United States
Environmental Protection
Agency
Office of Air Quality
Ranning and Standards
Research Triangle Park, NC
EPA 340/1-92-01 5b
September 1992
Revised March 1993
Stationary Source Compliance Training Series
fVEPA COURSE #345
EMISSION CAPTURE AND
GAS HANDLING SYSTEM
INSPECTION
Instructor Manual
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EPA 340/1-92-01 5b
Revised March 1993
Course Module #345
Emission Capture And
Gas Handling System Inspection
Instructor Manual
Prepared by:
Crowder Environmental Associates, Inc.
2905 Province Place
Piano, TX 75075
and
Entrophy Environmentalist, Inc.
PO Box 12291
Research Triangle Park, NC 27709
Contract No. 68-02-4462
Work Assignment No. 174
EPA Work Assignment Manager: Kirk Foster
EPA Project Officer: Aaron Martin
US. ENVIRONMENTAL PROTECTION AGENCY
Stationary Source Compliance Division
Office of Air Quality Planning and Standards
Washington, DC 20460
September 1992
Revised March 1993
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DISCLAIMER
This manual was prepared by Crowder Environmental Associates,
Inc. and Entropy Environmentalists, Inc. for the Stationary Source
Compliance Division of the U.S. Environmental Protection Agency.
It has been completed in accordance with EPA Contract Number 68-02-
4462, Work Assignment No. 174. The contents of this report are
reproduced herein as received from the authors. The opinions,
findings, and conclusions expressed are those of the authors and
not necessarily those of the U.S. Environmental Protection Agency.
Any mention of product names does not constitute endorsement by the
U.S. Environmental Protection Agency.
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ACKNOWLEDGEMENTS
This manual is a revised version of a manual originally
prepared by Crowder Environmental Associates, Inc. for the U.S.
EPA, Stationary Source Compliance Division (SSCD). It was
originally prepared under a subcontract to PEI Associates, Inc.
Entropy Environmentalists, Inc. has converted the manual into a
standardized format developed by the EPA Work Assignment Manager,
Mr. Kirk Foster. The majority of the drawings and photographs
included in the original manual have been redrawn and modified by
Ms. Sherry Peeler, Pendragon Inc. with the assistance of Entropy
Environmentalists, Inc.
nr Pf ENRV Library
U.S. EPA Region VII
11
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TABLE OF CONTENTS
Topic Page
Introductory Material
Course Description 0-1
Course Goals 0-2
Responsibilities of Course Director 0-3
Instructors 0-5
Physical Settings and Equipment 0-5
Lesson Plans 0-6
Testing Information 0-6
Grading Philosophy 0-7
Sample Agenda 0-8
Pre-test 0-10
Pre-test key 0-15
Post-test 0-16
Post-test key 0-21
Lesson l. General Principles of Ventilation
Goal 1-1
Objectives 1-1
List of Slides 1-2
Lesson Outline 1-3
Problem Set 1 1-10
Lesson 2. Hood Systems
Goal 2-1
Objectives 2-1
List of Slides 2-2
Lesson Outline 2-3
Problem Set 2 2-11
Lesson 3. Duct Systems
Goal 3-1
Objectives 3-1
List of Slides 3-2
Lesson Outline 3-3
Problem Set 3 3-12
IV
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Lesson 4. Gas Cooling Systems
Goal 4-1
Objectives 4-1
List of Slides 4~2
Lesson Outline 4-3
Problem Set 4 4-11
Lesson 5. Fan Systems
Goal 5-1
Objectives 5-1
List of Slides 5-2
Lesson Outline 5-3
Problem Set 5 5-18
Lesson 6. Measurement of Ventilation System Parameters
Goal 6-1
Objectives 6-1
List of Slides 6-2
Lesson Outline 6-3
Problem Set 6 6-18
Lesson 7. Ventilation System Inspection
Goal 7-1
Objectives 7-1
List of Slides 7-2
Lesson Outline 7-3
Problem Set 7 7-7
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INTRODUCTORY MATERIAL
This guide will provide you, as Course Director, with
assistance in the preparation and presentation of the course,
"Inspection of Industrial Ventilation Systems." It will provide
you with guidelines, instructions and general information that
should make it easier to conduct this course.
COURSE DESCRIPTION
This training course is a four-day lecture course dealing with
the inspection of industrial ventilation systems. In is not a
course in the design of ventilation systems. Although much of the
information presented comes from the design literature, many of the
topics needed to design systems have not been included. That
information that is utilized is oriented to focus on inspection
applications, rather than on design applications.
The course is organized into several lessons, with each lesson
having a problem set that allows the student to apply the skills
taught. The lesson topics are as follows:
1. General Principles of Ventilation
2. Hood Systems
3. Duct Systems
4. Gas cooling Systems
5. Fan Systems
6. Measurement of Ventilation System Parameters
7. Ventilation System Inspection
This course should be taught at an instructional level
equivalent to that of undergraduate university study. Students
should have a college education at the associated or bachelor level
in science or engineering and should have completed APTI Course
445, "Baseline Source Inspection Techniques", and Course 446,
"Inspection Procedures and Safety."
Course 345 0-1 Introductory Material
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COURSE GOALS
The overall goal of this course is to provide students with
the training and information necessary to conduct effective Level
2 and Level 3 inspections of industrial ventilation systems. The
specific goals are:
1. To develop an understanding of the basic information that
affects the character and behavior of air streams.
2. To develop an understanding of the different hood types,
their design and performance characteristics, and
techniques for their evaluation.
3. To develop an understanding of duct systems, their
design and performance characteristics, and
techniques for their evaluation.
4. To develop an understanding of gas cooling systems,
their design and performance characteristics, and
techniques for their evaluation.
5. To develop an understanding of fan systems, their
design and performance characteristics, and
techniques for their evaluation.
6. To develop an understanding of the equipment and
procedures for the measurement of ventilation system
parameters and the limitations of the techniques.
RESPONSIBILITIES OF THE COURSE DIRECTOR
This course requires four days for a complete presentation.
In addition, the Course Director can expect to spend 10 and 20
hours preparing for course. Pre-course preparation and course
continuity are the principal responsibilities of the Course
Director, and the Course Director will coordinate all on-site
activities both before and during the course presentation. The
actual tasks that are considered the direct responsibility of the
Course Director are as follows:
1. Scheduling the course presentation.
2. Recruiting, hiring, and briefing the instructors
3. Preparing the classroom and other teaching facilities
4. Preparing and distributing course materials to instructors
and students.
5. Presenting the introductory lecture and other lectures,
as appropriate
Course 345 0-2 Introductory Material
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6. Maintaining the continuity and coordination throughout
the course.
The following checklist is provided as an organization aid for
the Course Directors.
Pre-Course Responsibilities
Reserve and confirm classroom. Consider size, set-up
arrangement, and costs.
Contact and confirm all faculty for the course and
determine their A/V requirements. Send instructional
materials to them. One or more pre-course meetings are
advisable to order to ensure coordination and continuity
of presentations.
Reserve hotel accommodations for faculty (if necessary).
Make and confirm arrangements for coffee breaks
If any eating facilities are likely to be heavily used by
students, inform them of anticipated patronage and
anticipated lunch break times.
Make and confirm arrangements for transportation of
students (if necessary).
Assemble and send to students information on exact
location and times of course and information on
available lodging, eating, and transportation
facilities. Reserve a block of rooms for students
if appropriate.
Prepare and reproduce final copies of the course agenda.
Reproduce class roster, if available
Identify, order, and confirm all audiovisual equipment.
Prepare course identification signs for posting at meeting
area.
Arrange for and confirm any special on-site administrative
assistance needs.
Obtain copies of manuals and hand-outs.
Pack and ship course materials one week before course
begins.
Course 345 0-3 Introductory Material
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On-Site Course Responsibilities
Check on final room arrangements (i.e., tables, chairs,
lectern, water, cups)
Each day, set up audiovisual equipment and brief the
operator.
Post signs where needed.
Give receptionist, phone operator, and guards the names,
location, and agenda of the course and names of the
attendees.
Conduct a briefing session for each new instructor.
Verify and make final coffee arrangements.
Identify and arrange for other physical needs as
required.
Make a final check on arrival of instructors for the day.
Post-Course Responsibilities
Return the following to EPA (if an EPA course):
Unused course materials
Student registration forms
Pre-test answer sheets - graded
Post-test answer sheets - graded
Student course critiques
Instructor course critiques
Prepare Course Director's Report
Request honorarium and expense statements from faculty;
order and process checks.
Write thank-you letters to non-paid speakers- and to
others who may have contributed to the success of the
course.
Make sure audiovisual equipment is returned.
Course 345 0-4 introductory Material
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INSTRUCTORS
The five most important criteria in the selection of faculty
for this course are:
1. A knowledge of the current methods, procedures, and
industrial situations involved in the inspection of
ventilation systems.
2. Recent relevant practice al experience.
3. Knowledge of the kinds of jobs for which the training
is designed.
4. Ability to instruct adults using appropriate methods,
materials, and techniques.
5. A positive attitude toward air quality management.
Before instructors are actually involved with instruction in
the classroom, the Course Director should conduct thorough briefing
and preparation sessions. During these sessions the Director
should provide an overview of the course, discuss course goals and
lesson objectives, and ensure that the instructors are well
prepared and familiar with the materials, procedures, and
techniques that they will be using.
All instructors should understand the function of the course
goals and lesson objectives, and understand the relationship of
each goal and objective to the instructional materials and to the
pre-test and post-test. Attention to lesson objectives is
essential for successful presentation of course materials and for
successful student performance in this course.
The Course Director should emphasize the importance of
preparation by the instructors. Thorough familiarization with all
the prepared materials is essential for each "expert" instructors.
Problem sessions will require additional preparation, including a
complete run-through to become familiar with the methods used.
PHYSICAL SETTING AND EQUIPMENT
Classroom 1200 to 1500 square feet to accommodate 38
40 people
Furnishings All students should have desks or tables.
Equipment 35mm slide; projector screen, at least 6 feet
square; Chalkboard, erasers and chalk, (or
overhead projector and pens)
Lighting Adequate control to facilitate viewing slides
Course 345 0-5 Introductory Material
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LESSON PLANS
Each lesson plan contains the following information:
1. Lesson goal and objectives
2. Content guide for the instructor
3. Lecture outline
4. Guide for the use of visual aids
5. Solution key for the problem set
In general, each lesson plan is organized as an expended
outline, with keys to the visual aids given in the columns on the
right side of each page. Following each lesson outline is a solved
version of the problem set for that lesson. The instructor must
be familiar with the visual aids and student materials before
attempting to present any lesson.
Instructors may wish to deviate from the format or content for
given lesson, but should maintain the schedule and be sure that
lesson objectives are met. Variations should be in the direction of
greater student participation. Instructors should remember that
the exams reflect the lesson objectives as presented through the
lesson outlines. To stray too far from the prescribed lesson plan
will require changes in the post-test or in the test grading
process.
TESTING INFORMATION
Every student is required to take two tests - a pre-test and
a post-tests. The pre-test is to be given during the first
scheduled class session. It is designed to test the student's
knowledge of the subject matter on entering the course. The score
on this test will not affect the student's grade in the course. It
is used only to estimate learning gains and to inform course
designs about the effectiveness of the instruction. The pre-test
is an open-book test; in other works, the students may use notes,
books, or other reference materials.
The post-test is to be given at the end of the course. It is
essentially a final exam. The test is designed to measure how well
the student has mastered the course goals and lesson objectives.
The student's course grade depends heavily on the performance on
this test. The post-test is also an open-book test.
Course 345 0-6 introductory Material
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GRADING PHILOSOPHY
The guidelines for evaluating student performance and for
granting Continuing Education Units (CEUs) are as follows:
1. The student must:
a. Attend a minimum of 95% of all scheduled sessions.
b. Achieve a grade of at least 70% on the post-test.
2. In its current format, satisfactory completion of this
course will entitle a student to Continuing Education
Units (CEUs), provided that the organization presenting
the course has met other criteria for award of CEUs.
Course 345 0-7 Introductory Material
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AGENDA
INSPECTION OF INDUSTRIAL VENTILATION SYSTEMS
U.S. EPA, APTI COURSE 345
Location:
Room Number
Street Address
City
Phone Number
Moderator:
Name
Street Address
Organization
City, State
Day and Time
Day 1
9:00
9:15
9:45
10:00
10:15
12:00
1:00
2:30
2:45
4:30
Day 2
9:00
10:15
10:30
12:00
1:00
2:15
2:30
3:30
4:30
Subject
Welcome and Registration
Pre-Test
Break
Course Overview
General Principles of Ventilation
Lunch Break
General Principles, Problem Set
Break
Hood Systems
Adjourn
Hood Systems, Problem Set
Break
Duct Systems
Lunch
Duct Systems, Problem Set
Break
Gas Cooling Systems
Gas Cooling Systems, Problem Set
Adjourn
Instructor
Course 345
0-8
Introductory Material
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AGENDA (Continued)
Day 3
9 00 Fan Systems
10 15 Break
11 30 Fan Systems, Problem Set
12 00 Lunch
1 00 Fan Systems, Problem Set (Continued)
2 00 Measurement of Ventilation System
Parameters
2 45 Break
3 00 Measurement of Ventilation System
Parameters (Continued)
4:30 Adjourn
Day 4
9:00 Measurement of Ventilation System
Parameters, Problem Set
10:15 Break
10:30 Ventilation System Inspection
11:30 Lunch
12:30 Ventilation System Inspection, Problem Set
2:15 Break
2:30 Post-test
3:30 Course Critique
4:30 Adjourn
Course 345 0-9 Introductory Material
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Inspection of Industrial Ventilation Systems
Pre-Test
1. A fan with a 22 inch diameter sheave is driven by a 1725 rpm
motor with a 10 inch diameter sheave. What is the estimated
fan speed?
a.
b.
c.
d.
356 rpm
784 rpm
1,163 rpm
2,559 rpm
e. 3,795 rpm
2. One pound molecular weight of a gas at 32°F and 29.92 in. Hg
occupies a volume of:
a. 22.4 liters
b. 359 cubic feet
c. 379 cubic feet
d. 387 cubic feet
e. depends on the gas
3. A pitot tube measures:
a. velocity pressure
b. total pressure and velocity pressure
c. velocity pressure and static pressure
d. total pressure and static pressure
e. total pressure
4. One inch of mercury is equal to how many inches of water?
a. 13.6
b. 14.7
c. 29.92
d. 407
e. 760
5. At what distance from a hood should its static pressure be
measured?
a. 1 duct diameter
b. 2 duct diameters
c. 3 duct diameters
d. 8 duct diameters
e. 10 duct diameters
Course 345
0-10
Introductory Material
-------
6. Pressure exerted by air in motion is called:
a. static pressure
b. total pressure
c. absolute pressure
d. velocity pressure
e. turbulent pressure
7. An inspector finds that a hood static pressure is now 50
percent of its previous value. Approximately how much should
the capture velocity have changed?
a. 50 percent less
b. 71 percent less
c. 50 percent more
d. 71 percent more
e. 29 percent less
8. The coefficient of entry measures the efficiency of a hood to
convert:
a. kinetic energy to potential energy
b. velocity pressure to static pressure
c. static pressure to velocity pressure
d. total pressure to static and velocity pressure
e. hood entry loss to static pressure
9. Canopy hoods are best suited where:
a. thermal currents can be utilized
b. general air flow is low
c. make-up air is to costly
d. room cross-currents are a problem
e. none of the above
10. The air velocity at any point in front of a hood that is
necessary to overcome air currents and cause the air to flow
into the hood is called:
a. face velocity
b. slot velocity
c. plenum velocity
d. capture velocity
e. duct velocity
Course 345 0-11 Introductory Material
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11. A flat plate that is inserted perpendicular to the centerline
of a duct for the purpose of restricting air flow is called
a:
a. damper
b. check valve
c. solenoid
d. blast gate
e. bellows
12. How much enthalpy change occurs when 2 pounds of air are
cooled from 1000 F to 10°F?
a. 323.6 Btu
b. 224.5 Btu
c. 449.0 Btu
d. 567.9 Btu
e. 748.1 Btu
13. Which of the following is not a centrifugal fan?
a. backward curved
b. forward curved
c. axial flow
d. radial
e. backward curved airfoil
14. At a point just upstream of a fan, measurements give a
velocity pressure of 1.0 in. H2O and a static pressure of 3.5
in. H20. What is the total pressure?
a. +2.5 in. H2O
b. -2.5 in. H2O
c. -4.5 in. H20
d. +4.5 in. H2O
e. +3.5 in. H2O
15. A freely suspended flanged hood 2 inches wide and 72 inches
long exhausts 600 cfm. What is the velocity at a point 12
inches in front of the opening?
a. 3.2 fpm
b. 38.5 fpm
c. 600 fpm
d. 100 fpm
e. 54.5 fpm
Course 345 0-12 introductory Material
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16.
A 12 inch diameter hood has a flowrate of 1,444 acfm at
70°F. If the hood entry coefficient is 0.69, what is the
hood static pressure?
a.
b.
c.
d.
e.
0.21 in. H20
0.11 in.
0.69 in,
0.44 in,
H20
H20
H20
0.30 in. H20
17. An air stream is found to have a dry-bulb temperature of
170°F and a wet-bulb temperature of 100°F. What is the
relative humidity?
a. 10 percent
b. 15 percent
c. 20 percent
d. 25 percent
e. 30 percent
18. What is the static pressure loss when a 700 acfm air stream
at 100°F flows through a 6 inch diameter elbow with a radius
of 12 inches?
a.
b.
c.
d.
e.
0.
0.
0.
0.
0.
13
20
21
25
27
in.
in.
in.
in.
in.
H
H
H
H
H
2°
2°
2°
2°
,0
19. How many gallons of water initially at 60"F must be
evaporated each minute to cool a 50,000 acfm gas stream from
1000 F to 400°F?
a. 20.6
b. 28.4
c. 50.0
d. 67.7
e. 93.2
20. Static pressure measurements at the inlet and outlet of a fan
give -7.3 in. H20 and 0.7 in. H20, respectively. Inlet
velocity is estimated at 3,500 fpm and the gas stream
temperature is 250°F. What fan static pressure would
normally be used to enter a fan ratings table?
a.
b.
c .
d.
e.
6
7
7
8
9
.6
.3
.4
. 0
.9
in.
in.
in.
in.
in.
H
H
H
H
H
2
2
2
2
2
O
0
0
0
O
Course 345
0-13
Introductory Material
-------
Inspection of Industrial Ventilation Systems
Pre-Test Answer Sheet
Name:
1. a
2. a
3. a
4. a
5. a
6 . a
7. a
8. a
9. a
10. a
b c
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18. a b c d e
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Course 345
0-14
Introductory Material
-------
Name:
Inspection of Industrial Ventilation Systems
Pre-Test Answer Sheet Key
1. a b J c d e
2 . a f b) c d e
3. a b c ( d e
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4. ( a ) b c d e
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Course 345
0-15
Introductory Material
-------
NOTE
The Post-Test and Post-Test Answer Sheet for Course #345 - Emission Capture and
Gas Handling System Inspection - are available to course instructors by contacting the
Air Pollution Training Branch, MD-17, Environmental Protection Agency, Research
Triangle Park, NC 27711, telephone: 919-541-2401.
(Pages 0-16 through 0-21 are omitted from this manual copy)
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LESSON 1
GENERAL PRINCIPLES OF VENTILATION
Goal:
To develop a basic understanding of the character and behavior of
air streams.
Objectives:
At the end of this lesson the student should be able to:
1. Define standard air conditions
2. Calculate the apparent molecular weight of a mixture
3. Use the ideal gas law to relate the pressure, volume and
temperature properties of an air stream
4. Define density, specific volume and specific gravity
5. Define relative and absolute humidity
6. Define dry-bulb, wet-bulb and dew-point temperatures
7. Calculate the enthalpy change of a substance
8. Use a psychrometric chart to determine the properties of an
air-water vapor mixture
9. Apply the continuity relationship to an air stream
10. Define and manipulate total pressure, velocity pressure and
static pressure
11. Calculate velocity pressure from the velocity and
temperature of an air stream
12. Calculate velocity from the velocity pressure and
temperature of an air stream
Section 1 General Principles
1-1
-------
List of Slides
1-1 Ventilation fundamentals
1-2 Two sections of lecture
1-3 Properties of air and air-water vapor mixtures
1-4 Standard air
1-5 Molecular weight
1-6 Ideal gas law
1-7 Volume conversion for temperature and pressure
1-8 Density and specific volume
1-9 Specific gravity
1-10 Gibbs-Dalton rule of partial pressures
1-11 Relative saturation, relative humidity and absolute
humidity
1-12 Dry-bulb, wet-bulb and dew-point temperatures
1-13 Enthalpy
1-14 Defining equation for enthalpy
1-15 Enthalpy of water vapor
1-16 Enthalpy of air-water vapor mixture
1-17 Determination of enthalpy difference
1-18 Psychrometric chart
1-19 Principles of fluid flow
1-20 Continuity
1-21 Mass balance on flow system
1-22 Bernoulli's equation
1-23 Bernoulli's equation in units of head
1-24 Bernoulli's equation applied to flowing system
1-25 Bernoulli's equation applied to flowing system
1-26 Illustration of VP, SP and TP
1-27 Determination of velocity from velocity pressure
Section 1 General Principles
1-2
-------
I. Introduction SLIDES AND
NOTES
A. To conduct effective inspections, it is
important to have a firm understanding of the 1-1
basic information that affects the character-
istics and behavior of air streams.
B. Lesson is divided into two sections
1. Properties of air and air-water vapor 1-2
mixtures - definition of parameter is
important in ventilation system evaluation
and in techniques for determining them.
2. Fundamentals of fluid flow - discussion of
continuity and momentum relationships with
emphasis on Bernoulli's equation and its
implications.
II. Properties of air and air-water vapor mixtures
A. Standard air: air with a density of 0.075
Ib /ft3 and an absolute viscosity of 1.225 x 1-3
10* lbm/ft-sec.
1. The standard air density and absolute 1-4
viscosity apply to dry air at the standard
temperature of 70°F and the standard
pressure of 29.92 in. of mercury. These
values are used throughout this course
whenever standard conditions are required.
2. The U.S. EPA uses 25°C (77°F) as a definition
of "standard temperature. This is used in
many calculations involving regulatory
compliance.
3. Other organizations and engineering
disciplines have adopted slightly different
definitions of "standard" temperature and
pressure.
B. Molecular weight: air is a mixture so it has
no true molecular weight - does have an
apparent molecular weight that is calculated 1-5
from its composition.
Section 1 General Principles
1-3
-------
= S (Cent) (^component) trefer to
SLIDES AND
NOTES
Student Manual, pp. 1-1 and 1-2]
2 . Molecular weight of dry air often approxi-
mated as 28.95 Ib/lb-mole [explain concept
of Ib-mole]
3 . For moist air
MWuetair = < * ~ Cwater) (^dry air) + (Cweter) (^ater)
1-6
C. Ideal gas law: relates pressure, volume and
temperature properties of a pure substance or
mixture.
1. PV = nRT
P = absolute pressure (lbf/ft2)
V = gas volume (ft3)
n = number of moles (Ib-moles)
R = constant (1545 ft-lbf/lb-mole-°R)
T = absolute temperature (°R)
2. Other values of R [write on board]
1545 Lbf-ft/lb-moles °R
10.73 psia-ft3/lb-mole-°R 1~7
82.06 cm3-atm/g-mole-°K
8.31 x 103 kPa-m3/kg-mole-°K
0.73 atm-ft3/lb-mole-°R
21.83 (in Hg.) (ft3)/(lb mole-°R)
3. If moles don't change:
PV/T = nR = constant
or
PIVI/T! = P2V2/T2
or
V1 =
(T,/T2)
May also be used to calculate molar volume
[write on board]
V/n = RT/P
Section 1 General Principles
1-4
-------
D. Density and specific volume:
1. Density = weight/unit volume SLIDES AND
NOTES
2. Specific volume =
volume/unit weight = I/density 1-8
3. For an ideal gas -
Density (p) =
MW,lbm 530
387 ft3.
T, °R
(P, in. Her)
29.92 in. HgJ
4. Refer students to Table 1-1 in Student
Manual, p. 1-4.
E. Specific gravity: ratio of the density of a
material to the density of some reference
substance. 1-9
1. For a gas, specific gravity = rgas/rdl7air
2. For an ideal gas, specific gravity =
F. Relative and absolute humidity:
1. Gibbs-Dalton rule of partial pressure -
Components exert a pressure the same as if
it were alone in the same total volume at
the same temperature.
2. Relative saturation = / 1~10
3. Relative humidity = 1-11
Relative saturation x 100
4. Absolute humidity = Weightwltcr/Weightdiy ^
G. Dry-bulb, wet-bulb and dew point temperatures
1. Temperature measured with a standard 1-12
thermometer is termed dry-bulb temperature.
2 . A standard thermometer with a wet porous
wick over the sensing bulb is a wet-bulb
thermometer.
a. Water from the wick will evaporate into
a moving air stream.
Section 1 General Principles
1-5
-------
b. Wick cools until the rate of energy SLIDES AND
transferred to the wick equals the rate NOTES
of energy loss by the evaporating water
- temperature at equilibrium is termed
wet-bulb temperature.
c. Rate of evaporation depends on the
moisture content of the air - provides
an indication of the humidity.
3. Dew-point temperature is the temperature at
which condensation begins when moist air is
gradually cooled - it is the saturation
temperature corresponding to the absolute
humidity.
H. Enthalpy: the measure of the thermal energy 1-13
of a substance in Btu/lb - Btu is the amount
of heat necessary to raise one pound of water
from 59°F to 60°F at a pressure of one
atmosphere .
1. Enthalpy of a substance at a given 1-14
temperature has no practical value except
in relation to the enthalpy at another
temperature:
h = enthalpy (Btu/lb)
Cp = heat capacity at constant
pressure (Btu/lb-°F) [refer
students to Table 1-1 in
Student Manual, p. 1-4 J
t = temperature of substance (°F)
tpef = reference temperature (°F)
tref for dry air usually equals
0°F [highly variable]
tref for water usually equals 32 °F
Enthalpy of water vapor is equal to the 1-15
enthalpy of the water plus the latent heat
of vaporization.
For an air-water vapor mixture: 1-16
h (Btu/lbdryajr) = hdryajr + f(hwatervapor)
0 = absolute humidity (lbwater/lbdry air)
Section 1 General Principles
1-6
-------
4. Usually interested in enthalpy difference: SLIDES AND
NOTES
AH = h2 -
- tref) - (CpMt, - tpef)
5. Can also determine enthalpy difference from
tabulated values [refer students to Table
1-2 in Student Manual, p. 1-7]. Before
subtracting two enthalpy values, you must
confirm that they were determined for the
same reference temperature.
I. Psychrometric chart: graphical representation 1-18
of properties of air-water vapor mixtures.
1. Demonstrate location/determination of
a. dry-bulb temperature
b. wet-bulb temperature
c. absolute humidity
d. specific volume
e. enthalpy at saturated and non-saturated
conditions
f. dew-point temperature
g. relative humidity
2. Density of an air-water vapor mixture:
fixture = (1 + *)/"
)
II. Principles of fluid flow 1-19
A. Consider flow through the tube shown:
1. Mass flow rate into the tube, G1 , is 1-20
p1V1Al ; mass flow rate out of the tube,
G2, is /02V2A2
Section 1 General Principles
1-7
-------
2. If no accumulation or removal: SLIDES AND
IOTES
1-21
G, = G2 NOTES
or
P1V1A1 = P2V2A2
or, if p, = P2
V1A1 = V2A2
B. As fluid flows through a tube, its momentum
and pressure may change.
1. Applying the relationship, force equals
rate of change of momentum to a fluid
element and then integrating over the
cross-section of the duct, neglecting
frictional forces and assuming
incompressibility , gives Bernoulli's
equation:
V2/2 + P/p + gz = constant 1-22
V = fluid velocity
P = fluid pressure
p = fluid density
g = acceleration of gravity
z = elevation of fluid
2. Rearranging the terms to have units of 1-23
length gives:
V2/2g + P/pg + z = constant
V2/2g = velocity head (ft)
P/P9 = pressure head (ft)
z = potential head (ft)
C. Consider the situation shown, in which an open 1-24
tube has been inserted into a flowing fluid:
1. Since the terms in Bernoulli's equation sum
to a constant, we may write:
(V1)/2g + P^pg + z, = (V2)2/2g + P2/pg
Section 1 General Principles
1-8
-------
2. But z1 = z2 and V2 = 0. Substituting gives: SLIDES AND
NOTES
V,2/2g + P,/pq = P2/pg 1-25
V12/2g = velocity pressure
P.,/pg = static pressure
P2/pg = total pressure
3 . Another way of writing this is [write on
board] :
VP + SP = TP
VP = velocity pressure
SP = static pressure
TP = total pressure
4. Discuss relationship between VP, SP and TP 1-26
using diagram.
Velocity can be determined from velocity 1-27
pressure:
1. Converting the units of the velocity
pressure term so that it has unit of inches
of water gives [write on board] :
VP = [(V/60)2/2g] (pa/PH)12
aH
VP = velocity pressure (in. of H20)
V = velocity (ft/min)
pa = air density (lb/ft3)
pu = water density (lb/ft3)
2. Substituting a water density at 70°F of
62.302 lb/ft3 and a gravity acceleration at
sea level of 32.174 ft/sec2 gives [write on
board] :
VP = pfl(V/1096.7)2
3. Rearranging gives:
V = 1096.7 (VP/p)°-5
4 . For standard air
(p = 0.075 lb/ft3) :
V - 4005(VP)°-5
Section 1 General Principles
1-9
-------
PROBLEM SET 1
GENERAL PRINCIPLES OF VENTILATION
1-1. How much volume in ft3 does 1 Ib-mole of air at 70°F and
29.92 in. Hg. occupy? What is the volume if the air is at
32°F and 29.92 in. Hg?
Solution
a. 70°F = 70 + 460
29.92 in. Hg
V =
n
RT
530 °R
14.7 psia
no. 73 psia-ft3/lb.-mole
14.7 psia
r530°R1
b.
32°F = 32 + 460
V
n
RT
P
387 ft3/lb-mole
= 492 °R
[10.73 psia-ft3/lb-mole °Rir492
14.7 psia
= 359 ft3/lb-mole
1-2. A duct has a 1,500 acfm air flow at 110°F and -18.0 inches
of water. Atmospheric pressure is 30.12 in. Hg. What is
the flow rate at standard conditions?
Solution
T, = 110°F = 110 + 460
P. = 30.12 in. Hg. - 18/13.6
T^ = 530°R
Patd = 29.92 in. Hg.
V, = V2 (P2/P,) (T,/T2)
V, = 1500 .(28.80/29.92)(530/570)
V, = 1342.5 scfm
570°R
28.80 in Hg.
Section 1
1-10
General Principles
-------
1-3. Temperature measurements in an air duct indicate a dry-bulb
temperature of 83°F and a wet-bulb temperature of 60°F.
Determine enthalpy, humidity ratio (moisture content),
dewpoint temperature and relative humidity/
Solution
From psychrometric chart:
Enthalpy = 26.5 - 0.15
26.35 Btu/lb of dry air
Absolute Humidity = 40 grains/lb of dry air
= 0.0057 Ib/lb of dry air
Dew Point = 42.5 °F
Relative Humidity = 25%
1-4. What is the flowrate in a 6 in. diameter duct if the average
velocity pressure was measured and found to be 0.76 in. of
water and the gas temperature is 100°F? If the duct decreases
to 4 inches in diameter downstream, what will be
the new velocity and velocity pressure?
Solution
a. Ad = (7T/4) (6/12)2 = 0.1963 ft2
P100 f = 0.0708 lb/ft3
Q = 1096.7 Ad (VP/p)°-5
(096.7/0.1963 f t2) ( 0 . 76/0 . 07 08 ) °'5
= 705.3 acfm
b. Ad = (7T/4) (4/12)2 = 0.0872 ft2
V = 705.3 acfm/0.0872 ft2 = 8079 . 0--ft/min.
VP = p (V/1096.7)2
= 0.0708 lb/ft3 (8079.0 ft/min / 1096.7 ft/min.)2
= 3.84 inches of water
Section 1 General Principles
1-11
-------
1-5. How much enthalpy change occurs when a gas stream is cooled
from 2000 °F to 250 °F?
Solution
h200Q = 509.5 Btu/lb
h25Q = 45.7 BtU/lb
Ah = 463.3 Btu/lb
Section 1 General Principles
1-12
-------
LESSON 2
HOOD SYSTEMS
Goal:
To develop an understanding of the different hood types, their
design and performance characteristics, and techniques for their
evaluation.
Objectives:
At the end of this lesson the student should be able to:
1. State the importance of hood efficiency in the total
efficiency of a ventilation system
2. Recognize the different types of hoods and how each of
them functions
3. State the three principles of good hood design
4. List the factors that affect hood performance
5. Determine appropriate capture velocities for given
situations
6. Determine the capture velocity of an existing hood from
flowrate and configuration information
7. List the parameters that affect the capture of hot plumes
with overhead canopy hoods
8. Determine hood static pressure from flowrate and
configuration information
9. Use measured hood static pressure and configuration
information to estimate flowrate
10. Conduct effective inspections of hood systems
Lesson 2 2-1 Hood Systems
-------
List of Slides
2-1 Hood systems
2-2 Goal of good hood design
2-3 Total penetration relationship
2-4 Types of hoods
2-5 Hood design principles
2-6 Bucket elevator hood
2-7 Ladle hood
2-8 Bag filling station hood
2-9 Grinder hood
2-10 Exterior hoods
2-11 Electric arc furnace hood
2-12 Push-pull hood
2-13 Push-pull hood
2-14 Factors affecting hood performance
2-15 Capture velocity
2-16 Range of capture velocities
2-17 Cold flow
2-18 Flow into unflanged hood
2-19 Flow into flanged hood
2-20a Assorted hood flow relationships
2-20b Assorted hood flow relationships
2-21 Hot flow
2-22 Application of Bernoulli to hood flow
2-23 Simplification of Bernoulli relationship
2-24 Vena Contracta
2-25 Hood Entry Coefficient
2-26 Relationship between hood loss factor and entry
coefficient
2-16 Simplification of Bernoulli relationship
2-27 Estimating hood volume
Lesson 2 2-2 Hood Systems
-------
I. Introduction SLIDES AND
NOTES
A. To conduct effective inspections, it is
important to understand the concepts behind 2-1
good hood design and to know how to evaluate
hood performance.
B. The goal of good hood design in high capture
efficiency. The importance of this is 2-2
illustrated by the following relationship:
2-3
Penetration = 1 - Fractional Efficiency
Pt = Pt + (i - Pt 1 Pt
total hood *• hood' collector
II. Types of hoods
2-4
A. Enclosure hoods - envelope the process to the
maximum extent possible.
2-5
1. Designer envisions a total enclosure and
then removes portions as needed for material
and worker access.
2. Contains and removes contaminants from
within the enclosure, rather than capturing.
3 . Air volume requirement usually the lowest of
the three hood types.
4. Examples of enclosure hoods:
a. The bucket elevator is an example of an 2-6
enclosure-type hood. Buckets mounted on
a rotating vertical belt are used to
transfer material from one elevation to
another. To reduce emissions from this
process, a housing is provided that
completely encloses the operation, and
suction is provided to contain and remove
the contaminants. The only openings are
those necessary for receiving and
transferring the material.
b. The ladle hood is an enclosure-type hood. 2-7
Molten metal is transferred to a hot
metal ladle from a rotating-dump torpedo
car. The ladle hood contains and removes
the emissions as they evolve from the
transfer operation.
Lesson 2 2-3 Hood Systems
-------
Once the emissions have subsided, the SLIDES AND
ladle hood is tilted out of the way so NOTES
that the ladle may be moved to other
operations.
B. Receiver hoods - located adjacent to the point
of contaminant release.
1. Hood oriented to receive emissions as they
are ejected from the process.
2. Capture capability that must be provided by
air stream is reduced.
3. Examples of receiver hoods:
a. The bag filling process utilizes a 2-8
receiving-type hood. To avoid
interferences with the weighing scale,
the hood is mounted above the bag opening
to take advantage of the normal vertical
travel of emissions and somewhat reduce
the capture flow that might be required
with another orientation.
b. The grinding wheel hood is primarily a 2-9
receiving-type hood. Material removed by
the wheel has a normal travel direction
down and to the rear. The hood is mounted
in this location to take advantage of
this and reduce the necessary capture
flow. The hood also extends around the
top and sides of the wheel to provide for
enclosure of any contaminants that follow
the wheel motion.
c. The EOF hood system utilizes two
receiving-type hoods. Buoyant forces
carry the emissions into the primary hood
during the melting phase and into the
secondary hood during charging.
C. Exterior hoods - located an extended distance
away from source.
1. Principal example is the overhead canopy 2-10
employed with hot sources.
Lesson 2 2-4 Hood Systems
-------
2. Relies on normal movement of the buoyant SLIDES AND
plume to carry contaminants into the hood. NOTES
3. Subject to losses due to plume meander and
cross-drafts.
4 . Requires the largest air volume of the three
hood types.
5. Control of emissions from electric-arc 2-11
furnaces typically uses a canopy hood in
combination with an enclosure-type hood at
the furnace. During the melting cycle,
emissions are controlled from the hood
mounted on the furnace, with only a small
amount of flow drawn from the canopy to
remove any contaminants that might escape
the furnace. During charging operations,
the roof swings off the furnace to provide
access, and all air flow is directed to the
canopy to collect the significant plume that
usually results. In the tapping cycle, the
furnace tilts to pour the molten steel into
a ladle, disconnecting the furnace hood from
the duct through a break-flange arrangement.
In the system shown, air flow is then
directed to an enclosure hood at the ladle.
In other systems, the air flow is again
directed to the canopy hood for contaminant
capture and removal.
D. Push-pull hoods.
1. A controlled jet of air is directed across 2-12
the contaminant source and in the direction
of the exterior hood. The exterior hood
primarily serves to receive the air jet and
the contaminants carried with it.
2. Higher velocities with distance from the jet
source result in reduced air vol u-m e
requirements.
3. System must be carefully designed and
controlled to avoid dispersing contaminants
into the workspace.
4. Disturbance of the jet can occur if
obstructions are placed in its path,
reducing the system's effectiveness.
Lesson 2 2-5 Hood Systems
-------
5. A variation of the push-pull system is the SLIDES AND
air curtain hood. Jets of air are directed NOTES
downward to form a barrier that contains the
emissions while they are drawn off by the 2-13
exhaust system.
III. Hood design principles 2-5
A. Whenever possible, an enclosure hood should be
employed.
B. If an enclosure hood cannot be used, the hood
should be placed as close to the source as
possible and aligned with normal contaminant
flow.
C. To improve hood performance, duct take-offs
should also be placed in-line with normal
contaminant flow.
IV. Factor affecting hood performance 2-14
A. Room air currents associated with the workspace
ventilation system - currents of as little as
50 feet/min may be enough to affect the
performance of some hoods.
B. Thermal air currents from heat generating
equipment and processes - even low heat
releases, such as those from an electric motor,
may be enough to disturb hood performance.
C. Machinery motion - rotating or reciprocating
machinery can be a source of significant air
currents.
D. Material motion - downward motion of material
will create a downward air current that will
make the upward motion of contaminants more
difficult to achieve.
E. Operator movements - rapid movements of an
operator can create air currents of 50-100
feet/min.
V. Capture velocity
A. Capture velocity is defined as that air 2-15
velocity at a point in front of a hood or at
Lesson 2 2-6 Hood Systems
-------
the hood face that is necessary to overcome SLIDES AND
existing air currents and cause the contain- NOTES
inated air to move into the hood.
B. Required capture velocity will depend on both
the direction and velocity of the contaminants
at the desired point of capture, as well as the
level of disturbing air currents that must be
overcome.
C. A general guide for appropriate capture
velocities is shown in the table. 2-16
1. Values at the low end of the range would he
appropriate when disturbing air currents are
low, the toxicity of the contaminants is
low, or the hood is large, resulting in a
large air mass in motion.
2. Values at the high end of the range would eb
appropriate when air currents are high, the
toxicity of the contaminants is high, or the
hood is small.
VI. Cold flow into hoods 2-17
A. Relies totally or in part on the ability to
provide enough energy to capture a contaminant
and draw it into the hood, i.e., to develop the
necessary capture velocity-
B. Capture velocity decreases with distance from
the hood face. In general, capture velocity 2-18
one hood diameter away from the hood face is
less that 10 percent of the velocity at the
hood face.
C. Although the situation is improved with the 2-19
addition of a flange, the improvement is only
about 25 percent.
D. In contrast, 10 percent of the face velocity of
a blowing jet would be found about thirty
diameters away.
E. Expecting a hood to provide high capture
velocity several diameters away from the hood
face may be expecting too much.
F. Discuss the relationships for determining air
volume requirements to provide a desired
Lesson 2 2-7 Hood Systems
-------
capture velocity a given distance from the hood SLIDES AND
face for the different hood configurations. NOTES
Point our that, for an existing hood, these
same equations can be used to estimate capture 2-20a
velocity once the hood flowrate is known. and
2-10b
VII. Hot flow into hoods 2-21
A. Relies more on the buoyancy of the hot plume to
carry the contaminants into the hood than on
the ability to generate a capture velocity.
B. The velocity at the hood face need only be
about the velocity of the plume at that point.
C. As a hot plume rises it expands and cools by
entraining outside air and its velocity
decreases.
D. As the distance between the source and the hood
increases, the air volume required to capture
and remove the plume increases.
E. The slower moving upper portion of the plume is
susceptible to being disturbed by air currents,
causing it to move out from under the hood
VIII. Hood pressure losses 2-22
A. To cause air to move into a hood it is
necessary to provide the energy needed to
accelerate the air from essentially zero
velocity up to the velocity in the duct
connected to the hood and to overcome the entry
resistance of the hood itself.
B. Consider the hood system shown. Applying the
Bernoulli equation to this situation would
indicate that the total pressure at point'- 1
would equal the total pressure at point 2, or:
SP, + VP, = SP2 + VP2
C. But there is no air motion at point 1; 2-23
therefore:
0 = SP2 + VP2
or
SP2 = -VP2
Lesson 2 2-8 Hood Systems
-------
D. In reality, entering air forms a "vena SLIDES AND
contracta", causing the velocity to increase NOTES
and then decrease. This is not a perfect
process and results in an energy loss as static 2-24
pressure is converted to velocity pressure and
then back to static pressure. Therefore, we
define the hood static pressure loss, SPh, as:
sph = -SPZ = VP2 + he
he = hood entry loss
E. Hood entry loss is usually expressed as some
fraction of the velocity pressure in the duct
attached to the hood:
he = FhVP
Fh = hood loss factor
F. Hood losses may also be described by the hood
entry coefficient, Cg:
Ce = (VP/SPJ0-5
o ^ *2 cr
G. The hood entry coefficient can be related to
the hood loss factor by recalling that
SPh = VP + he and he = FhVP [Note: Instructor
may wish to develop this relationship on the
board.]. Thus:
he = {(1 - Ce2)/Ce2}VP 2_26
Therefore
Fh = (1 - Ce2)/Ce2
and
Ce = {l/(l+Fh)}°-5
IX. Evaluation of hood performance
A. Measurements of the hood static pressure can be
used to estimate the flowrate at the hood. 2-27
Q = VA = 1096.7A(VP/r)0'5
= 1096.7ACe(SPh/r)0'5
Q = volumetric flow rate (ft3/min)
V = hood face velocity (ft/min)
A = hood inlet area (ft2)
r = air density (lb/ft3)
Lesson 2 2-9 Hood Systems
-------
B. Performance and condition of a hood should be SLIDES AND
visually evaluated. NOTES
1. If dusty material is being handled by a
process, the amount of fugitive losses
provide an excellent indication of the
effectiveness of the hood system.
Refraction lines due to the escape of gases
contaminants may also be noticed.
2. The physical condition of the hood should be
assessed. Particular attention should be
paid to any modifications that have been
made to the original hood design or to any
damage that it may have sustained that may
affect its performance.
3. On movable hoods, the connection between te
hood system and the duct system should be
assessed to determine the "fit" of the
junction. Break-flanges should have a
maximum gap of 1-1% inches.
4. Hood position should be evaluated to assess
the effects of cross-drafts or other air
motion on hood capture efficiency.
Lesson 2 2-10 Hood Systems
-------
PROBLEM SET 2
HOOD SYSTEMS
2-1. A simple 12 inch diameter wide-flanged hood has an air fkw
of 400 acfm. At what distance away, along the centerline,
does the velocity equal 50% of the hood face velocity?
10% of the hood face velocity?
Solution
a. Ah = (7T/4) (12/12)2 = 0.7854 ft2
V = (4000 ft3/min)/ 0.785ft2 = 509.3 ft/min
0.5V = 254.7 ft/min
Q = 0.75V (10X2 + A)
X = [ (O/ (0.75)(254.7)) - 0.785
10
r
= 1(4007 (0.75) (254.7) ) - 0.7854
10
= 0.36 ft = 4.3 inches
0.5
b. 0.1V = 50.9 ft/min
X
(400/ (0.75) (50.9) ) - 0.78541 °'5
10
= 0.99 ft = 11.8 inches
Lesson 2 2-11 Hood Systems
-------
2-2. An acid dip tank is equipped with slot vents along both
long sides. Slot velocity is 2,000 fpm and the total
volume of 1,250 acfm is exhausted by a 7 inch diameter
duct. What is the hood static pressure, assuming a duct
entry loss of 0.25 VP?
Solution
Assume standard air
VP
slot
V
VP
(2000/4005)2
(7T/4) (7/12)2
1250 ft3/min
0.2673 ft2
0.25 inches of water
0.2673 ft2
4,676.4 ft/min
duct
2 _
(4676.4/4005)^ = 1.36 inches of water
1.78
0.25 VP
duct
1.78 (0.25) + 0.25(1.36)
0.79 inches of water
SP,
VP
duct T "e
1.36 + 0.79
2.15 inches of water
Lesson 2
2-12
Hood Systems
-------
2-3. Measurements in an 18 inch diameter dust just downstream of
hood give a hood static pressure of 2.5 inches of water and
a temperature of 250 °F. Assuming a hood entry loss of
1.5 VP, what is the actual gas flow rate?
Solution
Ah = (TC/4) (18/12) = 1.7671 ft2
P250 = 0.0558 lb/ft3
Fh = 1.5
Ce = (__1 )°'5 = [I/ (1 + l-5)]°-5
1 + ^h
0.53
Q = 1096.7 A Ce (SPh/p)0'5
1096.7 (1.7671) (0.53) (2 . 5/0 . 0558) °'5
3172.3 acfm
Lesson 2 2-13 Hood Systems
-------
2-4. A recent hood inspection finds a 40% drop in hood static
pressure compared to previous measurements. What is the
percent change in hood face velocity?
Solution
1
V oc (SPh)°-5
Therefore
v1 / v2
SPM = o.4 sph>2
V, = V2 (0.4 SPh(2/SPh(2)°-5
0.63 V2
The new velocity would be 63% of
the previous velocity.
Lesson 2 2-14 Hood Systems
-------
LESSON 3
DUCT SYSTEMS
Goal:
To develop an understanding of duct systems, their design and
performance characteristics, and techniques for their evaluation.
Objectives:
At the end of this lesson the student should be able to:
1. State the three types of energy losses that occur in duct
systems.
2. State three methods for estimating losses in duct systems.
3. Use the velocity pressure method to estimate frictional
losses in straight ducts.
4. Use the velocity pressure method to estimate losses in
elbows.
5. Calculate total static pressure losses in a duct segment.
6. Estimate hood flow rate from static pressure measurements
in a duct.
7. State appropriate transport velocities for different
situations.
8. Recognize the potential problems from low transport velocity
in dust containing systems.
9. Recognize areas having high potential for duct erosion.
10. State the purpose of balancing duct systems.
11. State two techniques for balancing duct systems and the
advantages and disadvantages of each.
12. Conduct effective inspections of duct systems.
Lesson 3 3-1 Duct Systems
-------
List of Slides
3-1 Duct systems
3-2 Application of Bernoulli equation to duct segment
3-3 Effect of friction and non-ideal conversions
between SP and VP
3-4 Simplification assuming constant velocity in duct segment
3-5 Types of duct losses
3-6 Techniques for estimating losses
3-7 Estimating frictional losses in straight duct
3-8 Estimating fitting losses
3-9 Velocity pressure calculation method
3-10 Velocity pressure calculation method
3-11 Velocity pressure calculation method
3-12 Result of pressure loss calculations
3-13 Transport velocity
3-14 Range of design velocities
3-15 Build-up concerns
3-16 Distribution of flow in branched ductwork
3-17 Branched duct example
3-18 Techniques to obtain balance
3-19 Characteristics of balance through design
3-20 Characteristics of balance with dampers
3-21 Branched duct example
Lesson 3 3-2 Duct Systems
-------
I. Introduction SLIDES AND
NOTES
A. Once contaminants from a process have been
captured by the hood system, it is the 3-1
responsibility of the duct system to convey
these contaminants to the collection device and
then convey the cleaned air on to its discharge
point .
B. In designing duct systems, much of the concern
is in selecting proper size ducts and in being
sure the system is "balanced" so that the
proper quantities of air are drawn from each
hood.
C. As inspectors, the design of a duct system is
of only limited concern. However, it may be
necessary to use some of the same tools as the
designer in order to accomplish inspection
goals .
II. Duct pressure loss
A. Consider the duct segment shown. 3-2
Applying Bernoulli's equation to points 1 and
2, we can write:
TP, = TP2
B. Because of friction between the gas stream and
the duct walls and because of non-ideal
conversion between static pressure and velocity
pressure as the gas stream accelerates or
decelerates, pressure losses between the two
points occur. Thus: 3-3
TP1 = TP2 + hL
or
VP1 = SP2 + VP2 + hL
C. If we assume that the velocity between points 3-4
1 and 2 is approximately constant, then VP1 =
VP2 and:
SP1 = SP2
D. Here, hL is the total pressure loss due to
friction and non-ideal pressure conversions.
For calculation purposes, we divide these
losses into three categories: 3-5
Lesson 3 3-3 Duct Systems
-------
1. Frictional losses in straight duct- SLIDES AND
involves the loss due to friction with the NOTES
walls.
3-5
2. Fitting losses - occur when the gas stream
flows through elbows, entries, transitions
and other types of fittings; results from
friction with the walls of the fitting and
with increased energy loss due to an
increased level of turbulence.
3. Acceleration losses - associated with
changes in the velocity of the gas stream;
accelerating a gas stream requires the input
of energy, while decelerating a gas stream
may result in a gain of energy. The amount
of pressure loss or gain depends on the
relative abruptness of the change.
E. Because our interest in duct losses will
usually be over relatively short distances, our
determination of losses will be confined to
those associated with straight ducts and
fittings.
F. There are three techniques in general use for 3-6
estimating these losses:
1. Equivalent length method - fitting losses
are expressed in length of equivalent
straight duct; total losses are calculated
by adding the equivalent length for the
fittings to the actual length of straight
segments and then multiplying by a factor
that expresses the pressure loss per length
of duct.
2. Velocity pressure method - both straight
duct and fitting losses are expressed as a
factor times the velocity pressure in the
duct segment.
3. Total pressure method - both straight duct
and fitting losses are expressed as a factor
times the total pressure in the duct
segment.
4. The technique to calculate duct system
losses that is used in this course is the
velocity pressure method.
G. Frictional losses in straight duct are 3-7
expressed as:
Lesson 3 3-4 Duct Systems
-------
hu = HfL'VP SLIDES AND
NOTES
Hf = velocity pressure loss per foot of
duct
L = length of duct, feet
1. The straight-duct loss factor, Hf, can be
determined from the following empirical
equation:
Hf = 0.0307V°-533/Q°-612 - 0.^937/Q0-079^-066
V - air velocity in feet/minute
Q = volumetric flowrate in cubic
feet/minute
D = duct diameter in inches
2. The straight-duct loss factor can also be
determined from Figure 3-1 in Student
Manual, pp. 3-4 and 3-5 [refer students to
figure].
3. Losses for rectangular ducts are determined
using an equivalent diameter and the
calculated velocity at that diameter. The
equivalent diameter in inches is determined
from [write on board]:
De = 1.3(AB)°-625/(A + B)°-25
where A and B are the lengths of the sides
of the rectangular duct in inches.
H. Fitting losses are expressed as: 3-8
hL2 = F-VP
F = fitting loss factor
1. There are a variety of fittings used -in
ventilation systems and factors for their
resistance can be found in a number of
reference texts.
2. The fitting of most interest for short
distance calculations is that for elbows.
These factors are given for 90° round elbows
in Table 3-1 in Student Manual, p. 3-6.
Resistances for other than 90° elbows are
determined as a percentage of the 90° elbow
resistance.
Lesson 3 3-5 Duct Systems
-------
Ill Velocity pressure calculation method SLIDES AND
NOTES
A. Calculating the pressure loss from one duct
location to another requires determining the 3-9,
loss of the straight sections and the loss of 3-10,
all the fittings and then adding them together and
to get the total loss. The specific step-wise 3-11
procedure for a segment, beginning at the hood,
is as follows:
1. Determine the duct velocity and calculate
the velocity pressure.
2. Determine the hood static pressure.
3. Multiply the straight duct length by the
friction loss factor.
4. Determine the number and type of all
fittings. Multiply the loss factor for each
type of fitting by the number of that type
and sum for all types.
5. Add the results from Steps 3 and 4 and
multiply the result by the velocity pressure
from Step 1.
6. Add the result from Step 5 to the hood
static pressure from Step 2. If there are
other losses (expressed in inches of water
column), add them also.
B. This calculation procedure gives the total 3-13
energy, expressed as static pressure, that is
needed to move the gas volume through the duct
segment.
IV. Estimating hood flowrate
A. Can measure the static pressure at some safer
or more easily reached location and use the
principles of duct resistance presented in this
lesson to estimate the air flow at a hood.
B. Recall from Lesson 1 the relationship for the
hood entry loss coefficient, C
e
ce = (vp/sph)°-5
or
SPh = VP/Ce2
Lesson 3 3-6 Duct Systems
-------
C. The hood static pressure could be determined by SLIDES AND
making a measurement anywhere in the duct NOTES
leading to the hood and then correcting the
measured value for the losses between the
measurement location and the hood. Assuming
losses due to both straight duct and fittings:
SPh = S^as ~ HfL'VP ' SF'VP
D. Equating the two relationships for hood static
pressure gives:
VP/Ce2 = SPmeas - HfL'VP - SF'VP
meas
or
VP = SPmeas/t1/^2 + HfL + SF)
E. To obtain Hf a trial velocity will have to be
assumed. The corresponding velocity pressure
would be compared to the calculated value and
the calculations repeated until reasonable
agreement is obtained.
F. Once an acceptable velocity pressure has been
determined, the flowrate can be calculated
from:
Q = VA = 1096.7A(VP/ra)°'5
or, if standard air is involved:
Q = 4005A(VP)°-5
V. Balancing duct systems 3-16
A. Balancing a branched duct system is the role of
the designer and is done to insure that the
correct air volumes are drawn from all hoods
that are connected to a common system. As
inspectors, it is important to have some
understanding of how this is accomplished and
the limitations of the various techniques.
B. The fundamental rule in balancing a duct system
is that all ducts entering a junction must have
equal static pressure requirements.
C. Consider the two-hood duct system shown. 3-17
At the junction, the static pressure in the
Lesson 3 3-7 Duct Systems
-------
longer duct that leads to Source 1 is 2.0 in. SLIDES AND
H20, while the static pressure in the duct NOTES
leading to Source 2 is 1.5 in. H2O. If nothing
is done, the system will adjust itself by
reducing the flowrate from Source 1 and
increasing the flowrate from Source 2 until the
same static pressure requirement results. To
prevent this situation, the designer must
adjust the resistances of each branch so that
they equal each other at the junction, while
maintaining design flowrates.
D. There are two techniques for obtaining static
pressure balance at a junction: 3-18
1. With dampers - inserting a damper into the
duct with the lower static pressure to raise
its value up to that of the other duct.
2. Through design - changes are made in duct
diameter, duct length, elbow radius, etc.,
or in the air volume in order to achieve
matching static pressures.
E. Characteristics of systems balanced through 3-19
design include:
1. Since the system resistance is fixed, air
volumes cannot be easily changed.
2. The system has limited flexibility for
future equipment changes or additions.
3. Because nothing protrudes into the gas
stream, there should be no unusual erosion
or accumulation problems.
4. Since balance may be achieved by making
small, but acceptable, changes in hood
volume, the total volume from a multiple
source system may be quite different than
the original design.
5. The system information must be detailed, so
that branch losses may be determined
accurately.
6. The system must be installed exactly as it
is designed. Any deviation will change the
resistance of a branch and the flowrates in
the system.
Lesson 3 3-8 Duct Systems
-------
F. Characteristics of systems balanced with SLIDES AND
dampers include: NOTES
1. Over a limited range, the air volumes may be 3-20
easily changed by changing the positions of
the dampers.
2. The system is flexible for future changes or
additions.
3. The damper may cause material accumulation
in the duct or may be eroded.
4. Since no volume changes are required for
balancing, the total volume will be the same
as the original design.
5. If balance is to be achieved by
trial-and-error, detailed system information
is not required, and branches that obviously
have lower resistance need not be
calculated. However, determining the branch
that has the greatest resistance is
critical.
6. Moderate variation from the design during
system installation is acceptable,
particularly if the system is to be balanced
by trial-and-error.
VI. Transport velocity 3-13
A. The velocity maintained within a duct segment
is referred to as the transport velocity.
1. For systems conveying vapors, gases or
smoke, the transport velocity chosen is a
compromise between fan energy cost and duct
cost - large diameter ducts result in lower
pressure losses and reduced fan energy but
cost more than smaller diameter ducts.
2. For systems handling particles, a transport
velocity is chosen to prevent settling. The
value of this velocity increases as the size
or density of the particles increases.
3. Typical values for transport velocity are
given in the table. 3-14
Lesson 3 3-9 Duct Systems
-------
B. There are several problems associated with the SLIDES AND
build-up of material inside ducts: NOTES
1. The resistance of the duct will increase due 3-15
to the reduction in effective flow area.
2. If the material is sticky or tends to form
solid cake, the deposition may continue
until the duct is completely plugged.
3. Deposition increases the weight of a duct
and may cause the duct system supports to
fail.
4. Hardened material deposited inside the duct
may break loose as a result of vibration and
travel down the duct to the fan or other
equipment, causing damage.
C. Inspecting for material build-up in a duct
system cannot be done effectively without
making measurements, since the accumulation is
not visible from the outside.
1. Measured static pressure differences between
locations along a duct could be compared to
expected values estimated using the
techniques described above.
2. Measurements of static pressure along a duct
could be plotted as a function of equivalent
length. If there are no obstructions, the
measurements will produce a straight line of
constant slope, with the values decreasing
(becoming more negative) in the direction of
gas flow.
D. Visual inspection points:
1. Another concern of particle conveying
systems is abrasion of the duct surf ace,-- a
potential that increases with increase in
transport velocity. This is a particular
problem wherever there is a change in
direction of the gas stream, such as at
elbows or entries. When material strikes
the duct walls, erosion can produce holes.
a. If the duct is under negative pressure,
air will enter the system through the
holes, reducing the amount of air that
enters at the hood, possibly causing loss
of capture efficiency.
Lesson 3 3-10 Duct Systems
-------
b. If the duct is under positive pressure, SLIDES AND
fugitive emissions may result as air NOTES
exits the holes. Also, segments that
have reduced air flow because of holes
may become susceptible to build-up
problems due to the loss of transport
velocity.
2. The best technique for locating holes in a
duct system is a visual inspection. To make
more effective use of inspection time, areas
on an elbow that are on the outside of the
turn, areas on a straight duct opposite
points of entry by other ducts, and areas
along the bottom of horizontal ducts should
be emphasized.
3. Somewhat related to transport velocity is
the problem of duct corrosion. As the gases
within a duct cool, condensation of moisture
and/or acidic material can occur. This
cooling may be the result of infiltration of
outside air or simply due to long residence
times in the duct, which can be exacerbated
by low transport velocities.
4. Physical damage to ducts can also increase
their resistance. A duct that has been
partially collapsed acts much the same as
a duct that has accumulated material.
Observations of physical damage should be
included in the visual inspection of a duct
system.
Lesson 3 3-11 Duct Systems
-------
PROBLEM SET 3
DUCT SYSTEMS
3-1. In the system shown below, a measurement of hood static
pressure in the 6 inch diameter duct at position A gives
1.9 inches of water. From position A back to the hood
there are 15 feet of straight duct and one 90° elbow
with R = 2D. Estimate the flowrate if the temperature
of the air stream is 70°F.
Solution
Assume a velocity of 3500 fpm
Fh = 0.5
Hf = 0.43 VP/ft
IF = 0.27
Ce = [!/(! + Fh) ]°'5 = 0.82
VP = S
- —
d/Ce2) + (HfL) + IF
1.9
I/(0.82)2+(0.0043)(15) + 0.27
= 0.7909 inches of water
V = 4005 (VP)0-5
4005 (0.7909)0'5
= 3562 fpm (checks with assumption
Q = 4005 A (VP)0-5
4005 (0.1963) (0.7909)0'5
699 acfm
Lesson 3 3-12 Duct Systems
-------
LESSON 4
GAS COOLING SYSTEMS
Goal:
To develop an understanding of gas cooling systems, their
design and performance characteristics, and techniques for
their evaluation.
Objectives:
At the end of this lesson the student should be able to:
1. State the three commonly used methods for cooling gases in
industrial ventilation systems.
2. Recognize the fundamental relationship governing the
performance of a dilution cooling system.
3. Use enthalpy and mass information to calculate air stream
volumes in a dilution cooling system.
4. State three problems associated with dilution cooling.
5. Recognize the fundamental relationship governing the
performance of an evaporative cooling system.
6. Use enthalpy and mass information to calculate the
theoretical water requirement in an evaporative cooling
system.
7. State three problems associated with evaporative cooling.
8. Recognize the fundamental relationship governing the
performance of a natural convection and radiation cooling
system.
9 - State four problems associated with natural convection and
radiation cooling.
10. Conduct effective inspections of gas cooling systems.
Lesson 4 Gas Cooling Systems
4-1
-------
List of Slides
4-1 Gas Cooling
4-2 Methods for cooling gases
4-3 Dilution with cooler gases
4-4 Problems with dilution cooling
4-5 Sulfuric acid dew-point curve
4-6 Quenching with water
4-7 Problems with quenching
4-8 Natural Convection and Radiation
4-9 Radiant Cooler
4-10 Problems with Convection and Radiation Cooling
Lesson 4 Gas Cooling Systems
4-2
-------
I. Introduction SLIDES AND
NOTES
A. Many processes generate gas streams at
temperatures that are too high for some air
pollution control devices to accept. Because
of this, it is necessary to employ some type of 4-1
cooling device to reduce gas temperature.
B. The most commonly used methods for cooling 4-2
gases in industrial ventilation systems are:
1. Dilution with ambient air
2 . Quenching with water
3 . Natural convention and radiation
C. In a limited number of cases, forced convection
systems using air or water for cooling, may be
encountered.
D. Cooling equipment will add to the resistance of
the system and may change the volume and
composition of the gases. If it is not
functioning properly, it can affect the
performance of other components in the system.
II. Dilution with ambient air 4-3
A. Cooling gases by dilution with ambient air is
the simplest method that can be employed. Hot
gases from a process are cooled by adding
ambient air in sufficient quantity to produce
a mixture with the desired temperature.
B. The fundamental relationship governing
performance may be developed through a heat
balance on the dilution system:
m1 = mass flowrate of hot gases
h1 = enthalpy of hot gases
m2 = mass flowrate of dilution air
h2 = enthalpy of dilution air
m3 = mass flowrate of gas mixture = m1 + m2
h3 = enthalpy of gas mixture
Lesson 4 Gas Cooling Systems
4-3
-------
C. Quantity and temperature of the hot gases and SLIDES AND
the desired temperature of the mixture are the NOTES
parameters that control the design. The
success of the design will depend on the
quantity of dilution air supplied in relation
to these parameters.
D. There are several potential problems with 4-4
dilution cooling:
1. Large air volumes may be required to
accomplish the desired temperature
reduction.
2. Problems with temperature control may also
be experienced if the quantity of dilution
air is not regulated.
3. When the temperature is not controlled, 4-5
corrosion problems are possible if acid or
moisture dew points are reached.
E. The inspection of a dilution cooling system is
rather straight-forward.
1. The system should be visually inspected to
evaluate the integrity of the system and to
determine if there are any indications of
corrosion problems.
2. If the temperature of the mixed gas stream
is being monitored, this value should be
noted and evaluated in terms of compati-
bility with downstream equipment,
particularly the control device, and with
regard to moisture or acid condensation
potential.
3. If controlled introduction of the dilution
air is employed, the condition of the
controller and the damper should .-be
evaluated and the set-point temperature
compared with any monitored values.
4. If temperature is not monitored,
measurements in the mixed gas stream may be
necessary to complete the evaluation.
Lesson 4 Gas Cooling Systems
4-4
-------
F. Measurements on a mixed gas stream that employs SLIDES AND
a branch duct to introduce the cooling air can NOTES
be used to estimate the volume of air coming
from the process and the volume used for
dilution.
1. Measure the volumetric flowrate and
temperature of the mixed stream and the
temperature of the hot gas stream and the
dilution air (usually ambient air).
2. Convert the volumetric flowrate of the
mixture to a mass flowrate using the density
corresponding to the measured temperature.
3. Determine the enthalpies of the three
streams based on their temperatures.
4. Substitute values into the heat balance
shown previously to determine the mass
flowrate of the hot gas and the dilution
air, as follows:
"hotpot + Kix ~ "Hiot) Dilution = mmixhmix
or
"W = mmix(hmix ~ hdi lution) / (hhot ~ ^dilution)
and
^dilution = ^mix ~ "W
5. Convert the mass flowrates to volumetric
flowrates using the densities corresponding
to their respective temperatures.
III. Quenching with water 4-6
A. When the volume of hot gases is large and the
amount of air needed to capture them is small,
some cooling method other than dilution with
ambient air is needed. Since evaporation of
water requires a large amount of heat, the gas
under these circumstances can be effectively
cooled by simply spraying water into the hot
gas stream.
Lesson 4 Gas Cooling Systems
4-5
-------
B. The fundamental relationship governing SLIDES AND
performance may be developed through a heat NOTES
balance on the evaporation system:
in
~ ngasout) = mwater (hwater vapor ~ hwater)
C. Again, the quantity and temperature of the hot
gases and the desired outlet temperature are
the parameters that control the design. The
success of the design will depend on the
quantity of water supplied in relation to these
parameters and the efficiency of its
evaporation.
D. There are several potential problems with
evaporative cooling: 4-7
1 . Water carry-over - degree of concern depends
on downstream equipment .
a. With wet scrubber systems, liquid
carry-over is not a concern, and the
efficiency of the evaporation equipment
need not be particularly high. The
evaporative cooler may be little more
than a series of spray nozzles mounted in
the duct leading to the scrubber.
b. In systems where water carry-over is a
concern, as in a fabric filter system, a
separate piece of equipment is likely to
be used for evaporative cooling. The gas
stream velocity will be significantly
reduced, and the liquid will be
introduced through spray nozzles at
pressures capable of producing a fine
spray. In some cases, air-atomized
nozzles may be used. These techniques
will likely be accompanied by an
elaborate control system.
2 . Corrosion - since the coolers utilize water
sprays, the potential for moisture and
condensed acid corrosion is significant,
particularly in systems where all of the
water is not evaporated. The designer
usually seeks to mitigate these problems
through the use of appropriate corrosion
resistant materials and linings.
Lesson 4 Gas Cooling Systems
4-6
-------
3. Temperature control - this can occur if the SLIDES AND
rate of water addition is not controlled or NOTES
if the control system is unable to respond
to the rate of change of the gas stream
temperature. Temperature control can also
be a problem if the water atomization is not
efficient.
Evaluation of an evaporative cooler:
1. A visual inspection to evaluate system
integrity and indications of corrosion
should be conducted.
2. If the outlet temperature is being
monitored, this value should be noted and
evaluated in terms of compatibility with
downstream equipment.
3. If temperature is not monitored, it may be
necessary to measure it; however, this
measurement may be complicated by the
presence of water droplets in the gas
stream.
4. A determination of the quantity of cooling
water used should be made. This could be
compared to calculated requirements.
a. Read the value indicated by a flowmeter
mounted on the delivery line or in the
control room.
b. Observe the delivery pressure on a gauge
mounted at the cooler or on the pump. To
be certain that any observed changes are
due only to a change in water flowrate,
the condition of the nozzles must also be
evaluated.
c. Plugged or eroded nozzles can --be
determined by observing the spray pattern
during operation.
5. The quality of recycled water should be
evaluated.
a. Water containing large particles would be
of concern because of the potential for
plugging or eroding the nozzles.
Lesson 4 Gas Cooling Systems
4-7
-------
b. If the water contains small particles, SLIDES AND
there would be concerns about passing NOTES
these more difficult to collect particles
on to the control device after the water
has been evaporated.
c. The quality of the water can be evaluated
by having plant personnel draw a sample
into a clear plastic container that you
provide. The sample should be well mixed
by shaking and then allowed to settle.
If the rate of settling is fairly rapid,
then the water contains large particles.
If the settling rate is very slow, the
water contains fine particles.
IV. Natural convection and radiation 4-8
A. Heat is transferred from a duct surface by
natural convection and radiation. This
behavior can be exploited to produce
significant amounts of cooling by providing a
section of duct that has large surface area.
B. The fundamental relationship governing the
performance of the cooler may again be
developed through a heat balance:
mgas(hgasin ~ hgas out) = UADTn,
U = overall heat transfer coefficient
A = heat transfer area
DTm = log-mean temperature difference
1. The overall heat transfer coefficient is a
function of a number of parameters,
including the duct diameter, the nature of
the duct surfaces, the thermal conductivity
of the metal, the velocity of the hot gases,
the wind speed, and the temper atuare
difference between the duct and the ambient
air.
2. The log-mean temperature difference is
simply a means of calculating an average
difference when that difference varies along
the length of the duct.
Lesson 4 Gas Cooling Systems
4-8
-------
C. Once again, the quantity and temperature of the SLIDES AND
hot gases and the desired outlet temperature NOTES
are the parameters that control the design. The
success of the design will depend on all the
parameters that affect the heat transfer
coefficient and on the total surface area
provided.
D. Large surface area is typically achieved by 4-9
arranging the duct in a series of vertical
columns. Since the velocities through the
columns are usually below the necessary
transport velocity for particles, the base of
alternate columns are joined across a hopper
for collection and removal of any settled dust.
E. There are a number of problems associated with 4-10
convection and radiation cooling systems.
1. The size of the cooler is usually quite
large, requiring significant amounts of
plant area for its installation.
2. Because the velocities in the cooler are
generally below the transport velocity for
particles, the system must be cleaned
continually to avoid build-up in the hopper
sections.
3. Because there is essentially no control on
the cooling process, it is not possible to
control the outlet temperature. This could
result in outlet temperatures that exceed
the limitations of downstream equipment or
that decrease into the range of moisture or
acid condensation.
F. Because of the nature of cooler design and
operation, the items that can be inspected on
these systems is limited.
1. The cooler should be visually inspected to
evaluate the integrity of the system and to
determine if there are any indications of
corrosion problems.
2. If the temperature of the outlet gas stream
is being monitored, this value should be
noted and evaluated in terms of compatibil-
ity with downstream equipment and with
regard to moisture or acid condensation
potential.
Lesson 4 Gas Cooling Systems
4-9
-------
3. If temperature is not monitored,
measurements in the outlet gas stream may be
necessary to complete the evaluation.
Lesson 4 Gas Cooling Systems
4-10
-------
Problem Set 4
Gas Cooling Systems
4-1. Ducts from a hot process and an overhead canopy hood join
before going into a fabric filter collector. Measurements
just downstream of the junction give an air volume of
20,188 acfm at 250 °F. Measurements in the hot duct give a
temperature of 3,000 °F and the plant air is estimated at
100 °F. What are the actual air volumes being drawn from the
process and the canopy hood?
Solution
m3 = (20,188 ft3/min) (0.0558 lb/ft3) = 1126.5 Ib/min
m1(802.3) + (1126.5 - m1)(9.6) = (1126. 5) (45.7)
m1 = 51.3 Ib/min
£3000 = />2000 (2460/3460)
= 0.0161(0.71) = 0.0114 lb/ft3
Q1 = 51.3/0.0114 = 4,5000 acfm
m2 = 1075.2 Ib/min
Q, = 1075.2/(0.0708) = 15,186 acfm
Lesson 4 Gas Cooling Systems
4-11
-------
4-2. A cupola furnace emits 300 Ib/min of gases at 2,250 °F,
Assuming 100 percent utilization, how much water at
60 °F is required to cool the gas stream to 350 °F?
Solution
Air:
Ah
581.6
70.0
511.6 Btu/lb
Water:
h350
h60
Ah
A
V
131.
0.
131.
= 1059.
3
0
3
9
Ah
tot
= 1191.2 Btu/lb
mw =
[(300)(511.6)] Btu/lb
(1191.2) Btu/lb
128.8 Ib/min
(128.8 Ib/min / 62.4 lb/ft3) (7.48 gal/ft3)
15.4 gal/min
Lesson 4
4-12
Gas Cooling Systems
-------
LESSON 5
FAN SYSTEMS
Goal:
To develop an understanding of fan systems, their design and
performance characteristics, and techniques for their evaluation,
Objectives:
At the end of this lesson the student should be able to:
1. Discuss the advantages and disadvantages of forced draft
and induced draft fan systems.
2. State the two classes of fan types used in industrial
ventilation systems.
3. List three types of axial fans and describe their
performance characteristics.
4. List five types of centrifugal fans and describe their
performance characteristics.
5. Describe three common fan arrangements.
6. State the fan laws for a homologous series of fans and
know how to apply them to fan inspection.
7. Discuss how fan curves and system curves interact to
determine the air volume delivered.
8. Discuss how changing system resistance affects fan
performance.
9. Discuss how changing fan speed affects fan performance.
10. Discuss how changing air density affects fan performance.
11. Define "system effect" as it relates to fan performance.
12. Estimate losses associated with system effects at the
inlet and outlet of a fan.
13. State the procedures involved in fan selection and know
how to apply them to fan inspections.
14. Describe how an amperage control system works during fan
start-up.
15. Conduct effective inspections of fan systems.
Lesson 5 5-1 Fan Systems
-------
List of Slides
5-1 Fan systems
5-2 Forced-draft induced draft fan arrangements
5-3 Types of fans
5-4 Axial fans
5-5 Centrifugal fan components
5-6 Types of Centrifugal fans
5-7 Forward curved fan
5-8 Forward curved fan performance chart
5-9 Radial fan
5-10 Radial fan performance chart
5-11 Backward inclined fan - standard blade
5-12 Standard backward inclined fan performance chart
5-13 Arrangement 1 SWSI
5-14 Fan laws
5-15 System curves
5-16 Interaction of systems curves with fan curve
5-17 Changes in fan rotation speed
5-18 Effect of air density on fan performance
5-19 System effects
5-20 Fan selection
5-21 Fan selection
Lesson 5 5-2 Fan Systems
-------
I. Introduction SLIDES AND
NOTES
A. The function of a fan is to cause the desired
amount of air to move through a system by 5-1
overcoming resistances in the hoods, ducts,
coolers, collection devices, stacks and any
other equipment present.
B. Fan performance depends on the type of fan
employed, the parameters of its operation, the
characteristics of the system it is used in,
and the properties of the gas stream it
operates on.
C. A fan can be generally characterized on the 5-2
basis of its location in the ventilation system
with respect to the control device.
1. Fans located before the control device are
referred to as forced draft because they
force or push the air through the collector
a. Fan acts on the dirty gas stream and may
be subject to increased wear and require
a higher level of maintenance, thereby
increasing operating costs.
b. Control device will only have to
withstand the pressure required to push
the gas stream through the device and on
to the stack. As a result, the collector
will require less structural reinforcing
and will likely be somewhat cheaper.
2. Fans located after the control device are
referred to as induced draft because they
induce or pull the flow through the
collector.
a. Fan acts on the cleaned gas stream and
would be less subject to wear. Thds
would likely require a lower level of
maintenance, reducing operating costs.
b. Control device will have to be
structurally reinforced to withstand
essentially the entire negative pressure
of the system and will probably be more
expensive.
Lesson 5 5-3 Fan Systems
-------
II. Types of fans SLIDES AND
NOTES
A. Fans designs can be classified as either axial
or centrifugal. A special class of fan that 5-3
employs a centrifugal wheel mounted in an axial
arrangement will sometimes be encountered in
industrial ventilation systems.
B. Axial fans are used to move large volumes of
air against low resistances. They may be used
for general ventilation or in low resistance
industrial ventilation systems; however, they
are not used very often in air pollution
control systems.
C. There are three basic types of axial fans: 5-4
1. Propeller - used for moving air against very
low static pressures, such as would be
encountered in general room ventilation.
Their performance is very sensitive to
resistance and a small increase will cause
a significant reduction in flow.
2. Tubeaxial - essentially a propeller-type fan
mounted in a cylindrical housing and capable
of moving air against pressures less than
about 2 in. H2O. Since the motor is
typically mounted inside the housing, it is
not generally used on particle-containing
gas streams.
3. Vaneaxial - similar in construction to
tubeaxial, but uses airfoil-style blades and
straightening vanes on the inlet and outlet
to improve efficiency. It is capable of
developing pressures up to about 8 in. H2O
and should also be limited to clean
applications.
D. The principal fan used in air pollution control 5-5
systems is the centrifugal fan. The basic
design of the centrifugal fan employs a fan
wheel or impeller mounted inside a scroll-type
housing. Air is draw into the impeller and
then forced out through the housing.
E. Centrifugal fans are distinguished by the 5-6
design of the impeller. There are three basic
impeller types: (1) forward curved, (2) radial
and (3) backward inclined. The backward
inclined impeller may use a standard
single-thickness blade or an airfoil blade.
Lesson 5 5-4
Fan Systems
-------
F. Forward curved impellers have blades that curve SLIDES AND
into the direction of rotation. NOTES
1. Commonly referred to as "squirrel-cage 5-7
blowers", they are constructed of
lightweight materials and usually have 24 to
64 closely-spaced blades.
2. For a given duty, these impellers are the
smallest of all the centrifugal types and
operate at the lowest speeds.
3. They are quiet in operation but are only
able to develop low to moderate static
pressures. Therefore, they are not commonly
used in air pollution control systems.
4. Since particles may adhere to the
closely-spaced blades and cause a balance
problem, their use should be limited to
clean gas streams.
5. The highest mechanical efficiency (ME) is 5-8
developed at a point to the right of peak
static pressure (SP), at about 50-60 percent
of the wide open volume, and the horsepower
requirement (HP) rises continually toward
the free delivery volume.
G. Radial impellers have 6 to 10 blades that 5-9
extend either straight out from the hub (R) or
in a radial direction (M).
1. They are the simplest of all the centrifugal
fans and the least efficient, but they are
capable of developing the highest static
pressures.
2. For a given duty, they operate at moderate
speeds.
3. The radial blade shape is generally
resistant to material build-up and may be
used in systems handling either clean or
dirty air. Impeller designs, range from
"high efficiency, minimum material" to
"heavy impact resistant".
4. Highest mechanical efficiency is developed 5-10
just to the left of peak static pressure, at
about 30-40 percent of the wide open volume
and the horsepower requirement again rises
continually toward the free delivery volume.
Lesson 5 5-5 Fan Systems
-------
H. The standard backward inclined impellers have SLIDES AND
9 to 16 single-thickness blades that incline or NOTES
curve away from the direction of rotation.
5-11
1. Peak efficiency and speed are slightly less
than the airfoil design.
5-11
2. Because the blades are single thickness,
they can be used in gas streams with light
dust loadings. However,they should not be
used in heavy loading situations that could
cause build-up on the blade surfaces.
3. Highest mechanical efficiency is developed 5-12
to the right of peak static pressure, at
about 50-60 percent of the wide open volume.
A unique characteristic of the backward
inclined impeller is that the horsepower
requirement reaches a maximum value near the
point of peak efficiency and then declines
toward the free delivery volume. For this
reason backward inclined fans are sometimes
referred to as "non-overloading", since any
variation from the optimum operating point
due to a change in system resistance will
result in a reduction in operating
horsepower.
I. The airfoil backward inclined impellers have 9
to 16 hollow airfoil-style blades that incline
or curve away from the direction of rotation.
1. They have the highest efficiency of all the
centrifugal fans and, for a given duty, will
operate at the highest speed.
2. Hollow blades can erode and accumulate
material inside, causing a balance problem.
They should, therefore, be limited to clean
air applications.
3. Highest mechanical efficiency is developed
to the right of peak static pressure, at
about 50-60 percent of the wide open volume.
The horsepower requirement exhibits a
non-overloading characteristic.
Lesson 5 5-6 Fan Systems
-------
J. The tubular centrifugal fan employs a centirif-
ugal wheel mounted in an axial arrangement.
The impeller design is usually backward
inclined but, although it has the same general
performance characteristics and limitations, is
somewhat less efficient. It also has lower
capacity and static pressure capabilities
because of the 90 degree change in direction
that occurs as the air moves through the
housing.
SLIDES AND
NOTES
III. Fan arrangements
A. Fans are constructed with different bearing
locations and motor mounting capabilities,
generally referred to as "arrangements".
Although these are not of any particular
importance to the inspection task, knowledge of
the various arrangements is desirable when it
is useful to speak the language of fan systems.
B. There are ten basic fan arrangements [refer
students to Figure 5-9 in Student Manual, p.
5-8J. SW or DW refers to single- or
double-width fans, respectively. SI and DI
refer to single- or double-inlet, respectively.
C. The most common fan arrangements employed are
Arrangements 1, 3 and 9.
1. Arrangement 1 has two shaft bearings mounted
on the pedestal with the impeller overhung
on the end of the shaft. For a V-belt
drive, the motor would be mounted on a
separate base adjacent to the pedestal and
at ground level, with pulleys or sheaves on
both the motor shaft and the fan shaft. For
direct drive, the motor would be mounted on
a separate base and connected directly to
the shaft, or on an extended fan base as -in
Arrangement 8.
2. Arrangement 3 also has two shaft bearings,
but they are located on either side of the
impeller and supported by the fan housing.
The drive arrangement would be the same as
Arrangement 1.
3. Arrangement 9 is the same as Arrangement 1,
but has the motor mounted on the outside of
the fan base with a V-belt drive system.
5-13
Lesson 5
5-7
Fan Systems
-------
D. Fans driven by V-belts will have an effective SLIDES AND
horsepower that is less than that provided by NOTES
the motor because of drive losses.
IV. Fan Laws
A. The fan laws relate the performance variables
for any homologous series of fans. A 5-14
homologous series is simply a range of fan
sizes where all of the dimensional parameters
are proportional.
B. At the same relative point of operation on any
two performance curves in a homologous series,
the mechanical efficiencies will be equal.
Under these conditions, the following
relationships apply:
Q2 = Q1(size2/size1)3(rpm2/rpm1)
P2 = P1(size2/size1)2(rpm2/rpm1)2(r2/r1)
bhp2 = bhp1(size2/size1)5(rpm2/rpm1)3(r2/r1)
The pressure may be represented by total
pressure, static pressure, velocity pressure,
fan total pressure or fan static pressure.
C. These expressions rely on the performance
curves being homologous and apply only at the
same relative point of rating. Under turbulent
flow, two performance conditions will be at the
same relative point of rating if the pressures
and flowrates at these two conditions are
related by:
This is the same as saying that the two
performance points must lie along the same
system curve.
Lesson 5 5-8 Fan Systems
-------
D. Fan laws are typically used to determine the SLIDES AND
effect of changing only one variable at a time NOTES
and are most often applied to a single fan
size. The most common variable of interest is
fan speed. For determining the effect of
changing fan speed while operating on the same
gas stream (r1 = r2) , the fan laws become:
Q2 = Q
P2 = P
bhp2 = bhp1(rpm2/rpm1)3
E. Note that if only changes in gas density are
involved, pressure capabilities and power
requirements change proportionally, while
flowrate is unaffected. This behavior is
sometimes characterized by stating that "a fan
is a constant volume machine", i.e., it moves
volumes of air not masses of air.
V. Fan performance
A. Performance graphs for centrifugal fans were
shown earlier. One of the relationships shown
on these figures was that between pressure
developed and air volume moved [draw repre-
sentation on board]. This relationship is
referred to as the fan curve or fan char-
acteristic. For a particular fan turning at a
given rpm, there is one and only one fan curve.
It represents all of the pressure/air volume
combinations that the fan is capable of when
operating at that one rpm. These range from
low air flow delivered against high pressure
(upper left) to high air flow delivered against
low pressure (lower right). What determines
which condition a fan will operate at is how
this curve interacts with the ventilation
system characteristics, as represented by the
system curve.
B. Normalized duct system curves for three systems 5-15
are shown in this figure. Plotted here is the
percentage of duct system resistance as a
function of the percent of duct system
flowrate. This is simply a normalized version
of a P verses Q plot. The system curves shown
follow the general relationship characteristic
of turbulent systems:
Lesson 5 5-9 Fan Systems
-------
P - P (O /O )2 SLIDES AND
p2 - P^QZ/QI) NOTES
1. In practice, the system curve is developed
by first determining the resistance or
static pressure for one flowrate through the
system, using the techniques discussed in
Lessons 2 and 3. Other points on the curve
are then determined using the above
relationship.
2. If the design point for System A were at 100
percent volume and 100 percent resistance,
increasing the flowrate to 120 percent of
the design flow would increase the
resistance to 144 percent of the design
resistance.
3. Likewise, decreasing the flowrate to 50
percent of the design value would decrease
the resistance to 25 percent of the design
resistance. Note that, on a percentage
basis, the same relationships also hold for
Systems B and C.
C. The point of intersection of the system curve 5-16
with the fan curve determines the actual fan
performance. This is shown in this figure,
where a normalized fan curve has been plotted
with the system curves from the previous
figure. Unless actions are taken to change
either the fan curve or the system curve, the
performance delivered will be that indicated by
the intersection point.
D. One way to change the f lowrate would be to
change the system. This could be done by
closing or opening a damper, producing a system
with more or less resistance and changing the
system curve.
1. Referring to the same figure, the flowrate
could be decreased to 80 percent of the
design volume by closing a damper until the
more resistant System B curved is obtained,
shifting the intersection to Point 2.
2. Likewise, the flowrate could be increased to
120 percent of the design value by opening
the damper and shifting the intersection to
Point 3.
Lesson 5 5-10 Fan Systems
-------
E. Changes in flowrate could also be produced by SLIDES AND
changing the fan speed, shifting the fan curve. NOTES
This is illustrated in this figure, where a new
fan curve representing a 10 percent increase in 5-17
speed has been added. At this new speed, the
point of operation shifts to Point 2.
1. Since flowrate is proportional to fan speed,
this 10 percent increase in speed produces
a corresponding 10 percent increase in
volume.
2. However, following the fan laws, this 10
percent increase in speed will reguire a 33
percent increase in operating horsepower,
which may be beyond the capabilities of the
existing motor.
F. According to the fan laws, changing gas density 5-18
will shift the fan curve. However, since gas
density also affects the system resistance, the
system curve will also be shifted. This is
illustrated in this figure for a doubling of
the density. The new operating point will
deliver the same air volume but at double the
resistance and double the horsepower
requirement.
G. Fan performance can also be affected by the
manner in which the fan is installed in the
system. Ratings information is developed in a
test set-up that insures consistency and
reproducibility of results and permits the fan
to develop its maximum performance. In any
installation where uniform flow conditions do
not exist, fan performance will be reduced.
1. Installation conditions that affect fan 5-19
performance are referred to as "system
effects". The three most common causes of
deficient performance are:
a. Non-uniform inlet flow
b. Swirl at the fan inlet
c. Improper outlet connections
Lesson 5 5-11 Fan Systems
-------
2. The influence of system effects on fan SLIDES AND
performance is shown in this figure. NOTES
a. The solid fan curve has been determined
without consideration of system effects
and performance corresponding to Point 1
is anticipated.
b. Because of system effects the effective
fan curve is the dashed line and
performance corresponding to Point 3 is
obtained.
c. This deficient performance could be
prevented by calculating the system
effect loss, adding it to the system
resistance and selecting a fan to operate
at Point 2.
3. Refer students to Figures 5-15 through 5-17
in Student Manual, pp. 5-14 through 5-16,
for system effect loss factors for some
common installation conditions. These
factors are in numbers of velocity pressures
lost, so the addition to the system static
pressure would be egual to the loss factor
times the appropriate velocity pressure.
VI. Fan selection
A. Selecting a fan is usually the responsibility
of the ventilation system designer. However,
since the inspector may wish to apply
variations of the selection technique in
evaluating the performance of an existing fan,
it is important that the methods used by the
designer be understood.
B. Fan selection is typically done using ratings
tables published by manufacturers for their
products.
1. The ratings table is entered along the row
corresponding to the design volume and down
the column corresponding to the design
static pressure, including system effects.
Lesson 5 5-12 Fan Systems
-------
2. The point of intersection indicates the rpm SLIDES AND
that the fan would have to turn to deliver NOTES
the required performance and the horsepower
that would be needed to drive it.
3. Shaded regions are usually included on the
chart to indicate areas of good mechanical
efficiency.
4. Ratings tables indicate the performance of
a fan when operating on standard air. Since
a given system may be handling air of a
different density, some adjustments are
involved before entering the table.
Remember, density does not affect fan
volume, but it does influence static
pressure conditions and horsepower
requirements.
C. The specific procedure involved in fan
selection is as follows: 5-20
1. Determine the design air volume at actual
conditions.
2. Calculate the fan static pressure at actual
conditions, including system effects. Fan
static pressure is defined as:
FSP = SPout - SPin - VPin
In calculating fan static pressure, the sign
of the static pressure is important and must
be included.
3. Correct the fan static pressure to an
equivalent value for standard air:
^equivalent = FSPactual < ° • 075/r8ctual)
4. Enter the ratings table at the actual volume 5-21
and the equivalent fan static pressure.
Determine the rpm and horsepower
requirements.
5. Correct the horsepower requirement to the
conditions of actual operation:
bhPactual = ^equivalent
Lesson 5 5-13 Fan Systems
-------
D. In selecting the appropriate motor for a fan,
the designer must give consideration to the
possible air densities the fan may have to
handle. Should the system be located outdoors
in an area that has extreme low temperatures,
the horsepower requirement for cold start-up
could be considerable.
E. An alternate way of dealing with cold start-up
would be to install the horsepower required for
normal operation and then use an inlet or
outlet damper, together with an amperage
control system, during start-up.
1. When the fan is started on cold air, the
amperage control system would sense a high
current flow and close the damper to prevent
or reduce air flow into the fan.
2. The fan turning through the restricted air
flow would heat it up, reducing its density
and reducing the current draw. The amperage
control system would sense this and open the
damper a little bit to allow some air flow
from the hot process.
3. This scenario would continue until the
damper was fully open and the system was
operating at design conditions.
VII. Evaluation of fan performance
A. The fan laws and the techniques involved in fan
selection may be used by the inspector to
estimate the air volume the fan is delivering.
For example, if the air volume delivered by an
existing fan were known, but a subsequent
inspection determined that the fan speed had
been changed, the new air volume could be
estimated from:
the
requ ired
volume
when
turned at
the
SLIDES AND
NOTES
Q2 =
B. Initial estimates of air volume could be made
using measurements of the fan operating
parameters, together with the appropriate
ratings table.
1. This approach would apply only to V-belt or
variable-speed drive fans, for which general
ratings tables are available. Direct drive
fans are specially constructed to deliver
Lesson 5
5-14
Fan Systems
-------
speed of the motor and do not have published SLIDES AND
performance tables. NOTES
2. Because of our inability to make exact
measurements of some of the parameters and
because of a lack of precision in the
ratings tables, these techniques will yield
only a rough estimate of flowrate.
The most satisfactory technique for estimating
fan performance from the ratings tables would
be to use measurements of fan speed and fan
static pressure. The specific procedure is as
follows:
1. Measure or estimate fan rpm. To obtain as
much accuracy as possible, measurement of
the rpm is preferred. However, if this is
not possible, an estimate can be used.
2. Determine fan static pressure for operation
on standard air. This would involve
measuring inlet and outlet static pressures
and estimating inlet velocity pressure.
a. To avoid turbulence problems, the
measurements could be made some distance
away from the fan, where acceptable
readings can be obtained. If measure-
ments are made at about the same
equivalent length away from the inlet and
outlet, the error introduced by this
should be minimal.
b. If inlet or outlet dampers are present,
the loss introduced by these fittings
would have to be estimated and included
in the determination of the respective
static pressure. Likewise, any losses
due to system effects should be included.
c. Air density could be estimated from a
measurement of temperature, and velocity
pressure could be estimated based on the
expected velocity at the inlet.
The estimated fan static pressure would
then be given by:
= 0.075(8?^ - SPin -
VPin)/ractuat
Lesson 5 5-15 Fan Systems
-------
3. Enter the ratings table for the fan at the SLIDES AND
column corresponding to the estimated fan NOTES
static pressure. Proceed down this column
until the row containing the measured fan
speed is located. Read along this row to
determine the estimated flowrate.
Interpolation between values in the ratings
table may be necessary.
4. If the air volume determined from this
procedure gives a significantly different
velocity pressure than that assumed in Step
2, the velocity pressure should be
re-estimated and the procedure repeated
until a reasonable agreement is obtained.
D. A less satisfactory technique for estimating
fan performance from the ratings tables would
be to use measurements of fan static pressure
and operating horsepower.
1. Following the same general procedures
outlined above, the fan static pressure
would be estimated and used to enter the
ratings table.
2. The row corresponding to the estimated
operating horsepower would then be located
and used to determine the estimated
flowrate.
E. The fan inspection should include an evaluation
of the condition of the fan.
1. A visual determination of the condition of
the fan housing to assess any indications of
corrosion.
2. An evaluation of the condition of the
isolation sleeves used to dampen vibration
between the fan and the inlet and outlet
ducts to determine if there are any leaks.
3. An evaluation of any vibration or belt
squeal.
a. Belt squeal during operation indicates
that the belts are slipping on the
pulleys. This can result in the loss of
200-300 rpm, with a corresponding
loss in air volume.
Lesson 5 5-16 Fan Systems
-------
b. A fan that is vibrating severely
represents a significant safety hazard.
If this condition should be
encountered, the inspection should be
terminated immediately and plant
personnel notified of the condition.
4. Confirmation of the fan rotation direction.
5. If the fan is not operating, an inspection
of the condition of the fan wheel would also
be useful to identify any build-up or
corrosion problems.
Lesson 5 5-17 Fan Systems
-------
PROBLEM SET 5
FAN SYSTEMS
5-1. A fan with a 20 inch diameter inlet duct is exhausting
8,000 acfm at 150 °F. The inlet static pressure is
-4.35 inches of water and the outlet static pressure
is 0.55 inches of water. What is the actual fan static
pressure? What is the fan static pressure at 70 °F?
Solution
(w/4) (20/12)'
2.182 ft2
V
8000/2.182
3666.4 fpm
VP = 0.0651 (3666.4/1096.7)2
FSP150 = 0.55 - (-4.35) - 0.73
= 4.17 inches of water
FSP70 = 4.17 (610/530)
= 4.80 inches of water
0.73 inches of
water
Lesson 5
5-18
Fan Systems
-------
5-2. A fan is delivering 10,500 acfm at 3.0 inches of water fan
static pressure when running at 400 rpm and using 16.2
horsepower. If the fan speed is increased to 500 rpm,
determine the new flowrate, fan static pressure and
horsepower requirement.
Solution
Q2 = 10,500 (500/400)
13,125 acfm
FSP2 = 3.0 (500/400)2
= 4.69 inches of water
bhp2 = 16.2 (500/400)3
= 31.64 horsepower
Lesson 5 5-19 Fan Systems
-------
5-3. A fan is needed to deliver 5,800 acfm at 200 °F. The fan
static pressure at operating conditions is estimated at
6.0 inches of water. For what conditions must the fan be
selected from the ratings tables?
Solution
FSP7Q = 6.0 (660/530)
= 7.47 inches of water
Select fan for 5,800 cfm and 7.47 inches of water
Lesson 5 5-20
Fan Systems
-------
5-4. in the system shown below, actual gas temperature is
150 °F. Form "A" to the elbow at the fan inlet is
20 feet, and from the fan outlet to the discharge elbow
is 8 feet. Both inlet and outlet ducts are 58 inches
diameter and both elbows have an R=1.5D. Using the ratings
table below, estimate the air volume if the fan speed is
1,050 rpm.
Solution
Assume a velocity of 3,500 fpm
VP = (3500/4500)2 = 0.76 inches of water
IN
Straight duct =
Elbow =
(0.0021) (20) (0.76) = 0.041 in. water
(0.39)(0.76) = 0.296 in. water
System effect = (1.1)(0.76)
= 0.836 in. water
-11.173 in. water
OUT
Straight duct =
Elbow =
System effect =
(0.0027) (8) (0.76) = 0.016 in. water
(0.39)(0.76) = 0.296 in. water
(0.33) (0.76) = 0.251 in. water
SP
out
0.563 in. water
FSP = 0.563 - (-11.173) - 0.76
= 10.976 inches of water
Approximate FSP as 11.0 inches of water
Lesson 5
5-21
Fan Systems
-------
Interpolation at 1050 rpm gives a volume of 61,813
acfm.
V = 61,813/[(7T/4) (58/12)2]
3,369 fpm
Fairly close to assumption - could estimate velocity
as 3400 fpm and repeat.
Lesson 5 5-22
Fan Systems
-------
LESSON 6
MEASUREMENT OF VENTILATION SYSTEM
PARAMETERS
Goal:
To develop an understanding of the equipment and procedures for the
measurement of ventilation system performance parameters and the
limitations of the techniques.
Objectives:
At the end of this lesson the student should be able to:
1. Select the proper size port for ventilation system
measurements.
2. Effectively seal a port while measurements are being made.
3. Select, calibrate and operate equipment for making static
pressure measurements.
4. Select, calibrate and operate equipment for making
temperature measurements.
5. Determine the number and location of traverse points needed
for a representative measurement of flowrate.
6. Select, calibrate and operate equipment for making flowrate
measurements.
7. State three techniques for measuring face velocity at hoods.
8. State three techniques for measuring fan speed.
9. Make an estimate of fan speed for fans with a V-belt drive.
10. Describe a procedure for determining 'the operating
horsepower of a fan.
11. Describe two techniques for estimating fan operating
horsepower.
12. Determine when measurement probes should be grounded and how
to accomplish it.
Lesson 6 6-1 Measurement
-------
List of Slides
6-1 Measurement of ventilation system parameters
6-2 Measurement ports for portable inspection equipment
6-3 Large stack-sampling port
6-4 Small measurement port
6-5 Differential pressure transmitter and port
6-6 Plugged port
6-7 Plugged elbow
6-8 Plugged port
6-9 Measurement of pressure
6-10 Aspiration effect error in static pressure measurement
6-11 Slack tube manometer
6-12 Static pressure gauges
6-13 Static pressure gauges
6-14 Techniques for the measurement of temperature
6-15 Thermocouple calibration recommendations
6-16 Temperature measurement errors
6-17 Thermocouple support techniques
6-18 Air infiltration error in temperature measurement
6-19 Effect of water droplets on temperature measurement
6-20 Measurement of gas flowrate
6-21 Gas flowrate EPA Reference Methods
6-22 Complete sampling train for gas flowrate measurements
6-23 Types of pitot tubes
6-24 Pitot tube coefficients
6-25 Number of sampling points required
6-26 Locations of sampling points required
6-27 Locations of sampling points required
6-28 Checking for cyclonic flow
6-29 Measurement of fan speed
6-30 Checking sheave diameters
6-31 Checking fan speed using sheave diameters
6-32 Horsepower measurement
6-33 Estimating horsepower from amperage measurements
6-34 Grounding cables
Lesson 6 6-2 Measurement
-------
I. Introduction SLIDES AND
NOTES
A. In previous lessons, the use of various
parameters to evaluate the performance of
ventilation system components has been 6-1
suggested.
B. In this lesson, the methods available for 6-1
making these measurements will be discussed and
recommendations on the most appropriate
techniques and procedures will be made. Where
appropriate, additional techniques for
estimating some parameters will be given.
II. Measurement ports 6-2
A. The most likely port to be found initially on
a ventilation system is a 3 or 4 inch diameter
sampling port located on or near the stack.
Although a port in this location may be useful 6-3
for some inspection measurements, ports of this
size should, in general, be avoided.
1. Difficult to sealing under both positive and
negative conditions
2. May be difficult to open because of the
large thread area.
B. The most useful port size for inspections is 6-4
l%-2 inch diameter, and this size is needed
only if measurements of velocity pressure are
anticipated. For the more routine measurements
of temperature and static pressure, ports of
%-% inch will accommodate most measurement
probes.
C. Permanently installed static pressure lines
should be avoided by the inspector. Plant 6-5
personnel will be needed to disconnect thefri,
only static pressure information can be
obtained from them, and it is difficult to
insure that the lines are clear.
D. Measurement ports are subject to the 6-6,
accumulation of material that may cause them to 6-7,
become plugged, even if they are on the clean and
side of the control device. Before using any 6-8
port, it should be cleaned out with a
non-sparking rod to assure unobstructed access
to the gas stream.
Lesson 6 6-3 Measurement
-------
Never open a port that was not placed there for SLIDES AND
your exclusive use. Plant monitoring ports may NOTES
be connected to controllers that initiate
equipment shut-down if the signal from them is
lost.
Because of the potential for fire or explosion
from sparks and because of possible damage to
downstream equipment, the inspector should not
request that ports be installed while the
equipment is running. Rather, the locations
and sizes needed should be marked for plant
personnel, so that they may install them the
next time the system is shut down.
The inspector should not make heroic efforts to
reach existing ports and should not have ports
installed in locations that cannot be reached
and used in safety. This should include
consideration of hazards to walking and
climbing, as well as the potential for exposure
to inhalation, vision, hearing and fire and
burn hazards.
III. Static pressure measurement
6-9
A. There are two widely used techniques for
sensing static pressures:
1. U-tube manometer
2. Magnehelic differential pressure gauge
B. The U-tube manometer is a reference instrument
that is available in a flexible or slack-tube
configuration to enhance its portability. The
manometer is equipped with magnets at the top
and bottom to facilitate temporary mounting and
is equipped with threaded connectors that are
used to seal the manometer during transport~
6-11
1. The manometer indicates the static pressure
by displacing the fluid in the tube. In
making static pressure measurements, one leg
of the manometer is connected to the probe
and the other is left open to the
atmosphere. The height difference between
the levels in the two columns is the
pressure in height of fluid, usually
expressed in inches of water.
Lesson 6 6-4 Measurement
-------
2. One of the principal difficulties with the SLIDES AND
U-tube manometer relates to the fluid. If NOTES
the pressure in the duct exceeds the
capacity of the manometer, fluid will either
be drawn into the duct or blown out onto the
inspector.
3. The inspector must remember to close the
seals when transporting the manometer to
prevent loss of fluid and to open them
before making a measurement.
C. The Magnehelic pressure gauge is a product of 6-12
Dwyer Instruments, Inc. It senses pressure
difference by deflecting a silicone rubber
diaphragm and then translating that deflection
to a needle indication through a magnetic
linkage. Although not as accurate as the
U-tube manometer, it is much more forgiving,
making it easier to use in field situations.
1. The Magnehelic is accurate to within 2
percent of full scale and has a high
resistance to shock and vibration. It is
available in over 70 ranges, from 0-0.25 in.
H2O to 0-20 psig. The most useful ranges for
ventilation system inspection are 0-5, 0-20
and 0-50 in. H20.
2. Except for the 0-0.25 and 0-0.50 in. H2O 6-13
ranges, the magnehelic may be used in any
orientation and can accept pressures up to
15 psig without being harmed. This property
allows gauges with different ranges to be
combined in one instrument package.
3. Because of the silicone rubber diaphragm,
the ambient temperature range is limited to
20° to 140°F. This lower limitation can be
accommodated when conducting inspections in
cold environments by keeping the gauge in- a
location that is within the range and then
taking it out briefly for making the
measurement.
D. The Magnehelic is not a reference instrument,
so its calibration should be checked
periodically.
1. The simplest way of doing this is to check
its indications against a U-tube manometer.
Lesson 6 6-5 Measurement
-------
Using a laboratory squeeze-bulb equipped SLIDES AND
with check valves, pressures from -40 to +40 NOTES
in. H20 can be easily generated.
2. The Magnehelic indications should be plotted
against those of the manometer to check for
accuracy and linearity- Gauges that give
inaccurate or non-linear indications should
be discarded.
3. While using the gauge, its zero should be
checked frequently and adjusted as needed
using the set-screw on the front plate.
Adjusting the zero will not affect the
calibration of the gauge.
E. Static pressure measurements must be made with
a square-ended probe placed at a right-angle to
the flow direction. The purpose of the probe
orientation is to be sure that no component of
velocity pressure is impacting the probe
during static pressure measurements.
F. The area between the probe and the port opening
should be sealed to avoid errors associated
with flow into or out of the duct. Errors
resulting from improper sealing can be as large
as 10-30 percent. 6-10
1. Flow into the duct can result in an
aspiration effect at the end of the probe
that can increase (make more negative) the
negative pressures being measured.
2. Flow out of the duct can add a component of
velocity pressure to the measurement of
positive pressures.
G. Several techniques are available for sealing
measurement ports.
1. For inspection ports, the best sealing
technique is to insert the probe through a
rubber stopper and then place that stopper
into or against the port.
2. For the larger stack-sampling ports, a
rubber sanding disc may be used to cover the
opening. The probe, equipped with a rubber
stopper, would then be inserted through the
center of the sanding disc, using the
stopper to complete the seal.
Lesson 6 6-6 Measurement
-------
H. To further mitigate port sealing problems, the SLIDES AND
probe should be extended well into the duct NOTES
while making measurements.
IV. Temperature measurement 6-14
A. There are several techniques available for
measuring temperature, including: (1) mercury
thermometers, (2) dial thermometers,
(3) thermistors and (4) thermocouples.
Unfortunately, each of these techniques has
some limitation when applied to the inspection
of industrial ventilation systems.
1. The mercury thermometer is constructed of
glass and is subject to breakage, with
resulting exposure to a toxic material.
2. Both the mercury and dial thermometers have
a limited probe extension, making the
measurement of temperatures across large
ducts impossible.
3. The thermistor is easy to use but its
response becomes non-linear over some part
of its temperature range, making data
interpretation difficult.
4. The potentiometer used to measure the output
of a thermocouple is not yet available in an
intrinsically-safe construction and cannot
be used in areas where explosive or
ignitable materials may be present.
B. Despite its limitations, the thermocouple is
recommended as the primary method for measuring
temperatures. In situations where explosive or
ignitable materials may be present, use of the
dial thermometer is suggested.
1. The most common thermocouple, and the one
recommended for use in inspections, is
Type K. The Type K thermocouple has a
temperature range of -400°F to +2,300°F and
is constructed with a positive wire of
chromel and a negative wire of alumel.
2. The thermocouple/potentiometer is not a
reference instrument and must be
Lesson 6 6-7 Measurement
-------
calibrated against a National Institute of SLIDES AND
Standards and Technology (NIST) traceable NOTES
to ensure accuracy-
6-15
a. Since the equipment required to do this
is expensive and not likely to be
available to the inspector, it may be
necessary to send the unit to a
specialized laboratory for calibration.
b. For most inspection situations, however,
high accuracy is not required. In these
cases, an acceptable evaluation of
instrument accuracy may be conducted by
checking its response in an ice bath and
a boiling water bath.
C. There are several potential sources of error in 6-16
making temperature measurements:
1. Unrepresentative measurement location
2. Cooling of the probe by infiltrated air
3. Impaction of water droplets on probe
D. Use of an unrepresentative location can be
avoided by making measurements at several
locations across the duct cross-section and
averaging them.
1. To reach locations well within the duct, the 6-17
thermocouple wire will need to be supported.
One satisfactory technique is to thread the
wire through a small diameter copper tube.
2. Since locations near the wall of a hot duct
will be cooler than near the center,
measurements made there may not be
representative of actual temperatures.
E. Problems can also occur from the cooling of
the probe due to air infiltration through the 6-18
port or through leaks into the duct upstream of
the measurement point.
1. The former problem can be avoided by sealing
the port in the manner described for static
pressure measurements.
Lesson 6 6-8 Measurement
-------
2. If a copper tube is used to support the SLIDES AND
thermocouple, it could be bent slightly so NOTES
that it extends into the oncoming gas
stream.
3. To avoid problems from upstream leaks, the
area near the measurement location should be
inspected for holes in the duct or leaks in
inspection hatches or expansion joints.
a. If these are found to exist, the
measurement location should be changed to
an area where these leaks will have mixed
into the flow.
b. If this is not possible, the number of
measurement points used to obtain an
average should be increased.
F. Measurements downstream of evaporative coolers
or wet scrubbers can be complicated due to the
presence of water droplets. Under these
conditions, the most reasonable option is to 6-19
shield the sensor. It should be realized,
however, that doing this will likely slow the
response of the sensor, requiring longer times
to make the measurements.
V- Fan speed measurement
A. Techniques available for the measurement of fan 6-29
speed include:
1. Standard tachometers
2. Strobetachometers
3. Phototachometers
B. Strobetachometers and phototachometers afre
expensive instruments that are not likely to be
available to the inspector. Also,
phototachometers require reflective tape to be
placed on the drive shaft and this can only be
done when the shaft is not moving.
Lesson 6 6-9 Measurement
-------
C. The recommended technique for measuring fan SLIDES AND
speed is the standard tachometer. NOTES
1. The easiest location for making the
measurement is on the end of the shaft,
through the access hole in the belt guard.
a. If no access hole is provided, the
inspector should request the assistance
of plant personnel.
b. Under no circumstances should the
inspector attempt to obtain access to the
shaft end by enlarging the mesh covering
the belt guard.
2. An alternative measurement location is on
the shaft, using the roller attachment
supplied with the tachometer. However,
using this method requires knowledge of the
shaft diameter in order to calculate the
rotational speed from the tachometer
reading.
D. An estimate of the fan speed can be obtained by
measuring the diameter of the fan and motor
sheaves and using their ratio, as follows: 6-30
Fan rpm = MS(MD/FD)
6-31
MD = motor sheave diameter
FD = fan sheave diameter
MS = motor speed (rpm)
1. Motors are generally available in the
nominal speeds of 600, 1200, 1800, 2400 and
3600 rpm. The actual speed is somewhat less
than the nominal value and is stamped on the
motor nameplate.
2. The inspector should be aware of belt
squeal, which can affect fan rpm, and severe
vibration, which can be a safety hazard.
Lesson 6 6-10 Measurement
-------
VI. Flowrate measurement SLIDES AND
NOTES
A. Measurement of gas flowrate in ducts is
accomplished by first measuring the average 6-20
velocity pressure and temperature of the gas
stream and then calculating the average
velocity. The flowrate is obtained by
multiplying this average velocity by the duct
cross-sectional area.
B. Procedures for conducting this measurement are 6-21
contained in 40CFR60, Appendix A, Methods 1
through 4, as part of the procedures for
conducting compliance sampling. Since the
level of accuracy reguired for inspection of
industrial ventilation systems is not as high 6-22
as that needed for compliance sampling, some
variances to these methods will be employed to
expand their application and simplify the
procedures and calculations, as follows:
1. Method 1 limits the technigue to ducts
larger than 12 inches diameter. For
inspection purposes, the procedures will be
applied to ducts of all sizes. To minimize
errors, a pitot tube smaller than 5/16 inch
O.D. should be used in ducts smaller than 12
inches diameter.
2. Method 1 prohibits the location of
measurement points within 1 inch of the wall
for ducts larger than 24 inches diameter and
within 0.5 inch of the wall for ducts
smaller than 24 inches diameter. For
inspection purposes, measurement points will
be at the locations prescribed by the
location procedures, with no adjustments
made.
3. Method 2 requires the determination of the
apparent dry molecular weight using Method
3 and the moisture content using Method 4 in
order to calculate the gas velocity and
flowrate. For inspection purposes, an
apparent dry molecular weight of 28.95 and
a moisture content of zero will be assumed.
4. Method 2 requires the measurement of the
absolute stack pressure in order to
calculate the gas velocity and flowrate.
Lesson 6 6-11 Measurement
-------
For inspection purposes, an absolute stack SLIDES AND
pressure of 29.92 in. Hg will be assumed. NOTES
C. Measurement of velocity pressure can be made
with either a standard pitot tube or an S-type 6-23
(Staubscheid) pitot tube. The S-type pitot is
preferred when there are particles in the gas
stream that could plug the static pressure
holes of a standard pitot.
1. If the construction of a standard pitot
conforms to Section 2.7 of Method 2, it does 6-24
not have to be calibrated and may be
assigned a pitot coefficient, Cp, of 0.99.
2. An S-type pitot may be assigned a pitot
coefficient of 0.84 if its construction
conforms to Section 4.1 of Method 2.
3. Procedures for calibrating an S-type pitot
may be found in Section 4 of Method 2.
D. For highest accuracy, pressures measured with
the pitot tube should be read using an inclined
manometer. If less accuracy is acceptable, a
0-2 in. H2O Magnehelic pressure gauge could be
substituted for the manometer.
E. The number of locations that are used to
compute the averages depends on the degree of
accuracy desired. This figure provides
guidance in determining the minimum number of
locations.
1. The number of locations is first determined 6-25
for the distance downstream from an
obstruction by reading vertically upward
from the lower x-axis.
2. The number of locations is then determined
for the distance upstream from ^n
obstruction by reading vertically downward
from the upper x-axis.
3. The larger of these two numbers is the
minimum number of locations or traverse
points.
Lesson 6 6-12 Measurement
-------
F. For circular ducts, the number of traverse SLIDES AND
points determined is divided by two to NOTES
determine the number of measurement points on
each diameter. The location of each traverse
point is given in this table as a percentage of 6-26
duct diameter from the inside wall to the point
location. 6-27
G. With rectangular ducts, the number of traverse
points is determined using an equivalent
diameter determined from:
De = 2LW/(L + W)
The cross-section is then divided into a grid
of equal rectangular areas and measurements are
made in the center of each grid element. The
grid configuration should be either
3x3, 4x3 or 4x4, depending on the number
of measurement locations needed.
H. Downstream of such devices as cyclones, 6-28
inertial demisters or ducts with tangential
entry, a swirling or cyclonic motion may be
encountered. When high accuracy is desired, it
should be determined whether the degree of
cyclonic flow is enough to cause significant
error in the measurements. The procedure for
accomplishing this is as follows:
1. Level and zero the manometer.
2. Connect an S-type pitot to the manometer.
3. Place the pitot tube at each traverse point
so that the openings are perpendicular to
the duct cross-sectional plane. In this
position, each tube should be reading static
pressure, and the indication of the
manometer should be zero.
4. If the differential pressure is not zero,
rotate the pitot tube until a zero reading
is obtained and record the resulting angle.
5. Calculate the average of the absolute values
of the angles, including those angles that
were zero (no rotation required) . If the
average is greater than
Lesson 6 6-13 Measurement
-------
20 degrees, the flow conditions at that SLIDES AND
location are not acceptable. NOTES
I. Once an acceptable location has been
identified, the velocity pressure and
temperature measurements are performed and the
averages are calculated.
1. Average velocity pressure is determined by
averaging the square roots of velocity
pressures measured at the prescribed
locations.
2. The temperature is measured at the same time
by attaching a thermocouple to the pitot
tube, and the average is calculated
arithmetically.
3. The average gas velocity is determined from:
V = 2.9C (VP°-5) (T )°'5
v ^..j^p^vjr / averagev average'
V = average gas velocity (feet/sec)
C = pitot coefficient
(dimensionless)
VP = velocity pressure (in. H2O)
T = gas temperature (°R)
4. The average gas flowrate is determined from:
Q = 60VA
Q = average gas flowrate (ft3/min)
A = duct cross-sectional area (ft2)
J. Other methods are available for determining gas
velocity and these are typically applied to
measurements at the hood face. To determine
flowrate with these devices, it would be
necessary to make several velocity measurements
across the face of the hood, determine an
average and then multiply it by the area of the
hood opening.
1. The rotating vane anemometer has a small
lightweight propeller that rotates as air
flows through the instrument. The
instrument is calibrated in feet and has to
be used with a timing device to determine
the velocity.
Lesson 6 6-14 Measurement
-------
2. Inside the instrument case of the swinging SLIDES AND
vane anemometer is an aluminum vane which NOTES
deflects the pointer on the scale in
proportion to the velocity. Air flows
through the probe and connecting tube into
the case and then through the channel which
contains the vane.
3. The Bacharach instrument is a rotating vane
instrument with a scale which reads directly
in feet per minute.
4. The probe of the hot wire anemometer is
provided with a wire element that is heated
with current from batteries in the
instrument case. As air flows over the
element, its temperature changes from what
it was in still air and the accompanying
resistance change is translated into
velocity on the indicating scale of the
instrument.
VII. Horsepower measurement
A. Estimates of operating horsepower can be made
in two ways.
1. The simplest method is to have plant
personnel measure the amperage while running
at load. This value would then be divided
by the full load amperage from the nameplate
and then multiplied by the rated horsepower
to obtain the estimated operating
horsepower. 6-32
2. Another method would require plant personnel
to measure both voltage and amperage while
running at load. For three phase motors,
these values would then be substituted into:
6-33
bhp = 3°-5VAfe/746
V = voltage
A = amperage
f = power factor
e = motor efficiency
For single phase motors, the square root of
3 is replaced by one.
Lesson 6 6-15 Measurement
-------
a. If the power factor were also measured SLIDES AND
and the motor efficiency determined from NOTES
the manufacturer, then a good value of
operating horsepower could be determined
with this relationship.
b. However, because of the time involved, we
can usually only estimate these
parameters and thereby obtain an estimate
of operating horsepower.
c. In the absence of other information, a
combined factor of 0.80-0.85 should be
used for the product of power factor
times motor efficiency.
B. Determination of operating horsepower is an
involved process that is not likely to be
performed very often. Also, because of the
procedures and measurements required, it should
be performed only by plant personnel and never
by the inspector. The procedure plant
personnel should use is as follows:
1. Prepare a graph like that shown, with
horsepower on the x-axis and amperage on the
y-axis.
2. Disconnect the motor from the fan and
measure the amperage when running at no
load. Mark this reading as point "a" on the
y-axis. Divide the no-load amperage by two
and mark this value as point "b" on the
y-axis.
3. Read the full load amperage from the motor
nameplate and draw a horizontal line across
the graph at this value. Read the rated
horsepower from the nameplate and draw a
vertical line at this value until it
intersects the full load amperage line.
Call this intersection point "c". Draw a
straight line from "b" to "c".
4. Divide the rated horsepower by two and draw
a vertical line at this value until it
intersects the line from "b" to "c". Call
this intersection point "d11- Draw a smooth
curve through points "a", "d" and "c".
Lesson 6 6-16 Measurement
-------
5. Connect the motor to the fan and measure the SLIDES AND
amperage when running at load. Read the NOTES
corresponding horsepower from the curve
"a-d-c".
Once the relationship between amperage and
horsepower is determined, it could be used
in subsequent inspections, provided the
motor has not been changed.
VIII. Use of grounding cables 6-34
A. When working with portable instruments in areas
where potentially explosive or ignitable
materials are present, all metal probes should
be grounded to the duct to avoid a static
discharge.
B. Guidance on when to use grounding cables is
provided by the following list:
1. When the moisture content of the gas stream
is low.
2. When the gas stream velocity across the
probe is high.
3. When the gas stream contains a relatively
high mass concentration of small-sized
particles.
4. When there is the possibility of dust
deposits in the bottom of the duct.
5. When there is any question about the need
for a grounding cable.
C. The most satisfactory technique is to use a
stranded cable with a pipe clamp attached to
one end and a spring-loaded jaw clamp on the
other. The pipe clamp is firmly attached -to
the probe and the jaw clamp attached to the
duct, usually at a flange or support.
D. Care should be taken to assure a good
connection at the duct and that all paint and
rust has been penetrated.
1. One way to check the connection would be to
measure the resistance between the probe and
the duct using an explosion-proof ohmmeter.
2. If the resistance is less than 3 ohms, the
connection is good.
Lesson 6 6-17 Measurement
-------
PROBLEM SET 6
MEASUREMENT OF VENTILATION SYSTEM PARAMETERS
6-1. A measurement port on a 24 inch diameter duct is 42 inches
upstream from an elbow and 78 inches downstream from an
entry. Determine the minimum number of measurement
points and their locations in order to make an acceptable
measurement of flowrate.
Solution
Upstream = 42/24 = 1.75D (12 points)
Downstream = 78/24 = 3.25D (16 points)
Use 2 traverses of 8 points each
Locations in inches from wall:
0.77
2.52
4.66
7.75
16.25
19.34
21.48
23.23
Lesson 6 6-18 Measurement
-------
6-2. Measurements on an 18 inch diameter duct with an S-type
pitot tube give the following readings:
Location Parameter Point Number
Traverse 1 VP (in. H20) 0.22 0.23 0.22 0.20 0.23 0.20
T (°F) 86.9 87.0 87.3 87.1 86.9 86.8
Traverse 2 VP (in. H2O) 0.14 0.20 0.20 0.10 0.14 0.23
T (°F) 85.7 85.0 84.9 84.8 84.7 84.7
Determine the flowrate at actual conditions.
Solution
(VP)0-5 = 0.44
Tavg = 86.0 °F
= 546 °R
V = 2.9 (0.84) (0.44) (546)0'5
25.05 ft/sec
(60) (25.05) [(7T/4) (18/12)2]
2.656 acfm
Lesson 6 6-19 Measurement
-------
6-3. The sheave on a fan shaft is 24 inches diameter and the
sheave on the drive motor is 8 inches diameter. Estimate
the fan speed if the motor speed is 1725 rpm.
Solution
Fan speed = 1725 (8/24)
= 575 rpm
Lesson 6 6-20 Measurement
-------
LESSON 7
VENTILATION SYSTEM INSPECTION
Goal:
To summarize and organize the inspection points and procedures from
previous lessons.
Objectives:
At the end of this lesson the student should be able to:
1. Describe the four levels involved in inspecting air
pollution sources.
2. List the items appropriate for Level 2 inspections of the
components of an industrial ventilation system.
3. List the items appropriate for Level 3 inspections of the
components of an industrial ventilation system.
4. Conduct effective inspections of industrial ventilation
systems.
Lesson 7 7-1 Inspection
-------
List of Slides
7-1
7-2
7-3
7-4
7-5
7-6
7-7
7-8
7-9
7-10
7-11
7-12
7-13
7-14
Ventilation system inspection
Level 2
Level 2 items for hoods
items for ducts
items for coolers
items for fans
Level 2
Level 2
Level 2
Level 3
Level
Level
Level
Level
items for hoods
items for ducts
items for coolers
items for fans
Completed flowchart for soil incinerator
Graph of static pressure profile
Graph of temperature profile
3
3
3
3
Lesson 7
7-2
Inspection
-------
I. Introduction
A. The efforts involved in inspecting air
pollution sources are generally categorized
according to a system of "levels", as follows:
1. Level 1 - visual evaluation of stack opacity
and fugitive emissions from off the plant
site.
2. Level 2 - on-site evaluation of the control
system relying on plant instruments for the
values of any inspection parameters.
3. Level 3 - similar to Level 2, but relying on
measurements by the inspector to determine
missing or inaccurate inspection parameters.
4. Level 4 - similar to Level 3, but including
the development of a process flowchart,
determination of measurement port locations
and evaluation of safety hazards and
protective equipment needs. If the process
or control equipment do not change, this
level of inspection would only be conducted
once.
B. The inspection level that is actually utilized
is dictated by the individual situation and
based on the judgement of the inspector.
1. For example, if a Level 1 inspection
indicates no problems, the inspector may
elect to terminate the inspection and
proceed to another facility-
2. Or, if in the course of a Level 2
inspection, critical information is needed
to complete the evaluation, the inspector
may elect to proceed to Level 3, making
on-site measurements to obtain the data.
C. These same four levels can also be applied to
the inspection of industrial ventilation
systems.
1. Level 1 would be limited to an off-site
evaluation of fugitive emissions from hoods
and ducts.
2. Most inspections will be conducted at Level
2, with the occasional need for a Level 3
evaluation, and would follow the same
approach used with control devices.
SLIDES AND
NOTES
7-1
Lesson 7
7-3
Inspection
-------
3. The additional items in a Level 4 would SLIDES AND
focus on port locations and safety issues. NOTES
II. Level 2 inspections 7~2
A. Hoods 7~3
1. Capture efficiency: visual evaluation of
fugitive losses as indicated by escaping
dust or refraction lines.
2. Physical condition: hood modifications or
damage that could affect performance;
evidence of corrosion.
3. Fit of "swing-away" joints: evaluation of
gap distance between hood system and duct
system on movable hoods.
4. Hood position/cross-drafts: location of
hood relative to point of contaminant
generation; effect of air currents on
contaminant capture.
B. Ducts 7-4
1. Physical condition: indications of
corrosion, erosion or physical damage;
presence of fugitive emissions.
2. Position of emergency dampers: emergency
by-pass dampers should be closed and not
leaking.
3. Position of balancing dampers: a change in
damper positions will change flowrates; mark
dampers with felt pen to document position
for later inspections.
4. Condition of balancing dampers: damper
blades can erode, changing system balance;
remove a few dampers to check their
condition.
C. Coolers 7-5
1. Physical condition: indications of
corrosion, erosion or physical damage;
presence of fugitive emissions.
Lesson 7 7_4 Inspection
-------
2. Outlet temperature: observe plant SLIDES AND
instruments to determine cooler effective- NOTES
ness; if controller is used, compare to
set-point value.
3. Spray pattern/nozzle condition: indications
of effective atomization on evaporative
coolers.
4. Water flowrate: observe plant flow meters
or pressure gauges to evaluate changes in
water flowrate on evaporative coolers.
D. Fans 7-6
1. Physical condition: indications of
corrosion.
2. Vibration: indications of balance problems
due to material build-up or wheel erosion or
corrosion; severely vibrating fans are a
safety hazard.
3. Belt squeal: squealing belts under normal
operation indicate a loss of air volume.
4. Fan wheel build-up/corrosion: internal
inspection of non-operating fans.
5. Condition of isolation sleeves: check
vibration isolation sleeves for holes.
6. .Rotation direction: check rotation
direction with direction marked on fan
housing.
III. Level 3 inspections 7-7
A. Hoods 7-8
1. Estimated volume: estimate flowrate using
SPh/ r and hood configuration.
2. Actual volume: determine flowrate by
measuring VP and temperature.
B. Ducts 7-9
1. Change in gas temperature: measure
temperature change across a section of duct
to. evaluate air infiltration.
Lesson 7 7-5 Inspection
-------
2. Change in static pressure: measure static SLIDES AND
pressure change across a duct section to NOTES
evaluate duct deposits; compare measure-
ments to calculations for clean duct.
3. Air volume: determine flowrate by measuring
VP and temperature.
C. Coolers 7-10
1. Inlet and outlet temperatures: measure
inlet and outlet temperature to evaluate
cooling effectiveness.
2. Water requirement: estimate water
requirement for evaporative coolers using
inlet and outlet temperatures and enthalpy
relationships; compare to actual use
information supplied by plant personnel.
3. Water turbidity: perform settling test on
water sample gathered by plant personnel to
evaluate particle size of solids.
4. Air volume: estimate air volume in dilution
cooling systems using measured temperatures
and enthalpy relationships; could also be
determined by measuring VP and temperature.
D. Fans
1. Volume changes: estimate new flowrate using 7-11
known performance (Q, rpm and r) and new rpm
2. Estimated volume: estimate flowrate using
rpm, FSP, temperature and ratings table;
could also be done using bhp, FSP,
temperature and ratings table.
IV. Use of flowcharts
A. Organizing inspection information on a 7-12
flowchart of the process aids interpretation
and evaluation
B. One normally expects static pressures to
decrease (become more negative) from the hood
toward the fan and to decrease (become less 7-13
positive) from the fan to the stack.
C. In general, temperatures should decrease
throughout the system, with significant drops
across cooling devices. A small rise in 7-14
temperature across may be noted due to
compression of the gas.
Lesson 7 7-6 Inspection
-------
PROBLEM SET 7
VENTILATION SYSTEM INSPECTION
The students will be "calculated out" by this point in the
course, so it is suggested that the instructor use this time to tie
together the inspection procedures by having the class talk through
the inspection of several situations presented to them. The
instructor should first present the situation and them have the
students list the various things that could be causing the problem.
It is helpful if the instructor maintains a list of the potential
caused on a blackboard, flip-chart or overhead transparency. Once
the potential causes have been identified, the instructor should
have the students discuss how they would check-out each one. Some
situations for class discussion are presented here; however, the
instructor may wish to use examples from his or her own
experiences.
Lesson 7 7-7 Inspection
-------
7-1 Emissions from transfer points in an ambient-condition
material handling process are collected with five hoods and
conducted to a pulse-jet fabric filter collector. A
preliminary Level 2 inspection finds dust escaping from all the
hoods; however, the stack visible emissions are in compliance.
Baseline data are available for hood static pressures,
inlet and outlet collector static pressures, fan speed and
stack visible emissions. What could be causing the fugitive
losses and how would you check-out each potential cause?
Solution
This situation could be caused by modified or damaged hoods;
but, since it is affecting all five of them, this is not
likely. There could also be an increase in the "fines" content
of the materials being processed, but a well-designed hood
should be able to handle this occurrence. The most likely
cause for this situation is decreased air volume at the hoods.
This could be confirmed by measuring the hood static pressures
and comparing them to the baseline values. If the pressure
decreases were not proportional, then the problem (or problems)
could be in the branch ducts to each hood, or there could be a
problem in some of the branch ducts in combination with a
downstream problem. Measurements of the air volume could also
be used to determine decreased airflow at the hoods.
Assuming proportional decreases in hood static pressure,
the decreased air volume could result from a number of causes,
as indicated below.
a. Holes in the main duct leading to the collector:
Evaluate with a visual inspection (best approach); check
static pressure at collector inlet to see if it has
decreased (may not be a good indicator-may not change
substantially or may be affected by other problems);
measure air volume at positions along duct looking for
unexplained increases (time consuming).
b. Main duct partially plugged: Check static pressure at
collector inlet to see if it has increased (best
approach); measure static pressure at several locations
along duct and plot versus equivalent length (time
consuming, but locates the problem); measure static
pressure change across suspect section and compare to
expected value-get H from estimated velocity based on
change in hood static pressures (time consuming-may not
be very accurate because of estimated velocity).
c. Main duct damaged: Evaluate with a visual inspection
(check upstream and downstream of the collector-damage
either place could reduce volume).
Lesson 7 7-8 Inspection
-------
d. Fan speed slowed down: Measure fan rpm and compare to
baseline values (best approach); estimate fan rpm from
sheave diameters and compare to baseline values (less
accurate, but cheaper).
e. Collector static pressure drop increased: Determine
collector pressure drop and compare to baseline value
(reasons for increased collector pressure drop are not
subject of this course - refer to APTI Course 445).
f. Air infiltration at collector: Evaluate with collector
inspection procedures (not a subject of this course-refer
students to APTI Course 445).
g. Damper position changed: Evaluate with a visual
inspection; if damper is upstream of collector, check
collector inlet static pressure to see if it has
increased; if damper is downstream of collector, check
collector outlet static pressure to see if it has
decreased.
Lesson 7 7-9 Inspection
-------
7-2. Emissions from transfer points in an ambient-condition
material handling process are collected with five hoods and
conducted to a pulse-jet fabric filter collector. A
preliminary Level 2 inspection finds dust escaping from one
of the hoods; however, the other hoods appear to be
collecting well and the stack visible emissions are in
compliance. Baseline data are available for hood static
pressures, inlet and outlet collector static pressures, fan
speed and stack visible emissions. What could be causing
the fugitive losses, and how would you check-out each
potential cause?
Solution
As in the previous problem, this situation could be the
result of decreased air volume at the one hood. This could
be confirmed by measuring the hood static pressure and com-
paring it to the baseline value. Measurement of the air
volume could also be used to determine decreased airflow at
the hood. Since only one hood is affected, it is now more
likely that a modified or damaged hood could be responsible.
This could be checked by inspecting the hood to see if it
conforms to good design practices. Comparison to
recommended hood designs from a reference text such as
ACGIH's Industrial Ventilation could also be made.
Assuming the problem is found to be decreased air volume,
the following are possible causes and techniques for their
evaluation.
a. Holes in the duct leading from the hood: Evaluate with
a visual inspection(best approach); measure air volume at
positions along duct looking for unexplained
increases(time consuming).
b. Duct partially plugged: Measure static pressure at
several locations along duct and plot versus equivalent
length (time consuming, but also locates the problem);
measure static pressure change across suspect section and
compare to expected value-get H from estimated velocity
based on change in hood static pressure (time consuming-
may not be very accurate because of estimated velocity).
c. Duct damaged: Evaluate with a visual inspection.
d. Damper position changed: Evaluate with a visual
inspection.
It is also possible that changes in the system balance have
occurred because of adjustments made elsewhere in the system. This
possibility could be checked by measuring the hood static pressures
of the other hoods and comparing them to the baseline values.
Increased flow at some hoods because of a change in damper position
may be causing decreased flow at the one hood.
Lesson 7 7-10 Inspection
-------
7-3. Emissions from transfer points in an ambient-condition
material handling process are collected with five hoods and
conducted to a pulse-jet fabric filter collector. A
preliminary Level 2 inspection finds dust escaping from one
of the hoods; however, the other hoods appear to be
collecting well, and the stack visible emissions are in
compliance. There are no baseline data available. What
could be causing the fugitive losses, and how would you
check-out each potential cause?
Solution
Since only one emission point is affected, it is possible that
a modified or damaged hood could be responsible. This could be
checked by inspecting the hood to see if it conforms to good design
practices. Comparison to recommended hood designs from a reference
text such as ACGIH's Industrial Ventilation could also be made.
As in the previous problem, this situation could also be the
result of decreased air volume at the one hood; however, since
baseline data are not available in this case, evaluation of this
potential is not as straight-forward. If there is a well-
functioning identical transfer point and hood in the system, the
inspector could measure its hood static pressure and compare it to
the measured hood static pressure of the malfunctioning hood.
Alternately, the air volume could be estimated from the hood static
pressure and configuration (or from fan performance or actually
measured) and used to determine the capture velocity. This could
be compared to typical values or to specific recommendations from
reference texts.
Assuming the problem is thought to be reduced air volume, the
following are possible causes and techniques for their evaluation.
a. Holes in the duct leading from the hood: Evaluate with
a visual inspection (best approach); measure air volume
at positions along duct looking for unexplained increases
(time consuming).
b. Duct partially plugged: Measure static pressure at
several locations along duct and plot versus equivalent
length (time consuming, but also locates the problem);
measure static pressure change across suspect section and
compare to expected value- get H from estimated
velocity based on hood static pressure and configuration
(time consuming-may not be accurate because of estimated
velocity).
c. Duct Damaged: Evaluate with a visual inspection.
d. Damper position changed: Cannot be evaluated without
baseline information.
Lesson 7 7-11 Inspection
-------
7-4. A constant volume hot gas process is equipped with an
evaporative cooler followed by a fixed-throat venturi
scrubber. A preliminary Level 2 inspection finds that stack
visible emissions have increased above the baseline value
but are still in compliance. Baseline data are available
for cooler inlet temperature, inlet and outlet collector
static pressures, pump discharge pressures for the scrubber
and the cooler, fan speed and stack visible emissions. What
could be causing the increased visible emissions, and how
would you check-out each potential cause?
Solution
Since the collector is a fixed throat design, a reduction in
air flow would cause the performance of the venturi scrubber to
decrease, leading to an increase in visible emissions. To evaluate
this potential, the inspector should first look at the process for
any sign of fugitive emissions. Also, since baseline fan speed is
available, the current fan speed could be measured or estimated and
compared to this value to see if it has been reduced. In addition,
the inspector could determine the pressure drop across the venturi
and compare this to the baseline value; however, since other
parameters (like liguid rate) also affect pressure drop, a definite
conclusion cannot be made from a pressure drop change alone.
Finally, the inspector could measure the air volume.
Another potential cause of increased visible emissions is lack
of sufficient cooling in the evaporation section. First, the
inspector should determine the cooler inlet temperature and compare
the cooling water pump discharge pressure to its baseline value to
determine any changes. If possible, the condition of the nozzles
should be determined through a visual examination to be sure that
any changes noted in pump pressure are due only to flow changes.
Also, since inadequate cooling water could also result from an
increase in gas flow, the fan speed should be determined and
compared to the baseline value, or the gas flowrate could be
measured.
Finally, increased visible emissions could result from the use
of cooling water containing a significant quantity of fine
particles. The inspector could check this by -t>bserving the
settling rate of particles in a water sample obtained by plant
personnel.
Lesson 7 7-12 Inspection
-------
APPENDIX A
SLIDES
-------
APPENDIX B
BIBLIOGRAPHY
B-l
-------
B-2
-------
ACGIH, Industrial Ventilation Manual, Twentieth Edition, Cincinnati, 1988.
Alden, J.L., Design of Industrial Exhaust Systems, Industrial Press, New York, 1939.
Aldina, G J., and J.A. Janke, "APT! Course 450: Source Sampling for Paniculate Pollutants
- Instructor's Guide", EPA-450/2-80-003, February 1980.
AMCA, "Fan Systems", Fan Application Manual, Part 1, Publication 201, Arlington Heights
(Illinois), 1979.
AMCA, "Field Performance Measurements", Fan Application Manual, Part 3, Publication
203, Arlington Heights (Illinois), 1976.
AMCA, "Troubleshooting", Fan Application Manual, Pan 2, Publication 202, Arlington
Heights (Illinois), 1976.
ANSI, "Fundamentals Governing the Design and Operation of Local Exhaust Systems",
American National Standard Z 9.2-1971, 1972.
ANSI, "Installation of Blower and Exhaust Systems for Dust, Stock and Vapor Removal or
Conveying", American National Standard Z 33.1, 1961.
ANSI, "Safety Code for the Use, Care and Protection of Abrasive Wheels", American
National Standard B 7.1-1970, 1970.
ASHRAE, Equipment Guide and Data Book, New York, 1972.
ASHRAE, Handbook of Fundamentals, Atlanta, 1985.
ASHRAE, HVAC Systems and Applications, Atlanta, 1987.
Astleford, W., "Engineering Control of Welding Fumes", NIOSH Publication 75-115,1974.
Baliff, J., L. Greenburg and A.C. Stern, 'Transport velocities for industrial, dusts-an
experimental study", Ind. Hyg. Quar., 9, 85 (1948).
Barr, H.S., R.H. Hocutt and J.B. Smith, "Cotton Dust Controls in Yarn Manufacturing",
NIOSH Publication No. 74-114,1974.
Barritt, S.L., "Duct design by programmable calculator", Heating, Piping &. Air Conditioning,
December 1978, p.28.
Bastress, E., J. Niedzwecki and A. Nugent, "Ventilation Requirements for Grinding, Buffing
and Polishing Operations", NIOSH Publication 75-107, 1974.
Baturin, V.V., Fundamentals of Industrial Ventilation, Pergamon Press, New York, 1972.
Brandt, A.D., "Should air be recirculated from industrial exhaust systems?", Heating, Piping
&Air Conditioning, 19, 69 (1947).
B-3
-------
Brandt, AD., Industrial Health Engineering, Wiley, New York, 1947.
Brown, EJ., "How to select multiple-leaf dampers for proper air flow control", Heating,
'Piping & Air Conditioning, April 1960, p. 167.
Brown, EJ., and H.E. Staub, "How to estimate system total pressure requirements",
'Heating, Piping & Air Conditioning, January 1971, p. 12.
Burgess W.A, and J. Murrow, "Evaluation of hoods for low volume-high velocity exhaust
systems", AIHA Journal, 37, 546 (1976).
Burgess, W.A, MJ. Ellenbecker and R.D. Treitman, Ventilation for Control of the Work
Environment, Wiley-Interscience, New York, 1989.
Burton, D J., Industrial Ventilation Work Book, DJBA, Salt Lake City, 1989.
Caplan, K.J., "Balance with blast gates~a precarious balance", Heating, Piping & Air
Conditioning, February 1983, p. 47.
Chamberlin, R., "The control of beryllium machining operations", Arch. Ind. Health, 19(2),
231 (1959).
Chen, S.Y.S., "Design procedure for duct calculations", Heating, Piping & Air Conditioning,
January 1981, p.41.
Cheremisinoff, P.N., and R.A Young, "Fans and blowers", Pollution Engineering, July 1974,
p. 54.
Chicago Blower Corporation, "A Course in Fan Arrangements and Classes", CBC-300,1981.
Chicago Blower Corporation, "Air Handling Equipment", 1982.
Chicago Blower Corporation, "Basic Course in Fan Density Correction", CBC-200,1981.
Chicago Blower Corporation, "Basic Course in Fan Selection", CBC-100,1981.
Churchill, S.W., "Friction factor equation span all fluid flow regimes", Chemical Engineering,
84,56(1977).
Clapp, D.E., D.S. Groh and J.D. Nenandic, "Ventilation design by microcomputer", AIHA
Journal, 43,212(1982).
Conroy, L., MJ. Ellenbecker and M. Flynn, "Prediction and measurement of velocity into
flanged slot hoods", AIHA Journal, 49, 226 (1988).
Constance, J A., "Estimating air friction in triangular ducts", Air Conditioning, Heating and
Ventilating, 60(6), 85 (1963).
Crowder, J.W., and KJ. Loudermilk, "Balancing of industrial ventilation systems", JAPCA,
32,115(1982).
Dalla Valle, J.M., "Velocity characteristics of hoods under suction", ASHVE Transactions,
38, 387 (1932).
B-4
-------
Dalla Valle, J.M., and T. Hatch, "Studies in the design of local exhaust hoods", ASME
Transactions, 54, 31 (1932).
Dalla Valle, J.M., Exhaust Hoods, Industrial Press, New York, 1952.
Danielson, J.A., ed., "Air Pollution Engineering Manual", Second Edition, EPA AP-40, May
1973.
Djamgowz, O.T., and S.A.A. Ghoneim, "Determining the pick-up air velocity of mineral
dusts", Can, Mining J., July 1974, p. 25.
Durr, D., N. Esman, C. Stanley and D. Weyel, "Pressure drop in elbows", Appl Ind. Hyg., 2,
57 (1986).
Ellenbecker, M.J., R. Gempel and W.A. Burgess, "Capture efficiency of local exhaust
ventilation systems", A1HA Journal, 44, 752 (1983).
Esman, N., D. Weyel and F. McGuigan, "Aerodynamic properties of exhaust hoods", AIHA
Journal, 47, 448(1986).
First, M.W., and L. Silverman, "Airfoil pitometer", I & EC, 42, 301 (1950).
Flanigan, LJ., S.G. Talbert, D.E. Semones and B.C. Kim, "Development of Design Criteria
for Exhaust Systems for Open Surface Tanks", NIOSH Publication 75-108,1975.
Fletcher, B., "Centerline velocity characteristics of local exhaust ventilation hoods", AIHA
Journal, 43, 626 (1982).
Fletcher, B., "Centerline velocity characteristics of rectangular hoods and slots under
suction", Ann. Occup. Hyg., 20, 141(1977).
Fletcher, B., "Effect of flanges on the velocity in front of exhaust ventilation hoods", Ann.
Occup. Hyg., 21, 265 (1978).
Fletcher, B., and A. Johnson, "Velocity profiles around hoods and slots and the .effects of an
adjacent plane", Ann. Occup. Hyg., 25,365 (1986).
Flynn, M., and MJ. Ellenbecker, "Capture efficiency of flanged circular local exhaust
hoods", Ann. Occup. Hyg., 30, 497 (1986).
Flynn, M., and MJ. Ellenbecker, "Empirical validation of theoretical velocity fields into
flanged circular hoods", AIHA Journal, 48, 380 (1987).
Flynn, M., and M J. Ellenbecker, "The potential flow solution for air flow into a flanged
circular hood", AIHA Journal, 46,318 (1985).
Garrison, R., "Centerline velocity gradients for plain and flanged local exhaust inlets", AIHA
Journal, 42, 739(1981).
Garrison R., "Velocity calculation for local exhaust inlets-graphical design", AIHA Journal,
44,941(1983).'
B-5
-------
Garrison R "Velocity calculation for local exhaust inlets-empirical design equations",
AIHA Journal, 44, 937 (1983).
Garrison, R., and D. Byers, "Static pressure and velocity characteristics of circular nozzles
for high velocity/low volume exhaust ventilation", AIHA Journal, 41, 803 (1980).
Garrison, R., and D. Byers, "Static pressure, velocity and noise characteristics of rectangular
nozzles for high velocity/low volume exhaust ventilation", AIHA Journal, 41, 855
(1980).
Geissler, H., "Purchased fan performance", Reprint No. 5483, Westinghouse Electric
Corporation, Pittsburgh, 1959.
Goldfield, J and F.E. Brandt, "Dust control techniques in the asbestos industry", AIHA
Journal, 35, 799 (1974).
Goodfellow, H., Advanced Design of Ventilation Systems for Contaminant Control,
Elsevier, New York, 1985.
Goodier, J.L., E. Boudreau, G. Coletta and R. Lucas, "Industrial Health and Safety Criteria
for Abrasive Blast Cleaning Operations", NIOSH Publication 75-112, 1975.
Guffey, S.E., and J. Hickey, "Equations for redesign of existing ventilation systems", AIHA
Journal, 44, 819 (1983).
Guffey, S.G., "An easier calculation system for ventilation design", AIHA Journal, 44, 627
(1983).
Hama, G.M., "A calibrating wind tunnel for air measuring instruments", Air Engineering, 41,
18(1967).
Hama, G.M., "Calibration of Alnor velometers",Aff£4/o«mfl/, 19,477 (1958).
Hama, G.M., and L.S. Curley, "Instrumentation for the measurement of low velocities with a
pitot tube", AIHA Journal, 28, 204 (1967).
Hama, G.M., "Ventilation control of dust from bagging operations", Heating and Ventilating,
April 1948, p.91.
Hama, G.M., and KJ. Bonkowski, "Ventilation requirements for airless spray painting",
Heating, Piping & Air Conditioning, October 1970, p. 80.
Hampl, V., and O.E. Johnson, "Control of wood dust from horizontal" belt, sanding", AIHA
Journal, 46, 567 (1985).
Hampl, V., O.E. Johnson and D.M. Murdock, "Application of an air curtain exhaust system
at a milling process", AIHA Journal, 49,167 (1988).
Hatch, T., "Design of exhaust hoods for dust control systems", /. Ind. Hyg. ToxicoL, 18, 595
(1936).
Healy, J.H., M.N. Patterson and E.J. Brown, "Pressure losses through fittings used in return
air duct systems", ASHRAE Transactions, 68, 281 (1962).
B-6
-------
Hemeon, W.C.L.. Plant and Process Ventilation, Second Edition, Industrial Press, New
York, 1963.
Hogan, E.E., "Design tips for better O&M", Pollution Engineering, March 1983, p. 16.
Huebener, D J., and R.T. Hughes, "Development of push-pull ventilation", AIHA Journal,
46,262(1985).
Huebscher, R.G., "Friction equivalents for round, square and rectangular ducts", Hearing,
Piping & Air Conditioning, 19, 127 (1947).
Hughes, R.T., and A~A. Amendola, "Recirculating exhaust air: guides, design parameters
and mathematical modeling", Plant Engineering, March 18, 1982, p.47.
Jorgensen, Robert, ed., Fan Engineering, Seventh Edition, Buffalo Forge Company,
Buffalo, 1970.
Kane, J.M., "Design of exhaust systems", Health and Ventilating, 42, 68 (1947).
Kane, J.M., "The application of local exhaust ventilation to eiectnc melting furnaces", Trans.
Am. Foundrymen's Assoc., 52, 1351 (1945).
Kashdan, E.R., D.W. Coy, JJ. Spivey, T. Cesta and H.D. Goodfellow, 'Technical Manual:
Hood System Capture of Process Fugitive Paniculate Emissions", EPA-600/7-86-016,
April 1986.
Kemner, W., R. Gerstle and Y. Shah, "Performance Evaluation Guide for Large Flow
Ventilation Systems", EPA-340/1-84-012, May 1984.
Koshland, C.P., and M.G. Yost, "Use of a spreadsheet in the design of an industrial
ventilation system", AppL Ind. Hyg., 2, 204 (1987).
Kurz, J.L., "Comparison between electronic and pitot-tube multi-point air velocity sensors
used in air flow measuring stations", Pollution Equipment News, December 1984, p.
58.
Loeffler, JJ., "Simplified equations for HVAC duct friction", ASHRAE J., January 1980, p.
76.
Lynch, J.R., "Computer design of industrial exhaust systems", Heating, Piping & Air
Conditioning, September 1968, p. 44.
Lynch, J.R., "Industrial ventilation: a new look at an old problem", Michigan's Occupational
Health, 19(3), 4(1974).
Madison, R.D., and W.R. Elliot, "Friction charts for gases including correction for
temperature, viscosity and pipe roughness", Heating, Piping & Air Conditioning, 18,
107(1946).
Malchaire J.B., "Design of industrial exhaust systems using a programmable calculator",
Ann. Occup. Hyg., 24, 217 (1981).
Markert, J.W., "Use of total pressure in air system design, fan selection", Heating, Piping d
Air Conditioning, October 1969. p. 70.
B-7
-------
McDermott, HJ.. Handbook of Ventilation for Contaminant Control, Ann Arbor Science.
Ann Arbor, 1977.
Mclnnes, R.G., B.R. Hobbs and S.V. Capone, "Guide for Inspecting Capture Systems and
Control Devices at Surface Coating Operations", EPA Contract 68-01-6316, Task 3j,
May 1982.
Midwest Research Institute, "Design Review Guide for Materials Handling Operations:
Chapter 4 - Capture/Control Systems", EPA Contract 68-01-6314, Task 6, February
1983.
Morse, F.B., ed., Trane Air Conditioning Manual, The Trane Company, La Crosse, 1965.
NIOSH, "Industrial Ventilation 588: Student Manual", August 1986.
Obler, H., "Ventilation modifications", Hearing, Piping & Air Conditioning, February 1980, p.
65.
Ower, E., and R.C. Pankhurst, The Measurement of Air Flow, Pergamon Press, Oxford,
1977.
Pring, R.T., J.F. Knudsen and R. Dennis, "Design of exhaust ventilation for solid material
handling", I&.EC, 41, 2442 (1949).
Rajhans, G.S., and R.W. Thompkins, "Critical velocities of mineral dusts", Can. Mining J.,
October 1967, p. 85.
Reason, J., "Fans", Power, September 1983.
Rennix, C.P., "Computer assisted ventilation design and evaluation", Appl Ind. HVR., 2, 32
(1987).
Richards, J., "Air Pollution Source Field Inspection Notebook", Revision 2, USEPA, APT!
June 1988.
Rogers, A.N., "Evaluation in fan selection", Reprint No. 5037, Westinghouse Electric
Corporation, Pittsburgh, 1954.
Rogers, A.N., "Selection of fan types", Reprint No. 5312, Westinghouse Electric
Corporation, Pittsburgh, 1957.
Rutgers University, "Industrial Ventilation: Student Manual", August 1989.
Schulte, H.F., E.C. Hyatt and F.S. Smith, "Exhaust ventilation for machine tools used on
materials of high toxicity",^/r/i. Ind. Hyg. Occup. Med., 5, 21 (1952).
Seeal, R., and J. Richards, "Inspection Techniques for Evaluation of Air Pollution Control
Equipment", Volume II, EPA-340/l-85-022b, September 1985.
Shorwell, H.P., "A ventilation design program for hand-held programmable computers"
AIHA Journal, 45, 749 (1984).
B-8
-------
Silverman, L., "Centerline velocity characteristics of round openings under suction", /. Ind.
Hyg. ToxicoL, 24, 259 (1942).
Silverman, L., "Fundamental factors in the design of lateral exhaust hoods for industrial
tanks",/. Ind. Hyg. ToxicoL, 23, 187 (1941).
Silverman, L., "Velocity characteristics of narrow exhaust slots",/. Ind. Hyg. ToxicoL, 24, 267
(1942).
Sisson, W., "OSHA spray booth air flow requirements", Pollution Engineering, November
1975, p. 31.
SMACNA, HVAC Duct System Design, First Edition, Vienna (Virginia), 1977.
SMACNA, HVAC Duct System Design: Tables and Charts, First Edition, Vienna
(Virginia), 1977.
SMACNA, Manual for the Balancing and Adjustment of Air Distribution Systems, First
Edition, Vienna (Virginia), 1967.
Sorg, G.R., "Fan acoustic basics: Part 1", Pollution Engineering, March 1983, p. 34.
Sorg, G.R., "Fan acoustic basics: Part 2", Pollution Engineering, April 1983, p. 30.
Staheli, A.H., "Control methods for reducing chlorinated hydrocarbon emissions from vapor
degreasers", Reprint No. 72-PEM-7, ASME, New York, 1972.
Thompson, J.E., and CJ. Trickier, "Fans and fan systems", Chemical Engineering, March 21,
1983, p. 48.
Tracy, W.EL, "Fan connections", Reprint No. 5100, Westinghouse Electric Corporation,
Pittsburgh, 1955.
Trickier, CJ., "Effect of system design on the fan", Engineering Letter No. E-4, New York
Blower, Chicago.
Trickier, C J~, "Field testing of fan systems", Engineering Letter No. E-3, New York Blower,
Chicago.
Trickier, CJ., "Fundamental characteristics of centrifugal fans", Engineering Letter No. E-l,
New York Blower, Chicago.
Trickier, CJ., "How to get more air from your fan", Engineering Letter No. E-5, New York
Blower, Chicago.
Trickier, CJ., "How to select centrifugal fans for quiet operation", Engineering Letter No.
E-13, New York Blower, Chicago.
USEPA, "Determination of Stack Gas Velocity and Volumetric Flow Rate", 40CFR60,
Appendix A, Method 2.
USEPA, "Plant Inspection Workshop Handout: Design, Operation and Maintenance of
Fans", July 1979.
B-9
-------
USEPA, "Sample and Velocity Traverses for Stationary Sources", 40CFR60, Appendix A,
Method 1.
Wright, D.K., "A new friction chart for round ducts", ASHVE Transactions, 51, 312 (1945).
-------
APPENDIX C
PSYCHROMETRIC CHARTS
c-i
-------
175 —
170 —
165 —
160 —
O
(X
co 150
Q
140 —
130 —
120 —
110
100
Psychrometric Chart for Humid Air
Barometric Pressure 29.92 in. Hg
Density Factor - Mixture
100
200
300
400 500 600 700 800 900
Dry Bulb Temperature In Degrees F.
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ATTENTION INSPECTOR TRAINING CONTACTS
The enclosed course package tided "Emission Capture and Gas Handling
System Inspection" is not a final version. Initial peer review has shown a number of
minor revisions and additions need to be done before the manuals are considered
complete. The manuals were used during the recent telecourse broadcast with
additional figures, tables and example problems added by the instructor to clarify
some lecture points. These revisions will be made during FY 1994 by the course
instructor, Jerry Crowder, UTA Compliance Training Support Center, Arlington, TX.
The video tape set of the 15 hour telecourse should be available in 6 weeks. Each
Regional Office and State Office may request a set at that time by contacting Betty
Abramson, APTB, phone 919/541-2371. Call Kirk Foster, SSCD, phone 919/541-
4571 if you have any questions concerning the course materials.
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BACKGROUND INFORMATION AND INVENTORY SHEET FOR
STATIONARY SOURCE COMPLIANCE TRAINING COURSE/WORKSHOP SERIES
PART I - COURSE INFORMATION
Course No.: AITP #345/APTI #345
Course Title: Emission Capture And Gas Handling System Inspection (also called
Inspection Of Industrial Ventilation Systems)
Course Category: Air Inspector Training Curriculum Intermediate Level
Course Type: Classroom course, 2-3 days, 1-2 instructors, with course manuals
(3), reference manuals (3), technical guides (3) included in course
reference manuals, and slides (250)
Development Status: Course manuals and slides were revised March 1993. Course
materials are considered up to date.
Course Description:
This course is designed for Federal and State/local agency compliance staff responsible for
inspecting and evaluating the performance of emission capture and collection systems. The
course provides students with an understanding of the components of industrial ventilation
systems, including hoods, ducts, gas coolers and fans. Basic ventilation system design principles
are reviewed and operation and maintenance practices discussed in regards to their affect on long
term equipment performance. However, the focus of the course is on inspection and
performance evaluation procedures. Case studies of various ventilation systems are included to
assist students in developing trouble-shooting skills. The importance of properly designed,
operated and maintained emission capture and transport systems to overall control performance is
stressed.
Major Course Topics include:
• Properties of air and air-water vapor mixtures
• Hood types, their design and performance characteristics,
and techniques for their evaluation
• Duct design and key failure points
• Gas cooling equipment design and performance characteristics
• Fan system design and fan performance characteristics
• Key ventilation system operating parameters and
parameter measurement techniques nT^pI R ?*SV "brar?
• Inspection and performance analysis procedures Kegion VII
Key Contacts For Information/Revisions:
EPA Project Leader: Kirk Foster, SSCD MD-17, EPA, Research Triangle Park, NIC 2771 1,
Telephone: 919/541-4571
Principle Author: Jerry Crowder, Crowder Environmental Assoc., 2905 Province Place,
Piano, TX 75075, Telephone: 214/964-7661, Fax: 214/867-3617
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PART II - COURSE INSTRUCTOR(S)
Qualified Instructors/Contractors For Course #345:
Most Experienced Team: Jerry Crowder, Phd., Crowder Environmental Assoc., without
other instructor assistance, (Phone: 214/964-7661, Fax:
214/867-3617)
Other Qualified Teams:
Team 1: John Richards, Phd., Richards Engineering, Durham NC, without other instructor
assistance, (Phone: 919/489-8273)
Qualified Instructors For Related Courses:
Option 1: Raymond Manganelli, Phd., Environmental Sciences, Cook College, Rutgers
University, New Brunswick, NJ. Can be contacted through the Rutgers
Inspector Training Center via Mike Gallo, jr. Phone 908/932-7715. Dr.
Manganelli is the principle instructor for EPA/Rutgers inspector training course of
the same title. The Rutgers course is a modified version of #345 presented in 2
1/2 days and includes a flow measurement lab session. The course is usually
presented only at the Rutgers Training Center.
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PART III - COURSE MATERIALS INVENTORY SHEET
Course # and Title:
Course 345 Emission Capture And Gas Handling System Inspection
(Also called Industrial Ventilation System Inspection)
Course Technical Contact:
Course Materials List:
Kirk Foster, SSCD MD-17, EPA, RTP, NC, Phone: 919/541-4571
Item/Title
Manual No.
Description/Comment
Instructors Package:
1.Instructor Manual
2.Slides set 200 slides
3.Instructor Reference Material Fans
And Fan Systems Manual
4. Post Test And Post Test Answer
Sheet
5.Plus student package
340/1-92-01 5b
340/1-92-015e
-Outline w/ notes manual
-Technical papers and reports on fan
system selection, design, and operation
Students Package:
1 .Student manual
2.Slide manual
3.Reference Volumes:
1 Industrial Ventilation System
Inspection Manuals
2 Guide On Measurement Ports
Location And Design
340/1-92-01 5a
340/1-92-01 5c
340/1-92-015d
340/1-92-01 5f
-Text type course manual
-Contains copy of all course slides
-Contains two manuals on industrial
ventilation system design and
inspection (600/7-86-016 & 340/1-84-
012)
-Technical guide on location and design
of AP control system parameter
measurement ports (340/1-84-017)
Optional Course Materials (Student):
(None)
(Note: The hot mix asphalt plant
description in chapter 15 in the Air
Pollution Engineering Manual (1992)
reference document has been used as a
group discussion problem on industrial
ventilation system and emission
problems orientation)
Additional Reference Materials:
(See "core technical reference
documents in attached list)
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PART IV - COURSE REFERENCE DOCUMENTS
(For Additional Reading and Technical Reference Library)
I. Inspection Manuals
1. Performance Evaluation Guide For Large Flow Ventilation Systems, EPA 340/1-
84-012, July 1984"
2. Guidelines On Preferred Location And Design Of Measurement Ports For Air
Pollution Control Systems, EPA 340/1-84-017. September 1984"
II. Technical Guides
1. Technical Manual: Hood System Capture of Process Fugitive Particulate
Emissions, EPA 600/7-86-01 6, April 1986"
2. Air Pollution Engineering Manual, Chapter 6 - Ancillary Equipment for Local
Exhaust Ventilation Systems, p. 155-205, Air & Waste Management Assoc.,
Pittsburgh, 1992"
3. Air Pollution Engineering Manual, Chapter 3 - Design of Local exhaust systems, p.
25-87, AP-40, US EPA, May 1973 (out of print)"
3. Industrial Ventilation, Twentieth Edition, ACGI, Cincinnati, OH, 1988
III. Technical Reports And Articles
1. Fans Special Report, John Reason, Power Journal, September 1983
2. Fans, Robert Aberbach, Power Journal, March 1968
IV. Technical Books
1. H. D. Goodfellow, Advanced Design of Ventilation Systems for Contaminant
Control, Elsevier Science Publishing Co., New York, 1987
2. Henry McDermott, Handbook of Ventilation Control, Ann Arbor Science, Ann
Arbor, Ml, 1977
V. Industrial Publications
1. The Fundamentals of the Operation and Maintenance of the Exhaust Gas System
in a Hot Mix Asphalt Facility, IS-52/87, National Asphalt Pavement Association,
Revised 1987"m
(1) Available from: National Asphalt Pavement Association, 5100 Forbes Blvd. Lanham,
MD 20706-4413, telephone (301) 731-4748, price $100 + $7.50 s&h
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