United btates
Environmenta1 Proxection
Agency
Air Pollution Training Institute
MD20
Environment*! Research Center
Research Triangle Park NC 27711
DRAFT 2-1-83
Air
APTI
f\ Ol§^ A P% Introduction to Baseline
V/OUrSG Ol- i"^"0 Source Inspection Techniques
REFERENCE
BASELINE TECHNIQUES FOR AIR
POLLUTION CONTROL EQUIPMENT
PERFORMANCE EVALUATION
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FORusEwrm
API! COURSE SI: 445
DRAFT 2-1-83
BASELINE TECHNIQUES FOR AIR
POLLUTION CONTROL EQUIPMENT
PERFORMANCE EVALUATION
by
John R. Richards
Engineering-Science
501 Wlllard Street
Durham, NC 27701
919-682-9611
Contract No. 68-01-6312
Task No. 30
Project No. 9430
Project Officer
Kirk E. Foster
Stationary Source Compliance Division
U.S. Environmental Protection Agency
Washington, D.C. 20460
February 1983
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DISCLAIMER
This draft report was furnished to the U.S. Environmental Protection
Agency by Engineering-Science, Inc., Durham, North Carolina 27701. It is
not an official policy and standards document. The opinions, findings,
and conclusions are those of the authors and not necessarily those of the
Environmental Protection Agency. Every attempt has been made to represent
the present state of the art as well as subject areas still under evalua-
tion. Any mention of products or organizations does not constitute en-
dorsement by the United States Environmental Protection Agency.
The U.S. Environmental Protection Agency does not endorse any speci-
fic Inspection procedure. This report is presented for informational
purposes only. Inspectors are encouraged to seek information concerning
specific procedures, especially safety procedures which have been adopted
at their agency or company. This report is not intended to abbreviate,
alter or supercede these procedures.
11
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ACKNOWLEDGEMENTS
Engineering-Science appreciates the assistance provided by the EPA Task
Manager, Mr. Kirk E. Foster. Numerous Engineering-Science personnel made
valuable contributions to this report. Ms. Robin Segal! prepared the sections
concerning inspection of flares and concerning the legal and administrative
aspects of plant inspection. Mr. Cal Thames prepared the section on inspection
of carbon bed adsorbers. Useful information was provided by Mr. Ted Michael is
and Mr. Macon Shepard concerning carbon bed adsorbers.
ill
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TABLE OF CONTENTS
Page
1.0 INTRODUCTION TO BASELINE INSPECTION TECHNIQUE 1-1
1.1 The Baseline Technique 1-2
1.2 Underlying Principles 1-3
2.0 ELECTROSTATIC PRECIPITATORS 2-1
2.1 Components and Operation 2-1
2.2 Inspection Procedures 2-8
2.3 References 2-14
3.0 FABRIC FILTERS 3-1
3.1 Components and Operation 3-1
3.1.1 Pulse Jet Fabric Filters 3-1
3.1.2 Reverse Air (Outslde-to-Inslde) Collectors 3-3
3.1.3 Reverse Air (Inside-to-0uts1de) Collectors 3-4
3.1.4 Shaker Collectors 3-5
3.2 Inspection/Maintenance 3-5
3.2.1 Pulse Jet Filters 3-5
3.2.2 Reverse Air (Outslde-to-Inside) Collectors 3-7
3.2.3 Reverse A1r (Inside-to-Outside) Collectors 3-8
3.2.4 Shaker Collectors 3-9
3.3 References 3-10
4.0 WET SCRUBBERS 4-1
4.1 Components and Operation of Particulate Scrubbers 4-1
4.1.1 Preformed Spray Scrubbers 4-2
4.1.2 Tray-Type Scrubbers 4-3
4.1.3 Packed-Bed Scrubbers 4-4
4.1.4 Venturi and Ori fice Scrubbers 4-5
4.1.4.1 Venturi Scrubber 4-5
4.1.4.2 Variable Throat Venturi Scrubbers 4-5
4.1.4.3 Orifice Scrubber 4-5
4.1.5 Mechanically Aided Scrubbers 4-5
4.2 Inspection Procedures 4-6
4.2.1 Opacity and Gas Flow Rate 4-6
4.2.2 Static Pressure Drop 4-7
4.2.3 External System Inspection 4-11
4.2.3.1 Demister 4-11
4.2.3.2 Throat (Venturi Scrubbers) 4-11
4.2.3.3 Shell 4-12
4.2.3.4 Precooler 4-12
4.2.3.5 Sump, Recirculation Line, Make-up 4-12
Line and Purge Line
4.3 References 4-14
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TABLE OF CONTENTS (Contd.)
Page
5.0 MECHANICAL COLLECTORS 5-1
5.1 Components and Operation 5-1
5.1.1 Simple Cyclones 5-1
5.1.2- Multiple Cyclones 5-3
5.2 Inspection Procedures 5-4
5.3 References 5-6
6.0 CARBON BED ADSORPTION SYSTEMS 6-1
6.1 Components and Operation 6-1
6.2 Inspectlon Procedures 6-4
6.3 References 6-8
7.0 FLARE 7-1
7.1 Components and Operation 7-1
7.1.1 Elevated Flares 7-2
7.1.2 Ground Flares 7-7
7.1.3 Forced Draft Flares 7-7
7.2 Inspection Procedures 7-9
7.3 References 7-11
8.0 AUXILIARY EQUIPMENT 8-1
8.1 VentH at1 on System 8-1
8.2 Fan Evalnation 8-4
8.2.1 Physical Condition of Fan Housing 8-5
8.2.2 Fan Operating Conditions 8-5
8.3 References 8-8
9.0 PROCESS EQUIPMENT 9-1
10.0 VISIBLE EMISSION EVALUATION 10-1
10.1 Observation Procedures 10-1
10.2 Basel 1 ne Eval uatlon 10-5
10.3 Limits to the Use of Opacity 10-9
10.4 References 10-9
11.0 SAFETY INFORMATION 11-1
11.1 General Procedures 11-2
11.1.1 Safety Training 11-3
11.1.2 Medical Monitoring Program 11-3
11.1.3 Written Safety Procedures 11-4
vi
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TABLE OF CONTENTS (Contd.)
11.2 Common Inspection/Maintenance Hazards 11-4
11.2.1 Inhalation of Toxic Agents and Asphyxiants 11-5
11.2.2 Accidental Falls 11-6
11.2.3 Noise 11-12
11.2.4 Head Protection 11-13
11.2.5 Eye Protection 11-13
11.2.6 Footwear 11-14
11.2.7 Burns 11-14
11.2.8 Heat Strees 11-14
11.2.9 Cold Weather Conditions 11-15
11.2.10 Electrical Shock 11-15
11.2.11 Ionizing Radiation 11-15
11.3 Confined Area Entry 11-17
11.3.1 General Entry Procedures 11-18
11.3.1.1 Electrostatic Precipitators 11-19
11.3.1.2 Fabric Filters 11-20
11.4 References 11-21
12.0 ADMINISTRATIVE AND LEGAL ASPECTS OF PLANT INSPECTIONS 12-1
12.1 Introduction 12-1
12.2 Preinspection Procedures 12-1
12.2.1 File Review 12-1
12.2.2 Inspection Announcement 12-3
12.2.3 Inspection Equipment 12-3
12.2.4 Plant Surroundings 12-4
12.2.5 Visible Emission Ob-servations 12-5
12.2.6 Plant Entry 12-4
12.2.6.1 Warrants 12-7
12.2.7 Preinspection Interview 12-10
12.3 Field Proceudres 12-10
12.4 Post-Inspect ion Procedures 12-11
12.4.1 Post-inspection Interview 12-11
12.4.2 File Update and Report Preparation 12-11
12.5 Handling Confidential Business Information 12-12
12.5.1 Defining Confidential Business Information 12-13
12.5.2 Suggested Handling Procedures 12-13
12.5.2.1 Receipt of Confidential Business Data...12-13
12.5.2.2 Handling in the Office 12-14
12.5.2.3 Privileged Data and Report Preparation..12-14
12.5.2.4 Potentially Confidential Information....12-14
12.6 Use of Photographic Documentation 12-15
12.7 Reference 12-16
APPENDIX A WORKING FILES A-l
APPENDIX B FLOW CHARTING TECHNIQUES B-l
APPENDIX C VISIBLE EMISSION OBSERVATION FORM C-l
APPENDIX D OSHA REGULATIONS D-l
APPENDIX E NIOSH GUIDELINES E-l
APPENDIX F BASIC STATISTICAL METHODS F-l
vii
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1.0 INTRODUCTION TO BASELINE INSPECTION TECHNIQUE
The Baseline Inspection Technique has been developed to aid both the
source operators and regulatory agency inspectors to routinely evaluate air
pollution control equipment performance. Early diagnosis of emerging oper-
ating problems is essential to the prevention of permanent equipment damage
and the minimization of emissions.
The fundamental principle of the technique is that control device
performance diagnosis is most accurate when observed operating conditions are
compared with site-specific baseline data. The specific "historical" data
implicitly takes into account the numerous subtle factors which can influence
emissions. Baseline assessments avoid the errors potentially introduced by
extrapolation of published literature values to a given facility.
Control device instruments and field measurements are sometimes subject
to error; therefore, baseline diagnosis is based on sets of data comparisons
rather than reliance on just one parameter. Even when some of the data is
unavailable or suspect in quality, it is still possible to reach meaningful
and accurate conclusions using the remainder of the data.
The purpose of the Baseline Inspection Technique is to rapidly iden-
tify significant changes in performance and the possible reasons for the
changes. The technique does not necessarily provide definite evidence of
noncompliance with regulations, nor does it necessarily provide a specific
list of repairs required.
This manual contains chapters detailing baseline inspection techniques
for most of the commonly encountered equipment for air pollution control. In
addition, it includes chapters which discuss visible emission observation,
auxil iary equipment inspection, process equipment evaluation, inspection
safety procedures, and the administrative and legal aspects of regulatory
inspections.
1-1
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At this point 1t 1s suggested that persons utilizing the Baseline
Inspection Technique have a technical background—preferably engineering
experience. As with any work involving equipment, care should always be
exercised. Formal safety training is highly recommended for this activity
and for any field work involving air pollution control equipment. No single
technique will satisfy all source characteristics and inspection circum-
stances; whenever necessary inspectors and source operators should modify
the procedures outlined 1n this manual.
1.1 THE BASELINE TECHNIQUE
In the Baseline Inspection Technique the inspector should start at the
point of gas exhaust and proceed "counter" to the gas flow through to the
process equipment. Proceeding counter to the gas flow (backward through the
system) tends to minimize inspection time and reporting requirements and
maximize the amount of useful information obtained. More specifically, the
Information on effluents and control equipment gained early in the inspection
is not only the easiest to obtain, it can be used later either to narrow the
scope of the inspection or to terminate the inspection without completing the
most time-consuming part of the evaluation—namely, the process equipment.
The Baseline Inspection procedures are listed below 1n the suggested
temporal sequence beginning at the stack, proceeding backward through the sys-
tem, and ending with the process equipment. For regulatory agency personnel,
there are some additional preinspection and post-inspection steps required.
These are listed separately from the Baseline procedures and presented in
the last chapter of the manual entitled "Administrative and Legal Aspects of
Plant Inspections".
Baseline Inspection Procedures
Observe the stack effluent
Check the continuous monitor(s)
Measure the fan parameters and evaluate physical condition
Analyze the control equipment performance and physical conditions
Check the ventillation system performance and physical conditions
Evaluate process operating conditions
Check raw materials and/or fuels
Preinspection Steps (regulatory agency personnel only)
Review the source files
Schedule the inspection
Check the portable inspection equipment
1-2
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Observe the plant surroundings prior-to entry
Request entry to the plant
Interview plant official (s)
Postinspection Steps (regulatory agency personnel only)
Interview plant official (s)
Update source files
Prepare report
The Baseline Inspection approach offers particular advantage to regula-
tory agency personnel in that it is very consistent with the regulations. An
inspector must confirm compliance with a set of regulations which normally
consists of the following:
1. Opacity levels.
2. Operation and maintenance of continuous monitors.
3. Operation and maintenance of control devices.
4. Recordkeeping requirements for control devices.
5. Raw material characteristics (fuel surfur regulations).
6. Process operation rates (specific operating permit limits).
By proceeding counter to the gas flow, the inspector can determine compliance
with the first four regulations rapidly. At the same time, the performance
of the collector and fan provides a good indication of changes in raw material
characteristics or process load. Therefore, in many cases it is possible to
abbreviate inspections when compliance with items 5 and 6 is highly probably.
This helps agencies better utilize scarce inspection time and minimize
disruption of source personnel schedules caused by the inspection.
1.2 UNDERLYING PRINCIPLES
The Baseline Technique is based on five basic principles. The first
of these is that the operating characteristics and performance of each con-
trol system is initially assumed to be unique. This is because there are a
myriad of process variables and control device design factors, any one of
which can singly or collectively influence performance. Often it is dif-
ficult, if not impossible, to determine reasons why apparently similar units
opperate quite differently. To ensure the accuracy of the performance eval-
uation, the Baseline Techniques utilizes a comparison of present operating
conditions against a historical baseline level for that unit. Each variable
which has shifted significantly is considered a "symptom" of possible oper-
ation problems. During the inspection a number of comparisons are made and
1-3
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the symptoms are diagnosed. Acquisition of site-specific baseline data is
important to the success of the approach.
Experience during numerous previous Inspections has indicated that
many on-site monitors for air pollution control devices are either inaccu-
rate or have failed entirely. Due to this very common problem, sole use
of on-site monitors 1s unreliable. A second basic principle of Baseline
Inspections 1s that portable meters are used 1n Heu of permanent on-site
meters whenever feasible. The use of portable meters Includes basic qua-
lity assuance checks. During the Inspection both the portable meter and
permanent meter values are recorded. This provides a means to confirm
the operational .status of the onslte gauges.
The basic type of equipment necessary to perform a Baseline Inspec-
tion 1s listed in Table 1-1 along with an approximate estimate of cost
(1980 dollars). Regulatory agencies do not need a complete set for each
Individual and may need only one set for each local office. The most
expensive Items are the self-contained breathing apparatus and these
are required only 1f confined area entry Into environments conceivably
having oxygen deficiencies or toxic agents 1s anticipated3. The rest
of the safety equipment 1s quite economical and certainly each inspector
should be fully equipped.
Principle 3 of the Baseline Technique 1s simply that a^ much infor-
mation as possible will be used to evaluate performance so that problems
can be identified at the earliest time possible. Fan operating condi-
tions, fan physical conditions, and control device Internal conditions3
provide especially useful Indicators of developing problems and are
therefore Included within the scope of Baseline Inspection Technique.
The Inspection data 1s organized 1n a coherent fashion as it is ob-
tained. In this manner the Inspector can expand or abbreviate an inspec-
tion based on an examination of the initial data. And thus principle 4 is:
Diagnosis of operation problems 1s done by evaluation of sets of symptoms
characteristic of common problems. Reliance on sets of symptoms means
^Internal inspection of control equipment 1s not recommended unless each
individual performing the Inspection has received specific and detailed
training in safety procedures. See Chapter 11.0 SAFETY INFORMATION.
1-4
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TABLE 1-1. RECOMMENDED EQUIPMENT FOR
FIELD INSPECTIONS
Item Approximate cost (1980 dollars)
*1.
*2.
*3.
*4.
*5.
*6.
*7.
*8.
*9.
10.
11.
*12.
*13.
*14.
15.
*16.
*17.
*18.
19.
20.
*21.
*22.
23.-
24.
*25.
*26.
27.
28.
Hard hat
Safety shoes
Safety glasses (side shields)
Ear protectors
Oust masks
Cannlster type respirator
Coveralls
61 oves
Tool belt
Ropes and harness
Pry bar
Flashlight
Tape measure
Ouct tape
Stopwatch
Grounding cable
Differential pressure gauges
Gauge magnets
Pitot tubes
Velometer
Thermocoupl es
Multimeter
Tachometer
pH paper
pH meter
Combustion gas analyzer (03 4 C02)
Oxygen meter (for confined area entry)
Self-contained rebreather
(minimum of 2 required)
*Ind1cates equipment required for most inspection
ment
should be taken when necessary.
$ 2 to 5 5
$ 25 to $ 40
$ 5 to $ 100
$ 1 to $ 10
$ 10/100 masks
$ 15 to $ 30
$ 20
$ 3 to $ 8
$ 30
$ 50
$ 5
$ 10 to $ 15
$ 7 to $ 10
$ 5
$ 20 to $ 150
$ 25 to $ 35
$ 50 to $ 75
$ 5
$ 100 to $ 150
$ 200 to $ 400
$ 150 to $ 300
$ 10 to X 20
$ 100 to $ 200
$ 3 to $ 6
$ 100 to $ 400
$ 150
$ 500 to $ 700
$1000 to $1500
situations. Other equip-
that analyses can be completed even if several of the measurements can-
not be made at a given facility.
Principle 5 of the Baseline Technique is that the judgement of the
Inspector must take precedent over any procedures contained in this re-
port. Due to the numerous site-specific factors, an inspector must al-
ways remain alert regarding necessary changes in the scope of the inspec-
tion or procedures. For example, nothing should be attempted at the risk
of personal injury or damage to the equipment. Furthermore, it may be
necessary to alter certain analyses. Many inspectors will quickly evolve
to more sophisticated inspection techniques not discussed herein. Basic-
ally, it is impossiible to prepare a concise, reliable inspection manual
for all situations. There is no substitute for a well-trained, conscien-
tious inspector.
1-5
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2.0 ELECTROSTATIC PRECIPITATORS
The two most Important elements in the systematic inspection of an elec-
trostatic precipitator are power input data and plume opacity. The power
data, which is easily read off the transformer - rectifier (T-R) sets, can be
used to determine if the particle charging and migration is adequate. Both
of these are basic to the proper operation of any precipitator. It is not
sufficient, however, to simply maintain adequate power levels. Other fac-
tors such as partial bypass (sneakage) and reentrainment may lead to high
mass emission rates. Such conditions are detected by increased plume opacity.
Therefore, power input and opacity are complimentary diagnostic tools. With
these performance indicators it is possible to routinely evaluate operating
conditions by comparing present levels with baseline levels. Shifts off the
baseline indicate a need for a detailed inspection of precipitator components.
A brief discussion of the components common to most large electrostatic
precipitators3 is useful in developing an effective inspection approach. The
basic operating principles are introduced in the following section.
2.1 COMPONENTS AND OPERATION
The gas stream generated in the process equipment is delivered to the
precipitator at duct velocities of 50 to 75 ft/s. The gas stream must be
slowed in order to provide time to adequately treat the effluent; accordingly,
the entrance to the unit is typically an expansion chamber, often termed the
"inlet nozzle." Here the gas velocity drops more than an order of magnitude
down to 3 to 8 ft/s. Turning vanes and perforated plates are often used to
improve gas distribution across the face of the precipitator.
aThis section concerns the standard negative corona precipitators. For infor-
mation concerning the positive corona devices often used for collection of
organic aerosols, see The Air Pollution Engineering Manual, AP-40, 1973.
2-1
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The participate laden gas stream enters a number of parallel passages
comprised by large collection plates and a discharge electrode assembly.
There are many varieties of the latter, Including the standard weighted wires
assembly to the recent rigid frame and rigid electrode designs. Typical
widths of the passages are 9 to 12 1n. The discharge electrode system 1s
connected to a high voltage power supply which converts 440 to 480 volt A.C.
power to 15 to 70 kV D.C. power. Most new power supplies Include power
controllers to optimize power Input.
There are normally a number of power supplies on a given electrostatic
precipitator. Each of these feed a separate region of the precipitator,
termed a field.0 There are usually 2 to 10 fields 1n a series, and 2 to 8
fields in parallel on a unit. It is important for the agency inspector to
know the layout of fields and the field numbering system used at the plant.
The particulate matter passing through the energized electrostatic
precipitator is charged and then 1t migrates to the collection plate at a rate
dependent on the strength of the electrostatic field and the number of ions
on the particle (which depends on particle size). Some particles also are
collected on the negatively charged discharge electrodes. Both sets of
electrodes must be rapped on a regular basis to remove most of the accumulated
material.
The sol Ids dislodged during rapping fall into hoppers below the elec-
trodes. Most units have a pyramidal hopper. Such hoppers are usually equip-
ped with insulation, heaters and level indicators. Beneath each hopper is a
solids discharge valve which could be as simple as a rotary valve or as
sophisticated as a pressurized evacuation or a pneumatic evacuation system.
A basic understanding of precipitator operating principles is necessary
for the evaluation of the inspection results. Figure 2-1 1s a simple schematic
of the particle charging process. Beginning in block a, the application of
the high negative voltage to the discharge electrodes results in the very
rapid acceleration of electrons away from the discharge electrode and toward
the collection plate. The electrons are moving fast enough so that when they
field may include up to two separate bus sections.
2-2
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e
Trajectory of Particle
with
Positive Ions
Dust on Electron
Discharge
Electron
Trajectory of
Negative
Ions
G'
O
Discharge Electrode
Collection Electrode
Gas Molecule
Positive Ion
Negative Ion
Electron
Dust Particle
, Dust Layer
O on
I Collection)
Plate
Trajectory
of
Particle with
Attached Ions
FIGURE 2-1. Particle Charging and Migration
2-3
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collide with a gas molecule, that molecule-1 s Ionized. The original electron
plus the one freed during lonization are then accelerated again under the
influence of the strong electric field. This ionization process is repeated
many times 1n a very short distance, resulting in a large number of electrons
and positive gas ions. These positive ions return to the discharge electrode
carrying a small number of particles along (see Figure 2-1, block b). As the
electrons continue to move away from the discharge electrode, the electric
field strength decreases. The slower moving electrons are then captured dur-
ing the next encounter with a gas molecule (see Figure 2-1, block c). The
negative ion created then begins to move along the electric field lines to-
ward the collection plates. The negative ions are themselves captured on the
particles (Figure 2-1, block d); the larger the particle the more ions which
can be attached on the surface. Once the particles cross the turbulent zone
between the discharge and collection electrodes, they build up in a layer; the
charge is dissipated through the layer and onto the grounded collection elec-
trode. The ease by which the charge is dissipated through the dust layer is
inversely related to the resistivity.
The voltage applied to the discharge electrode (commonly termed the "sec-
ondary voltage") is one of the most important operating variables. If the
voltage is below what is called the corona onset voltage (see Figure 2-2), the
avalance process described earlier is not initiated. Under these conditions
the precipitator acts simply as a settling chamber and the particulate matter
removal is usually less than 40%. As the voltage goes up above corona onset
levels, smaller particles are charged more effectively and the electric field
which drives charged particles toward the collection plate is increased. The
voltage on the discharge electrodes should be as high as possible limited only
by excessive sparking between the electrodes. Most electrostatic precipita-
tors operate between 15 and 50 kV.
A second parameter of importance is the current passing from the discharge
electrodes to the collection plates (commonly called the "secondary current").
The secondary current and secondary voltage for each field as read off the
panels of the T-R set control cabinet are multiplied together to get the total
power input to the field as shown in Equation 2-1. This is conveniently re-
corded as watts (kV times mA equal watts). The total power to the precipitator
is the sum of power levels in each field, see Equation 2-2.
2-4
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750
500
i-
3
u
§ 250
SPARKING
CORONA ONSET
I
10 25 40
Secondary Voltage, Kilovolts
FIGURE 2-2. Voltage-Current Plot
2.1.1 Moderate and High Resistivity Conditions
The total amount of power per unit volume of gas being treated is often
a good indirect indication of the degree of particle collection. The greater
the power input, the greater the collection efficiency. The general relation-
ship between power input and penetration (1 minus the collection efficiency)
is shown in Equation 2-3.
x S,
Eq. 2-1
where PI » power to field 1, watts
Sv * secondary voltage of field 1, kilowatts
Sc » secondary current of field i, milliamps
2-5
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Eq. 2-2
t .
where
Eq. 2-3
a fractional penetration
K.J * constant
Pc » corona power, watts
V « fl ow rate ACFM x 103
The mass penetration power Input curve which results from Equation 2-3
is illustrated in Figure 2-3. The Kj constant is dependent on many factors
including the particle composition, surface characteristics, and size dis-
tribution. The magnitude of K^ is lowest for difflcult-to-collect materials.
0.8
c
o
5 o-6
s-
4->
0)
0)
a.
* 0.4
o
*j
^ 0.2
200 400 600 800
Corona Power, Watts/103 ACFM
FIGURE 2-3. Penetration as a Function of Power Input and
2-6
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There are certain practical factors which modify the shape of the pene-
tration-power input curve in actual installations. The low gas velocities
and long retention times result in effective settling of large particles.
Therefore, even with a zero power level, the penetration rarely exceeds 0.6
(40% collection efficiency). In each precipitator, there is a small quantity
of gas which successfully bypasses the treatment zone. Due to this untreated
gas the penetration never reaches zero. There are also emissions due to re-
entrainment which are only partially affected by power input. Due to these
factors, a hypothetical curve for an actual Installation would appear as
shown 1n Figure 2-4. The two bottom areas represent the penetration due to
sneakage and reentrainment. In a given unit these values could be considerably
greater than shown.
0.020
c
o
+J
(Q
0-015
0.
It)
o
0.010
0.005
\
K-0.5 \ Ki=(X3
•
%
%
\
Kj=0.1 \
t
200 400 600
Corona Power, Watts/103 ACFM
800
FIGURE 2-4.
Influence of Reentrainment and Sneakage on Penetration
2-7
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Due to the strong Influence of the Kj parameter on the position of the
curve and the possible Influence of non-power related emission modes, it is
not presently possible to define a universally applicable penetration power
input curve. These correlations must be developed for each installation sep-
arately. This is the only means to adequately account for the K-j parameter.
In some plants the particle characteristics may vary enough to cause substan-
tial variations in the value of K-f.
The use of power-emission correlations plus the evaluation of secondary
voltage and current data used to calculate the power provide powerful tools
for the source and agency Inspectors. Unfortunately, not all precipitators
have secondary voltage meters and a few do not even have secondary current
meters. In such cases (often with older units), similar analysis can be done
with the primary current and primary voltage meters which are almost always
avail able3- The primary meters monitor the power input to the transformer of
the power supply. These meters are a less direct Indication of electrical
conditions in the electrode zone.
2.1.2 Low Resistivity
When the resistivity of the dust layer 1s low, there is no general rela-
tionship between the power input and the penetration. Particulate emissions
are primarily influenced by the superficial velocities through various por-
tions of the predpltator, the rapping intensities, the rapping frequency,
and the precipitator aspect ratio.
2.2 INSPECTION PROCEDURES
The inspection begins with the stack visible emission observation. Com-
pliance with visible emission requirements 1s determined and any change in
opacity from typical levels 1s noted. The presence of regular "puffs" should
be noted and timed. Next, the data on the output consoles of any transmis-
someters and gas monitors should be obtained. Again, the presence of spikes
should be logged and the Intervals between spikes estimated. The transmis-
someter 1s usually 1n a more favorable location and is more sensitive to
spikes than the visible emissions observer. The present level and trend in
opacity over the last eight hours should be checked. Also, the inspection
should note the frequency and levels of the automatic span and zero checks.
awhen using primary side data, the power input 1s usually multiplied by the
Power factor. For older installation a factor of 0.75 is often assumed.
2-8
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An oxygen content measurement 1n the ESP exit breeching is useful in
determining if there is a serious air Inleakage. Temperature readings at the
exit are also useful for confirming the magnitude of the inleakage.
These preliminary steps accomplished before the actual inspection of the
Precipitators take about 1/2 to 1 hour. It is time well spend since this
data can be used to narrow the scope of the inspection.
The inspector then proceeds to the electrical cabinets which are connec-
ted to each of the transformer-rectifer (T-R) sets. For each T-R set there are
a set of meters on the outside of the cabinet. The meters generally have the
following units:
primary voltage - volts, A.C.
primary current - amps, A.C.
secondary voltage - kilovolts, D.C.
secondary current - milliamps, D.C,
spark rate - number per minute
The readings should be written down in the same order as the power supplies
are arranged on the precipitator.1*2 For example, assume there is a precipi-
tator with 8 power supplies arranged 1n the order shown 1n Figure 2-5.
CHAMBER
FIGURE 2-5,
CHAMBER B
Precipltator Having Two Chambers Each with Four Fields
1n Series and Two Bus Sections per Field
2-9
-------
For the first chamber the Inspector would record all the electrical
parameters on fields 1 to 4 in order. Then the values on the next chamber
would be recorded starting with 5 and ending with 8. The reason for this
approach is that the inspector must determine if the normal trends are pre-
sent in order to confirm the prevailing resistivity range. In the large major-
ity of the predpitators which have moderate resistivity, the secondary
current is very low- 1n the-Inlet fields and Increases progressively 1n the
subsequent fields. The trend line 1s shown 1n Figure 2-6. The secondary
voltages are usually slightly higher 1n the Inlet field and decrease toward
the outlet field. This trend line 1s shown 1n Figure 2-7.
When the resistivity 1s low, all of the fields have high secondary cur-
rents which approach the current limit of the T-R set. Sparking 1s very low
in all fields and may be absent entirely from the outlet fields. When the
dust resistivity is high the secondary currents are low throughout the chamber,
however, there may be a slight Increase going from Inlet to outlet. Sparking
is usually but not always high when the resistivity 1s high.
With the electrical data logged 1n the proper order, 1t is possible to
quickly scan the data. Data analysis can be done most effectively by plotting
the secondary voltage and current plots as shown 1n Figures 2-6 and 2-7. The
line marked baseline is the data recorded earlier, generally during a stack
test. This sort of simple plot can be used to answer one very basic but vital
question, namely, has there been a shift 1n all the values 1n each field or
have only a few fields changed? The latter normally implies some localized
problem such as rapper failure, malalignment, solids buildup, Insulator leak-
age, and air Inleakage. If all the fields have changed, then the resistivity
has probably changed. Based on the analysis of these plots, the remainder of
the Inspection can be arranged. If the total power Input has not changed sig-
nificantly since the baseline period and the opacity has not Increased signi-
ficantly, then there 1s probably no need for further Inspection at this time.
Table 2-1 Illustrates some of the ways the inspection approach can be ad-
justed to respond to possible signs of performance problems. If there is a
need to check the rappers, the Inspector should use whatever hearing protec-
tion and respirators3 are appropriate. The quickest way to check rappers 1s
dFugitive gas leaks on predpitators operated under positive pressure can
lead to high concentrations of 503.
2-10
-------
to have an electrician access the rapper control cabinet and manually activate
each set of rappers. The more patient inspector may simply let the rappers
activate on their normal schedule and confirm that each sounds normal. For
large units, the latter approach can be quite tedious. Another approach, used
by a number of operators, is to precariously balance a washer (or penny) on the
side of each rapper. When returning several hours later, one need only find
the rappers that failed to shake the washer off.
1200
1
Q.
•.•
000
800
600
400
200
1 » • *
,
Baseline Values ^^
^*^'°''
vr^ + + * Present Values
o-- -•'
i i i i
1234
Field
FIGURE 2-6. Comparison of Present and Baseline Values for Secondary Current,
Four Field Unit
FIGURE 2-7.
45
40
£ 35
o
^30
25
20
Baseline Values
— D
Present Values
1234
Field
Comparison of Present and Baseline Values for Secondary Voltage,
Four Field Unit
2-11
-------
The Intensity of rapping should be checked whenever puffing is ob-
served3. For compressed air type units, the intensity is proportional to
the air pressure (usually gauges are available on the air lines leading to
the rappers).5 For other types of rappers, the intensity is controlled by
either the voltage or current in the rapper power lines.
TABLE 2-1. INSPECTION ORIENTATION BASED ON INITIAL REVIEW
OF ELECTRICAL SET DATA
Symptoms
Electricalset
Other
Inspection items
Low secondary currents
(one or more fields)
Reduced power input in
all fields
Increased opacity
Increased opacity
High power input in all
or most fields
Puffing
Low secondary voltage in
one or more fields
Increased opacity
Reduced voltages in a
number of fields
Higher 03 levels
Check collection plate
rappers
Check for changes which
could lead to high par-
ticle resistivity (fuel
sulfur content, temper-
ature change, ash com-
position change)
Check rapper intensity
and sequence, especially
on inlet and outlet
fields; also check for
factors which would give
low particle resistivity
Source personnel should
check insulators during
next outage; agency per-
sonnel confirm that in-
sulator heater and pent-
house blowers are
operating
Check for air inleakage
around hatch and hoppers
For most precipitators it is difficult to confirm quickly that solids
are being discharged. If this can be checked safely and reasonably quickly,
it is a worthwhile task. If no solids are being discharged over a 10 to 30
minute period, then either a solids discharge system problem has developed
(with potentially serious consequences) or the precipitator is in a very
advanced state of deterioration. In either case immediate attention is
warranted.
2-12
-------
There is occasionally a need to make an internal inspection of at least
part of the precipitator to identify an operating problem. An internal
inspection is usually done only by the source personnel; however, in rare
instances the agency inspector may also find one useful3. Such inspections
should be done in the company of source personnel completely familiar with
safety procedures and only during major outages when the units have been
cooled, purged, and deenergized. Once inside the region(s) exhibiting un-
usual electrical readings, an observer would check for any or all of the
following items:
1. Deposits on collection plates (should be 1/8" to 1/4" and dry),2
2. Wire plate alignment (should be +_ 1/4", visually should not be able
to see out-of-al ignment electrodes),2
3. Presence of "clinkers" at bottom of electrodes,
4. Presence of broken wires,
5. Corrosion of electrodes, and
6. Eroded or plugged gas distribution plates.
The importance of conducting the internal inspection safely cannot be over-
emphasized. Personnel should not work alone, should have adequate respira-
tors, should use grounding strips, and should follow all lockout procedures.
After each major outage, source personnel should perform an air load
test on each field and record the results of the test in a convenient location.
This test will clearly identify uncorrected malalignment or the presence of
foreign objects left by personnel inside the unit. Also insulator high
voltage leakage can be identified. The agency inspector should request such
records whenever these problems are suspected.
The inspection of the precipitator should also include at least a brief
review of the operating records kept by the source. Such records should
obviously include the T-R set electrical data (hopefully analyzed by the
operator, not just filed away). Also, the records should describe any signif-
icant maintenance work such as the addition of wire shrouds, adjustment of
rappers, and the removal of wires. Concerning the latter item, there should
^Internal inspections are not recommended unless the inspector has received
specific and detailed training in confined area entry.
2-13
-------
be a drawing available Indicating where wires had been removed and where on
any given wire the failure had occurred. Based on the pattern of failures
an operator can determine 1f there 1s some underlying problem leading to wire
failure, such as malallgnment. Obviously such problems should be corrected
before the wire 1s replaced, otherwise the new wire will also soon fall. With
such records both the source personnel and agency Inspector can more easily
determine what 1s reasonable and necessary to maintain continuous compliance.
2.3 REFERENCES
1. Richards, J., Hawks, R. and Szabo, M., "ESP Inspection Procedures -
Operator and Agency Roles in Ensuring Continuous Compliance", In: Proceed-
ings of Specialty Conference on Operation and Maintenance of Gas Cleaning
Equipment, Air Pollution Control Association, April 1980, pp 41-50.
2. Ahrens, J., "A Coordinated Approach by a Central Group to Maintain
Precipitator Compliance", In: Proceedings of Specialty Conference on
Operation and Maintenance of Gas Cleaning Equipment, Air Pollution
Control Association, April 1980, pp 51-60.
3. Neundorfer, M., " Electrode Cleaning Systems: Optimizing Rapping Energy
and Rapping Control", In: Proceedings of the Symposium on the Transfer
and Utilization of Particulate Control Technology, 1979.
2-14
-------
3.0 FABRIC FILTERS
In fabric filter systems participate is collected within a dust cake
supported on either a woven or felted fabric. The fundamental collection
mechanisms include ^impaction, interaction, diffusion, and in some cases
electrostatic attraction. The latter has not been fully studied, therefore,
its importance on a specific unit is difficult to quantify.1 The collection
efficiency is extremely high and any emissions which do occur are thought to
be due to leaks through bag tears across poorly seated gaskets, cracks in
welds, or high-velocity pinholes. As a result, the typical size efficiency
curve does not have a strong particle size dependence.2.3 p0r this reason, the
outlet particle size distribution is often similar to the inlet distribution.
3.1 COMPONENTS AND OPERATION
The manner by which the fabric is cleaned and the means of mounting the
bag in the housing are the two principal features used to classify fabric
filters. For the purposes of these reports, the four broad categories listed
below will be discussed separately.
Pulse jet
Reverse air (outside-to-inside flow)
Reverse air (inside-to-outside flow)
Shakers
Obviously there are a number of other types. For information concerning
operating characteristics and components, see References 4 and 5.
3.1.1 Pulse Jet Fabric Filters
Example pulse jet filters are depicted in Figures 3-1 and 3-2. The bags
are cylindrical and are supported on an interior cage which is suspended from
the tube sheet. The particulate laden gas stream is admitted in the hopper
area. The particulate is collected on the outside surface of the felted
bags. The cleaned gas passes up the inside of the bags and into the clean
air plenum above the tube sheet. Above each row of bags there is a compressed
air supply line called a "blow tube." The line has either a hole or nozzle
3-1
-------
FIGURE 3-1. Pulse Jet Filter
(Courtesy of Environmental Elements Corporation)
FIGURE 3-2. Pulse Jet Filter; Close-Up View of Air Manifold,
Blow Tube, and Venturi
(Courtesy of Environmental Elements Corporation)
3-2
-------
directed downward toward each bag. At regular intervals, a solenoid activated
valve on each tube is opened momentarily, allowing a pulse of air to enter
each bag in that row. The shock wave dislodges the cake. By this means,
cleaning can be done without taking the unit off-line. The dislodged dust
is collected within the hopper and is discharged through a rotary valve or
similar device.
The pulse jet collectors normally operate at an air-to-cloth ratio (gas
flow 1n acfm divided by available filtering cloth area) of 4 to 8, well above
other collectors. Felted type material is used almost exclusively.
3.1.2 Reverse Air (Outside-to-Inside Flow)
These collectors tend to be single compartment, smaller units similar to
the unit shown in Figure 3-3. The bags are supported on an inner cage which
is again suspended from an upper tube sheet. The gas stream enters on the
lower side of the hopper area and the gas flow pattern is the same as for the
pulse jet collectors discussed earlier.
FIGURE 3-3.
Reverse Air Fabric Filter (outside-to-inside
(Courtesy of the Carter Day Company)
3-3
flow)
-------
Cleaning of the bags is usually done.by a rotating arm located above the
tube sheet. A small fan pulls filtered air for injection through the rota-
ting arm and down through the bag.
These types of collectors usually operate at air-to-cloth ratios of 1
to 4. Unlike pulse jet collectors, woven fabrics are generally used.
3.1.3 Reverse Air (Inside-to-Outside Collectors)
The bags in this type of collector are mounted in a lower tube sheet and
suspended from the roof of the compartment. Cages are not generally used,
however, some bags are manufactured with anticollapse rings to aid dust dis-
charge during cleaning. Gas flow 1s up through the bags, passing from the
inside to the outside.
The bags are mounted in two or more compartments. Periodically, the
chambers are Isolated by means of dampers and filtered air is passed through
from the outside of all the bags in the compartment.
Either a thimble or snap ring assembly is normally used to attach the
bags to the tube sheet (Figure 3-4). These attachments are a common source
Bag
"*~ Thimble—*
Stainless
D-^-Steel
Clamp
Cell Plate
Thimble Connection
Cell Plat
late-J[
Cuff with
Spring
"•"Steel"-1
Band Cell
Snap Band Connection
FIGURE 3-4.
Bag-Cell Plate Attachments for Reverse Air
(inside-to-outside) Baghouses
3-4
-------
of operating problems. An adjustable hook or cap is used at the top of the
bag to provide proper bag tension, a critical factor. These types of fabric
filters often have precleaners and/or blast plates to reduce the amount of
large sized abrasive particulate reaching the lower portion of the bags.
Because of the gentle cleaning action and the type of bag mounting, this
system can accept glass-fiber bags. For this reason, most high temperature
(>400°F) units are of this type. Air-to-cloth ratios range from 0.5 to 3.0.
3.1.4 Shaker Collectors
These collectors resemble the reverse air (inside-to-outside flow) units
with the exception that fabric cleaning is done by a shaker motor instead of
reverse air. Cleaning is done compartment-by-compartment. Gas flow is up
through the bags and outside to the "clean side". Typical air-to-cloth ratios
are 1.0 to 3.0. Woven fabrics are used almost exclusively.
3.2 INSPECTION/MAINTENANCE
The inspection of all fabric filters begins with the visible emission ob-
servation. Of particular interest is the presence of short-term spikes during
the cleaning of a specific compartment (reverse air units) or of a specific
row (pulse jet units). Oxygen content of flue gas downstream of fabric
filters is a useful indicator of ambient air inleakage problems which could
lead to condensation on the bag. Pitot traverse data and/or fan data can be
used to estimate the actual air-to-cloth ratio, a very important operating
variable. Emissions are directly related to actual air-to-cloth ratio.6»?»8
3.2.1 Pulse Jet Filters
Each of the valves (Figure 3-2; which supply the blow tubes should be
checked to confirm that adequate cleaning of each row of bags is being done.
A firm "thud" should be audible if the valve is activated and is operational.
The row being cleaned is easily identified by lightly resting a hand on the
valve. Normally the rows are cleaned starting at one end and proceeding
sequentially to the other end. Rows not being cleaned should be marked and
recorded. If this condition has persisted for some time, it is probable that
a substantial dust cake has accumulated on the outsides of the bags. This
could lead to somewhat higher gas velocities and therefore higher particulate
emissions through the remaining rows.
3-5
-------
If all of the valves sound weak or if none are being activated, then
the compressed air supply should be checked. The pressure gauge on the
cleaning air manifold is usually in the range of 90 to 120 psig.a Lower
values may indicate inadequate cleaning. In rare cases the supply line to a
set of valves is inadvertently shut off.
The cleaning air supply tank should have a small drain at the bottom to
periodically remove oil and water. Also the main air line coming to the
pulse jet filter should have a dryer (type necessary depends partially on
climate). Without provisions to remove water and oil, the bags can be "wetted"
from inside leading again to a higher than anticipated static pressure.
The presence of any short-term puffs with a duration of 1 to 3 seconds
is indicative of small holes or tears in the bags. When the row having the
damaged bag(s) is pulsed, the dust cake bridging the hole is temporarily
removed, leading to a short-term high emission rate until the hole is "healed"
by a newly formed dust cake. Large holes and tears often do not reseal, thus
leading to a continuous emission. The row causing short-term puffs should be
identified by determining which row is being pulsed at the time of the spike.
The static pressure drop across the pulse jet collector should be checked
by removing*5 the lines to the existing monitor and clearing the tap hole.
Portable gauges supplied by the inspector can then be used to accurately
measure the static pressure drop. High values indicate higher than normal
gas flow rates, partial blinding of the fabric, or inadequate cleaning. Low
values suggest large tears or serious ambient air infiltration on the clean
side. The static pressure drop is not a very sensitive indicator of bag tears
and holes.9 If a detectable drop in static pressure drop has occurred, it is
probable that a substantial fraction of the gas stream passes through the
holes rather than the filter cake.
Severe air inleakage is often due to poorly seated access hatches on the
top of the collector. Usually the air inleakage can be easily heard and
felt when the problem is severe.
aSome brands are designed to operate at a much lower pressure, 15 to 20 psig.
In these cases, the amount of air per square foot of bag surface is normally
greater than the conventional type pulse jet filter.
"Often plant rules require that this is done only by plant personnel.
3-6
-------
A pulse jet collector must be locked- off before an internal inspection
can be done. Once this is safely done, the clean side hatches can be removed
to inspect the blow tubes and the Venturis (if present). Clean side deposits
indicate poor collection efficiency. During the early stages of equipment
deterioration, poor efficiency can only be identified by examining deposits
on the underside of the blow tubes, directly above each bag.
3.2.2 Reverse Air (Outside-to-Inside Flow)
The rate of solids discharge from the collector should be checked by ob-
serving the amount of solids being discharged to a waste bin or being transpor-
ted along a screw conveyor. Solids discharge is relatively continuous with
this type of collector, therefore, the rate of discharge needs to be observed
for 1 to 5 minutes. Lower than normal rates can indicate any of the following:
1. Failure of the reverse air fan,
2. Failure of the internal cleaning arm,
3. Failure of the rotary discharge valve below the hopper,
4. Solids bridging within the hopper,
5. Reduction in the quantity of process gas treated due to
serious air inleakage,
6. Substantial penetration through the bags, and
7. Low particulate matter generation rate at the process source.
All of these, with the exception of No. 7, are serious operating problems
which demand the inspector's immediate attention. The first three conditions
can be confirmed quickly, simply by observing the equipment. For combustion
sources, air inleakage can be identified by measuring flue gas oxygen content
levels at various locations before and after the collector. On other sources,
potential sites for air inleakage such as flanges, welds, solid discharge
valves and hatches should be checked for audible air inleakage.
The static pressure drop across the collector should be evaluated using
the same procedure discussed earlier. Higher than normal levels again suggest
inadequate cleaning or blinding of the outer bag surface due to moisture or
oil entering with the gas stream. Low static pressure drops may be caused
by numerous tears or holes in the woven fabric or by poorly attached bag
3-7
-------
cage assemblies at the tube sheet. As in the case with pulse jet units,
there must be numerous holes and/or tears before there is a noticeable drop
in static pressure.
Internal inspection should be done only when the unit (fan, reverse air
blower, cleaning arm and rotary valve) is locked off and all safety require-
ments are satisfied. Bag-to-bag abrasion, often caused by bent cages, can
be identified by observing the bottom of the bags from the hopper access
hatch.3
3.2.3 Reverse Air (Inside-to-Outside Flow)
The solids discharge from a typical multicompartment reverse air fabric
filter 1s Intermittent. There is significant solids discharge only during a
short period while each of the compartments is undergoing cleaning. The dis-
charge rate should be checked during one or more cleaning cycles. Reasons
for inadequate solids discharge are the same as those discussed earlier for
Reverse Air (outside-to-inside flow) collectors.
Static pressure drop across the entire collector should be measured with
portable gauges. There should be no need to measure the pressure drop across
each compartment since these must be the same. If there are compartment-by-
compartment flow resistance differences, the flow of gas will automatically
adjust to give equal static pressure drops.
This type of collector is often used for high temperature service. In
such cases, the Inlet gas temperature should be measured using a portable
thermocouple and then compared with the on-site instrument. High temperatures
are of concern only if the maximum rated temperature of the fabric being used
is exceeded. Low temperatures Indicate the potential for condensation of
volatile compounds and/or water on the interior bag surfaces.
One problem often leading to low temperature levels is air inleakage up-
stream from the collector. On combustion sources this can be evaluated by
measuring the flue gas oxygen content. Significant deviation from normal oxy-
gen levels combined with low gas temperatures may indicate serious air inleak-
age.
"CAUTION: Opening of a hopper access hatch must be done with extreme care
due to the potential for hot, free flowing solids behind the hatch which
could lead to serious burns and/or suffocation.
3-8
-------
Internal inspection can only be done when one or more of the compartments
are isolated. Even then extreme care is warranted since most such collectors
have some leakage of gas across the isolation dampers. Unless the compartment
is pressurized by a clean air fan or the entire collector has been purged
out, it is recommended that the inspector use a self contained rebreather or
air-line respirator.3
If the clean side deposits are uniform and substantial (>!" to 2" deep
throughout) it is very difficult-to determine the source or sources of the
problem. Normally most bag problems in this type of collector occur near the
bottom, therefore, this area should be checked first. Common problems include
bag abrasion on the opposite side from the inlet and cutting of bags on sharp
thimbles. The latter may be aggravated by excessive tension which causes the
fabric to rub against the sharp edge of the thimble during reverse air clean-
ing. Low bag tension can cause creasing of the bag at the bottom which
results in abrasion and pinholes.
Solids buildup in bags can be checked by grabbing the bag just above the
thimble. If the bag is full of solids, then no gas has been passing upward.
If the hopper below is full, gentle massaging of the fabric will not be
successful in cleaning the bag.
3.2.4 Shaker Collectors
This type of fabric filter is entirely analogous to the Reverse Air
(inside-to-outside flow) collectors with the exception of the cleaning
mechanism. Inspection is done in a similar fashion.
Due to the more strenuous cleaning action, bag tension is even more
important. Excessive tension can result in bag cutting on the thimbles or
bags being yanked free of the thimble clamp. These types of fabric filters
also suffer most bag problems near the bottom, close to the tube sheet.
Leaks around poorly seated snap ring bags may also reduce collection
efficiencies. Out-of-round rings or poor installation can cause these prob-
lems. The snap ring type of bag attachment is also vulnerable to inlet
abrasion since there is no thimble to protect the bags from the turning gas
stream.
^Internal inspections are not recommended unless the inspector has received
specific and detailed traTnThg in confined area entry safety procedures.
3-9
-------
3.3 REFERENCES
1. Donovan, R. P., Turner, J. H., and Abbott, J. H., "Passive Electrostatic
Effects in Fabric Filtration," In: Second Symposium on the Transfer and
Utilization of Participate Control Technology, vol. i.ycontrol of
Emissions from Coal fired Boilers. VerutittH; >• P-» Armstrong, ^. A.,
and Durham, M.editors, U.S. Environmental Protection Agency Publication
No. 600/9-80-039a, September 1980, pp. 476-493.
2. Turner, J., "Extending Fabric Filter Capabilities," J. of the Air Pollu-
tion Control Association, Vol. 24, No. 12, 1974.
3. Ensor, D. S., R. G. Hooper, and R. W. Schech, "Determination of the
Fractional Efficiency, Opacity Characteristics, Engineering and Economic
Aspects of a Fabric Filter Operating at a Utility Boiler," Electric Power
Research Institute Report, EPRI FP-297, November 1976.
4. Billings, C., and Wilder, J., "Handbook of Fabric Filter Technology,
Vol. I," APTD 0690, NTIS PB200648, GCA Corp., Boston, 1970.
5. Theodore, L., and Buonicore, A. J., Industrial Air Pollution Control
Equipment for Particulates, CRC Press, Cleveland, 1976.
6. Hall, R. R., R. Dennis, and N. F. Surprenant, "Fibers, Fabrics, Face Vel-
ocity and Filtration," In: A Specialty Conference on the User and Fabric
Filtration Equipment III. E. R. Fredrick, editor, APCA Specialty Conference
Proceedings, 1978, pp 156-169.
7. Dennis, R. H. A. Klemm, "Verification of Projected Filter System Design
and Operation," in Symposium on the Transfer and Utilization of Particulate
Control Technology. Vol. 2, Fabric Filters and Current Trends in Control
Equipment. Venditti. F. P.. J. A. Armstrong, and M. Durham. Editors. U.S.
Environmental Protection Agency, Publication No. 600/7-79-044b, February
1979, pp. 143-160.
8. Leith, D., M. W. First, M. Ellenbecker, and D. D. Gibson, "Performance of
a Pulse-jet Filter at High Filtration Velocities," In: Symposium on the
Transfer and Utilization of Particulate Control Technology: Vol. 2.
Fabric Filters and Current Trends in Control Equipment, Venditti.FT P.,
J. A. Armstrong, and M. Durham, editors, U.S. Environmental Protection
Agency, Publication No. 600/7-79-044b, February 1979, pp. 11-26.
9. Engineering-Science, Inc., "An Investigation of a Fabric Filter Emissions
Correlation," Final Report to the U.S. Environmental Protection Agency,
Contract 68-01-4146, Task 69, May 1980.
3-10
-------
4.0 WET SCRUBBERS
Wet scrubbers comprise a very large and diverse set of control devices,
all of which share similar particle collection mechanisms. Inertia! impaction
and Brownian diffusion are the dominant collection mechanisms in most conven-
tional scrubbers. Accordingly, these scrubber systems generally exhibit
strong particle-size-dependent performance. Among scrubber types there are
substantial differences with regard to the effectiveness of the mechanisms,
the greatest differences occuring in the particle size range of 0.2 to
2.0 MinA- Particles in this size range scatter light effectively, therefore,
plume opacity is high when the particulate penetration in this size range is
high. For this reason, opacity is a good diagnostic tool. Unfortunately,
it is not always easy to evaluate the actual opacity due to condensed water
interference.
A second indication of high particulate penetration is a decrease in the
static pressure drop. Usually when the pressure drop is high, the inertia!
impaction conditions are optimized and the penetration in the 0.2 to 2.0 micron
range is minimized. Pressure drop can be accurately measured, therefore,
it is a very useful diagnostic tool. If either the opacity or pressure drop
has changed significantly since the baseline period, a more detailed inspec-
tion is warranted.
4.1 COMPONENTS AND OPERATION OF PARTICULATE SCRUBBERS
I
Because of their diversity, it is difficult to classify scrubbers into
distinct generic categories. Scrubbers that are grouped on the basis of
similar mechanisms may have greatly varying geometric arrangements. In this
discussion major categories of scrubbers are arranged in an approximate
ascending order of performance capabilities and energy requirements.
4-1
-------
The scrubber liquid may be used for particle collection in several
distinct ways. The most common is generation of droplets, which are then
intimately mixed with the gas stream. Particle collection can also be achieved
on water layers or sheets surrounding some form of packing material. In this
case the gas stream is forced to negotiate an intricate path around the
individual packing elements. The high velocity passage of gas may also
generate "jets" of li,quid in which particle collection may occur.
4.1.1 Preformed Spray Scrubbers
Preformed spray scrubbers require the least energy of the various scrub-
bers and they consequently allow the highest particulate penetration, especi-
ally of small-diameter particles. Most preformed spray scrubbers are highly
efficient only for particles larger than 10 umA diameter and are relatively
less efficient for particles smaller than 5 M^A diameter.
A spray tower is the simplest type of preformed spray scrubber, consis-
ting of a chamber containing an array of spray nozzles (Figure 4-1). Parti-
culate-laden gases pass vertically up through the tower while the liquid
droplets fall by gravity countercurrent to the gas flow. Particle collection
is primarily by impaction. While the spray scrubber has low particle remo-
val capability, it is often useful for treating effluent gas streams having
high mass loadings of large diameter particulate matter.
The cyclonic spray tower is similar to the spray tower scrubber except
that the gas stream is given a spiral motion. In one typical configuration
particulate-laden gases enter the scrubber vessel tangentially at the bottom
and pass upward in a spiral motion around a centrally located array of spray
nozzles. Droplet migration is crosscurrent to the gas flow. A vane type
cyclonic scrubber utilizes a system of vanes rather than a tangential inlet
to impart cyclonic motion. Other cyclonic scrubbers consist of multiple
miniature cyclone tubes, each with a separate liquid supply. This design
utilizes a downward flow pattern for the gases in contrast to the typical
upward flow. Cyclonic spray towers generally operate with a static pressure
drop of 4 to 8 in. W.G. Penetration of particles less than 2 wnA in diameter
is typically quite high.*
4-2
-------
.- __
A A
A A
*
A A A
A A A
I
r
GAS OUTLET
DEMISTER
LIQUOR INLETS
GAS INLET
LIQUOR OUTLET
FIGURE 4-1. Spray Tower.
4.1.2 Tray-Type Scrubbers
A tray-type scrubber typically consists of a vertical tower with one or
more perforated plates mounted transversely inside. In such a scrubber the
liquid flows from top to bottom while the gas flows from bottom to top.
Gases in the tray-type scrubber mix with the liquid as it passes through the
openings in the plates.
The perforated plates of a tray-type scrubber are often equipped with
impingement baffles or bubble caps over the perforations forming impingement
surfaces. As the gas passes upward through a perforation, it is forced to
make a 180-degree turn into a layer of liquid. The gas bubbles through the
liquid, causing the particulate to impinge against the liquid sheet. The
4-3
-------
impingement baffles are below the liquid level on the perforated plates and
for this reason are continuously washed clean of collected particles.
Penetration through a typical impingement plate is low for particles larger
than 1 MmA2, but penetration of submlcrometer particulate is higher than with
some higher-energy scrubbers. Pressure drop through a typical baffle plate
is roughly 1.5 in. W.G. per stage. Addition of plates increases the scrubber
pressure drop, but does not proportionally decrease the penetration of
submicrometer particulate.
4.1.3 Packed-Bed Scrubbers
In the typical packed-bed scrubber the liquid is introduced at the top
of the packed bed and trickles down through 1t; the packing breaks down the
liquid flow into a film with a large surface area. The liquid can also be
introduced concurrent with gas flow or crosscurrent with gas flow. Packing
materials include raschig rings, pall rings, berl saddles, tellerettes,
intalox saddles, and materials such as crushed rock. Packed beds are also
constructed with metal grids, rods, or fiberous pads. These scrubbers are
often used for gas transfer or gas cooling, both of which are facilitated by
the large liquid surface area provided on the packing.
Plugging of a bed can occur if the gas to be treated is too heavily laden
with solid particles. Moving-bed scrubbers have been developed that have
less propensity for plugging. These scrubbers are packed with low-density
plastic spheres, which are free to move within the packing retainers.
Packed-bed scrubbers are reported to have low penetration for particle
sizes down to 3 MmA and can sometimes remove a significant fraction of par-
ticulate in the range of 1 to 2 ^mA. The standard countercurrent arrangement
requires the greatest liquid flow and can best handle heavier loadings.
Crosscurrent packed-bed scrubbers require much less liquid flow, usually
operate at lower static pressure drops, and rarely suffer from plugging.
Concurrent packed-bed scrubbers are reportedly more efficient than other
packed-bed scrubbers for the smaller particulates, but they typically operate
at higher pressure drops.
4-4
-------
4.1.4 Venturi and Orifice Scrubbers
Venturi and orifice scrubbers are perhaps the most common particulate
removal devices, in part because they allow lower penetration of small parti-
cles than most other types of scrubbers. These scrubbers accomplish supe-
rior particulate collection by generating small liquid droplets in the turbu-
lent zone in a manner that creates a high initial relative velocity between
the droplets and the particulate. Inertial impaction capture of particulate
by the scrubbing liquid is more efficient in these highly turbulent proces-
ses, but a price is paid in energy consumption to achieve the low penetra-
tion.
4.1.4.1 Venturi Scrubber - The simple venturi scrubber, often called a gas-
atomizing spray scrubber, consists of a series of sprays upstream from a
converging and diverging "throat" section (Figure 4-2). As the gas approaches
the venturi throat, the velocity and turbulence increase. The high gas
turbulence atomizes the liquid into small droplets and increases interaction
between the droplets and the particulate. Pressure drops in venturi scrubbers
can range from less than 4 to 100 in. W.G.
4.1.4.2 Variable Throat Venturi Scrubbers - Pressure drop and venturi per-
formance are partially dependent on gas velocity through the venturi. Several
variations of the standard venturi scrubber have been developed to allow the
venturi throat dimensions to be changed as gas flow rates change. Among
these scrubbers are the plumb-bob venturi, the flodded-disc venturi, the
moveable-blade venturi, the radial-flow venturi, and the variable-rod venturi.
4.1.4.3 Orifice Scrubber - In an orifice scrubber, sometimes referred to as
an entrainment or self-induced spray scrubber, the gas stream passes over a
pool of scrubbing liquid at high velocity just before entering an orifice.
The high velocity of the gas induced ("entrains") a spray of scrubbing liquid
droplets, which interact with the particulate in and immediately after the
orifice. Orifice scrubbers have moderate pressure drops (3 to 15 in. W.G.)
and low penetration of particulate 2 to 3 MmA in diameter and larger.
4.1.5 Mechanically Aided Scrubbers
The mechanically aided scrubbers utilize a mechanical rotor or fan to
shear the scrubbing liquid into dispersed droplets. These scrubbers use a
specially designed stator and rotor arrangement which produces very finely
4-5
-------
GAS INLET
LIQUOR
INLET
GAS OUTLET
LIQUOR OUTLET
FIGURE 4-2. Venturi Scrubber.
divided liquid droplets that are effective in the capture of fine particu-
late. The low penetration of fine particulate, however, is achieved at a high
energy cost. Both wet fan and disintegrator type mechanically aided scrubbers
are subject to particulate buildup or erosion at the rotor blades, so they
are often preceded by precleaning devices for removing coarse particulate.
4.2 INSPECTION PROCEDURES
4.2.1 Opacity and Gas Flow Rate
The inspection of all particulate wet scrubbers starts with an evalua-
tion of plume opacity, weather conditions permitting. The residual plume
4-6
-------
(after steam plume dissipation) has a direct relationship to the mass concen-
tration in the effluent gas. Procedures for evaluating wet scrubber opacity
are discussed in Chapter 10.
Gas flow rate through the wet scrubber should be estimated by use of a
pltot tube or by analyses of process operation. The flow rate is an important
variable since 1t often determines the relative velocities between the parti-
cles and the water (droplets or sheets) and therefore determines the effective-
ness of Inertial impaction.
4.2.2 Static Pressure Drop
Static pressure measurements should be made before and after the wet
scrubber.3 Often it 1s necessary to clean out the existing static pressure
taps prior to making the measurement since these taps are prone to plugging.
At the same locations, the gas temperature should be measured. (Note that
water droplet Impaction on the temperature probe may not allow measurement of
a true dry bulb temperature.)
Performance of wet scrubbers can be evaluated by comparisons of the
present "power input" (usually proportional to pressure drop) to the baseline
level. This approach, called the Contact Power Method, is described in
references 3 and 4.
The Contact Power approach is based on the concept that penetration is
directly related to the energy input into the gas-liquid contact.5'9 For
gas-atomized scrubbers, the power consumption is approximated by the equation
PG = 0.158 AP Eq. 4-1
where
PQ * power consumed, hp/1000 acfm.
AP * gas phase pressure drop, 1n. W.G.
When the liquid stream adds a significant fraction of the total energy,
Equation 4-2 is also used. The total energy is the sum of the gas and liquid
phase power consumption (Equation 4-3).
aln the case of ventuM scrubbers, the downstream tap should be located after
the elbow or in the cyclonic separator in order to avoid boundary layer
separation phenomenon.
4-7
-------
PL » 0.583 PfL Eq*
where
Pf » fluid pressure, pslg.
L » Iiqu1d-to-gas ratio, gpm/1000 acfin.
PT « PG + PL E1«
The scrubber collection efficiency 1s then expressed as shown 1n Equation 4-4.
NT « 0P? Eq- 4~4
where
( Inlet grain loading 1
NT » number of transfer units, In (outlet grain loading j, dimension!ess.
PT * total power consumption, hp/1000 acfm.
0,/3 * constants, dlmensionless.
The constants are parameters dependent on the characteristics of the particu-
late matter. Using this approach 1t 1s assumed that there are no independent
effects due to throat velocity, I1qu1d-to-gas ratio, scrubber design and other
parameters.
In certain cases it 1s possible to achieve good correlations using this
approach. Figure 4-3 shows the relationship between outlet loadings and sta-
tic pressure drop for a set of scrubbers on coal-fired boilers. Hesketh^ has
developed an empirical equation relating to static pressure drop and penetra-
tion. As shown 1n Figure 4-4 there is a good relationship between the two
parameters.
Pt - 3.47 AP-1-43 Eq. 4-5
where
P^ * penetration, dimension!ess.
AP « gas phase pressure drop, 1 in. W.fi.
The contact power analysis Indicates whether sufficient energy is being
expended. It can lead to erroneous conclusions 1f there has been a major shift
1n the inlet particle size distribution. Also, physical problems which can
lead to excess emissions regardless of power input can also invalidate a con-
tact power analysis. Such problems include poor gas-liquid distribution (i.e.
venturi throat), particle regeneration, and particle nucleation. These can be
detected only by Increased opacities. The Contact Power Correlations also do
not appear to be valid when there is significant condensation of water vapor in
the scrubber or when the 11quid-to-gas ratio is below 5 gallons per 1000 ACF.
4-8
-------
0.07
0.06
0.05
0.04
<*_
o
•o
7: o.o3
HJ
o
3 o.oo;
o
•4-J
HI
2 3 4
Theoretical Power Consumption, HP/10^ ACFM
FIGURE 4-3. Correlation of a Coal-Fired Boiler Scrubber Outlet
Dust Loading with Theoretical Power Consumptiony
4-9
-------
0.500
0.200
0.100
0.050
0.020
0)
0-
0.010
0.005
T 1 I I M HI
• '
i i
r—i—i i i i IT
i
i
i
3 4 5 6 7 8 10 20 30
Static Pressure Drop, Inches W.G.
50 70
FIGURE 4-4. Comparison of Predicted Penetration as Calculated 1n
Equation 4-5 and Measured5
4-10
-------
4.2.3 External System Inspection
The components of the wet scrubber system should be inspected on a
regular basis. This usually does not require much time and often emerging
performance problems can be readily identified.
4.2.3.1 Demister - Demister problems are usually caused by plugging or
scaling from excessive material buildup or mechanical failures. One easily
Identifiable symptom is the carryover and eventual fallout of droplets from
the scrubber stack. This is usually caused by reentrainment of the scrubbing
liquor as it passes through openings in the partially blocked demister at
higher than design velocities. Another sign of demister failure is the
buildup of material around the lip of the stack. This carryover of material
can also buildup on the fan blades and cause severe vibrations which should
be readily apparent.
A properly operating demister washing system should prevent excessive
material buildup from occurring. The inspection should include an investiga-
tion into the type and frequency of demister washing and the quality of the
washing water. If the water has a high solids content, a cleaner water
source may be necessary.
The most accurate method of determining demister performance is the
measurement of the static pressure drop across the demister. The normal
pressure drop range is between 0.5 and 2.0 inches of water with most applica-
tions less than 1.0 inches. Any measurement outside of this range indicates
significantly decreased efficiency of the demister.
4.2.3.2 Throat (Venturi Scrubbers)- The inspection of the throat of a ven-
turi scrubber should include an evaluation of the ease of access to the
liquor distribution components. If the nozzles or weirs are not easily
accessible, this may mean that regular maintainence is very difficult and
that maldistribution may occur. This problem is particularly acute when the
nozzles are susceptible to abrasion and plugging.
At the point of water introduction into the throat, a thermocouple should
be used to measure the gas inlet temperature. A temperature greater than
300°F can be an indication of potential operating problems if the gas stream
4-11
-------
contains high organic or metallic vapors. Upon contact with the liquor in
the throat these vapors will condense to form submicrometer particles. Often
the particles form after passing the zone of optimum inertia! impaction,
hence, penetration of these particles is high.
The use of recirculated liquor with a high solids content may also lead
to problems when the entering gas stream 1s greater than 300°F. Some of the
atomized liquor droplets may evaporate to dryness releasing a "regenerated"
particle. Thus, a small degree of evaporation can significantly increase
mass emissions from the scrubber.
If the venturi has a variable throat, the relative position (open or
closed since baseline tests) should be noted. This position has a large
effect on throat pressure drop since this changes the cross sectional area
available for the liquor and gas to pass through. As the throat area decrea-
ses, the relative droplet particles velocities Increase, hence, penetration
is reduced.
4.2.2.3 Shell - The exterior of the scrubber shell is inspected for corrosion
and erosion. Corrosion is quite probable if the shell construction material
is carbon steel and the pH of the recirculated liquor is less than 6. The
problems caused by erosion usually occur 1n areas of high velocity and direct
contact of the gas-liquor stream. The most common areas of damage are the
elbow of the venturi, opposite the tangential inlet to the cyclonic separator,
and the inlet to the venturi throat.
4.2.3.4 Precooler - The presence of a precooler should be noted during the
inspection. Certain types of problems associated with the temperature of the
gas stream as discussed under the throat Inspection procedures above can be
remedied through the use of a precooler. The quality of the water used in
the precooler should be determined. Since most of this water evaporates, a
high solids content can significantly increase the mass loading of the gas
stream that enters the throat.
4.2.3.5 Sump, Recirculation Line, Make-up Line and Purge Line - An attempt
should be made to make an estimate of the liquor recirculation, make-up and
purge rates if at all possible. The most suitable location for the recir-
culation and make-up rate estimates is at the point of discharge into the
4-12
-------
red rculation tank. The purge rate estimate can be made at the settling
pond or lagoon. If there 1s some apparent or suspected problem with the
scrubber, a sample of the recirculation liquor can be obtained from the top
of the recirculation tank. This sample can be analyzed to determine if it
has any properties which might adversely affect the system. At this time
the temperature and pH of the recirculation liquor can also be measured.
In order to document the recirculation system, a fl ow diagram of the scrub-
ber's piping should be drawn.
The static pressure drop across the demister should be measured. Plug-
gage of this can lead to reduced gas flow through the wet scrubber or to
carryover of water droplets. The latter can result 1n fan Imbalance or
local fallout. Static pressure drop across demisters normally range from
0.5 to 3.0 inches W.6.
Internal inspection of wet scrubbers 1s normally not necessary or
advisable. It 1s usually possible to check for nozzle pluggage or poor liquor
spray patterns by viewing the nozzles from an external hatch (when the unit
has no effluent gas passing through and has been purged). Other problems
can be identified equally well simply from the viewing ports of a hatch3.
The entry into a wet scrubber should be done only by plant maintenance
personnel cognizant of potential damage which can be done to corrosion resis-
tant linings, trays and other components.
aHatches should be opened only by plant personnel, and all safety procedures
should be fully satisfied.
4-13
-------
4.3 REFERENCES
1. Theodore, L., and Buonlcore, A. J., Industrial A1r Pollution Control
Equipment for Particulates. CRC Press, Cleveland 19/b.
2. Calvert, S., J. Goldshmld, D. Leith, and D. Mehta, Wet Scrubber System
Study. Volume I; Scrubber Handbook. EPA-R2-72-118a, August 1972.
3. Engineering-Science, "Scrubber Emission Correlation," Final Report to
U.S. EPA, Contract No. 68-01-4146, Task Order 49, 1979.
4. Semrau, K. et al., "Energy Utilization by Wet Scrubbers," EPA Report
600/2-77-234, November 1977.
5. Semrau, K. T., C. L. Wltham, and W. W. KerHn, "Energy Utilization by
Wet Scrubbers," EPA-600/2-77-234, November 1977.
6. Semrau, K. T., and C. L. Wltham, "Wet Scrubber Liquid Utilization,"
EPA-650/2-74-108, October 1974.
7. Strauss, W., Industrial Gas Cleaning, 2nd Edition, Pergamon Press,
Inc., New York, N.Y., 1975.
8. Hesketh, H., "Fine Particle Collection Efficiency Related to Pressure
Drop, Scrubbant and Particle Properties, and Contact Mechanism," J.
A1r Pollution Control Association, Volume 24, No. 10, October 1974,
pp. 939-942.
9. Ranade, M. B., and Kashdan, E. R., "Design Guidelines for an Optimum
Scrubber System," Second Symposium on the Transfer and Utilization of
Partlculate Control Technology, U.S. Environmental Protection Agency
Publication EPA-600/9-80-039a, September 1980, pp. 538-560.
4-14
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5.0 MECHANICAL COLLECTORS
Mechanical collectors comprise a broad class of particulate control
devices that utilize the mechanisms of gravity settling, inertia!, and dry
impaction. Performance capability is limited to the relatively large particle
size ranges. Because of this limitation and increasing regulatory require-
ments, use of mechanical collectors has gradually declined and they are now
used primarily as precleaners; although in certain applications, mechanical
collectors are adequate. They are reasonably tolerant of high dust loadings
and are not susceptible to frequent malfunction if properly designed and
operated.
The principal diagnositc tool for evaluating mechanical collector per-
formance is the static pressure drop. Other performance indicators include
opacity and solids discharge rate.
5.1 COMPONENTS AND OPERATION
In a cyclone3, a vortex is created within the cylindical section by
either injecting the gas stream tangentially or by passing the gas stream
through a set of spin vanes. Due to inertia, the particles migrate across
the vortex gas streamlines and concentrate near the cyclone walls. Near the
bottom of the cyclone cylinder the gas stream makes an 180 degree turn and
the particles are discharged either downward or tangentially into hoppers
below. The treated gas passes upward and out of the cyclone.
5.1.1 Simple cyclones
The simple cyclone consists of an inlet, cylindrical section, conical
section, gas outlet tube, and dust outlet tube. A typical tangential inlet,
axial outlet simple cyclone is shown in Figure 5-1.
aOnly cyclones and multi-cyclones are addressed in this manual. For informa-
tion on the other various types of mechanical collectors, refer to the Parti-
culate Control Techniques Document, Second Edition1.
5-1
-------
GAS
IN"
GAS OUTLET TUBE
DUST OUTLET TUBE
OUSTOUT
FIGURE 5-1. Typical Simple Cyclone
Particle separation is a function of the gas flow throughout the cyclone
cylindrical diameter. At higher gas flow rates and smaller cylinder dia-
meters, the particle inertia is greater resulting in higher collection
efficiency. There is an upper limit, however, where the increased turbulence
caused by higher gas velocities can disrupt particle concentration.
Medium efficiency single cyclones are usually less than 12 feet in dia-
meter and operate at static pressure drops of 2 to 6 inches W.G. Overall
collection efficiency is a function of the inlet particle size distribution.
5-2
-------
5.1.2 Multiple cyclones
A multiple cyclone consists of numerous small-diameter cyclones operat-
ing in parallel. The high-efficiency advantage of small-diameter tubes is
obtained without sacrificing the ability to treat large effluent volumes.
The individual cyclones, with diameters ranging from 3 to 12 inches,
operate at pressure drops from 2.0 to 6.0 inches W.G. The inlet to the
collection tubes is axial, and a common Inlet and outlet manifold is used to
direct the gas flow to a number of parallel tubes. The number of tubes per
collector may range from 9 to 200 and is limited only by space available and
by the ability to provide equal distribution of the gas stream to each tube.
Properly designed units can be constructed and operated with a collection
efficiency of 90 percent for particles in the 5 to 10 ymA range.1 Factors
which may contribute to reduced performance include erosion, plugging, corro-
sion and hopper recirculation.
Hopper recirculation in reverse flow type system occurs when tubes at
the rear of the bank have a slightly lower static pressure drop. This can
occur whenever flow distribution is nonideal or when the outlet tubes are
shorter than those in the front (a common design). In these cases a portion
of the gas in the front tubes can pass out the bottom and then enter the
discharge of tubes in the back rows.
Hopper recirculation can lead to substantially reduced collection effi-
ciency. Some of the ways to minimize this problem include segregation of
the hopper and equalizing the lengths of all discharge tubes.
Ambient air inleakage into the hopper area can interfere with the dust
discharge in the tubes and lead to increased emissions. These leaks may
occur at hopper flanges, access hatches or through the solids discharge
valves. Severe leakage on multicyclones serving combustion systems can be
identified by measurement of the flue gas oxygen content before and after the
collection.
Plugging of the gas inlet vanes leads to partial or total failure of
individual tubes to establish an adequate vortex. Partial plugging allows
dust penetration through the affected tube. Complete plugging results in an
5-3
-------
increased flow of gas through the remaining tubes and an increase in overall
collector static pressure drop. Partial plugging of a significant number of
tubes can cause variation in pressure drop from tube to tube, cause gas short
circuiting through the dust hopper, and cause an increase in dust reentrai nment
at the tube dust outlet.
Plugging of outlet tubes or the sol Ids discharge is common. The latter
is generally due to poor hopper discharge practices which allow solids to
periodically accumulate to the bottom of the tubes. Further information on
mechanical collectors can be found in references 1-6.
5.2 INSPECTION PROCEDURES
Static pressure taps should be installed on the inlet and outlet ducts
so that the static pressure drop can be measured on each inspection using
portable gauges. Since these taps often plug, the tap should be cleared
before attempting any measurements. Shifts from a baseline static pressure
level may indicate internal problems and reduced part icul ate collection
efficiency. Comparison with baseline levels 1s done by correcting gas flow
rate and gas temperature data back to levels during the baseline period.
This is done using Equation 5-1.
«p) (d,nep) Eq. 5-1
I ^baseline)
where
Q » flowrate, ACFM
d » density factor, dimension less
The gas densities can be obtained by use of a psychrometric chart shown in
Figure 5-2. To get a density factor, the humidity must be roughly estimated.
For units serving combustion sources, flue gas oxygen content should be
measured on a routine basis at the tap holes. This value should be compared
with typical values for the specific unit to determine if there is deter-
ioration of the unit. An increase of more than 0.5% 02 across the collector
is a sign of excessive air inleakage.
The rate of solids discharge should be checked frequently. Bridging of
solids in the hopper, failure of the solids discharge valve, or severe internal
problems may all be identified by this simple technique. All of these demand
immediate attention.
5-4
-------
CL30
200
300
DAY BULB TEMPERATURE IN DEGSEES F
400
400
QOO
FIGURE 5-2. Psychrotnetric Chart for Humid Air
(Reprinted with permission of American Air
Filter, Louisville, Kentucky)
Internal inspections should be conducted by plant personnel, at a mini-
mum on an annual basis. These should be conducted by personnel qualified
in proper confined area entry procedures and during a major outage after the
unit has been purged out. The internal inspection should identify plugging,
erosion, and corrosion problems. In some cases it may be advisible to use
tracers or smoke to identify gasket and weld leaks.
5-5
-------
5.3 REFERENCES
1. Theodore, L. and Buonicore, A.J., Industrial Air Pollution Control
Equipment. CRC Press, Cleveland, Ohio, 1976, p. bb.
2. Licht, W.. Air Pollution Control Engineering, Marcel Dekker, Inc., 1980.
3. Baxter, W., In: Air Pollution, Vol II. 3rd Edition, A. Stern, editor,
Academic Press, New York 1977.
4. Strauss, W., Industrial Gas Cleaning. 2nd ed., Pergamon Press, 1975,
p. 213.
5. Crawford, M., Air Pollution Control Theory, McGraw-Hill, Inc., 1976,
p. 236.
6. Schneider, A.C., "Mechanical Collectors," In: Handbook for the Operation
and Maintenance of Air Pollution Control Equipment, Cross, F. L. and
Hesketh, H. E., editors, Technomic Publishing Co., Westport, Ct., 1975,
pp. 41-68.
5-6
-------
6.0 CARBON BED ADSORPTION SYSTEMS
Carbon adsorption is a technique for the removal of organic vapors from
a gas stream. The adsorption process is made possible through the use of
specially "activated" carbon adsorbent which is highly porous and possesses
fine capillaries. These attributes result in a very high surface-to-volume
ratio. Through capillary action and secondary bonding, the activated carbon
can adsorb onto its surface large quantities of volatile organics.
6.1 COMPONENTS AND OPERATION
In a typical carbon adsorption unit, as shown in Figure 6-1, the organic
vapor laden gas stream passes through a filter to remove particulate matter and
then through a cooler to reduce the temperature to less than 38°C. A blower
then forces the gas stream through one of the carbon beds. The organic vapors
are adsorbed by the carbon and the purified air flows to the atmosphere. In
order to have continuous operation, a second carbon bed is being regenerated.
Regeneration is necessitated when the carbon becomes saturated with organics.
Adsorption of a vapor by activated carbon occurs in two stages. Initial-
ly- adsorption occurs at an efficiency approaching 100 percent, but as the
retentive capacity of the carbon is reached, traces of the vapor begin to
appear in the exit air stream. This is called the breakthrough point of
carbon beyond which the efficiency of removal decreases rapidly.
Eventually, the vapor concentrations at the inlet and exit become equal
as the carbon becomes saturated having adsorbed the maximum amount of vapor
that it can adsorb at the specific temperature and pressure. Figure 6-2
graphically illustrates the deterioration of performance as the active sites
on the carbon surface are depleted.
In the regeneration process, the organics are desorbed from the carbon
by passing either steam or hot gases through the bed. The temperature of
6-1
-------
Steam
Vessel A
•tx-
Vessel B
•X-
•• •.»••».• .•••.•••. ••.-' •.«••••*
;•;.'.'.'>:' Carbon 'Bed;'••.•;::':•
-'.•'.'•'.''•• ••/.. '.•-.",'•*•'' ••".."•.""»'.' °
* » » • «^ * •* • • • • i , _• .* •_& * *
I
Solvent
Laden
Air
Cooling
Water
To Atmosphere
Condenser
Recovered
Solvent
FIGURE 6-1. Typical Carbon Bed Adsorber
6-2
-------
-
Note: This curve is an example.
Actual time will vary for
each application.
GOO
500
400
300
200
100
50
1 2 3 4 if7
25 30 35
On-Stream Time (Minutes)
40
45
FIGURE 6-2.
Discharge Concentration vs. Time for a Non-Cooled Carbon-Bed
Adsorption System
6-3
-------
This desorbing medium must be such that the carbon is heated to a temperature
higher than that at which the organic vapors were adsorbed. Saturated steam
at low pressures is the most common desorbing medium. The steam is usually
passed through the carbon bed in a direction opposite to the flow of gases
during adsorption.
The steam along with the desorbed solvents are passed to a condenser and
then are decanted to separate the water and the recovered solvent. The re-
generation process leaves the carbon hot and saturated with water. Sometimes
(and in newer systems), before the carbon bed is placed back on stream, cool-
ing of the carbon is performed. Atmospheric air blown through the bed is most
commonly used to remove the heat from the carbon.
Regeneration/adsorption cycles are controlled either manually or auto-
matically. With automatic control, cycles are either executed for a set
time or vary depending on the continuous measurement of effluent concentration
(called "breakthrough control"). Breakthrough control utilizes monitoring of
the effluent concentration to identify the point where a bed is just approach-
'ing breakthrough, at which time the vapor laden inlet gas stream is switched
to a regenerated bed.
6.2 INSPECTION PROCEDURES
Excessive emissions from carbon bed adsorption systems usually result
from the typical failure modes of the carbon beds and their ancillary equip-
ment. These failure modes are as follows:
o Steam valves leak;
o Air discharge valves leak;
o Insufficient steam flow during regeneration;
o Insufficient time for steamout;
o Poor steam distribution;
o Condensation system failure;
o Collapse of carbon bed;
o Loss of carbon activity;
o Bed blockage or channeling due to buildup of lint, dust, polymers,
or other materials;
o Uneven bed distribution; and
o Improper setting of system controls.
6-4
-------
Unfortunately, it is impossible to detect -many of these failure modes by phy-
sical inspection and many of the inspection procedures involved are unduly
hazardous for the inspector. This section presents several inspection tech-
niques that are presently available and which can be readily utilized by
maintenance and regulatory agency personnel in determining the effectiveness
of operating carbon adsorption systems.
Discharge gas monitoring can demonstrate that breakthrough does, or does
not occur.1 Although not an exact test, it 1s probable that a system which
goes through several cycles of full-load operation without reaching break-
through, is operating at adequate adsorption efficiencies. Determination of
the presence of absence of breakthrough requires that solvent concentrations
in the 0-500 ppm range be continuously measured. Several types of instruments
are presently available for measuring solvents at these low levels. Among
these are:
o Flame ionization systems;
o Ultra-violet ionization systems; and
o Diffusion sensors.
These systems each have some advantages and disadvantages. They require cali-
bration for the solvent being measured if exact measurements are required, but
can also be used without calibration to indicate relative concentration levels.
If the output of a suitable detector is connected to a recorder, the adsorber
discharge concentration can be monitored over several cycles to determine if
a breakthrough occurs. For a facility operating at normal production rates,
the absence of breakthrough may be taken as evidence that the adsorption sys-
tem is operating satisfactorily. For successful testing an inspector must be-
come familiar with the use of the instrumentation, safety considerations in its
use, and its application to carbon adsorption systems.
An overall system material balance, taken over a reasonable time period,
is one of the best techniques for determining overall system efficiency.1 To
utilize a material balance the plant must maintain accurate records of solvent-
containing materials entering the process, and of the recovered solvent. Re-
covered soJvent returned to the process is considered as part of the solvent
entering the system. The solvent concentration of all materials entering the
process must be known. A form for a material balance is presented in Figure
6-3.
6-5
-------
CARBON BED ADSORPTION SYSTEM MATERIAL BALANCE
Inventory Period: From .to
INPUT
(a) Solvent containing materials:
i of materials x (# solvent/1 material) * I solvent.
1.
2.
3.
4.
5.
6. Total solvent in raw materials (in #)
(-1+2+3+4+5)
(b) Purchased solvent
7.
8.
9.
10.
11. Total purchased solvent (in #)
(-7 + 8 + 9 + 10)
RECOVERED SOLVENT
12. Total solvent from recovery system
13. Solvent sold
14. Recycled solvent (-12-13)
% OVERALL EFFICIENCY
100 x (12)
(6) + (11) + (14)
Note: If the solvent-recovery system returns more than one solvent stream,
a separate sheet should be prepared for each solvent stream. Over-
all efficiency is the average of the efficiencies for each stream.
FIGURE 6-3. Overall Material Balance For Facilities Using
Solvent Recovery Systems
6-6
-------
Most of the information can be assembled from shipping data, and from com-
ponent data available from raw-material suppliers. The data needed to complete
the material balance is the quantity of recovered solvent. This data is only
available directly from the source through use of totalizing flow meters which
measure solvent from the recovery systems. Since not all installations have
these flow meters installed, the material balance procedure will not be appli-
cable to every carbon bed installation.
A third efficiency evaluation procedure can be used for systems employing
instruments (such as flowmeters) providing data which can be used to calculate
steam to recovered solvent ratios.^ If one assumes a constant solvent input
into the system and constant length adsorption cycles, then if the ratio of
solvent to steam decreases, it is indicative of a decrease in collection
efficiency. This technique is readily used on systems recovering immiscible
solvents and having flowmeters on both the solvent and water streams following
the decanter. While it will alert maintenance/inspection personnel to a
malfunction of some type in the carbon bed system it is, unfortunately, of
little aid in diagnosing the problem.
Several types of visual inspections can also be used to help in evaluat-
ing carbon adsorption system.3 The first visual check that can be made is to
see if the proper bed is on the adsorption or desorption cycle according to
the mode selection of the control panel.
If the system operates on timed cycles, then a check should be made to de-
termine if the bed actually changes at the predetermined time (the cycle dura-
tion). At this time, the agency inspector may also inquire as to the rationale
for the cycle duration. Sometimes operating conditions no longer coincide
with design specifications and cycle times have not been adjusted accordingly
to insure adequate system performance.
If the system utilizes breakthrough control, then the concentration sett-
ing of the organic analyzer being used to monitor the exhaust should be
checked to see that it is within reasonable limits. If possible, the zero
setting of the device (as described in the operating manual) should also be
checked.
6-7
-------
During regeneration, the steam pressure according to the gauge(s) should
be compared to the design value to aid in determining if beds are being fully
regenerated. Lastly, a quick visual inspection should be made for corrosion,
especially 1n the piping between the carbon beds and the condensor and the
condensor system itself.a
6.3 REFERENCES
1. Mlchaelis, Theodore B., "Techniques to Detect Failure in Carbon Adsorp-
tion Systems," report by Engineering-Science, EPA Contract No. 68-01-
4146, July 1980.
2. Communication between Mr. Ted Michaelis, Engineering-Science and Ms.
Robin Segal 1, Engineering-Science, 19 February, 1982.
3. Communication between Mr. Macon Shepard, Engineering-Science and Ms.
Robin Segall, Engineering-Science, 19 February, 1982.
dSome organics form acids when regenerated with steam.
6-8
-------
7.0 FLARES
Flares are used for the control of gaseous combustible emissions from
stationary sources. They are most often employed to dispose of large quan-
tities of gases during plant upsets. In these cases flows are usually inter-
mittent with flow rates of several million cubic feet per hour during a
major upset. Flares have also found use as a control device for continuous
gas flows of the order of a few hundred cubic feet an hour. This is a rel-
atively inexpensive method to control gaseous emissions, but unfortunately
has the potential disadvantage of creating other emissions from the flare
itself.
7.1 COMPONENTS AND OPERATION
There are three types of flares commonly in use today. These are the
elevated flare, the ground flare, and the forced draft flare. The choice of
flare type depends on the specific characteristics of the gas flow to be
disposed of and the primary aim in flaring the gas. Elevated flares are used
primarily in conjunction with vapor relief collection systems in large-scale
chemical manufacturing or petroleum refining operations; expedient vapor
disposal rather than pollution control is the design emphasis.
Ground flares, which include conventional flare burners discharging
horizontally and the "low-level" flares, are useful for the disposal and
control of routine discharges. The low level flares are generally less noisy,
and emit much less thermal radiation and glare. They are also more efficient
than elevated flares in the combustion of gaseous wastes and thus have lower
air emissions. Ground flares used alone are not suitable for large gas flows,
however, and so often, low level flares are used in conjunction with an
elevated'Tlare when the possibility of the sudden venting of substantial gas
quantities exists.
7-1
-------
Forced draft flares use a blower of. some type to supply the air and
turbulence necessary for the efficient and smokeless burning of vented gases.
Unlike other efficient flares, they do not require the use of steam, water, or
an auxiliary gas for smokeless flaring. Forced draft flares are advantageous
1n their low operating cost and reliability, but are relatively expensive to
Install and can only handle a relatively narrow range of waste gas flow rates.
7.1.1 Elevated Flares
The modem elevated flare system 1s made up of several components
Including the flare tip, some type of gas trap directly below the tip, a
pilot and Ignition system at the top of the flare tip, and the stack and its
support. When smokeless burning 1s required, a steam Injection system must
also be provided at the top of the flare. Water seals to prevent the spread
of fire and knockout drums are also usually required for safety reasons-
Figure 7-1 shows a schematic of a typical elevated flare system.
The flare tip where waste gas combustion occurs must have excellent
flame holding ability and mixing characteristics to enable 1t to operate over
a wide range of turndown ratios. This 1s ensured using multiple continuous
Pilots around the combustion tip and by providing a flame stabilization ring
on the tip (see Figure 7-2).
Smokeless burning for elevated flares 1s achieved using special flare
tips which inject water, natural gas or steam into the flame thereby increasing
air-gas mixing and ensuring complete combustion. Water injection has many
disadvantages and natural gas injection 1s cost effective only 1n cases where
the gas has no value, so steam is most commonly used to achieve smokeless
burning.
There are two basic steam Injection techniques used 1n elevated flares.
In one method steam is Injected from nozzles on an external ring around the
top of the tip (Figure 7-2). In the second method the steam is Injected by
a single nozzle located concentrically within the burner tip.
In recent years regulations have required flares to be smokeless for
large turndown ratios. To ensure satisfactory operation under varied flow
conditions, these two types of steam Injection have been combined into one
tip. The internal nozzle provides steam at low gas flow rates and the
7-2
-------
L,
Cy
(2]
Flare Burner and Location
of Fluid!c Seal
Gas Trap
Riser Sections
Entry, Disentrainment
or Water Seal
Ladders and Platforms
FIGURE 7-1. Integrated Flare Stack Components1
7-3
-------
Utility Field Flare Tip
Flame Retention Ring
•Pilot Assembly
Endothermic Field Flare Tip
Smokeless Field Flare Tip
End other mi c
Assist Gas
Supply
Steam Distribution Ring
FIGURE 7-2. Flare Tips from John Zink Company!
7-4
-------
external jets are available at high flow rates. Several other special purpose
tips are currently in use including ones that inject steam and air and ones
that inject gas to raise the heat value of the waste gas stream.
The rate of steam injection to the flare tip is controlled manually or
automatically. While automatic control is usually not mandatory, it is
preferred because it reduces steam usage, greatly reduces the amount of
Smoking and minimizes noise. Automatic systems use flow measurement devices
with' ratio control on steam. Since the flow rate measurement cannot include
the variables of degree of saturation and molecular weight, the ratio controls
are usually set for some average hydrocarbon composition. It is usually
necessary to have a fixed quantity of steam flowing at all times to cool the
distribution nozzles at the tip.
To prevent air migration into the flare stack as a result of wind effects
or density difference between air and flare gas, a continuous purge gas flow
through the flare system 1s maintained. The system can be purged with natural
gas, processed gas, inert gas, or nitrogen. To reduce the amount of purge gas
required and to keep air out of a flare system, gas trap devices are also used
and are normally located in the stack directly under the flare tip. One type
of gas trap commercially available is the molecular seal (Figure 7-3). This
type trap may not prevent air from getting in the stack as a result of gas
cooling in the flare headers. Instrumentation systems are available to auto-
matically increase the purge rate to prevent air from entering the stack dur-
ing rapid gas cooling. Another type of gas trap is the Fluidic Seal which
utilizes baffles to create a velocity gradient between the waste gas and the
ambient air to prevent air migration into the flare stack. This seal weighs
much less than a molecular seal and can be placed much closer to the flare tip,
The pilot burners ignite the outflowing gases and keep them lit. Usually
three or four pilot burners are used. A separate system must be provided
for pilot burner Ignition to prevent flare failure. The usual method is to
ignite a gas/air mixture 1n an Ignition chamber by a spark. The flame front
travels through an Igniter tube to the pilot burner at the top of the flare.
This system permits the igniter to be set up at a safe distance from the
flare, up to 100 feet, and still Ignite the pilots satisfactorily. The
whole device is mounted on an ignition panel and set up in an accessible
spot on the ground. The Ignition panel must be explosion proof, have an
7-5
-------
unlimited life, and be Insensitive to all weather conditions. On elevated
flares, the pilot flame 1s usually not visible and an alarm system to Indi-
cate pilot flame failure is desirable. This is usually done by a thermo-
couple in the pilot burner flame. In the event of flame failure, the tem-
perature drops and an alarm sounds.
Outlet to Flare Burner
Outlet to Flare Burner
Clean-Out
Inlet from Flare Riser
National Air Oil NDS Double Seal
(Patent applied for)
Inlet from.Flare Riser
John Zink Molecular Seal
(U.S. 3,055,417)
FIGURE 7-3. Air Reentry Seals1
7-6
-------
Water seals and flame arrestors are used to prevent a flame front
from entering the flare system. Knockout drums are located at or near
the base of elevated flares to separate liquids from the gases being
burned.
7.1.2 Ground Flares
A ground flare consists of a burner and auxiliaries, such as, a seal,
pilot burner and igniter. Two types are found; one type consists of con-
ventional burners discharging horizontally with no enclosures. These
flares must be installed in a large open area for safe operation and
fire protection. If the ignition system fails they are not as capable
in dispersing the gases as an elevated flare. For these reasons this
type of ground flare has found only limited applications.
Ground flares may also consist of multiple burners enclosed within
a refractory shell as in the recently developed "low level" flares (Fig-
ure 7-4). The essential purpose of a low level flare is complete conceal -
"lent of the flare flame as well as smokeless burning at a low noise level.
The flared gases are connected by a manifold to a series of burner heads
which discharge the gas into a refractory enclosure. Mixing of the gas
and air 1s accomplished by a series of multi-jet nozzles. Combustion is
obtained with little or no steam because of the turbulence and temperature
of the burning zone due to the natural draft and the enclosure. This type
of ground flare can be designed to handle most plant flare occurrences and
then the remaining large releases can be diverted to an elevated flare-
Figure 7-5 is a schematic showing how such a system works. This type of
integrated flare system is becoming quite common, especially in populated
areas.
7.1.3 Forced Draft Flares
The forced draft flare uses air provided by a blower to supply pri-
mary air and turbulence necessary to provide smokeless burning of relief
gases without the use of steam. Figure 7-6 shows two common designs of
forced draft flares. This type of flare combines smokeless burning with
low operating cost and reliability because only pilot gas and electricity
are required. The flame is also stiffer and, because of the forced draft,
1s less affected by the wind. A blower flare should have an automatic air
turndown device to prevent excess air from quenching the flame and creat-
ing smoke if the flare gas rate is reduced. Variable speed blowers or
7-7
-------
baffles coupled to flow sensing devices have been used on these flares to
extend their turn-down ratio. These flares are used mainly to provide
smokeless burning where steam 1s not available.
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2 Flare Gas Risers
3 Flare Gas Header(s)
4 Flare Gas Connection^ )
5 Combustion Chamber
1 1 6 Refractor/ Lining and
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FIGURE 7-4. Ground Rare (from National A1r01l Burner Company)1
7-8
-------
7.2 INSPECTION PROCEDURES
The Initial and by far the most informative procedure in a flare in-
spection is the visible emissions observation. The presence or absence
of visible smoke is a primary indication of the flare's combustion effi-
ciency. Almost all flares in use at the present time will be of smokeless
design and therefore should have essentially no visible emissions.
Pilot Gas
Line
Elevated Flare Burner
Flare Gas
Line
Diversion
Seals
Control System
FIGURE 7-5. Ground Flare and Elevated Flare Connected by a Double
Stage Water Seall
7-9
-------
If smoke 1s visible, this 1s usually an Indication of some sort of
malfunction. An exception occurs 1n cases where the flare 1s burning waste
gases from a major plant upset and the gas flowrate has exceeded the practical
limit of smokeless burning for that particular flare. The most critical
determinant of smoke production 1s the amount and distribution of oxygen 1n
the combustion zone. Therefore a smoking flare might be caused by:
1. Lack of sufficient steam Injection (to provide turbulence and
oxygenated compounds) at the combustion zone,
2. Lack of sufficient water Injection at the combustion zone, or
3. Lack of sufficient air from blowers 1n forced draft systems.
Combustion
Air Inlet
Flare Gas
Inlet
Combustion
Air Inlet
a. Biaxial Forced Draft Unit
b. Coaxial Forced Draft Unit
FIGURE 7-6. Two Designs for Forced Draft Flare Systems*
7-10
-------
Comparison of the values from steam or water pressure gauges (if available)
with manufacturer's design values may provide an indication of whether
Sufficient pressure is available for smokeless combustion.
Unfortunately, flares do not otherwise readily lend themselves to reg-
gulatory and routine maintenance Inspections. Some further cursory inspec-
tion procedures include being aware of malodorous compounds in the flare's
vicinity and examining the ducts and pipes carrying the various gases, air
and steam for obvious leaks and signs of deterioration.
A potential future Inspection procedure for flares 1s the remote sens-
Ing of the components 1n the gas stream exiting the flare. This method
may provide a means of determining the combustion efficiency of flares
and the actual quantities of pollutants emitted to the atmosphere. For
an example of the application of remote sensing on flare emissions, the
report by W. F. Herget et al entitled "Development of Flare Emission
Measurement Methodology" is recommended.
7.3 REFERENCES
1. Klett, M. G. and J. B. Galeski, "Flare Systems Study," report by Lock-
heed Missiles and Space Co., Inc. for U.S. EPA Research Triangle
Park, NC, Publication No. EPA-600/2-76-076, March 1976.
2. Communication between Mr. Glenn Draper, Engineering-Science and Ms.
Robin Segal!, Engineering-Science, 18 February 1982.
7-11
-------
8.0 AUXILIARY EQUIPMENT
There are three main types of equipment auxiliary to air pollution
control devices. They are the (1) ventilation system which includes the
hoods and ductwork leading to the air pollution control device, (2) the fans
or blowers associated with the control device, and (3) the continuous monitors,
if any, installed after the control device to monitor the effluent. This
chapter discusses the counter-flow inspection procedures for these types of
equipment.
8.1 VENTILATION SYSTEM
The ventilation system is simply the hood and ductwork leading to the
air pollution control device. Since there are no moving parts it is often
erroneously assumed that nothing can go wrong. Actually the ductwork is
prone to serious air inleakage due to erosion and corrosion. Also, under
certain circumstances solids can build up, thereby restricting gas flow.
Evaluation of the ventilation system is done by observing the physical
condition and by measuring static pressure and gas temperature profiles. For
combustion sources an oxygen profile is very useful. These profiles are
acquired by measuring the various parameters at three or more points along
the ductwork. The measuring points could be simple 1/4" O.D. static pressure
taps or 1" to 2" ports equipped with threaded caps. They do not have to be
equally spaced.
The measurement results are plotted on a graph as a function of the
equivalent linear distance from the control device. As shown in Figure 8-1,
the static pressure (on systems with the fan after the control device) should
become progressively less negative as one moves away from the control device
toward the process. The slope of the line will be basically linear if the
equivalent lengths of elbows and duct expansions are used (calculation of
8-1
-------
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Scrubber
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100 200 300 400 500
Equivalent Length, Feet
1
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Fan -
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600 700
FIGURE 8-1. Example Static Pressure Profile (System Having a
Mechanical Collector and Wet Scrubber)
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equivalent lengths is discussed in Reference 1). A sharp change in the static
pressure profile slope suggests either partial blockage of the duct or a
large air infiltration point due to a hole, weld failure, or an open clean
out trap door. Air infiltration should be apparent also on the gas temperature
profile. This should increase directly proportional to the distance away
from the collector (see Figure 8-2). A discontinuity in the line3 indicates
the general location of an air inleakage. The flue gas oxygen content should
not change substantially; however, most systems have some degree of air
infiltration which leads to a gradually increasing Q£ level as one moves away
from the process (Figure 8-2). A sharp increase in the flue gas oxygen
content is indicative of air inleakage.
One common cause of air inleakage is holes caused by erosion. Particulate
matter laden gas streams moving at high velocities (3500 to 5000 feet per
minute) can be quite abrasive. Abrasion normally occurs at elbows and anywhere
the gas stream shifts direction sharply.
Uninsulated ducts are susceptible to corrosion, especially if the gas
stream has a high concentration of acid vapors. Moisture on the relatively
cool inner surface of the ducts absorbs the acidic compounds and promotes
corrosion. As air infiltration increases, the overall gas stream is cooled
by the ambient air, thus accelerating corrosion.
Hoods should be inspected to see if they have been damaged by overhead
cranes or other moving equipment. It is also common to find that operating
personnel have moved the hood to gain better access to the process equipment
or have adjusted dampers controlling the gas flow. The inspector must
determine whether the present hood configuration provides adequate emission
capture. A velometer or small pi tot tube may be used in measuring the gas
velocities around small hoods, while for large hoods visual observation may be
the only method available to evaluate captive effectiveness. In some cases
it is possible to evaluate hoods using static pressure readings one to three
duct diameters downstream from the hood. This static pressure is related to
the gas flow rate as shown in Equation 8-1.
Negative pressure systems only.
8-3
-------
Sph - (1-0 + Fh)Vp Eq. 8-1
where
Sp - hood static pressure,
Fn » hood entry loss factor.
Vp * velocity pressure.
The hood entry loss factor is constant for a given hood configuration
(see reference 1 for typica-1 values). The velocity pressure calculated in
this manner can be used to estimate gas flow. Use of this approach enables
Inspection/maintenance personnel to "baseline" a hood. This method, however,
only indicates the overall gas flow rate; 1t does not conclusively show that
the contaminants are being effectively captured. The latter is achieved only
when the overall gas flow rate and hood location are proper.
8.2 FAN EVALUATION
Inspection of the fan requires only a modest investment of time and
provides very valuable diagnostic information which can be used later to
narrow the scope of the inspection. The procedure described in this section
is useful for evaluation of relatively small direct- and belt drive fans with
rated gas flow rates of less than 50,000 acfm. Larger, more complex systems
may be evaluated using information available in standard texts such as Fan
Engineering, (Buffalo Force, Co, 1980). The Counterflow Inspection Procedure
utilizes the data listed in Table 8-1.
TABLE 8-1. FAN INSPECTION
1. Physical condition of fan housing
a. Vibration
b. Corrosion
c. Vibration/expansion sleeve integrity
d. Damper position
e. Hatch access
2. Fan operating conditions
a. RPM
b. Gas temperature
c. Sheaves ratio
d. Slippage squeal
e. Fan motor current
8-4
-------
8-2.1 Physical Condition of Fan Housing
The first item to be checked is fan vibration, and this is done simply
by observing the fan. The purpose of this initial check is primarily to
indicate whether the inspection can continue. In certain very unusual
circumstances, the vibration may be so severe that fan disintegration is
imminent. Such an event is life threatening, and accordingly the inspection
should be halted immediately and plant management should be advised of the
fan conditions.
Most small fans have flexible sleeves on the inlet and outlet ducts.
These serve to reduce the transmission of normal fan vibration to the duct-
work and also provide for thermal expansion. Cracks and tears in these
sleeves are quite common. If these occur on the inlet side, cold ambient
air is drawn in reducing the quantity of gas pulled through the process hoods
and air pollution control systems. This may result in increased fugitive
emissions at the process and increased fan energy use. If the fan happens to
be located before the control device, then both the inlet and outlet sleeves
are important.
Corrosion on the exterior of the housing may be indicative of gas
temperatures below the acid vapor and/or water vapor dewpoints. If this
problem does exist, the ductwork leading to the fan from the control device
will also suffer from corrosion, perhaps to the extent of significant air
inleakage. The latter is easily identified by a lower than expected gas
temperature coupled with higher than normal flue gas oxygen contents (com-
bustion sources only). Most oxygen analyzers are relatively easy to use and
are reasonably accurate (+_ 1 percent 02).
On a routine basis, plant personnel should inspect the fan wheel for
erosion, corrosion, and material accumulation. It is often possible to con-
firm that this is being done by examining the hatch or the fan housing.
8.2.2 Fan Operating Conditions
The most important fan operating parameter is the rotational speed
measured in revolutions per minute (rpm). The gas flow rate through a given
system is directly proportional to the rpm. A rough estimate of the rpm for
belt-driven fans can be obtained simply by multiplying the fan motor rpm by
8-5
-------
the ratio of the fan and motor sheaves as indicated in Equation 8-2a.
Fan rpm » (motor rpm) motor sheave diameter Eq. 8-2
fan sheave diameter
Obviously, the measurement of sheaves is subject to some error since it must
be done by looking through a belt guard. (Caution: the belt guard should not
be removed to obtain a more accurate measurement). Belt slippage can also
lead to a rotational speed several hundred rpm lower than estimated. This
slippage is usually detectable by an audible squealing and in extreme cases,
poor belt tension.
A more accurate measurement of rpm can be done by use of either a manual
tachometer, a phototachometer, or a strobe type tachometer. Use of a manual
tachometer is very straightforward assuming that there is a convenient access
port to the fan shaft. Often the configuration of the belt guard precludes
use of the manual tachometer. In such cases a phototachometer may be of use.
This device senses and counts pulses of reflected light. The most accurate
readings are obtained when a piece of reflective tape (usual'y supplied by
the instrument manufacturer) is fixed on the fan shaft. It is possible to
read integer multiples of the rpm if there is more than one reflective site
within the field of view of the sensor. The rough estimate derived by the
sheave ratio is generally useful in confirming that the lowest reading is in
fact the actual rotational speed.
Fan rpm on simple fans cannot increase unless the source personnel either
replace the motor or the sheaves. Since an increase in rpm normally results
in a greater gas flowrate, the performance of certain types of collectors,
electrostatic precipitators and fabric filters may be adversely affected. If
the tip speed has exceeded permissible limits (specified by the manufacturers)
fan disintegration may result.
For most fans used with air pollution control systems the total horsepower
required (termed the "brake horsepower") increases as the gas flow rate in-
creases. This is illustrated in Figure 8-3 which is a typical set of curves
for a radial blade fan. As the operating point in Figure 8-3 shifts to the
right it is apparent that there is a non-linear increase in the brake horse-
power.
dThe rpm of direct-drive fans does not vary.
8-6
-------
7 I S 10
us riow RATE. SCFH x 10'
n
12
FIGURE 8-3. Fan Curves and System Characteristic Curve
If the brake horsepower could be accurately calculated based on simple
measurements of fan operating conditions, it would be possible to make a
reasonable estimate of the gas flow rate through the system. Unfortunately,
this is usually not possible'since the brake horsepower is dependent on the
power factor which is neither easy to measure nor constant. The relationship
between brake horsepower and motor operating parameters is presented in
Equation 8-3.
Fan'brake horsepower * current x voltage x power factor x 0.746 Eq. 8-3
(amps) (volts)
Due to the direct relationship between motor current and the brake
horsepower and the basic nature of the fan curves (see Figure 8-3), it is
possible to identify significant changes in gas flow rate using only the fan
motor current which is relatively easy to measure using an inductance ammeter.
Normally, an electrical cabinet must be opened to reach wire not covered by
conduit piping. If the motor is a three phase type, the current in all three
wires should be measured and the average current computed. (CAUTION:
INSPECTORS SHOULD NEVER OPEN ELECTRICAL CABINETS DUE TO POTENTIAL SHOCK
HAZARDS. THE PLANT ELECTRICIAN SHOULD MAKE ALL SUCH MEASUREMENTS.) The
motor horsepower is normally used in fan performance evaluation.
8-7
-------
Since the brake horsepower 1s also a function of gas temperature, the
measured motor current must be corrected back to standard conditions before
comparison with the baseline motor current. This conversion may be done
using Equation 8-4 with the data presented in Table 8-2.
Motor Current (@STP) - Motor Current (@Temp) x (Table 8-2 Value @Temp) Eq. 8-4
If the corrected motor current has shifted more than 20% from the baseline
value, there has probably been a significant change 1n the gas flow rate
through the air pollution control system. The actual prevailing gas flow
rate can be measured using EPA Reference Method 2 procedures.
TABLE 8-2. FAN DATA, TEMPERATURE CORRECTION*
Temp
°F
20
40
60
80
100
120
140
160
180
200
220
240
260
280
300
Factor
0.91
0.94
0.98
1.92
1.06
1.09
1.13
1.17
1.21
1.25
1.28
1.32
1.36
1.40
1.43
Temp
°F
320
340
360
380
400
420
440
460
480
500
520
540
560
580
600
Factor
1.47
1.51
1.55
1.59
1.62
1.66
1.70
1.74
1.77
1.81
1.85
1.89
1.92
1.96
2.00
dFrom Basic Energy/Environment Analysis^, NAPA
Information series 67, by C. Heath, August 1978.
8.3 REFERENCES
1. American Conference of Governmental Industrial Hygienists, Indus-
trial Ventilation. Sixteenth Edition, 1980.
2. McDermott, H. J., Handbook of Ventilation for Contaminant Control.
Ann Arbor Science, 1976.
8-8
-------
9.0 PROCESS EQUIPMENT
The purpose of the process inspection is to answer questions and to
confirm conclusions reached in earlier steps. However, if the source is
subject to special state/local regulations or to New Source Performance
Standards or to National Emissions Standards for Hazardous Air Pollutants,
compliance with recordkeeping and monitoring requirements should be checked
first, using a DSSE-published series of documents which includes checklists
and associated information on recordkeeping and monitoring requirements.
In the process inspection the inspector can seek answers to questions
which arose earlier. He can address problems which could be individually or
collectively responsible for nonoptimal performance. Questions he might ask
include but but are not limited to:
1. Has the production rate increased (higher mass loading c.nd/or
gas flow rate)?
2. Have the raw materials and/or fuels changed to the extent that
effluent characteristics are different?
3. Has the process equipment deteriorated to the extent that emissions
are affected?
4. Have changes in operating conditions resulted in more difficult
collection problems (e.g. particle size decreases)?
The process inspector should begin at the control centers where the process
monitors are located, to look for signs of changes in operating conditions and
to observe current operating/maintenance practices. At these centers, process
operating data are available; a process flowsheet is generally posted on the
control panel; plant operators are generally nearby; and the subdued noise
level is conducive to technical discussions.
While in the control room, the inspector should seek out the process
monitors and/or records most pertinent to the compliance questions. Example
"inspection points" for six source types can be found in Table 9-1; several
generalizations can be drawn from this table.
9-1
-------
1. In most cases, the inspector can confirm increased production
rate by using data available in the control room;
2. The inspector can confirm raw material changes by inspecting
records kept either in the control room or in the administrative
offices;
3. The inspector cannot easily confirm process operational changes;
4. For batch operations, it 1s necessary to observe the equipment since
little useful Information is available in the control room; and
5. For other processes, it is possible to Identify changes in operating
conditions, but the significance of the changes is hard to deter-
mine.
Follow-up questions remaining after the inspection of records and monitors in
the control room can be quite time consuming due to the cyclic processes and
to distances between inspection points at large plants. The follow-up can be
guided by the items listed in Table 6, but the inspector is encouraged to
develop more extensive lists for specific plants. The presence of fugitive
emissions should be noted.
9-2
-------
TABLE 9-1. EXAMPLE INSPECTION POINTS, COUNTERFLOW INSPECTION PROCEDURES
Type of
Industry/Source
Inspection la the
Office and/or Control Room
Inspection of
Specific Equipment
.1. Con f Ira the Hates of Production end/or Cenerstlon
Sulfuclc
•eld
Aaphalt
Utility or
Induttrlel
boiler
Ceaent
Refinery
Check scld production records, and
observe acid flow rat* Indicator.
N/A
Check megsvatt generation and steam
production ratee.
N/A
Observe number of betchee shipped
per hour of plant operation.
N/A
Check rev aaterlal feed rate records. N/A
Check throughput recorde on catalytic N/A
cracker.
2< Confirm Raw Material Changes
Asphalt N/A
Utility or Check dilly records of eoalyiee:
Industrial Z ««h, IS, Btu content, ash fusion
boiler tenp.
Sulfurlc Check records of feed content! high
acid levels contribute acid mist.
Perform lab teate to determine coal
gradation and surface moisture
percentege.
Tske semple for later analyses.
K/A
Refinery
Check production Inventory recorde.
-------
vo
TABLE 9-1. EXAMPLE INSPECTION POINTS. COUNTERFLOW INSPECTION PROCEDURES (cont'd.)
Typ« of Inepection la th«
Industry/Source Of(let and/or Control Room
Inspection of
Specific Equipment
3. Confirm Process Operation*! Changes
Sulfurlc
•eld
Secondary
bras* and
bronie
Utility or
Industrial
boiler
Check cacalyet bed leap and air flow
rate to catalyst bed If SOj Monitor
valuta are high. Check acid concen-
tration teap end flow to absorber*.
Check record! for percentage of line
in alloy and for pouring teap.
Check air preheater exit
temperatures.
H/A
Check for grease and oil on scrap tod
for operational practices such as
Maintenance Integrity of slag load.
Check hood caption velocity in
furnace aree. Determine If line 1*
added before furnace teap le maximum.
H/A
4. Confirm Process Equipment Deterioration
Sulfurie
acid
Secondary
braa* and
bronie
Utility or
Industrial
boiler
Refinery
Observe SOj concentration monitor*!
check for inactive or poisoned
catalyst if SO] is high.
N/A
Check excess air level by meana of
Oj readings.
N/A
Check pressurs drop across mist
eliminator. If low, check for
shortclrcuitlnii if high, check for
plugging.
Check hoode and ductwork'for
physical damage end caption velocity!
Check to ae* if stoker boiler
draft above fuel beds has >0.10"
negative pressure.
Observe flow rate.
-------
10.0 VISIBLE EMISSION OBSERVATION
Plume opacity 1s evaluated in order to: (1) confirm compliance with
applicable regulations, and (2) to diagnose performance of air pollution
control equipment. This chapter does not deal directly with compliance
determination, rather it emphasizes the diagnostic aspects of the visible
emission observation. For those requiring detailed information on legal
requirements pertaining to opacity observations, it can be found in refer-
ences 1 and 2.
Plume opacity is the degree to which ambient light is absorbed and
scattered while passing through the plume to the observer. The usefulness
of the plume opacity concept is due to the fact that the extent of light
attenuation due to absorption and scattering is often directly related
to the particulate mass concentration in the plume gas stream; an increase
in plume opacity normally indicates an increase in the effluent mass con-
centration. Opacity is an especially useful, indicator for wet scrubbers
and electrostatic precipitators since the particles which are collected
the least efficiently are in the particle size range which attenuate light
most effectively. As the performance of these control devices begins to
degrade, the plume opacity increases significantly. Thus, opacity can
be early symptom of developing particulate collection problems.
10.1 OBSERVATION PROCEDURES
Incorrect visible emission observation procedures can result in sub-
stantial errors. Accordingly, it is important to adhere to the procedures
incorporated into the U.S. EPA Reference Method 9 (and most other similar
regulations). The basic requirements are as follows:
1. Observations must be made by a qualified observer who
has had formal training in proper procedures.
2. Readings should be made in the densest portion of the
plume which is free of condensed water.
10-1
-------
3. Readings must be made with the son at the observer's back,
within a quadrant of 140°.
4. To the extent possible, the observer should be approxi-
mately 90° (geometrically normal) to the plume travel.
The opacity observations should be made every 15 seconds for a total of
at least six minutes. Longer time periods are often desirable in order to
ensure representative operating conditions for the control device. If emis-
sion spikes or "puffs" are observed on an internrittant basis, the observation
period should be long enough to characterize the frequency.
A complete description of the observation conditions should be made at
the time of the observation (not written from memory at a later time). This
should include the position of the observer, the type of background, weather
conditions, and plume characteristics. One convenient form for opacity
observations, developed by Eastern Technical Associates under contract to the
U.S. EPA, is included in Appendix C.
The position of the observer should be characterized in sufficient detail
to estimate the angle of observation. On sources with high stacks or with
rectangular vents (such as roof monitors), it is possible to get an apparent
opacity which is above the actual opacity due to the angle of observation.
This is possible since the light coming to the observer is passing through a
wider section of the plume as shown in Figure 10-1.
1200*
1200*
FIGURE 10-1. Extended viewing pathlength on an elevated source
(Path I is actual diameter, Path L1 is apparent diameter.)
10-2
-------
The difference between the apparent opacity and the actual opacity for a
30 foot diameter stack is shown in Figure 10-2 for the observation angles of
30°, 45°, and 60°. It is obvious that the angle of observation can have a
significant effect, especially if the opacity readings are made at various
locations. In such a case the change in opacity levels from the baseline
level may be due at least partially to a change in observer location. For
this reason, diagnostic opacity readings should always be corrected back to
an observation angle of 0.
10 20 30 40 50 60 70 80 90 100
Real Opacity, %
FIGURE 10-2. Effect of the Angle of Observation in the Observed Opacity
for a Stack 30 feet in Diameter
10-3
-------
The position of the source relative to other possible sources of parti-
culate and/or steam should be recorded on .the observation form. There should
be no question that the observed opacity is for the source of interest only.
Conditions which may have influenced the readings such as fugitive road dust
and intermittant steam releases along the line of sight should be noted on the
observation form. Obviously, these values should be ignored when analyzing
the data to determine if opacity levels have shifted from the baseline levels.
Plume characteristics must be carefully documented. Certain effluent
gas streams contain volatile compounds or reactive compounds. During the
rapid cooling which occurs as the effluent leaves the stack, condensation of
the materials can lead to substantial quantities of aerosol which did not
exist as particles in the control device. Plumes composed primarily of such
aerosols are termed "secondary plumes" or "detached plumes". The presence of
a secondary plume usually does not imply control device operating problems.
Secondary plumes often have very low opacity at the stack exit (between 0%
and 10%) with very high opacities 1 to 5 stack diameters downwind. For this
reason the plume appears to be "detached" from the stack. Secondary plumes
do not revaporize like steam plumes.
The presence of condensed water in the plume usually can be easily
recognized by the experienced observer. If such a "steam plume" exists, the
readings should be made either before the water condenses or after it evapor-
ates to leave a residual plume; the location chosen by the observer should be
noted on the form. Reading in the region after evaporation is often the only
option available; however, it has no diagnostic value since the observed path-
length is never the same as that used in the baseline opacity observations.
Occasionally, there js. some question as to whether the steam plume has
actually dissipated and the observed plume is the residual aerosol not col-
lected by the control device. This can be addressed by analyzing effluent
gas stream and ambient meteorological conditions using a psychrometric chart
as shown in Figure 5-2.! The initial point is based on the measured stack
temperature and the average gas moisture content as estimated from previous
stack tests. The final point is the ambient wet bulb and dry bulb tempera-
tures. -If- the line connecting the two points does not cross the saturation
curve, then a steam plume probably is not present. If the line crosses into
10-4
-------
the saturation region and then reenters the unsaturated region at a tempera-
ture of 5° to 10° above actual dry bulb temperature, then plume dissipation
probably occurs.
The presence or absence of steam formation within the plume can also be
evaluated by comparing the dissipation of steam vent effluent at the plant,
with the dissipation of the plume of interest. If the steam vent plume
dissipates rapidly it 1s unlikely that condensed water will persist long in
the contaminated plume.
The color of the effluent is another plume characteristic which should
be observed. For fossil fuel combustion sources, the color is an indirect
indication of operating conditions. The following list in Table 10-1 was
compiled by EPA's Control Programs Development Divisions:
TABLE 10-1. PLUME CHARACTERISTICS AND COMBUSTION PARAMETERS
Plume color Possible operationg parameters to investigate
White Excess combustion air; loss of burner flame in oil-fired
furnace.
Gray Inadequate air supply or distribution.
Black Lack of air; clogged or dirty burners or insufficient
atomizing pressure, improper oil preheat; improper size
of coal.
Reddish brown Excess furnace temperatures or excess air; burner con-
figuration.
Bluish white High sulfur content in fuel.
For other types of sources, the color may not be as variable or may not have
a distinct meaning with respect to the process or the control equipment.
Nevertheless, a change in the color indicates a change in the system.
10.2 BASELINE EVALUATION
For diagnosing the change in performance of air pollution control
equipment, the magnitude of the shift in opacity from historical (baseline)
levels is as important as the magnitude of the opacity itself. A significant
increase in opacity usually indicates an increase in the mass concentration
of the effluent. The sensitivity of opacity as a diagnostic tool depends on
10-5
-------
the characteristics of the opacity-mass concentration correlation. Case 1 in
Figure 10-3 represents the most sensitive relationship between opacity and
mass concentration in that a large increase in opacity indicates a small
increase in the mass concentration (and presumably the mass emission rates if
flow rates are similar). In Case 2, opacity has diagnostic value only up to
a certain value at which point it becomes totally insensitive to the mass
CASE 1
80
CASE 3
20
CASE 2
i 2 3 *
MASS EMISSIONS. ARBITRARY UNITS
FIGURE 10-3. Opacity-Mass Relationships
10-6
-------
emission rate. Fortunately, most of the opacity-mass concentration correla-
tions which have been Identified appear to be basically linear as represented
by Case 3 1n Figure 10-3.
Figure 10-4 illustrates a opacity-mass concentration correlation devel-
oped at a coal-fired power station during a five-year testing program. The
relationship 1s typical of most correlations 1n that it is approximately
linear. It is unusual 1n that there 1s an abundance of test data with which
to prepare the correlation. Figures 10-5 and 10-6 present other correlations.
It 1s apparent that each of these correlations have a different slope and
different degrees of variability. For these reasons, the correlations must
presently be developed on a site-specific basis. Procedures for calculating
the 95% confidence Interval for the correlations are presented 1n Appendix F.
Usually 1t 1s not necessary to Include the confidence Interval when the
readings are used strictly for diagnostic purposes.
0.30 ,
J~ 0.25 -
T: 0.20-
0.15-
~ 0.10-
o.os
Test
1
2
3
4
S
Symbol
O
A
Q
O
V
Date
0*t*
Taken
2/73
11/73
6/75
6/75
8/78
MW
?
r
140
80
125
. 50
- 40
. 30
. 20
• 10
0
0.1 0.2 0.3 * 0.4 0.5 0.6 0.7 0.8
H - M«ss Concentration (g/N«J)
FIGURE 10-4. Example Opacity-Mass Relationship
(from reference 2)
10-7
-------
0.2
•0.1
75 I
70 5
rtj
-------
10.3 LIMITS TO THE USE OF OPACITY
Due to the particle size dependence of light scattering, opacity is
not universally applicable in evaluating mass concentration. Particles above
approximately 2 microns in diameter do not scatter light appreciably, there-
fore, substantial mass emissions of these relatively large particles may
occur without high opacity levels. In such cases, the material often settles
rapidly leaving deposits in.the vicinity of the discharge point. Inspection/
maintenance personnel must be aware of such sources and must utilize other
means to routinely evaluate control device performance.
10.4 REFERENCES
1. Missen, R. and A. Stein, "Guidelines for Evaluation of Visible Emissions,"
report by Pacific Environmental Sciences for the U.S. EPA, Report No. EPA-
340/1-75-007, April 1975.
2. "Quality Assurance Guideline for Visible Emission Training Programs,"
report by PEDCo. Environmental, Inc. for the U.S. EPA, EPA Contract
No. 68-02-3431, Work Assignment III, August 1981.
10-9
-------
11.0 SAFETY INFORMATION
Inspection/maintenance personnel should not be working at an industrial
facility unless they have the proper safety equipment, are trained in the use
of this safety equipment, and are trained to recognize potential safety haz-
ards. All plant safety requirements and all agency safety procedures (in
case of the regulatory agency Inspector) must be satisfied3. This chapter em-
phasizes the Importance of these safety procedures and provides supplemental
information concerning many of the most common procedures.
There are a wide variety of potential hazards which may be encountered
while inspecting and maintaining air pollution control equipment. A partial
list of these hazards is provided below.
1. Acute exposure to toxic gases such as S02, 03, N02> ^S and CO
due to entry into confined areas and due to fugitive leaks of
flue gas around open measurement ports, corroded door gaskets,
and corroded expansion joints and flanges.
2. Exposure to fume and dusts containing asbestos, lead, beryllium
and arsenic.
3. Burns due to contact with hot objects such as uninsulated flue gas
ducts and portable sampling/ measurement equipment.
4. Heat stress due to exposure to hot process equipment, hot flue
gas ducts and stacks.
5. Static electrical shock obtained while conducting measurements
downstream of electrostatic precipitators or in fiberglass ducts.
6. Falls through roofs or through horizontal surfaces weakened by
the accumulation of excess solids or the corrosion of interior
supports in air pollution control equipment.
aThe information and recommendations contained in this chapter have been
compiled from sources believed to be reliable and accurate. No warranty,
guarantee or representation is made by Engineering-Science as to the absolute
correctness or sufficiency of any representation contained in this and
other documents. It should not be assumed that all acceptable safety measures
are contained in this and other publications or that other or additional
measures' may not be required under particular or exceptional conditions or
circumstances. The information provided in this section is not intended to
super-cede, replace, or amend safety procedures adopted by regulatory agencies
and private concerns.
11-1
-------
7. Falls on wet walking surfaces 1n the vicinity of control
equipment or on the access ladders to control equipment.
8. Physical injuries due to entrapment in rotating mechanical
equipment such as fan sheaves and screw conveyors.
9. Head injuries from falling objects, overhead beams, and pro-
truding equipment.
10. Hearing impairment due to exposure to noise from rappers,
compressors, and process equipment.
11. Explosions of fans operating at excessive tip speeds or
operating severally out-of-balance.
12. Physical injuries due to the improper opening of access hatches.
13. Asphyxiation due to improper entry into confined areas.
14. Asphyxiation due to free flowing solids discharged from hopper
access hatches.
15. Eye injuries due to flying objects or splashing chemicals.
16. Foot injuries due to falling objects.
17. Explosions due to static electricity discharge within ducts being
sampled or tested.
18. Exposure to toxic gases, toxic particulate, or steam rising from
processes below or present in the general vicinity of elevated
walkways and platforms.
19. Burns due to contact with hot, free flowing solids.
20. Burns due to contact with high pressure steam leaks.
Despite the long list of potential hazards, inspection/maintenance work
on air pollution control equipment need not be dangerous. Each individual
simply must develop respect for these problems and carefully adhere to the
safety procedures adopted by his or her employer.
11.1 GENERAL PROCEDURES
Each individual performing inspection/maintenance work on air pollution
control equipment should adhere to the following two basic rules:
1. Every situation should be carefully evaluated before work is begun.
2. Work should be halted if the individual experiences headache, eye
or nose Irritation, nausea, dizziness, drowsiness, vomiting, loss
11-2
-------
of coordination, chest pains or shortness of breath. Conditions
should be reevaluated before continuing the work.
The first requirement can only be satisfied by conducting the inspection
or maintenance work in a methodical manner and at a controlled pace. Undue
haste can easily result in careless accidents. It is also important to take
a rest break whenever fatigue reaches the point that judgement is affected.
The second rule is necessary because many of the occupational hazards
encountered by inspection/maintenance personnel do not have any easily
recognized characteristics such as a distinctive odor. For example, some
chemicals such as ^S, which are easily recognized at low concentrations
cannot be detected at high concentrations since at high concentrations they
overwhelm and disable the sensory organs. Acute exposure to some materials
can occur without any immediate discomfort, then later (within 24 hours)
exposure will lead to severe respiratory Impairment. For these reasons it
is important that all personnel be familiar with the initial symptoms of
acute exposure to possible hazards so that they are able to leave an area
of exposure until environmental conditions can be more fully evaluated.
Each regulatory agency and industrial firm should have certain general
safety procedures to minimize the risk involved in equipment maintenance and
inspection. These should, at a minimum, consist of the following which are
covered in the next sections: Safety training, a medical monitoring program,
and written safety procedures.
11.1.1 Safety Training
All inspection/maintenance personnel should receive regularly scheduled
safety instruction in safety procedures, use of personal protective equipment,
and recognition of potential physical and inhalation hazards.*»2 It 1s also
desirable that each person receive training 1n First Aid and Cardio-Pulmonary
Resuscitation.2 Attendance at the safety training program should be mandatory
and should be recorded in each individual's employment file. New employees
assigned inspection/maintenance duties should receive this training prior to
beginning field work.
If the duties include responding to hazardous chemical spills or fires
or the Investigation of chemical waste dump sites, considerable additional
training may be necessary. Information concerning safety procedures for such
work may be found 1n reference 1.
11-3
-------
11.1.2 Medical Monitoring Program
Annual physical examinations should be conducted as a precondition to
further work. These examinations should provide screening for evidence of
exposure to toxic substances. They need not be a comprehensive health
evaluation since this remains the responsibility of each Individual, but
should, at a minimum, include the following tests:
1. Chest X-ray
2. Electro-cardiogram
3. Blood tests
4. Eye examination
5. Liver and kidney function tests
6. Pulmonary function tests
More detailed information is available in reference 1.
11.1.3 Written Safety Procedures
A written procedures manual should be prepared by each regulatory agency
and private organization involved in the inspection/maintenance of air pollu-
tion control equipment. This should at a minimum address use of personnel pro-
tective equipment, recognition of hazardous conditions, recognition of symp-
toms of exposure, procedures to be followed in the event of potential hazards,
and the reporting of Illnesses or accidents.
The manuals should be dated and revised whenever necessary. Each emplo-
yee should be Issued a numbered copy of this manual and should be responsible
for adding modifications to the manual.
11.2 COMMON INSPECTION/MAINTENANCE HAZARDS
Safe working procedures begin with a full understanding and respect for
potential hazards. Those problems most frequently encountered while working
on air pollution control equipment are summarized in this section. Additional
information is available in a number of excellent publications, including the
three listed below:
1. Occupational Diseases, A Guide to Their Recognition, Revised Edition.
U.S. Department of Health, Education and Welfare, June 1977.
2. The Industrial Environment - Its Evaluation and Control, U.S.
Department of Health, Education and Welfare, 1973.
3. Sax, N.I. Dangerous Properties of Industrial Materials, Van Nostrand
Reinhold Company, New York, N.Y.
11-4
-------
11.2.1 ^nhalatlon of Toxic Agents and Asphyxiants
There are a wide variety of toxic agents and asphyxiants which may be ac-
cidently inhaled during the inspection of an industrial facility. The value
of a medical surveillance program and proper safety procedures is demonstrat-
ed in the following paragraphs which summarize the potential consequences of
acute exposure to some of the most common air contaminants.
Soluble gases such as sulfur dioxide, ammonia, and chlorine have very dis-
tinctive odors and can often be detected by taste at very low concentrations.
At higher levels eye, nose, and throat Irritation occurs. Because of these
"warning properties", these types of air contaminants can usually be recog-
nized by Inspection/maintenance personnel who can leave the immediate area
or put on respirators. If the acute exposure continues, these compounds can
cause severe cardio-pulmonary problems Including but not limited to bronchitis
and pneumonia.
Most organic compounds and nitrogen dioxide are not very soluble and these
often penetrate deep into the lower lung. The initial symptoms of exposure
are nonspecific and may not be recognized by inspection/maintenance personnel.
These symptoms include: dizziness, drowsiness, headache, 1ightheadedness, and
nausea. The poor "warning properties" of these types of compounds makes them
extremely dangerous. Acute exposure may lead to pulmonary edema several hours
after the exposure.
The chemical and physical asphyxiants are another group of air contami-
nants which have very poor "warning properties". Chemical asphyxiants include
such gases as carbon monoxide and hydrogen sulfide. Carbon dioxide is the most
common physical asphyxiant. Inspection/maintenance personnel may be unable
to escape from confined and partially confined areas with high concentrations
of these compounds.
The inhalation of particulate matter rarely causes immediate physical
discomfort or impairment. For this reason, it is possible for undesirable
quantities of toxic materials such as lead, arsenic and asbestos to reach
the lung. These can be slowly absorbed Into the blood system thereby
allowing attack on organs such as the liver and kidney. In other cases, the
materials can lead to severe respiratory problems. Many of the problems
resulting from the Inhalation of particulate matter develop over an extended
11-5
-------
period of time and this fact underscores the need for a regular occupational
health screening physical.
Table 11-1 is a brief summary of the initial symptoms (if any) of exposure
to the common air contaminants. Since inspection/maintenance personnel are
usually more at risk from short term, acute exposures than from chronic expo-
sures, the acute symptoms are emphasized. Table 11-1 does not 11st all materi-
als of significant risk, does mrt 11st all the possible symptoms, and does jiot
provide a complete set of recommendations for personal protection equipment.
It 1s Intended simply to emphasize the Importance of good safety procedures.
The Occupational Safety and Health Standards regulations9 have very spe-
cific and detailed requirements regarding the use of respirators for protec-
tion from exposure to air contaminants. These are reproduced as Appendix D.
Each individual using respirators should ensure that the requirements are
satisfied. Basically this means that each individual should know how to
select the proper respirator, should be trained in the use of respirators,
should be fitted properly, should understand respirator maintenance require-
ments, and should be physically able to perform the work while wearing a
respirator. Information concerning the use of respirators is available in
reference 4, pages 519 to 526 and reference 7, pages 1025 to 1055.
11.2.2 Accidental Falls
Extreme caution is warranted whenever it is necessary to walk across
a roof or walkway which has a heavy accumulation of solids. Occassionally
these surfaces have not been designed to support this load plus the addi-
tional weight of one or two persons. When crossing such areas it is prudent
to remain close to the well trodden path.
A similar problem may be encountered on the roofs of air pollution
control equipment. In this case, corrosion of the, interior supports can
reduce the load bearing capacity of a roof, thus all should be crossed with
caution.
Around wet scrubbers and any other equipment using pumps there is often
a layer of. water 1n the adjacent walkways. In some cases, this layer of
water may be partially hidden by a cover of dust or fibrous material. If
inspection/maintenance personnel are not careful the slick area will be
discovered in a most painful manner.
11-6
-------
TABLE 11-1.
Compound
Route of
Entry
Symptoms of Exposure to Common Air Contaminants
(Source of data: References 3, 5 and 6)
Personal
Protection
Recommended
corns
Comments
Ammonia
Arsenic
Asbestos
Benzene
Beryllium
Inhalation
Inhalation
and
Ingestlon of
dust and
fume
Inhalation
of
airborne
fibers
Inhalation
of gas
Inhalation
of dust or
fume
Full face mask with
ammonia canister,
self-contained
rebreather or
supplied air
respirator
Self-contained
rebreather or
supplied air
respirator
Dust mask
Self-contained
rebreather or
supplied air
respirator
Self-contained
rebreather or
supplied air
respirator
Exposure may cause severe eye
and throat Irritation, nausea,
perspiration, vomiting and
chest pain.
Cough, chest pain, headache,
general weakness, followed by
gastrointestinal symptoms.
No symptoms,
Eye Irritation, headache,
dizziness, nauseai drowsiness,
convulsions.
Intense, brief exposure may
result In nonproductive
cough, low grade fever, chest
pains, and shortness of
breath.
Bronchitis or pneumonia
may result from an Intense
exposure.
Acute arsenical poisoning
due to Inhalation is rare.
Prolonged exposure may
cause cancer.
Acute exposure may lead to
unconsciousness and death.
Benzene 1s a confirmed
carcinogen.
Acute exposure to Beryllium
can result in chemical
pneumonitls with pulmonary
edema several hours after
exposure.
-------
TABLE 11-1.
Symptoms of Exposure to Common Air Contaminants (Cont'd.)
(Source of data: References 3, 5 and 6)
Compound
Cadmium
Carbon
Dioxide
Carbon
Monoxide
Ethylene
Oxide
Ethers
and Epoxy
Compounds
Hydrogen
Chloride
Route of
Entry
Inhalation
of dust and
fume
Inhalation
of gas
Inhalation
of gas
Inhalation
of gas
Inhalation
of gas
Inhalation
of mist or
vapor
Personal
Protection
Recommended
Dust mask
Self-contained
rebreather or
supplied air
respirator
Self-contained
rebreather or
supplied air
respirator
Full face
respirator and
protective
clothing
Self-contained
rebreather or
supplied air
respirator
Full face mask
Symptoms
Acute exposure may occur without
any Immediate symptoms. In
some cases there may be dryness
In the throat, headache, cough,
shortness of breath and vomiting.
Symptoms are those of asphyxia,
Including: headache, dizziness,
shortness of breath, weakness,
drowsiness, and ringing In ears.
Initial symptoms Include:
headache, dizziness, nausea,
drowsiness, pale skin color,
and vomiting.
Nausea, vomiting, eye and
nose Irritation, drowsiness.
Eye Irritation with tear
production, coughing, nausea,
drowsiness.
Eye and throat Irritation.
Comments
Brief exposures to very
high concentrations may
result In pulmonary
edema.
Rapid recovery occurs upon
return to fresh air.
Acute exposure may lead to
unconsciousness and pul-
monary edema.
Concentrations of 1,000 to
2,000 ppm are dangerous
even for a brief time.
-------
Compound
TABLE 11-1. Symptoms of Exposure to Common Air Contaminants (Cont'd.)
(Source of data: References 3. 5 and 6)
Route of
Entry
Personal
Protection
Recommended
Symptoms
Comments
Hydrogen Sulflde
Lead, Inorganic
Mercury, Inorganic
Nickel
Inhalation
of gas
Inhalation
of dust,
fume, or
vapor;
Ingestlon
Inhalation
of dust or
vapor
Inhalation
of dusts
Self-contained
rebreather or
supplied air
respirator
Self-contained
rebreather or
supplied air
respirator;
full body work
clothing
Self-contained
rebreather or
supplied air
respirator
Full face
respirator
Hydrogen sulflde has a
distinctive rotten eggs odor
at low concentrations, however,
at high levels there may be
no odor at all due to
olfactory paralysis.
Initial symptoms of acute
exposure Include: headache,
dizziness, eye Irritation,
loss of coordination,
weakness, and numbness.
No Immediate physical symptoms.
No Immediate physical symptoms.
No Immediate physical symptoms.
Death may result rapidly
from acute exposure.
Chemical pneumonia may
develop several hours
after exposure.
Work cloths should be
washed separately from
street cloths. Disposable
shoe covers may be advis-
able. Lead Is a cumula-
tive poison.
Work clothes exposed
should not be washed or
stored with street clothes
Elemental mercury readily
volatilizes at room
temperature.
Nickel 1s a suspected
carcinogen.
-------
TABLE 11-1.
Compound
Route of
Entry
Symptoms of Exposure to Common Air Contaminants (Cont'd.)
(Source of data: References 3, 5 and 6)
Personal
Protection
Recommended
Symptoms
Comments
Nickel CarbonyT
Nitrogen Oxides
(NO. N02)
Ozone
Sulfur Dioxide
Sulfurlc Acid
Inhalation
of gas
Inhalation
of gas
Inhalation
of gas
Inhalation
of gas
Inhalation
of mist
Full face
respirator
Self-contained
rebreather or
supplied air
respirator
Self-contained
rebreather or
supplied air
respirator
Self-contained
rebreather or
supplied air
respirator
Full
mask
face gas
Severe exposure can cause
headache, dizziness, nausea,
vomiting, fever, and difficulty
breathing.
Initial symptoms Include:
cough, chills, fever, headache,
nausea, vomiting.
Eye Irritation, dryness of nose
and throat, choking, cough, and
fatigue.
Sulfur dioxide has a strong.
suffocating odor at levels
greater than 0.5 ppm. The
taste threshold Is 0.3 to
1.0 ppm. Eye Irritation begins
at approximately 20 ppm.
Eye Irritation, tickling of
the nose and throat, coughing,
and sneezing. Concentrations
of 0.1 to 10 ppm may be un-
pleasant and concentrations of
10 to 20 ppm may be unbearable.
Nickel carbonyl Is a
confirmed carcinogen and
may release CO upon
decomposing.
i
Acute pulmonary edema may
follow a five to twelve
hour period with no
apparent symptoms. During
exposure only mild bron-
chial Irritation may be
experienced. Concentra-
tions of 100-150 ppm are
dangerous for periods of
30 to 60 minutes.
Pulmonary edema may occur
several hours after severe
exposure.
Survivors of acute
exposure may later develop
chemical bronchopneumonla
Concentrations of 400 to
500 ppm are considered
Immediately dangerous to
life.
-------
TABLE 11-1,
Compound
Route of
Entry
Symptoms of Exposure to Common Air Contaminants (Cont'd.)
(Source of data: References 3, 5 and 6)
Personal
Protection
Recommended
Symptoms
Comments
Toluene
Vinyl Chloride
Inhalation
of vapors
Inhalation
of vapors
Chlorine
Inhalation
of vapors
Full face mask
Self-contained
rebreather or
supplied air
respirator
Full face mask
Eye Irritation, headache,
dizziness, fatigue, drowsiness,
loss of coordination.
Vinyl chloride has a pleasant,
ethereal odor; exposure may
cause llghtheadedness, nausea,
and symptoms similar to mild
alcohol Intoxication.
Pungent odor at greater than
3.0 ppm. Throat Irritation
occurs at approximately 15 ppm.
Acute exposure may result In
cough, and chest pain, and eye
throat Irritation.
Acute exposure may lead
to collapse and coma.
Vinyl chloride Is a
confirmed carcinogen.
Pulmonary edema may occur
several hours after severe
exposure.
-------
An inevitable chore of inspecting air pollution control equipment is
climbing up and down ladders. During wet weather it is probable that the
last person to use a ladder deposited a layer of mud on the foot rungs.
Climbing the ladder may be dangerous unless the foot rails are used for the
hands (rather than the more common practice of grabbing the side rungs).
11.2.3 Noise
Whenever the noise level 1s high enough such that normal conversation
cannot be heard at a distance of 2 feet, hearing protection 1s necessary.
Speech Interference studies have indicated that this noise level is approxi-
mately equal to 82 to 88 dBA.7»8 For comparison purposes, the OSHA limit
for contluous exposure over an 8 hour period 1s 90 dBA.9
During Inspection/maintenance work, noise levels greater than 90 dBA may
be encountered around electrostatic predpitator rappers, compressors and
blow tubes for pulse jet fabric filters, Induced draft fans, and process
equipment. Even though the Inspection/maintenance personnel will usually not
be 1n the high noise location for the full 8 hour period, the use of hearing
protection is: (1) consistent with plant safety policies, (2) ensures
conformance with OSHA requirements, and (3) may improve communication. The
latter point may surprise some who instinctively believe that communication is
hindered by ear muffs or plugs. Actually there is some evidence to demonstrate
improved hearing with the use of ear protection when noise levels exceed the
90 dBA range. It is believed that the hearing protection prevents distortion
of the ear canal at the high noise levels while 1t keeps the speech-to-noise
levels at a constant level.8
Failure to use hearing protection can lead to gradual hearing loss es-
pecially 1n the frequency range of 1000 to 4000 Hz. Unfortunately, there are
no Immediate symptoms of noise Induced hearing loss. The pain threshold for
most individuals is 130 dBA, well above the 90 dBA level which can adversely
affect hearing,8
There are several basic kinds of hearing protection including: fixed
size ear plugs, malleable ear plugs, and earmuffsc When used properly, any of
these can reduce levels of noise 30 to 50 dB in the frequency range of 1000
to 4000 Hz.10*11 Obtaining a proper fit with a tight accoustical seal is
11-12
-------
very important. Some suggestions for obtaining the maximum degree of protec-
tion are listed below.
(1) If fixed size plugs are used, the fit should be checked on a regular
basis since the ear canal may increase in size with regular use of
any ear plug and since the ear plug may shrink slightly.
(2) Malleable plugs should be inserted before the inspector begins any
work which will get his hands dirty. For this reason, the plugs
should probably be inserted immediately after the pre-inspection
meeting (in the case of a regulatory agency inspector) and remain
in until the Inspection is over. This will prevent dirt or foreign
objects from causing irritation or infection of the ear canal.
(3) To obtain the best acoustical seal, the entrance to the ear canal
should be opened and straightened by pulling the ear backwards
with one hand while inserting the plug with the other. (For more
information, refer to the illustration shown in Reference 7,
page 333).
If adequate noise protection cannot be obtained by the use of a single
type of protector, then an inspector may wish to use an ear muff in combination
with a plug. This provides an additional attenuation of 3 to 5 dB over that
available with either one alone.10
11.2.4 Head Protection
Inspection/maintenance-personnel should wear hardhats whenever they are
on plant grounds (except of course when inside office spaces and similar
sheltered areas). The hardhats should satisfy the requirements of ANSI
Standards for Protective Helmets, Z89.1-1969. These should protect the
individual from falling objects (impact force less than 850 Ib-ft) and from
collisions with low crossbeams or small equipment suspended from the ceiling.
At least once a month, the hard hat should be checked for possible cracks
or a defective suspension. The latter is particularily important since it is
the suspension which provides the impact protection. Instructions for regular
washing of hardhats is provided in Reference 12.
11.2.5 Eye Protection
Inspection/maintenance personnel routinely pass through process equipment
areas where eye protection is mandatory. Glasses with side shields or flexible
goggles should be carried and put on when entering these areas. The eye pro-
11-13
-------
tection must conform to the requirements of ANSI Standards Z87.1-1968. Prac-
tice for Occupational and Educational Eye and Face Protection. Contact lenses
should not be worn.
11.2.6 Footwear
Many Industrial facilities do not require safety shoes as long as entry
to certain areas 1s not necessary. Nevertheless, safety shoes should be worn
at all times while performing Inspections/maintenance. Shoes with metal toe
boxes are generally adequate. The footwear should meet the specifications
of ANSI Standard Z41.1-1967.
11.2.7 Burns
Most of the gas streams of concern to air pollution control equipment
Inspection/maintenance personnel are at relatively high temperatures. For
example, the gas streams from cupolas and stoker fired boilers are often 400°F
to 600°F. The ducts transporting this effluent gas stream are often uninsu-
lated and contact with a duct surface can result 1n a burn.
Handling pi tot tubes and other sampling equipment recently withdrawn
from a hot duct is another common cause of burns. Insulated gloves are
available for this purpose.
11.2.8 Heat Stress
Heat stress is a potential problem for regulatory agency inspectors
since they do not have the opportunity to become acclimated to hot environ-
ments. Measurements of effluent conditions often brings inspectors into
close proximity of hot ducts and/or stacks, both of which radiate heat. If
preventive measures are not taken, either heat cramps or heat exhaustion may
result. The symptoms of these problems are severe cramps, extreme fatigue,
weakness, nausea, clammy or moist skin, high pulse rate, and a high body
core temperature.13 To reduce the risk of heat stress the inspection/main-
tenance personnel should take the precautions outlined below:
(1) Take frequent breaks 1n a cooler area.
(2) Drink fluids recommended by a physician or Industrial
hygiene professional for such conditions.
(3) If possible, schedule strenuous work and hot work in
the cooler parts of the day.
11-14
-------
11.2.9 Cold Weather Conditions
Routine inspection of air pollution control equipment should not be done
when the wind chill factor is below -20°F. The wind chill factor is a combined
Index of the ambient temperature and the wind velocity as shown in Table 11-2.
Below -20°F there is an Increased risk for localized cold injuries. There is
also a reasonable chance that measurements made under the stress of excessively
cold conditions win not be accurate due either to the impaired judgement of
the Inspector or due to the malfunction of portable instruments. Additional-
ly, during such periods, plant maintenance personnel often must cope with
process operational problems caused by the cold conditions. Thus, regulatory
agency inspectors should not perform any Inspections in very cold weather
unless warranted by a public health emergency or a severe problem demanding
immediate attention.
11.2.10 Electrical Shock
High static electrical charges can build up 1n certain ducts and control
systems. When Inspection/maintenance personnel attempt to insert a pi tot
tube, thermocouple, or other probe into the duct they may receive a consider-
able shock. In some cases, the static discharge could initiate a serious
explosion. Before inserting any portable test equipment or cleanout rod
Into a duct and gas stream, the test equipment probe and rod should be
grounded.* This consists of: (1) a proper electrical bond between the probe/
rod and the sidewall of the duct (or control device) and (2)-a proper ground
connected to the sidewall.
The existence of a proper ground for the sidewall must be confirmed with
the appropriate plant personnel. If 1t 1s impossible to prepare a proper
bonding wire £r 1t is impossible to confirm adequacy of the sidewall ground,
the measurement should not be conducted.
Also before a measurement is conducted, 1t is important to confirm that
the proper grounding equipment has been selected and that there are no defects
which would interfere with the static electricity dissipation. Each bonding
wire and ground connection should be visually and manually checked before
the measurement is made.
*For additionalfnformation on grounding see National Fire Protection Associa-
tion Publication No. 77 (1983) and American Petroleom Institute Recommended
Practice 2003, Fourth Edition (1982).
11-15
-------
TABLE 11-2. Wind Chill Factors
Wind in
ffl.p.h.
Calm
5
10
15
20
25
30
35
4o
>*5
50
32
Local Temoerature In Oeqress Fahrenheit
23
14
5
-4
-13
-22 •
"-31
Eouivalent Temoerature (Wind Plus Local Temoerature)
32
29
18
n
7
3"
1
-1
-3
-3
-4
23
20
7
-1
-6
-10
-13
-15
•17
-18
-18
Little— >
Danger
for Those
Properly
Clothed
14
10
-4
-13
-19
-24
-27
-29
-31
-32
-33
5
1
-15
-25
-32
-37
-41
-43
-45
-46
-47
-4
.a
-26
-37
-44
-50
-54
-57
-59
-61
-62
Considerable ^
Danger
-13
-18
-37
-49
-57
-64
-68
-71
-74
-75
-76
-22
-28
-48
-61
-70
-77
-82
-85
-87
-89
-91
-31
-37
-59
-73
-83
-90
-97
-99
-102
-104
-105
-40
-40
-47
i
-70 |
-88
-98
-104
-109
-113
-116
-118
-120
Extreme ^*
Danger
11-16
-------
The portable instruments should not be taken into plants and facilities
where there is a chance of exposure to explosive gases, vapors, fibers, or
dusts. Such industrial operations include, but are not limited to: grain
elevators, grain milling operations, coal dust handling facilities, and many
types of chemical processes. The battery operated thermocouples, pH meters,
and typical flashlights are not explosion proof.
A regulatory agency Inspector should never attempt to open an electri-
cal cabinet to make ammeter readings. Such measurements should always be
made by qualified plant personnel.
Inspection/maintenance work should not be conducted during threatening
weather conditions. Lightening sometimes travels a considerable distance
ahead of an approaching storm and normally strikes the high areas of a plant
where the air pollution control equipment is usually located.
11.2.11 Ionizing Radiation
The new hopper level detection instrumentation used frequently on large
scale fabric filter and electrostatic precipitator systems employs a source of
gamma radiation to detect the accumulation of solids. If the source unit has
been damaged due to impact from moving equipment or some other cause, exces-
sive radiation levels in the immediate vicinity of the source could result.
Normal safety procedures in this case include posting warning signs and
roping off the damaged area until the source can be sealed. The regulatory
agency inspector should thus be cautioned never to approach a damaged nuclear
type hopper level detector.
When entering the hopper, plant maintenance personnel should carefully
complete the lock-out procedure for the nuclear type level detector. The
shield must cover the source unit in order to provide protection.
11.3 CONFINED AREA ENTRY
A confined area may be defined as an enclosure in which dangerous air
contamination cannot be prevented or removed by natural ventilation through
openings. Access to the enclosure 1s usually restricted, so that it is
difficult for a worker to escape or to be rescued. Examples of such confined
areas Include fabric filter compartments, electrostatic precipitator pent-
houses and electrode sections, wet scrubber internals, mechanical collector
11-17
-------
internals, and hoppers on all types of air pollution control equipment.
Maintenance personnel must enter these areas on regular basis; regulatory
agency inspectors should not enter confined areas. It is important to
note:
Plant maintenance personnel should be trained in proper confined
area entry procedures, should be given the necessary respirators
and personal protective equipment, and should be required to per-
form all work in strict adherence to plant safety procedures and
OSHA requirements.
Potential dangers of confined area entry can be grouped into three cate-
gories: oxygen deficiency, explosion, and exposure to toxic air contaminants.
Oxygen deficiency is a very common and insidious hazard since many of the gas
streams treated 1n air pollution control equipment have oxygen concentrations
of only 4% to 12%. Oxygen levels of less than 19.5% produce detectable physi-
ological changes, while levels less than 16.0% result 1n rapid disability and
death. Unfortunately, the initial sensory symptoms of low oxygen levels are
simply a slight difficulty in breathing and ringing in the ears. Maintenance
personnel may ignore these symptoms and then rapidly become incapacitated.
Prior to entering any confined space, the environment inside should first be
tested using a portable oxygen analyzer. The probe should be long enough
so that the gas actually _[n_ the confined area is tested rather than the air
leaking in around the partially opened hatch.
Maintenance personnel must be cognizant of the explosion potential inside
air pollution control equipment. Many combustion sources generate moderately
high concentrations of carbon monoxide, especially during upset periods. A
combustible gas analyzer should be used to detect the presence of CO and
organic vapors. The particulate matter collected in many control devices is
also potentially explosive.
Some of the most common toxic air contaminants 1n the confined areas of
air pollution control equipment are ^S, 303, N02 and particulate. Maintenance
personnel should select and use the proper respirator based on the initial
sampling of the interior environment of each confined area.*
*The selection and use of respirators are subjects too involved and too impor-
tant to be" covered briefly; for these reasons, they are beyond the scope of
this manual. For detailed information please read the appropriate references
listed earlier.
11-18
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11.3.1 general Entry Procedures
The National Institute of Occupational Safety and Health (NIOSH) has
presented specific guidelines for working inside confined areas. Excerpts
from this document are provided in Appendix E. Maintenance personnel should
study the excerpts in Appendix E and then read the entire NIOSH document.
A written permit should be obtained prior to entry into confined areas.
This should confirm that the'establlshed lockout and isolation procedures have
•
been followed and the personnel have the proper safety equipment. This permit
should be posted in a conspicuous location. During the lockout the air pollu-
tion control system and all accessory systems should be locked and tagged.
The accessory systems include: fans, rapper systems, conveyors, compressors,
solid discharge valves, hopper and Insulator heaters, hopper level indicators,
and pumps. If more than one person 1s involved 1n the entry, each person
should have his own lock and key for each Hern which must be locked out.
The access hatch to the confined area should be opened with extreme
caution. If a unit which operates at a positive pressure has not been
deenergized yet, the hatch will have as much as 300 pounds of force on the
interior surface of the hatch (6 inches static pressure, hatch 2'x4'). Once
the last bolt or latch has been removed, the hatch will accelerate outward.
Units which operate at negative pressures have the opposite problem in that
the hatch is held closed with several hundred pounds of force. Personnel who
wrap their hands around the hatch 1n a futile attempt to "break the seal" can
suffer severe injuries 1f the hatch slams shut again. Opening of hopper
access doors must be done with particular care since hot, free flowing solids
may be piled up behind the door. Once the hatch is opened these solids can
suffocate, severely burn, and/or otherwise injure personnel below the access
hatch. Additionally, many of the solids collected 1n air pollution control
systems are combustible. When the hopper access hatch is removed the Inrush
of ambient air (and oxygen) can cause fires inside the control device.
Once safe access is achieved, the environment should be carefully observ-
ed and tested. The oxygen concentration and the levels of potentially toxic
gases should be determined by portable meters. The dust levels should be ob-
served. Entry should not be made until the proper personal protective equip-
11-19
-------
ment has been put on and checked out. There should always be an observer
1n the vicinity of the access hatch who 1s trained and equipped to rescue
the worker(s).
There are several specific confined area entry problems for each type of
air pollution control system. These are summarized in the following sec-
tions.
11.3.1.1 Electrostatic Precipitators - A predpltator which has been deener-
gized for a period up to several days may still have a residual electrostatic
charge of 10 to 20 kilovolts on the electrodes. The electrodes could deliver
a fatal shock unless this charge is first dissipated to ground using a "hot
stick". A "hot stick" normally consists of a long wooden stick with.a metal
hook on one end and a flexible metal conductor connected to a ground. This
should be used each time entry is made into a penthouse and electrode zone.
Regular maintenance (primarily involving cleaning and testing) is necessary
for the hot sticks. If the sound of "buzzing" characteristic of a hive of
bees is ever heard upon opening of a hatch, the unit is still energized.
Work should be immediately halted!
While working inside an electrostatic precipitator, a securly connected
ground should be kept in plain view at all time. If the power supply is acci-
dentally energized this ground could provide some degree of protection.
11.3.1.2 Fabric Filters - Large fabric filter systems are often built with a
number of compartments, one or-irore of which may be Isolated for maintenance.
Entry to the off-line compartments for maintenance should be done with the
same care used for entry Into any other confined area. The dampers which
isolate one compartment from another often leak which can result in high
concentrations of toxic gases such as ^S and CO in the off-line compartment.
While performing maintenance work Inside a fabric filter, care should
be taken that the self-contained rebreather or supplied air respirator do
not damage the bags adjacent to the walkways; there is often very little
clearance inside fabric filters. Before entering fabric filters, the size
of the hatch should be considered with respect to the difficulty in removing
a worker in an emergency situation. Maintenance personnel inside fabric
filters (also electrostatic preclpitators and mechanical collectors) are
11-20
-------
Particularly vulnerable to heat stress due to the additional work inherent
in the use of respirator and the moderately high temperatures usually found
inside this equipment.
The purpose of the preceding discussions is to emphasize the importance of
proper entry procedures for air pollution control equipment. Some basic
considerations have been introduced. Individuals involved in this work should
carefully read OSHA requirements9 and other references on the subject.
11.4 REFERENCES
1. Safety Manual for Hazardous Waste Site Investigation, U.S. Environmental
Protection Agency. Draft Manual dated September 1979. Available from
the Office of Occupational Health and Safety, Waterside Mall, 401 M Street
S.W., Washington, D.C.
2. Stack Sampling Safety Manual, Prepared by Norman V. Steere & Associates
for the U.S. Environmental Protection Agency, Contract No. 68-02-2892,
September 1978.
3. Occupational Diseases, A Guide to their Recognition, Revised Edition, U.S.
Department of Health, Education and Welfare, June 1977.
4. The Industrial Environment - Its Evaluation and Control, U.S. Department
of Health, Education and Welfare, 1973.
5. Dangerous Properties of Industrial Materials, Sax, N.I. Van Nostrand
Reinhold Company, New York, N.Y.
6. Accident Prevention Manual for Industrial Operations, National Safety
Council, 6th Edition, 1971.
7. Patty's Industrial Hygiene and Toxicology, Third Revised Edition, Volume 1.
G. Clayton and F. Clayton, Editors.Wiley-Interscience Publication Page 340,
8. Reference 6, Page 1152.
9. Occupational Safety and Health Standards, U.S. Department of Labor,
Federal Register, Vol. 37, Number 202, page 22157, October 18, 1972.
10. Reference 6, Page 1155.
11. Reference 7, Pages 337-338.
12. Reference 6, Page 1149.
;
13. Reference, Pages 937-948.
14. A Primer on Confined Area Entry, Rexnord Safety Products, Malvern, Pa.
11-21
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12.0 ADMINISTRATIVE AND LEGAL ASPECTS OF PLANT INSPECTIONS
12.1 INTRODUCTION
The majority of this inspection manual deals with Counter-flow Inspection
Techniques for the actual performance evaluation of air pollution control
equipment. An equally important consideration in conducting air pollution
field inspections is the administrative aspects of the inspection including
preparation, entry to the plant, post-inspection procedures, and report writ-
ing. The legal aspects and consequences of the enforcement inspection must
be considered prior to visiting any facility.
This chapter presents the administrative and legal aspects of conducting
a field inspection. Due to the complex nature of environmental law and the
differences in statutes from state to state it can not be an exhaustive study
of the subject, nor can it be used as the final word on the specific laws or
regulations. Rather, the aim of this chapter is to bring to the prospective
inspector's attention the various administrative elements of the entire in-
spection scheme which are essential to a successful and complete regulatory
inspection. It covers procedures for preparation for an inspection, plant
entry practices, points to be aware of during the inspection and some post-
inspection and report preparation considerations. In addition, special
sections of this chapter are devoted to methods of handling confidential
business information and photographic documentation.
12.2 PREINSPECTION PROCEDURES
12.2.1 File Review .
Prior to inspecting a facility an agency inspector should review the
agency files concerning that facility to thoroughly familiarize himself
with all pertinent information on the facility's particular process(es),
types of emissions, and operating history. The following items should be
checked. Copies of items 1 and 2 from the list should be obtained for the
inspector's "working" file.
12-1
-------
1. Pending compliance schedules and .variances,
2. Construction and/or operating permits pertaining
to source processes,
3. Past conditions of noncompliance,
4. Malfunctions reports, and
5. History of-abnormal operations.
The inspector should also obtain a copy of appropriate plant layout drawings
to assist in locating emission points, drawing flow diagrams, and in preparing
the inspection report. If available in the files, the inspector should note
what personal safety equipment is required. The files should always be re-
viewed before entry to the plant so that important plant characteristics will
be more easily remembered.
The inspector should prepare a concise "working" file containing basic
plant information, process descriptions, flowsheets, and acceptable operating
conditions (Appendices A and B). It should contain the following to facili-
tate inspections and/or preparations:
1. A chronology of control actions, inspections, and
complaints concerning each major source in the plant;
2. A flowsheet identifying sources, control devices,
monitors, and other information of interest;
3. The most recent permits for each major source;
4. Previous inspection checklists; and
5. Baseline performance data.
Once compiled, such a file is easy to update and allows an inspector to do an
effective file review without struggling through the typically voluminous
central files.
The inspector should know what regulations are applicable to the facility
and if he has any questions should consult the agency administration or legal
staff prior to conducting the inspection. It is important to know what data is
useful in confirming compliance and what evidence is necessary to document pos-
sible violations of each of the applicable regulations.
Based on reviews of agency and any previous "working" files, the inspec-
tor should schedule an inspection time when plant processes will probably be
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operating at representative conditions. The scheduling of a time to visit
plants having batch operations or other irregular operating schedules (e.g.,
seasonal) is especially important.
12.2.2 Inspection Announcement
Agency supervisory personnel should be consulted concerning agency policy
on the advance announcement of Inspections. If 1t is desirable to announce
the Inspection 1n advance, leads of 1 day to 1 week are generally adequate to
ensure that the necessary plant personnel will be available. The person
contacted should be one having the authority to release data and samples and
to arrange for access to specific processes.
12.2.3 Inspection Equipment
Necessary tools and safety gear should be organized and be ready to
carry in a portable case from emission point to emission point.
Carry at all Times
Hardhat
Safety glasses or goggles
Gloves
Coveralls
Safety shoes (steel toed)
Ear protectors
Dust masks
Tool belt
Tape measure
Flash! ight
Differential pressure gauges
Gauge magnets
Thermocouples
Multimeter and grounding cables
pH paper or pH meter
Duct tape
Pocket guide of Industrial hazards
Other equipment should be gathered to be left in a central location such as
the inspector's car until needed.
Carry When Needed
Respirator with appropriate cartridge(s)
Ropes and harness
Stopwatch
Pryba r
Velometer
P1tot tubes
Bucket
Sample bottles (Continued)
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Combustion gas analyzer
Oxygen meter
Tachometer
Self-contained breathing equipment
Particularly important is the safety equipment—including the hard hat, the
safety glasses, and the ear protectors. Remember, it is the inspector's
responsibility to know what safety equipment will be needed and to have it
before entering the plant. "Access to certain industrial facilities can be
rightfully restricted or refused by plant representatives if designated safety
equipment is not worn.
Some plant may require that equipment brought on to plant property be
signed in. An equipment inventory form may facilitate check-in of the inspec-
tion equipment.
12.2.4 Plant Surroundings
Observations of areas surrounding the plant before entering may reveal a
variety of signs of operational practices and pollutant emissions which can
aid in the preentry evaluation, including:
1. Obvious vegetation damage near the plant,
2. Odors downwind of the plant,
3. Deposits on cars parked closeby,
4. Other signs of "dusting" downwind of the plant,
5. Fugitive emissions near plant boundaries,
6. Conditions around the product and/or waste storage piles,
7. Conditions near lagoons and sludge ponds, and
8. Proximity of source to potential receptors.
Some of the signs may indicate that fugitive emission sources should be added
to the inspection agenda. If odors are a problem, the weather conditions in-
cluding wind direction should be noted for inclusion in the inspection report;
once inside the plant, olfactory fatigue may (under certain circumstances)
reduce the inspector's ability to detect odors.
12.2.5 Visible Emission Observations
In addition to observing the plant surroundings prior to entry, the in-
spector can also perform visible emission observations at this time. It is
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possible that not all emission points will, be visible from a location outside
the plant property lines, but those that are may be conveniently read before
entry. Chapter 10 details the procedures for these observations.
It 1s appropriate for the inspector to inform plant management of excess
visible emissions subsequent to their observation; and at the same time he
should find out what caused them. Notification of the plant officials of
excess emissions gives them the opportunity to promptly evaluate the problem.
There may be statutes which require notification and the Inspector should
discuss this with his agency's legal staff.
12.2.6 Plant Entry
Arrival at the facility must be during normal working hours. As soon as
the inspector arrives on the premises he should locate a responsible plant
official usually the plant owner or manager. In the case of an announced
inspection this person would most probably be the official to whom notification
was made. It is important that the inspector note the name and title of this
official. The inspector should be prepared to present the official with cre-
dentials and to summarize the reasons for the plant visit. Credentials pro-
vide the plant official with assurance that the inspector is a lawful repre-
sentative of the agency. Proper credentials should include the inspector's
photograph, signature, his physical description, (age, height, weight, color
of hair and eyes), and the authority for the inspection.
Unless express permission has been obtained from the inspector's employ-
er, visitor release forms and waivers which purport to release the company
from tort liability should not be signed. An Inspector may waive his right
to sue for damages by signing these release forms. The precise effect of
signing an advance release of liability for negligence depends upon the law
of the state in which the tort occurs. The State Attorney General can make
a current determination of the effect of these waivers for each individual
state. It 1s suggested that the inspector consult with the legal staff of
his agency and have them obtain a determination. If the plant official
denies entry for refusal to sign a waiver, the Inspector should take down the
official's*name and title, leave the plant, and contact his supervisor for
further Instructions.
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Inspectors have, in the past, occasionally been asked to sign nondisclo-
sure statements or agreements. These agreements vary slightly in content
from one to another, but generally require that confidential information,
disclosed to an inspector during the course of an inspection, be handled there-
after in a specified manner. An inspector should not sign such agreements
unless the agency's legal counsel has expressely approved the agreement.
To avoid subsequent legal entanglements, an inspector must gain entry to
a plant's private premises and perform inspection activities in a manner con-
sistent with the company's right of privacy guaranteed by the Fourth Amendment
of the U.S. Constitution. In a recent Supreme Court decision [Marshall v.
Barlow's. Inc. 436 U.S. 307 (1978)3, the court held that an OSHA inspector
was not entitled to enter a work site without either (1) the owner's consent,
or (2) a warrant. This decision has affected the policy for conducting inspec-
tions under EPA's programs and the state programs and has made it important
for all federal and state inspectors to conduct inspections in conformance
with their agency's policies.
In order to have the background information necessary to obtain a warrant
and following the guidance of the Barlow decision, there are several procedural
steps that should be followed when an authorized plant official refuses entry
to an inspector:
1. Tactfully discuss the reason for denial with the plant official.
This is to insure that it has not been based on a misunderstanding
of some sort. If resolution is beyond the authority of the inspector
he might suggest that the official seek advice from the company's
attorneys on clarification of EPA's or the State's authority for
inspection under the Clean Air Act and State law.
2. Note the facility name and exact address, the name and title of the
plant officials approached, the authority of the person issuing the
denial (he must be authorized), the date and time of denial, the rea-
son for denial, facility appearance, and any reasonable suspicions
as to why entry was refused.
3. The inspector should be very careful to avoid any situations that
might be construed as threatening or inflammatory. Under no circum-
stances should he cite the potential penalties of entry denial.
4. Lastly, the inspector should withdraw from the premises and contact
his supervisor to decide on a subsequent course of action.
These procedures also apply in the additional case that consent is with-
drawn or partially withdrawn during the inspection. In an EPA "Memorandum
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on Inspection Procedures" (April 11.1979}1, it is stated that all evidence
obtained prior to the withdrawal of consent is considered admissable. When
the inspector is denied access only to certain parts of the plant, he should
make note of this including the area of the plant and the official's reason
for denying access. The Inspection should be completed to the extent allow-
able and then, after leaving the facility, the Agency administration should
be contacted to determine whether a warrant should be obtained to inspect
the portions of the facility not seen.
All observations pertaining to the denial should be carefully noted in
the inspection field notes, they will be important for use in affidavit
writing if a warrant is later sought.
12.2.6.1 Warrants - In the event that a plant official persists in refusing
plant entry or withdraws consent during the course of an inspection, an
administrative or criminal warrant may be used to gain entry into the plant.
A warrant is a judicial authorization for an appropriate official to enter a
specifically described location and perform specifically described inspection
functions. The inspector should always confer with his supervisor to deter-
mine that this course of action is the most appropriate.
There are two types of warrants: criminal and civil (or administrative)
warrants. Administrative inspection warrants are the type most often sought
the case of plant entry denial; criminal search warrants are only used in
cases where the inspection is intended, in whole or in part, to gather evidence
for a possible criminal prosecution. To obtain a criminal search warrant, one
must be able to demonstrate criminal probable cause which is based on whether
a person of ordinary caution and prudence would be led to believe and con-
scientiously entertain a strong suspicion of a violation. Administrative
warrants are issued upon the showing of (1) civil probable cause or (2) that
the establishment was selected for inspection pursuant to a neutral adminis-
trative inspection scheme. Showing civil probable cause consists of demon-
strating specific evidence of an existing violation. A neutral or reasonable
Inspection scheme would include schemes such as annual inspections of permit
holders in a given program.1
When securing a warrant three documents have to be drafted, an application
for a warrant, an accompanying affidavit and the warrant itself. The applica-
tion identifies the statutes and regulations under which the Agency seeks the
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warrant. In addition, it clearly identifies the site or establishment to be
inspected including, if possible, the name of the owner and/or operator.
The affidavit(s) in support of the warrant application contain the fac-
tual background for seeking the warrant. An affidavit is a sworn statement
signed by someone with personal knowledge of the facts stated therein and
witnessed by a notary public or the magistrate. In cases where entry to a
plant has been denied, at least one affidavit would be signed by the inspector
who was refused entry. An affidavit for a warrant sought in the absence of
probable cause should incorporate the neutral administrative Inspection
scheme which was the basis for attempting to Inspect that particular esta-
blishment.
The inspector works in conjunction with the Agency attorney to prepare
the warrant documents. It is not important that the inspector be able to word
his affidavit in proper legal terminology, but that he has carefully recorded
at the time denial of entry, and obtained previous to the inspection, the
pertinent information needed to write the warrant application and affidavit:
o Address of premises,
o Names and titles of owner and authorized person who refused entry,
o Time and place of refusal,
o Reason for refusal,
o Reason for inspection, and
o Description of premises and equipment to be inspected
It is important that the warrant specify to the broadest extent possible the
areas that are intended to be inspected, the records to be inspected, samples
to be taken, and articles to be seized. In general, the stated scope of
inspection in civil warrants can be broader than in criminal warrants.
When the agency attorney completes the preparation of the legal docu-
ments, they must be presented to the proper judge for his signature on the
warrant to render it legally binding. For an inspection by EPA authority,
the warrant would be signed by a U.S. Attorney; state inspection warrants
are signed by a state judge. The assisting attorney should be able to direct
the state inspector to the proper court and judge. The judge has the option
of questioning the applicant and any other witnesses before deciding to
issue the warrant.
The conditions of serving a warrant vary from state to state and with
the federal courts, but some common things to be aware of are:
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o Required notice to the source .that a warrant has been issued,
o Effective time for execution and return of warrant to the court,
o Reasonable time for inspection (e.g. during normal working hours), and
o Restrictions on forcible entry.
When the inspector serves the warrant on the facility owner or his autho-
rized representative, a copy of the warrant should be left with the plant offi-
cial. The inspection must be conducted strictly in accordance with the speci-
fications of the warrant. The inspector who conducts an illegal search can be
liable for civil damages. If samples or records are taken, receipts must be
issued. The inspector must maintain an inventory of all such property taken
from the premises.
When the inspection has been completed, the warrant is returned to the
magistrate. The person serving the warrant usually signs the return of ser-
vice. A copy of the inventory of property removed from the facility premises
must be submitted to the court upon return of the warrant and the inspector
should be present to certify that the inventory is correct.
There are three conditions under which a facility may be inspected with-
out the company being justified in requiring a warrant. The first condition
would be in an emergency when there is not enough time to obtain a warrant.
Emergency situations include potential imminent hazard situations and situa-
tions where evidence might potentially be destroyed or the violation will
disappear before a warrant can be obtained. If the facility refuses entry
under these situations, the inspector would need the assistance of a state
or U.S. Marshall to gain entry. Secondly, observations by inspectors of
things that are in plain view, things that a member of the public could be
in a position to observe, also do not require a warrant. This includes
observations made from the public area of a plant or from private property
which is not normally closed to the public. Third, some types of abatement
programs specifically require right of warrantless entry.1
It should be mentioned here that several special instances exist where
an inspector might seek a warrant before there has been any denial of entry
to a facility. These include instances when surprise is particularly crucial
to the inspection, when a company's prior refusals or other bad conduct
Indicate it will be likely that entry is denied again, or when the distance
to a U.S. Attorney or magistrate is so considerable that excessive travel
time would be wasted if entry were refused.1
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12.2.7 Preinspection Interview
Every inspection should begin with a preinspection interview. The in-
spector should plan this initial interview with the plant owner, manager or
other authorized official prior to the in-plant inspection. During this
interview he should discuss the following points:
1. The purpose and scope of the inspection, ,.. »
2. The type of measurements to be made, and the type of samples (tf any;
to be acquired,
3. The operational status of all process and pollution control equipment
to be evaluated,
4. Inspector's preferred inspection agenda,
5. Changes in plant management that need to be noted in the agency files,
6. Plant safety requirements,
7. Scheduling of a post-inspection Interview,
8. Operating records required by Standards of Performance for New
Sources (NSPS) and/or for determinations of operating conditions
specified in permits,
9. Applicable regulatory requirements and their specific applications,
10. Company's right to request confidentiality of business information,
11. Whether photographs are allowed, and
12. Union agreements.
In regard to confidentiality, it is most important that the inspector be
prepared to discuss how his agency or organization handles information claimed
confidential Including the procedures involved in determining confidentiality.
A suggested methodology concerning handling business confidential information
can be found in Section 12.5.
Other issues the Inspector should be prepared to discuss in the event
that company officials have any questions concerning them include:
1. Authority for the Inspection,
2. Agency organization, and
3. Details of new or existing regulations.
The inspector should request that a company official accompany him during the
inspection to answer questions and to facilitate designation of confidential
business data.
12.3 FIELD PROCEDURES
The inspector should respect all union-company agreements. If these
agreements so require, the Inspector should request that union personnel make
any necessary measurements and acquire any samples. This 1s done under the
supervision of the company representative and with the guidance of the
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inspector. The assistance of union personnel considerably accelerates the
field work since these individuals have the proper tools, and are thoroughly
familiar with the locations of static pressure taps, measurement ports, and
control equipment instruments. The inspector should not seek information
from union personnel regarding the operation and maintenance at the plant.
This is unfair to both the union personnel and the plant representative since
the union operators are not. authorized to release this information and may
not be aware of the confidential nature of some of the information.
The inspector should keep 1n mind the public relations liason part of
his role as inspector and seek to develop or improve the good working
relationship with the plant officials. An inspector can do this by adhering
to the following common sense rules:
1. Remain courteous at all times, and
2. Respect the normal working schedule of the plant personnel.
12.4 POST-INSPECTION PROCEDURES
12.4.1 Post-inspection Interview
Having evaluated the exhaust systems, monitoring equipment control
systems, and possibly the processes themselves, the inspector should again
meet with a plant official to:
1. Ask follow-up questions as necessary,
2. Ensure that all confidential Information has been noted in the field
data sheets,
3. Review inspection notes so that there is general agreement on the
technical facts,
4. Discuss need for a follow-up inspection or additional records, and
5. Prepare and deliver receipts for any samples taken.
Under no circumstances during these discussions should the inspector
make judgements or conclusions concerning the compliance of the source with
applicable regulations. He may state matters of fact (i.e. smoke opacity at
a certain stack exhaust point was 20%), but should not relate these to facility
compliance.
12.4.2 File Update and Report Preparation
The source files, Including Inspection reports, are the agency's source
of Information on any particular facility, thus the inspectors contribution
1n updating the files and preparing Inspection reports is most vital.
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As soon as possible after arriving .back at the office, while all the
events of the inspection are still fresh in his nrind. the inspector should
change all appropriate file entries. He should also begin preparing his
inspection report. Most agencies have a preferred report style, so specific
format will not be dealt with in this document. The report should, though,
include (1) the conclusions of the inspector based on observations and cal-
culations stated clearly 1n.concise paragraphs, (2) the control device diag-
nostic checklists found 1n Appendix D, and (3) a cover page (see example
shown 1n Table 9) with the following Information:
-Any change 1n responsible plant personnel,
-Requested permit changes or reported process modifications,
-Results of the Counterflow evaluation,
-Action requested,
-Inspector's signature, and
-Date of Inspection.
A copy of the report should be kept both 1n the inspector's "working" file
and 1n the agency's central file.
12.5 HANDLING CONFIDENTIAL BUSINESS INFORMATION
Industry is becoming increasingly sensitive to and aware of agency use
and disclosure of confidential business information. This subject has become
a major point of contention 1n regard to allowing Inspectors on plant property.
For this reason, 1t 1s especially Important for all agencies performing
Inspections to adopt rules and guidelines for the handling of confidential
business information. The presentation to companies of an organized, secure
scheme for confidential information handling will do much to increase their
confidence in an agency and their rapport with Its representative plant inspec-
tors.
As the current time the Environmental Protection Agency and most State
agencies have established policies and procedures for handling proprietary
Information. Most of these include penalties for wrongful disclosure and
formal procedures for safeguarding privileged information. Penalties for
Federal employees, for example, are fines up to $1,000 and one year in prison
and dismissal from employment and are set forth in the Code of Federal
Regulations, 40 CFR Chapter 1, Part 2, Section 2.211 and the United States
Code, Title 18, Section 1905. State and local agency employees should check
with agency attorneys to determine their personal liability. When state and
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local agencies are delegated authority for the New Source Performance Stan-
dards and National Emission Standards for Hazardous Air Pollutants by EPA,
then they may be liable under the same provisions as Federal employees.
12.5.1 Defining Confidential Business Information
From the inspector's standpoint, confidential information may be defined
as information received under a request of confidentiality which may concern
or relate to trade secrets, processes, operations, style of work or apparatus,
or the identity, confidential statistical data, amount or source of any in-
come, profits, losses, or expenditures. This information could be in written
form, in photographs, or in the inspector's memory.
12.5.2 Suggested Handling Procedures
This section summarizes a suggested set of procedures to be used by the
inspector and the agency in safeguarding confidential information obtained
during field inspections. Although each inspector and agency may use somewhat
different procedures depending on the agency policies, this section should
serve to bring to the inspector's attention the typical methods used in
handling privileged information.
12.5.2.1 Receipt of Confidential Business Data - As stated previously, the
inspector must be careful to identify all privileged information collected
during an inspection. And, since confidential information involves extra
paperwork and possible legal consequences, he should avoid collecting any
privileged information unnecessarily. Plant officials should be given an
opportunity to identify privileged information and to request confidentiality.
They should also be informed, if agency policy, that they may also request
confidentiality at a later time assuming the data has not already been dis-
closed. The inspector should not, in any case, speculate whether the data
in question will eventually be considered confidential; this determination is
a legal and administrative policy decision and not within the inspector's
authority.
While the field inspector is on the road, inspection documents containing
privileged information should be marked and kept in a locked briefcase, while
physical samples should be marked and kept in a locked container. The com-
plete inventory of confidential information received should be compiled by
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stamping each page received with an ink -stamp similar to that shown below.
At the conclusion of an on-site inspection, the inspector should prepare a
list of all documents received which indicates the following:
(1) A concise, general description of each document,
(2) The total number of pages, and
(3) A document number.
CLAIMED CONFIDENTIAL
DOCUMENT—— PAG
REC'D. """" OATE
REC-D. "»v PN
12.5.2.2 Handling in the Office - Immediately upon return to the agency, the
potentially confidential information (data, charts, drawings, etc.) should be
placed in a secure, lockable file cabinet designated especially for confiden-
tial information. Records should be kept of every person who uses a document;
this may be in the form of a sign out sheet for each document. In addition,
it may be useful in keeping document exposure to a minimum, that each document
bear an attached list of these persons authorized to use it.
In general, confidential documents should not be reproduced. If, for
some reason, it becomes necessary to copy privileged information, all copies
should be included in the confidential document inventory and accounted for
as would be an original.
12.5.2.3 Privileged Data and Report Preparation - In preparing the inspec-
tion report, it is recommended that confidential information be reference in
a non-confidential manner (i.e., by reference to the document in the confi-
dential files and a general description of the information contained therein).
If necessary, the confidential data may be included in the report, but the
entire report must then be treated as a confidential document.
12.5.2.4 Potentially Confidential Information - Although all inspections
should include ample opportunity for plant officials to request confidential
handling of designated data, every allowance should be made to safeguard
potentially confidential data (it may be stamped "Confidential--Pending
Company Review") until a company Indicates its intentions or submits a written
request. In cases where an agency has questions concerning the confidenti-
ality of certain information, they may forward the information or inspection
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report to a responsible industry official for company review. The official
should be requested by cover letter to review the report and to clearly mark
any data considered confidential. Until the reviewed report is returned the
data included should be treated as privileged information.
12.6 USE OF PHOTOGRAPHIC DOCUMENTATION
Photographic documentation of an emission source, though useful in some
aspects, often elicits a negative reaction from plant officials. Therefore,
1t is the opinion of the authors that in most cases the inspection can be
conducted as effectively and usually more efficiently without the use of
photographic documentation. There will be some cases, however, where an
Inspector or his agency will require photographs of control devices and/or
associated equipment. This section details a suggested methodology for
photographic documentation and includes some particulars on the legal aspects
of taking photographs of/within the private areas of a company's premises.
Section 114 of the Clean Air Act may be interpreted to say that an
inspector can take photographs of plant equipment to document his inspection.
Like other proprietary information, EPA and other agencies can require that a
source allow photographs to be of equipment that might reveal trade secrets.
But, in almost all instances it is best to avoid photographing any sensitive
areas and to limit photographs to only those which are absolutely necessary.
For the purposes of inspections covered by this manual, the photographs will
generally be of air pollution control equipment and any proprietary feature(s)
in the backgound can be shielded.
Prior to taking any photographs the inspector should consult with the
plant official (1) about plant policy concerning photographs and (2) to obtain
consent. This is mostly conveniently accomplished during the pre-inspection
interview. The inspector may offer to provide the official with duplicates
of all photographs taken. As with other business data collected, during
and/or at the conclusion of the inspection, the inspector should ascertain
whether any of the photographs taken contain proprietary information and if
the company wishes to designate any as confidential. Photographs taken
employing a Polaroid-type instant camera are useful for inspections because
they allow an immediate confidentiality review and the opportunity for the
inspector to readily provide the company with duplicate shots.
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The inspector must be exacting in -his photographic techniques because
all photographs must be authenticated and thoroughly identified if they are
to be used as evidence in a court of law. When a photograph is introduced as
evidence, the photographer, or on occasion another person familiar with the
subject pictured, must affirm that the reproduction is a "fair representation"
of what it is trying to show. To help ensure that this is true for his
photographs, the inspector should take Into account the type of lenses,
filters and film he uses so as not to Introduce any photographic artifacts.
He should also endeavor to take photographs that include some indication of
(1) the scale of the object being photographed, (2) its location in the scheme
of the plant (if possible, without including proprietary information), and
(3) the direction from which the photograph was taken.
Every photograph must be logged in the inspector's field notes. This log
should include:
o Photo ID number,
o Type of film, lens, filters used,
o Date,
o Time,
o Location,
o Subject and purpose,
o Photographer's initials.
Polaroid-type instant photos should be immediately identified on the back
after shooting with the corresponding photo ID number. Photographs which
require developing and printing should be numbered as soon after these as
possible. Photogaphs of a confidential nature must be developed by an
authorized contractor.
12.7 REFERENCE
1. "Memorandum on Inspection Procedures (April 22, 1979)," from the Assistant
Administrator for Enforcement to Regional Administrators, Surveillance
and Analysis Division Directors, and Enforcement Division Directors, U.S.
Environmental Protection Agency, published in The Environment Reporter,
Bureau of National Affairs, Inc., Washington, D.C., 6-8-79, pp 9-23.
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