MICROSCOPY:
(CARBON SANDWICH)
COUNT
(22,OOOX)
T
RESULTS
Figure 8-2 - Flow Chart for Particulates Analyses
8-9
-------
•H
Figure 8-3 - Representative Sampling for Analysis
Figure 8-4 - Wear Debris Collected on 8y Nuclepore Filter
8-10
-------
RF PRODUCES ATOMIC OXYGEN
WHICH REACTS WITH CARBONACEOUS
MATERIAL TO FORM GASES AND
VAPORS WHICH ARE CONTINUOUSLY
EXHAUSTED BY VACUUM
PYREX REACTION
CHAMBER
t
[M
s:
a.
OXYGEN
ATOMIC
OXYGEN
TO
VACUUM
// GLASS
SAMPLE BOAT'
•SAMPLE
Figure 8-5 - Low Temperature Ashing
-------
A series of tests was run to determine the organic content
removal by the oxygen plasma on several types of samples. The removal
rate varied according to sample type and state of subdivision:
Removal Rate
Sample mg/hr
Carbon Rod
Small Piece (Large Area) 31
Large Piece (Small Area) 21
Phenolic Resin >15
Filter Paper 40
Wear Debris 4
Carbon rod was the standard recommended by the instrument manufacturer
who claimed a removal rate of 90 mg/hr. This rate was never obtained.
For the carbon rod, the phenolic resin, and the filter paper, the removal
rate was dependent on surface area exposed to the plasma. The wear de-
bris, in spite of a large surface area, exhibited very low removal rates.
Consequently, long periods were required for removal.
The LTA process removed 15 to 30 percent of the sample
weight, which, in turn, effectively increased the concentration of the
asbestos content for counting purposes, as performed later. Figure 8-6
shows LTA-treated wear debris as distributed on a 0.8y Nuclepore filter.
The large groups of asbestos fibers shown in Figures 8-4 and 8-6 are not
typical; in almost all cases single fibers and fibrils exist and the
larger groups are shown for illustrative purposes only.
The second representative sample step is described in
Sequence 7B of Appendix D. The appropriate LTA sample was taken in the
following manner: approximately 10 fractions of approximately 0.05 mg
each (material held on tip of fine spatula) were placed in a tiny platinum
boat on a five-place analytical balance until 0.55 ± 0.05 mg,weighed to
the nearest 0.01 mg, was obtained. This material was then suspended in
a liquid and distributed onto a 0.2y Nuclepore filter as outlined in
Sequence 7B of Appendix D and shown in Figure 8-7- The manner in which
the value of 0.55 + 0.05 mg was obtained is described in the following
section. .
8.4.4 Sample Distribution for Microscopy
The amount of material to be examined by microscopy was
arrived at by trial-and-error. A 47 mm filter loading of 10.0 mg was
too great, as the smaller particles were not seen or separated from larger
particles. The sample shown in Figure 8-6 was prepared with 7.0 mg load-
ing and several areas of severe crowding or multi-layers of particles
were seen. A further series of samples was made with filter loadings
8-12
-------
(a) LTA Wear Debris on 0.8p Nuclepore Filter - 500X
(b) Asbestos Particle Located in LTA Wear Debris - 5000X
Figure 8-6 - SEM Photomicrographs of LTA Wear Debris Samples
3-13
-------
Figure 8-7 - Uniform Sample Distribution onto Filter
down to 1.0 mg. At the 1.0 mg level, the particles were sufficiently
spread out to permit viewing of each particle by electron microscopy.
However, to achieve consistently stable films, a further study was carried
out (Appendix E) and it was found that good electron microscopy results
could only be obtained by implementing the following changes in the ana-
lytical procedure:
• Use of a smaller grid opening (400 mesh screens) to
give good support and higher thermal conductivity.
o Lower loading on filter (0.50 to 0.60 mg) for more
uniform distribution.
8-14
-------
• A,second layer of carbon to effectively "sandwich" the
wear debris for both strength of sample and thermal
conductivity improvements.
In early tests, wear debris was collected on both Millipore
and Nuclepore filters. The smaller particles entered into the fibrous
network of the Millipore filters as shown by scanning electron microscopy.
On the other hand, the Nuclepore membranes readily exhibited the collected
wear debris on a relatively flat surface. To avoid future qualitative
and quantitative problems with fiber identification, Nuclepore filters
were therefore selected for all further work in this program.
8.4.5 Selected Microscopy Methods
8.4.5.1 Initial Studies and Rationale
r
A survey of the available analyses for asbestos
particles in friction material wear debris or in ambient air samples
was made. All methods found were satisfactory for total asbestos. All
methods found were unsatisfactory for asbestos particle size distribution,
as they all involved a particle size reduction step for transmission elec-
tron microscopy observation. Fiber bundles similar to those shown in
Figure 8-6 did not permit sufficient electron beam penetration and good
images could not be obtained for qualitative and quantitative observation
when fibril ends were not present.
In the very early tests, wear debris from a sample
dynamometer was collected on the filter train of the 8.Op and 0.2y Nucle-
pore filters. Both filters were examined by a combination of optical and
transmission electron microscopy. The following observations were made:
• When the total airborne sample was small, the particulate
distribution between the filters was almost even. As the
total sample (sum of debris on both filters) became larger,
the larger amount of debris remained on the 8.0y filter.
In effect, it became a finer filter and less material passed
to the 0.2y filter.
« The size distribution on the 8.0y filter varied over a larger
range; the material on the 0.2y filter was finer and more
uniform in size.
« Fibers were found on both filters; fibers up to 2.0y diameter
and 50y long were located on the 8.0y filter, and up to
0.9y diameter and 3.6y long on the 0.2y filter. The electron
beam could not penetrate the thicker fibers.
• Although many nonfibrous particles were checked for crystal-
linity by electron diffraction, very little crystallinity
was found.
8-15
-------
Additional particulate analyses were carried out
for the airborne samples collected from the inertia dynamometer tests
described in Section 6. The filters were examined as collected , without
any sample redistribution onto a single filter. The following observations
were made:
o Asbestos fibers longer than 20 microns were obtained.
o Very fine fibrils were extremely difficult to detect in
"as-collected" airborne wear debris.
Based on the above studies, it was deemed neces-
sary to employ two magnifications. To detect fibers greater than 5y,
a magnification in the range 400 to 1000 diameters, was required. To
detect the finer fibers and the ultimate fibrils, a magnification in
the range 10,000 to 40,000 diameters was required.
The following optical plus transmission electron
microscopy magnifications were selected:
Fibers Detected (p)
Minimum Maximum
d x 1 d x 1
Transmission Electron
at 22.000X 0.03 x 0.10 0.50 x 35
Optical (Phase Contrast)
at 400X 0.50 x 1.50 10 x 100
8.4.5.2 Optical Microscopy Analysis for Asbestos
The U.S. Public Health Service procedure outlined
in Section 8.3.3 was modified for this program. The procedure(°~1)
called for Millipore filters and the fluid used for phase contrast had
a refractive index of 1.460. In the Bendix procedure with Nuclepore
Filters, a fluid matching one of the refractive indices of Nuclepore
filters at 1.585 was substituted.
The procedure used is described in Sequence 8H
of Appendix D. Figure 8-8 shows the microscopist behind the Reichert
Zetopan as equipped with Heine phase contrast optics at 400 diameters.
A typical photomicrograph (Figure 8-9) shows fiber among the remaining
wear debris.
8.4.5.3 Transmission Electron Microscopy Analysis
for Asbestos
The University of California School of Public
Health procedure, also described in Section 8.3.3, was modified for this
program. A magnification of 22,000 diameters was used instead of the
prescribed 3000 diameters because of the difficulty in seeing fibers below
O.ly in diameter.
8-16
-------
Figure 8-8 - Phase Contrast Optical Microscopy at 400X
' •*'" * .
Figure 8-9 - Phase-Contrast Photomicrograph of Wear Debris - 400X
8-17
-------
The procedure used is described in Sequence 8B
of Appendix D. Figure 8-10 shows the Hitachi Type HU-125E transmission
electron microscope used in this program. A typical photomicrograph
(Figure 8-11) shows asbestos fiber among the remaining wear debris.
8.4.6 Calculations From Microscopy Results
8.4.6.1 Rationale and Microscopy Count Sheet
The ultimate asbestos fibril has been found to
be circular in cross section(8-5). When the wear debris was spread thinly
over the flat Nuclepore filter membranes, each fiber remained flat when
viewed in the microscope, so that its projected diameter and length
Figure 8-10 - Transmission Electron Microscope
8-18
-------
could be measured. The volume of each asbestos fiber was readily deter-
mined from the following formula:
„ TTd
V 4 x
where
V = volume of material
d = projected diameter measured
£ = length measured
When two or more fibrils make up the larger fiber bundles, a larger-than-
actual projected diameter results. Even fibers with elliptical cross
section were assumed to lay such that their largest diameter was parallel
to the filter. In all cases, the volume- calculated from the projected
diameter and length was thus on the high side.
For each .fibril or fiber found, it was necessary to determine its
dimensions and calculate the volume of asbestos found. Because of the
large number of fibers, this procedure became tedious. To simplify fiber
sizing, a Microscopy Count Sheet was developed .(Figure 8-12). The cross-
hatched areas are the boxes which did not follow the definition of a
fiber: the length was required to be three or more times greater than
the diameter. Each fiber found by the appropriate microscopy method was
classified into the proper box containing the projected diameter and
length of the fiber in question. A typical microscopy count for a sample
generated in this program is superimposed on Figure 8-12.
8.4.6.2 Sample Calculation
A typical calculation is carried out in the following manner.
For each box, an average volume is calculated from,the formula:
where
V = average volume for box
~2 2
d = average of diameter for box
Si = average length for box
8-19
-------
Figure 8-11 - Asbestos Fiber in Brake Emission
These values are given in Figure 8-13. Then it is necessary to multiply
the number of fibers given in each box in'Figure 8-12 by the volume given
for the corresponding box as shown in Figure 8-13.
The typical microscopy count shown in Figure 8-12
is used to calculate asbestos content in the following manner. The fibers
of each group are totaled as shown in Table 8-5. The total number of
fibers per group (n) is then multiplied by the average volume per group
(V) to obtain the product (n x V). All products are then totalled to
arrive at the total volume of asbestos detected.
Since only a fraction of the total area is ac-
tually scanned, the volume observed must be normalized to the entire area
containing wear debris:
Total Fiber
Volume (by EM or OM)
= Volume obtained (cc) x
Total Area of Filter
(No. of Fields Counted) x (Area of a Field)
I (n x V) x
990 mm'
IF x (Area of Field)
-------
MICROSCOPY COUNT SHEET
Vehicle Test: /
Schedule: A-0-
Collector:
Sample:
Date: 7-2V-72.
Total Sample Weight: /86~./
_mg
LTA Weights (I/F): 38-8 I 3/.2- mg
Count Weight: Q .£2.
Comments:
•x
o
o
o
(N
(N
g
o
0.08
0.08
/
0.25
0.25
/
0.50
/
Illl
(D
/rrtf
iff
EM Field Size:
3.0 x 3. Op
No. of Fields:
ZOO
FIBER LENGTH (u)
Illlll
7-2 5- 7Z.
Date Counted:
OM Field Size: |8_ x 88_H
No. of Fields:
##«*•»#>#
Microscopist:
Figure 8-12 - Microscopy Count Sheet
8-21
-------
FIBER VOLUME CALCULATION
o
o
o
O)
(N
EM Field Size
3.0 -x 3.On
No. of Fields
o
o
FIBER LENGTH (u)
3.0
0,982.
3.0
3.19
fZ.8
33.2.
(e.3,0
10
7,30
76-7
35
A3,
5-5,8
270
Z.3,3
95,0
JC-S
1380
2,89
39,3
/190
Z.3Z
x.o3
mo?
Date Counted:
OM Field Size:
No. of Fields:
x 88U
Microscopist:
Figure 8-13 - Fiber Volume Calculations
8-22
-------
**** ASBESTOS ANALYTICAL RESULTS ****
VEHICLE TEST: 1
SCHEDULE: A. B. BASELINE
COLLECTOR: RIGHT PEAR BRAKE
SAMPLE: SUMP
10F 0
0.464E-16
0.681E-16
0.100E-15
0.1476-15
0.215E-15
0.316E-15
0.464E-15
0.681E-15
O.LOOE-14
0. 1476-14
0.215E-14
0.316E-14
0.464E-14
0.6SIE-14
0. 100E-13
0.147E-13
0.2L5E-13
0.316E-13
0.464E-13
0.6B1E-13
0.1006-12
0.147E-12
0.215F-12
0.31AE-12
0. 4646-12
0.681E-12
0.1006-11
0.147E-1 1
0.2156-11
0.3166-11
0.464E-11
0. 6816-11
0. IOOE-10
0.147E-10
0.215E-10
0.316E-10
0.4646-10
0.6816-10
0. IOOE-09
0.1476-09
0.2156-09
0.3166-09
0.4646-09
0.681E-09
0.100E-08
0.0
0.0
0.0
0.0
0.550E
0.0
0.0
0.1656
0.0
0.275E
0.0
0.0
0.660E
0.0
0.0
O.llOE
0.0
0.495E
0.0
0.0
0.5bOF
0.0
0.0
0.0
0.0
0.0
0.575E
0.0
0.0
0.0
0.575fi
0.0
0.0
0.447F
0.0
0.639E
0.6i9E
0.0
O.P56F
0.0
0.0
0.0
0.0
0.0
0.0
06
07
07
07
07
07
06
04
04
04
03
03
04
DATE: 7-21-72
NO.: 104
LTA(I)= 0.38806-01
LTA(F)= 0.3120F-01
ASBESTOS PFPCENT =
10C 4 10C 5 10^ 6
EM SUB THTAL = 0.5683E-06
flM SUB TOTAL = 0.8148F-06
TOTAL = 0.1383E-05
COUNT WEIGHT = 0.62006-03
1 1 1
1 1 1
1 1 1
1 1 1
1 1 1
1 1 1
I 1 1
1 1 1
1 1 1
1 1 1
1 1 1
1 1 1
1 I 1
1 1 1
1 1 1
1 1 1
1 1 - 1
1 1 1
1 1 1
1 1 1
1 1 1
1 1 1
1 1 1
1 1 1
II 1
1 1 1
1 1 1
1 1 1
1 1 1
1 1 1
1 1 1
1 1 1
10F 1
101= 5 irc r.
NJ
Figure 8-14 - Computer Printout of Asbestos Analytical Results
-------
Table 8-5 - Sample Calculation
ELECTRON MICROSCOPY
Fiber
Number
(n)
1
3
5
12
1
1
9
1
Fiber _
x Volume = n x V
(V x 10~15 cc) (x 10~15 cc)
0.20 0.20
0.50 1.50
1.31 6.55
3.50 42.0
11.3 11.3
10.2 10.2
27.1 243.0
88.0 88.0
E n x ? = 402.7
Total Volume
E
(No.
402.
= 202
(n x V) x (Area of filter)
of fields) x (Area of field)
7 x 10~15 990 x 106 y2
200 ^ 3 x 3 y2
x 10~9 cc
OPTICAL
Fiber
Number
(n)
9
9
2
5
1
1
4
MICROSCOPY
Fiber _
x Volume = n x V
(V x 10~12 cc) (x 10~12 cc)
0.982 8.92
3.19 28.7
13.5 27.0
12.8 64.0
29.4 29.4
33.2 33.2
76.4 305.0
E n x V = 496.22
Total VolumeOM
E
(No.
496.
= 316
(n x V) x (Area of filter)
of fields) x (Area of field)
2 x 10~12 990 x 106 y2
200 * 88x88y2
x 10~9 cc
n
66-ZB-d
Total Volume
(Total Volume).,.. + (Total Volume)..,
Jin UM.
(202 + 316) 10~9 cc = 518 x 10~9 cc
Total Weight
518 x 10~9 x 2.50 ^ x 1000 SB.
cc gm
1.33 x 10~3 mg
Asbestos Percent
0.00133 312
-OT x 388 x
8-24
-------
For the electron microscopy analyses at 22,000 diameters, the area of a
field was 3 x 3 y2. por the optical microscopy analyses at 400 diameters,
the area of a field was 88 x 88 y2. in electron microscopy analysis,
402.7 x 10~15 cc was found for 200 fields:
v ^ - x 9 x 1 cc
Volume (by EM) (2Q()) x (3 x 3 y2)
202 x 10~9 cc
Total Fiber Specific 0 c, gm _., T7 . , ,, „..,
„ n t, „„.,. x „ . 2.56 •6— = Fiber Weight (by EM)
Volume (by EM) Gravity cc & \ j '
202 x 10~9 cc x 2.56 -SB = 0.00052 mg
cc
Combined total for all •_ „„,.,,,
, „ e , = 0.00133 mg.
asbestos found
This amount of asbestos calculated is for debris which had been slightly
concentrated in the LTA process. Thus the asbestos percent, as related
to the original material, is obtained by the following expression:
Asbestos Total Asbestos Found . . F inr.
_ = „ . , x LTA Ratio •=• x 100
Percent Count Weight I
For the example given in Figure 8-12, the percent asbestos for the sump
sample of the right rear brake collected for the A.B. Baseline Schedule
of vehicle test 1 is found:
Asbestos 0.00133 31.2 ...... _ ..-,_
Percent = 0762— X 3O X 10° = °'173
8-25
-------
8.4.6.3 Computerization of Calculations and
Particle Size Distribution
The calculation of asbestos content was lengthy
and thus susceptible to computational errors. Moreover, over 150 such
calculations were anticipated for the program. A computer program was
therefore developed in conjunction with the Count Sheet given in Fig-
ure 8-12. The uppermost horizontal row and the extreme left vertical
column of markers are used to identify the box with its corresponding
volume. The circled number is the number of fibers found which corres-
pond to that volume. Unlike the manual calculation, grouping of boxes
in threes is not required and for this reason the computer calculation
is slightly different and slightly more accurate than the manual
calculation.
The computer program is given in Appendix F.
Figure 8-14 shows the computer printout for the sample calculation given
in the previous section. The computer printout gives the asbestos
percent = 0.179 percent, which compares with the manual calculation of
asbestos percent = 0.173 percent.
8.4.7 Possible Sources of Error
The possible sources of error for the sampling and analysis
of particulate wear debris are listed in Table 8-6.
The possible sources of error associated with sample pro-
cessing were minimized through the use of statistical methods. For sample
selection, two stages of representative sampling took place: weighing
prior to sample low temperature ashing, and weighing for distribution
onto the filter. Uniformity of sample distribution was checked by low
power optical microscope observation immediately after distribution.
This was further checked by the microscopy results as shown in Figure 8-12.
Just under the number of fields reported for the electron microscopy re-
sults, the notation used shows 15 fibers found in 100 fields examined
on 2 grids from one side of the filter, while 18 fibers were found for
100 fields examined on 2 grids from the other half on the filter. Also,
for the optical microscopy results, 17 fibers were found in 100 fields
on a sample taken from one side of the filter, while the other side yielded
13 fibers. These distributions were typical.
As indicated in Appendix E, a series of tests was run to
insure good samples for electron microscopy. Membrane shrinkage did not
occur and membrane curling was minimized. No observations in the elec-
tron microscope were taken near membrane edges. The sample distribution
was finalized after more than ten different sample weights were examined
and then several different samples at the same sample weight gave repro-
ducible films in terms of stability and counting.
8-26
-------
Table 8-6 - Possible Sources of Error
SAMPLE PROCESSING
Low Temperature Ashing
Sample Selection
Extent of Ashing
Weighing
Sample Distribution
Sample Selection (From Vial)
Sample Weighing
Characteristics of Sample and Variations in
Size Distribution
Loss through Filter
Filter/Funnel Interface Effects
Sample Handling
Air-Borne Dust Contamination
Static Electricity
Air Currents
MICROSCOPIC METHODS
Sample Preparation
Sample Identification
Sample Redistribution during Cutting
Membrane Stretching, Shrinkage, or Curling
Sample Counting
Depth of Field
Width x Length Estimates
Large Fiber Contributions
Fiber Identifications (Asbestos Versus Olivine)
Magnification Variations
Statistics
8-27
-------
Perhaps the largest sources of error occur in the sample
counting procedure, for the following reasons:
• Width and length estimates of fibers and their
insertion into the proper box in Figure 8-12
(a borderline diameter such as 0.05 y which is
between lines 12 and 13 gives an average volume
difference of approximately 3) .
o Fiber identification difficulty, especially in
optical microscopy (asbestos or olivine).
• Number of fibers found and their statistics.
These errors were minimized by counting a large number of
fibers and/or fields, whichever came first. The target for fiber count-
ing was 100 fibers in 100 fields in both electron and optical microscopy.
This target was rarely obtained because of the very low content of as-
bestos present in the sample. A maximum number of fields to be counted
for low fiber concentrations was also established (200 EM fields and
300 OM fields), to avoid unnecessary delays for very low concentrations.
The largest effect found on the asbestos analysis was the
occurrence of a large fiber. Its volume contribution significantly in-
creased the contribution, in either microscopy method, by 100-200 percent.
This could give up to a 50 percent change in the final calculation. If
additional fields were counted or a replicate analysis made, a comparable
fiber was usually not found. The large fiber was thus considered an
"outlier" and was not used in the calculations. In some instances, more
than one large fiber was found in a sample. Replicate analyses did not
yield similar fibers and the asbestos emissions result was significantly
different as shown in Table 8-7 for the following sample: Vehicle Test
1, Detroit Traffic Schedule, right front brake, sump sample (Example 1).
The precision in the asbestos analytical results can be
estimated by considering the replication data given in Table 8-7. The
percent deviations range from 0 to 79 percent; the average is +27 percent.
On the other hand, Figure 8-15 shows the variation of the maximum devia-
tion (given in Table 8-7) with the asbestos percent found. The data
show that the maximum deviation for results with asbestos contents above
approximately 0.10 percent have a maximum envelope at approximately 20
percent, with averages at 12-15 percent. The maximum deviation increases
for asbestos content below 0.10 percent, where errors for the small
amounts of asbestos emissions become less significant.
8.5 ANALYSIS OF GASEOUS EMISSIONS
8.5.1 Method of Analysis
j*a< „ A + 8aS collection system (described in Section 5.4) was
designed to collect and separate condensable and noncondensable gases
T I' BeCSUSe °f the hlgh vaP°r Pressure of the noncon-
gases ln the activated-charcoal traps, storage took place at
8-28
-------
Table 8-7 - Extent of Error in Asbestos Emissions Analytical Results
EXAMPLE
NUMBER
1
3
4
6
7
8
9
10
SAMPLE
Vehicle Test 1
Detroit Traffic
Right Front Brake
Sump Sample
Vehicle Test 1
Detroit Traffic
Right Front Brake
Surfaces
Vehicle Test 1
Detroit Traffic
Right Front Brake
Airborne
Vehicle Test 1
A.B. Baseline
Right Rear Brake
Airborne
Vehicle Test 3
Detroit Traffic
Right Front Brake
Surfaces
Vehicle Test 3
Detroit Traffic
Right Rear Brake
Surfaces
Vehicle Test 3
Final Baseline
Right Front Brake
Surfaces
Vehicle Test 3
Final Baseline
Right Rear Brake
Sump
Vehicle Test 3
Final Baseline
Right Rear Brake
Surfaces :
Cumulative for
Vehicle Tests
1, 2, and 3
Clutch
Surfaces
ASBESTOS
PERCENT
0.247*
0.631
0.186
0.137*
0.085
0.091
0.116
0.052*
0.025
0.085
0.068
0.432*
0.554
0.013*
0.034
0.057*
0.045
0.087*
0.061
0.512*
0.386
0.511
0.237*
r
0.047
0.047
AVERAGE
0.355
0.107
0.056
0.493
0.023
0.051
0.074
0.470
0.228
0.047
MAXIMUM
DEVIATION
0.276
0.022
0.031
0.061
0.011
0.006
0.013
0.084
0.010
0.000
PERCENT
DEVIATION
+79%
+21%
+55%
+21%
+48%
+12%
+18%
+18%
+ 5%
0
*Result reported in Tables 9-16, 9-17, and 9-18.
8-29
-------
100H
80-
O
LU
O
5
i
60-
40-
20
MAXIMUM
AVERAGE
T"
0.10
-1 -1 1
0.20 0.30 0.40
ASBESTOS PERCENT FOUND
0.50
0.60
Figure 8-15 - Variation of Maximum Deviation of Asbestos Analytical
Results with Asbestos Percent Found
-70°C with solid carbon dioxide packed around the traps. The analytical
procedures are given in Appendix D. The primary method of analysis was
gas chromatography for both the noncondensable and condensable gases.
8.5.2 Gas Handling System
The gas handling system used for the gas analysis is shown
in Figure 8-16. The system included various sections designed to perform
the following tasks:
• Gas inlet and fraction traps - used to separate air
from the gases of interest.
• Toepler pump and gas buret - used to transfer the gases
and measure their volume.
• Gas chromatograph transfer U-tube - used with gas buret
and Toepler pump to inject a sample into the gas
chromatograph (Figure 8-17).
8-30
-------
CALIBRATION GAS
STORAGE RESERVOIR
G.C. SAMPLE TRANSFER
U TUBE
HIGH VACUUM
MANIFOLD
MERCURY DIFFUSION
PUMP
GAS FRACTIONATING
TRAPS
DEWAR CYLINDER
HELIUM SUPPLY
VEHICLE GAS
COLLECTION SYSTEM
TOGAS
CHROMATOGRAPH
TOEPLER PUMP
Figure 8-16 - Gas Handling System
8-31
-------
Figure 8-17 - Gas Handling System and Gas Chromatograph
-------
o Calibration gas storage volumes - used to store pure gases
or known mixtures which were used to calibrate the gas
chromatograph.
The noncondensable gases were to be handled first. The
complete step-by-step procedure is described as Sequence 10A in Appen-
dix D. The condensable gases were then handled and their procedure is
described as Sequence 10B in Appendix D.
8.5.3 Calibration of Gas Chromatograph
Prior to any analyses of samples generated by the vehicle,
it was necessary to check out the gas handling system and calibrate the
gas chromatograph. The gas handling system was set up in good working
order. A calibration gas from one of the gas storage volumes was expanded
into the high-vacuum manifold. By means of the Toepler pump, all of the
sample could be collected and measured in the gas buret. The sample was
then introduced into the G.C. transfer U-tube. The helium flow of the
gas chromatograph was diverted so that the volume of gas in the gas chro-
matograph transfer tube could then be introduced directly into the gas
chromatograph. The volume of gas introduced was calculated and the gas
chromatograph detector response was determined. For a series of different
volume sizes added to the gas chromatograph, a calibration curve could
be made. Figure 8-18 is the typical detector response calibration curve
obtained for carbon dioxide. Similar curves were prepared for other
gases expected.
The retention data for the column used were obtained in
the following manner. A gas mixture containing air (nitrogen and oxygen),
carbon monoxide, methane, carbon dioxide, water, and propane was prepared
exterior to the system. The mixture was stored in a separate volume.
Small samples could be introduced through the gas inlet of the gas handl-
ing system. The sample was collected in the gas buret and transferred
to the gas chromatograph. Several different temperature programs for the
gas chromatograph column were evaluated in order to obtain a reproducible
program which would elute all gases predictably and well separated.•
Figure 8-19 shows the typical retention time calibration for low molecular
weight gases which may be present in the noncondensable gas traps. The
components were separated on a column 6 feet long and 0.125 inch O.D.,
packed with Porapak Q. The column was initially cooled to less than
-70°C with dry ice. This condition was needed to separate N2, 02, and
CO. The column temperature was then raised rapidly to 30°C to elute
CH^ and C02. The column was then heated to 180°C at 10°C/min to elute
water, C^s, and C4*s.
8.5.4 Problems and Interferences
In Section 6.2.3, the integrity of the rotating seal was
discussed along with its leak rate as measured under both static and
dynamic conditions. It was impossible to eliminate the leak completely.
Under static conditions, the flow through the seal was VL37 cc/min. This
8-33
-------
1200
1000-
S 800
X
1
D
O
o
U-
o
cc
UJ
ED
600
Z
400
200
DETECTOR TEMPERATURE: 180°C
DETECTOR CURRENT: 180mA
0.20
0.40 0.60 0.80
NUMBER OF MOLES (X 10'5)
1.00
1.20 i
Figure 8-18 - Detector Response for Carbon Dioxide
improved to about 50 cc/min under the most optimum conditions. However,
in all cases there was a gas flow through the rotating seal into the
emissions collection system.
The rotating seal was downstream of the gas drier and car-
bon dioxide removal bed (described in Section 5.2.1). Thus the air
entering the rotating seal contained the normal atmospheric components
including carbon dioxide and water in addition to oxygen, nitrogen, and
argon. In heavy traffic, measurable amounts of carbon monoxide and nitro-
gen oxides were also expected to be present. The large amounts of carbon
dioxide and water obtained proved to be the major problem when the gases
were collected at low gaseous emission concentrations such as in the
8-34
-------
H
o.
O
cc
O
UJ
UJ
Q
CO
0
HEAT
DRY FAN TO
ICE ON 32°C
CH4
CO
6' 1/8" OD PORAPAK Q
37 CC/ mm
I
12
-30°C TO 180°C @ 10°/ mm
•Ar
IV
01
m
18 S
-70°C
Figure 8-19 - Typical Calibration Chromatogram for Low Molecular
Weight Gas
8-35
-------
Detroit Traffic Test. During the later stages of the program, attempts
were made to circumvent the carbon dioxide and water problems by selec-
tively collecting gases only during periods when gas emissions were ex-
pected to be adequate, such as the fade tests.
8.6 REFERENCES
(8-1) S. G. Bayer, T. A. Brown, and R. D. Zumwalde, "Equipment and
Procedures for Mounting Millipore Filters and Counting
Asbestos Fibers by Phase Contrast Microscopy," H.E.W. Public
Health Service, February 1969.
(8-2) R. E. Heffelfinger, C. W. Melton, and W. M. Henry, "Develop-
ment of a Rapid Survey Method of Sampling and Analysis for
Asbestos in Ambient Air," Interim Report to National Center
for Air Pollution Control, July 1970.
(8-3) W. J. Nicholson, A. N. Rohl, and E. F. Ferrand, "Air Pollu-
tion in New York City," Presented to Second International
Air Pollution Conference, Washington, D.C., December 1970.
(8-4) J. Murchio, Private Communication, 1971.
(8-5) K. Yada, "Study of Chrysotile Asbestos by a High Resolution
Microscope," Acta Chrystallegraphica, Vol. 23, 704 (1967).
8-36
-------
SECTION 9
VEHICLE TEST RESULTS
9.1 VEHICLE OPERATIONS
9.1.1 Test Scheduling and Problems Encountered
Early in the program, it was estimated that approximately
38 days would be required to complete each vehicle test. This estimate
was based on the optimistic assumption that the vehicle measurements
procedure (take emissions samples, measure wear, inspect system, and
replace worn parts) would require 1.5 days.
Tables 9-1, 9-2, and 9-3 are the actual versus estimated
test schedules for vehicle tests 1, 2, and 3, respectively. Vehicle
test 1 took 56 days because of the problems listed. Moreover, the mea-
surements sequence actually required approximately two days. In addition,
approximately one-half day was lost per schedule because of rain (the
summer of 1972 was the wettest summer in recent history). The sum of
the additional one-half day for measurements plus the one-half day for
rain loss gave an average of an additional one day per schedule, or an
additional seven days per vehicle test. Thus, the addition of seven days
to the estimate of 38 days gave a value of 45 days, achieved in vehicle
tests 2 and 3.
Near the end of vehicle test 3, there was a very good chance
of finishing in approximately 42-43 days. However, melting snow and
freezing rain made the driving conditions hazardous at times. Thus two
days were lost, and the program was completed just prior to the even more
wintry weather which began in late November in the Detroit area.
Some of the problems encountered in the program and their
solutions can be summarized as follows:
• During the 10-stop fade schedule of vehicle test 1, the hardened
steel ring which rotates aginst the Teflon seal slipped from its
anchored position after shearing the locking pins. The leak
thus created was detected immediately after the fade stops and
prior to the reburnish. The ring was reanchored and no further
problem was encountered during the 15-stop fade or any further
test schedule.
• During the Detroit traffic schedule of vehicle test 1, water
was found in the right rear brake collector. This was pulled
in through the rotating seal. This problem was not encountered
again, as the vehicle was not operated during heavy rain.
9-1
-------
Table 9-1 - Actual Versus Estimated Test Schedules for Vehicle Test 1
TEST
SCHEDULE
Burnish
Measurements*
A. B. Baseline
Measurements
Detroit Traffic
Measurements
10-Stop Face
Reburnish
Measurements
A. F. Baseline
Measurements
15-Stop Fade
Reburnish
Measurements
Final Baseline
Measurements
ESTIMATED
TIME (DAYS)
2.0 , ,
1.5
3-0 , 5
1.5
12.0 ,
1.5 13'5
1.5
1.0 4.0
1.5
3'° 4 5
1.5 ^
1.0
1.0 3.5
1.5
3>° 4 5
1.5 4'5
38.0
ACTUAL TIME (DAYS)
START
5/1
5/11
5/19
6/14
6/22
6/30
7/6
FINISH
5/10
5/18
6/13
6/21
6/29
7/5
7/12
TOTAL
8
6
20
6
6
5
5
56
REMARKS OR PROBLEMS
• Heaters shorted.
• Inverter failed.
• Loose collector screws.
• Slow silicone cure.
• Burned-out heater.
• Water in rear collector
(due to rain).
• Replaced rear seal.
• Burned air line.
• Replaced filters .
• Rain - test stopped.
• Slow silicone cure.
• Rain.
• Slow silicone cure.
• Burned-out T.C.
• Measurements - fronts
only.
• Rotor ring slippage.
• Rain.
«
Take emissions samples, measure wear, inspect systems, replace worn parts,
9-2
-------
Table 9-2 - Actual Versus Estimated Test Schedules for Vehicle Test 2
TEST
SCHEDULE
Burnish
Measurements*
A. B. Baseline
Measurements
Detroit Traffic
Measurements
10-Stop Fade
Reburnish
Measurements
A. F. Baseline
Measurements
15-Stop Fade
Reburnish
Measurements
Final Baseline
Measurements
ESTIMATED
TIME (DAYS)
2'° 3.5
3.0 , _
1.5 4'5
12'° 13 5
1.5 1J>;J
1.5
1.0 4.0
1.5
3.0
1.5 4-5
1.0
1.0 3.5
1.5
3.0 . ,
1.5 4'5
38.0
ACTUAL TIME (DAYS)
START
7/13
7/18
7/24
8/16
8/22
8/30
9/7
FINISH
7/17
7/21
8/15
8/21
8/29
9/6
9/13
TOTAL
4
4
18
4
6
4
5
45
REMARKS OR PROBLEMS
• Rain.
• T/C- replaced.
• Inverter malfunction.
• Rain.
• T/C replaced.
• Lost pressure on llth
circuit. Brake fluid
in collector. Test
terminated.
VO
I
CO
Take emissions samples, measure wear, inspect systems, replace worn parts.
-------
V£>
I
Table 9-3 - Actual Versus Estimated Test Schedules for Vehicle Test 3
TEST
SCHEDULE
Burnish
Measurements
A. B. Baseline
Measurements
Detroit Traffic
Measurements
10-Stop Fade
Reburnish .
Measurements
A. F. Baseline
Measurements
15-Stop Fade
Reburnish
Measurements
Final Baseline
Measurements
ESTIMATED
TIME (DAYS)
2'° 3 5
1.5 ^
3<0 4 S
1.5
12.0
1.5 ^'^
1.5
1.0 4.0
1.5
3.0 ,
1.5 'D
1.0
1.0 3.5
1.5
3.0
1.5 *•*
38.0
ACTUAL TIME (DAYS)
START
9/18
9/22
9/29
10/24
10/27
11/3
11/9
FINISH
9/21
9/28
10/23
10/26
11/2
11/8
11/17
TOTAL
4
5
17
3
5
4
7
45
REMARKS OR PROBLEMS
• Rain.
• Freezing rain.
• Icy roads.
Take emissions samples, measure wear, inspect systems, replace worn parts.
-------
• During the final baseline schedule of vehicle test 2, pressure
was lost for the rear brakes and brake fluid was found in the
collector. The combined sump and surfaces sample, for the
eleven completed circuits, was salvaged by filtering and re-
peatedly washing the particulates to remove the brake fluid.
The linings were "destroyed" as the fluid could not be removed
completely. This problem was not encountered again.
9.1.2 Mileage Accumulations
Table 9-4 lists the mileage accumulations for each schedule.
The A.B. Baseline, A.F. Baseline, and Final Baseline were run according
to the same schedule, repeated at different times within the overall
vehicle test program. The average baseline mileages varied from 343 to
348 miles and the maximum variation between vehicle tests was +5.7 percent.
This range for the baseline schedules could also be compared to one-fourth
of the Detroit traffic test for which the average was 352 miles (1408 v 4)
and for which the overall variation was +3.8 percent. The overall vari-
ation for the total mileage accumulation of all three vehicle tests was
very low at +2.4 percent. These mileage variations were primarily due
to the varying times taken to reach the Detroit traffic circuit. Normally
only three round trips were required to obtain the twelve circuits. Rain,
seal failure, thermocouple malfunctions, and other minor difficulties
which required a premature return to base added to the minimum mileage
possible.
9.1.3 Reporting of Vehicle Test Data
The data for each vehicle test are accumulated in a separate
volume which includes a section for each test sequence: Burnish; A.B.
(After-Burnish) Baseline; Detroit Traffic; 10-Stop Fade; A.F. (After-
Fade) Baseline; 15-Stop Fade; and Final Baseline. Each section includes
the following data sheets: Vehicle Log Sheet; supplementary vehicle
data sheets such as Detroit Traffic data sheets; Wear Sheet - Front Axle;
Wear Sheet - Rear Axle; Collection of Brake Emissions (Right Side); Col-
lection of Brake Emissions (Left/Control Side); and Test Summary Sheet.
The complete list and examples of each type of data sheet
are included in Appendix G.
9.2 PERFORMANCE OF EMISSIONS COLLECTION SYSTEMS
9.2.1 Rotating Seal Life
The success of the vehicle tests depended heavily on the
proper operation of the rotating seals. Table 9-5 is a running log of
rotating seal mileages (life) obtained during the vehicle test program.
The original intent was to change the rotating seals at the start of
each test and prior to the 10-Stop Fade. Both premature seal failure
and the unexpected fact that disastrous rotating seal wear did not occur
during the fade led to abandonment of that plan.
9-5
-------
Table 9-4 - Summary of Vehicle Mileage Accumulations
Schedule
Burnish
A.B.
Baseline
Detroit
Traffic
10-Stop
Fade
A.F.
Baseline
15-Stop
Fade
Final
Baseline
Totals
Test
1
2
3
1
2
3
1
2
3
1
2
3 .
1
2
3
1
2
3
1
2
3
1
2
3
Miles
174
127
100
328
348
368
1439
1430
1355
47
53
58
356
339
347
47
79
52
352
326
352
2756
2702
2632
8090
Average
Miles
134
348
1408
53
347
59
343
2697
Maximum
Deviation
34
20
53
6
9
20
17
65
Percent
Deviation
5.7
3.8
2.6
4.9
2.4
9-6
-------
Table 9-5 - Running Log of the Rotating Seals Mileages
Vehicle Test Program
Obtained in the
Test
Schedule
Pre-Test
Burnish
A. B. Baseline
Detroit Traffic
10-Stop Fade
A. F. Baseline
15-Stop Fade
Final Baseline
Total Miles
MK III
Front Collector
Vehicle
Test 1
126
174
328
1431/2059
47
356
47
353/815
2756
Vehicle
Test 2
127
348
1430/1965
53
339/392
12/12
67
326/393
2702
Vehicle
Test 3
100
368
1355
58
347/2664*
52
352/404
2632
MK III
Rear Collector
Vehicle
Test 1
174
328
731/1233
700
47
356
47
353/1515
2756
Vehicle
Test 2
127
348/475
1430
53/1483
339
79
326/744
2702
Vehicle
Test 3
100
368
103/1315
62/62
1190
58/1248
347
52
352/751
2632
Comments
Test 1: OK
Test 2: OK
Test 3: OK
Test 1: OK
Test 2: Rear seal failed and replaced after
475 miles.
Test 3: OK
Test 1: Rear seal replaced after 1233 miles.
Front seal replaced after 2059 miles.
Test 2: OK
Test 3: Rear seal replaced after 103 miles.
Front seal replaced after 62 miles -
"out-of-round. "
Test 1: OK
Test 2: Front seal replaced after 1958 miles.
Rear seal failed and replaced after
1483 miles.
Test 3: OK
Test 1: OK
Test 2: Front seal failed and replaced after
392 miles.
Test 3: Front seal replaced after 2664 miles.
Test 1: OK
Test 2: Front seal failed and replaced after
12 miles.
Test 3: OK
Test 1: Front seal replaced after 815 miles.
Rear seal replaced after 1515 miles.
Test 2: OK, seals used to start Test 3.
Test 3: OK
Includes 393 Miles from Test 2
-------
Table 9-6 summarizes the rotating seal life in miles ob-
tained for each seal during the three vehicle tests. These data were
used to obtain a maximum average life for each rotating seal.
Seven rotating seals were used on the front disc brake
collector. They were replaced at different mileage accumulations as
follows:
• Two seals failed after 12 and 329 miles.
• Three seals survived 1965, 2059, and 2664 miles and were
replaced as worn, but not failed.
• Two seals were used for 815 and 404 miles and were replaced
although they were not completely worn or failed after vehicles
tests 1 and 3, respectively.
Eight rotating seals were used on the rear drum brake
collector. They were replaced at different mileage accumulations as
follows:
• Three seals failed after 62, 475, and 1483 miles.
• Four seals survived 1233, 1515, 1315, and 1248 miles and were
replaced as worn, but not failed.
• One seal survived 751 miles and was removed in good condition
after the third vehicle test.
9.2.2 Operating Temperatures
9.2.2.1 Normal Brake Stops
Throughout the vehicle tests, it was necessary to monitor
the temperatures at all four wheels. The driver was instructed to take
specified actions when greater than desired temperature differences
occurred. For example, during the Detroit Traffic Circuits, the maximum
normal operating temperature was 330°F before proceeding. These cool-down
periods were seldom necessary.
The effectiveness of the thermal control aids attached to
the right front brake described in Section 5.5.3 is shown in Table 9-7.
The AT = 200 to 250°F shown for the initial burnish was reduced to a
AT = 115 to 160°F. Most important was the reduction of the right front
brake operating temperature from about 400°F to about 300°F.
Since approximately 90 percent of the test miles were
driven on the Detroit Traffic circuit, it was necessary to monitor the
temperatures obtained and maintain test reproducibility. Although the
temperatures did vary slightly, the normal operating range for the right
front brake was 260 to 300°F while the normal operating range for the
right rear brake was 170 to 200°F. The brake shrouding did not present
any difficulties on hot days. Table 9-8 illustrates the brake tempera-
tures measured during four consecutive Detroit Traffic Circuits on a hot
9-8
-------
Table 9-6 - Rotating Seal Life (Miles)
VEHICLE
TEST
1
2
3
SEAL
INSTALLATION
1
2
3
4
5
6
5 (cont'd)
6 (cont'd)
7
8
Maximum
Expected
Life (miles)
FRONT DISC BRAKE
Fl 2059
F2 815
F3 1965
F4 392
F5 12
F6 (393)*
F6 2664
F7 404
2059
1965 Average:
2664 2229
REAR DRUM BRAKE
Rl 1233
R2 1515
R3 475
R4 1483
R5 (744)*
R5 1315
R6 62
R7 1248
R8 751
1233
1515
1483 AVi35f:
1315
1248
Continued usage into Vehicle Test No. 3.
9-9
-------
VO
M
O
Table 9-7 - Brake Temperatures During Burnish Tests (°F) (Vehicle Test 1)
INITIAL BURNISH
(NO THERMAL CONTROL AIDS)*
After 20 Stops
After 40 Stops
After 60 Stops
RERUN BURNISH
(WITH THERMAL CONTROL AIDS)**
After 10 Stops
After 40 Stops
After 60 Stops
After 80 Stops***
After 100 Stops
After 160 Stops
FRONT DISC BRAKE
Right
(Shrouded)
400
340
360
280
310
265
200
280
300
Left
(OEM Configuration)
150
120
160
150
150
150
130
165
170
AT
250
220
200
130
160
115
70
115
130
REAR DRUM BRAKE
Right
(Shrouded)
255
200
245
205
245
215
160
220
190
Left
(OEM Configuration)
150
110
150
150
165
165
135
170
130
AT
150
90
95
75
80
50
35
50
70
***
Test stopped because of failure of Mk II rear drum seal.
Thermal control aids on front wheel plus Mk III rear drum seal.
k
Start of second day.
-------
Table 9-8 - Brake Temperatures During Detroit Traffic Circuits
(Vehicle Test 2 - A.B. Baseline)
Location on
Traffic Route
12 Mile and Woodward
Michigan and Third
Adams and Woodward
Adams and Woodward
12 Mile and Woodward
12 Mile and Woodward
Michigan and Third
Adams and Woodward
Adams and Woodward
12 Mile and Woodward
12 Mile and Woodward
Michigan and Third
Adams and Woodward
Adams and Woodward
12 Mile and Woodward
12 Mile and Woodward
Michigan and Third
Adams and Woodward
Adams and Woodward
12 Mile and Woodward
Time of
Day
(July 20, 1972)
6:25 am
6:50
6:59
7:13
7:54
7:54 am
8:37
8:52
9:08
9:48
9:48 am
10:25
10:38
10:49
11:34
1:00 pm
1:42
1:59
2:17
2:50
Ambient
Temp.
°F
75
78
78
79
79
79
80
82
82
84
84
85
85
87
85
90
91
91
91
91
Range (°F)
Front Disc Brake
Right
(Shrouded)
180
260
260
270
270
270
300
300
280
330
330
310
300
280
310
310
320
310
310
300
260-330
Left
(Normal)
130
140
150
150
150
150
160
160
150
190
190
170
170
160
160
210
180
180
170
160
150-210
AT
50
120
110
120
120
120
140
140
140
140
140
140
130
120
150
100
140
130
140
140
110-140
Rear Drum Brake ,/
Right
(Shrouded)
120
150
140
150
150
150
170
180
180
190
190
200
190
180
190
'160
210
210
200
170
140-210
Left
(Normal)
120
140
140
150
150
150
160
160
. 160
160
160
170
140
170
160
160
180
180
170
150
140-180
AT
0
10
0
0
0
0
10
20
20
30
80
30
20
10
30
0
30
30
30
20
10-30
-------
July day with ambient temperatures up to 91°F. The At between the
front brakes remained between 110 and 140°F while that for the rear drum
brakes' remained between 10 and 30°F.
The temperature trends discussed here were typical for
all three vehicle tests.
9.2.2.2 Heavy-Duty Fade Stops
During the Detroit Traffic Test, a series of stops from
40 mph, in rapid succession, every two blocks caused all four brakes to
rise in temperature faster than normal. The shrouded brakes would then
cool slower than the normal brakes during subsequent running. Conse-
quently, it was anticipated that during the fade tests it would be
necessary to program the right front disc brake according to the known
temperature versus stop number for the same friction materials previously
run on an inertia dynamometer and on a normal test vehicle.
The dynamometer and normal vehicle test baseline results
are given in Figure 9-1. Two different dynamometer tests are included.
The data for the shrouded right front disc brake and the normal left
front disc brake are superimposed on the baseline results. After the
7th stop, the time increment was increased for the vehicle test to pre-
vent the right front disc brake from overheating the lining and creating
an abnormal situation. The left brake showed a slight temperature reduc-
tion during this increased interval. The right front brake was thus
held to the illustrated time-versus-stop curve by increasing the interval
as necessary. A temperature of 525°F was recorded as the temperature before
the 10th stop. Temperature excursions after the last two stops were higher
than 540°F. The recovery stops demonstrated the rate at which the brakes
returned to their normal operating temperatures.
The data for the rear drum brakes are also shown in Fig-
ure 9-1. The shrouded rear drum brake followed the baseline curve closely.
The left rear drum brake showed a slight temperature reduction with the
increase in interval. During the recovery stops, both rear brakes followed
the baseline cooling curve closer than the corresponding disc brakes
followed their baseline cooling curve.
Figure 9-2 shows the corresponding data for the 15-Stop
Fade schedule. Baseline data for two inertia dynamometer tests are also
plotted on the graph. During the vehicle test, the shrouded right front
disc brake began to heat more rapidly than expected (based on the 10-stop
fade experience) and the increased interval for cooling between stops
was first necessary after the 5th stop. Additional increased intervals
were then necessary after each succeeding stop. Consequently, the left
front disc brake never did increase above 300°F. A temperature of 575°F
was recorded as the temperature before the 15th stop. Temperature excur-
sions after the last 6 stops were higher than 600°F.
9-12
-------
FRONT BRAKES
600
500- -
TT 400--
u
CC
DC
UJ
1
UJ
300-
200--
100- -
FIRST
INCREASED
INTERVAL
VEHICLE
O BASELINE
A RIGHT
D LEFT
8 10
8 10 12
REAR BRAKES
600--
500- -
400 - -
HI
CC
cc
LU
a.
300--
200-
100- -
FIRST
INCREASED
INTERVAL
f
468
FADE
10 2
STOP NUMBER
46 8 10 12
RECOVERY
Figure 9-1 - Brake Temperature Data - Vehicle Test 1, 10-Stop Fade
9-13
-------
FRONT BRAKES:
600-r
500 +
cc
400 +
300 -h
CC
Ul
o.
LLJ 200
100-
FIRST
INCREASED
INTERVAL
DYNAMOMETER
O BASELINE
A RIGHT
D LEFT
8 10 12 14
8 10
12
REAR BRAKES:
600-
500
o_ 400 -|-
LU
cc
D
< 300-
cc
LU
a.
I" 200-
100
FIRST
INCREASED
INTERVAL
14
6 8 10 12
FADE
STOP NUMBER
6 8
RECOVERY
10 12
Figure 9-2 - Brake Temperature Data - Vehicle Test 1, 15-Stop Fade
9-14
-------
The long time period at which the brakes were above 500°F
produced an additional effect within the shrouded brake. The heat gener-
ated at the rotor/pad interfaces was retained within the shroud and caused
the brake fluid within the right front caliper to heat. The resultant'
boiling of fluid produced a "loss of brake pedal" for the 14th and 15th
stops; the brakes bottomed out, and pumping the brakes did not restore
adequate line pressure to maintain the planned deceleration.
The recovery data illustrate the rate at which the
shrouded brakes recovered from the high-temperature testing. The fluid
boil (soft pedal) persisted through the first eight recovery stops until
the indicated lining temperature of the shrouded brake fell below 400°F.
This behavior demonstrates the effectiveness of air cooling in keeping
brake temperature low on normal unshrouded brakes.
The data for the drum brakes are also illustrated in
Figure 9-2. The increased interval early in the test sequence held the
temperatures lower than for the baseline data.
The temperature trends discussed for the fade schedules
were typical for all three vehicle tests.
9.2.3 Collection Efficiencies
9.2.3.1 Recovery of Brake Particulate Emission
The weights of brake particulate wear debris collected
during vehicle tests 1, 2, and 3 are given in Tables 9-9, 9-10, and 9-11,
respectively.
For the right front disc brake, the surface sample has
the largest weight of the three samples taken. The sump and airborne
samples are comparable in weight. For the left front brake, the sump
sample was comparable in weight to the right front brake. Moreover the
total weight of the samples taken from the left front brake of vehicle
tests 1 and 2 were comparable when added for each schedule to arrive
at a total weight for the entire vehicle test. On the other hand, the
cumulative sample taken for all of the vehicle test 3 was significantly
less.
For the right rear drum brake, the surfaces sample has
the largest weight of the three samples taken. The sump and the airborne
samples are comparable in weight. In some instances, the results for the
sump value were reported negative. This occurred because of the 80 per-
cent return of material to the sump from each preceding schedule. No
negative values occurred during the normal driving up to the end of the
Detroit Traffic Test schedule. During the more severe fade tests, some
of the 80 percent return was redistributed to the surfaces samples. The
overall wear debris from each wheel did, however, have a positive weight
gain.
9-15
-------
Table 9-9 - Weights of Brake Particulate Wear Debris Collected
(Vehicle Test 1) (gm)
Schedule
Burnish
A.B.
Baseline
Detroit
Traffic
10 Stop
Fade
A.F.
Baseline
15 Stop
Fade
Final
Baseline
Totals
Collector
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Entire
Test
Front Brakes
Right
(Shrouded)
0.142
0.412
0.061
0.083
0.644
0.130
0.201
2.010
0.237
0.580
1.212
0.013
0.191
1.764
0.259
0.616
5.943
0.120
0.154
2.011
0.375
0.967
13.996
1.195
17.158
Left
(Normal)
0.116*
0.029
0.128
0.055
0.458
0.109
0.244
0.076
0.153
0.030
0.150
0.027
0.138
0.083
1.387
0.409
1.796
Rear Brakes
Right
(Shrouded)
0.144
1.170
0.046
0.185
0.590
0.049
0.436
4.052
0.285
-0.335
0.371
0.017
0.060
0.652
0.030
-0.046
0.100
0.004
0.097
0.440
0.003
0.541
7.375
0.434
8.350
Left
(Normal)
0.220
0.394
0.208
0.205
1.654
0.878
1.120
0.275
-0.516
1.543
-0.330
0.169
0.017
0.448
2.373
3.912
6.285
*Estimated from cumulative sample (0.145 gm) taken during this
schedule only. 6
9-16
-------
Table 9-10 - Weights of Brake Particulate Wear Debris Collected
(Vehicle Test 2) (gm)
Schedule
Burnish
A.B.
Baseline
Detroit
Traffic
10 Stop
Fade
A.F.
Baseline
15 Stop
Fade
Final
Baseline
Totals
Collector
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Entire
Test
Front Brakes
Right
(Shrouded)
0.109
0.432
0.039
0.049
0.481
0.015
0.042
2.828
0.106
0.170
1.437
0.023
0.098
1.114
0.107
0.098
2.205
0.099
0.051
1.193
0.138
0.555
9.690
0.527
10.772
Left
(Normal)
0.122
0.032
_
0.343
0.126
0.128
0.055
0.084
0.036
0.084
0.049
0.111
0.141
0.984
0.439
1.423
Left Brakes
Right
(Shrouded)
0.105
0.166
0.004
0.081
0.596
0.007
1.247
4.159
0.056
-0.217
1.322
0.010
-0.047
0.749
0.004
-0.047
0.181
0.008
0.260*
1.070*
0.011
0.941
8.293
0.104
9.288
Left
(Normal)
-0.132
0.157
0.109
0.166
0.955
0.769
-0.597
0.290
-0.255
0.328
-0.255
0.360
0.295
0.172
0.637
2.242
2.879
Value may be in error because of brake fluid in collector during
Final Baseline schedule.
9-17
-------
Table 9-11 - Weights of Brake Particulate Wear Debris Collected
(Vehicle Test 3) (gm)
SCHEDULE
Burnish
A.B.
Baseline
Detroit
Traffic
10 Stop
Fade
A.F.
Baseline
15 Stop
Fade
Final
Baseline
Totals
COLLECTOR
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Entire
Test
FRONT BRAKES
RIGHT
(SHROUDED)
0.121
0.408
0.045
0.266
1.097
0.138
0.208
3.773
0.495
0.438
0.515
0.188
0.033
1.389
0.328
0.391
3.075
0.402
0.105
2.860
0.337
1.562
13.117
1.933
16.612
LEFT
(NORMAL)
Cumulative
Sample
1
'
0.182
0.169
0.351
REAR BRAKES
RIGHT
(SHROUDED)
0.319
2.056
0.033
0.215
1.234
0.052
0.379
1.154
0.027
0.151
0.248
0.015
0.118
0.295
0.050
0.088
0.184
0.018
0.246
2.288
0.017
1.516
7.459
0.212
9.187
LEFT
(NORMAL)
Cumulative
Sample
i
'
0.974
1.908
2.882
9-18
-------
9.2.3.2 Mass Balance
£.2.3.2.1 Amount of Emissions
The initial weights of the brake friction material and
the weight losses per wheel are given in Table 9-12. The weights of the
particulates collected (Tables 9-9, 9-10, and 9-11) and the data in
Table 9-12 were used to calculate the mass balances given in Tables 9-13,
9-14, and 9-15 (numbers not in parentheses).
The right front brake data ranged from approximately
42 percent recovery in the initial tests to approximately 70 percent in
the later tests. The low initial recovery may have been due to excess
gassing of the green linings resulting in a lower recovery as particu-
lates. This condition changed as the linings became burnished to a
greater extent and the frictional heat-affected layer contained more
inorganic content. The recovery for the 10-stop fade of vehicle tests 1
and 3 were low as the debris was "tarry" and the surfaces fraction could
be collected only with difficulty. The recovery for the 15-stop fade
of vehicle tests 1 and 3 was somewhat low, possibly for the same reason.
The left front brake showed the same basic trends as
the right front brake, increasing throughout the vehicle tests where
normal driving was carried out. During the two fade tests and after
fade and Final Baseline, approximately 2 to 3 times more wear debris
remained in the unshrouded brake. This may have been due to the high
concentration of wear debris produced, which in turn was scraped into the
rivet holes during the braking.
The material recovery totals for the rear brakes show
wide variations. The problem, in part, was due to the carryover from
test-to-test of the sump debris, 80 percent of which was returned to the
brake after each test schedule. The data can be explained partially
by examination of the distribution of particulate emissions obtained at
each sample location.
9.2.3.2.2 Distribution of Emissions
The data given in parentheses in Tables 9-13, 9-14,
and 9-15, represent the percent of total particulates collected - the
distribution of the particulate emissions. The bottom portion of Tables
9-13, 9-14, and 9-15, shows the ranges for the distribution into sump,
surface, and airborne samples.
The data for the rear brakes fell into fairly narrow
ranges for the first three schedules only. From the 10-Stop Fade to
the Final Baseline, the data show both negative recoveries and greater
than 100 percent recoveries. For both the 10- and 15-Stop Fade schedules
of vehicle test 1, the negative recovery figures were not reflected by
corresponding increases in the surface or airborne figures. However, the
reverse situation prevailed in vehicle test 2 for the 10-Stop Fade and
the ensuing A.F. Baseline.
9-19
-------
VO
Table 9-12 - Brake Friction Material Initial Weights and Weight
Losses (gm)
en
01
CO
CO
o
,J
4J
,e
00
•H
01
01
4J
Ml
•H
3
Initial
Duty
Moderate
Heavy
to
Abusive
Cumulative
As
Prepared
Schedule
Burnish
A. B. Baseline
Detroit Traffic
Totals
10-Stop Fade
A. F. Baseline
15-Stop Fade
Final Baseline
Totals
Total Wear
Inner
Outer
Primary
Secondary
Totals
Vehicle Test 1
Front
Right
1.48
1.86
5.64
8.98
5.72
3.34
11.87
3.73
24.66
33.64
95.8
117.4
213.2
Left
0.96
1.29
4.17
6.42
0.78
1.14
0.50
1.22
3.64
10.06
93.8
116.5
210.3
Rear
Right
3.33
0.92
5.80
10.05
0.45
1.02
0.29
0.49
2.25
12.30
108.1
189.6
297.7
Left
1.35
1.21
4.96
7.52
0.67
2.39
0.25
1.13
4.44
11.96
106.4
189.3
295.7
Vehicle Test 2
Front
Right
1.45
1.15
4.11
6.71
2.69
2.87
3.62
1.89
11.07
17.78
106.4
105.0
211.4
Left
0.94
1.11
3.53
5.58
1.58
1.28
0.49
0.68
4.03
9.61
106.1
105.6
211.7
Rear
Right
0.66
1.21
5.31
7.18
1.01
0.28
0.35
1.57
3.21
10.39
104.9
181.3
286.2
Left
0.79
1.17
4.16
6.12
0.54
0.95
0.55
0.83
2.87
8.99
102.4
180.2
282.6
Vehicle Test 3
Front
Right
1.32
2.81
5.02
9.15
4.44
2.11
7.79
4.14
18.48
27.63
115.3
152.3
267.6
Left
0.62
1.39
5.05
7.06
0.82
1.17
0.72
2.44
5.15
12.21
113.0
160.3
273.3
Rear
Right
3.11
1.89
1.83
6.83
1.22
0.61
1.20
1.19
4.30
11.13
113.2
153.5
266.7
Left
3.06
0.80
4.67
8.53
1.90
1.34
0.80
1.45
5.49
14.02
113.7
167.7
280.4
-------
Table 9-13 - Material Percent Recovery as Particulate Emissions
(Vehicle Test 1)
SCHEDULE
Burnish
A.B.
Baseline
Detroit
Traffic
10 Stop
Fade
A. F.
Baseline
15 Stop
Fade
Final
Baseline
Ranges
COLLECTOR
Sump
Surfaces
Airborne
Total
Sump
Surface
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
FRONT BRAKES
RIGHT
(SHROUDED)
(24)* 10
(67) 28
(9) 4
42
(11) 5
(24) 34
(15) 7
45
(10) 4
(81) 35
(9) 4
43
(31~) 10
(63+) 20+
(6-) 2
32+
(9) 6
(79) 52
(12) 8
66
(9) 5
(89) 50
(2) 1
56
(6) 4
(79) 54
(15) 10
68
( 6-31)
(63-89)
( 2-15)
LEFT
(NORMAL)
(81) 9
(19) 2
U
(71) 10
(29) 4
14"
(79) 11
(21) 3
14
(76) 31
(24) 10
41
(81) 13
(19) 3
16"
(88) 30
(17) 6
36
(61) 11
(39) 7
18"
(61-83)
(17-39)
REAR BRAKES
RIGHT
(SHROUDED)
(10) 4
(87) 36
(3) 1
41
(22) 20
(72) 65
(6) 5
90
(9) 7
(85) 70
(6) 5
82
-75
83
4
12
(8) 6
(88) 64
(4) 3
73
-16
35
1
20
20
90
1
111
( 8-22)
(72-88)
( 3-6)
LEFT
(NORMAL)
(36) 16
(64) 29
4l
(51) 17
(49) 16
33"
(65) 33
(35) 18
5l
166
41
207
-22
65
~43~
-133
68
-65
1
40
4l
(36-65)
(35-65)
*Numbers in parenthesis are percents of total particulates collected: 10/42 = 24%
Not all of the sample was recovered.
9-21
-------
Table 9-14 - Material Percent Recovery as Particulate Emissions
(Vehicle Test 2)
SCHEDULE
Burnish
A.B.
Baseline
Detroit
Traffic
10 Stop
Fade
A.F.
Baseline
15 Stop
Fade
Final
Baseline
Ranges
COLLECTOR
Sump
Surfaces
Airborne
Total
Sump
Surface
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
FRONT BRAKES
RIGHT
(SHROUDED)
(20)* 8
(73) 30
(7) 3
41
(7) 4
(71) 41
(22) 13
58
(2) 1
(93) 65
( 5) 3
69
(10) 6
(88) 33
(2) 1
60
(2) 1
(89) 39
(9) 4
44
(5) 3
(90) 61
(5) 3
67
(4) 3
(86) 63
(10) 7
73
(2-20)
(71-93)
(2-22)
LEFT
(NORMAL)
(81) 13
(10) 3
16
Not
Sampled
(72) 10
(28) 4
14"
(72) 8
(28) 3
n
(83) 15
(17) 3
18
(63) 17
(37) 10
IT
16
21
IT
(63-83)
(17-37)
REAR BRAKES
RIGHT
(SHROUDED)
(38) 16
(60) 25
(2) 1
42
(12) 7
(86) 49
(2) 1
57
(22) 23
(77) 78
(1) 1
102
-22
131
1
111
-181
267
1
87
-13
52
2
41
Brake
Fluid
in Linings
(12-22)
(60-86)
(1-2)
LEFT
(NORMAL)
-17
20
~
(39) 9
(61) 14
23
(56) 23
(44) 18
41
-110
54
^56"
(44) 28
(56) 35
63
-46
65
19
(63) 36
(37) 21
57
(39-63)
(37-61)
*Numbers in brackets are percents of total particulates collected: 8/41 = 20%
9-22
-------
Table 9-15 - Material Percent Recovery as Particulate Emissions
(Vehicle Test 3)
SCHEDULE
Burnish
A.B.
Baseline
Detroit
Traffic
10 Stop
Fade
A.F.
Baseline
15 Stop
Fade
Final
Baseline
Ranges
COLLECTOR
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
FRONT BRAKES
RIGHT
(SHROUDED)
(21)* 9
(72) 31
(7) 3
43
(19) 10
(72) 39
(9) 5
54
(5) 4
(85) 75
(11) 10
89
(38) 10
(46) 12
(16) 4
26
(2) 2
(79) 66
(19) 16
84
(20) 10
(70) 34
(10) 5
49
(4) 3
(86) 69
(10) 8
80
( 2-38)
(46-86)
( 7-19)
LEFT
(NORMAL)
Cumul
Sam
1
ative
pie
r
(52) 1.5
(48) 1.4
~3~
REAR BRAKES
RIGHT
(SHROUDED)
(13) 10
(83) 66
(4) 3
79
(9) 7
(87) 65
(4) 3
75
(25) 21
(74) 63
(1) 1
85
(36) 12
(61) 20
(3) 1
33
(25) 19
(64) 48
(11) 8
75
(32) 7
(64) 14
(4) 1
22
H20
in
Linings
( 9-36)
(61-87)
( 1-11)
LEFT
(NORMAL)
Cumul
Sam
1
ative
pie
f
(34) 9
(66) 17
26"
*Numbers in brackets are percents of total particulates collected.
9-23
-------
The ranges for the sump, surfaces, and airborne samples
given at the bottom of all three tables agreed rather well for all brakes
irregardless of the brake friction materials used or the rotor conditions
prior to the start of the test.
9.3 PERCENT ASBESTOS CONTENTS
9.3.1 Program Results
The microscopy results were converted by the computer into
the asbestos emissions results summarized in Tables 9-16, 9-17, and 9-18.
For vehicle test 1, the range of asbestos contents in brake
emissions varies from a high of 1.65 percent down to a low of 0.05 per-
cent. Of the 47 analyses reported, only two were above 1.00 percent.
The overall average was 0.38 percent.
For vehicle test 2, the range of asbestos contents in brake
emissions varies from a high of 1.42 percent down to a low of 0.03 per-
cent. Of the 43 analyses reported, only one was above 1.09 percent, and
only three were in the range 0.50 to 0.96 percent; all others were less
than 0.50 percent. The overall average, was 0.25 percent.
For vehicle test 3, the range of asbestos content in brake
emissions varies from a high of 0.51 percent down to a low of 0.003 per-
cent. Of the analyses reported, three were in the range 0.20 to 0.51 per-
cent; all others were less than 0.20 percent. The overall average was
0.07 percent.
For all three vehicle tests, the overall average of asbestos
content in the brake emissions was 0.23 percent. The following trends
were noteworthy:
• The right front disc brake yielded higher asbestos contents
than the right rear drum brake (for two of the three vehicle
tests):
Vehicle Test R.F. Disc (%) R.R. Drum (%)
1 0.45 0.30
2 0.26 0.24
3 0.07 0.07
• In^general, the airborne samples contained a lower asbestos
weight percent than the corresponding sump and surfaces samples.
• In general, the asbestos weight percent in brake emissions was
higher when the materials were new; the asbestos content de-
creases with brake use.
• For all vehicle tests, the asbestos weight percent increased
only slightly for the severely burnished brakes during the
fade tests.
9-24
-------
Table 9-16 - Summary of Asbestos Analytical Results (Vehicle Test 1)
(Weight Percent)
Schedule
Burnish
A.B.
Baseline
Detroit
Traffic
10-Stop
Fade
A.F.
Baseline
15-Stop
Fade
Final
Baseline
Collector
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Average
Front Brakes
Right
(Shrouded)
0.813
0.398
0.144
(0.452)*
1.650
0.472
0.290
(0.804)
0.247
0.137
0.052
(0.145)
0.463
0.162
0.154
(0.260)
0.656
0.507
0.134
(0.432)
0.602
1.548
0.175
(0.775)
0.435
0.290
0.167
(0.297)
0.452
Left
(Normal)
Not
Anal
)
**
yzed
i
Average
Rear Brakes
Right
(Shrouded)
0.865
0.349
(0.607)
0.179
0.415
0.493
(0.362)
0.129
0.373
0.092
(0.198)
0.280
0.071
0.132
(0.161)
0.419
0.242
0.079
(0.247)
0.071
0.257
0.222
(0.183
0.585
0.324
0.145
(0.351)
0.301
Left
(Normal)
No
Anal
1
0.
0.
0.
0.
t
yzed
t
991
265
275
416
Not
Analyzed
0.
0.
439
472
Not
Analyzed
*Average value for wheel where collection took place.
**Not Analyzed - indicates that analysis was not required.
9-25
-------
Table 9-17 - Summary of Asbestos Analytical Results (Vehicle Test 2)
(Weight Percent)
SCHEDULE
Burnish
A.B.
Baseline
Detroit
Traffic
10-Stop
Fade
A.F.
Baseline
15-Stop
Fade
Final
Baseline
COLLECTOR
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Average
FRONT BRAKES
RIGHT
(SHROUDED)
0.402
0.968
0.186
(0.515)*
0.236
0.311
0.211
(0.253)
0.304
0.548
0.234
(0.362)
0.244
0.261
0.107
(0.260)
0.443
0.173
0.165
(0.260)
0.119
0.193
0.095
(0.136)
0.117
0.071
0.032
(0.073)
0.258
LEFT
(NORMAL)
Not
Analyzed
i
r
Average
REAR BRAKES
RIGHT
(SHROUDED)
0.484
1.416
0.087
(0.636)
0.268
0.098
0.344
(0.237)
0.249
0.113
0.115
(0.159)
0.199
0.619
0.194
(0.185)
0.138
0.237
0.180
(0.185)
0.065
0.136
0.048
(0.083)
0.058
0.067
(0.063)
0.243
LEFT
(NORMAL)
Not
Analyzed
i
r
*Average value for wheel where collective took place.
9-26
-------
Table 9-18 - Summary of Asbestos Analytical Results (Vehicle Test 3)
(Weight Percent)
SCHEDULE
Burnish
A.B.
Baseline
Detroit
Traffic
10-Stop
Fade
A.F.
Baseline
15-Stop
Fade
Final
Baseline
COLLECTOR
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Average
FRONT BRAKES
RIGHT
(SHROUDED)
0.218
0.101
0.099
(0.109)*
0.106
0.024
0.125
(0.085)
0.018
0.013
0.025
(0.019)
0.045
0.041
0.055
(0.047)
0.158
0.073
0.047
(0.093)
0.109
0.047
0.035
(0.064)
0.089
0.087
0.037
(0.071)
0.070
LEFT
(NORMAL)
Cumulative
Sample
i
'
Not
Analyzed
Average
REAR BRAKES
RIGHT
(SHROUDED)
0.063
0.046
0.060
(0.056)
0.063
0.056
0.044
(0.054)
0.046
0.057
0.037
(0.047)
0.102
0.055
0.014
(0.057)
0.034
0.022
0.003
(0.019)
0.065
0.025
0.014
(0.035)
0.512
0.237
0.035
(0.261)
0.074
LEFT
(NORMAL)
Cumulative
Sample
1
1
0.026
0.031
-
-
*Average value for wheel where collection took place.
9-27
-------
• The data for vehicle test 2 showed slightly lower emissions
than for vehicle test 1 (Test 2 started with smoother used rotor
surfaces. )
9.3.2 Battelle Analyses
The contractual requirements for the asbestos particle size
distribution in addition to the asbestos content placed undue burden on
the accuracy of the asbestos content calculation. To provide a systematic
independent check on the asbestos emissions analyses, the EPA Project
Officer arranged a second contract for Battelle Columbus Laboratories
to analyze 24 samples generated by the program. The analytical method
used by Battelle was developed for EPA under a separate contract. The
method is outlined in Appendix H.
The Battelle results are given in Appendix H. Mr. Carl
Melton was the Battelle Technical Contact.
9.3.3 Johns-Manville Analyses
During the course of the program, Johns-Manville volunteered
to analyze three samples from the program using an analytical procedure
which they had developed for the determination of low asbestos contents
in brake wear debris. Drs. Sidney Spiel and James Leineweber conducted
these tests. The results are given in Appendix H.
9.3.4 Comparison of Asbestos Analytical Results
Table 9-19 gives the comparative data for the asbestos
analytical results obtained by the program, Battelle, and Johns-Manville.
The three Johns-Manville results agreed with the Battelle data as expected.
In 19 of the 24 analyses, the program results were higher
for asbestos percent than the corresponding data from Battelle. The five
Battelle results that were larger than the corresponding program results
were larger by the following factors: 7.5, 2.6, 2.1, 2.1, and 1.2.
There were three program results larger than the corresponding Battelle
results by a factor of less than 1.5. Of the remaining 16 comparative
sets of data, two program results were greater by a factor in the range
1.5 to 2.5, eight program results were greater by a factor in the range
2.5 to 10, and six program results were greater by a factor in the range
10 to 100. The program average was 0.25 percent, while the Battelle
average was 0.17 percent, or 68 percent of the Program average.
The program data were expected to be higher for the follow-
ing reasons :
• All fibers found were assumed to be cylinders of projected
diameter and length as indicated by microscopy. A fiber with
an elliptical cross section will actually be smaller in volume
than that reported.
aSSUmed to be 10° Percent asbestos. Par-
degraded asbestos fibers are similar to asbestos and were
counted. Thxs is especially true for the larger fibers.
9-28
-------
Table 9-19 - Comparison of Analytical Results for Asbestos
Vehicle
Test 1
Vehicle
Test 2
Vehicle
Test 3
Schedule
Detroit
Traffic
10-Stop
Fade
Burnish
Detroit
Traffic
Detroit
Traffic
Collector
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Sump
Surfaces
Airborne
Averages
Front Disc Brakes
Program
0.247
0.137
0.052
0.463
0.254
0.402
0.186
0.304
0.234
0.018
0.025
0.204
JM
0.005
-
-
—
-
-
Battelle
0.21
0.011
0.001
1.22
0.31
0.28
0.10
0.62
0.006
0.135
0.016
0.265
Rear Drum Brakes
Program
0.129
0.373
0.092
0.280
0.132
0.484
1.416
0.249
0.113
0.115
0.046
0.037
0.289
JM
0.002
0.006
—
—
-
-
-
Battelle
0.025
0.006
0.001
0.22
0.007
0.10
0.38
0.057
0.061
0.015
0.010
0.044
0.077
Clutch
Program
0.291
-
-
-
-
-
Battelle
0.007
-
-
-
~
-
VO
VO
Program Average: 0.25
Battelle Average: 0.17
Ratio: Battelle/Program =0.69
-------
• Other analytical techniques rely on reducing all asbestos to
its fibril nature where dimensions and structure are well
characterized. At the same time, all olivine and partially
degraded asbestos are mechanically reduced to a nonfibrous
nature so that only the stronger asbestos fibrils that remain
are counted.
9.4 ASBESTOS EMISSIONS FACTORS
To compare the generation of asbestos emissions properly on a
mass-weighted basis, it was found necessary to calculate the asbestos
emissions factors in weight and in weight per mile. These weights of
asbestos emissions were obtained by multiplying the weight of brake wear
debris generated (Tables 9-9, 9-10, or 9-11) by the appropriate asbestos
percent determined for that weight of debris produced (Tables 9-16, 9-17,
or 9-18). These data are expressed in mg in Tables 9-20, 9-21, and 9-22.
Example:
Vehicle Test 2
Burnish
Right Front Brake ^ Sample
Sump
From Table 9-10:
Weight of sample collected: 0.109 gm
From Table 9-17:
Asbestos weight percent: 0.402
Data given in Table 9-21:
0.10 gm x 1000 2S. x 0.00402 = 0.438 mg
gm &
Using the mileages reported in Table 9-4, the asbestos emission in Mg per
mile are given in Tables 9-23, 9-24, and 9-25.
Example:
Sample same as that used in above example.
From Table 9-21:
Asbestos weight produced for entire test: 0.438 mg
From Table 9-4:
Mileage for Burnish Sequence of vehicle test 2: 127 miles
Data given in Table 9-24:
0.438 mg x 1000 M v 127 miles = 3.45 yg/mlle
9-30
-------
Table 9-20 - Weight of Asbestos Generated During Braking
(Vehicle Test 1) (mg)
SCHEDULE
Burnish
A.B.
Baseline
Detroit
Traffic
10-Stop
Fade
A.F.
Baseline
15-Stop
Fade
Final
Baseline
COLLECTOR
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
FRONT BRAKES
RIGHT
(SHROUDED)
1.160
1.640
0.088
2.888
0.137
0.340
0.377
0.854
0.497
2.754
0.123
3.374
2.685
1.963
0.080
4.728
1.253
8.943
0.347
10.543
3.708
91.998
0.210
95.916
0.670
8.748
0.626
10.044
LEFT
(NORMAL)
No
Anal1
i
t
yzed
r
REAR BRAKES
RIGHT
(SHROUDED)
N/A
10.121
0.161
10.282
0.331
2.449
0.242
3.022
0.562
15.114
0.262
15.938
1.039
0.022
1.061
0.251
1.578
0.024
1.853
0.257
0.009
0.266
0.567
1.426
0.004
1.997
LEFT
(NORMAL)
No
Anal
1
16.
2.
18.
3.
1.
4.
t
yzed
p
350
315
665
180
143
323
Not
Analyzed
0.
0.
798
798
Not
Analyzed
9-31
-------
Table 9-21 - Weight of Asbestos Generated During Braking
(Vehicle Test 2) (mg)
SCHEDULE
Burnish
A.B.
Baseline
Detroit
Traffic
10-Stop
Fade
A.F.
Baseline
15-Stop
Fade
Final
Baseline
COLLECTOR
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
FRONT BRAKES
RIGHT
(SHROUDED)
0.438
4.190
0.026
4.654
0.116
1.495
0.032
1.643
0.127
15.620
2.510
18.237
0.415
3.755
0.024
4.194
0.160
1.932
0.177
2.269
0.117
4.250
0.094
4.461
0.051
0.851
0.044
0.946
LEFT
(NORMAL)
Nc
Anal
i
>t
.yzed
1
REAR BRAKES
RIGHT
(SHROUDED)
0.508
2.350
0.035
2.893
0.217
0.584
0.028
0.829
3.108
4.705
0.064
7.877
-0.430
8.190
0.019
7.779
-0.672
1.775
0.007
1.110
-0.031
0.246
0.004
0.229
0.847
0.074
0.921
LEFT
(NORMAL)
Nc
Ana!
\
)t
Lyzed
9-32
-------
Table 9-22 - Weight of Asbestos Generated During Braking
(Vehicle Test 3) (mg)
SCHEDULE
Burnish
A.B.
Baseline
Detroit
Traffic
10-Stop
Fade
A.F.
Baseline
15-Stop
Fade
Final
Baseline
COLLECTOR
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
T otal
Sump
Surfaces
Airborne
Total
FRONT BRAKES
RIGHT
(SHROUDED)
0.264
0.412
0.045
0.721
0.282
0.263
0.173
0.718
0.037
0.490
0.124
0.651
0.197
0.211
0.103
0.511
0.052
1.014
0.154
1.220
0.426
1.445
0.141
2.012
0.093
2.488
0.125
2.706
LEFT
(NORMAL)
Cumul
Sam
1
ative
pie
r
Not
Analyzed
REAR BRAKES
RIGHT
(SHROUDED)
0.201
0.946
0.020
1.167
0.135
0.691
0.023
0.849
0.174
0.658
0.010
0.842
0.154
0.136
0.002
0.292
0.040
0.065
0.002
0.107
0.057
0.046
0.003
0.106
1.260
5.422
0.006
6.688
LEFT
(NORMAL)
Cumul
Sam
1
ative
pie
\
0.253
0.591
0.844
9-33
-------
Table 9-23 - Weight of Asbestos Generated During Braking
(Vehicle Test 1) (yg/mile)
Schedule
Burnish
A.B.
Baseline
Detroit
Traffic
10-Stop
Fade
A.F.
Baseline
15-Stop
Fade
Final
Baseline
Collector
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Front Brakes
Right
(Shrouded)
6.77
9.42
0.51
16.70
0.04
1.04
1.15
2.23
0.35
1.91
0.09
2.35
57.13
41.77
1.70
100.60
3.52
25.12
0.97
29.61
78.89
1957.40
4.47
2040.76
1.90
24.85
1.78
28.53
Left
(Normal)
No
Ana]
,
t
yzed
r
Rear Brakes
Right
(Shrouded)
N/A
58.11
0.92
59.09
1.01
7.47
0.74
9.22
0.39
10.50
0.18
11.07
22.11
0.47
22.58
0.71
4.43
0.07
5.21
5.47
0.19
5.66
1.61
4.05
0.01
5.67
Left
(Normal)
Nc
Ana!
\
)t
.yzed
1
13.52
1.61
14.13
67.85
24.35
92.20
No
Anal
i
t
yzed
>
9-34
-------
N
Table 9-24 - Weight of Asbestos Generated During Braking
(Vehicle Test 2) (yg/mile)
SCHEDULE
Burnish
A.B.
Baseline
Detroit
Traffic
10-Stop
Fade
A.F.
Baseline
15-Stop
Fade
Final
Baseline
COLLECTOR
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
FRONT BRAKES
RIGHT
(SHROUDED)
3.45
32.70
0.20
36.35
0.33
4.29
0.09
4.71
0.09
10.92
1.74
12.75
7.83
70.85
0.45
79.13
0.47
5.70
0.52
6.69
1.48
53.85
1.19
56.52
0.16
2.61
0.14
2.91
LEFT
(NORMAL)
Not
Analyzed
i
V
REAR BRAKES
RIGHT
(SHROUDED)
4.63
18.52
0.28
23.43
0.62
1.68
0.08
2.38
2.17
3.29
0.04
5.50
- 8.22
154.50
0.36
146.64
-1.98
5.24
0.02
3.28
-0.39
3.11
0.05
2.77
9 fiO
0.23
2.83
LEFT
(NORMAL)
Not
Analyzed
I
1'
9-35
-------
Table 9-25 - Weight of Asbestos Generated During Braking
(Vehicle Test 3) (yg/mile)
SCHEDULE
Burnish
A.B.
Baseline
Detroit
Traffic
10-stop
Fade
A.F.
Baseline
15-Stop
Fade
Final
Baseline
COLLECTOR
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
Sump
Surfaces
Airborne
Total
FRONT BRAKES
RIGHT
(SHROUDED)
. 2.64
4.12
0.45
7.21
0.77
0.72
0.47
1.96
0.03
0.36
0.09
0.48
3.40
3.64
1.78
8.82
0.15
2.94
0.44
3.51
7.22
24.49
3.20
34.91
0.27
7.25
0.36
7.88
LEFT
(NORMAL)
Cumulative
Sample
V
Not
Analyzed
REAR BRAKES
RIGHT
(SHROUDED)
2.01
9.46
0.20
11.67
0.04
1.88
0.06
1.98
0.13
0.49
0.01
0.63
2.66
2.34
0.03
5.03
0.12
0.19
0.01
0.32
0.97
0.78
0.05
1.80
3.67
15.81
0.02
19.50
LEFT
(NORMAL)
Cumulative
Sample
v
0.10"
0.22
9-36
-------
The data for the clutch emissions are given in Table 9-26. During
vehicle test 1 and the early stages of vehicle test 2, it was decided
to combine the very small airborne samples collected as indicated in
Table 9-19. The treatment of the data to arrive at the asbestos emis-
sions in ug/mile was similar to that for the brake emissions given
earlier.
9.5 ASBESTOS EMISSIONS TRENDS
9.5.1 New versus Burnished Materials
The comparison of the Burnish, A.B. Baseline, and Detroit
Traffic Test overall asbestos emissions data is given in Table 9-27.
Both the right front disc brake and the right rear drum brake show that
the asbestos emissions generated during the Burnish schedule are higher
for the new friction materials. Asbestos emissions decrease for slightly
used materials during the A.B. Baseline schedule. The asbestos emissions
increase slightly with increased use as shown with the Detroit Traffic
test.
The rear drum brake data showed two effects brought out by
the vehicle test scheduling and material selections:
• The data above indicate that the Detroit Traffic asbestos
emissions are higher than for the A.B. Baseline. This effect
is probably due to the extent of conditioning of the lining
prior to each test. The Burnish duty is slightly heavier than
the A.B. Baseline duty and this may be responsible for the dif-
ferences between the A.B. Baseline and the Detroit Traffic
results, even though both latter tests are identical in duty.
• Vehicle test 2 used the same linings as vehicle test 1. The
Burnish, A.B. Baseline, and Detroit Traffic schedules showed
lower asbestos emissions than vehicle test 1. The data demon-
strate that asbestos emissions decrease with increased lining
life.
The amount of clutch airborne wear debris collected for
vehicle test 2 was less than for vehicle test 1. The progression through
vehicle test 3 would have continued, except for the fact that several
severe clutch applications and clutch slippages were made to increase
the amount of debris to simulate generation of emissions under more se-
vere conditions. In spite of this practice, the asbestos percent of
the debris and the airborne asbestos emissions content for the clutch
samples decreased with use as shown in Figure 9-3.
9.5.2 Disc Versus Drum Brake Materials
The data given in Table 9-27 also indicate the following
trends:
• For all moderate-duty schedules, the drum brakes produced more
total emissions than the disc brake.
9-37
-------
Table 9-26 - Summary of Clutch Asbestos Emissions
SAMPLE
AIRBORNE
SURFACES
SUMP
VEHICLE
TEST
1
2
3
SCHEDULE
Burnish
A.B. Baseline
Detroit Traffic
10-Stop Fade
A.F. Baseline
15-Stop Fade
Final Baseline
Burnish
Cumulative
(A.B. Baseline
To Final Baseline)
Cumulative
(Burnish to
Final Baseline)
Cumulative for all
3 Vehicle Tests
Cumulative for all
3 Vehicle Tests
WEAR DEBRIS
WEIGHT
0.0005
0.0042
0.0097
0.0001
0.0009
0.0003
0.0040
0.0004
0.0058
0.0126
1.9519
14.8472
ASBESTOS
WEIGHT
PERCENT
N/A
N/A
0.291
0.493
N/A
0.136
0.035
0.099
0.047
ASBESTOS
(Mg)
0.028
0.026
0.008
0.004
1.930
6.990
ASBESTOS
(ug/mile)
0.019
0.032
(0.023)
0.003
0.001
0.239
0.864
Table 9-27 - Comparison of Asbestos Emissions from New and
Burnished Materials
Location
RIGHT
FRONT
DISC
BRAKE
RIGHT
REAR
DRUM
BRAKE
Vehicle
Test
1
2
3
Totals
1
2
3
™— — W.HH^__
Burnish
(ug/mile)
16.70
36.35
7.21
60.26
59.09
24.43
11.67
94.19
.
A,B. Baseline
(ug/mile)
2.23
4.71
1.96
8.90
9.22
2.38
1.98
13.58
Detroit
Traffic
(Mg/mile)
2.35
12.75
0.48
15.58
11.07
5.50
0.63
17.20
*~" ^^^^V^^^^M
Burnish
A.B. Baseline
7.5
7.7
3.7
Average: 6.3
6.4
10.3
5.9
Average: 7.5
Burnish
A.B.B. + D.T.
2
7.3
5.3
9.2
Average : 7.3
5.8
7.3
Average: 8.8
9-38
-------
1.00-1
0.8CH
in
o
Is °-6°'
ffi
LU
u
-------
VO
Table 9-28 - Asbestos Emission from Heavy-Duty Tests
Location
Right
Front
Disc
Brake
Right
Rear
Drum
Brake
Vehicle
Test
1
2
3
Totals
1
2
3
Totals
10-Stop Fade
(ug/mile)
100.60
79.13
8.82
188.55
22.58
146.64
5.03
174.25
A.F. Baseline
(ug/mile)
29.61
6.69
3.51
39.81
5.21
3.28
0.32
8.81
15-Stop Fade
(ug/mile
2040.76
56.52
34.91
2132.29
5.66
2.77
1.80
10.23
Final Baseline
(ug/mile)
28.53
2.91
7.88
39.32
5.67
2.83
19.50
28.00
10-Stop Fade
Detroit Traffic
42.8
6.2
18.3
Average: 22.4
2.0
26.7
8.0
Average: 12.2
-------
The following trends are noteworthy:
• The right front brake emissions were higher than the correspond-
ing rear brake results as only the front brake experienced the
true fade temperatures because of the brake designed balance.
• The 15-Stop Fade total emissions for the front brake were higher
than for the 10-Stop Fade total, again because of the higher
temperatures experienced, as compared to the 10-Stop Fade.
• The A.F. Baseline and Final Baseline total emissions were higher
than the corresponding A.B. Baseline total given in Table 9-25
by a factor of approximately 4.4 for the front brake.
• The right rear drum brake show higher emissions for the 10-Stop
Fade than for the 15-Stop Fade due to a shift in duty to the
rear brakes as the front brakes fade during their first heavy-
duty experience.
The above total-wheel asbestos emission trends indicate that
there is a rise in total asbestos emissions produced with high temperature
use. This trend was only partially reflected in a slight asbestos percent
increase indicated earlier in Tables 9-16, 9-17, and 9-18. The greatest
portion of the asbestos emissions increase was due mainly to the largdr-
than-normal amount of wear debris produced during and after the heavy
duty and high temperatures experienced by the friction materials, as indi-
cated in Tables 9-9, 9-10, and 9-11, and considering the mileages for
each schedule.
The following observation was also noteworth in the compari-
son of moderate and heavy-duty tests:
• The ratio of asbestos emissions for the 10-Stop Fade to Detroit
Traffic Tests (far right column of Table 9-27) was higher than
the ratio of asbestos emissions for the Burnish to A.B. Baseline
plus Detroit Traffic test average (far right column of Table
9-26). The order of decreasing asbestos emissions from brakes
can be summarized:
Fade (or heavy-duty stops)
I Decreased
Burnish I Asbestos
A.B. Baseline + Detroit Traffic jf Emissions
(moderate driving)
9.5.4 Effects of Friction Materials
The data for the asbestos emissions were rearranged for
each brake as shown on Table 9-29. This is the best way to compare the
results due to the different friction materials. The following trends
were noted:
9-41
-------
Table 9-29 - Comparison of Asbestos Emission Generated by Different
Friction Materials
Duty
Moderate
Heavy
to
Abusive
Schedule
Burnish
A. B. Burnish
Detroit Traffic
Totals
10-Stop Fade
A. F. B seline
15-Stop Fade
Final Baseline
Totals
Asbestos Emissions (tag/mile)
Vehicle Test 1
Front
16.70
2.23
2.35
21.28
100.60
29.61
2040.76
28.53
2199.50
. Rear
59.09
9.22
11.07
79.38
22.58
5.21
5.66
5.67
39.12
Vehicle Test 2
Front
36.35
4.71
12.75
53.81
79.13
6.69
56.52
2.91
145.25
Rear
23.43
2.38
5.50
31.31
146.64
3.28
2.77
2.83
155.52
Vehicle Test 3
Front
7.21
1.96
0.48
8.65
8.82
3.51
34.91
7.88
55.12
Rear
11.67
1.98
0.63
13.98
5.03
0.32
1.80
19.50
26.75
ESTIMATED VARIATION
ON ESTIMATE OF INITIAL
ASBESTOS CONTENT.
60 65
ASBESTOS CONTENT (WT %)
70
CO
01
Figure 9-4 -
Variation of Asbestos Emissions During Moderate Duty
With Asbestos Content of Disc Pads
9-42
-------
• For the disc pads, there was an increase in asbestos emissions
for increases in pad asbestos content:
Estimated
Vehicle Asbestos Asbestos
m n Emissions
Test Content . .
(Weight percent) (.jag/mile)
3 60 8.65
1 65 21.28
2 70 53.81
These data are plotted in Figure 9-4 and show an almost linear
relationship, predicting a zero asbestos emission content when
the pad asbestos content falls below 55 weight percent.
• There was no such trend for the drum brake data.
• Both the disc pads and the drum linings of vehicle test 3 showed
the lowest asbestos emissions of all three tests. Both the disc
pads and the secondary linings contained brass chips which may
have been responsible for the almost complete conversion of the
asbestos in the brake emissions of the respective wheels.
9.5.5 Airborne versus Sump versus Surfaces Samples
The comparisons of the asbestos emissions found in the sump,
surfaces and airborne sample locations can be determined from the data
given in Table 9-30. The data can be summarized and compared (Table 9-31):
Front Disc Brake Trends
• For the moderate-duty tests, the airborne asbestos emissions
were 6.12 percent of the total emissions. The surface samples
contributed 76.80 percent while the sump samples were 17.02
percent.
• For the heavy-duty tests, and as a result of the severely
burnished rubbing surfaces, the airborne asbestos emissions
were only 0.71 percent and the sump samples 6.71 percent as
the surfaces samples increased to 92.58 percent.
Rear Drum Brake Trends
• For the moderate tests, the airborne asbestos emissions were
2.00 percent of the total emissions. The surfaces samples
contributed 88.28 percent while the sump samples were 9.72
percent.
9-43
-------
Table 9-30 - Comparison of Asbestos Emissions for Various Sample
Locations (ug/mile)
Duty
Moderate
Heavy
or
Abusive
Vehicle
Test
1
2
3
1
2
3
Schedule
Burnish
A. B. Baseline
Detroit Traffic
Burnish
A. B. Baseline
Detroit Traffic
Burnish
A. B. Baseline
Detroit
Averages :
10-Stop Fade
A. F. Baseline
15-Stop Fade
Final Baseline
10-Stop Fade
A. F. Baseline
15-Stop Fade
.Final Baseline
10-Stop Fade
A. F. Baseline
15-Stop Fade
Final Baseline
Averages :
Front Disc Brake
Sump
6.77
0.04
0.35
3.45
0.33
0.09
2.64
0.77
0.03
1.61
57.13
3.52
78.69
1.90
7.83
0.47
1.48
0.16
3.40
0.15
7.22
0.27
13.52
Surfaces
9.42
1.04
1.91
32.70
4.29
10.92
4.12
0.72
0.36
7.28
41.77
25.12
1957.40
24.85
70.85
5.70
53.85
2.61
3.64
2.94
24.49
7.25
185.04
Airborne
0.51
1.15
0.09
0.20
0.09
1.74
0.45
0.47
0.48
0.58
1.70
0.97
4.47
1.78
0.45
0.52
1.19
0.14
1.78
0.44
3.20
0.36
1.42
Rear Drum Brake
Sump
N/A
1.01
0.39
4.63
0.62
2.17
2.01
0.04
0.13
1.38
—
0.71
—
1.61
—
1.30
2.66
0.12
0.97
3.67
1.58
Surfaces
58.11
7.47
10.50
18.52
1.68
3.29
9.46
1.88
0.49
12.38
22.11
4.43
5.47
4.05
154.50
5.24
3.11
1.30
2.34
0.19
0.78
15.81
18.28
Airborne
0.92
0.74
0.18
0.28
0.08
0.04
0.20
0.06
0.01
0.28
0.47
0.07
0.19
0.01
0.36
0.02
0.05
0.23
0.03
0.01
0.05
0.02
0.13
9-44
-------
Table 9-31 - Summary Comparison of Surfaces,
Sump, and Airborne Samples
BRAKE SYSTEM
Disc Brake
Moderate Duty
Heavy Duty
Drum Brake
Moderate Duty
Heavy Duty
Average (wt)
SUMP
(ug/mile)
1.61
(17.02)*
13.52
(6.71)
1.38
(9.72)
1.58
(7.90)
4.52
(7.33)
SURFACES
(ug/mile)
7.28
(76.86)
185.04
(92.58)
12.38
(88.28)
18.28
(91.45)
55.75
(91.68)
AIRBORNE
(ug/mile)
0.58
(6.12)
1.42
(0.71)
0.28
(2.00)
0.13
(0.65)
0.60
(0.99)
fc
Data in parentheses are the percents of the total
samples for the condition considered.
9-45
-------
• For the heavy-duty tests, and as a result of redistribution of
the sump sample, the airborne asbestos emissions were only
0.65 percent and the sump samples 7.90 percent as the surfaces
samples increased to 91.45 percent.
9.6 CHANGES IN LINING WEAR RATE AFTER USE AT HIGHER TEMPERATURES
One of the goals of the project was to ascertain the changes in
lining wear rate and the corresponding asbestos contents after precon-
ditioning at elevated temperatures. The lining wear changes are given
in Table 9-32.
The A.B. Baseline schedule (and the other Baselines) consisted of
a three-day Detroit Traffic driving test. The Detroit Traffice schedule
consisted of twelve days of the same road pattern. Thus one-fourth of
the Detroit Traffic schedule was equivalent to the A.B. Baseline schedule.
The data for the front brakes showed good consistency for each of these
schedules. The data for the rear brakes showed wider variations.
The A.F. Baseline and Final Baseline schedules were run after the
10- and 15-Stop Fade schedules followed by a Reburnish schedule. The
right front brake indicated >550°F during the fades and had a wear
factor approximately 250 percent greater than the one-fourth Detroit
Traffic schedule. The left front brake indicated only 300-370°F during
the 10-stop fade (due to increased intervals) and had a wear factor
approximately 120 percent greater than the A.B. Baseline and the one-
fourth Detroit Traffic schedules.
9.7 RESULTS OF GASEOUS EMISSIONS ANALYSES
9.7.1 Summary of Analytical Methods Attempted
Analysis of the gaseous emissions was made difficult by
the large quantities of water and carbon dioxide present in the samples.
Calculations were made which indicated that the flow through the rotating
seals was approximately 0.5 to 0.7 percent of the total. Even when
gaseous emissions collections were made during their peak formation such
as the fade tests, sufficient quantities of untreated air entered through
the rotating seals (downstream of the Drierite and calcium oxide) to
present serious analytical interferences.
Several different analytical schemes were used and proved
only partially successful. Initially, the entire contents of the char-
coal ^ gas traps were condensed in the gas handling system described in
Section 8.5.2. Traps cooled with acetone-dry ice and LN2 were employed.
The noncondensable gases proved to be essentially 100 percent air; no
other gases could be detected except for a small amount of C02. When
all this gas was pumped away and the LN2 removed, the trap was found to
contain 100 percent C02. In one instance, the C02 vapor pressure built
up so fast that a stop-cock barrel was shot out of the system. In
attempts to trap heavier gases and reduce the danger of a high pressure
9-46
-------
Table 9—32 - Change in Lining Wear Rate After Operation at Increased
Temperatures
SCHEDULE
A.B.
BASELINE
DETROIT
TRAFFIC
(*4)
A.F.
BASELINE
FINAL
BASELINE
Vehicle
Test
No.
1
2
3
Avg.
1
2
3
Avg.
1
2
3
Avg.
1
2
3
Avg.
Miles
328
348
368
358
357
343
356
339
347
353
326**
352
Stops
682
483
520
562
570
750
480
542
843
594
**
464
352
Pedal
Appl.
1382
1330
1370
1412
1375
1507
1432
1045
1298
1444
**
1202
1433
FRONT BRAKES
RIGHT
(SHROUDED)
Max.
Temp
(°F)*
310
320
330
360
330
300
-v-550
550
520
^625
600
560
Wear
Per Stop
(Mg)
2.73
2.38
5.40
3.50
2.53
1.80
1.67
2.00
6.95
5.12
2.50
4.86
6.28
4.07
4.87
5.07
LEFT
(NORMAL)
Max.
Temp.
(°F)
170
240
170
170
210
150
360
370
300
275
310
330
Wear
Per Stop
(Mg)
1.89
2.30
2.68
2.29
1.87
1.55
1.67
1.70
2.37
2.36
1.39
2.04
2.06
1.47
2.91
2.15
REAR BRAKES
RIGHT
(SHROUDED)
Max.
Temp.
(°F)
220
200
240
260
180
240
375
290
370
325
280
430
Wear
Per Stop
(Mg)
1.20
2.50
3.64
2.45
2.63
2.33
0.61
1.86
2.12
0.52
0.73
1.12
0.83
***
1.42
1.13
LEFT
(NORMAL)
Max.
Temp.
(°F)
170
240
180
180
240
150
340
320
320
285
260
330
Wear
Per Stop
(Mg)
1.78
2.42
1.54
1.91
2.26
1.83
1.55
1.88
4.95
1.76
1.59
2.77
1.90
1.79
1.73
1.81
VO
Before Test
Data for only 11 circuits.
Brake fluid in friction materials - no result.
-------
build-up, the C02 was allowed to evaporate into the vacuum after the
LN2 trap was replaced with acetone-dry ice. The final fraction proved
to be mainly C02 and water with traces of hydrocarbons.
An attempt to eliminate C02 and 1^0 was made by passing
the gases from the charcoal traps through Drierite and calcium oxide
traps placed between the gas handling and the gas collection systems.
This proved partially successful.
The traces of gases obtained gave only small peaks in gas
chromatography with the thermal conductivity detector (T.C.D.). This
problem was overcome by employing the flame ionization detector (F.I.D.)
for the hydrocarbon analyses. However, all attempts proved fruitless
in detecting anything other than minor amounts of C^'s to C%'s. Because
of all of these difficulties, it was decided to minimize the effort
devoted to future gas analyses.
In a last attempt to detect gaseous emissions products the
gas collection system was connected directly to the gas injector of the
gas chromatograph and the sample was analyzed simultaneously with both
T.C.D. and F.I.D. This method proved successful for the fade test
products. Although the T.C.D. detected only the major inorganices, the
F.I.D. gave several peaks discussed in the following section. This
method indicated that the initial tests with T.C.D. alone did not have
adequate sensitivity for the organic products in the C^-Cj range where
the entire test was sampled. The major drawback of this revised method
of direct injection is that it is impossible to analyze the total
volume of products obtained.
9.7.2 Gaseous Emissions Detected
Table 9-33 lists the data from the analysis of the gaseous
emissions from vehicle test 1 while Table 9-34 lists the data from
vehicle tests 2 and 3.
For vehicle test 1, the activated-charcoal gas traps from
the Burnish and Detroit Traffic tests showed traces of C± to C4 hydro-
carbons in large quantities of air, carbon dioxide, and water (Table 9-33).
No other materials could be found.
For the 10-Stop Fade test, the initial gases released from
the traps again showed traces of Cx to C4 hydrocarbons when analyzed.
The traps were then connected directly to the gas chromatrograph (G.C.)
as described in the previous section. The charcoal gas trap samples from
the right front brake, 10-Stop and 15-Stop Fade schedule of all vehicle
tests were analyzed with a Porapak column. At times, the large amount
of air and CC>2 gave slightly earlier than normal elution times as compared
to the calibration blend. The same sample was also run on a W-98 sili-
cone gum rubber column. Table 9-35 lists the elution order of different
compounds from the Porapak column. The table llgts fche compounds used
tor calibration, those detected, and possible compounds whose elution
occurs between the calibration compounds. Table 9-36 lists the elution
9-48
-------
Table 9-33 - Data From Analysis of Gaseous Emissions (Vehicle Test 1)
Schedule
Burnish
Detroit
Traffic
10-Stop
Fade
A. F.
Baseline
15-Stop
Fade
Final
Baseline
Front Disc Brake
Charcoal
Traps
Much C02 ,
air, H20,
trace CE^
Much C02,
air, H20
trace 014
64 to C8's:
benzene,
toluene,
phenol, and
cresols
Not
sampled
Low M.W.
C4-C6
Not
sampled
Condensable
Gas Trap
Water
Water
Not
sampled
1 Peak
, MW ~Cj4
Not
sampled
Rear Drum Brake
Charcoal
Traps
Much CO 2 >
air, H20,
trace Ctfy
Trace CH4,
C3H8,
i-C4H10
C02, Air, H20
CH4, C3H8,
i-C4Hio , and
high M.W.'s*
Not
sampled
C02, Air, H20
Not
sampled
Condensable
Gas Traps
Water
Water
Water
Not
sampled
Water
Not
sampled
Clutch
Charcoal
Traps
Much C02,
air, H20
trace CIfy, C2H6,
C3H8, C4Hl0's
Much C02,
air, H20
trace CH4, C2H6
Much C02
air, H20
Not
sampled
Much C02
air, H20
trace CH4
Not
sampled
VO
*M.W. = Molecular Weight
-------
Table 9-34 - Data From Analysis of Gaseous Emissions (Vehicle
Tests 2 and 3)
Schedule
Vehicle Test 2
Vehicle Test 3
A.B.
Baseline
Detroit
Traffic
10-Stop
Fade
15-Stop
Fade
Burnish
Detroit
Traffic
10-Stop
Fade
15-Stop
Fade
Front Disc Brake
Charcoal
Traps
C02, air
H20,
trace CE^
Benzene,
tolueme,
up to
cardanol
Some high
M.W.* peaks
Some high
M.W. peaks
C02, Air,
H20,
trace City
C02, Air,
H20,
trace City plus
high M.W. peaks
Some high
M.W. peaks
Some high
M.W. peaks
Condensable
Gas Trap
Nc
ana]
1
^
>t
.yzed
r
r
Rear Drum
Charcoal
Traps
CO 2, air
H20,
trace City
C02, air
H20,
trace C-^ to CQ
Some high
M.W. peaks
C02, air, H20
trace City
C02, H20, air
C2H6 + C2H6
+ traces C^ to
C8
Not
analyzed
I
Brake
Condensable
Gas Traps
N
ana
i
ot
lyzed
r
1
*M.W. = Molecular Weight
9-50
-------
Table 9-35 - Elution Order From Porapak Q
Air
Carbon monoxide
Methane
Carbon dioxide
Ethane
Water
Propane
Methanol
Formaldehyde
Acetaldehyde
Butane
Ethanol
Propylene oxide
Propionaldehyde
Acetone
Isopropanol
Acetic acide
Methyl acetate
Propanol
Pentane
Isobutraldehyde
Butraldehyde
2-Butanone
Methyl-ethyl ketone
Ethyl acetate
Isobutanol
Hexane
Butanol
Benzene
C7+
Calibrant
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Detected
X
X
X
X
X
X
X
X
X
X
X
X
Possible
X
X
X
X
9-51
-------
Table 9-36 - Elution Order From W-98
Pentane
Benzene
Toluene
m+p-Xylene
o-Xylene
Benzaldehyde
Phenol
l,2,3TM-Benzene
Indene
o-Cresol
m-Cresol
2,6DM-Phenol
l,2,3,5TM-Benzene
2,4DM-Phenol
n-Dodecane
n-Hexadecane
Calibrant
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Detected
X
X
X
X
X
X
X
Possible
X
X
X
X
9-52
-------
order of different compounds from the W-98 column. The table lists the
compounds used for calibration, those detected, and other possible com-
pounds 'expected.
9.7.3 Shroud Extract Analysis
During normal fade tests, a dark brown cloud of high mole-
cular weight organics with a pungent odor appeared after the seventh
to fifteenth fade stops for each front brake. During the 10-Stop Fade
of vehicle test 1, a cloud was observed for the left front brake only
as the brake shroud prevented any such release for the right front brake.
The inside surface of the shroud was covered with a "tarry" layer which
presented the same pungent odor after all fade tests.
The G.C. chromatogram of the shroud extracts from the 10-
Stop and 15-Stop Fade tests of all vehicle tests were chromatographed
on an OV-101 column. The results indicated that the shroud extract
contained organics with molecular weights higher than n-dodecame [mole-
cular weight 170 and boiling point 214°C (420°F)]. Cardanol is present
in all samples.
9-53
-------
SECTION 10
ESTIMATED EMISSIONS FOR CARS AND TRUCKS
10.1 APPROACH
The purpose of this section is to develop an estimate of total
brake and'clutch emissions from the U.S. population of motor vehicles
in use on the roads and highways. Inputs include all of the test re-
sults described earlier in this report, together with a supplementary
data base on U.S. motor vehicle population and usage and on friction
material usage and consumption obtained from other sources.
Because of the uncertainties in all of the data available, emis-
sions can only be considered as a broad range, rather than as a single
value, with the expectation that the true average emissions for both
individual vehicles and the motor vehicle population in general will
be within the range of values calculated below.
10.2 SUPPLEMENTARY DATA BASE
The data base reported in the accompanying tables was obtained
from a wide variety of trade publications and from industry and govern-
ment contacts. Credit is given to the sources of major contributions.
Although they vary considerably in quality, the data are, in general,
adequate for the purpose of estimating total annual emissions, because
emissions themselves can vary so widely from vehicle to vehicle, from
operator to operator, and from locality to locality.
10.2.1 Number of Vehicles in Use
Table 10-1 lists the total U.S. motor vehicle population
as estimated by both Department of Transportation (DOT) (National Highway
Traffic Safety and Federal Highway Administration)(10-1)* and by the
R. L. Polk Company/10-2) ^e Polk census is said to be more precise
because it eliminates multiple registrations of the same vehicle. Polk
considers that DOT estimates may be as much as 13 percent too high. Both
Polk and DOT omit military vehicles, but include all other motor vehicles
that are state-licensed including police cars, school buses and the like.
Independently, the General Services Administration reports that 190,000
Department of Defense vehicles are in use world-wide.
Table 10-2 lists the U.S. braked trailer population and
Table 10-3 lists the U.S. motor vehicles with dry clutches.
*
Numbers in parentheses refer to References at end of section.
10-1
-------
Table 10-1 - U. S. Braked Motor Vehicle Population
Private Passenger Cars
(R.L..Polk Estimate 7-1-71: 83,137,324)
D.O.T. Estimate 7-1-72:
Trucks:
(R.L. Polk Estimate 7-1-71: 18,462,287)
D.O.T. Estimate 7-1-72:
(Includes 897,456 Truck Tractors)
Light
Medium
Heavy
Buses :
Under 6000 Ibs GVW*
6 -10,000
10-14,000
14-16,000
16-19,500
19.5-26,000
26-33,000
Over 33,000
12,109
4,952
125
125
645
1,290
395
1,165
,000
,000
,000
,000
,000
,000
,000
,000
D.O.T. Estimate 7-1-72
Miscellaneous Motor Vehicles: motor cycles,
etc.
D.O.T. Estimate 7-1-72
96,397,000
20,800,000
403,000
3,787,000
Total Motor Vehicles in Use**
D.O.T. Estimate 7-1-72
121,400,000
*Gross vehicle weight; estimates from 1970-71 sales data extended by this study,
**This total includes approximately 1.5 million public vehicles (450,000 cars,
920,000 trucks, and 185,000 buses), but does not include 190,000 Department
of Defense vehicles in worldwide use.
Table 10-2 - U. S. Braked Trailer Population
Class
Recreational
Travel
Camping
Boat
Miscellaneous
(Animal, Utility, etc.)
Commercial
Utility
Trucking
Full
Semi
Number
In Use
1,800,000
1,200,000
2,500,000
1,700,000
1,000,000
278,000
1,552,000
Percent
With
Brakes
95
20
35
80
60
100
100
Number
With Brakes
1,710,000
240,000
875,000
1,360,000
600,000
278,000
1,552,000
6,615,000
10-2
-------
Table 10-3 - U. S. Motor Vehicles With Dry Clutches
Vehicle
Type
Passenger Cars
Domestic
Imported
Trucks and Buses
Light
Medium
Heavy
Number
Of Vehicles
In Use
87,100,000
9,300,000
17,100,000
2,600,000
1,600,000
Percent
Containing
Clutches With
Asbestos
15
90
75
95
100
Number
Of Dry
Clutches
13,064,000
8,370,000
12,900,000
2,470,000
1,600,000
38,404,000
Source: estimate made from industry canvas,
Table 10-4 - Yearly Additions to U. S. Braked Vehicle Population
New Vehicles Placed in Service (Calender Year 1972):
Passenger Cars:
Net U.S. Production
Net Imports
Total
Trucks:
Total (estimated)
9,312,502
1,593,605
Estimate Total:
10,906,107
2,600,000
13,506,107
Source: Wall Street Journal
10-3
-------
The DOT estimate of 117-million total vehicles, including
20.8-million trucks, is probably sufficiently accurate for estimating
brake emissions for 1972. It should be noted that the net growth in
vehicles each year is given approximately by the sum of U.S. cars,
trucks and other vehicles sold plus imports sold (all adjusted for ex-
ports) (Table 10-2) less annual retirement of about six- to seven-
million cars and one-million trucks.(10-3, 10-4, 10-5) The scrappage
rate tends to rise and fall with the sales rate and may well have been
closer to eight-million cars than to seven-million for 1972. Figures
are not yet available.
Assuming a total retirement of nine-million vehicles, the
net growth in vehicles for 1972 was approximately 4.5 million:
10.9 million cars sold
+2.6 million trucks sold
13.5 million total
- 9.0 million scrappage
4.5 million net growth
The net growth in car and truck registrations from 1961 to
1971 averaged 3.12-million vehicles per year and will probably tend to
follow the same patterns over the near future.
10.2.2 Motor Vehicle Usage
Table 10-5 shows the approximate total number of miles
traveled by all U.S. motor vehicles to be 1.249-trillion miles for 1972,
according to a recent DOT estimate (10-1) e fhis total is said to be grow-
ing at a 4.5- to 5.2-percent annual rate. To accomplish this mileage,
about 100 billion gallons of motor fuel were consumed for an overall
average of a little over 12 miles per gallon. The detailed breakdown
of mileage by vehicle type and roadway type (Table 10-6) was adjusted for
1972 total mileage from 1970 DOT data.
Roadway mileage and usage are further identified in Table 10-6
by type of surface and by locale, whether urban or rural. More insight
into vehicle usage is given in Tables 10-7 and 10-8 where motor vehicle
usage is classified by the purpose of the trip and length of the trip.
All of these factors cast light, to some extent, on the degree of vehicle
brake usage and emissions.
10.2.3 Estimates of Brake Usage and Abuse
Brake usage varies widely from gentle to abusive. In the
following paragraphs the term abusive braking will be defined and its
extent will be explored.
10-4
-------
Table 10-5 - Motor Vehicle Usage by Vehicle Type and Roadway
Vehicle
Passenger Cars
Motorcycles and
Motorbikes
Buses :
School
Commercial
Trucks-Total
Single Unit
Trucks
Truck
Combinations
Total-all vehicles
Billions
By Road
Local
Rural
109*
- A
35
33
1.9
150
of Vehicle Miles Traveled
Type and Location*
Main Total
Rural Urban Mileage
337 534 980
10.9
6.
^
119 91 245
88 77 198
31 14 47
464 635 1,249
Mileage Per
Vehicle (1970)
9,978
3,605
13,306
7,274
32,591
11,450
9,807
41,903
10,076
*Blanks indicate insufficient data. Other data are adjusted for 1972 total
analysis from 1970 D.O.T. breakdown on best-estimate basis.
**Weighted total average
Table 10-6 - Type and Usage of Public Roads
Road Type
1.
2.
3.
By Classification
Interstate (42,500 authc
Rural
Urban
Primary-Highways
Rural
Urban
Secondary Highways
Rural
Urban
Municipal Streets
By Location
Rural
Urban
By (Duality
Surfaced
Non-surfaced
Grand Totals
Miles of Road
rized)
30,000
5,000
705,000
2,990,000
3,169,000
561,000
784,000
2.946,000
3,730,000
Billions of
Annual Miles of
Vehicle Travel
(1972 estimate)
117
113
222
153
275
.92
277
1,249
Source: World Almanac, 1973 and
1972 Automobile Facts and Figures; adjusted
10-5
-------
Table 10-7 - Motor Vehicle Usage by Purpose of Trip
Purpose of Trip
Earning a living
(driving to work, etc.)
Family business
Educational
Social
(includes vacations)
Proportion of
Total Use
42.1%
19.6
5.0
33.3
Average
Trip Length
10.2 miles
5.5
4.7
13.1
Table 10-8 - Motor Vehicle Usage by Length of Trip
Length of Trip
(one way)
Under 5 miles
5 -10
10-15
15-20
20-30
30-40
40-50
50-100
Over 100
Percentage of Trips
54.1
19.6
13.8
4.3
4.0
1.6
0.8
1.0
0.8
100.0
Proportion of
Total Use
Miles, Percent
11.1
13.8
18.7
9.1
11.8
6.6
4.3
7.6
17.0
100.0%
Average trip length =8.9 miles
DOT Preliminary Survey 1969-70
10-6
-------
Abusive braking, with the organic-bonded friction materials
used almost universally on motor vehicles today, implies heating the
bulk friction material to temperatures above about 500 to 600°F. At
these temperatures, the phenolic resin binders gradually pyrolyze, weaken,
and become brittle, allowing wear to increase rapidly. Because degrada-
tion is a time-temperature phenomenon, total brake-use history is
important.
Overheating can be caused by one or a combination of the
following:
Dragging brakes caused by system defect or operator error.
Repeated use of brakes to retard the vehicle on a long downgrade.
Repeated high-speed stops.
Maladjustment.
Severe vehicle overloading.
Partial brake system failure, overworking one or more brakes.
The degree of overheating is further influenced by ambient air tempera-
ture, wind velocity and relative direction, air flow around the brake
(design) and use of engine braking to assist the foundation brakes.
In predominantly flat terrain and on most interstate-quality
highways with gentle grades, the need to use brakes to overcome gravity
is minimal. Here, brake overheating is rare and usually comes from
abusive use as in the fade tests carried out under this program.
In very hilly or mountainous regions, overheating can occur
quite easily as was demonstrated by a team of professional test drivers
on cross country runs in 1967. Zechel, et.al.(10-6)} described a study
where a group of professional test drivers drove a total of 44,000 miles
with six 1966 U.S. passenger cars in order to perform an "Automotive
Brake Evaluation Under Customer Usage Conditions." Results of this trip
(see Table 10-9) show that abusive temperatures were reached only in
mountainous regions (and in the hot and hilly Los Angeles traffic for
one disc brake car). Intentionally aggressive braking behavior in
Detroit, St. Louis, New York, and other areas of heavy traffic failed
to produce excessively high brake temperatures.
The proportion of mountain driving mileage on these trips
was as follows: Eastern leg, 7.8% of the total; Western leg, 7.4%, of
which 2.4% was in Los Angeles traffic. Repeated runs were intentionally
made over some of these mountain roads for increased severity of the
test. Because we have shown that total emissions tend to increase with
abusive braking, its prevalence will be explored further.
Table 10-10 gives the results of an attempt to estimate the
proportion of U.S. driving that takes place in predominantly hilly or
mountaninous areas where long steep grades are common. Basic data on
10-7
-------
Table 10-9 - Results of Cross-Country Brake Test Trip
Local
Eastern Trip:
Highway and rural
N.Y. City traffic
Peters and Potts Mountain
Western Trip:
Los Angeles traffic
Other city traffic
Highway and rural
in hilly areas
Rocky Mountains
Maximum Brake Temperatures (°F)
Drum Brakes (4 cars)
Average
Peak
Temperature
250
343
471
421
300
526
Maximum
350
390
580
465
360
410
650
Disc Brakes (2 Cars)
(not used on Eastern Trip)
Car "E"
320
300
300
430
Car "F"
630
410
375
748
Source: SAE Report SP 338 (1967)
*Report covers 44,180 miles of coast-to-coast driving by professional
drivers using 6 different makes of passenger cars. Test were deliberately
aggressive to generate maximum temperatures to check brake fluid boil.
Car "F" ran hotter on the front wheels by more than 300°F compared to the
rear wheels.
Table 10-10 - Where Vehicles Are Used
Estimated Total Annual Usage
Predominantly
Flat Terrain
with
Infrequent, Gentle
Grades
Steep Hills to
Mountainous
with
Frequent, Long,
Steep Grades
Plains States 30, with
79 million vehicles
Partly mountainous States-
20, with 38 million vehicles
Estimated Usage:
70% flat terrain
30% steep grades
Totals
Percent of all
driving
Type of Braking Expected
777 billion miles
328
1,105
88.5%
Normal
Minor Amount
144 billion miles
144
11.5%
Severe to abusive
brake use may be
needed.
Source: Estimate made for this study.
10-8
-------
miles driven in each state are readily available from DOT. The percentage
of driving that takes place in mountainous areas, where abusive brake
use may be necessary, is estimated to be 11.5% of all driving. The esti-
mate is subjective, to a large degree, and may be high, but no better
data have been located.
Table 10-11 lists some additional U.S. driving characteristics
recently gathered by the American Petroleum Institute. Table 10-12 lists
typical numbers of brake applications per mile as measured under this and
other brake programs. It is an illustrative rather than an exhaustive
study of the subject.
Figure 10-1 illustrates the frequency of high-g stops, as
determined at the Highway Safety Research Institute of the University of
Michigan (10-7). This shows that 50 percent of all stops are less than
0.15 g (4.8 fps2), 99 percent are less than 0.36g (11.6 fps2) and 99.9
percent are less than 0.5g (16 fps2). Carpenter^lO-8) confirms one point
on the University of Michigan curve and lends credibility to the data.
10.2.4 Asbestos in Friction Materials
Almost all of the commercial friction materials used for
braking passenger cars and trucks today are based on the unique strength
and thermal stability of natural asbestos (chrysotile) fibers. This has
been true for over fifty years. Table 10-13 shows that the asbestos
content of friction materials averages about 60 percent.
Table 10-14 lists the weights of the brake lining materials
used in this program. They are typical of the weights of friction material
used on passenger cars today and will be considered average for the cal-
culations which follow.
Compilations of data on brake rotors and friction materials
usage appear in Tables 10-15, and 10-16, and 10-17 respectively. Based
on the data in Table 10-16, the total amount of asbestos contained in all
of the automotive brake friction materials sold each year is calculated
to be about 103 million pounds which corresponds to M.18 million pounds
used prior to grinding. The two most knowledgeable sourcesdO-9, 10-10)
report that 90 to 120 million pounds per year are used. A report from
IIT Research Institute suggests that 67 million pounds are used annually
in brake linings(10-11). ^ Bureau of Mines Report (1°-12) based on 1968
data credits only 50 million pounds of asbestos to automotive use, a
number the authors find to be much too small. Ignoring the two latter
values, the three estimates of asbestos contained in linings range from
90 to 120 million pounds. Using the calculated value of 118 million
pounds and assuming a 15-percent grinding and drilling loss, the maximum
amount of asbestos incorporated in brake friction materials is taken to
be 103 - million pounds per year.
A compilation of data on clutch friction materials usage is
given in Table 10-17. Based on these data, the total amount of asbestos
contained in all automotive clutch friction materials sold each year is
calculated to be about 4.5-million pounds.
10-9
-------
Table 10-11 - Some U. S. Driving Characteristics
City
Chicago
Houston
Los Angeles
Minneapolis-St. Paul
New York
Detroit Traffic test
(this study)
Average
Daily
Mileage
35
36
32
-
38
110
Average
Speed
22.9
25.2
24.7
26.3
25.4
17
Daily
Driving
Time
88 minutes
85 minutes
70 minutes
-
85 minutes
7.0 hours
Source: American Petroleum Institute (except for Isst item)
Table 10-12 - Brake Applications Per Mile
Source
This study
University of
Michigan
Highway Safety
Research Dept.
Zechel et al,
(SAE SP-338)
Type of Traffic
Detroit traffic
Ann Arbor and
Michigan traffic
Cross Country
Eastern trip (4 cars)
Western trip (4 cars)
No. of Pedal
Applications
Per Mile
4.4
1.43
1.43
1.9
0.98
Total
No. of
Miles
8,091
6,255
8,400
24,400
No. of
Stops
Per mile
2.6
-
Average
Decelera-
tion fps
4 to 6
-
Source: as noted
10-10
-------
Table 10-13 - Asbestos Content of Automotive Friction Materials
Vehicle and Brake Type
Average Percent Asbestos
Content by Weight*
Passenger Cars
Drum Linings
Disc Pads
Truck Segments
Clutch Facings
"Average composition" for use in the
calculations in this report.
68 + 5
60 + 5
55 + 5
50 ± 5
60
*Sources Estimates made for this study.
10 1 0.1
PERCENT OF DECELERATIONS EXCEEDING g
0.01 «
Figure 10-1 - Frequency Distribution of Braking Decelerations
10-11
-------
Table 10-14 - Brake Friction Material Weights for Test Vehicle
Vehicle
Test
1
2
3
Friction
Material
Description
Inner Pad
Outer Pad
Primary Lining
Secondary Lining
Inner Pad
Outer Pad
Primary Lining
Secondary Lining
Inner Pad"
Outer Pad
Primary Lining
Secondary Lining
Average Per Wheel
Average Per Axle
Average Per Car
Weight of Friction Material (gms)
Front Disc Pads
Right
95.8
117.4
-
106.4
105.0
-
115.3
152.3
-
Left
93.8
116.5
-
106.1
105.6
-
113.0
160.3
-
231.3
462.6
Rear Drum Linings
Right
-
108.1
189.6
-
104.9
181.3
-
113.2
153.5
Left
-
106.4
189.3
-
102.4
180.2
•
113.7 '
167.7
311.3
622.6
1085.2
Table 10-15 - Number of Newly Surfaced Rotors Used Each Year
Rotors replaced
Rotors turned or ground
New rotors on new
vehicles (1972)
Total rotors with
new surfaces per year
Percent of vehicles with new surfaces:
68,570.000
VW J _/ / \J j \J\J\J f\f\
4 x 123,323,000 x ° =
4,700,000
9,810,000
54,060,000
68,570,000*
*Source; Stanford Research Institute Data.
10-12
-------
Table 10-16 - Compilation of Annual Motor Vehicle Brake Friction
Material Usage
Vehicle
Passenger
Car
Light
Truck
Medium
Truck or Bus
Heavy
Truck
Miscellaneous
(Trailers, etc.)
Description
Front Disc
Pads Only
Front Drum
Linings Only
Rear Drum
Linings Only
Drum Linings
Drum Linings
Drum Linings
Drum Linings
Amount Used
Number and Unit
9,660,000 Axle Sets
24,300,000 Axle Sets
32,400,000 Axle Sets
4,730,000 Vehicle Sets
670,000 Vehicle Sets
781,000 Vehicle Sets
Weight
Per
Unit (Ibs)
1.0
1.8
1.3
5.0
15.0
41.0
Total Weight
(Ibs)
9,660,000
43,700,000
42,100,000
23,700,000
10,100,000
32,100,000
10,000,000
171,360,000
Source: Calculated from Friction Materials Standards Institute,
D.O.T., and Stanford Research Institute Data.
-------
Table 10-17 - Compilation of Annual Clutch Friction Material Usage
Vehicle
Passenger Cars:
Domestic
Imports
Totals
Trucks :
Light
Medium
Heavy
Totals
New
900,000
1,350,000
2,250,000
1,500,000*
290,000*
190,000*
1,980,000
Annual Clutch Facing Use
Replacement
New
1,760,000
935,000
Rebuilt
280,000
1,170,000
Total
Units
Installed
1,710,000
2,580,000
4,290,000
3,100,000*
600,000*
385,000*
4,085,000
Weight
Per Unit
(Ibs)
0.88
0.60
1.26
1.56
2.26
Total
Clutch Weight
(Ibs)
1,500,000
1,550,000
4,000,000
950,000
680,000
8,740,000
*Estimated for ratio each truck size with clutch (Table 10-3)
Source: Estimated from market studies and industry sources for this study
Table 10-18 - Relative Brake Relining Frequency
Locale
Northeast
South
Large cities (over 1 million)
Medium cities (100,000-500,000)
Small cities (under 25,000)
Rural areas
Average -U.S.
No. of Wheels Relined
Per 100 Vehicles Each
Year
74
49
82
93
54
44
60*
*Approximately equivalent to relining all four wheels
on 15% of all vehicles each year.
10-14
-------
Frequency of brake relining is another measure of lining
use, Table 10-18(10-13). Multiplying the relining rate of 15 percent
per year times the vehicle population of 123 million and adding, the number
of new vehicles registered last year, 13.5 million, gives 32,100,000 ve-
hicle sets as an estimate of annual friction materials usage. This is
a somewhat smaller number than that derived in Table 10-16, probably be-
cause insufficient emphasis was given to medium and heavy trucks in these
data. One word of caution is in order at this point: the amount of fric-
tion material worn away each year is significantly less than that which
is installed for a variety of reasons to be discussed in the next
sub-section.
10.2.5 Amount of Friction Material Actually Worn
For several reasons, the amount of brake lining (and
asbestos) worn away during a year is significantly less than the total
amount installed on vehicles. Brake linings are seldom completely worn
away (due to the geometry of brake systems, perhaps 10 percent of the
lining is still left on a brake when lining wear-through occurs). Linings
are usually replaced in sets rather than piecemeal. As a consequence of
this and other actions, about 25 percent of all brake linings is discarded
at relining time. Furthermore, millions of vehicles are retired from
service each year, many with brake linings that are far from worn out.
Perhaps the average retired vehicle has about 1/3 of its usable lining
remaining, or 1/3 x 90 percent + 10 percent = 40 percent of the installed
weight of the lining.
Combining these figures, the amount of brake friction
material worn away each year is calculated as follows:
Total Brake
Friction Material
Installed weight each year 171.4 million Ibs
Less Discarded on relining - 25% 42.7 million Ibs
Less discarded on vehicles retired 11.7 million Ibs
(7 million cars x 2.38 Ib x 40% = 6.7 +
(0.75 million light trucks x 5 Ibs x 40% = 1.5)+
(0.10 million medium trucks x 15 Ibs x 40% = 0.6)+
(0.15 million heavy trucks'x 41 Ibs x 40% = 2.4)+
(miscellaneous =0.5)
Amount worn away, annually 117.0 million Ibs
10-15
-------
Employing the same reasoning for clutches, the amount of
clutch material worn away is calculated as follows:
Total Clutch
Friction Material
Installed weight each year 8.76 million Ibs
Less discarded on relining - 15% 1.31 million Ibs
Less discarded on vehicles retired 0.89 million Ibs
(1.5 million cars x 0.75 Ibs x 40% = 0.45)+
(0.50 million light trucks x 1.26 Ibs x 40% = 0.45)+
(0.10 million medium trucks x 1.56 Ibs x 40% = 0.06)+
(0.15 million heavy trucks x 2.26 Ibs x 40% = 0.13)
Amount worn away, annually 6.56 million Ibs
Summarizing, the combined total of brake and clutch fric-
tion material worn away annually is 117.0 + 6.6 = 123.6 million pounds.
Assuming that the average asbestos content is 60 weight percent, the
amount of asbestos worn away as friction material wear debris is ^74
million pounds.
10.3 INTERPRETATION OF TEST RESULTS
10.3.1 Factors Influencing Rate of Emissions
Emissions measured during this program were generated by
an intentionally severe schedule, one that is used by the industry to
accelerate brake testing. Consequently, emissions were undoubtedly gen-
erated at a rate somewhat above average for the population as a whole.
Emissions per mile for a given brake can vary, for ex-
ample, with the following:
• Composition of the friction material
• Composition, metallurgical structure and hardness of the
cast iron rotor (drum or disc).
• Surface roughness of the rotor.
• Previous use (history) of the friction material - primarily
thermal history, both recent and overall.
• Third-body contamination of the sliding interface by
road dust, wear debris, rain water, salt and the like.
• Vehicle usage - miles driven: urban, surburban, rural,
expressway.
• Vehicle weight, including passengers and cargo.
• Vehicle speed at beginning (and end) of stop.
10-16
-------
• Deceleration (average or typical, as well as instantaneous).
• Frequency of braking due to traffic, terrain, and
driver habits.
• Interface temperature, sliding speed, and unit load on
the friction material.
• Roadway surface and grade.
• Air temperature, wind velocity, and wind direction
relative to direction of vehicle motion.
• Brake design, including brake balance front to rear,
and swept area in relation to vehicle weight and
horsepower.
• Vehicle design including brake cooling adequacy.
• Operator habits and behavior - riding the brake,
gentle stops versus rapid deceleration versus abusive
deceleration, etc.
• Brake adjustment and maintenance - balance from side
to side and front to rear.
Some of the above factors are not independently variable, but are mentioned
for emphasis. Tires (radial versus bias belt), engine-transmission brak-
ing, suspension, and aerodynamic shape also influence vehicle braking to
some extent.
During this test program, emissions were measured under
the following sets of conditions:
• Seven different friction material formulations made
by five different manufacturers.
• Disc versus drum brakes.
• New friction materials versus used friction materials.
• Freshly machined rotors versus polished (used) rotors.
• Moderate use versus abusive use under seven driving
categories.
Emissions were examined for asbestos content using the
best available techniques and confirmatory tests were conducted at two
additional laboratories (Battelle and Johns-Manville). The program
results for asbestos emissions were slightly higher and were chosen ex-
clusively to calculate a maximum asbestos emissions estimate.
10-17
-------
10.3.2 Weighting Factors
10.3.2.1 Distribution Weighting Factors
10.3.2.1.1 Location of Wear Debris
Disc brakes are designed to allow air to pass through
them freely. Because of this open design they retain less wear debris
than drum brakes. Consequently, the surfaces samples for the disc brake
are essentially emitted samples. As indicated earlier, the disc brake
emission collector collected all disc brake wear debris. It was frac-
tionated into the following samples:
• airborne: these are the light particles which remain in
the air-stream as it progress through -the
collector - in this program this material was
collected on filters - and the particulates
were presumed to be representative of disc brake
wear debris which may remain airborne in the
atmosphere for a period of time.
• surfaces: these are the heavier agglomerates which quickly
fall to the ground or nearby surfaces - in this
program this material was deposited on the bottom
and inner surfaces of the shroud and on the brake
parts.
• sump: these are the particles of brake debris remaining
in the brake on the lining surfaces, in the rivet
holes, and in the caliper.
The drum brake emissions collector also collected
all of the drum brake wear debris. It fractionated into the following
samples:
• airborne: there are light particles which remain in the
air-stream as it passes through the collector -
in this program this material was collected on
filters - and the particulates were presumed
to be representative of disc brake wear debris
which may remain air-borne in the atmosphere for
a period of time.
• surfaces: these are the heavier agglomerates which quickly
fall to the ground or nearby surfaces - in this
program this material was deposited on the inner
surfaces of the shroud and on the brake parts.
• sump: these are the particles which remain on the brake
drum and lining surfaces and in the rivet holes.
10-18
-------
10.3.2.1.2 Comparison of Normal versus Shrouded Brakes
The effect which the shrouding produced on the
quantity and distribution of the emissions for the right front disc brake
and the right rear drum brake can be estimated as follows.
The data given earlier in Tables 9-9 and 9-10 for
vehicle tests 1 and 2 show that the individual sump samples of wear
debris collected after each schedule for the normal disc brake are com-
parable in amount to those of the shrouded disc brake. The totals are
also comparable. On the other hand, the data given in Table 9-11 show
that the cumulative sump sample, taken at the end of vehicle test 3, is
significantly less than the total obtained from the summation of each
individual schedule. Further, the total sump sample for vehicle test 3
is comparable in value to the average value collected for each schedule
alone of vehicle tests 2 and 3. Consequently, the sump sample appears
to achieve and maintain an average value independent of the mileage.
When the debris is removed, the equilibrium value appears to reestablish
itself.
The surfaces samples for the open brake behaves in a
similar manner. The surfaces samples of the open brake were smaller
(only 2.7 to 4.5 percent of the shrouded brake samples). The total
surfaces sample for the left front brake, taken after vehicle test 3, was
comparable to the maximum single value (for the Detroit traffic test -
the longest mileage test), when individual values are taken after each
schedule. Here again, an equilibrium value appears to establish itself.
The best estimate for the distribution of the disc
brake wear debris when the brake is new can be made by considering the
Burnish data of Table 9-13. After 174 miles, the distribution of emis-
sions can be estimated.
9% returned in sump
2% on surfaces - calculated from open brake
4% airborne - measured at shrouded brake
85% road dropout - balance
The best estimate for the distribution of the disc
brake wear debris for a use brake can be made from the data from vehicle
test 3. After 2632 miles, the distribution from the open disc brake is
as follows:
1.5% retained in sump
1.4% retained on surfaces - evaluated from open brake
7% airborne - average from shrouded brake
91% road-dropout - balance
As the brake is used, the amount retained in the brake remains constant,
but the percent values for retention decrease to less than one percent.
10-19
-------
The average for the airborne samples for 8100 miles is six percent. Thus
the distribution for the well-used disc brake can be estimated as follows:
1% retained in brake
6% airborne
93% road drop-out
No major change in these relative proportions is expected for continued
operation beyond the 8100 miles of the test to wear-out.
The data given in Table 9-9 for vehicle test 1 show
that the amounts of sump sample debris collected after each schedule for
the normal (unshrouded) drum brake are somewhat comparable to those of
the shrouded drum brake. The totals are also somewhat comparable, al-
though the total for the shrouded brake seems slightly low. The surfaces
samples are slightly less for the normal drum brake and the overall totals
for the entire test show that approximately 53 percent of the surfaces
samples remained in the brake. The negative numbers for the sump samples
are real. Since 80 percent of the sump sample from the previous schedule
was reintroduced onto the brake drum prior to each following schedule,
it was possible for the sample to redistribute in such a way that the
sump sample decreased to a value less than the original amount added.
The surfaces sample showed a corresponding increase so that the total
debris generated was never a negative value for the shrouded brake. The
normal drum brake could and did occasionally show a negative value for
total debris.
The rear brake data given in Table 9-10 for vehicle
test 2 was for the continued testing of the used original equipment rear
brake linings from vehicle test 1. Thus each rear wheel started with
the 80 percent sump debris addition (from vehicle test 1). The total
debris collected from the shrouded brake for vehicle tests 1 and 2 were
comparable. The total debris from the open brake was less for vehicle
test 2 than for vehicle test 1. The only explanation feasible is as
follows. The amount in the sump debris of this test is at an equilibrium
level and there is no more physical room for the material. Thus it falls
out of the wheel immediately and less debris is distributed to the sur-
faces in vehicle test 2 as compared to vehicle test 1.
The best estimate for the normal distribution of
drum brake wear debris when the brake is new can be made from the Burnish
data of Table 9-13. After 174 miles, the distribution of emissions can
be estimated as follows:
16% retained in sump
29% retained on surfaces - calculated from open brake
1% airborne - measured at shrouded brake
54 road drop-out - balance
10-20
-------
The best estimate for the distribution of drum brake
wear debris for a used brake can be made by extending the data in
Table 9-11 for vehicle test 3. For 2632 miles, the open drum brake
accumulated the following:
Sump debris: 0.97 gm (9% of weight loss)
Surface debris: 1.91 gm (17% of weight loss)
Supplementary data from employees' vehicles and vehicles submitted for
brake relines in local shops indicated the following trends for friction
materials with an average life of 40,000 miles:
After 5000 miles:
Sump debris: ^2 gm (vLO% of friction material wear)
Surfaces debris: ^4 gm (^18% of friction material wear)
After 25,000 miles:
Sump debris: V3 gms (^5% of friction material wear)
Surfaces debris: M.O gms (vL2% of friction material wear)
After 40,000 miles:
Sump debris: ^4 gms (^3% of friction material wear)
Surfaces debris: ^12 gms (M.0% of friction material wear)
The trends are graphically illustrated in Figure 10-2.
Not all of the wear debris found in a brake is from
the friction material itself. The analysis of a few samples for iron
content indicated approximately 5-15 percent by weight is iron oxide
which came from the rotor wear.
In this program, no driving or braking took place
on dusty or salted roads. However, the average consumer would drive
under these conditions at times and this would slightly alter the com-
position of the retained brake debris. For purposes of estimation, the
average vehicle has linings that are 50 percent worn (at the 20,000 mile
point on Figure 10-2) and the contributions to the atmosphere can be
estimated in the following manner:
13% retained in sump
6% retained on surfaces
2% airborne
79% road drop-out
10-21
-------
20
16-
3?
Q
< 12
CC
CO
cc
co
III
0
DC
8-
4-
20
16 -
O)
CO
cc
to
Uj
Q
DC
12 -
a j
o -
4-
PERCENT SURFACES
DEBRIS RETAINED
WEIGHT OF
SURFACES DEBRIS
PERCENT SUMP
DEBRIS RETAINED
WEIGHT OF
SUMP DEBRIS
10,000
20,000
MILES
30,000
40,000
n
01
01
Figure 10-2 - Variation of Wear Debris Retention with Mileage
(for Rear Drum Brakes)
10.3.2.1.3 Summary
As a result of the above analysis, it is proposed
that the test results be weighted in the following manner for the deter-
mination of asbestos emissions distribution from a passenger vehicle:
Simulation
Disc Brake:
New friction couple
After 2632 miles
After 8100 miles
After 20,000 miles
Drum Brake:
New friction couple
After 2632 miles
After 20,.000 miles
Test Schedule
Required
Burnish
Composite
Composite
Composite
Burnish
Composite
Composite
Airborne Road Vehicle
(Atmosphere) Drop-Out Retention
0.04
0.07
0.06
0.06
0.01
0.02
0.02
0.85
0.91
0.93
0.93
0.54
0.72
0.79
0.11
0.03
0.01
0.01
0.35
0.26
0.19
10-22
-------
10.3.2.2 Severity Weighting Factors
10.3.2.2.1 New Versus Burnished Friction Materials
The vehicle test results indicated that rerunning
the rear drum linings from vehicle test 1 on vehicle test 2 gave lower
asbestos emissions. The A. B. Baseline and Detroit Traffic schedules of
vehicle test 2 showed lower asbestos than the corresponding schedules of
vehicle test 1. The same trends were shown for the clutch. Consequently,
it is necessary to include a certain percentage (weight) of Burnish
schedule results in the calculations of total asbestos emissions.
Burnish tends to be completed after approximately
200 miles of test driving schedules, but stability of surface finish may
not occur until somewhat later on private passenger cars. Assuming that
the maximum is 400 miles and that; the brake friction materials have a
30,000-mile average life, the fraction of driving is:
400 -0.013
30,000
This is the severity factor used for determining the extent of Burnish
asbestos emissions. During the next period of driving, the friction
materials are still moving toward their stabilized level for light to
moderate duty. The test vehicle used approximately 350 miles. Assuming
that up to 400 miles are required, the fraction of driving is kept the
same as for the Burnish factor above. Thus the A. B. Baseline factor is
also 0.013.
10.3.2.2.2 Severe or Abusive Braking
The results presented previously show conclusively
that total emissions increase during and immediately after severe (abu-
sive) braking (the fade tests). While it is necessary to test brakes
under these abusive conditions so that they will function in emergencies,
it is not common to operate vehicles in the abusive manner that generates
high emissions. Data reported in Section 10.2 indicate that severe braking
occurs less than 10 percent of the time, nationwide.
Most of the severe braking takes place in comparatively
remote or lightly populated mountain areas where 11.5 percent of all
driving takes place (Table 10-10). With experience, most of the local
drivers tend to drive in a manner where they refrain from fading the
brakes. Assuming that the severe braking encountered under these condi-
tions occurs a maximum of 10 percent, the fraction for severe braking
can thus be calculated:
0.10 x 11.5 = 1.15 percent of all driving
The amount of hot-rodding followed by severe braking,
is not known. Nor is the amount of driving known when a foot is kept on
10-23
-------
the brake at all times. A further action which causes emissions caused
by severe brake friction material dragging is on the unreleased emergency
brake. To account for all of these actions, the above fraction of driving
should be increased to a 2.0 percent maximum. Thus the factor for the
10-Stop Fade consideration is 0.020.
10.3.2.2.3 Renewal of Friction Surfaces
The data given in Section 9.6 show that the wear rate
of friction materials is increased after high-temperature operation.
Consequently, the calculations of asbestos emissions requires the inclu-
sion of an A. F. Baseline contribution. The test vehicle used approxi-
mately 350 miles; under less than moderate duty, approximately 600 miles
would be required. The fraction of driving which gives the A. F. Baseline
factor can be calulated:
600 =0.020
30,000
10.3.2.2.4 Normal Brake Operation
Most braking takes place under normal or low tempera-
tures (less than 300°F). As indicated earlier, the Detroit Traffic Test
is an accelerated vehicle test and is more severe than normal driving
throughout most of the country. The temperatures actually encountered
would be typical of warmer climates and hilly areas such as those found
in the Los Angeles area. In any event, the Detroit Traffic Test used in
this program gives the maximum asbestos emissions expected for normal
brake operation.
10.3.2.3 Summary
As a result of the above analysis, it is proposed that
the test results be weighted in the following manner for the determination
of maximum total asbestos emissions for a passenger vehicle:
Test Schedule Weighting
Simulation Required Factor
New friction couple Burnish 0.013
Surfaces preparation A. B. Baseline 0.013
Moderate braking Detroit Traffic 0.934*
Severe braking 10-Stop Fade 0.020
Renewal of friction
surfaces A. F. Baseline 0.020
*Determined by difference
10.3.3 Asbestos Emissions Per Vehicle
10.3.3.1 Total Asbestos Emissions Estimate
The total asbestos emissions for the test vehicle can
10-24
-------
be estimated from the test results given in Section 9 and the severity
weighting factors. The calculation is summarized in Table 10-19. The
asbestos emissions for the disc brakes, drum brakes, and clutch from
each vehicle test were averaged and used with the Burnish, A. B. Baseline,
Detroit Traffic, 10-Stop Fade, and A. F. Baseline schedules. The cor-
responding severity factors were used to calculate the weighted emissions.
The sum of the weighted emissions is the total asbestos emissions expected
from an average vehicle.
10.3.3.2 Asbestos Emissions and Their Fate
The total asbestos emissions per vehicle as calculated
above, are not merely deposited onto the ground or entirely emitted into
the atmosphere. In general, the asbestos emissions can and will probably
end up in any of three different places:
• retained in the brake and/or disposed of during servicing.
• deposited on the ground
• floated into the atmosphere
The calculation given in Table 10-20 shows that the largest part of the
asbestos emissions produced is emitted from the brakes and clutch as
drop-out material. The fate of the total emissions calculated earlier for
the test vehicle is as follows:
Road-dropout: 23.34/28.51 x 100 = 81.9 percent
Airborne: 1.05/28.51 x 100 = 3.7 percent
Retained in Brake: 28.51 - 24.39/28.51 x 100 =14.4 percent
10.4 ESTIMATED ASBESTOS EMISSIONS
10.4.1 Passenger Vehicles
10.4.1.1 Total Asbestos Emissions
The estimated total asbestos emissions per year can be
calculated from the following information:
Total asbestos emissions per vehicle: 28.51 micrograms/mile
Number of miles per year: 9,978
Number of passenger vehicles: 96,400,000
Estimated asbestos emissions in pounds per year
= -.?8'51.?P x ID'6 ffl x 9.978 x 103 Sii^ x ^- x 96.4 x 106 vehicles
mile-vehicle yg yr 454 gm
= 60,400 pounds per year.
10.4.1.2 Distribution of Asbestos Emissions
The distribution of the total asbestos emissions cal-
culated for the test vehicle can be determined by applying the percent
distributions given in Section 10.3.3.2. The fate of the 60,400 pounds
10-25
-------
M
Table 10-19 - Total Asbestos Emissions Calculated From the Test
Vehicle (Average for the Three Vehicle Tests)
Schedule
Burnish
A. B. Baseline
Detroit Traffic
10-Stop Fade
A. F. Baseline
Friction
Couple
Disc Brake
Drum Brake
Clutch
Disc Brake
Drum Brake
Clutch
Disc Brake
Drum Brake
Clutch
Disc Brake
Drum Brake
Clutch
Disc Brake
Drum Brake
Clutch
Asbestos Emissions (ug/mile)
Vehicle Test
1
16.70
59.09
—
2.23
9.22
—
2.35
11.07
—
100.60
22.58
—
29 . 61
5.21
—
2
36.35
24.43
—
4.71
2.38
—
12.75
5.50
—
79.13
146.14
—
6.69
3.28
—
3
7.21
11.67
—
1.96
1.98
—
0.48
0.63
—
8.82
5.03
—
3.51
0.32
—
Average
20.09
31.39
1.11
2.97
4.52
1.11
5.19
5.73
1.11
62.80
58.15
1.11
13.27
2.94
1.11
Per
Axle
40.18
62.78
—
5.94
9.04
—
10.38
11.46
—
125.60
116.30
—
26.54
5.88
—
Severity
Weighting
Factors
0.013
0.013
0.934
0.020
0.020
Total
Weighted
Emissions
(yg/mile)
0.52
0.82
0.01
0.07
0.12
0.01
9.70
10.70
1.03
2.51
2.33
0.02
0.53
0.12
0.02
28.51
-------
Table 10-20 - Distribution-Weighted Asbestos Emissions From the
Test Vehicle
Schedule
Burnish
A.B.
Baseline
Detroit
Traffic
10-Stop
Fade
A.F.
Baseline
Friction
Couple
Disc Brake
Drum Brake
Clutch
Disc Brake
Drum Brake
Clutch
Disc Brake
Drum Brake
Clutch
Disc Brake
Drum Brake
Clutch
Disc Brake
Drum Brake
Clutch
Asbestos Emissions (pg/mile)
Vehicle Test
1
16.70
59.09
2.23
9.22
2.35
11.07
100.60
22.58
29.61
5.21
2
36.35
24.43
4.71
2.38
12.75
5.50
79.13
146.14
6.69
3.28
3
7.21
11.67
1.96
1.98
0.48
0.63"
8.82
5.03
3.51
0.32
Average
20.09
31.39
1.11
2.97
4.52
1.11
5.19
5.73
1.11
62.80
58.15
1.11
13.27
2.94
1.11
Per
Axle
40.18
62.78
5.94
9.04
10.38
11.46
125.60
116.30
26.54
5.88
Dist. Weighting
Factors
Dr op-Out
0.85
0.54
0.10
0.85
0.54
0.10
0.93
0.79
0.10
0.93
0.79
0.10
0.93
0.79
0.10
Airborne
0.04
0.01
0.01
0.04
0.01
0.01
0.06
0.02
0.01
0.06
0.02
0.01
0.06
0.02
0.01
Severity
Weighting
Factors
0.013
0.013
0.934
0.020
0.020
Total
Weighted Emissions
(pg/mile)
Drop-Out
0.44
0.44
0.00
0.06
0.07
0.00
9.02
8.45
0.10
2.33
1.84
0.00
0.49
0.10
0.00
23.34
Airborne
0.02
0.01
0.00
0.00
0.00
0.00
0.58
0.21
0.01
0.15
0.04
0.00
0.03
0.00
0.00
1.05
o
NJ
-------
calculated for the test vehicle is as follows:
Road-dropout: 49,470 pounds
Airborne: 2,230 pounds
Brake retention: 8,700 pounds
10.4.2 Trucks and Buses
10.4.2.1 Estimated Severity Factors
Truck brakes usually tend to operate at higher tempera-
tures than passenger cars. Thus a greater proportion of high-temperature
use in severity weighting can be obtained by using a larger fraction of
the 10-Stop Fade asbestos emissions. For trucks and buses, the test re-
sults are arbitrarily weighted as follows:
Simulation Test Schedule Weighting Factor
Light Truck:
New materials Burnish 0.013
Moderate braking A. B. Baseline 0.013
Moderate braking Detroit Traffic 0.874
Abusive braking 10-Stop Fade 0.050
Surface renewal A. F. Baseline 0.050
Medium Truck and Bus:
New materials Burnish 0.013
Moderate braking A. B. Baseline 0.013
Moderate braking Detroit Traffic 0.774
Abusive braking 10-Stop Fade 0.100
Surface renewal A. F. Baseline 0.100
Heavy Truck:
New materials Burnish 0.013
Moderate braking A. B. Baseline 0.013
Moderate braking Detroit Traffic 0.674
Abusive braking 10-Stop Fade 0.150
Surface renewal A. F. Baseline 0.150
10.4.2.2 Estimated Emissions Factors
In addition to the severity factors, it is necessary
to estimate the total average asbestos emissions for a light truck, a
medium truck (or bus), and a heavy truck. The value for the test car
was 28.51 micrograms/mile. Assuming that light trucks have a result
proportional to the ratio of the friction materials weights, the asbestos
emissions for light trucks are larger than the test car by the following
factors:
Front drum brake: 2.0
Rear drum brake: 3.0
Clutch: 2.0
10-28
-------
A slightly larger factor is selected for the clutch as it is used more
often in trucks than in passenger cars.
Following the same line of reasoning, the asbestos
emissions for medium trucks and buses are larger than the test car by the
following factors:
Front drum brake: 3.0
Rear drum brake: 10.0
Clutch: 4.0
The factors for a heavy truck are as follows:
Front drum brake: 5.0
Rear drum brake: 30.0
Clutch: 6.0
10.4.2.3 Calculations of Total Asbestos Emissions
for Trucks and Buses
The estimates for the total average asbestos emissions
per vehicle are shown in Tables 10-21, 10-22, and 10-23, for a light truck,
a medium truck or bus, and a heavy truck, respectively.
Table 10-21 - Estimate for Total Asbestos Emissions Expected
for a Light Truck
Schedule
Burnish
A. B. Baseline
Detroit Traffic
10-Stop Fade
A. F. Baseline
Friction
Couple
Front Drum Brake
Rear Drum Brake
Clutch
Front Drum Brake
Rear Drum Brake
Clutch
Front Drum Brake
Rear Drum Brake
Clutch
Front Drum Brake
Rear Drum Brake
Clutch
Front Drum Brake
Rear Drum Brake
Clutch
Asbestos Emissions
Estimate Per Axle (ug/mile)
62.78 x 2.0'
62.78 x 3.0
1.11 x 2.0
9.04 x 2.0
9.04 x 3.0
1.11 x 2.0
11.46 x 2.0
11.46 x 3.0
1.11 x 2.0
116.30 x 2.0
116.30 x 3.0
1.11 x 2.0
5.88 x 2.0
5.88 x 3.0
1.11 x 2.0
Asbestos
Emissions
(ug/mile)
125.56
188.34
2.22
18.08
27.12
2.22
22.92
34.38
2.22
232.60
348.90
2.22
11.76
17.64
2.22
Severity
Weighting
Factors
0.013
0.013
0.874
0.050
0.050
Total
Weighted
Emissions
(pg/mile)
1.63
2.45
0.03
0.24
0.35
0.03
20.03
30.05
1.94
11.63
17.44
0.11
0.59
0.88
0.11
87.51
10-29
-------
Table 10-22 - Estimate of Total Asbestos Emissions Expected
for a Medium Truck
Schedule
Burnish
A. B. Baseline
Detroit Traffic
10-Stop Fade
A. F. Baseline
Friction
Couple
Front Drum Brake
Rear Drum Brake
Clutch
Front Drum Brake
Rear Drum Brake
Clutch
Front Drum Brake
Rear Drum Brake
Clutch
Front Drum Brake
Rear Drum Brake
Clutch
Front Drum Brake
Rear Drum Brake
Clutch
Asbestos Emissions
Estimate Per Axle (ug/mile)
62.78 x 3.0
62.78 x 10.0
1.11 x 4.0
9.04 x 3.0
9.04 x 10.0
1.11 x 4.0
11.46 x 3.0
11.46 x 10.0
1.11 x 4.0
116.30 x 3.0
116.30 x 10.0
1.11 x 4.0
5.88 x 3.0
5.88 x 10.0
1.11 x 4.0
Asbestos
Emissions
(ug/mile)
188.34
627.80
4.44
27.12
90.40
4.44
34.38
114.60
4.44
348.90
1163.00
4.4.4
17.64
. 58.80
4.44
Severity
Weighting
Factors
0.013
0.013
0.774
0.100
0.100
Total
Weighted
Emissions
(Ug/mile)
2.45
8.16
0.06
0.35
1.18
0.06
26.61
88.70
3.44
34.89
116.30
0.44
1.76
5.88
0.44
290.72
Table 10-23 - Estimate of Total Asbestos Emissions Expected
for a Heavy Truck
Schedule
Burnish
A. B. Baseline
Detroit Traffic
10-Stop Fade
A. F. Baseline
Friction
Couple
Front Drum Brake
Rear Drum Brake
Clutch
Front Drum Brake
Rear Drum Brake
, Clutch
Front Drum Brake
Rear Drum Brake
Clutch
Front Drum Brake
Rear Drum Brake
Clutch
Front Drum Brake
Rear Drum Brake
Clutch
Asbestos Emissions
Estimate Per Axle (ug/mile)
62.78 x 5.0
62.78 x 30.0
1.11 x 6.0
9.04 x 5.0
9.04 x 30.0
1.11 x 6.0
11.46 x 5.0
11.46 x 30.0
1.11 x 6.0
116.30 x 5.0
116.30 x 30.0
1.11 x 6.0
5.88 x 5.0
5.88 x 30.0
1.11 x 6.0
Asbestos
Emissions
(ug/mile)
313.90
1883.40
6.66
45.20
271.20
6.66
57.30
343.80
6.66
581.50
3489.00
6.66
29.40
176.40
6.66
Severity
Weighting
Factors
0.013
0.013
0.674
0.150
0.150
Total
Weighted
Emissions
(ug/mile)
4.08
24.48
0.09
0.59
3.52
0.09
38.62
231.72
4.49
87.22
523.35
1.00
4.41
26.46
1.00
951.12
10-30
-------
Table 10-24 - Distribution-Weighted Asbestos Emissions From
A Light Truck
Schedule
Burnish
A.B. Baseline
Detroit
Traffic
10-Stop Fade
A.F. Baseline
Friction
Couple
Front Drum Brake
Rear Drum Brake
Clutch
Front Drum Brake
hear Drum Brake
Clutch
Front Drum Brake
Rear Drum Brake
Clutch
Front Drum Brake
Rear Drum Brake
Clutch
Front Drum Brake
Rear Drum Brake
Clutch
Severity
Weighted
Emissions
(mg/mile)
1.63
2.45
0.03
0.24
0.35
0.03
20.03
30.05
1.94
11.63
17.44
0.11
0.59
0.88
0.11
87.51
Distribution Weighting Factors
Drop-
out
0.89
0.89
0.10
0.90
0.90
0.10
0.90
0.90
0.10
0.90
0.90
0.11
0.90
0.90
0.10
Airborne
0.02
0.02
0.02
0.03
0.03
0.02
0.03
0.03
0.02
0.03
0.03
0.02
0.03
0.03
0.02
Retention
0.09
0.09
0.88
0.07
0.07
0.88
0.07
0.07
0.88
0.07
0.07
0.88
0.07
0.07
0.88
Weighted Emissions (mg/mile)
Drop-
out
1.45
2.18
0.00
0.22
0.32
0.00
18.03
27.05
0.19
10.47
15.70
0.01
0.53
0.79
0.01
76.95
Airborne
0.03
0.05
0.00
0.01
0.01
0.00
0.60
0.90
0.04
0.35
0.52
0.00
0.02
0.03
0.00
2.56
Retention
0.15
0.22
0.03
0.02
0.02
0.03
1.40
2.10
1.71
0.81
1.22
0.10
0.04
0.06
0.10
8.01
Table 10-25 - Summary of All Brake and Clutch Emission (Ibs per year)
Vehicle
Passenger Cars
Light Trucks
Medium Trucks
and Buses
Heavy Trucks
Miscellaneous*
Number
of Vehicles
96,400,000
17,100,000
2,600,000
1,200,000
6,615,000
Totals
Total
Asbestos
Emissions
60,400
32,300
16,300
32,900
16,300*
158,200
Percent of Total
Distribution
Dr op-Out
49,470
28,420
14,330
28,920
14,330
135,470
(85.6)
Airborne
2,230
940
470
950
470
5,060
(3.2)
Brake
Retention
8,700
2,940
1,500
3,030
1,500
17,670
(11.2)
Estimated equal to medium trucks as weights of friction material
used for both categories, are almost equal (Table 12). Includes
motorcycles, trailers, etc.
10-31
-------
The estimated total asbestos emissions per year for
light trucks can be calculated from the following information:
Total asbestos emissions per vehicle: 87.51 yg/mile
Number of miles per year: 9,807
Number of trucks: 17,100,000
Estimated asbestos emissions in pounds per year
= 87.51 x ID'6 x 9.807 x 103 x x 17.1 x 106 vehicles
= 32,300 pounds per year
The estimated total asbestos emissions per year for
medium trucks and buses can be calculated from the following information:
Total asbestos emissions per vehicle: 290.72 yg/mile
Number of miles per year: 9,807
Number of trucks: 2,600,000
Estimated asbestos emissions in pounds per year
= 290.72 -Bf- x 10~6 SSL x 9.807 x 103 ^^. x 1 lb x 2.60 x 106 vehicles
mile yg yr 454 gms
= 16,300 pounds per year
The estimated total asbestos emissions per year for
heavy trucks can be calculated from the following information:
Total asbestos emissions per mile: 951,12 yg/mile
Number of miles per year: 9,807
Number of trucks: 1,600,000
Estimated asbestos emissions in pounds per year
= 951.12 ^f- x 10~6 ££ x 9.8o7 x 103 SilfJL x 1 "> x 1>60 x 106 vehicles
mile yg yr 454 gms
= 32,900 pounds per year
10 . 4 . 2 . 4 Total Truck Asbestos Emissions
The estimated value for the total asbestos emissions
from trucks and buses is as follows:
Light trucks 32,300 pounds
Medium trucks and buses 16,300 pounds
Heavy trucks 32.900 pounds
81,500 pounds
10-32
-------
10.4.2.5 Distribution of Truck Asbestos Emissions
10.4.2.5.1 Estimated Distribution Weighting Factors
The distribution weighting factors for passenger car
brakes are discussed in Section 10.3.2.1. Trucks contain drum brakes
which are designed to be more open than passenger car drum brakes. In
many instances, no splash shields are used or they are very open. More-
over, trucks run with hard tires and stiff suspensions; these lead to a
hard ride and more shaking at the wheels. Consequently, the retention
of wear debris in truck drum brakes is estimated to be approximately 25
percent of that for passenger vehicle drum brakes.
From the data given in Section 10.3.2.1.3, it is
possible to estimate the following distribution weighting factors for
truck drum brakes:
Test Road Vehicle
Simulation Schedule Airborne Drop-Out Retention
New friction couple Burnish 0.02 0.89 0.09
After 2632 miles Composite 0.03 0.90 0.07
The airborne figure was adjusted upward. The openness of the disc brake
gives rise to a higher airborne fraction than for a closed drum brake.
The value estimated for the truck drum brake takes this into account.
10.4.2.5.2 Truck Asbestos Emissions and Their Fate
The total asbestos emissions calculated for the
light truck, medium truck and bus, or heavy truck will be distributed
into three places:
o retained in the brake and/or disposed of during service
o deposited on the ground
o floated into the atmosphere
The typical calculations for the light trucks are given in Table 10-24 and
can be summarized:
Road Drop-out: 76.95/87.51 x 100 = 87.9 percent
Airborne: 2.56/87.51 x 100 = 2.9 percent
Brake Retention: 8.01/87.51 x 100 = 9.2 percent
10.4.3 Estimated Asbestos Emissions
The summary of the total asbestos emissions estimates and
their distribution is given in Table 10-25.
10-33
-------
Table 10-26 - Calculation of Weighted Average Unconverted Asbestos
Percent for Sump Sample
Schedule
Burnish
A.B.
Baseline
Detroit
Traffic
10-Stop
Fade
A.F.
Baseline
Vehicle
Test
1
2
3
Average
1
2
3
Average
1
2
3
Average
1
2
3
Average
1
2
3
Average
Front
Brake
0.813
0.402
0.218
0.478
1.650
0.236
0.106
0.664
0.247
0.304
0.018
0.190
0.463
0.244
0.045
0.251
0.656
0.443
0.158
0.419
Rear
Brake
0.484
0.063
0.274
0.179
0.268
0.063
0.170
0.129
0.240
0.046
0.138
0.280
0.199
0.102
0.194
0.419
0.138
0.034
0.197
Overall
Average
0.376
0.417
0.164
0.223
0.308
Weighting
Factor
0.013
0.013
0.824
0.075
0.075
Weighted
Percent
0.005
0.005
0.135
0.017
0.023
0.185
Table 10-27 - Calculation of Weighted Average Asbestos Percent for
Surfaces Sample
Schedule
Burnish
A.B.
Baseline
Detroit
Traffic
10-Stop
Fade
A.F.
Baseline
Vehicle
Test
1
2
3
Average
1
2
3
Average
1
2
3
Average
1
2
3
Average
1
2
3
Average
Front
Brake
0.398
0.968
0.101
0.489
0.472
0.311
0.024
0.269
0.137
0.548
0.013
0.233
0.162
0.261
0.041
0.155
0.507
0.173
0.073
0.251
Rear
Brake
0.865
1.416
0.046
0.776
0.415
0.098
0.056
0.190
0.373
0.113
0.057
0.181
0.071
0.619
0.055
0.248
0.242
0.237
0.022
0.167
Overall
Average
0.633
0.230
0.207
0.202
0.209
Weighting
Factor
0.013
0.013
0.824
0.075
0.075
Weighted
Percent
0.008
0.003
0.171
0.015
0.016
0.213
10-34
-------
10.4.4 Alternate Estimate for Total Asbestos Emissions
An alternate method to calculate an estimate for total
asbestos emissions is proposed.
Tables 10-26, 10-27, and 10-28 list the data and the
calculations required to produce a weighted average asbestos percent for
the sump, surfaces, and airborne samples using the weighted portions of
the Baseline, A. B. Baseline, Detroit Traffic, 10-Stop Fade, and A. F.
Baseline schedules.
The data given in Table 10-16 indicated that the percent-
ages of annual consumption of friction materials is as follows:
Passenger Car Brakes: 56 percent
Truck Brakes: 44 percent
The data given in Section 10.3.2.1.3 and Section 10.4.2.5.1 show that the
average distributions for most of the brake mileages can be summarized as
follows:
Road Vehicle
Brake Airborne Drop-Out Retention
Passenger Car Brakes 0.03 0.77 0.20
Truck Brakes 0.03 0.90 0.07
The calculation for the weighted average asbestos found in all brakes is
given in Table 10-29.
The average wear debris recovery for each vehicle can
also be calculated from the data given in Table 9-14:
Fronts . Rears
Test 1 51.2* 67.8*
2 60.8 81.6
3 60.2 81.3
*Low because of incomplete, difficult recoveries
of Fade samples.
The drum rear samples are known to contain approximately 10 weight percent
material such as iron oxide from drum wear. Thus an average recovery of
approximately 65 percent, based on the debris from the friction materials
for vehicle tests 2 and 3, is used in the calculation. Therefore, the
asbestos percent based on the friction material worn in the test vehicle
is calculated as follows:
0.206 x 0.65 = 0.134
10-35
-------
Table 10-28 - Calculation of weighted.average.asbestos Percent for
Airborne Samples
Schedule
Burnish
A.B.
Baseline
Detroit
Traffic
10-Stop
Fade
A.F.
Baseline
Vehicle
Test
1
2
3
Average
1
2
3
Average
1
2
3
Average
1
2
3
Average
1
2
3
Average
Front
Brake
0.144
0.186
0.099
0.143
0.290
0.211
0.125
0.209
0.052
0.234
0.025
0.104
0.154
0.107
0.055
0.105
0.134
0.165
0.047
0.115
Rear
Brake
0.349
0.087
0.060
0.165
0.493
0.344
0.044
0.294
0.092
0.115
0.037
0.081
0.132
0.194
0.014
0.113
0.079
0.180
0.003
0.087
Overall
Average
0.154
0.251
0.093
0.109
0.101
Weighting
Factor
0.013
0.013
0.824
0.075
0.075
Weighted
Percent
0.002
0.003
0.077
0.008
0.008
0.098
Table 10-29 - Data and Calculation of.Weighted.Asbestos Percent
for All Vehicles
Friction
Materials
Passenger
Car
Truck
Fraction
of Friction
Material
0.56
0.44
Fraction
of Debris
Airborne
Drop-Out
Retention
Airborne
Drop-Out
Retention
0.03
0.77
0.20
0.03
0.40
0.07
Weight
Percent
Asbestos
0.098
0.213
0.185
0.098
0.213
0.185
Weighted
Asbestos
Percent
0.002
0.092
0.021
0.001
0.084
0.006
0.206
10-36
-------
The total weight of friction material worn away annually in brakes is
117 million pounds. The total asbestos estimate from brakes can now be
calculated:
117,000,000 x 0.00134 = 157,000 pounds
The total weight of friction material worn away annually in clutches is
6.6 million pounds. The total asbestos estimate from clutches (assuming
a retention of ^75 percent) can be calculated as follows:
6,600,000 x 0.00047 x 0.25 = 800 pounds
Thus the total is approximately 157,800 pounds, which agrees with the
figure reported in Section 10.4.3 above.
10.5 SUMMARY OF ASBESTOS EMISSIONS
The results indicate that more than 99.7 percent of the asbestos
used in friction material is converted to a non-fibril form. The total
asbestos emissions for all vehicles in the United States is estimated
to be 158,000 pounds annually. Of this total, a small part was found
to remain airborne. The contribution to the atmosphere is estimated
to be 5060 pounds, or 3.2 percent of the total asbestos emissions.
10-37
-------
10,6 REFERENCES
(10-1) National Highway Traffic Safety Administration and Federal
Highway Administration preliminary estimates, private com-
munication, January 18, 1973.
(10-2) R. L. Polk & Co., private communication, January 12, 1973.
(10-3) "Truck Sales Jumped 24 Percent in 1972 to 2.6 Million
Units," Wall Street Journal, January 8, 1973.
(10-4) "1972 Automobile Facts and Figures," Motor Vehicle
Manufacturers Association, 1973.
(10-5) "Motor Truck Facts," Motor Vehicle Manufacturers
Associaation, 1973.
(10-6) W. J. Zechel, et. al., "Automotive Brake Evaluation Under
Customer Usage Conditions," SAE Special Publication SP-338,
Society of Automotive Engineers, April 1968.
(10-7) R. G. Mortimer (University of Michigan), "Hard Braking
is More Common Than You Might Think," Automotive
Engineering, August 1971, page 32.
(10-8) N. Carpenter and E. G. Goddard, "The Measurement of
Braking Performance for Compulsory Motor Vehicle Inspec-
tion," Journal, Institute of Motor Industry, Vol. 4,
No. 10, 1955.
(10-9) Private Communication, January 1973.
(10-10) Private Communication, January 1973.
(10-11) C. F. Harwood (IITRI), "Asbestos Air Pollution Resulting
From the Wear of Braking Linings," Illinois Institute of
Technology Research Institute, April 1972.
(10-12) T.(C. May and R. W. Lewis, "Asbestos," A Chapter from
"Mineral Facts and Problems," U.S. Bureau of Mines
Bulletin 650, 1970 edition.
(10-13) Private Communication, January 1973.
10-38
-------
SECTION 11
SUMMARY
The specific objectives of this program were stated earlier. The
end objective was the documentation of asbestos emissions from brakes
and clutches and the assessment of their overall contributions to the
atmosphere. These objectives were met by means of the program as planned
and completed.
For the results to be representative of average consumer-type vehicle
usage, a vehicle intermediate between compacts and luxury vehicles was
selected. The vehicle was equipped with front disc brakes, rear drum
brakes, and a dry clutch. All friction material used contained asbestos.
Three vehicle tests were run. The first vehicle test was run with the
original-equipment friction materials. The second vehicle test simulated
a partial reline - fronts only relined - while the rears were repeated to
give a replicate test, and an indication of emissions trends for friction
materials with continued use. The third vehicle test simulated a complete
brake reline, and included turned discs and drums. The friction materials
selected for the program were representative of those supplied by the
industry - five different manufacturers produced the original equipment
and aftermarket disc pads and drum linings, which were selected in part
because of their high-volume usage.
The collection of particulate and gaseous emissions from any vehicle
friction couple has never, to the authors' knowledge, been reported in the
literature. To define the extent of these emissions, a collection system
was devised which combined the functions of separation and storage. Unique
emissions collectors for both disc and drum brakes, and for a clutch, were
conceived, designed, and built as the main embodiment of this instrumenta-
tion. The collectors separated the wear debris into three different frac-
tions: a sump sample which included the wear debris on the lining surfaces,
in the rivet holes, and on the brake drum; a surfaces sample which in-
cluded the wear debris on the brake and collector shroud surfaces; and
an airborne sample collected on membrane filters.
The front disc brake emission collector was tested on an inertia
dynamometer to check out its operation. The most critical part of the
collector operation was the rotating seal. The final design selected
was made from graphite-filled Teflon which rotated against a hardened
steel ring. Thermal response tests were made, the results indicating
that for normal operation the shrouded disc brake would operate at a
slightly higher temperature than the normal brake configuration. A
method was devised to determine the leak rate of the collector. The
rotating seal was largely responsible for the residual leak; the leak
rate was reduced significantly by use of a very small amount of high-
temperature grease. The rotating seal underwent durability testing and
11-1
-------
survived seven hours at 50 mph. A second series of dynamometer tests
gave reproducible emissions and temperatures. Finally, a test was made
in which the collector, and especially the rotating seal, were shown to
be relatively leak-tight to external liquid and particulate contaminants.
The vehicle was equipped with standard brake test instrumentation.
A front disc brake collector and a rear drum brake collector were in-
stalled on the right side of the vehicle. The clutch was sealed by
closing the few holes in its casing. The left wheel brakes were left
in their normal configuration and were used to monitor the operation of
the shrouded brakes. Wear debris was taken from the left brakes as well
as from those on the right. The amounts of debris formed and their com-
positions were used to demonstrate that the brake shrouding did not
significantly affect the operation of the brakes on the right side.
Although there are many brake and friction material tests suitable
for measuring a specific condition or combination of conditions, no one
test adequately matches driving conditions which would be representative
of all vehicles. Consequently, it became necessary to devise a rational
and meaningful vehicle test. Seven schedules were chosen, and each was
followed by a measurements procedure (take emissions samples, measure
wear, inspect the systems, and replace worn parts). The first three
schedules - Burnish, After Burnish (A.B.) Baseline, and Detroit Traffic -
constituted low to moderate temperature testing. The final four sched-
ules - 10-Stop Fade, After Fade (A.F.) Baseline, 15-Stop Fade, and Final
Baseline - constituted high temperature and abusive testing.
A detailed step-by-step procedure was prepared for the removal of
brake emissions from the collectors. The amounts of debris collected
at the various locations were used later to calculate the mass balances.
A detailed step-by-step procedure was also prepared for the sampling,
handling, and analysis of the asbestos emissions.
The analysis of brake wear debris indicated the presence of 20-30
weight percent polymeric and carbonaceous material, which in turn pro-
duced a fluffy appearance when the material was examined in the scanning
electron microscope. The organic portion was therefore removed by low
temperature ashing. Two representative samplings were used: the first
in sample selection for low temperature ashing; and the second in sample
selection for distribution on a filter membrane for subsequent analysis.
The only suitable method of analysis for asbestos was microscopy.
At the beginning of the program, one optical and three transmission
electron microscopy methods had been developed by others. Two of the
electron microscope methods were not suitable because they changed the
fiber size distribution of the asbestos. Initial experiments indicated
that the asbestos in wear debris varied in size from 0.1 micron in diame-
ter up to 2.0 microns in diameter by 50 microns in length. To preserve
the particle size distribution, a combination of optical microscopy and
transmission electron microscopy was selected. Optical microscopy with
phase contrast optics at 400 diameters was used to detect fibers with
11-2
-------
diameters of 0.5 micron and above. Transmission electron microscopy at
22,000 diameters was used to detect fibers with diameters of 0.5 micron
and below.
The projected fiber diameter and length were used to determine the
fiber volume. The volumes were summed, converted to weight, and normal-
ized for the entire sample weighed onto the filter. A computer program
was subsequently developed to minimize computational time and to elimi-
nate errors in the processing of these calculations.
The possible sources of error associated with sample processing
and analysis were minimized through the use of statistical methods. The
largest effect found on the asbestos analysis was the occasional occur-
rence of a large fiber. The extent of error increased as the percent
asbestos in the sample decreased. The data showed that the maximum
deviation for results with asbestos contents above 0.10 percent averaged
12-15 percent and had a maximum at approximately 20 percent. The maxi-
mum deviation increased for asbestos contents below 0.10 percent, where
errors for the small amounts of asbestos emissions become less signifi-
cant from the standpoint of air pollution.
A gas handling system was set up to separate, measure, and transfer
samples to the gas chromatograph. A step-by-step procedure was prepared.
The non-condensable gases were analyzed by separating the gases on a
Porapak Q column and then detecting the separated components with a
thermal conductivity detector. In some instances, a flame ionization
detector was also used. The condensable gases were analyzed by separa-
ting the components on a W-98 silicone gum rubber column and detecting
with a flame ionization detector.
The vehicle tests were carried out during the period May 1 to
November 17, 1972. Only one major problem occurred during the vehicle
testing: during the 10-Stop Fade of vehicle test 1, the hardened steel
ring,on which the rotating seal slides, became loose. The ring was re-
anchored and no further problem was encountered during the 15-Stop Fade
or in any further test schedule. This result showed the durability of
the collector and rotating seal design and construction. For the 8100
miles of testing, only seven front and eight rotating seals were required.
This was better than anticipated at the start of the program. The mileage
accumulations for each schedule of each vehicle test showed that the
mileages were reproducible.
Prior to vehicle test 1, a Burnish schedule was performed and the
temperature for the right front disc brake was found to be near 400°F.
The temperature difference, AT, between the right and left front brakes
was 200-250°F. This was unacceptable. The addition of several thermal
control aids reduced the difference to the range 115 to 160°F. Most
important was the reduction of the right front brake operating tempera-
tures from about 400°F to about 300°F. The brake shrouding did not
present any problems on hot days. During the Detroit Traffic Test, the
AT between the front brakes remained between 100 and 140°F while that
for the rear drum brake remained between 10 and 30°F.
11-3
-------
During the fade tests, the right front brake was programmed accord-
ing to known temperature versus stop-number curves obtained for the same
friction materials previously run on an inertia dynamometer and on a
normal test vehicle. After the seventh stop, the time increment between
stops was increased to prevent the right front brake from overheating the
friction materials within the shroud. The 15-Stop Fade produced an addi-
tional effect within the brake. The heat generated was retained within
the shroud and caused the brake fluid within the right front caliper to
heat. The resultant fluid boil produced a loss of pedal for the last
two fade stops and persisted through the first eight recovery stops.
The recovery of particulate emissions from both front brakes
yielded a comparison of the amounts of emissions of the normal with the
shrouded disc brake. For both brakes, the sump sample appeared to reach
and maintain an average amount of debris which was independent of the
mileage. When the debris was removed, the steady-state value appeared
to reestablish itself. The surfaces sample for the open brake showed
the same behavior. The recovery data were used to calculate the distri-
bution weighting factors used later to calculate the distribution of
brake emissions in three categories: retained in the brake, released
as road drop-out material, and airborne material.
The amounts of particulates collected in the three samples were
compared with the friction material weight losses. In all cases, the
data for the right front brake ranged from approximately 42-percent
recovery in the initial schedule of each vehicle test to approximately
70 percent for the final schedules. The low initial recovery may have
been caused by excess gassing during Burnish, resulting in a lower
recovery of particulates. The brake emissions recovered from the fade
tests were "tarry", and the surfaces samples were recovered only with
difficulty.
The material recovery data for the rear brakes showed wide vari-
ation. The problem in part was due to the 80-percent sump carry-over
to the following test. During certain vehicle tests, the sump sample
was redistributed within the brake and registered a lower value after
the test. Thus, a negative weight was recorded. The other samples for
that brake did increase and a positive overall value was always recorded.
The range of asbestos content in the brake emissions for vehicle
tests 1 and 2 went from a high of 1.65 percent to a low of 0.03 percent
for the 90 analyses; only three were above 1.00 percent. The overall
average for vehicle test 1 was 0.38 percent and for vehicle test 2 was
0.25 percent. For vehicle test 3, the range of asbestos content was
from a high of 0.51 percent to a low of 0.003 percent. The overall
average was 0.07 percent.
To provide a systematic independent check on the asbestos analyses,
the EPA Project Officer arranged a second contract for Battelle Columbus
Laboratories to analyze twenty-four samples generated during the program.
Johns-Manville also provided three analyses. The Johns-Manville and
11-4
-------
Battelle data agreed very well. In 19 of the 24 analyses, the Program
results were slightly higher than the corresponding Battelle results.
The Program average was 0.25 percent, while the Battelle average was
0.17 percent or 68 percent of the Program average. The Program data
were expected to be higher for the following reasons: all larger fibers
(bundles of fibrils) found were assumed to be cylinders of projected
diameter and length, and a fiber with an elliptical cross section was
actually smaller in volume than reported; and all fibers were assumed
to be 100-percent asbestos (partially degraded asbestos or olivine
fibers were weak and mechanically reduced to non-fibrous material by
the other analytical techniques, hence only the remaining asbestos
fibrils that remained were counted).
Analysis of the gaseous emissions was made difficult by the large
quantities of water and carbon dixodie which by-passed the gas condition-
ing trap and entered through the rotating seals. Most samples showed
traces of GI to 03 hydrocarbons only as lower concentrations of higher
molecular weight gases could not be detected,. When the gases were con-
centrated from the fade.tests, C^ to Cg compounds such as butanes, ben-
zene, toluene, phenol, and cresols were detected in the gas traps. The
corresponding shroud extracts showed Ci2 to 630 materials, including
cardanol.
To compare the emissions properly, it was found necessary to cal-
culate the asbestos emission factors for each sample in micrograms/mile.
The values of these factors were obtained by multiplying the weights of
brake debris generated by the appropriate asbestos percents, then divid-
ing by the miles per test schedule. Thus, either a high asbestos content
or a large sample gave a high factor. The following .observations were
made:
• asbestos emissions were higher for new friction surfaces and
decreased with use;
• the drum brake produced more asbestos emissions than the disc
brake initially, the difference decreasing as the friction
materials continued in use;
• heavy (abusive) duty did not necessarily give a higher percent
- asbestos, however, the large amount of debris produced gave a
significant rise in asbestos emissions;
• asbestos emissions from the brakes were found to decrease from
fade or heavy-duty stops (highest) to burnish to moderate
braking (lowest);
• for the disc pads only, there was an increase in asbestos emis-
sions with increased asbestos content in the friction material
(there was no such trend for the drum brake materials);
11-5
-------
•
both the front disc pads and the drum linings of vehicle test 3
have wear comparable to that found in the other two vehicle
tests, yet the asbestos emissions were significantly lower
(both pads and secondary linings contained brass chips which
may have been in part responsible for the more complete con-
version of the asbestos in the brake emissions); and
for both disc and drum brakes, the surfaces sample was the
largest of the three (^92 percent), the sump sample was next
percent) , and the airborne sample was the smallest (VL percent) ,
Each fade schedule included the 12-stop recovery and a 35-stop reburnish.
It was expected that the recovery and reburnish stops would remove the
heat-damaged rubbing surfaces of the friction materials. However, both
the A.F. Baseline and Final Baselines show an average increase of 250 per
cent more wear over their approximately 350 miles or approximately 1500
stops. These data indicate that many stops were necessary to produce a
renewed surface.
The end objective of this report was to develop the best possible
estimate of total brake and clutch emissions per year for the U.S. popu-
lation of braked vehicles in use. A data base was obtained from a wide
variety of trade publications and from industry and government contacts.
The number of vehicles given and the other data presented indicated a
wide and varied usage so that some assumptions had to be made in prepar-
ing the asbestos emissions estimates.
The asbestos content in brake friction materials was given by the
two most knowledgable industry sources as 90 and 120 million pounds for
1972. In the program our calculations, ^118 million pounds was used.
These ^118 million pounds of asbestos were incorporated in 171 million
pounds of brake friction materials. A calculation gave the total brake
friction material worn away as 117 million pounds per year. The program
calculation for the asbestos content in clutch friction materials was
4.38 million pounds in 8.76 million pounds of friction material. A
calculation gave the total clutch friction material worn away as 6.56
million pounds.
Two series of weighting factors were developed. The distribution
weighting factors were calculated from the material recoveries in the
shrouded and unshrouded brakes as indicated earlier. Estimates were
made for both disc and drum brakes from the test vehicle for the amounts
of the different samples distributed from the brakes. These estimates
were made for the Burnish schedule, for the end of a complete vehicle
test, and for the end of all three vehicle tests. For the drum brake,
estimates were made for up to 40,000 miles. The severity weighting
factors were calculated from the percentages of different braking modes:
for new versus burnished friction materials, for severe (or abusive)
versus moderate braking, and for the renewal of friction surfaces (post-
fade) .
11-6
-------
The total asbestos emissions estimate for the test vehicle was
calculated from the asbestos emissions factors and the severity weight-
ing factors. The average asbestos emissions factors for the disc brakes,
drum brakes, and clutch were used along with the Burnish (new surfaces),
A.B. Baseline (surfaces preparation), Detroit Traffic (moderate braking),
10-Stop Fade (severe braking) and A.F. Baseline (surface renewal) weight-
ing factors. The value obtained for the test vehicle was 28.51 yg/mile.
The total asbestos emissions were not considered to be merely
dumped onto the ground or thrown into the atmosphere. The fates of the
emissions were calculated with the use of the distribution weighting
factors as follows:
Road Drop-out 81.9 percent
Airborne 3.7 percent
Brake Retention 14.4 percent
The annual total asbestos emissions estimate for 96,400,000 passen-
ger vehicles travelling .an average of 9,978 miles per year was found to
be 60,400 pounds distributed as follows:
Road Drop-Out 49,470 pounds
Airborne 2,230 pounds
Brake Retention 8,700 pounds
60,400 pounds
Truck brakes usually tend to generate and to operate at higher
temperatures than passenger cars. To estimate asbestos emissions for
light, medium, and heavy trucks, it was found necessary to adjust the
severity under which the emission would be expected to occur. The
severity weighting was obtained by using a larger fraction of the 10-
Stop Fade (and A.F. Baseline) asbestos emissions according to the
following progression:
Passenger car 2.0 percent
Light truck 5.0 percent
Medium truck (and bus) 10.0 percent
Heavy truck 15.0 percent
In addition, it was necessary to estimate the asbestos emissions factors.
Assuming that these factors were roughly proportional to the increased
friction material weights of the appropriate vehicles compared to the
test vehicle, the following estimated factors were determined:
Front Rear
Drum Brake Drum Brake Clutch
Light truck 2.0 3.0 2.0
Medium truck (and bus) 3.0 10.0 4.0
Heavy truck 5.0 30.0 6.0
11-7
-------
The annual total asbestos emissions estimates for light trucks,
medium trucks (and buses) and heavy trucks were found to be:
Light trucks 32,300 pounds
Medium trucks (and buses) 16,300 pounds
32,900 pounds
Heavy trucks
81,500 pounds
The distribution weighting factors for trucks were calculated based
on the following considerations. The truck drum brake is designed to be
more open than the car drum brake and in many instances no splash shields
are used. Based on the estimates, that only about 25 percent as much
debris remains in a truck drum brake as compared to a passenger car drum
brake, distribution weighting factors for trucks were estimated. The
distribution of the total asbestos emissions estimate was as follows:
Road Drop-Out
Airborne
Brake Retention
87.9 percent
2.9 percent
9.2 percent
The summary of the estimated asbestos emissions for all vehicles
in pounds/year was calculated as follows:
Passenger Cars
Light Trucks
Medium Trucks
(and buses)
Total Asbestos
Emissions
60,400
32,300
16,300
Distribution
Drop-Out Airborne Retention
49,470
28,420
14,330
2,230
940
470
8,700
2,940
1,500
Heavy Trucks
Miscellaneous
Distribution by
32,900
16,300
158,200
percent :
28,920
14,330
135,470
85.6%
950
470
5,060
3.2%
3,030
1,500
17,670
11.2%
These estimates should be considered as maximum values.
The total asbestos emission estimates, and especially the airborne
emissions estimate, are considerably lower than the 540,000 pounds esti-
mated by IIT Research Institute. (ia~1;L)
11-8
-------
APPENDIX A
WEAR DEBRIS CALCULATIONS
A.I INTRODUCTION
This appendix discusses friction material reactions used to estimate
amounts of wear debris which were expected to have been collected during
various cycles of the "Brake Emissions" program. Consideration is given
to both disc and drum brakes.
A. 2 FRONT DISC BRAKE
A. 2.1 Composition
From previous studies, the typical composition of a disc
pad can be approximated:
Resin -\
Cashew I
Rubber J
Asbestos
Zinc
^32 wt %
^64 wt %
^4 wt %
A.2.2 Burnished Products
From various studies, the following amounts of burnished
products can be estimated.
« Particulates Gravimetric
Factor
Resin ^ Carbonaceous
Cashew I ^32 wt % -> Binder 0.50
Rubber J ^16 wt % (from TGA)
Asbestos ^64 wt % -»• Olivine 0.86
^55 wt % (from TGA)
Zinc ^4 wt % -»• ZnO 1.25
^5 wt % (from TGA)
Total 76 wt %
Consequently, the expected amount of particulate wear debris expected
is 76% of the weight lost. Although disc wear does occur, it cannot be
estimated at this time.
• Gaseous Products
The average organic molecule can be assumed
to have the structure:
A-l
-------
— GIL
C9H1()ON
CH = CH-NH
which undergoes the following oxidation reaction:
C9H1QON + 11.5 02 -»• 9 C02 + 5 H20 + NO
MW = 148 MW = 32
From the above calculation, only 50% of the organic portion oxidized:
32 wt % x 0.50 = 16 wt
which gives 16/148 = 0.108 mole of organic oxidized. This requires:
11.5 x 0.108 = 1.24 moles of 0,
1.24 x 32.0 = 39.7 gins of 0,
Total amount of material reacting:
16.0 + 39.7 = 55.7 gms
Conversion factor is:
55.7
16.0
= 3.48
A-2
-------
Since not all 16.0 gms of the organic portion will be completely oxidized
to gases, this value represents a maximum amount of material expected.
The expected amount of gaseous wear products is 56% of the weight lost.
A.2.3 Typical Disc Brake Wear Rates
Burnish: ^0.007" or ^0.018 cm
Detroit Traffic: ^.020" or ^0.051 cm
SAE Fade: M3.030" or ^0.076 cm
7 Stop, 90 mph: ^0.015" or ^0.038 cm
A.2.4 Disc Pad Area
2
Inner: 8.50 in
Outer: 11.25 in2
19.75 in2
19.75 in2 x (2.54 cm/in)2 = 127.5 cm2
A.2.5 Calculated Wear During Burnish
Area x Thickness - 127.5 x 0.018 = 2.30 cc
Typical S.G. for disc pad is 1.70
Calculated weight loss:
2.30 x 1.70 = 3.91 gms
« Particulate Portion
3.91 x 0.76 = 2.97 gms
which will be collected in four areas:
sump
brake surfaces
8.0M filter
0.2y filter
A-3
-------
Gaseous Portion
3.91 x 0.56 = 2.19
which will be collected in three traps:
Wear Particulates
(inch/cm) (gms)
affic
mph
0.007/0.018
0.020/0.051
0.030/0.076
0.015/0.038
2.97
8.47
12.70
6.36
Gases
(gms)
2.19
6.26
9.38
4.68
Total
5.16
14.73
22.08
11.04
one condensable gas trap
two noncondensable gas traps filled with charcoal
Total Sample Expected
2.97 + 2.19 = 5.16 gms.
A.2.6 Summary of Typical Wear Expected
Test
Burnish
Detroit Ti
SAE Fade
7 Stop, 9(
A.3 REAR DRUM BRAKE
A.3.1 Composition
From previous studies, the typical compositions of primary
and secondary linings can be approximated:
Primary Secondary
Resin "\
Cashew j 28 31
Asbestos 72 69
A.3.2 Brake Parameters
Designation: 11 x 2-1/4" DSSA
Primary Area: 2.25" x 8.8" (average arc length)
= 19.8 in2
Secondary Area: 2.25" x 11.5" (average arc length)
= 25.9
A-4
-------
higher torque stops.
(The total lining length is 8.8 + 11.5 = 20.3". The actual
drum circumference is 3.14 x 11" = 34.6". Thus the lining sweeps 20.3/
34.6 x 100 = 59% of the available drum surface.)
A.3.3 Burnished Products
Because the secondary is programmed to absorb more torque
and essentially wear more throughout the lining combination's usage, and
because the primary and secondary wear debris contributions are always
combined, a more typical starting composition for the combination must
be slanted toward the secondary's composition analysis:
iin ^
ihew f
*esjn I 30 wt %
Cashew
Asbestos 70 wt %
The following amounts of burnished products can be estimated:
• Particulates
Gravimetric
Factor
Resin \ or> „/ Carbonaceous
_ , 7 JU Wt 7o "*•„., r\ cr\
Cashew J Binder 0.50
^15 wt %
Asbestos 70 wt % -> Olivine
^62 wt % 0.90
77 wt %
• Gaseous Products
The average organic molecule can be assumed to be:
OH
I C10H10°2
OH
A-5
-------
which undergoes the following oxidation reaction:
C10H10°2 + n'5 °2 * 10C°2 + 5H2°
MW = 162
Since only 50% of the organic portion is oxidized, i.e., 15 wt %, this
corresponds to 15/162 = 0.093 mole oxidized which in turn requires 11.5 x
0.093 x 32 = 34.3 gms of oxygen. The total amount of reactants is 15.0 +
34.3 = 49.3 gms which represent a gravimetric factor equal to:
15.0
A. 3. 4 Typical Drum Rear Wear Rates
Burnish: MD.005" or ^0.013 cm
Detroit Traffics 0.010" or 0.026 cm
SAE Fade: ^0.008" or ^.020 cm
7 Stop, 90 mph: 0.005" or 0.013 cm
A. 3. 5 Drum Brake Lining Areas
Primary: 19.8 in2
Secondary: 25.9 in^
45.7 in2
45.7 in2 x (2.54 cm/in)2 = 297 cm2
A.3.6 Calculated Wear During Burnish
Volume = Area x Thickness
= 297 x 0.013
= 3.86 cc
Typical S. G. is 1.70
Calculated weight lost:
3.86 x 1.70 = 6.56 gms
A-6
-------
• Particulate Portion
6.56 x 0.77 = 5.15 gms
« Gaseous Portion
6.56 x 0.49 = 3.21 gms
« Total Wear Debris
5.15 + 3.21 = 8.36 gms
A.3.7 Summary of Typical Wear Expected
Test
Burnish
Detroit Traffic
SAE Fade
7 Stop, 90 mph
Wear
(inch/cm)
0.005/0.013
0.010/0.026
0.008/0.020
0.005/0.013
Particulates Gases Total
(gms) (gms) (gms)
5.15 3.21 8.36
10.30 6.42 16.72
8.24 5.13 13.37
5.15 3.21 8.36
A-7
-------
APPENDIX B
NUCLEPORE FILTER FLOW CHARACTERISTICS FOR BRAKE LINING WEAR DEBRIS
B.I INTRODUCTION
This appendix describes a series of experiments used to define the
filter flow characteristics of Nuclepore membranes with varying loadings
of brake lining wear debris. Figure B-l is a schematic of the experi-
mental setup.
B.2 FLOW VERSUS PRESSURE DROP
Table B-l is the compilations of flow versus pressure drop data
for both unloaded filters and loaded filters containing approximately
1.0 gram of wear debris (from a 1970 Chrysler Imperial rear drum brake).
This data is plotted in Figure B-2.
B.3 FLOW AND PRESSURE DROP VERSUS LOADING
Table B-2 is the flow and pressure drop variations versus filter
loading data at a fairly high initial pressure drop setting while
Table B-3 is similar data for a lower initial pressure drop. The data
are plotted in Figure B-3. The initial and final (with approximately
1 gram loading) pressure drops and flows for this data are identified
as Runs 3 and 4 on Figure B-2.
B.4 MATERIAL BALANCE DATA
Additional Table B-2 Data:
• Amount of debris added to system: 1036.0 mg
Amount of debris collected on filters: 1000.6
'If " - — - -
Amount of debris lost in system : 35.4 mg
*
some spillage, most remains on
walls of tube leading from
funnel to filter holder.
• Removal of 8y membrane from under debris
after light shaking: 15.3 mg
Original weight: 14.1
Amount remaining on filter: 1.2 mg
• Removal of 8y membrane from under debris
and air blow: 14.7 mg
Original weight: 14.1
Amount remaining on filter: 0.6 mg
B-l
-------
MERCURY
MANOMETER
FUNNEL
8/J FILTER
FLOWMETER
CONTROLLED
LEAK
PUMP
Figure B-l - Sketch of Experimental Setup for Defining Filter Flow
Characteristics of Nuclepore Membranes
B-2
-------
Table B-l - Flow Versus Pressure Drop Data
Unloaded Filter?
Run 1
Flow (CFIi)
0.9
2.3
3.8
5.9
7.7
9.7
11.0
12.0
AP (cm Hg)
1.0
3.4
6.2
11.0
16.6
23.9
28.9
33.4
Run 2
Flow (CFM)
0.9
2.3
3.8
7.7
9.7
AP (cm Hg)
1.0
3.7
6.5
17.1
24.2
Loaded Filter
Run 1
Flow (CFII)
0.9
2.0
3.0
4.0
5.0
7.0
9.0
11.0
12.0
AP (cm Hg)
1.0
3.1
4.1
7.2
9.6
15.2
22.7
30.6
35.6
12'
10'
UNLOADED:
• RUN 1
A RUN 2
O RUN 3
O RUN 4
LOADED
O RUN 1
• RUNS
• RUN 4
12 16 20
PRESSURE DROP (CM HG)
24
28
32
36
Figure B-2 - Plot of Flow Versus Pressure Drop
B-3
-------
Table B-2 - Flow and Pressure Drop Versus Loading Data
Wear Debris
Reservoir Weight
(gm)
13.0160
13.0025
12.9744
12.9528
12.8883
12.7911
12.5590
12.3547
11.9800
AW
(rag)
—
13.5
28.1
21.6
64.5
97.2
232.1
204.3
374.7
Filter
Loading
(mg)
0.0
13.5
41.6
63.2
127.7
224.9
457.0
661.3
1,036.0
Pressure Drop
(cm Hg)
52.7 - 27.6 = 25.1
51.4 - 28.8 = 22.6
51.3 - 28.9 = 22.4
51.1 - 29.2 = 21.9
50.7 - 29.6 = 21.1
50.4 - 29.9 = 20.5
50.3 - 30.0 = 20.3
50.1 - 30.2 = 19.9
50.0 - 30.3 = 19.7
Flow
(CFM)
9.4
9.0
9.0
8.8
8.7
8.4
8.3
8.2
8.0
25-7
C3
X
o
0.
o
oc
a
UJ
cc
UJ
oc
a.
15
10'
20
O PRESSURE DROP
A FLOW
40 60
FILTER LOADING (MG)
80
10
H
-n
100
Figure B-3 - Plot of Pressure Drop and Flow Versus Filter Loading
B-4
-------
Table B-3 - Flow and Pressure Drop Versus Loading Data
Wear Debris
Reservoir Weight
(gm)
13.7892
13.7741
13.7590
13.7416
13.7012
13.5552
13.3928
13.5198
12.8014
AW
(mg)
—
15.1
15.1
17.4
40.4
146.0
162.4
233.0
358.4
Filter
Loading
(mg)
0.0
15.1
30.2
47.6
98.0
234.0
396.4
629.4
987.8
Pressure Drop
(cm Hg)
43.3 - 36.9 = 6.4
43.3 - 36.9 - 6.4
43.2 - 36.9 = 6.3
43.2 - 36.9 = 6.3
43.2 - 36.9 - 6.3
43.2 - 36.9 - 6.3
43.2 - 37.0 = 6.2
43.2 - 37.0 = 6.2
43.2 - 37.0 = 6.2
Flow
(CFM)
3.8
3.7
3.7
3.7
3.7
3.7
3.7
3.7
3.6
Additional Table B-3 Data:
• Removal of 8y membrane from under debris
after light shaking and air blow:
Original weights
Amount remaining on filter:
• Weight of funnel plus tubing plus debris:
Weight of funnel plus tubing:
Weight of debris trapped:
B.5 CONCLUSIONS
14.9 mg
13.4
0.6 mg
43,187.0 mg
43,144.8
42.2 mg
• The flow rate through the filters is fairly reproducible
for different membranes.
• Gas flow is proportional to pressure drop.
2
• Initial 1 to 2 mg/cm loading reduces flow slightly
(^10 percent).
2
• Higher loading (up to 100 mg/cm ) reduces flow an
additional 10 percent.
* Wear debris can be separated from membrane and stored
in a vial without any significant loss.
-------
Minimal losses will occur in the heated transfer line
between the shroud and the filter holder.
Over-all filter setup chosed for this project appears
to operate satisfactorily for approximately 1 gram of
collected debris. Larger amounts will require a pre-
filter of several filter changes.
B-6
-------
APPENDIX C
COLLECTION OF BRAKE AND CLUTCH EMISSIONS
Sequence Description
1 Preparation of Collection Systems (Table C-l)
2 Installation of Collection System, on Test Vehicle (Table C-2)
3 Preparation of Vehicle for Test (Table C-3)
4 Vehicle Test (Table C-4)
5A Removal of Particulate Filters and Gas Collectors from
Vehicle (Table C-5)
5B Removal of Wear Debris from Disc Brake Emissions Collector
(Table C-6)
5C Removal of Wear Debris from Drum Brake Emissions Collector
(Table C-7)
5D Removal of Wear Debris from Clutch Emissions Collector
(Table C-8)
6 Transfer of Samples to Analytical Laboratories (Table C-9)
C-l
-------
n
Table C-l - Preparation of Collection System for Vehicle Test - Sequence 1
Operation
Location
Responsibility
Remarks
Gas Collection System
Rinse interior of condensable gas trap
(only) with toluene (three rinses;
^25 cc per rinse). Air dry. Assemble
trap train. Check all connections.
Heat trap train in vacuum oven at
100°C for one hour at vacuum (all
valves open).
Remove from oven and close valves.
Clean, Label, and Weigh Vials
Particulate Filter Holders
Remove 0-ring, wipe clean with
toluene. Air dry.
Rinse filter holders with toluene
until clean. Air dry.
Replace 0-ring in holder.
Weigh filter membranes.
Reassemble particulate collection
system.
Laboratory
Laboratory
Laboratory
Laboratory
Technician
Technician
Technician
Technician
Laboratory
Laboratory
Laboratory
Technician
Technician
Technician
Remove high molecular
weight materials.
Remove residual gases
from previous test.
For wear debris:
Sump sample
Surfaces sample
Additional
Removes sludge.
From desiccator.
-------
Table C—2 - Installation of Collection Systems - Sequence 2
n
Operation
Pick Up Gas Collection Systems (3) ,
Particulate Filter Holders (3) , and
Vials with Laboratory Cart.
Cover with plastic sheet for
transportation to garage.
Install Gas Collection Systems
(Three Systems)
Connect ends
Connect thermocouples
Check temperatures
Check inlet air drier and filters
Install Particulate Filter Holders
(Three Systems)
Hoist vehicle
Connect ends, pack insulation,
tighten clamp
Connect thermocouples
Connect heater
Check heating (50% power)
Record temperatures
Assemble Emissions Collectors
Front
Rear
Clutch
Location
Laboratory/
Garage
Garage
Garage
Garage
Responsibility
Driver
Driver
Driver
Driver
Remarks
Handle with care during
transportation.
Front Brake 1 or 2
Rear Brake 3 or 4
Clutch 5 or 6
(1, 3, 5 or 2, 4, 6 are
on the same tests - do
not change or mix.)
-------
n
-P-
Table C-3 - Preparation of Vehicle for Test - Sequence 3
Operation
Prepare Record Sheets
Check Vehicle (Gas, Oil, Tires, Etc.)
Fill Trap Boxes With Dry Ice
Fill Dry Ice Storage Box (in
Vehicle Trunk)
Check Trap Temperatures
Front
Rear
Clutch
Check Battery and Inverter Electrical
System
Check Thermocouples, Brake Counter,
Brake Gages, etc.
Disconnect Battery Charger
Start Engine, Restart Inverter,
Record Odometer
Adjust Air Flows
Front
Rear
Clutch
Location
Office
Garage
Garage
Garage
Garage
Garage
Garage
Garage
Garage
Garage
Responsibility
Driver/
Test Engineer
Driver
Driver
Driver
Driver
Driver
Driver
Driver
Driver
Driver
Remarks
Review scheduled test.
Handle with scoop or
gloves.
Must be colder than
-70°C (-94°F).
To ensure safe engine
start.
To ensure proper collec-
tion efficiency.
-------
Table C-4 - Vehicle Test - Sequence 4
Operation
O
In
Check Vehicle Test Record Sheets
Drive to Test Area
Record Time, Mileage, Reset Brake
Counter
Record All Temperatures and Air Flows
Perform Test
Monitor Brake Temperature Balances (R to L)
Record Maximum and Minimum Temperatures
Monitor Emissions
Collectors:
Check flows
Check temperatures
Cold Boxes
Particulate heaters
Return Vehicle to Garage With Brake
Temperatures Below 200°F.
Location
Vehicle
Vehicle
Vehicle
Vehicle
Vehicle
Vehicle
Vehicle
Vehicle
Vehicle
Responsibility
Driver/ -
Test Engineer
Driver/
Test Engineer
Driver
Driver
Driver
Driver
Remarks
Prepared prior to test.
Periodically
Periodically
Periodically
Periodically
-------
n
ON
Table C-5 - Removal of Partlculate Filters and Gas Collection from Vehicle - Sequence 5A
Operation
Park Vehicle in Garage Over Hoist
Stop Engine
Record Odometer and Brake Counter
Close All Valves in Gaseous
Collection System
Turn Off Heaters
Close Garage Door
Check Gaseous Collection System and Top
Up Dry Ice
Remove Gaseous Collection Systems and
Place on Cart (Clean)
Hoist Vehicle
Remove Particulate Collection Systems and
Place on Cart (Onto Shock-Proof Pad) .
Location
Garage
Garage
Garage
Garage
Garage
Garage
Garage
Garage
Garage
Garage
Responsibility
Driver
Driver
Driver
Driver
Driver
Driver
Driver
Driver
Driver
Driver
Remarks
Immediately after com-
pletion of test.
Immediately after com-
pletion of test.
immediately after com-
pletion of test.
Immediately after com-
pletion of test.
Immediately after com-
pletion of test.
Immediately after com-
pletion of test.
Immediately after com-
pletion of test.
Check and ensure valves
are closed. Label lo-
cation and run number.
Handle with care. Do
not bump.
-------
Table C-6 - Removal of Wear Debris from Disc Brake Emissions Collector - Sequence 5B
Operation
Location
Responsibility
Remarks
Adjust Vehicle on Hoist
Remove Wheel. Visually Inspect Collector
and Rotating Seal.
Clean Exterior Surfaces.
Spread 4x5 foot Clean Plastic Sheet
Below Wheel Well.
Spread 12" x 18" Clean Plastic Sheet Under
Collector Shroud. Place Clean Vial Onto
Sheet.
Carefully Remove
Rubbing seal and inspect
Screws
Outboard shield
Vacuum Debris From Outboard Shield, Rotor,
and All Other Brake and Collector Surfaces
onto 0.2p Nuclepore filter. Remove Caliper
Cover Plate and Vacuum. Transfer Filter
to Vial.
Garage
Garage
Garage
Garage
Garage
Garage
Garage
Driver
Driver
Driver
Driver
Driver
Driver
Technician
Wheels should be 1 to
2 inches above floor.
Record observation.
To protect clean smaller
sheet to catch debris.
To catch wear debris.
Vial previously cleaned
and weighed.
Record inspection.
Label:
Location
Surfaces Sample
Vehicle Test No.
Schedule
o
i
(1 of 2)
-------
n
00
Table C-6 - Removal of Wear Debris from Disc Brake Emissions Collector - Sequence 5B
Operation
Location
Responsibility
Remarks
Replace Plastic Sheet Under Open
Collector.
Garage
Remove Both Caliper Bolts and Remove
Caliper. Vacuum the Pad Debris Onto 0.2y
Nuclepore Filter. Vacuum Wear Debris From
Rivet Holes and From Inside of Caliper
Piston.
Remove Pads From Shoes.
Dry, Weigh and Mike the Pads
Reassemble Brake and Collector.
Garage
Laboratory
Laboratory
Garage
Technician
Technician
Technician
Driver
Driver
Label:
Location
Sump Sample
Vehicle Test No.
Schedule
Weigh to nearest 0.01 gm.
Use SAE micrometer
procedure.
(2 of 2)
-------
Table C-7 - Removal of Wear Debris From Drum Brake Emissions Collector - Sequence 5C
Operation
Location
Responsibility
Remarks
Remove Wheel. Visually Inspect Rotating
Seal.
Clean Exterior Surfaces.
Spread 4' x 5' Clean Plastic Sheet
Below Wheel Well.
Spread 12" x 18" Clean Plastic Sheet
Under Collector (Shroud).
Carefully Remove Drum and Set Down With
Opening Facing Up.
Collect Sump Sample Including Debris From
Brake Shoe Rivet Holes and Place Into Vial.
Vacuum Brake Surfaces and Drum Interior
Onto 0.2y Nuclepore Filter. Collect
Wear Debris on First Plastic Sheet and
Put Into Vial. Dismantle Brake and
Vacuum all Parts. Vacuum Backing Plate.
Transfer Filter.
Garage
Garage
Garage
Garage
Garage
Garage
Driver
Driver
Driver
Driver
Driver
Technician
Garage
Technician
Record observations.
Label:
Location
Sump Sample
Vehicle Test No.
Schedule
Label:
Location
Surfaces Sample
Vehicle Test No.
Schedule
n
vo
(1 of 2)
-------
Table C-7 - Removal of Wear Debris From Drum Brake Emissions Collector - Sequence 5C
Operation
Remove Linings From Shoes .
Dry, Weigh, and Mike Linings.
Reassemble Braise .
Return 80% of Sump Wear Debris to
Drum Surface.
Replace Drum Assuring that no Debris
Falls Out.
Reassemble Collector (Shroud)
Components
Location
Garage
Garage
Garage
Garage
Garage
Responsibility
Driver
Driver
Driver
Driver
Driver
Remarks
Record weights.
Wipe away any hydraulic
oil.
Need for drum grinding
action.
(2 of 2)
-------
Table C-8 - Removal of Wear Debris From Clutch Emissions Collector - Sequence 5D
Operation
n
Adjust Vehicle Height.
Carefully Clean Exterior Surfaces
Spread 4' x 5' Clean Plastic Sheet
Below the Clutch.
Spread 12" x 18" Clean Plastic Sheet
Under Clutch
Remove Clutch Cover.
Vacuum Debris Onto 0.2y Nuclepore Filter.
Transfer to Vial.
Carefully Vacuum. All Other Surfaces
Wear Debris.
Weigh and Mike the Clutch Facing Assembly
(at Start of First Vehicle Test and at
Finish of Last Vehicle Test).
Reassemble Clutch and Collector (at Start
of First Vehicle Test and at Finish of
Last Vehicle Test).
Location
Garage
Garage
Garage
Garage
Garage
Garage
Garage
Garage
Garage
Respons ib illty
Driver
Driver
Driver
Driver
Driver
Driver
Driver
Driver
Driver
Remarks
Label:
Location
Sump Sample
Vehicle Test No.
Schedule.
Caution: oil mist on
surfaces.
Label:
Location
Surfaces Sample
Vehicle Test No.
Schedule
Record weight.
-------
N>
Table C-9 - Transfer of Samples to Analytical Laboratories - Sequence 6
Operation
Location
Responsibility
Remarks
Ensure All Samples are on Cart and
Protected From Possible Shaking in
Transfer to Labs
Cover Cart With Plastic Sheet
Transfer Cart and Samples to Analytical
Lab
Check-In All Samples and Verify
Identification
Garage
Garage
Laboratory
Laboratory
Technician
Technician
Technician
Technician
Report to project
engineer
-------
Sequence
APPENDIX D
ANALYSIS OF BRAKE AND CLUTCH EMISSIONS
7A Process Particulate Filters (for Material Balance Considera-
tions) (Table D-l)
7B Redistribution of Particulates for Microscopy (Table D-2)
8A Particulate Analysis by Optical Microscopy (Table D-3)
8B Particulate Analysis by Electron Microscopy (Table D-4)
9 Asbestos Emissions and Size Distribution (Table D-5)
10A Noncondensable Gaseous Emissions Processing (Table D-6)
10B Analysis of Noncondensable Gaseous Emissions (Table D-7)
11A Condensable Gaseous Emission Processing (Table D-8)
11B Analysis of Condensable Gaseous Emissions (Table D-9)
12 Total Gaseous Emissions (Table D-10)
D-l
-------
Table D-l - Processing Particulate Samples - Sequence 7A
Operation
Location
Responsibility
Remarks
Airborne Samples
Remove Filter Membrane From Filter
Holders Over Clean 12" x 12" Plastic
Place Filter Membranes Into Clean
Vial. Brush Loose Debris Into Vial.
Accumulate Filter Membranes Pertinent
to Same Test.
All Samples
Desiccate All Filter Membranes and Vials
of Particulates.
Weigh All Samples
Select Samples for Division for
Battelle. Divide samples, Pack,
and Ship.
Low Temperature Ashing (LTA)
Randomly Select 20 to 50 mg of Wear
Debris From Vial and Distribute in
Thin Layer Over LTA Boat.
Insert Into LTA. Initiate Plasma.
Remove After 7 Hours and Redistribute
Wear Debris in Boat.
Insert Into LTA. Initiate Plasma and
Remove After Further 17 Hours.
Redistribute Wear Debris and Insert
Into LTA for additional 24 Hours.
Laboratory
Laboratory
Laboratory
Laboratory
Laboratory
Laboratory
Laboratory
Laboratory
Laboratory
Laboratory
Technician
Technician
Technician
Technician
Project Engineer
Technician
Technician
Technician
Technician
Technician
Technician
Use extreme care. Work in
draft-free, ultra—clean area.
Some vehicle tests may have
two or more filter sets
(i.e., Detroit Traffic Test).
Record on test sheet.
Record selections. Use
extreme care.
Record weight and time.
Expose new surfaces to
plasma.
Record weight loss after
48 hours elapsed LTA time.
-------
Table D-2 - Redistribution of Particulates for Microscopy - Sequence 7B
Operation
Location
Responsibility
Remarks
For each LTA Sample Weigh 0.55 + 0.05 mg
Onto Tiny Platinum Boat by Taking Several
M).05 mg Fractions from LTA Sample.
Suspend in 100 cc of 1:1 MethanoliMEK in
250 cc Beaker
Filter Onto 47 mm O.D. 0.2u Nuclepore
Membrane:
Swirl Solution and Rapidly Pour Into
Funnel.
Start Vacuum and Then Stop Solution
Level About 1/2 cm above Filter.
Wash Down Beaker and Add to Funnel
Start Vacuum and Again Stop Level
1/2 cm above Filter.
Wash Down Funnel Sides with Solvent.
Allow Last Wash to Filter to
Completion.
Cover Top of Funnel with a Clean
Petri Dish Top and Pull Vacuum
for 5 Minutes.
Remove Filter and Store in Petri Dish.
Laboratory
Laboratory
Laboratory
Laboratory
Laboratory
Laboratory
Laboratory
Laboratory
Laboratory
Technician
Technician
Technician
Technician
Technician
Technician
Technician
Technician
Technician
Preserve sample distribution.
Use pre-filtered solvent. Use
very clean beaker (rinsed with
solvent).
Preserve random distribution.
Do not allow to dry. Use 3-way
stopcock to control vacuum.
Do not allow to dry. Use 3—way
stopcock to control vacuum
Cover keeps dirt out. Can also
be used in above steps between
washings.
Insure sample is labeled properly.
-------
u
-P-
Table D-3 - Particulate Analysis by Optical Microscopy - Sequence 8A
Operation
Sample Preparation
Insure Dust and Draft-Free Ambient
Conditions.
Label a Clean Slide With a Frosted
End for Easy Sample Identification.
Rinse With Filtered Acetone.
Place 1 Drop of Solution With
Refractive Index 1.585 in Center of
Slide and Smear Into a Shape Corres-
ponding to a Typical Filter Section.
Cut a Circular Section From Nuclepore
Filter. Handl With Forceps. Place
Nuclepore Filter on Top of Solution
on Glass Slide.
Cover with Corning No. 1 Cover Slip
(24 x 40 mm) to Flatten the Filter
Paper and Hold the Mounting Medium
in Place.
Store Sample in a Petri Dish or Slide
Box Until Counting Takes Place.
Location
Metallurgical Lab.
Metallurgical Lab.
Metallurgical Lab.
Metallurgical Lab.
Metallurgical Lab.
Metallurgical Lab.
Responsibility
Microscopist
Microscopist
Microscopist
Microscopist
Microscopist
Microscopist
Remarks
To reduce static charge of
filters, use either of the
following:
a-emitter such as those sold
by photographic houses to clean
camera lenses.
Ether-soaked swabs passed in
air over the filter so that
vapor will dissipate charge.
Remove all bubbles.
(1 of 2)
-------
Table D-3 - Particulate Analysis by Optical Microscopy - Sequence 8A
Operation
Location
Responsibility
Remarks
Counting Procedure
Fill Out Count Sheet (Exhibit D-I).
Set Up Microscope With Heine Phase-
Contrast Optics at 400X.
Calibrate the Microscope by the
Following Procedure. The Length of the
Large Reticle is 200 L Units. By Measur-
' ing the Actual Length of the Rectangle
Using the Stage Micrometer and Dividing
This Value by 200, the Value of L at the
Magnification is Obtained.
Place a Sample Slide on the Stage and
Focus on the Top Surface of Filter.
The Total Fiber Count Should be at
Least 100 Fibers or 100 Fields, Which-
ever is Less.
Count All Fibers Crossing the Limits
of the Counting Field on Two Adjacent
Sides (Top and Left).
Record the Counts Into the Various
Size Ranges Given on the Count Sheet.
Laboratory
Metallurgical Lab.
Metallurgical Lab.
Project Engineer
Microscopist
Microscopist
Metallurgical Lab.
Microscopist
Metallurgical Lab.
Microscopist
With this value for L, the actual
diameter for each circle and the
length of each individual area
can be obtained for fiber sizing.
This sketch shows the distribution
of 100 fields over several areas
easily scanned by stage movement.
During the count of each field, it is
important to constantly adjust the
fine focus back and forth. This
brings into focus the fibers that
might not be seen otherwise.
(2 of 2)
Ui
-------
Table D-4 - Particulate Analysis by Electron Microscopy - Sequence 8B
Operation
Location
Responsibility
Remarks
Sample Preparation
Cut Out a 1/2 inch Filter Circle of
Nuclepore Filter With a Special
Cutter and Mount on a Glass Microscope
Slide With Scotch Tape.
Coat the Piece of Filter with Carbon
in a Vacuum Coater.
Metallurgical Lab.
Metallurgical Lab.
Technician
Technician
Use a Drop of Diffusion Pump Oil on
Porecelain Plate to Determine Carbon
Film Thickness.
Prepare Copper Grids (400 Mesh).
For Each Filter Sample, Place 2 to 3
Grids Onto a 3/8 Inch High Polyurethane
Foam Block Sitting in Chloroform in a
Petri Dish. The Surface of the Chloroform
is About 1/8 Inch From the Top of the
Polyurethane Block.
Cut a 1/8 Inch Diameter Disc (the Size
of the Specimen Grid) From the Carbon-
Coated Filter With a Sharp Specially-
Made Boring Tool.
With a Pair of Tweezers, Place the Carbon-
Coated Filter Disc With Carbon Side Down
Onto the Grid.
Metallurgical Lab.
Metallurgical Lab.
Metallurgical Lab.
Technician
Technician
Technician
Metallurgical Lab.
Metallurgical Lab.
Technician
Technician
Use thin strip (1/4 inch wide)
tape to hold filter.
Pieces from 4 samples mounted
on one slide and a total of 12
pieces on 3 different slides can
be coated in one operation. Ladd
Industries carbon appears to be
best A 1 x 4 ran rod is used.
Color development should be dark
yellow to yellow-brown.
The tool is machined from tool
steel and hardened to the level
of surgical steel.
This is a tricky operation: must
place one edge down first and then
rapidly lay down the other.
(1 of 3)
-------
Table D-4 - Particulate Analysis by Electron Microscopy - Sequence 8B
a
N]
Operation
Sample Preparation (Continued)
Cover the Petri dish and Allow to Stand
Approximately 3 Hours. Note: See
Reference diagram below
Remove Grid with Carbon Film From Bath
and Carbon Coat the Debris Side in the
Vacuum Evaporator.
Store on a Filter Paper in Another
Petri Dish. They are now Ready for
Electron Microscopy.
Location
Metallurgical Lab.
Metallurgical Lab.
Metallurgical Lab.
Responsibility
Technician
Technician
Technician
Remarks
The Nuclepore filter is
apparently dissolved by the
the chloroform by wick action
through the pores of the car-
bon replica.
Nuclepore filter
Debris
Carbon Replica
Copper Grid
- Cover
-Petri Dish
- Chloroform
Polyurethane
(2 of 3)
-------
t)
00
Table D-4 - Particulate Analysis by Electron Microscopy - Sequence 8B
Operation
Sample Counting
Fill Out Count Sheet
Calibrate the Microscope.
Place a Sample Grid in the Microscope
and Check Several Grid Openings to
Ensure that the Grid is Suitable for
Counting.
Set up EM at 22.000X for Fiber Identi-
fication by Morphology and Electron
Diffraction.
Count and Record Fibers for Each of 20
Fields in a 400 Mesh Specimen Grid.
Use a Hand Counter or Other Method to
Record the Number of Fields Counted.
Count all Fibers Crossing the Limits
of the Counting Field on Two Adjacent
Sides (Top and Left). Record the
Counts in the Various size Ranges
Given on the Count Sheet (Exhibit
D-I).
Electron and/or X-ray Diffraction
Check Crystallinity of Several Particles
and Fibers, and/or Fields.
Location
D-212
Metallurgical Lab.
Metallurgical Lab.
Metallurgical Lab.
Metallurgical Lab.
Metallurgical Lab.
Metallurgical Lab.
Responsibility
Project Engineer
Microscopist
Microscopist
Microscopist
Microscopist
Microscopist
Microscopist
Remarks
Binocular magnification at
10X can be used for greater
magnification.
A field is defined as an area
within the square etched on the
grid.
Record typical diffraction patterns.
(3 of 3)
-------
Table D-5 - Asbestos Emissions and Size Distribution - Sequence 9
Operation
Total the Number of Fibers in Each Size
Category
Calculate the Total Fiber Volume
Calculate the Total Fiber Weight.
Calculate the Total Fiber Concentration
Calculate and Plot the Asbestos Particle
Size Distribution
Location
D-212
D-212
D-212
D-212
D-212
Responsibility
Project Engineer
Project Engineer
Project Engineer
Project Engineer
Computer
Remarks
-------
Table D—6 - Noncondensable Gaseous Emissions Processing - Sequence 10A
V
K1
O
Operation
Fill Out Gas Analysis Sheet (Exhibit
D-II) .
Check Gas Storage Box.
Start Up Gas Chromatograph With Porapak
Column Installed.
Start Up Gas Processing Equipment
Connect Noncondensable Gas Trap to Gas
Inlet Tap With Vacuum Tubing. Pump
Out Tubing.
Place Dry Ice Trap Around Primary Inlet
Trap. Place Liquid Nitrogen Around
Secondary Inlet Trap.
Maintain Gas Storage Box at Dry Ice Tem-
perature. Open Taps and Allow Nonabsorbed
Gases to Escape From All 3 Traps.
Isolate Condensable Gas Trap.
Pump Out G.C. Sample U-Tube. Close High
Vacuum Tap to Isolate .Manifold. Remove
LN2 Trap.
Remove DI in Gas Storage Box and Raise to
Ambient.
Begin Collection of Adsorbed Noncondensable
Gases in Gas Burette With Toepler Pump.
Complete Gas Measurement. Select a Portion
for Analysis by G.C. Discard Remainder or
Store a Portion in an Empty Gas Storage
Volume.
Collect Additional Fractions Until All
Gases are Measured and Analyzed.
Location
D-212
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
.Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Responsibility
Project Engineer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Remarks
Record condition.
See conditions in Exhibit
D-III.
Insure good seal prior
to further processing.
To remove any possible
condensable.
To remove carrier air from
sample. Check vacuum return
periodically.
To be analyzed later
separately.
Top-up DI trap.
If amount appears to be
large, close valves and
isolate a portion.
Record quantities and G.C.
results Exhibit D-III
for each fraction.
Record as above.
-------
Table D-7 — Analysis of Noncondensable Gaseous Emissions - Sequence 10B
Operation
Location
Responsibility
Remarks
Insure G.C. Parameters are Properly Set for
Porapak Column.
Check Base-Line Stability of Thermal
Conductivity Detector.
Select a Portion of Gas Burette Sample
for G.C. Analysis.
Open Gas Burette 3-Way Tap and Push Gas
Sample Into Sample U-Tube. Raise Mercury
to Tap of Gas Burette.
Close 3-Way Tap."
Turn G.C. Recorder On. Adjust Chart Paper
to Record Injection Time. Record Sample
Identification on Chart.
Inject Sample. Record Injection Time and
Attenuation.
Monitor G.C. Analysis.
Lower Mercury Level in Gas Burette. Keep
Mercury Seat Valve Open.
Open High Vacuum Tap to Diffusion Pump.
Open 3-Way Tap to Pump Out G.C. Sample
U-Tube.
Monitor G.C. Retention Times, Peak Heights
and Attenuation Settings.
Check Gas Burette Vacuum. Close 3-Way Tap
to Isolate G.C. Sample U-Tube. Prepare a
Calibration Sample for G.C. From a Gas
Storage Bulb.
Inject Calibration Sample and Record as
Above.
(Run Infrared Analysis).
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
See Exhibit D-III
Attenuation XI.
Use 4.98 cc volume at 5 to
15 cm pressure.
Do not allow mercury into
bore of top.
After 10 sec., return top
to normal He flow positions.
Use magnet to hold open.
Caution: Monitor pen to
insure full record.
(Inject sample into gas
cell through sample
U-tube.)
-------
KJ
Table D-8 - Condensable Gaseous Emissions Processing - Sequence 11A
Operation
Location
Responsibility
Remarks
Insure Condensable Gas Trap is Under Vacuum.
Place Dry-Ice Around First Distillation
Trap and LN2 Around Second Trap.
Distill Contents of Condensable Gas Trap
Through Traps in Gas Handling System.
After Distillation, Allow LN2 Trap to
Ambient Temperature and Determine Amount
and Composition of Noncondensable Gases.
Replace Tubing at Gas Inlet With a
Specially Built, Weighed Glass Vessel.
Evacuate and Isolate the First Trap and
This Vessel. Heat Trap and Cool Vessel so
that a Vacuum Distillation Transfers Con-
densable Gases to Vessel.
When All Liquid is Transferred, Close
Stop-Cock and allow to come to Ambient
Weigh and Determine Weight of Condensable
Gases.
Analyze by Gas Chromatography.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Clean vessel with solvent
and regrease stop-cock.
-------
Table D-9 - Analysis of Condensable Gaseous Emissions - Sequence 11B
Operation
Insure G.C. Parameters are Properly Set
for Silicone Gum Column.
Check Base-Line Stability of Flame loni-
zation Detector.
Turn G.C. Recorder On. Adjust Chart Paper
to Record Injection Time. Record Sample
Identification On Chart.
Inject 1.0 ul Sample. Record Injection
Time and Attenuation.
Monitor G.C. Analysis.
Run Calibration Blend.
(Run Infrared Analysis.)
Location
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Analytical Lab.
Responsibility
Gas Chroma-tographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Gas Chromatographer
Remarks
See Exhibit D-III
Attenuation XI Range 10.
Monitor temperature
p ro gr amming .
Periodically.
(Periodically. Blank out
solvent plus calibration.)
Co
-------
Table D-10 - Total Gaseous Emissions - Sequence 12
Operation
Total the Number of Moles of Each Noncon-
densable Gas Produced.
Relate the Number of Moles of Condensable
Gases Formed to the Internal Calibration
and to the Calibration Blend.
Calculate the Carbon Content in Grams.
Total the Carbon Content.
Location
Laboratory
Laboratory
Laboratory
Laboratory
Responsibility
Project Engineer
Project Engineer
Project Engineer
Project Engineer
Remarks
Can be related to weight
lost x organic fraction x
carbon fraction.
-------
Exhibit D-I
MICROSCOPY COUNT SHEET
Vehicle Test:
Schedule:
Collector:
Sample:
Date:
Total Sample Weight:
LTA Weights (I/F):
Count Weight:
Comments:
o
o
o
o
o
sf
16
29
30
0.03
0.05
0.05
0.08
0.03
/
0.25
0.25
/
0.50
0.50,
1.0
3.0
EM Field Size:
3.0 x 3.0]]
No. of Fields:
FIBER LENGTH (u)
_mg
jng
mg
Date Counted:
OM Field Size:
No. of Fields:
Microscopist:
D-15
-------
Exhibit D-II - Gaseous Emissions Data
Sample: Sample Date:
Run No: Analyst:
Location: Analysis Date:
Box No:
Comments:
Noncondensable Emissions:
P =
V =
T =
n =
H2
N2
°2
CO
co2
C2H6
Condensable Emissions:
Sample Plus Tare:
Tare:
Sample:
D-16
-------
Exhibit D-III
INSTRUMENT SETTINGS:
Column:
Flow:
Temperature Program:
Detector Temperature:
ELUTION ORDER:
ANALYSIS OF NONCONDENSABLE
GASEOUS EMISSIONS
10' 1/8" O.D. Stainless Steel packed
80/100 mesh Porapak Q
40 cc/min He
-80°C to 160°C programmed at 10°C/min.
160°C (Dual Thermal Conductivity)
Hydrogen
Nitrogen
Oxygen
Carbon Monoxide
Methane
Carbon Dioxide
Ethane
Water
C3 to C^'s
ANALYSIS OF CONDENSABLE
GASEOUS EMISSIONS
6' 1/8" O.D. Stainless Steel packed
with 10% W-98 on 80/100 mesh
Chromosorb W
40 cc/min He
25°C to 260°C programmed at 6°C/min.
300°C (Dual Flame lonization)
C3 to 04*3
Benzene
Toluene
Xylenes
Phenols
Cresols
DM and TM Phenols
n-Ci6 solvent
n-C calibration
-------
APPENDIX E
ELECTRON MICROSCOPY ANALYSIS OF BRAKE EMISSION SAMPLES
E.I SUMMARY
The previously developed technique for preparing brake emission
debris for viewing with the electron microscope was found to be unsat-
isfactory for test car samples. That procedure was developed with
standards and employee vehicle wear debris. When applied to the test
vehicle brake emissions, excessive film breakage and instability occurred.
Consequently, the technique was modified so that it was reasonably sure
that no further difficulties would be encountered with the remaining
samples to be analyzed. Basically success was achieved with (1) use
of a finer copper grid, (2) double carbon film, and (3) reduced debris
loading on the film. The details of the procedure, as modified, are
given in Exhibit E-l.
E.2 PROBLEM
The difficulty with the previously developed procedure was
manifested by the following:
(1) Fracture of the carbon film occurred during the
cleaning operation employed to remove the filter.
The fracture was so severe that carbon film coverage
of the copper grid varied from 0 to 10% of the area
originally covered.
(2) The large wear debris particles were unstable under
the electron beam (expansion and contraction).
This particle movement tore the film and released
the wear debris so that analysis was impossible.
(3) The filter and carbon film appeared to shrink under
the action of the cleaning solvent. This raised
the question as to whether concentration of the wear
debris was occurring because of the shrinkage and in
this way creating a discrepancy between the real and
observed number of particles per unit area.
E.3 PROBABLE CAUSES
It was assumed that the first two difficulties were created by
the large nonasbestos wear debris particles. These particles appeared
larger than those previously found in wear debris samples from the
employee vehicle drum surfaces. The large particles apparently cause
film tears because they created thin spots or openings in the carbon
film during evaporation attributable to shadowing effects. These weak
E-l
-------
spots in the film and the bulk of the particles then contributed to
film tearing during the strains of the cleaning operation. The particle
instability under the electron beam could be attributed to heating and
charging effects. The third difficulty occurred because the filter
shrank under the action of the solvent before dissolving. Since the
carbon film and filter were initially attached, the filter stressed the
carbon film and also caused it to distort or crack.
E.4 SOLUTION ATTEMPTED
The following procedures or materials were tried in an attempt
to eliminate the film breakage problem.
(1) A range of film thicknesses was investigated from
thinner to thicker than that previously used.
(2) Silicon monoxide films were used in the hope that
they would provide additional strength.
(3) Different films and film combinations were tried.
These included chromium, platinum-carbon, chromium
on carbon and collodion on carbon.
(4) Extreme care was exercised in laying the film on
the grid prior to cleaning in order to ensure no
handling breakage.
(5) The time to clean the filter from the film was
shortened in an attempt to prevent breakage during
cleaning.
(6) The cleaning solution was diluted or saturated in
an attempt to reduce the severity of the cleaning
operation.
(7) Carbon film was cleaned both while on a rough and
on a smooth side of carbon grid.
(8) Vacuum drying of the film following cleaning was
tried to remove all traces of residual solvent in
case this was the cause of particle instability
under the beam.
(9) A finer mesh grid (400 instead of 200) was tried
to provide greater support for the carbon film.
(10) A second carbon film was vaporized over the wear
debris and onto the original film following the
cleaning operation. This sandwiched the wear debris
between two carbon films. It was hoped that the
additional film would provide additional strength
and reduce particle instability.
E-2
-------
E.5 SUCCESSFUL APPROACHES
Only the last three of the above mentioned techniques proved
significant in combating film breakage and instability: fine mesh grid,
double carbon film and lower debris loading on the film. The 400 mesh
grid apparently provided greater support for the film and did reduce
breakage during cleaning. The second carbon film applied after clean-
ing measurably strengthened the original film. Although there still
appeared to be some particle instability under the beam the double
film was strong enough to resist tearing.
The effect of the degree of loading on film integrity following
cleaning is shown in Figure E-l. The debris was an air-borne sample
taken from the right rear brake following the baseline test. All
samples were on a 400 mesh grid and received a double carbon film.
The debris loadings on the submitted filters were 1, 0.50, and 0.30 mg.
The last two show good film coverage while the 1 mg loading shows
extensive breakage. Also the 1 mg loading showed more stability under
the beam than did the other two. Therefore, even though the counting
time was increased because of the decreased loading, the filter loading
was reduced to less than 0.60 mg.
Another consideration in selecting the debris loading for the
film was the possibility that the large particles would mask the
asbestos fibers. Considering the extreme, if the debris were concen-
trated to the extent that particles covered the entire grid opening,
few fibers would be seen. The debris distribution for several initial
filter loadings is shown in Figure E-2.
The possibility of erroneous results due to film shrinkage with
attendant concentration of the debris was investigated. It did not seem
reasonable that debris concentration would occur because the debris was
attached to the carbon film and the carbon film itself would not shrink
under the action of the solvent. Since the periphery of the carbon
film was changing it was assumed that this could only occur by fracture
or distortion of the film. Optical microscopy confirmed the assumptions.
The film did not undergo shrinkage, but rather accomplished the dimen-
sional change by forming folds as shown in Figure E-3. These folds
were confined mainly to the periphery and would not pose any difficulty
to the measurement as long as the folded area was avoided. In other
films the folds were not confined entirely to the periphery, however,
these areas could easily be avoided during the counting as they were
readily detectable on viewing with the electron microscope. Therefore,
the film folding under the action of the solvent posed no serious diffi-
culties in the analysis.
E-3
-------
Figure E-l - Photomicrographs of Carbon Films on 400-Mesh Grid 50X
[Films were made from filters with original debris loading
of 0.3 (upper), 0.5 (center) and 1 (lower) mg. Debris was
airborne collection from A.B. Baseline schedule of vehicle
test for right rear drum brake]
E-4
-------
Figure E-2 - Electron Micrographs of Debris Distribution on Carbon
Films Made from Initial Filter Loadings of 0.3 (upper),
0.5 (center) and 1 (lower) mg. (Debris was airborne
collection from Baseline test) 6000X
E-5
-------
Oil*:
Figure E-3 - Photomicrograph of Carbon Film on 400-Mesh Grid Following
Cleaning -Operation. SOX (Shrinkage was due to film folds
near periphery of film. Film was made from filter with
0.5 mg debris loading.)
E.6 CONCLUSIONS
1. The modified technique for preparing electron microscopy
samples should provide a trouble-free method for analyzing
all samples required for the program.
2. Loading of the filter was limited to less than 0.6 mg.
This was required to prevent film breakage and, in addition,
there was less chance of the large particles masking the
asbestos fibers.
3. Film folding during cleaning did not introduce error into
the analysis.
E-6
-------
EXHIBIT E-I
PROCEDURE FOR ELECTRON MICROSCOPY ANALYSIS
OF BRAKE EMISSION SAMPLES
1. Receive and log in sample.
2. Cut out 1/2-inch filter circle with special cutter.
3. Mount filter circle (debris side up) on glass slide with tape.
4. Vacuum evaporate carbon film on filter circle (4 mm length of
carbon rod; 1 mm in diameter).
5. Remove from evaporator and cut out four 1/8-inch circles with
special cutter.
6. Prepare cleaning bath to remove filter from carbon film by the
following steps. Put polyurethane foam block in a petri dish
and fill with chloroform to about 1/8-inch below the foam surface.
Put 400 mesh copper grids on the top surface of the foam.
7. Place 1/8-inch carbon-coated circles on grids in the chloroform
bath with carbon side down.
8. Let sample clean in bath at least 3 hours. Bath is covered during
cleaning to prevent contamination.
9. Remove the carbon film on the grid from bath and carbon coat the
debris side in the vacuum evaporator.
10. Remove from evaporator and view in transmission electron microscope.
E-7
-------
APPENDIX F
COMPUTER PROGRAM FOR COMPUTATION OF
ASBESTOS CONTENT USING
ANALYTICAL MICROSCOPY TECHNIQUES
FORTRAN IV G LEVEL 70
MAIN
DATE 710?4
15/1=1/51
PAf.F 0001
0001
0002
0003
0004
0005
0006
0007
0008
0009
0010
0011
0012
0013
0014
0015
0016
0017
0018
0019
0020
°021
0022
C**** ************************ **************** ***********************»****,*,. ».,
C IN TWO DIMENSIONAL ARRAYS, IND^X I CORRESPONDS TO »OWS 11 14,
C 15*25, 16*26, 27 -31 ON MICROSCOPY COUNT SHFFT \Hn 1N1FX J
C CORRESPONDS Tn fOUI"NS 1 '8 ON MICROSCOPY COUNT SHFFT.
C* ******************************************************************************
DIMENSION BOX ( 49 I , VOL ( 1 2 , 8) , I VOL ( 12 , P I , FCTP ( 2 I , VPLT ( 49 )
1 , INM( 8I.XC1LI12.RI ,
1 IVH<5»,ISCH(20I,ICOL(20I,ISAMP(20I,IDATF(10I,TOT(2I
C**** ************ ******************************** *******************************
C ARRAY XOL CONTAINS VOLUME * 10**17.
C**** ***************************************************************************
DATA XOL/.077F-3, .2E-3, . 53E-3 , 9*0 .0,
2 .192E-3,.5E-3,l.31E-T,10.15E-3,fl*0.0,
3 .51E-3, 1. 34'r-3,3.?)f-3,27.1F-3,12?.?-3,.<)82,6*0.0,
4 1.66E-3,4.25E-3,11.3E-3,!)8.0E-3,401.E-3,:i.l9,12.fl,'<3.2,63.6,
4 3*0.0,
5 3.83E-3.10.E-3,26.3E-3,203.E-3,floo.E-3,7. 1, 29.» , 7f,. 7, 1 47. ,
5 241. .436. ,0. ,
6 7,77E-3,20.E-3,52.f'E-3,406.E-3, 17 80. E-3, 13. 5, 53. 8, 141. ,270.,
6 433.,805.,1.6PE3.
7 4*0. 0. 2960. F- 3, 23. 3. 9 3., 243., 466. , 765 . , 13RO. , 2 . 89E3 ,
8 4*0. 0,4 740. =-3,39.3,1 57., 40 9. ,794.,1290.,2.33E3,4.69E3/
C**** it*************************************************************************
C FCTRIll MULTIPLIES POWS 11-16. FCTRI2I MULTIPLIES ROWS 25-31.
C****** **#***#****#***#**#####***###*#**#*$$##*#*#****#***#*#*###?* #*##*********
DATA FCTR/110.E6..12784F6/
DO 190 1=1.12
PRINT 999.1 ,( XOL ( I. J) ,J=1 .81
999 FORMAT! I5.8E14.5)
190 CONTINUE
STEP=1. 0/6.0
C**** ******** *******************************************************************
C COMPUTE ARRAY BOX PO" LOG-LOG PLOT. BOX = 10**-!'. TO 10**-fl IN
C .STEPS OF 10**l/6.
C**** ***************************************************************************
DO 10 1=1,49
BOXU I = STEP*( 1-11-4.0-13.0
10 CONTINUE
C**** ***************************************************************************
C COMPUTE VOL(I.J) THE LOG OF XOLH.J) AND MULTIPLY XOL (I.JI BY
C 10**-12
C**** ***************************************************************************
DO 20 1=1,12
00 20 J=l.fl
IVOL(I,J)=0
VOL(I,J)=0.0
IF( XOL( I,J) .EO.O. IGO TP 20
VOL(I.J)=ALOG10(XOL(I.J) 1-12.0
XOL(I.J)=XOL( I ,JI*1.E-12
c**** ***************************************************************************
C COMPARE VOL(I.J) TO ARRAY BOX. ASSIGN NUMBER OF CLOSEST BOX TO
C IVOLd.JI.
c**** ***************************************************************************
00 30 K=l,49
IFIVOLI I.JI .LE.BOX(KI IGO TO 40
30 CONTINUE
K=49
40 IVOL(I.J)=K
F-l
-------
FORTRAN IV C, LEVEL 20
MAIN
OATF = -73024
15/19/51
PAGE 0002
002*
0025
0026
0027
0028
0029
0030
0031
0032
0033
0034
0035
0036
0037
0038
0039
0040
0041
0042
0043
0044
0045
0046
0047
0048
0049
0050
0051
0052
0053
0054
0055
0056
0057
0058
0059
0060
0061
0062
0063
0064
0065
0066
20 CONTINUE
DO 50 1=1.49
BOXU )=10.0**BOX1 I I
50 CONTINUE
00 191 1=1,12
PRINT 999,1 ,( VOLd.JI ,J=1.8)
191 CONTINUF
C
C START DOING STUFF
C
C**** ***************************************************************************
C READ HEADING CARD.
C*******************************************************************************
100 READ (5,900,END=500> 101.(IVH(I I,1=1,5),(ISCH(J),J=1.20).
1 (ICOL(KI,K=l,20t,(ISAMP(L).L=1.20>,(I HATE(M),M=1,101
900 FORMATII4.1X.75A1)
READ (5,9011 ID.TOTWT.XI,XF,XCNT
901 FORMAT!I4.6X.4E10.0)
IF( ID.NE.IDDGO TO 501
TOTWT=TOTWT*.001
XI=XI*.001
XF=XF*.001
XCNT=XCNT*.OOl
DO 200 1=1,49
VPLTII 1=0.0
200 CONTINUE
C*******************************************************************************
C TOT(l) SUM OF ROWS 11-16. TOTI2I = SUM OF ROWS 25-31.
c*******************************************************************************
TOT(1)«0.0
TOT(2>=0.0
TOTAL=0.0
110 READ (5,920) ID,I.J.(INM(K),K=l,8),ITOT
IF(ID.NE.I011GO TO 501
920 FORMAT!14,211.4X,BI3,6X,15)
IF(I.EQ.2IJ=J+l
IF(I.E0.3)J=J+11
IFd.EO. 3)1=2
DO 120 K=1.8
TOT(I) = TOTdl+2.56*XOLtJ,KI*lNM(KI*FCTR(I)/I TOT
IF(IVOL(J,K).EO.O)GO TO 120
VPLT( IVOLI J,K)) = VPLT(IVOL(J.KI) + INM(K)*FCTR(I l/ITflT
120 CONTINUF
C*******************************************************************************
C TEST FOR LAST DATA CARD.
C*******************************************************************************
IFd.EO.2.AND.J.E0.12IGO TO 130
on TO no
130 CONTINUE
TOTAL=TOT!l)+TOT<2)
PCT=TOTAL*XF*100.0/(XCNT*XII
PRINT 911
911 FORMAT!'I1,45X,'**** ASBESTOS ANALYTICAL RESULTS ****•)
PRINT 912.TOT!1 I,TOT(2)
912 FORMAT! '0',105X,'FM SUB TOTAL = •,El 1.4,/105X,•OM SUB TOTAL =•,
1 Ell.4)
PRINT 910,(IVH! I I,1 = 1,5),(I DATE(J),J-1,10),X I.TOTAL,
1 (ISCH(K),K=1,20I,I01,XF,XCNT.
F-2
-------
FORTRAN IV G LEVFL 20
MAIN
DATE = 73024
15/19/51
PAGE 0003
0067
0068
0069
0070
0071
0072
0073
0074
1 (ICOL(L),L=1,20) i
1 ,M=1,20>,PCT
910 FORMAT('OVEHICLE TEST: • , 5A1, 30X, 'D ATE : • , 10A 1, 13X, ' LTA ( I ) = • . f I 1.4
1.16X,'TOTAL =',E11.4,/ 5X,'SCHEDULE: •.ZOAlilSX.1 NO.: '.I5.18X,
2'LTAtF)=',E11.4, 9X,'COUNT WEIGHT =',E11.4,/' ',3X,'COLLECTOR: ',
320A1,/' ',6X,'SAMPLE: ',20A1,SOX,'ASBESTOS PERCENT =•,F7.3,•*',/>
CALL LGPLT(BOX,VPLT,49)
GO TO 100
500 STOP 1
950 FORMAT!'1 CARDS OUT OF ORDER ON RUN NO.',15)
501 PRINT 950,101
STOP 999
END
FORTRAN IV G LFV^L 20
MAIN
= 73024
15/19/51
PAGE 0004
SUBPROGRAMS CALLED
SYMBOL LOCATION SYMBOL LOCATION SYMBOL LOCATION SYMBOL LOCATION
IBCOM* 14C FRXPR* 150 LGPLT 154 ALOG10 158
SYMBOL
LOCATION
SCALAR MAP
SYMBOL LOCATION SYMBOL LOCATION
I 174 J 178
L 188 M 18C
XF 19C XCNT 1AO
SYMBOL LOCATION SYMBOL LOCATION SYMBOL LOCATION
STPP 17C K 180 101 184
ID 190 TOTWT 194 XI 198
TOTAL 1A4 ITOT 1A8 PCT 1AC
SYMBOL LOCATION
BOX 1BO
[NM 640
I SAMP 894
ARRAY MAP
SYMBOL LOCATION SYMBOL LOCATION SYMROL LOCATION SYMBOL LOCATION
VOL 274 IVOL 3F4 FCTR 574 VPLT 57C
XOL 660 IVH 7EO ISCH 7F4 ICOL 844
IOATE HF4 TOT 90C
FORMAT STATEMENT MAP
SYMBOL LOCATION SYMBOL LOCATION SYMBOL LOCATION
999 914 900 91D 901 927
912 972 910 9A2 950 A6D
SYMBOL
920
LOCATION
932
SYMBOL
911
LOCATION
944
to
*OPTIONS IN EFFECT* ID,EBCD1C.SOURCE,NOLIST.DECK.NOLOAD,MAP
*OPTIONS IN EFFECT* NAME = MAIN , LINECNT = 60
*STATISTICS* SOURCE STATEMENTS = 74,PROGRAM SIZE =
*STATISTICS* NO DIAGNOSTICS GENERATED
-------
APPENDIX G
VEHICLE TEST DATA REPORTS
Because of the large number of test reports for different phases
of the vehicle tests and subsequent collection of brake emissions, the
individual data sheets were assembled into a separate volume for each
vehicle test. The original test data sheets were retained by the
Principal Investigator at Bendix Research Laboratories.
The volume for each vehicle test contains seven major sections,
one for each test schedule; and each section is broken down further
into three secondary sections for the vehicle operation results, the
brake emissions data sheets, and the,analytical results:
Vehicle operation data reports:
• Figure G-l is the Vehicle Log Sheet which remained in the
vehicle to record the overall vehicle operation throughout
the test schedule.
• Figure G-2 is the Burnish report.
• Figure G-3 is the Detroit Traffic data sheet used during the
Baseline and Detroit Traffic schedules.
• Figure G-4 is the 10-Stop Fade data sheet.
• Figure G-5 is the 15-Stop Fade data sheet.
• Figure G-6 is the Recovery data sheet used in conjunction with
the 10- and 15-Stop Fade data sheets during the Fade schedules.
• Figure G-7 is the Reburnish data sheet used in the 10- and
15-Stop Fade schedules.
Brake Emissions data sheets:
• Figures G-8 and G-9 are the Wear Sheet-Front Axle and Wear
Sheet-Rear Axle used to record both weight and thickness losses
of all friction materials on the vehicle.
• Figures G-10 and G-ll are the Collection of Brake Emissions
(Right Side) and Collection of Brake Emissions (Left/Control
Side) which were used to record and calculate the brake wear
debris collected in the sump, on the surfaces, and the airborne
samples.
• Figure G-12 is the Test Summary Sheet used to summarize the
wear data and to check out the material balances.
G-l
-------
Analytical Results:
• Figure 8-13 is the Microscopy Count Sheet onto which each fiber
found by microscopy was classified according to its dimensions.
• Figure 8-16 is the Computer Printout which gave the asbestos
percent and the size distribution.
• Figure G-13 is the Asbestos Emission Summary Sheet used to
summarize each test schedule.
-------
\/£tfiCLE LOG,
7e.st A/o.
Dates: Start:
Test Sefft/ent
DfiT£
TttTALS
4MB.
CF)
?e:
M,™
ODOfn&TER
START
F/HNISH
Tom.
STOPS
flfPL.
COMMTC
Fini&h :
COMMENTS
Figure G-l - Vehicle Log Sheet
-------
Test No.,
Burnish (Brake Performance Test Weight);
Odometer Date
Temp,
200 Stops, 40 MPH, 12 FPSPS in Highest Gear, 250° IBT or 1 Mile Maximum -
40 MPH Cooling Speed, 80% Burnish
Stop
1
20
40
60
80
100
120
140
160
180
200
Initial Temperatures °F
L.F.
R.F.
L.R.
R.R.
Max.
L.P. psi
Max.
P.F. Ib.
P.T.
in.
Comments
Comments
Figure G-2 - Burnish Report
G-4
-------
DETROIT CITY TRAFFIC TEST
START ODOM.
CAR NO.
START **
MICH. & 3RD. **
ADAMS & WOOD.
ADAMS & WOOD.
12 MILE **
ADAMS & WOOD.
ADAMS & WOOD.
ADAMS & WOOD.
12 MILE **
ADAMS & WOOD.
ADAMS & WOOD.
ADAMS & WOOD.
12 MILE **
ADAMS & WOOD.
ADAMS & WOOD.
ADAMS & WOOD.
12 MILE **
ADAMS & WOOD.
ADAMS & WOOD.
ADAMS & WOOD.
12 MILE **
ADAMS & WOOD.
ADAMS & WOOD.
END **
END ODOM.
TIME
AMB.
L.F.
TEST NO
R.F.
L.R.
•
R.R.
DATE
COMMENTS
Figure G-3 - Detroit Traffic Data Sheet
G-5
-------
Test No..
First Baseline: (Brake Performance Test Weight)
Odometer Date _
.Temp..
3 Stops, 30 MPH, 10 FPSPS in Highest Gear, 140°-150° IBT Each Stop
Stop
1
2
3
Initial Temperatures °F
L.F.
R.F.
L.R.
R.R.
L.P.*PSI
Init.
Sust.
Fin.
Max.
P.F.
Ib.
P.T.
in.
Comments
First Fade: Odometer .
.Date.
.Temp.
. Wind .
10 Stops, 60 MPH, 15 FPSPS in Highest Gear, 0.4 Mile Interval, 140°-150° IBT For Stop I
Req't.: 200# Maximum P.E. First Four Stops
Stop
1
2
3
4
5
6
7
8
9
10
Initial Temperatures °F**
L.F.
R.F.
L.R.
R.R.
L.P.*PSI
Init.
Sust.
Fin.
P.F. Ib.
Init.
Sust.
Fin.
P.T.
in.
Comments
Total Elapsed Time .
.Sec.
Must include maximum line pressure.
*
On cooling cycle.
Figure G-4 - 10-Stop Fade Data Sheet
G-6
-------
Test No..
First Baseline: (Brake Performance Test Weight)
Odometer Date
. Temp..
3 Stops, 30 MPH, 10 FPSPS in Gear, 140°-150° IBT Each Stop
Stop
1
2
3
Initial Temperatures °F
L.F.
R.F.
L.R.
R.R.
L.P.*PSI
Inlt.
Sust.
Fin.
Max.
P.F.
Ib.
P.T.
in.
Comments
First Fade: Odometer.
.Date.
_Temp..
.Wind.
15 Stops, 60 MPH, 15 FPSPS in Gear, 0.4 Mile Interval, 140°-150° IBT For First Stop
Req't.: 200# Maximum P.E. For First Eight Stops
Stop
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Initial Temperatures °F
L.F.
R.F.
L.R.
R.R.
L.P.*PSI
Init.
Sust.
Fin.
P.F. Ib
Init.
Sust.
Fin.
P.T.
in.
Comments
Total Elapsed Time Sec.
*
Must include maximum line pressure.
Figure G-5 - 15-Stop Fade Data Sheet
G-7
-------
Test No..
Recovery - One Mile After Last Fade Stop, at 40 MPH Cooling Speed
12 Stops, 30 MPH, 10 FPSPS in Highest Gear, or Max. Decel.
for 200 Ib. PF if 10 FPSPS Cannot Be Obtained, One Mile Interval
Req't.: 5 FPSPS Minimum for 2009 P.E. for First 5 Stops,
150# Maximum P.E. for Stop #6
Stop
1
2
3
4
5
6
7
8
9
10
11
12
Initial Temperatures °F
L.F.
R.F.
L.R.
R.R.
L.P.*PSI
Init.
Sust.
Fin.
P.F. Ib.
Init.
Sust.
Fin.
P.T.
in.
Comments
Driver .
. Observer.
(1) If warning light is activated, which M'cyl. piston bottomed out? Front D Rear D
(2) Center differential valve piston.
(3) Check front/rear pressure differential:
Front line pressure PSI ^
Rear line pressure PSI f Read simultaneously at approx. 1000 PSI
Figure G-6 - Recovery Data Sheet
G-8
-------
Reburnish (Brake Performance Test Weight);
Odometer Date
,Temp..
35 Stops, 40 MPH, 12 FPSPS, 250° IBT of One Mile Maximum in Gear
Stop
1
10
20
25
35
Initial -Temperatures °F
L.F.
R.F.
L.R.
R.R.
Max.
L,P. psi
Max.
P.F, Ib.
P.T.
in.
Comments
Figure G-7 - Reburnish Data Sheet
G-9
-------
Vehicle Test No.
Test Sequence:_
WEAR SHEET.
.AXLE
MAKE OF CAR:
LINING:
.MODEL:.
COMMENTS:.
PTHHT
Date
Mileage
RTCTIT
Date
Mileage
T.F.FT
Date
Mileage
T.KT7T
Date
Mileage
Total
Stops
1
2
3
4
5
6
Weight Loss
Total
Stops
1
2
3
4
5
6
7
Weight Loss
Total
Stops
1
2
3
4
5
6
Weight Loss
Total
Stops
1
2
3
4
5
6
7
Weight Loss
. Figure G-8 - Wear Sheet - Front Axle
G-10
-------
Vehicle Test No..
Test Sequence:—
WEAR SHEET.
.AXLE
MAKE OF CAR:,
LINING:
.MODEL:
COMMENTS:.
Uir.WT BRAI
Date
Mileage
HTRHT RRA1
Date
Mileage
T.F.TT RRA1
Date
Mileage
LKFT RRAJ
Date
Mileage
CE (PRI. OR FORWARD)
Total
Stops
1
2
3
4
5
6
Weight Loss
CE (SEC. OR REVERSE)
Total
Stops
1
2
3
4
5
6
7
8
Weight Loss
CE (PRI. OR FORWARD)
Total
Stops
1
2
3
4
5
6
Weight Loss
CE (SEC. OR REVERSE)
Total
Stops
1
2
3
4
5
6
7
8
Weight Loss
Figure G-9 - Wear Sheet - Rear Axle
G-ll
-------
OF
Test S&fu&>ee:
TestVat&s
Finish :
FRONT BtflKE
•SuMP SAMPLE'. S,lter*4e.tirir.
• Cafifer fl'cttn /,#«t:
-frVtttlil**
StfRFflCBS Sfi0Pl£ •• Sitter iJetns:
tirtor -filter:
debris
^^^alohf-0*.
tgtal tn OZu.
1,131 m-filters:
%m
TOTAL S/)ffif/.e:
! > SUMP:
\ i > SURFACES:
r >
COMMEMTS:
RIGHT
0/eAKE
6i/Mp SAMPLE:
•]tletf-7raeK
•dfv'ft //«/«s
>r»Kg. P*t->
2 fitters;_
-t.i«l:
-86%falui-n:_
2.0%/Sdtnifj;
filter:
SAMPLE:
•fitter + debris:
-Pilier;
TtiaL on S.o/n:
fob/on M«:
•iiiaL on •
Cwrtded Suuf Samfle
Previtus test • _
r _„„.
i
|«n j TOTAL
L-
r"
i =
Sump:
->• SuRFRces:
CoMMEttre:
r
Figure G-10 - Collection of Brake Emissions (Right Side)
G-12
-------
Emission
Vehicle
Jest Saau.enc.e:
i£Fr
SUMP SAMPLE: filter+ctabris:
•Caliper fist'* -filter.
SAMPLE:' /i Her 4 debris:
TOTAL SAMPLE:
i *• Sump
--> St/erflces:
LEFT DRUM BRRKE
'SAMPLE' -fik
•foot Ab/ss
2.0%r*tun:
•:-filter debris;
•Drum
COMMENTS:
CorreeleJ Sutup Sample
i
i i < >
i i
i i
r
foTfiL.
i ------ > SUMP •
r
CL u TCH
•ttdat. an o.l'-
filters.
Figure G-ll - Collection of Brake Emissions (Left Side)
G-13
-------
TEST
\Je,hicl&
Stops'
Tf si Dates : Start;
F/his A
FROHT 2>/sc BtfflfeS •
Temperature fonfte f°f) '
S0inples Col teemed (artfij '
Sump •
Surfaces:
fl Id Is owe '•
ToTaL •
L'hinq UJear- \ */o
° TotaL
ffecovert °/o]
/?EAfi BUM BRAKES'
Tern fie ntvre K^nae (°p}
Samples Coll&c.'f'e.J (^ms-):
S i/i- fa ties :
Airborne:
TohL-
Lihin* Wear: P/<$
Toial
(.RetoverVfi
CLUTCH-.
Sample C°l/e
-------
St/MMflW SttEST.
Vehicle, Test No..
Test Schedule :
: Debris data are repotted as
Debris Qenera+ed per- step)
FIGHT
CLUTCH
U
LEFT
D&bns:
Asbestos:
Debris :
Debris :
flsbestos;
[\U
Pl&UT
SUMP :
Debt-is :
ft s best**'.
SURFACES;
Asbestos:
flsbestor:
Figure G-13 - Asbestos Emissions Summary Sheet
G-15
-------
APPENDIX H
ASBESTOS EMISSIONS ANALYSIS REPORTS
FROM BATTELLE COLUMBUS LABORATORIES AND
JOHNS-MANVILLE RESEARCH AND ENGINEERING CENTER
The following information has been excerpted from the final summary
report "Asbestos Emissions Analysis" by Battelle Columbus Laboratories
(C. W. Melton and W. M. Henry) to the Environmental Protection Agency
(Contract No. 68-01-0416). Dr. Joseph H. Somers was the Project Techni-
cal Officer who supplied this information to Bendix Research Laboratories.
The objective of the project was to analyze 24 clutch and brake
lining emissions for asbestos content. The samples were generated, col-
lected, and submitted for analysis by the Bendix Research Laboratories.
The analytical method used for asbestos in brake and clutch lining
emissions was a modification of one developed for the analysis of asbes-
tos in collections of airborne particulate. In general, results indica-
ted that sump samples contained, by far, more asbestos than airborne or
surface samples.
Experimental Procedure and Calculations;
The analytical procedure employed was as follows:
(1) An aliquot of the brake or clutch debris was weighed.
(2) The aliquot was put into a centrifuge tube and was low-temperature
ashed for three days.
(3) The ash residue was suspended in 10 ml of an aqueous solution to
which 3 drops of 1.0 percent Aerosol OT was added and then was
treated ultrasonically to separate the asbestos fibers into colloi-
dal fibrils.
(4) The extraneous material was separated by centrifugation from the
asbestos which remained in colloidal suspension in the supernatant
liquid.
(5) The supernatant liquid was filtered through a Millipore filter
(HAWP 025, HA 0.45 y, 25 mm) to deposit the asbestos fibrils uni-
formly over the surface of the filter.
(6) A carbon film was vapor-deposited over the asbestos fibrils on
the filter and a 3-mm x 3-mm square was cut from the resulting
carbon-coated specimen.
(7) The filter was dissolved in acetone to leave the carbon film bear-
ing the asbestos fibrils.
(8) The carbon film was picked up on a 200-mesh electron microscope
specimen support grid.
H-l
-------
(9) The support grid and carbon film were loaded into the transmis-
sion electron microscope and the fibrils within several (usually
ten) grid openings were counted and the results recorded as num-
ber of fibrils per grid opening.
(10) The number of fibrils per grid opening was translated into micro-
grams of asbestos in the aliquot taken by using a standard curve
which was generated from known standard samples.
(11) Percentage asbestos in the sample was calculated by dividing the
weight of the detected asbestos by the weight of the aliquot.
H-2
-------
Experimental Results
Results of the analyses of the 24 samples submitted by Bendix are
as follows:
BATTELLE
SAMPLE NO.
29897-1-1
29897-1-2
29897-1-3
29897-1-4
29897-1-5
29897-1-6
29897-8-1
29897-8-2
BENDIX SAMPLE DESCRIPTION
Vehicle Test 1
Detroit Traffic Schedule
Right Front Brake
Airborne Sample
Vehicle Test 1
Detroit Traffic Schedule
Right Rear Brake
Airborne Sample
Vehicle Test 1
Detroit Traffic Schedule
Right Front Brake
Sump Sample
Vehicle Test 1
Detroit Traffic Schedule
Clutch
Airborne Sample
Vehicle Test 1
Detroit Traffic Schedule
Right Rear Brake
Surfaces Sample
Vehicle Test 1
Detroit Traffic Schedule
Right Rear Brake
Sump Sample
Vehicle Test 1
10-Stop Fade
Right Front Brake
Airborne Sample
Vehicle Test 1
10-Stop Fade
Right Front Brake
Sump Sample
PERCENT ASBESTOS
IN SAMPLE
0.00055
0.00057
0.207
0.0068
0.0061
0.025
0.031
1.22
H-3
-------
BATTELLE
SAMPLE NO.
29897-8-3
29897-8-4
29897-8-5
29897-8-6
29897-8-7
29897-8-8
29897-14-1
29897-14-2
29897-14-3
BENDIX SAMPLE DESCRIPTION
Vehicle Test 1
10-Stop Fade
Right Rear Brake
Airborne Sample
Vehicle Test 1
10-Stop Fade
Right Rear Brake
Sump Sample
Vehicle Test 2
Burnish Schedule
Right Front Brake
Sump Sample
Vehicle Test 2
Burnish Schedule
Right Rear Brake
Sump Sample
Vehicle Test 2
Burnish Schedule
Right Front Brake
Airborne Sample
Vehicle Test 2
Burnish Schedule
Right Rear Brake
Surfaces Sample
Vehicle Test 1
Detroit Traffic Schedule
Right Front Brake
Surfaces Sample
Vehicle Test 2
Detroit Traffic Schedule
Right Front Brake
Airborne Sample
Vehicle Test 2
Detroit Traffic Schedule
Right Front Brake
Sump Sample
PERCENT ASBESTOS
IN SAMPLE
0.0074
0.216
0.275
0.103
0.100
0.376
0.011
0.0057
0.62
H-4
-------
BATTELLE
SAMPLE NO.
29897-14-4
29897-14-5
29897-14-6
29897-14-7
29897-14-8
29897-14-9
29897-14-10
BENDIX SAMPLE DESCRIPTION
Vehicle Test 2
Detroit Traffic Schedule
Right Rear Brake
Airborne Sample
Vfehicle Test 2
Detroit Traffic Schedule
Right Rear Brake
Sump Surface
Vehicle Test 2
Detroit Traffic Schedule
Right Rear Brake
Surfaces Sample
Vehicle Test 3
Detroit Traffic Schedule
Right Front Brake
Airborne Sample
Vehicle Test 3
Detroit Traffic Schedule
Right Front Brake
Sump Sample
Vehicle Test 3
Detroit Traffic Schedule
Right Rear Brake
Airborne Sample
Vehicle Test 3
Detroit Traffic Schedule
Right Rear Brake
Sump Sample
PERCENT ASBESTOS
IN SAMPLE
0.015
0.057
0.061
0.016
0.135
0.044
0.0104
H-5
-------
jonns-Manvine
Research & Engineering Center
P. O. Box 159
Manville, N. J. 08835
(201) 722-9000
September 6, 1972
Dr. M. G. Jacko
Materials and Processes Department
Bendix Research Laboratories
Southfield, MI 48075
Dear Dr. Jacko:
We have finally completed the analysis of the brake lining
wear debris you sent to us. These samples were described
as follows in your letter to Dr. Speil of July 5, 1972.
Sample No. 1 - Vehicle Test 1
J-M No. 4123-58-1 Detroit Traffic Schedule
Right Front Brake
Surfaces Sample
Sample No. 2 - Vehicle Test 1
J-M No. 4123-58-2 Detroit Traffic Schedule
Right Rear Brake
Surfaces Sample
Sample No. 3 - Vehicle Test 1
J-M No. 4123-58-3 Detroit Traffic Schedule
Right Rear Brake
Airborne Sample
The fiber- content of the samples and the weight loss on
ignition are given below. The fiber content was determined
by the rub-out procedure which I believe we explained to you
at the time of your visit to our laboratory.
Mo. 1- No. 2 No. 3
Initial Sample Weight (mg) 50.78 46.50 45.70
Weight of Ash After Ignition @ 400C(mg) 43.50 31.10 30.20
Weight Loss on Ignition 14.4% 33.1% 33.9%
Total Fiber in Sample (micrograms) 2.54 0.98 2.73
Percent Fiber in Original Sample 0.005 0.002 0.006
We were unable to determine the element distribution because
our emission spectrograph has been disassembled for our move
to Denver.
H-6
-------
Dr. M. G. Jacko
September 6, 1972
Page 2
If you have any questions regarding these samples or pro-
cedures you can contact Dr. Speil. He will be available
through the month of September. After that time you can
contact me in Denver. Our mailing address and telephone
number in Denver will be:
Johns-Manville Corporation
P. O. Box 5108
Denver, Colorado 80217
Phone: (303) 770-1000
Very truly yours,
'/
J. P. Leineweber
mp
cc: Dr. S. Speil
H-7
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