United States
Environmental Protection
Agency
Air Pollution Training Institute
MD20
Environmental Research Center
Research Triangle Park, NC 27711
EPA 460/2-82-0
August 1982
Air
APTI
Course Sl:417
Controlling VOC Emissions
from Leaking Process
Equipment
Student Guidebook
Developed and designed by:
Gerald T. Joseph, P.E.
Marilyn Peterson
Northrop Services, Inc.
P.O. Box 12313
Research Triangle Park, NC 27709
Under Contract No.
68-02-3573
EPA Project Officer
R. E. Townsend
United States Environmental Protection Agency
Office of Air, Noise, and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, NC 27711
U S
„+*! protection Agency
S Environmental Proiev.
Chicago.
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Notice
This is not an official policy and standards document. The opinions and selections
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 evaluation. Any mention of products or organiza-
tions does not constitute endorsement by the United States Environmental Protec-
tion Agency.
Availability
This document is issued by the Manpower and Technical Information Branch,
Control Programs Development Division, Office of Air Quality Planning and Stan-
dards, USEPA. It was developed for use in training courses presented by the EPA
Air Pollution Training Institute and others receiving contractual or grant support
from the Institute. Other organizations are welcome to use the document.
This publication is available, free of charge, to schools or governmental air
pollution control agencies intending to conduct a training course on the subject
covered. Submit a written request to the Air Pollution Training Institute, USEPA,
MD 20, Research Triangle Park, NC 27711.
Others may obtain copies, for a fee, from the National Technical Information
Service (NTIS), 5825 Port Royal Road, Springfield, VA 22161.
u
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Table of Contents
Page
Lesson 1. Controlling VOC Emissions from Leaking Process Equipment 1-1
Course Overview 1-1
Course Description 1-1
Course Goal and Objectives 1-1
Lesson Titles 1-2
Requirements for Successful Completion of this Course 1-2
Materials 1-2
Use of this Guidebook 1-2
Instructions for Completing Final Exam 1-3
Lesson 2. Background for Fugitive VOC Regulations 2-1
Lesson Goal and Objectives 2-1
Introduction 2-1
Regulations 2-3
Glossary 2-3
Lesson 3. Potential Sources of Fugitive VOC Emissions 3-1
Lesson Goal and Objectives 3-1
Introduction 3-1
Process Equipment—Leaks • 3-2
Other Potential VOC Emission Sources 3-16
Emission Factors 3-19
Lesson 4. Control of Fugitive VOC Leaks from Process Equipment 4-1
Lesson Goal and Objectives 4-1
Introduction 4-1
Control Devices 4-2
Leak Detection and Repair Techniques 4-7
Structure of Regulations for Leak Detection and Repair 4-13
Lesson 5. Portable VOC Detection Devices 5-1
Lesson Goal and Objectives 5-1
Introduction 5-1
Operating Principles 5-1
Performance Criteria and Evaluation Procedures for Portable VOC Detectors 5-6
Safety 5-8
Lesson 6. Inspection Procedures 6-1
Lesson Goal and Objectives 6-1
Introduction 6-1
Pre-inspection Preparation 6-1
General Field Procedures 6-5
m
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Appendix A. Method 21. Determination of Volatile Organic Compound Leaks A-l
Appendix B. Response Factors of YOG Analyzers for Selected Organic Chemicals B-l
Appendix C. Portable VOC Detection Devices C-l
Appendix D. Number of Fugitive VOC Emission Sources for a Typical
Refinery, Chemical Unit and Gas Plant D-l
IV
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Lesson 1
Controlling YOG Emissions
from Leaking Process Equipment
Course Overview
Course Description
This course is designed for technical people involved in monitoring industries for VOC
emissions from leaking process equipment. The course reviews in detail the sources of
fugitive VOC emissions and the procedures and equipment used to detect leaks. Course
topics include:
Introduction to source categories and regulations
Potential sources of emissions
Inspection procedures
Devices used to detect leaking components
Equipment and procedures used to control leaks
Course Goal and Objectives
Goal
To familiarize you with the sources of VOC emissions and with methods used to detect
and control leaks.
Objectives
Upon completion of this course, you should be able to:
1. describe what constitutes a leak.
2. recognize five major components that may leak.
3. identify control techniques and hardware used to prevent components from leaking.
4. name three methods used to detect leaks.
5. describe the procedures for using a portable VOC detector to detect a leaking
component.
6. describe the operation of two portable VOC detection devices.
1-1
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Lesson Titles
Lesson 1: Course Overview
Lesson 2: Background for Fugitive VOC Emission Regulations
Lesson 3: Potential Sources of Fugitive VOC Emissions
Lesson 4: Control of Fugitive VOC Emissions from Process Equipment
Lesson 5: Portable VOC Detection Devices
Lesson 6: Inspection Procedures
Requirements for Successful Completion
of this Course
In order to receive 2.0 Continuing Education Units (CEUs) and a. certificate of course
completion, you must:
1. take one mail-in final examination.
2. achieve a final course grade of at least 70% based on the final examination.
Materials
SI:417 Guidebook, Controlling VOC Emissions from Leaking Process Equipment
SI:417 Final exam; 40 questions
The content of some of the lessons in this guidebook has been adapted from EPA
documents. The applicable documents are referenced at the end of these lessons.
Use of the Guidebook
This guidebook directs your progress through the text material for this course. This first
lesson introduces the rest of the course material and explains how to use it. Lessons 2
through 6 are self-paced in a text format that provides review exercises for sections of each
lesson. To complete a review exercise, place a piece of paper across the page covering the
questions below the one you are answering. After answering the question, slide the paper
down to uncover the next question. The answer to the first question will be given on the
right of the page separated by a line from the second question (Figure 1-1). All answers
for review questions will appear below and to the right of their respective questions. The
answers will be numbered to match the questions.
1-2
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Review Exercise
1. Question lonlo
nlli cllo ylloimlM
2. Question oli <>«il
It iiluouyic <>
3. Question > IN lot
^N^lo nil i cllo yllon
1. Answer
nlio
2. Answer
"|i-"iil|'_
Figure 1-1. Review exercise format.
Complete the review exercise for each section in each lesson. If you are unsure about a
question or answer, review the lesson section preceding the question. Then proceed to the
next section.
Lesson Content
Lessons in this guidebook contain the following information:
• lesson goal
• lesson objectives
• text material
• review exercises and exercise answers
Instructions for Completing the Final Examination
Contact the Air Pollution Training Institute if you have any questions about the course or
when you are ready to receive a copy of the final examination.
After completing the final exam, return it and the answer sheet to the Air Pollution
Training Institute. The final exam grade and course grade will be mailed to you.
Air Pollution Training Institute
Environmental Research Center
MD 20
Research Triangle Park, NC 27711
1-3
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Lesson 2
Background for Fugitive VOC
Emission Regulations
Lesson Goal and Objectives
Goal
To familiarize you with the regulations and terminology used when controlling VOC leaks
from process components such as valves, pump seals, and compressor seals.
Objectives
Upon completing this lesson, you should be able to:
1. define what constitutes a leaking component.
2. list three industries which have considered, proposed, or promulgated regulations
to reduce fugitive VOC emissions.
3. state the difference between CTG, NSPS, and NESHAPs.
Introduction
The National Ambient Air Quality Standards (NAAQS) for Ozone (Os) were revised on
February 8, 1979. Ozone is seldom emitted directly into the atmosphere, but results
primarily from a series of complex chemical reactions between organic compounds and
nitrogen oxides in the presence of sunlight. In order to meet the NAAQS, the Clean Air
Act requires States to promulgate regulations which will limit the amount of organic com-
pounds that can be emitted from various sources.
Major sources of hydrocarbon emissions were identified and placed on the EPA priority
list. The list ranks source categories in terms of the quantities of nationwide pollutant
emissions, the mobility and competitive nature of each source category, and the
anticipated danger to public health or welfare. Two categories that specifically address
fugitive emission sources appear on the list: petroleum refineries and synthetic organic
chemicals manufacturing (SOCMI). Other source categories also address fugitive emis-
sions. Fugitive emissions are those volatile organic compounds (VOCs) released into the
atmosphere when the gaseous or liquid hydrocarbon fluid that is being processed leaks
from plant equipment or is exposed to the atmosphere. Pump seals, compressor seals,
valves and flanges are a few samples of process equipment that may leak; while cooling
towers, wastewater treatment and separating systems are examples of potential fugitive
2-1
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emissions sources due to exposure. Table 2-1 lists the industries for which standards or
guidelines governing fugitive emissions are being considered, proposed, or promulgated.
Table 2-1. Source categories that emit fugitive VOCs.
Source category
Petroleum refineries
Synthetic organic chemicals manufacturing
industry
Polymers and resin manufacturing
Natural gas and natural gasoline processing
plants
Benzene in coke ovens/by-products plants
Vinyl chloride sources
Benzene fugitive sources
Type of control guidance
CTG*, NSPS*
CTG, NSPS
CTG, NSPS
CTG, NSPS
NESHAPs*
NESHAPs
NESHAPs
•CTG: Control Technique Guidelines
NSPS: New Source Performance Standards
NESHAPs: National Emission Standards for Hazardous Air Pollutants
As can be seen from Table 2-1, there are numerous industries that emit fugitive VOCs.
However, the sources of fugitive emissions, methods by which emissions are detected and
repaired, and control procedures are very similar for each of these industries. This self-
instructional course presents information about the inspection and control of VOC emis-
sions from various pieces of process equipment. Generally, the information presented will
apply to process equipment regardless of industry. However, most of the information is
based on data from petroleum refineries and synthetic organic chemical manufacturing
industries (SOCMI).
Review Exercise
1. True or False? Ozone is emitted from many refiner-
ies, chemical plants, and other industries that
process hydrocarbons.
2. True or False? The EPA develops its Priority List
for ranking emission sources based only on the
amount of pollutants emitted.
1. b. Fake
3. True or False? Sources of fugitive VOC emissions
vary greatly depending on the type of industry.
2. b. False
3. b. False
2-2
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Regulations
Two types of Federal regulations pertain directly to fugitive VOC emissions. The regula-
tions are the New Source Performance Standards (NSPS) and the National Emission
Standards for Hazardous Air Pollutants (NESHAPs). The Federal Government also
publishes Control Technique Guidelines (CTG); the guideline documents are not regula-
tions, but only serve as an information base from which State and local agencies can
develop their own regulations. In the past, most State and local agencies have adopted
regulations very similar to the CTG documents. However, these agencies have adopted dif-
ferent regulations when local sources have needed special attention.
NSPS apply to all new stationary sources, the construction or modification of which
commences after the regulations are proposed by publication in the Federal Register.
Regulations developed by States (from the CTG) apply to all existing stationary sources,
but generally only in areas that are nonattainment for that particular pollutant (in this
case O3). The NESHAPs regulations apply to both new and existing stationary sources, no
matter where they are located. With three different regulatory levels, some overlap occurs.
In these cases, the most stringent of the regulations apply.
Regulations for controlling fugitive emissions from the various industries listed in Table
2-1 are similar. The regulations all require:
1. use of specific equipment or the inspection of processing equipment at various pre-
determined time intervals.
2. provisions for repair of leaks and maintenance of equipment.
The main difference between regulations for the various industries is in the frequency
that a piece of process equipment must be monitored to detect leaks. In some cases,
especially under the NESHAPs and NSPS, additional equipment may be specified to
ensure leak-proof operation.
No attempt is made in this course to cover the specific regulations governing each of the
seven source categories listed in Table 2-1.
Glossary
The following are a few of the important terms used when discussing fugitive VOC
emissions:
Action level—A measured concentration value obtained with a portable VOC monitor.
It indicates the need for repair.
Directed maintenance—Refers to a maintenance procedure in which the hydrocarbon
detector is used during maintenance. The leak is monitored with the instrument until
the repair reduces the measured concentration below the action level.
Fugitive emissions of VOC— Generally refers to the diffuse release of vaporized
hydrocarbon or other organic compounds. Fugitive emissions originate from equipment
leaks and from large and/or diffuse sources.
Leak—A measured VOC concentration of the action level or greater, determined at a
specified distance from the fugitive emission source (usually 0 cm). The concentration
2-3
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value that defines a leak can vary, depending on the regulation and the industry. A value
of 10,000 parts per million by volume (ppmv) is by far the most often used and will be
used in this course unless otherwise noted.
No detectable emission—A local VOC concentration at the surface of a source that
indicates that a VOC emission (leak) is not present. Since background VOC concentration
may exist, and to account for instrument drift and imperfect reproducibility, a difference
between the source surface concentration and the local ambient concentration is deter-
mined. A difference based on a meter leading of less than 5% of the leak definition con-
centration indicates that a VOC emission is not present.
Process stream—Process fluids such as react ants, intermediate products, final products,
and by-products, that are contained within pipes, pumps, valves, etc. in a process unit.
Steam, water, air, and other utility lines are not considered to be process streams.
Process unit—Equipment assembled to produce an organic chemical as an intermediate
or final product. A process unit can operate independently if supplied with sufficient feed
or raw materials and sufficient storage facilities for the final product.
Repair—Adjustment or alteration of leaking equipment which reduces the screening
value from greater than or equal to the action level (i.e., 2:10,000 ppmv) to below the
action level (i.e., < 10,000 ppmv).
Response factor—A correction factor that quantifies the difference in meter response
that a portable VOC analyzer has for various hydrocarbons and substituted organic
chemicals.
Screening—The act of measuring the hydrocarbon concentration of a source with a por-
table hydrocarbon detector.
Screening value—The hydrocarbon concentration (in ppmv) detected at a source with a
portable hydrocarbon detector while traversing with the instrument probe around all the
potential leak points of the source.
Source type—Process unit equipment components that may emit fugitive emissions.
Common source types of fugitive emissions are valves, pump seals, flanges, compressor
seals, and sampling lines.
Type of service—The physical state (g;as, liquid, or both) of the material(s) contained in
a specific pipeline or vessel. The terms liquid and gas are defined at operating condition
of the process. Liquid process streams can be further subdivided into:
• light VOC liquid—any process stream with a vapor pressure of equal to or greater
than 0.3 kPa at 20°C (lighter than kerosene).
• heavy VOC liquid—any process stream with a vapor pressure less than 0.3 kPa at
20 °C.
Volatile organic compound (VOC)—Any organic compound that participates in
atmospheric photochemical reactions.
2-4
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Review Exercise
1. Which of the following does not by itself constitute
a regulatory requirement?
a. NSPS
b. NESHAPs
c. CTG
d. State or local regulations
2. The NSPS apply to all new stationary sources
a. in an attainment area.
b. in a nonattainment area.
c. regardless of location.
1. c. CTG
3. True or False? VOC refers to any organic com-
pound that participates in atmospheric
photochemical reactions.
2. c. regardless of location.
4. The type of liquid service is usually classified as
light or heavy liquid depending on the vapor
pressure of the liquid. For example, a liquid with a
vapor pressure greater than 0.3 kPa at 20 °C is
classified as a
a. heavy liquid.
b. light liquid.
3. True
5. The vaporized hydrocarbons or other organic
compounds that leak from process equipment in
chemical plants, petroleum refineries, and other
industries are called
4. b. light liquid.
5. fugitive emissions.
Reference
Environmental Protection Agency (EPA). May 1981. Evaluation of Maintenance for
Fugitive VOC Emissions Control. EPA 600/2-81-080.
2-5
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Lesson 3
Potential Sources
of Fugitive VOC
Emissions
Lesson Goal and Objectives
Goal
To familiarize you with the sources of VOC leaks
from process equipment.
Objectives
Upon completing this lesson, you should be able
to:
1. recognize at least three types of process
equipment that may potentially leak.
2. describe the potential leak areas for the
above three sources.
S. recognize leak rate emission factors and the
limitations on these using references such as
AP-42.
Introduction
There are many potential sources of fugitive VOC
emissions. The sources that will be considered in
this lesson include: pump seals, compressor seals,
process valves, pressure relief devices, and agitator
seals. The operation of these sources and their
potential leak areas will also be presented in this
lesson. Control measures for these sources are
presented in the next lesson.
VOC emissions result not only from leaking
process equipment, but also from direct exposure
of hydrocarbons to the atmosphere. Sampling
systems, drains and waste water systems, and
S-l
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cooling towers all release fugitive hydrocarbons to
the atmosphere. A discussion of the control
technology for these sources as well as for flanges
will be presented in this lesson.
Process Equipment—Leaks
Pumps
Pumps are used extensively by industries to move
organic liquids. The most widely used pump is the
centrifugal pump. Other pumps used are the
positive displacement, reciprocating and rotary
action, canned-motor, and diaphragm pumps.
Most pumps have a moving shaft which is exposed
to the atmosphere (Figure 3-1). The fluid being
moved inside a pump must be isolated from the
atmosphere. This requires a seal. Leaks can occur
at the point of contact between the moving shaft
and stationary casing. The canned-motor and
diaphragm pumps do not have seals. Therefore,
they effectively prevent leaks.
Moving shaft
Figure S-la. Vertical centrifugal pump.
Stationary
casing
Potential
leak areas
Seal
Figure Jt-lb. Horizontal pump.
3-2
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Pump Seals
Two generic seals currently in use on pumps are
the packed seal and the mechanical seal.
Mechanical seals, the predominant seals in use
today, can be categorized as single or double
mechanical seals. Single mechanical seals are less
effective than double mechanical seals.
Packed Seals
Figure 3-2 is a diagram of a packed seal. Packed
seals can be used on both reciprocating and cen-
trifugal (rotary action) pumps. Centrifugal pumps
are more widely used. The packing material is
compressed in the cavity (stuffing box) to form a
seal around the moving drive shaft. A packing
gland is used to apply the needed compression.
Lubrication is required to prevent frictional heat
buildup between the seal and the shaft. A suffi-
cient amount of either the liquid being pumped or
a supplementary liquid must be allowed to flow
between the packing and the shaft to provide the
necessary lubrication.
Single Mechanical Seals
Figure 3-3 is a diagram of a basic, single
mechanical seal. A mechanical seal prevents
leakage by means of two sealing elements, one sta-
tionary and one rotating. The two sealing elements
are also referred to as the primary ring (usually
the rotating one) and the mating ring (stationary).
The surfaces or faces where the two rings contact
are polished (lapped) to a very high degree of
flatness to maintain contact over their entire
material surface, providing a nearly complete seal.
Note that the sealing faces are perpendicular to
the shaft rather than parallel to it as in the packed
seal.
Mechanical seals can also be equipped with
secondary seals. Secondary seals prevent leakage
between the rotating ring and shaft, the stationary
ring and gland plate, and the stuffing box housing
and gland ring. The secondary seals are often flex-
ible O-rings, as pictured in Figure 3-3.
. .
Stationary
Packing
Pumped
liquid
Figure $-2. Simple packed ml.
Springs
Secondary seals
(O-rings)
Seal facing'
Rotating
ring
Potential
leak area
Figure 5-5. Single mechanical teal.
3-3
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Mechanical seals, even equipped with secondary
seals, are not leak-proof. As with packed seals, the
seal faces must be lubricated to remove frictional
heat. Depending on the condition of the seal and
degree of flatness of the seal faces, the leakage rate
can be very low. The seal coolant is usually the
pumped liquid. If it is a poor lubricant, other
fluids compatible with the liquid being pumped
are used.
Double or Dual Mechanical Seals
Double mechanical seals are generally more effec-
tive in preventing leaks than are single seals.
Double mechanical seals can be arranged either
back-to-back or in tandem. There is a closed
cavity between the two seals in a back-to-back
arrangement (Figure 3-4). A seal liquid, such as
oil or water, is circulated through this seal-housing
cavity. In order for the seal to function, the seal
liquid must be at a pressure greater than the
operating pressure of the liquid being pumped at
the stuffing box. As a result some liquid will leak
across the seal faces passing into the stuffing box
and also out past the outer seal face to the:
atmosphere. The seal liquid should be non-
contaminating so that it will not contaminate
either the pumped liquid or the atmosphere.
In the tandem mechanical seal arrangement
(Figure 3-5), both seals face the same direction.
The inner seal is located in the stuffing box
housing rather than in the seal housing. The
liquid used for lubrication is referred to as the
barrier fluid and is kept at a lower pressure than
the fluid in the stuffing box. Therefore, any
leakage will be from the stuffing box into i:he seal
cavity containing the barrier fluid. The barrier
fluid is routed to a closed reservoir, and any
process fluid that has leaked into the seal cavity
will also be transferred to the reservoir. To ensure
that no VOCs leak from the reservoir, the reservoir
can be vented to a control device.
Sealless Pumps
Another pump that has been used is the sealless
(or shaftless) pump, which includes the canned-
motor pump and the diaphragm pump. In. a
Potential
leak area
Seal liquid
outlet
Figure 3-4. Double mechanical teal
(back-to-back arrangement).
Barrier
fluid inlet
Barrier fluid
outlet
Figure 5-5. Tandem mechanical teal arrangement.
3-4
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canned-motor pump, the cavity that houses the
motor rotor and the pump casing are intercon-
nected. As a result, the motor bearings operate in
the process liquid. All seals are eliminated.
Because the process liquid also lubricates the bear-
ings, abrasive solids cannot be tolerated. Canned-
motor pumps are being widely used for handling
organic solvents, organic heat transfer liquids,
light oils, and many toxic or hazardous liquids.
They are also used where leakage is an economic
problem.
Diaphragm pumps (Figure 3-6) perform some-
what like piston and plunger pumps. However, the
driving member is a flexible diaphragm made of
metal, rubber, or plastic. Their primary advantage
is the elimination of all packing and seals exposed
to the process liquid. This is an important asset
when hazardous or toxic liquids are handled.
Compressors
Compressors are, basically, pumps that are used in
gas service. Gas compressors used in process units
can be driven by rotary or reciprocating shafts and
therefore need shaft seals to isolate the process gas
from the atmosphere. Rotary shafts may use either
packed or mechanical seals, while reciprocating
shafts must use packed seals. As with the seals in
pumps, the seals in compressors are likely to be the
source of fugitive emissions from compressors.
Compressor Seals
Shaft seals for compressors may be labyrinth seals,
restrictive carbon ring seals, liquid film seals, or
mechanical contact seals. All of these seals are leak
restriction devices; none of them completely
eliminate leakage. Many compressors may be
equipped with ports in the seal area to evacuate
gases collecting there. If vented to the atmosphere
these ports can be a source of fugitive emissions.
Diaphragm
Piston
Figure 3-€. Diaphragm pump.
3-5
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Labyrinth Seals
The labyrinth compressor seal is composed of a
series of close tolerance, interlocking teeth that
restrict the flow of gas along the shaft. A straight-
pass labyrinth compressor seal is shown in Figure
3-7. Many variations in tooth design and materials
of construction are available. Although labyrinth
seals have the largest leak potential of the different
types, properly applied variations in tooth con-
figuration and shape can reduce leakage by up to
40% over a straight-pass labyrinth seal. However,
the loss and recycle rates are usually not accep-
table from either environmental or energy conser-
vation standpoints.
Restrictive Carbon Ring Seals
Restrictive carbon ring scab consist of multiple sta-
tionary carbon rings with close shaft clearances.
This seal may be operated dry or with a sealing
fluid. A restrictive ring seal can achieve lower leak
rates than can the labyrinth type.
Liquid Film Seals
Centrifugal compressors can be equipped with
liquid film seals. The seal is formed by a film of
oil between the rotating shaft and stationary
gland. When the circulating oil is returned to the
oil reservoir, process gas can be released to the
atmosphere. To eliminate release of VOC emis-
sions from the seal oil system, the reservoir can be
vented to a control device.
Mechanical Contact Seal
Mechanical contact seals for compressors are
similar to the mechanical seals described for
pumps. This seal reduces the clearance between
the rotating and stationary elements to essentially
zero. Oil or another suitable lubricant is applied to
the seal faces. Mechanical seals can achieve the
lowest leak rates of the seals described here, but
they are not suitable for all processing conditions.
Teeth
Potential
leak area
Figure 3-7. Labyrinth ihaft teal.
3-6
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Review Exercise
1. Two generic types of seals used on pump shafts are
a. single mechanical seals and centrifugal seals.
b. packed seals and mechanical seals.
c. tandem seals and teeth seals.
2. Only a
. seal can be used on both
reciprocating and rotary action pumps
and compressors.
a. packed
b. mechanical
c. tandem
d. centrifugal
1. b. packed seals and
mechanical seals.
3. True or False? Unlike packed seals, mechanical
seals need no lubrication between the contact faces
and therefore totally eliminate all leaks.
2. a. packed
4. True or False? In general, the canned-motor pump
and the diaphragm pump have the lowest potential
to leak.
3. False
5. True or False? Although all gas compressors are
similar in operation to pumps, they have no shafts,
and therefore do not leak.
4. True
Besides the seal area, two other potential areas
where fugitive VOC emissions can be emitted from
gas compressors are
a. circulating oil reservoirs.
b. evacuation ports from seal areas.
c. centrifugal ports.
d. tandem seals.
5. False
7. A mechanical seal prevents leakage by means of
two sealing elements, one and one
6. a. circulating oil reservoirs.
b. evacuation ports from
seal areas.
7. stationary (mating)
rotating (primary)
3-7
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Process Valves
One of the most common pieces of equipment in
an industrial plant is the valve. Individually,
process valves have a low emission rate. However,
because of the large number of valves present in
most plants, as a group they usually constitute the
largest percentage of fugitive VOC emissions (see
Appendix D). For example, in a 100,000 g;allon
per day petroleum refinery, there are usually
25,000 process valves as compared to about 250
pump seals. In some instances valves may make up
90% of the process components that must be
checked for leaks.
Many different valves exist, such as globe, gate,
plug, ball, and check valves. However, they can be
grouped into three functional categories:
• Block: used for on/off control. Generally,
these valves are used only occasionally, such as
when there is a process change (i.e., unit
shutdown).
• Control: used for flow rate control.
• Check: used for directional control. These
valves do not have stems, therefore they will
not be covered in this course.
The most common valves in use are the gate
valve and the globe valve. These valves can be
found either in-line or at the end of a process line.
In-line Valves
Valves are activated by a valve stem. Depending
on the design, the valve stem may have either a
rotational or linear motion. (Pressure relief valves
are discussed under a separate heading.) The
process fluid inside the valve must be isolated from
the atmosphere. This requires a seal. The possi-
bility of a leak through this seal makes it a poten-
tial source of fugitive emissions. Figures 3-8
through 3-12 show the potential leak areas from
the stems of some common valves. Since check
valves are enclosed within process piping, they
have no stem or packing gland and are not con-
sidered to be a potential source of fugitive
emissions.
Packing nut
Body
Seat
Figure 3-8a. Manual globe valve.
Disk
Figure: Mb. Globe control valve.
3-8
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Packing nut
Potential
leak areai
Potential
leak areas
Figure S-9a. Nonrifing Mem gate
Figure J-9b. Rising Mem gate Yahre.
Potential
leak area
Disk
Figure 5-10. Butterfly ralve.
3-9
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Potential leak
areas
Figure 3-11. Lubricated plug valve.
Potential
leak area*
Figure 3-12. Ball valve.
3-10
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Valve Seals
Sealing the stem to prevent leakage can be
achieved by applying packing inside a packing
gland or O-ring seal. The most common valve-
stem seal is the packed seal. A specialized packing
material is inserted into the area around the stem,
then compressed by a packing gland to form a
tight seal. The most common packing materials
are various types of braided asbestos that contain
lubricants. Other packing materials include
graphite, graphite-impregnated fibers, and tetra-
fluoroethylene. The packing material used depends
upon the valve application and configuration. At
high pressures these glands must be quite tight to
attain a good seal. As packing wear or lubricant
loss occurs, the packing gland must be tightened
to continue providing a tight seal.
Elastomeric O~rings are also used for sealing
process valves. These O-rings provide a good seal,
but are not suitable where there is sliding motion
through the packing gland. These seals are rarely
used in high pressure service. Operating
temperatures are limited by the O-ring material.
Bellows seals are more effective for preventing
process fluid leaks than are conventional packing
glands or any other gland-seal arrangements. This
seal incorporates a formed metal bellows that
makes a barrier between the disc and body bonnet
joint. An example of this seal is presented in
Figure 3-13. The bellows is the weak point of the
system and its service life can be quite variable.
Consequently, the bellows seal is usually both
backed up with a conventional packing gland and
often fitted with a leak detector in case the seal
fails.
Figure 3-13. BeUowi ml.
3-11
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Specialized valve designs can isolate both the
working parts of the valve and the environment
from the process liquid. This may be done with a
diaphragm seal. Figure 3-14 illustrates two
diaphragm seals on a globe valve; the bonnet seal
and the weir seal. The weir seal's diaphragm may
also be used to control the flow of the process
fluid. In this design, a compressor component
pushes the diaphragm toward the valve bottom,
throttling the flow. The diaphragm and com-
pressor are connected so that it is impossible for
them to be separated under normal working condi-
tions. When the diaphragm reaches the valve bot-
tom, it seats firmly, forming a leak-proof seal.
This configuration is recommended for fluids con-
taining solid particles and for medium-pressure
service. These valves can be used at temperatures
of up to 205 °C and in severe acid solutions
depending upon the diaphragm material used. A
valve using a diaphragm seal can become a source
of fugitive emissions if that seal fails.
Open-ended Valves or Lines
Some valves are installed so that they operate with
the downstream line open to the atmosphere.
Open-ended valves may be used for draining,
venting, or purging. As with the valve stem seal,
the valve seat may also be a source of emissions. A
faulty valve seat or incompletely closed valve would
result in leakage of VOCs to the atmosphere.
Weir
Figure 3-14a. Weir diaphragm teal.
Diaphragm
Figure 5-Mb. Bonnet diaphragm teal.
3-12
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Pressure Relief Devices
Engineering codes require that pressure-relieving
devices or systems be used in applications where
the process pressure may exceed the maximum
allowable working pressure of the vessel. The most
common pressure-relieving device used in process
units is the pressure relief valve (Figure 3-15).
Typically, a relief valve is spring-loaded. It is
designed to open when the process pressure
exceeds a set pressure. This allows the release of
vapors or liquids until the system pressure is
reduced to its normal operating level. When the
normal pressure is reattained, the valve reseats,
and a seal is again formed. There are two poten-
tial causes of leakage from relief valves. One is
simmering or popping, which is a condition caused
by the system pressure being close to the set
pressure of the valve. Simmering occurs when the
operating pressure is similar to the set pressure of
the valve, while popping occurs when the
operating pressure exceeds the set pressure,
generally for an extremely short period. The other
cause of leakage is improper valve reseating after a
relieving operation.
Rupture disks are also commonly used on
process units. These disks can be used in combina-
tion with or in place of pressure relief valves.
These disks are made of a material that ruptures
when a set pressure is exceeded, thus allowing the
system to depressurize. The advantage of a rupture
disk is that it seals tightly and does not allow any
VOCs to escape from the system under normal
operation. However, when the disk does rupture,
the system depressurizes until atmospheric condi-
tions are obtained. This could result in an
excessive loss of product or a corresponding
excessive release of fugitive emissions.
Alternate leak
area if bom
inaccearible
Figure 3-15. Spring loaded prepare relief valve.
Agitators
Agitators are commonly used to stir or blend
chemicals. Like pumps and compressors, agitators
may leak organic chemicals at the point where the
shaft penetrates the casing. Consequently, seals are
required to minimize fugitive emissions from
3-13
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agitators. Four seals are commonly used with
agitators: packed seals, mechanical seals, hydraulic
seals, and lip seals.
Agitator Seals
Packed seals for agitators are very similar in design
and application to the packed seals for pumps.
Although mechanical seals are more expensive
than the other three seals (packed, hydraulic, or
lip), they greatly reduce leakage rate. This offsets
their higher cost. Mechanical seals need less fre-
quent maintenance—one-half to one-fourth that of
packed seals. In fact, when used on agitators at
pressures greater than 1140 kPa (150 psig),
mechanical seals are so superior that the use of
packed seals is rare. Like packed seals, mechanical
scab for agitators are similar in design and
application to mechanical seals for pumps.
The hydraulic seal (Figure 3-16) is the simplest
agitator shaft seal. In the hydraulic seal, an
annular cup attached to the process vessel contains
a liquid that is in contact with an inverted cup
attached to the rotating agitator shaft. The
primary advantage of this seal is that it is a non-
contact seal. However, this seal is limited to low
temperatures and pressures and can handle only
very small pressure fluctuations. Organic chemicals
may contaminate the seal liquid and then be
released into the atmosphere as fugitive emissions.
Therefore, the hydraulic seal is the least used
agitator seal.
A lip seal (Figure 3-17) can be used on a top-
entering agitator as a dust or vapor seal. The
sealing element is a spring-loaded elastomer. Lip
seals are relatively inexpensive and easy to install.
Once the seal has been installed, the agitator shaft
rotates in continuous contact with the lip seal.
Pressure limits of the seal are 2 to 3 psi because it
operates without lubrication. Operating tempera-
tures are limited by characteristics of the elas-
tomer. Fugitive VOC emissions could be released
through this seal when it wears excessively, or
when its pressure limits are surpassed by the
operating pressure.
Atmosphere
Rotating shift
Inverted cup
Process fluid
Figure 3-16. Hydraulic teal for agitators.
Routing shaft
Elastomer
lip seal
Figure 3-17. Lip teal.
3-14
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Review Exercise
1. Generally,
contribute the largest
percentage of fugitive VOC emissions.
a. pump seals
b. flanges
c. valves
d. compressor seals
Process valves can leak through the packing around
the valve
a. stem.
b. gate.
c. globe.
d. check.
1. c. valves
Process valves that are used for on/off control
when there is a process change are referred to as
valves.
a. control
b. block
c. relief
d. check
2. a. stem.
4. True or False? Open-ended valves can leak from
both the valve stem and the seat.
5. b. block
The leakage from relief valves that occurs when the
system pressure is too close to the set pressure of the
relief valve is known as
a. hydraulic or pressure.
b. plugging or checking.
c. blocking or controlling.
d. simmering or popping.
4. True
Rupture disks are used in combination with or in
place of to prevent leaks.
a. pressure relief devices
b. pump seals
c. compressor seals
d. agitators
5. d. simmering or popping
7.
are commonly used to blend or
stir chemicals.
a. Fans
b. Spoons
c. Agitators
d. Valves
6. a. pressure relief devices
7. c. Agitators
S-15
-------
8. True or False? Packed, mechanical, hydraulic,
and lip seals are all used to prevent leaks from
agitators.
9. seals can isolate both the working
parts of the valve and the environment from the
process fluid.
8. True
9. Diaphgram
Other Potential VOC
Emission Sources
Sampling Systems
The operation of a process unit is checked
periodically by routine analysis of feedstocks and
products. To obtain representative samples for
these analyses, sampling lines must be purged
before sampling. The purged liquid or vapor is
sometimes drained onto the ground or into a sewer
drain, where it can evaporate and release VOC
emissions to the atmosphere.
Closed-purge sampling can be used to eliminate
any possible emissions. Closed-purge sampling
systems eliminate VOC emissions either by return-
ing the purge material directly to the process or by
collecting the purge in a closed collection system
for eventual recycle or disposal.
Flanges
Flanges are bolted, gasket-sealed junctions between
sections of pipe and pieces of equipment. They are
used wherever pipe or equipment components
(vessels, pumps, valves, heat exchangers, etc.) may
require isolation or removal. The possibility of a
leak through the gasket seal makes them a poten-
tial source of fugitive emissions (Figure 3-18).
The results of EPA's refinery sampling programs
have shown that flanges have a very low emission
factor. Even though there are many of them in
any refinery or chemical plant, their overall con-
Potential
leak area
Figure 3-18. Flange.
3-16
-------
tribution to the emission rate is small (see Appen-
dix D). Most flanges cannot be isolated from the
process to permit gasket replacement. If a flange is
found to leak, the only repair options are tighten-
ing the flange bolts or injecting a sealing fluid.
Similar potential sources of VOCs are any joint
connections and moving parts that have seals to
keep VOCs from escaping to the atmosphere.
Cooling Towers
Cooling towers remove heat from water used to
cool process equipment such as reactors, con-
densers, or heat exchangers. Cooling water is cir-
culated through the process units (in tubes) and
returned to the cooling tower where the water is
cooled. In the cooling tower, air is circulated
through the water, a portion of the water
evaporates into the air and the remaining water is
cooled by furnishing the heat for this evaporation
process (Figure 3-19).
Figure 3-19. Cooling ton
3-17
-------
Organic fluids can enter the cooling water from
leaking process equipment or as a result of using
contaminated process water as cooling tower make-
up water. VOCs can be released to the atmosphere
as cooling water vaporizes in the tower.
In a recent survey, the majority of cooling
towers tested did not have significant VOC emis-
sions. These cooling towers use indirect (non-
contact) condensation which greatly reduces the
amount of contaminated cooling water entering
the tower. However, if a leak occurs in the process
equipment or if direct contact condensation is
used, VOC emissions can be significant.
The best control for cooling towers is to
minimize the amount of hydrocarbons entering the
tower. Direct contact condensation is used in some
existing plants, but its use is being phased out
because of environmental considerations. Moni-
toring the hydrocarbon input to the cooling tower
is very difficult. Even if elevated concentrations of
hydrocarbons are detected, identifying and repair-
ing the specific leak can be very difficult.
However, if a leak occurs in the process equip-
ment, it is often in the best interests of the plant
to repair it as soon as possible.
Process Drains and Wastewater Systems
Contaminated wastewater can originate from
several sources including (but not limited to) leaks,
spills, pump and compressor seal cooling a ad
flushing, sampling equipment cleaning, and rain
runoff. Contaminated wastewater is collected in
the process drain system and directed to the
wastewater treatment system where hydrocarbons
may be recovered and the wastewater undergoes
treatment as required. Organic compounds; con-
tained in the wastewater can evaporate wherever
wastewater is exposed to the atmosphere. As such,
the primary VOC emission points include the
drain system vents and the surfaces of forebays and
separators.
Several known techniques reduce VOC emissions
from process drains and wastewater separators.
Process drain emissions can be controlled by
reducing the amount of VOC that is spilled or
3-18
-------
otherwise put into the drain system. The drains
can also be controlled by installing inverted
U-bends to trap VOCs within the drain system.
Available data show that only a small percentage
of drains have concentrations greater than 10,000
ppmv. Wastewater separators can be controlled by
covering or enclosing the oily water surface of the
separator. Although uncontrolled wastewater
separator emissions can be quite large, the results
of ongoing studies will need to be reviewed to
determine the magnitude of emissions under
existing controls.
Emission Factors
Data to quantify the uncontrolled levels of emis-
sions from the various sources presented in this
lesson are not available for all the source
categories. Data of this type have been obtained
for the petroleum refining industry and are
presented in Table 3-1. Note that the emission fac-
tors in Table 3-1 are the average for all com-
ponents—both leaking and nonleaking. For exam-
ple, to compute the emissions from pipeline valves
in gas service, multiply 0.059 Ib/hr times the total
number of valves (in gas service) in the refinery.
In addition, it is important to note that these
emission factors were developed from data taken
from refineries without inspection and repair pro-
grams (outlined in Lesson 4). While these
refineries generally repair leaks that are physically
evident (to minimize product loss), equipment is
not repaired specifically to reduce the level of
VOC emissions. Therefore, for refineries that have
VOC emissions maintenance and repair programs,
the emission factors in Table 3-1 are not applicable.
Presently, the EPA is developing a method to
better estimate the emission factors from facilities
having operation and maintenance programs.
(This is also discussed in Lesson 4). The approach
taken is to estimate an emission-reduction effi-
ciency based on the following factors:
Theoretical Maximum Control Efficiency—frac-
tion of total mass emissions for each source type
with VOC concentrations greater than the action
level.
3-19
-------
Leak Occurrence and Recurrence Correction
Factor—Correction factor to account for sources
which start to leak between inspections (occur-
rence) and for sources which are found to be leak-
ing, are repaired, and start to leak again before
the next inspection (recurrence).
Non-instantaneous Repair Correction Factor—
Correction factor to account for emissions which
occur between detection of a leak and subsequent
repair; that is, repair is not instantaneous.
Imperfect Repair Correction Factor—Correction
factor to account for the fact that some sources
that are repaired are not reduced to zero emission
levels. For computational purposes, all sources that
are repaired are assumed to be reduced to .a 1000
ppmv emission level equivalent to a concentration
of 1000 ppmv.
For further information on this method see
EPA, April 1982.
3-20
-------
Table $-1. Fugitive emission factors for petroleum refineries.*
Emission
wurce
Pipeline
valves
Open-ended
valves'
Flanges
Pump seals
Compressor
seals
Process drains
Pressure vessel •
relief valves
(gas service)'
Cooling
towers
Oil/water
separators
Procea
ft ream
type'
II
III
IV
V
I
I
HI
IV
II
V
I
II
Emission
factor
units
Ib/hr-source
fcg/day-source
Ib/hr-source
kg/day-source
Ib/hr-source
kg/day-source
Ib/hr-source
kg/day-source
Ib/hr-source
kg/day-source
Ib/hr-source
kg/day-source
Ib/hr-source
kg/ day-source
Ib/hr-source
kg/day-source
Ib/hr-source
kg/day-source
Ib/hr-source
kg/day-source
Ib/hr-source
kg/day-source
Ib/hr-source
kg/day-source
lb/10« gal
cooling water
kg/10* liters
cooling water
lb/10» bbl
refinery feed'
kg/ 10' liters
refinery feed
lb/101 gal
wastewater
kg/10' liter
wastewater
lb/10» bbl
refinery feed
kg/10' liters
refinery feed
Emi*non f acton
Uncontrolled Controlled
emissions1 emissions
0.059 (0.050-0.110) NA
0.64 (0.32-1.19)
0.024 (0.017-O.OS6) NA
0.26 (0.18-O.S9)
0.0005 (0.0002-0.0015) NA
0.005 (0.002-0.016)
0.018 (0.007-0.045) NA
0.20 (0.08-0.49)
0.005 (0.0016-0.016) NA
0.05 (0.017-0.17)
0.00056 (0.0002-0.0025) NA
0.0061 (0.002-0.027)
0.25 (0.16-0.37) NA
2.7 (1.7-4.0)
0.046 (0.019-0.11) NA
0.50 (0.21-1.2)
1.4 (0.66-2.9) NA
15 (7.1-31)
0.11 (0.05-0.23) NA
1.2 (0.5-2.5)
0.070 (0.023-0.20) NA n
0.76 (0.25-2.2)
0.36 (0.10-1.3) Negligible
3.9 (1.1-14)
6 0.70
0.7 0.083
10 1.2
0.03 0.004
5 0.2
0.6 0.024
200 10
0.6 0.03
Applicable control
tartiiMtloaT
Monitoring and
maintenance program
Installation of cap or
plug on open-end of
valve/line
Monitoring and main-
tenance programs
Mechanical seals; dual
seals, purged seals
monitoring and main-
tenance programs,
controlled degassing
vents
Mechanical seals, dual
seals, purged seals,
monitoring and main-
tenance programs,
controlled degassing
vents
Traps and covers
Rupture disks upstream
of relief valves and/or
venting to a flare
Minimization of hydro-
carbon leaks into
cooling water system.
Monitoring of cooling
water for hydrocarbons
Covered separators
and/or vapor recovery
systems
Emission
factor
rating
A
A
A
A
A
A
A
A
A
A
A
A
D
D
* Overall, less than If,
NA= Not Available
A = Excellent
D* Below Average
by weight of the total VOC emissions are ethane.
3-21
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* The volatility and hydrogen content of the process streams have a substantial effect on the emission rate of some fugitive
emission sources. The stream identification numerals arid group names and description axe:
Stream
identification
numeral
I
II
III
IV
Stream
name
All streams
Gas streams
Light liquid and
gas/liquid streams
Heavy liquid streams
Hydrogen streams
Stream group description
All streams
Hydrocarbon gas/vapor at process
conditions (containing less than 50%
hydrogen, by volume)
Liquid or gas/liquid stream with a
vapor pressure greater than that of
kerosene (>0.1 psia at 100°F or
689 Pa at 38 °C), based on the most
volatile class present at > 20% by
volume
Liquid stream with a vapor pressure equal
to or less than that of kerosene (£0.1 psia
at 100°F or 689 Pa at 38°C), based on the
most volatile class present at >20% by
volume
Gas streams containing more than 50%
hydrogen by volume
' Numbers in parentheses are the upper and lower bounds of the 95% confidence interval for the emission factor.
' The downstream side of these valves is open to the atmosphere. Emissions are through the valve seat of the closed valve.
* Emission factor for relief valves in gas service is for leakage, not for emissions caused by vessel pressure relief.
' Refinery rate is defined as the crude oil feed rate to the atmospheric distillation column.
3-22
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Review Exercise
1. Fugitive emisisons of VOCs from sampling opera-
tions can be controlled by using a(n)
sampling system.
a. Method 5
b. Method 21
c. closed purge
d. open valve
2. True or False? Although flanges are the most
numerous source of fugitive VOC emissions
their total mass emission rate is generally very
small.
1. c. closed purge
S. True or False? Cooling towers and wastewater
systems are not generally sources of fugitive VOC
emissions, since any VOCs present will be dissolved
in the water.
2. True
4. For cooling towers and wastewater systems, the
best control technique is to entering the
system.
S. False
5. Wastewater separators can be controlled by
the oily water separators.
a. covering or enclosing
b. agitating
c. putting mechanical seals on
d. the open burning of
4. limit the hydrocarbons
5. a. covering or enclosing
3-2S
-------
Sources
The text in this lesson was primarily adapted from the following EPA documents.
Draft. Environmental Protection Agency (EPA). August 1981. Control of Volatile Organic
Compound Fugitive Emissions from Synthetic Organic Chemical, Polymer and Resin
Manufacturing. Control Technology Guideline (CTG).
Draft. Environmental Protection Agency (EPA). April 1981. VOC Fugitive Emissions in
Petroleum Refining Industry—Background Information for Proposed Standards.
Environmental Protection Agency (EPA). July 1980. Assessment of Atmospheric Emissions
from Petroleum Refining: Volume 4. Appendix E: Control Technology Review and
Evaluation. EPA 600/2-80-075 (also Volume 1—Final Report EPA 600/2-80-75a).
Environmental Protection Agency (EPA). December 1980. Organic Chemical Manufac-
turing: Volume 3. Storage, Fugitive and Secondary Sources. EPA 450/3-80-25.
Environmental Protection Agency (EPA). April 1982. Fugitive Emission Sources of
Organic Compounds—Additional Information on Emissions, Emission Reductions and
Costs. EPA 450/3-82-010.
References
Block, H. P. 1977. Improve Safety and Reliability of Pumps and Drivers, Part 4.
Hydrocarbon Processing. 56(4): 181.
Environmental Protection Agency (EPA). March 1980. Tichenor, B. A., Hustvedt, K. C.,
and Weber, R. C. Controlling Petroleum Refinery Fugitive Emissions Via Leak Detection
and Repairs in Proceedings: Symposium on Atmospheric Emissions from Petroleum
Refineries. November 1979. Austin, Texas. EPA 600/9-80-013.
Environmental Protection Agency (EPA). April 1981. Compilation of Air Pollutant Emis-
sion Factors up through and including supplement 12. AP-42.
Hoyle, R. 1978. How to Select and Use Mechanical Packing. Chem. Eng. 85(22): 103.
Isaacs, M. 1971. Pressure-Relief Systems. Chem. Eng. 78(5): 113.
Kayser, D. S. 1972. Rupture Disc Selection. CEP. 68(5):61.
Kem, R. 1977. Pressure Relief Valves for Process Plants. Chem. Eng. 84(5): 187.
Litchfield, D. K. 1971. Controlling Odors and Vapors from API Separators. Oil and Gas
Journal. 69(44):60-62.
Nelson, W. E. 1977. Compressor Seal Fundamentals. Hydrocarbon Processing. 56(12):91.
Nurken, R. F. 1974. Pump Selection for the Chemical Process Industries. Chem. Eng.
3-24
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Pikulik, A. 1978. Manually Operated Valves. Chem. Eng. 85(8):119.
Pikulik, A. 1976. Selecting and Specifying Valves for New Plants. Chem. Eng. 83(19): 168.
Ramsden, J. H. 1978. How to Choose and Install Mechanical Seals. Chem. Eng.
85(22): 102.
Temple ton, H. C. 1971. Valve Installation, Operation and Maintenance. Chem. Eng.
78(2S):141.
3-25
-------
Lesson 4
Control of Fugitive VOC Leaks
from Process Equipment
Lesson Goal and Objectives
Goal
To familiarize you with control techniques to reduce fugitive VOC leaks.
Objectives
Upon completing this lesson, you should be able to:
1. name process equipment that is designated as leakless.
2. describe three types of inspection programs used to detect VOC leaks from process
equipment.
3. list the advantages and disadvantages of the above three inspection programs.
4. describe repair techniques used for leaking valves, pump seals, compressor seals,
pressure relief valves, and flanges.
5. list four factors that determine the effectiveness of an inspection and repair program.
Introduction
A number of different regulatory formats could be used by an agency to control fugitive
VOC emissions from leaking process equipment. The regulatory formats can be classified
as:
1. Equipment Standard
2. Work Practice
3. Standard of Performance or Emission Standard
Prescribing a performance standard for most fugitive VOC emission sources is not feasi-
ble, since measuring emissions (by the bagging technique) from a single source is very dif-
ficult and time consuming. The great number of sources and the fact that they are usually
spread apart over large areas make such a requirement economically impractical. The
only exception to this performance standard regulation would be if the standard is set to
allow "no detectable emissions".
Methods for controlling fugitive VOC emissions from leaking process equipment are
generally based on equipment standards, work practice, or a combination of both. This
lesson is divided into three sections. The first section presents the control devices which
can be used to limit fugitive VOC emissions and describes their uses and limitations. The
4-1
-------
second section covers leak detection and repair methods (work practice) that can be
instituted to reduce fugitive VOC emissions. The third section discusses work practice
regulations.
Control Devices
One approach to controlling fugitive VOC emissions from process equipment is to require
the use of equipment that limits VOC emissions. This section discusses the kinds of equip-
ment that could be applied and their advantages and disadvantages.
Pumps
Three control alternatives to eliminate leaks from pump seals are: using dual mechanical
seals with a pressure indicator on the barrier fluid system, using a sealless pump, or
enclosing the seal area and venting the emissions to a control device.
Dual Mechanical Seals
As discussed in Lesson 3, dual mechanical seals are generally more effective than either
single mechanical seals or packing in preventing leaks from rotating pumps. Any leaks
through the inner seal may be dissolved or suspended in the sealing fluid between the dual
seals. The sealing fluid must be a heavy Liquid or non-VOC liquid, otherwise the sealing
fluid could leak. Emissions of VOCs from the barrier fluid degassing vents can be con-
trolled by a closed-vent system which consists of piping to transport the degassing emis-
sions to a control device (such as a process heater or vapor recovery system). Control effec-
tiveness as high as 100% for a dual mechanical seal and a closed-vent system is possible
depending on the effectiveness of the auxilliary control device and on the frequency of
mechanical seal failure. Also, the barrier fluid pressure can be kept greater than the
operating pressure so that any leaks will be into the process fluid. In these cases, the bar-
rier and process fluids must be compatible.
To assure proper operation of dual mechanical seals with a closed vent degassing
system, a pressure or level indicator can be used on the barrier fluid. This indicator would
reveal any catastrophic failure of the inner or outer seal, or of the barrier fluid system.
The indicator could be monitored in a control room with an alarm to signal failure of the
system. If operated in this manner, dual mechanical seals on pumps can normally be
exempted from leak detection and repair programs.
Some conditions preclude the use of dual mechanical seals. These seals can be used only
on shafts with rotary motion. And, they cannot be used at temperatures above 260 °C
(500 °F).
Sealless Pumps
Sealless pumps, such as the canned-motor and diaphragm pumps, do not have a potential
leak area. Therefore, they achieve 100% control. The main limitation of these pumps is
that they can pump only clean process fluid. Since a small portion of the process fluid is
4-2
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pumped through the bearings to provide lubrication, abrasive solids can cause excessive
bearing wear. Sealless pumps are also limited in some process applications by the flow rate
or pressure at which the pump is required to operate.
As with any other leakless equipment, an initial performance test using Reference
Method 21 can verify that the piece of equipment meets a "no detectable emission" limit.
This initial verification and annual rechecks are performed to ensure compliance.
Compressors
Fugitive emissions from compressors occur at the junction of a moving shaft and a sta-
tionary casing. Emission reductions from compressors may be achieved by improving the
seal at the junction, or by collecting and controlling the emissions from the junction.
Mechanical Contact Seals
Mechanical contact seals for compressors are similar to the mechanical seals described for
pump applications. Existing compressors may have mechanical contact seals equipped
with barrier fluid flush systems. Barrier fluid reservoir degassing vents must be controlled
with closed-vent systems as described for pumps. Sometimes a barrier gas may be used to
form a buffer between the compressed gas and the atmosphere. This system requires a
clean external gas supply that is compatible with the gas being compressed. Contaminated
barrier gas must be disposed of properly. The control efficiency for mechanical contact
seals depends on the efficiency of the control device and the frequency of seal failures.
Closed-vent Systems and Control Devices
Compressors in some services cannot be fitted with mechanical seals. For these cases,
enclosure of the seal area may be a reasonable option. The seal area of a compressor may
be enclosed, and the VOC emissions may be routed to a control device through a closed- ,
vent system. However, flow-inducing devices may be required to transport vapors to the
control device. Although the formation of explosive mixtures or excessive pressure buildup
in the enclosed seal area may prohibit application of this equipment modification to some
existing process units, closed-vent systems have been applied to compressor seal areas in
petroleum refineries. Several control methods could be used to dispose of VOC emissions
collected from compressor seal areas. Incineration, carbon adsorption, and condensation
are three control methods that might typically be applied. Control efficiencies of the three
methods depend on specific operating characteristics and type of VOC.
4-3
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Pressure Relief Devices
Rupture Disks
A rupture disk can be installed upstream of a relief valve in order to prevent fugitive
emissions through the relief-valve seat. Figure 4-1 is a diagram of a rupture-disk and
relief-valve installation. Under normal conditions, the rupture disk seals the system tightly.
But if its set pressure is exceeded, it will break and the relief valve will relieve the
pressure. This procedure may require the use of a larger size relief valve because of
operating codes. Since it's possible that the disk may rupture, the disk/valve combination
may also require appropriate piping changes to prevent disk fragments from lodging in
the valve, which would keep it from being reseated properly. A block valve upstream of
the rupture disk may be required in order to permit in-service replacement of the disk
after rupture. If the disk were not replaced, the first overpressure would result in the relief
valve being the same as an uncontrolled relief valve—and it might actually be worse since
disk fragments may prevent proper reseating of the relief valve. In some plants, installa-
tion of a block valve upstream of a pressure relief device is common practice. In others, it
is forbidden by operating or safety procedures. Tandem pressure relief devices with a
three-way valve can be used to prevent operation without relief protection if block valves
are not allowed.
In rupture-disk/relief-valve combinations, some provision for testing the integrity of the
disk is necessary. Pressure should not be allowed to build up in the pocket between the
disk and the relief valve; otherwise, the disk will not function properly. The pocket must
be connected to a pressure indicator, recorder, or alarm. If the process fluid is not hazar-
dous or toxic, a simple bubbler apparatus can be used to test the integrity of the disk by
connecting the bubbler to the pocket. The control efficiency of the disk/valve combina-
tion is assumed to be 100% for fugitive emissions resulting from improper seating or relief
valve simmering. The control efficiency would be lowered if the disk integrity were not
maintained or if the disk were not replaced after rupture. The disk/valve combination has
no effect on emissions resulting from ovei-pressure relieving. However, the pressure relief
device may be vented to a flare system. This provides control for both overpressure occur-
rences and any leakage that may occur.
4-4
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Spring loaded
relief valve
Piping to
atmosphere or
control unit
Blind flange
From process
Figure 4-1. Rupture-disk and relief-valve installation.
Open-ended Valves or Lines
Blinds, Caps, and Plugs
Blinds, caps, plugs, or a second valve are devices for closing off the ends of valves and
pipes. When installed downstream of an open-ended valve, they prevent leaks that may
occur through the seat of the valve from reaching the atmosphere. Open-ended valves are
used mostly in intermittent service for sampling, venting, or draining. If a blind, cap,
plug, or second valve is used downstream of a valve when it is not in use, VOC emissions
can be reduced. If a second valve is used in conjunction with the first valve, the upstream
valve should always be closed before the downstream valve is closed. This operational
requirement is necessary to prevent the trapping of process fluid between the two valves.
4-5
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The control efficiency of these devices is assumed to be 100%. The actual control effi-
ciency will depend on how frequently the cap or plug is removed. The installation of a
blind, cap, or plug limits, but does not prevent, the leakage that may occur through the
valve-stem seal.
Review Exercise
1. The
and
are two types of
sealless pumps, which, because of their design,
eliminate areas where leaks can occur.
2. The degassing vents from the barrier fluid on a dual
mechanical seal should be
a. vented to the atmosphere.
b. equipped with packed seals.
c. connected to a control system.
d. bled periodically.
1. canned-motor
diaphragm
Which of the following will not prevent emissions
from an open-ended valve seat?
a. packing
b. cap
c. plug
d. second valve
2. c. connected to a control
system.
4. True or False? Under normal operating conditions,
rupture disks totally prevent the release of any VOC
emissions.
3. a. packing
Of the following, which would be the most effective
control equipment for a pump?
a. single packed seal with pressure indicator for
barrier fluid system
b. dual packed seal with pressure indicator for bar-
rier fluid system
c. single mechanical seal with pressure indicator for
barrier fluid system
d. dual mechanical seal with pressure indicator for
barrier fluid system
4. True
5. d. dual mechanical seal with
pressure indicator for barrier
fluid system
4-6
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6. True or False? Emissions from compressor seals can
sometimes be controlled by enclosing the seal area
and venting the emissions to a control device.
7. Mechanical seals can be used only on shafts that
have a(n) motion
6. True
8. True or False? Compressors are essentially pumps
used in gas service; therefore, methods to control
leaks are similar for both.
7. rotary
9. VOC emissions from open-ended valves can be
8. True
reduced by installing a
a. blind.
b. cap.
c. second valve.
d. all of the above
9. d. all of the above
Leak Detection and Repair Techniques
Leak Detection Techniques
Fugitive VOC emissions can be reduced by applying a leak detection and repair program
in which fugitive sources are located and repaired at regular time intervals. Leak detec-
tion can be accomplished by three monitoring techniques: an individual component
survey, a unit area survey, and fixed point monitoring. Only the individual component
survey (using a portable VOC detector) has proven effective in locating all significant
equipment leaks.
Individual Component Survey
In an individual component survey, each potential fugitive emission source is checked for
leakage. The most predominant and effective method t>f surveying individual components
is to use a portable VOC detection device that measures the concentrations at the surface
where leakage can occur. This is also commonly referred to as screening. Two additional
individual component survey methods are: using the visual, auditory, or olfactory senses;
and spraying each component with a soap solution and observing bubble formation.
Visual observation is good for locating liquid leaks, especially pump seal failures. For
example, observation of liquid leaking along the shaft indicates an outer seal failure.
However, observation of a visible leak does not necessarily indicate VOC emissions, since
4-7
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the leak may be composed of non-VOC compounds or nonvolatile organ!cs. High pressure
leaks may be detected by hearing escaping vapors. Leaks of odorous material may be
detected by smelling the odor. However, in many instances, even large VOC leaks are not
detected by these methods. These methods used by themselves are not adequate to deter-
mine compliance, but can indicate which areas should be surveyed with a portable VOC
detection device.
Spraying soap solution on equipment components is another individual survey method.
If the soap solution forms bubbles or is blown away, a leak from the component is
indicated. A disadvantage of this method is that it does not distinguish leaks of non-VOC
compounds from VOC leaks. Consequently, air or steam leaks would produce the same
observed effect as VOC leaks. This method is only semiquantitative since it requires that
the observer subjectively determine the rate of leakage based on the behavior of the soap
bubbles. This method is limited to cool sources, since temperatures above 100°C would
cause the water in the soap solution to boil away. To help screen in this temperature
range, glycol can be added to the soap solution. This method is also not suited for moving
shafts on pumps or compressors, since the motion of the shaft may interfere with the
motion of the bubbles caused by a leak. This method can be used in combination with a
portable hydrocarbon detector. Where appropriate, the soap solution can be used for an
initial screening to limit the number of times the instrument will need to be used. The
soap solution will quickly distinguish nonleaks from very large leaks. Leaking sources can
then be screened with the detector.
Portable hydrocarbon detection instruments are the best instruments to identify leaks of
VOCs from equipment components. This instrument is used to sample and analyze the air
close to the potential leak surface by traversing the sampling probe tip over the entire area
where leaks may occur. This sampling traverse is referred to as monitoring or screening.
The hydrocarbon concentration of the sampled air is displayed on the instrument meter.
The performance criteria for monitoring instruments are discussed in Lesson 5. For an
individual component, an increased meter reading indicates that an emission or leak is
present. Data from petroleum refineries have been used to develop relationships between
the monitoring concentration and mass emission rates for several types of sources.
However, these correlations are valid only when applied to the average of a large number
of sources. The relationship for individual sources between the screening value and the
leak rate varies widely. The hydrocarbon concentration that indicates that a component
needs maintenance must be chosen. Components which have indicated concentrations
higher than this action level are marked for repair. Data from petroleum refineries
indicate that large variations in mass emission rates may occur over short time periods for
an individual component. More frequent monitoring intervals tend to reduce the chance
of missing large leaks because of their variable leak rates.
Area Survey
A unit area or walk-through survey entails measuring the ambient VOC concentration
within a distance of one meter of all equipment located on the ground or at other accessi-
ble levels within a processing area. These measurements are performed with a portable
VOC detection instrument that uses a strip chart recorder.
4-8
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The instrument operator walks a predetermined path to assure total available coverage
of a unit on both the upwind and downwind sides of the equipment, noting on the chart
record the location in a unit where any elevated VOC concentrations are detected. If an
elevated VOC concentration is recorded, the components in that area can be screened
individually to locate the specific leaking equipment.
It is estimated that 50% of all significant leaks in a unit are detected by the walk-
through survey, provided only a few pieces of equipment are leaking (so that the VOC
background concentration is sufficiently reduced to allow reliable detection).
The major advantages of the unit area survey are that leaks from sources near the
ground can be located quickly and manpower requirements are lower than those for the
individual component survey. Some of the shortcomings of this method are:
1. VOC emissions from adjacent units can cause false leak indications;
2. high or intermittent winds (local meteorological conditions) can increase dispersion
of VOC, causing leaks to be undetected;
3. elevated equipment leaks are not detected; and
4. additional effort is necessary to locate the specific leaking equipment (i.e., individual
checks in areas where high concentrations are found).
Fixed-point Monitors
This method consists of placing several automatic hydrocarbon sampling and analysis
instruments at various locations in the process unit. The instruments may sample the
ambient air intermittently or continuously. Elevated hydrocarbon concentrations indicate
a leaking component. As in the walk-through method, an individual component survey is
required to identify the specific leaking component in the area. For the fixed-point
monitoring method, the portable hydrocarbon detector is also required. Leaks from adja-
cent units and meteorological conditions may affect the results obtained. The efficiency of
this method is not well established, but it has been estimated that 33% of the number of i
leaks identified by a complete individual component survey could be located by fixed-
point monitors. These units operate continously. Therefore, they can locate leaks more
quickly than individual or unit area surveys. Fixed-point monitors are more expensive
than individual source monitors; multiple units may be required; and the portable instru-
ment is also required to locate the specific leaking component. Calibration and
maintenance costs may be higher than for individual or area surveys. Fixed-point monitors
have been used to detect emissions of hazardous or toxic substances (such as vinyl
chloride) as well as potentially explosive conditions. Fixed-point monitors have an advan-
tage in these cases, since a particular compound can be selected as the sampling criterion.
In the past, monitoring of this type has been done to determine worker exposure to cer-
tain chemicals; not necessarily to limit fugitive emissions of VOCs.
4-9
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Review Exercise
1. Using a portable VOC detection device to measure
the VOC concentration at the surface of a com-
ponent is commonly referred to as
2. Visual observation may be an effective technique
for locating liquid leaks from .
1. screening
3. True or False? Spraying a soap solution on equip-
ment components is the easiest and most effective
technique for determining if a component is
leaking.
2. pump seals
4. In using a portable hydrocarbon detector, the VOC
concentration that indicates that a component needs
maintenance is referred to as the
3. False
5. True or False? Walk-through surveys have an
advantage over surveying individual components in
that the walk-through does not require a portable
VOC detector.
4. action level
6. The most effective method for detecting leaking
components is
a. an individual component survey using a portable
VOC detector.
b. the area survey using a portable VOC detector.
c. fixed-point monitoring.
d. visual inspection.
5. False
7. Spraying soap solution to screen for leaking sources
should be done only on
a. valves.
b. flanges.
c. cool sources.
d. hot sources.
6. a. an individual component
survey using a portable VOC
detector.
7. c. cool sources.
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Repair Techniques
When leaks are located by the monitoring techniques described in this lesson, the leaking
component must be repaired or replaced. Many components can be serviced on-line,
meaning without interrupting the process. However, a leak that cannot be eliminated by
on-line servicing requires that the component be isolated from the process for either repair
or replacement. Isolating the component in many instances requires a complete or partial
shutdown of the process.
A leaking component may be repaired by either directed or undirected maintenance.
Directed maintenance is performed while simultaneously monitoring the leaking com-
ponent with a portable VOC detection device to assess the effectiveness of the repair
effort. Undirected maintenance refers to repairs performed on leaking components
without monitoring the component while it is being repaired.
The following descriptions of repair methods include only those features of each fugitive
emission source (pump, valve, etc.) which need to be considered in assessing the
applicability and effectiveness of each method. They are not intended to be complete
repair procedures.
Pumps
Many process units have spare pumps which can be used while repairing the faulty pump.
The unit can be isolated without major process disruption while the leaking pump is being
repaired. Leaks from packed seals may be reduced by tightening the packing gland.
However, at some point, the packing may deteriorate so much that further tightening
would have no effect, or would possibly even increase fugitive emissions from the seal. If .
such is the case, the packing would be replaced with the pump out of service. When
mechanical seals are used, the pump must be dismantled so that the leaking seal can be
repaired or replaced. Dismantling a pump may result in spills of some process fluid,
causing VOC emissions. These temporary emissions could be greater than the continued
leak from the seal. Therefore, the pump should be flushed of as much VOCs as possible
before opening it to replace the seal.
Compressors
Leaks from packed seals may be reduced by the same repair procedure that was described
for pumps. Leaks from other types of seals require that the compressor be out of service
for repair. Since extra compressors are not usually kept on-site, repair or replacement of
the seal would require a shutdown of the process. If the leak is small, temporary emissions
resulting from a shutdown could be greater than if the seal were allowed to leak until the
next scheduled shutdown and then repaired.
Pressure Relief Devices
In general, leaking relief valves must be removed for repair. However, if a relief valve has
only reseated improperly, manually releasing it may improve its seat. If this is not effec-
tive, the valve may need repair or replacement. In order to remove the relief valve without
shutting down the process, a block valve is installed upstream of the relief valve. (In some
chemical plants, installation of a block valve upstream of a pressure relief device may be a
common practice. In other companies, this practice may be forbidden by the operating or
4-11
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safety procedures of that company, even though allowed by ASME codes.) A spare relief
valve should be attached while the faulty valve is repaired and tested. Even though a relief
valve has just been repaired or replaced, it is still possible that the next over-pressure relief
will result in another leak.
Valves
Most valves have a packing gland that can be tightened while the valve is in service. This
procedure should decrease the emissions from the valve. In some cases, however, the emis-
sion rate may actually increase if the packing is old and brittle or if the packing gland has
been overtightened. Plug-type valves may also be repaired while in service. They can be
lubricated with grease to reduce emissions around the plug.
Some valves cannot be repaired while in service and must be isolated from the process
and removed for repair or replacement. In some situations, isolating a valve may be
relatively easy; for instance, if a manual by-pass loop is available, or if the process opera-
tion can be temporarily changed. However, in most cases, isolation of a valve can be
achieved only by a process shutdown—a major operation. Also, shutting down a process to
isolate a leak may result in more emissions than if the valve were allowed to leak until the
next scheduled shutdown and then repaired at that time.
Depending on site-specific factors, it may be possible to repair process valves by
injecting a sealing fluid into the source. Injection of sealing fluid has been successfully
used to repair leaks from certain valves in petroleum refineries in California.
Open-ended valves allow fugitive emissions to escape through the valve seat. Open-
ended valves include drain, purge, sample, and vent valves. Fugitive emissions from open-
ended valves can be controlled by installing a cap, plug, flange, or second valve to the
open end of the valve. In the case of a second valve, the upstream valve should always be
closed after using the valves. Each time the cap, plug, flange, or second valve is opened,
any VOC which has leaked through the first valve's seat will be released. These emissions
have not been quantified. Control efficiency will depend on the frequency of cap or plug
removal. Caps, plugs, etc. for open-ended valves do not affect emissions which may occur
during valve use. These emissions may be caused by line purging for sampling, draining,
or venting through the open-ended valve.
Flanges
Flange leaks can occasionally be sealed effectively by simply tightening the flange bolts.
For a flange leak that requires off-line gasket seal replacement, a total or partial shut-
down of the unit would probably be required because most flanges cannot be isolated. For
many of these cases, temporary flange repair methods can be used. Unless a leak is major
and cannot be temporarily corrected, the emissions resulting from shutting down the unit
would probably be larger than the continuous emissions that would result from not
shutting down the unit until time for a shutdown for other reasons. Flange leak incidences
are very low and many can be corrected by on-line maintenance.
4-12
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Review Exercise
1. True or False? A leaking mechanical seal requires
that the pump be dismantled before it can be
repaired.
2. Generally, most valves can be repaired on-line by
tightening the .
1. True
3. True or False? Repairing compressor seal leaks is
usually no problem, since most plants have many
spare compressors.
2. packing gland
4. True or False? In spite of the large number of
flanges present, total plant emissions from flanges
are generally very small since most flanges have very
low leak rates.
3. False
5.
maintenance refers to maintenance
4. True
performed while simultaneously monitoring the
leaking component to assess the effectiveness of the
repair effort.
6. If two valves are used, the
valve
5. a. Directed
must always be closed first to prevent trapping fluid
between the two valves.
a. upstream
b. downstream
7. Leaks from a seal on a pump may be
reduced by tightening the gland.
6. a. upstream
7. packed
packing
Structure of Regulations
for Leak Detection and Repair
As described in Lesson 2, there are seven industries that currently have or anticipate stan-
dards to regulate fugitive emissions of VOCs. In developing fugitive VOC emission stan-
dards, each industry was studied separately and a unique set of standards proposed for
4-13
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that industry. Many of the regulations are very similar. The following factors were
addressed for each industry since they determine the effectiveness of a leak detection and
repair program:
• action level (definition of a leak)
• applicability (process equipment to be regulated)
• inspection interval (monitoring frequency)
• interval between detection and repair.
The following is a general discussion of how the above factors were used to develop
fugitive VOC regulations. No attempt is made to detail all the requirements for each of
the industries.
Action Level
The action level is the VOC concentration, observed during monitoring, that defines a
leaking component that requires repair. A leak definition can be based on either a con-
centration value or a "no detectable emission" standard. The "no detectable emission"
standard is applied to sources designed to operate in a leakless manner, such as pressure-
relief devices with rupture disks or sealless pumps.
The concentration-based value most often used to define a leak is a concentration equal
to or greater than 10,000 ppmv. This concentration value is based on the ability to locate
leaks in this concentration range and then repair the leak (bring the concentration below
10,000 ppmv). The "no detectable emission" standard is not an absolute zero reading. A
violation of the "no detectable emission" limit is defined in Reference Method 21 as "a
concentration greater than five percent of the concentration-based leak definition". For
example, based on the 10,000 ppmv definition of a leak, a concentration greater than 500
ppmv would be in violation of the "no detectable emission" standard.
Applicability and Inspection Interval
Fugitive emission regulations are generally applicable to specific process components
(pumps, compressors, valves, sampling connections, pressure relief devices, and open-
ended lines) that are in VOC service. In VOC service includes any fugitive emission source
that contains or contacts a fluid composed of equal to or greater than 10% VOC by
weight. For the benzene fugitive emission regulation, in benzene service includes any
source that contains or contacts a fluid equal to or greater than 10% benzene by weight.
VOC service can further be divided into light liquid or heavy liquid service. Light
liquid VOC service is defined as one or more of the stream components having a vapor
pressure greater than 0.3 kPa (0.04 psia) at 20°C (68°F). All VOC sources with a stream
component vapor pressure equal to or leas than O.S kPa at 20 °C are in heavy liquid
service. The NSPS for "Refinery Leaks" defines heavy liquid as kerosene or a heavier liquid.
The inspection interval or length of time between monitoring is based on the leak rate
and leak frequency of a specific process component and on service conditions. Different
intervals are often specified for different process components. For example, the Draft NSPS
for Petroleum Refineries proposes that most valves in gas or light liquid service, and pumps
in light liquid service, be monitored monthly. However, if a diaphragm or bellows valve is
used, the valve needs only annual monitoring to demonstrate "no detectable emissions".
4-14
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It should be noted that certain control equipment can be substituted for periodic leak
detection and repair procedures. From the above example, if the pump in light liquid ser-
vice was equipped with dual mechanical seals and a pressure indicator on the barrier fluid
system, then that pump could be exempted from the monthly inspection requirement.
In addition, since valves constitute a large percentage of the components to be
monitored (about 90%), alternatives to a periodic inspection cycle have been used to
reduce cost. If the owner/operator can prove that the valves achieve a good performance
level then one or more of the next inspection cycles may be skipped. A good performance
level is based on having a low percentage (usually 2%) of valves that are found to leak.
Allowable Interval before Repair
The allowable time before repair reflects a balance between eliminating a source of VOC
emissions and allowing the plant operator sufficient time to obtain necessary repair parts
and maintain some degree of flexibility in overall plant maintenance scheduling. The
allowable interval before repair is usually specified as 15 days unless a process shutdown is
required. In most cases, the plant operator is required to document when the repairs are
first attempted, reasons for any delay in repair (more than 15 days), and when the leaking
component was successfully repaired.
Review Exercise
The VOC concentration, observed during moni-
toring, that defines a leaking component that
requires repair is referred to as the
a. screen.
b. action level.
c. concentration.
d. effort level.
2. True or False? "No detectable emission" is defined
in Reference Method 21 as a concentration equal to
zero.
1. b. action level.
3. All process components must be monitored
a. weekly.
b. monthly.
c. annually.
d. at varying times, depending upon specific
regulations.
2. False
3. d. at varying times,
depending on specific
regulations.
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4. In VOC service is defined as any source that
contains or contacts a fluid composed of
or more VOCs by weight.
a. 10%
b. 1%
c. 95%
d. 0.1%
5. True or False? All components that are found to
leak must be repaired within 1 hour.
4. 10%
6. A
VOC service is defined as one or
more of the stream components having a vapor
pressure greater than 0.3 kPa (0.04 psia) at
20 °C (68°F).
a. light liquid
b. heavy liquid
c. mixed liquid
5. Fabe. The component must
be repaired as soon as
possible, taking into con-
sideration plant maintenance
schedules.
6. a. light liquid
Sources
The text in this lesson was primarily adapted from the following EPA documents.
Draft. Environmental Protection Agency (EPA). August 1981. Control of Volatile Organic
Compound Fugitive Emissions from Synthetic Organic Chemical, Polymer and Resin
Manufacturing. Control Technology Guideline (CTG).
Draft. Environmental Protection Agency (EPA). April 1981. VOC Fugitive Emissions in
Petroleum Refining Industry—Background Information for Proposed Standards.
Environmental Protection Agency (EPA), July 1980. Assessment of Atmospheric Emissions
from Petroleum Refining: Volume 4. Appendix E: Control Technology Review and
Evaluation. EPA 600/2-80-075D.
Environmental Protection Agency (EPA). December 1980. Organic Chemical Manufac-
turing: Volume 3. Storage, Fugitive and Secondary Sources. EPA 450/3-80-25.
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Lesson 5
Portable VOC Detection Devices
Lesson Goal and Objectives
Goal
To familiarize you with three portable VOC detection devices.
Objectives
Upon completing this lesson, you should be able to:
1. describe the operating principles of three portable VOC detection devices.
2. determine if a portable VOC detector meets the appropriate performance criteria
and equipment specifications using EPA Reference Method 21.
S. recognize the appropriate safety procedures.
Introduction
A number of portable VOC detection devices are capable of measuring leaks from process
equipment. These devices operate on a variety of principles, the three most common being
ionization, infrared absorption, and combustion. Any analyzer can be used, providing that
it meets the specifications and performance criteria contained in EPA Reference Method 21.
This lesson is divided into three sections. The first section is a brief description of the
operating principles and some of the limitations of portable VOC detection devices. The
second section covers the performance criteria required by Reference Method 21. The last
section is a brief discussion of safety considerations. A glossary provided at the end of the
lesson lists some useful terms used to describe the operation and the capabilities of
monitors. Appendix C is a table listing the manufacturers most likely to offer portable
VOC detectors. This table also gives the weight, cost, and operating range of these
devices.
Operating Principles
Ionization
Ionization refers to the act of forming charged atoms (ions) from a neutral compound.
Ionization detectors operate by supplying energy to the sample to ionize it and then
measuring the charge (number of ions) produced. Two methods of ionization currently in
use are flame and photometric.
5-1
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Flame lonization Detector (FID)
In a flame ionization detector (FID), the sample is injected into a detection chamber
where it is exposed to a hydrogen flame. The flame is surrounded by negative collecting
electrodes. When most organic vapors burn, they form positively-charged carbon ions as
intermediate products of combustion. As these positively charged ions are collected, a
calibrated output current is read on a panel meter or recorder (see Figure 5-1).
Hydrogen gas
cylinder
Gas
chromatograph
column
(optional)
Strip chart
recorder
(optional)
Hand held
readout meter
Sample inlet
Sample pump
Figure 5-1. Organic vapor detector using flame ionization detector (FID).
Pure hydrogen burning in air (O2 and N2) produces very little ionization, so background
effects are minimal. Although carbon monoxide and carbon dioxide do not produce
interferences, FIDs show a very low sensitivity to water vapor. Additionally, if water con-
denses in the sample tube, it may block the tube and give erratic readings. As with most
gas samplers, a filter is used to remove any paniculate matter which may be present.
A standard FID usually measures the total carbon content of the organic vapor sam-
pled. The FID analyzers are calibrated using a calibration gas (such as methane or hex-
ane) and the output is read in parts per million by volume (ppmv) of carbon measured as
methane or hexane. With special options, the FID is capable of measuring total gaseous
nonmethane organics (TGNMO) or individual organic components. TGNMO can be
measured by obtaining a reading of the total carbon content in the sample. Then, a car-
bon filter that will absorb all the organics, except methane, is placed on the detector.
Then a second reading is obtained. By subtracting the second value (methane) from the
first (total carbon), the TGNMO is obtained. Concentrations of individual organic com-
pounds in a mixture can be measured by the addition of a gas chromatograph.
5-2
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Certain organic compounds that contain nitrogen, oxygen, or halogen atoms give a
reduced response. In addition, some organics may not give any response at all. Also, FIDs
manufactured by different companies may respond differently to the same chemical com-
pound. Reference Method 21 requires that a response factor be determined for each com-
pound that is to be measured. These response factors are discussed later. Presently, FIDs
are one of the most accepted and widely used detectors for measuring organic leaks from
process equipment.
Photo-ionization Detector
Photo-ionization uses ultraviolet light (instead of a flame) to ionize the organic vapors.
The detector consists of an argon-filled, ultraviolet (UV) light source that emits photons.
A chamber adjacent to this UV light source contains a pair of electrodes. When a positive
potential is applied to one electrode, the field created drives any ions that are formed to
the collector (negative) electrode. Again, the output current (which is proportional to ion
concentration) is read on a meter or recorder.
Presently, only two portable photo-ionization VOC detectors are being marketed. As
with FIDs, detector response varies with the functional group in the organic compounds.
Photo-ionization detectors have been used to detect leaks in the synthetic organic
chemicals industry, especially for certain compounds, (for example, formaldehyde) that
will not give a response on an FID or on a combustible detector.
Nondispersive Infrared Detector
Nondispersive infrared (NDIR) spectrometry is a technique based upon the broadband
light absorption characteristics of certain gases. Infrared radiation is typically directed
through two separate absorption cells—a reference cell and a sample cell. The sealed
reference cell is filled with nonabsorbing gas, such as nitrogen or argon. The sample cell
is physically identical to the reference cell and receives a continuous stream of the gas
being analyzed. When a specific hydrocarbon is present, the IR absorption is proportional
to the molecular concentration of that gas. The detector consists of a double chamber
separated by an impermeable diaphragm. Radiant energy passing through the two absorp-
tion cells heats the two portions of the detector chamber differentially. The pressure dif-
ference causes the diaphragm between the cells to distend and to vary the capacitance.
The variation in capacitance is proportional to the concentration of the component of gas
present and is measured electronically.
The NDIR instruments are usually subject to interference, because other gases (e.g.,
H2O and CO2) absorb light at the wavelength of the gas of interest. Efforts to eliminate
the interferences by use of reference cells or optical filters are only partially successful. For
hydrocarbon monitoring, the detector is filled with one of several different hydrocarbons,
such as hexane or heptane, which may be different from the hydrocarbons contained in
the sample; this causes a disproportionate response. Therefore, these detectors are gen-
erally used only for the detection and measurement of single components.
For these cases the wavelength at which a certain compound absorbs infrared radiation
is predetermined, and the device is preset (by the use of optical filters) for that specific
wavelength. If set to a wavelength of S.4 micrometers, infrared devices can be used to
5-S
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detect and measure petroleum fractions, including gasoline and naphtha, which are
known to be mixtures of aliphatic (saturated and unsaturated) and aromatic
hydrocarbons.
Combustion Analyzers
Combustion analyzers are designed using one of two principles:
1. by measuring the thermal conducmity of a gas.
2. by measuring the heat produced by combusting the gas.
By far, the most common method used in portable VOC detection devices is measuring
the heat of combustion. These devices are referred to as hot wire detectors or catalytic
oxidizers.
One hot wire detector uses a combustion cell composed of two resistance elements. One
element is a catalytic-coated filament, the other is uncoated. The combustible gas sample
is catalytically oxidized by the coated resistance filament. The resulting heat release
changes the filament's resistance. This resistance is then compared, to a reference element
as shown in Figure 5-2. The resistance value of the reference element is unaltered by the
oxidation of combustible gas. The resulting imbalance is easily measured and related to
VOC concentration.
Sample inlet
Catalytic-coated
filament
Gas outlet
Reference cell
Gas outlet
To Wheatstone
bridge
Figure 5-2. Hot wire detector.
5-4
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Combustion analyzers, like most other detectors, are nonspecific for mixtures of gases.
Mixtures must be separated (usually by a chromatographic column) to identify an
individual concentration. Although not required by the regulations, identifying an
individual concentration may be desirable. In addition, combustion analyzers will give a
reduced response to or not detect any gases that are not readily combusted (for example,
formaldehyde and carbon tetrachloride). Because of their ease of operation and
applicability to most sources, combustion analyzers are widely used in both refineries and
SOCMI plants to detect leaks.
Review Exercise
1. FID refers to a
2. True or False? An FID uses a hydrogen flame to
combust the sample gas and produce carbon ions
that can be easily measured.
1. flame ionization detector
3. True or False? Two types of portable ionization
detectors used to detect leaking process equipment
are photo-ionization detectors and infrared
detectors.
2. True
4. What does the hot wire combustion analyzer
measure that is easily related to the concentration of
the gas sample?
a. vapor pressure of the gas sample
b. partial pressure of the gas sample
c. heat produced by combustion of the gas sample
d. latent heat of the gas sample
3. False
5. Any portable detection device that meets the
specifications and performance criteria of
can be used to monitor leaks from
process equipment.
4. c. heat produced by com-
bustion of the gas sample
5. Federal Reference Method 21
5-5
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Performance Criteria and Evaluation
Procedures for Portable VOC Detectors
As previously stated, any portable VOC detector may be used as long as it meets the per-
formance criteria specified in Reference Method 21. Reference Method 21 is reproduced
in Appendix A. A discussion of the performance criteria and detector evaluation pro-
cedure is presented below and summarized in Table 5-1.
Table 5-1. Performance criteria for portable VOC detectors.
Criteria
Response factor
Response time
Calibration
precision
Requirement
Must be < 10
Must be £ SO seconds
Must be <; 10% of
calibration gas value
Time interval
One time, before detector
is put in service
One time, before detector
is put in service. If modi-
fication to sample pumping
or flow configuration is made,
a new test is required.
Before detector is put in
service and at 3-month
intervals or next use, which-
ever is later.
In addition to the performance criteria, Reference Method 21 also requires that the
analyzer meet the following specification!*:
• the VOC detector shall respond to those organic compounds processed at the plant
(determined by the response factor).
• the analyzer shall be capable of measuring the leak definition specified in the regula-
tion (i.e., 10,000 ppmv or "no detectable limit").
• the scale of the analyzer shall be readable to ± 5 % of the specified leak definition
concentration.
• the analyzer shall be equipped with a pump so that a continuous sample is provided
at a nominal flow rate of between 0.5 and 3 liters per minute.
• the analyzer shall be intrinsically safe for operation in explosive atmospheres as
defined by the applicable standards.
Also, criteria for the calibration gases to be used are specified. Two calibration gases
are required for both monitoring and analyzer performance evaluation. One is a zero gas
which is air with less than 10 ppmv VOC. The other calibration gas uses a reference com-
pound/air mixture. This calibration gas is also referred to as the reference gas. The con-
centration of the reference gas is approximately equal to the leak definition. The leak
definition and the reference compound are both specified in the applicable regulations.
Calibration may be performed using a compound other than the reference compound if a
conversion factor is determined for the alternate compound. The resulting meter readings
during source surveys can be converted to reference compound results. Often, manufac-
turers list conversion factors for other gases in their operator's manuals. Because of
nonlinear responses, however, care must be taken to use the conversion factor at the
action level.
5-6
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Response Factor
The sensitivity of an analyzer varies, depending on the composition of the sample and
concentration detected. The response factor (RF) helps to quantify the sensitivity for each
compound. The response factor is defined by:
_ , Actual concentration of compound
Response factor = *-
Observed concentration from detector
A response factor must be determined for each compound that is to be measured, either
by testing or from reference sources. The analyzer response factor for individual
compounds to be measured must be less than 10.0. The response factor tests are required
before placing the analyzer in service, but do not have to be repeated at subsequent
intervals.
Response factors can be determined by the following method. First the analyzer is
calibrated using the reference gas. Then, for each organic species that is to be measured,
a known standard in air is obtained or prepared. The standard should be at a concentra-
tion of approximately 80% of the leak definition unless limited by volatility or explosivity.
In these cases, a standard at either 90% of the saturation concentration or 70% of the
lower explosive limit (LEL) is prepared. This mixture is then injected into the analyzer
and the observed meter reading is recorded. The analyzer is then zeroed by injecting zero
air until a stable reading is obtained. The procedure is repeated by alternating between
the mixture and zero air until a total of three measurements is obtained. A response fac-
tor is calculated for each repetition and then averaged over the three runs.
Alternately, if response factors have been published for the compounds of interest for
the type of detector, the response factor determination is not required, and existing results
may be referenced. Results of a study developing response factors for FID (Foxboro
OVA-108 and OVA-128) and catalytic oxidation (J. W. Bacharach TLV Sniffer) analyzers
are presented in Appendix B. The values are only for pure organic chemicals.
It is important to note that these response factors are used only as a guide to determine
a particular analyzer's appropriateness for detecting a given compound. For example,
from the data presented in Appendix B, it can be readily seen that in screening for leaks
from a source containing cumene, an FID can be used (RF= 1.87); while the catalytic
oxidation detector cannot (RF has no value). Similarly, from the same data, neither of
these devices would be capable of detecting leaks from a source containing carbon
tetrachloride.
The concept of using response factors as a general guide to analyzer applicability is
especially important when dealing with chemical mixtures. Since many process streams in
industrial plants are composed of a mixture of chemicals, having a simple method to
determine the response factor for a given detector type is important. One EPA study has
concluded that analyzer response factors for a mixture fall between the responses expected
for the pure components. Therefore, if desired, an interpolated or weighted average can
be used to predict the response for mixtures based on known responses for individual
chemicals. For further information see EPA 600/2-81-110, Response of Portable VOC
Analyzers to Chemical Mixtures.
5-7
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Response Time
The response time of an analyzer is defined as the time interval from a step change in
VOC concentration at the input of a sampling system to the time at which 90% of the
corresponding final value is reached as displayed on the analyzer readout meter. The
response time must be equal to or less than 30 seconds. The response time must be deter-
mined for the analyzer configuration that will be used during testing. The response time
test is required before placing an analyzer in service. If a modification to the sample
pumping system or flow configuration is made that would change the response time, a
new test is required before further use.
The response time of an analyzer is determined by first introducing zero gas into the
sample probe. When the meter has stabilized, the system is quickly switched to the
specified calibration gas. The time, from the switching to when 90% of the final stable
reading is reached, is noted and recorded. This test sequence must be performed three
times. The reported response time is the average of the three tests.
Calibration Precision
Calibration precision is the degree of agreement between measurements of the same
known value. To ensure that the readings obtained are repeatable, a calibration precision
test must be completed before placing the analyzer in service, and at 3-month intervals, or
at the next use, whichever is later. The calibration precision must be equal to or less than
10% of the calibration gas value.
To perform the calibration precision test, a total of three test runs are required.
Measurements are made by first introducing zero gas and adjusting the analyzer to zero.
The specified calibration gas (reference) is then introduced and the meter reading is
recorded. The average algebraic difference between the meter readings and the known
value of the calibration gas is then computed. This average difference is then divided by
the known calibration value and multiplied by 100 to express the resulting calibration
precision as percent.
Safety
Portable instruments to detect fugitive VOC emissions from stationary sources are required
to be used in hazardous locations such as petroleum refineries and bulk gasoline terminals.
The National Electrical Code requires that instruments to be used in hazardous locations
be certified to be explosion proof, intrinsically safe, or purged.
Hazardous locations are divided into three classes: Class I, Class II, and Class III. Each
class is divided into two divisions (Division 1 or 2) according to the probability that a
hazardous atmosphere will be present; and also into seven groups depending upon the
type of hazardous material exposure. Groups A through D are flammable gases or vapors,
and Groups E, F, and G apply to combustible or conducting dusts. Class I, Division 1,
Groups A, B, C, and D locations are those in which hazardous concentrations of
flammable gases or vapors may exist under normal operating conditions. Class I, Division
2, Groups A, B, C, and D locations are those in which hazardous concentrations of flam-
mables may exist only under unlikely conditions of operation.
5-8
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Only five manufacturers presently produce certified portable VOC detection
instruments. Table 5-2 lists these manufacturers, approved instrument model numbers,
and instrument certification categories.
Table 5-2. Portable VOC detection instrument certification.
Manufacturer
Bacharach Instrument Co.,
Santa Clara, California
Foxboro,
Norwalk, Conneticut
HNU Systems, Inc.
Newton Upper Falls,
Massachusetts
Mine Safety Appliances Co. ,
Pittsburgh, Pennsylvania
Survey and Analysis, Inc.,
Northboro, Massachusetts
Model no.
L
TLV Sniffer
OVA-128
OVA-108
PI-101
40
OnMark
Model5
Certification
Intrinsically safe, Class I, Division 1,
Groups C and D
Intrinsically safe, Class I, Division 1,
Groups C and D, and Class I, Division 2,
Groups A and B
Intrinsically safe, Class I, Division 1,
Groups A, B, C, and D
Intrinsically safe, Class I, Division 1,
Groups A, B, C, and D
Intrinsically safe, Class I, Division 2,
Groups A, B. C, and D
Intrinsically safe, Class I, Division 1,
Group D, and Class I, Division 2,
Groups A, B, and C
Intrinsically safe, Class I, Division 1,
Groups A. B, C, and D
In addition to instrument certification, certain operating procedures and safety precau-
tions must be observed when any portable VOC detection device is used. The very first
thing that must be done is to read the operating and service manual very carefully before
using the device in the field. Also, to maintain the intrinsic safety which is built into cer-
tain detectors, it is imperative that the operating and service manual be consulted before
trouble-shooting or servicing.
Flame ionization hydrocarbon detectors are potentially hazardous since they burn
hydrogen in the detector cell. Mixtures of hydrogen and air are flammable over a very
wide range of concentrations. Therefore, additional safety precautions should be taken
when igniting the flame and refilling the hydrogen supply tank. Both these tasks should be
carried out in a safe area to ensure that there are no sources of ignition. As can be seen
from Table 5-2, one FID analyzer, Foxboro's OVA, has been certified intrinsically safe for
use in hazardous atmospheres. Additional safety considerations on field use of these
analyzers are discussed in the next lesson, Inspection Procedures.
5-9
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Review Exercise
1. True or False? Reference Method 21 lists the model
numbers of the EPA-approved portable VOC
detection devices.
2. The
gives a quantitative measure of
1. Fake
an analyzer's sensitivity.
a. response factor
b. precision test
c. lag time
d. reference gas
3. True or False? Response factors can be obtained
only from the manufacturers of the portable
analyzers.
2. a. response factor
4. The reference gas used to calibrate the analyzers
is specified
a. in Reference Method 21.
b. by the manufacturer.
c. in the applicable regulation for each source
category.
d. by the National Bureau of Standards.
3. False
5. True or False? The response time of a specific
analyzer partially depends upon its sample flow
configuration.
4. c. in the applicable
regulation for each source
category.
6. True or False? A calibration precision test is
required to be performed only before placing the
analyzer in service for the first time.
5. True
7. A portable VOC analyzer must be readable to
± of the specified leak definition
concentration.
a. 5%
b. 25%
c. 50%
d. 0.1%
6. False
7. a. 5%
5-10
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8. A portable VOC analyzer must be equipped
with a to provide a continuous sample
flow.
9. True or False? Reference Method 21 requires
that the portable VOC analyzer be intrinsically safe
for use in an explosive atmosphere.
8. pump
10. Federal Reference Method 21 requires that the
portable VOC detector have a response time equal
to or less than
a. 1 second.
b. SO seconds.
c. 1 minute.
d. 5 minutes.
9. True
10. b. 30 seconds.
Glossary
Accuracy—The difference between the measured value and the true value that has been
established by an accepted reference method procedure. In most cases, a value is quoted
by the manufacturer.
Ambient Temperature Range—The range of ambient temperature over which the
instrument meets stated performance specifications.
Calibration Gas—The VOC compound used to adjust the instrument meter reading to a
known value. The calibration gas is usually the reference compound at a concentration
approximately equal to the leak definition concentration.
Calibration Precision—The degree of agreement between measurements of the same
known value, expressed as the relative percentage of the average difference between the
meter readings and the known concentration.
Fall Time—The time interval between the initial response and a 90% response (unless
otherwise specified) after a step decrease in the inlet concentration. This measurement is
usually, but not necessarily, the same as the rise time.
Interference—Any substance causing a deviation of instrument output from the value
that would result from the presence of only the pollutant of concern.
Lag Time—The time interval from a step change in the input concentration at the
instrument inlet to the first corresponding change in the instrument output.
Lower Detectable Limit—The smallest quantity or concentration of a sample that
causes a response equal to twice the noise level. (Not to be confused with sensitivity, which
is the minimum detectable change).
5-11
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Noise—Spontaneous deviation from a mean output not caused by input concentration
changes (expressed as a percentage of the full scale).
Range—The lower and upper detectable limits. (The lower limit is usually reported as
0.0 ppm. This is somewhat misleading arid should be reported as the true lower detec-
table limit.)
Reference Compound—The VOC species selected as an instrument calibration basis for
specification of the leak definition concentration. (For example: If a leak definition con-
centration is 10,000 ppmv as methane, then any source emission that results in a local
concentration that yields a meter reading of 10,000 on an instrument calibrated with
methane would be classified as a leak. In this example, the leak definition is
10,000 ppmv, and the reference compound is methane.)
Response Factor—The ratio of the known concentration of a VOC compound to the
observed meter reading when measured using an instrument calibrated with the reference
compound specified in the application regulation.
Response Time—The time interval from a step change in the input concentration at the
instrument inlet to a reading of 90% (unless otherwise specified) of the ultimate recorded
output. This measurement is the same as the sum of lag time and rise time.
Sensitivity—The smallest change in inlet concentration which can be detected
distinguishable from instrument noise for outputs at mid-scale and 80% of full scale. The
magnitude of change in inlet concentration required may differ with pollutant concentra-
tion and may also be different for positive and negative displacements.
Span Drift—The change over a stated period of time in instrument output of
unadjusted continuous operation when the input concentration is a stated value other than
zero (expressed as a percentage of the full scale).
Warmup Time—The elapsed time necessary after startup for the instrument to meet
stated performance specifications when the instrument has been shut down for at least
24 hours.
Zero Drift—The change over a stated period of time in instrument output of unadjusted
continuous operation when the input concentration is zero (expressed as a percentage of
the full scale).
Sources
The text in this lesson was adapted primarily from the following documents:
Environmental Protection Agency (EPA). March 1980. Summary of Available Portable
VOC Detection Instruments. EPA 340/1-30-010.
Environmental Protection Agency (EPA). January 5, 1981. Proposed Reference Method
21, Determination of Volatile Organic Compound Leaks. EPA-46, Federal Register No. 2.
5-12
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References
Bacharach Instruments. October 1981. Instruction Manual TLV Sniffer. Pittsburgh, PA.
Foxboro, Instruction and Service Manual for Model OVA-108. S. Norwalk, CT.
Environmental Protection Agency (EPA). September 1981. Response Factors of VOC
Analyzers at a Meter Reading of 10,000 ppmvfor Selected Organic Compounds. EPA
600/2-81-051.
Environmental Protection Agency (EPA). September 1981. Response of Portable VOC
Analyzers to Chemical Mixtures. EPA 600/2-81-110.
5-13
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Lesson 6
Inspection Procedures
Lesson Goal and Objectives
Goal
To prepare you to inspect process components for VOC leaks.
Objectives
Upon completing this lesson, you should be able to:
1. recognize the preparation and equipment needed to perform inspections.
2. be familiar with the recordkeeping requirements specified in the regulations.
3. distinguish between a source survey based on a concentration or "no detectable
emission" limit.
4. recognize appropriate safety procedures.
Introduction
General inspection procedures for individual process components such as valves and pump
seals are outlined in Reference Method 21. The inspection procedures for the individual
process components are identical for all of the source catagories (SOCMI, refineries, etc.).
This lesson will review these inspection procedures, noting some of the problems that may
occur and the safety precautions to be observed. It is important to note that plant size and
complexity will greatly affect inspection procedures. Therefore, this lesson presents several
inspection approaches rather than one standard procedure.
Pre-inspection Preparation
Research
Since any inspection requires labor and expense, minimizing the inspection time spent in
the plant is important. The inspector should conduct a thorough search of the agency files
on the facility to be inspected. This will help determine the types of process units, the
number of process units, and the compliance history and trends of this facility. The
inspector should be as informed as possible about the operation of these process units and
the potential sources of fugitive VOC emissions. The more the inspector knows, the better
he or she will be able to communicate with plant personnel.
6-1
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The inspector must also review the regulations that are applicable to the facility.
Regulations about sources to be inspected, action level (leak definition), and inspection
interval should be particularly noted. The inspector can then determine the best schedule
for plant visits. Because of the large number of sources, it will generally be impossible to
inspect all of them at a specific facility at one time (see Appendix D). Most regulations
are developed on the basis of a process unit being the affected facility. For example, in a
refinery, alkylation and isomerization are both process units. Before entering the plant,
the inspector should determine the number of process units he or she intends to inspect.
This will enable the inspector to prepare survey log sheets for these process units similar to
those maintained by plant operators. Figure 6-1 is an example of a survey log sheet for
identifying leaking components.
Process uni
Component
Leak detection an
*
Stream composition
Gas
Liquid
Light
Heavy
Tag
number
d repair
Instru
Date
leak
located
survey log
mem operator „
Analyzer
Date
maintenance
performed
Component recheck
after maintenance
Date
Analyzer
reading
(ppmv)
Figure 6-1. Example monitoring survey log sheet.
6-2
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The number of process units that will be inspected is determined by the level of inspec-
tion planned. Generally, the inspections are aimed at maintaining a limited number of
units in continuous compliance with the regulations. Therefore, the inspector will
periodically screen a random sample of process equipment. These process units can be
chosen from plant records or previous inspection reports that indicate any problem areas.
If this information is not available, the inspector may wish to choose process units that
handle gases or light liquids. For example, in a refinery, these process units would be light
ends/gas processing, fluid catalytic cracking, alkylation, and isomerization. The inspection
may also be aimed at obtaining strict compliance for the entire facility. For large plants
(especially refineries), this would require a group of inspectors working for several days.
Notification
The facility management should be contacted before the inspection date unless a surprise
inspection is intended. The facility management should be notified of the intent to inspect
and the purpose of the inspection. A date and time can then be arranged and the facility
management informed to have the appropriate records available at the time of the inspec-
tion. Also, the inspector can find out what safety equipment will be required.
Equipment
Inspecting the facility for equipment leaks requires the inspector to have a portable VOC
detector. As discussed in Lesson 4, other methods may be used to detect leaking com-
ponents; however, this lesson will focus on using a portable VOC detector. In choosing
and operating a portable VOC detection device, the following must be considered:
1. Does the detector respond to the compounds being processed and have a response
factor less than 10? (Lesson 5 and Appendix B)
2. Does the inspector understand how to start up, use, calibrate, shut down, and in the
case of an FID, refuel the detector? The inspector may wish to practice these pro-
cedures in the lab or office.
3. Does the instrument meet all the specifications required by Reference Method 21?
(Lesson 5 and Appendix A)
4. Has the instrument passed calibration precision and response time tests? Has it been
rechecked prior to use? (Lesson 5 and Appendix A)
5. Is the instrument operating properly immediately preceding its use in the field? Has
it been calibrated, battery checked, etc.? This is not a requirement of Reference
Method 21, but helps eliminate delays in the field.
6. Have arrangements been made so that calibration gas (hexane or methane) is at the
inspection site? Also, have arrangements for hydrogen cylinders been made if an FID
is to be used?
In addition to the portable VOC detection device, the inspector must also carry paper
and pencil. An inspection team should consist of at least two persons—one person to
operate the portable VOC detector and the other to take the necessary notes.
6-3
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Review Exercise
The EPA reference method for the determination of
VOC leaks from process components is
a. 5.
b. 2.
c. 25.
d. 21.
2. Most regulations governing VOC leaks consider the
to be the affected facility.
1. d. 21.
a. process unit
b. entire plant
c. component
3. The leak definition is given in
a. Reference Method 21.
b. the appropriate regulation.
2. a. process unit
4. Specifications and performance criteria for portable
VOC detectors are given in
a. Reference Method 21.
b. the appropriate regulation.
3. b. the appropriate
regulation.
Before a plant inspection, the inspector must
review the applicable regulations for the facility
being inspected for
a. sources to be inspected.
b. action level.
c. inspection interval.
d. all of the above
4. a. Reference Method 21.
To perform Reference Method 21, the inspector
is required to use a to locate leaks.
a. portable VOC detector
b. soap bubble solution with glycol
c. transmissometer
d. mechanical seal
5. d. all of the above
6. a. portable VOC detector
6-4
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General Field Procedures
This section covers a number of important aspects involved in the plant visit and inspec-
tion. Because of the number of and different types of source categories, this section will
outline general approaches to conducting an inspection, rather than recommend a stan-
dard procedure.
Inspection of Plant Records
Any facility affected by VOC fugitive emission regulations will be required to keep records
to verify compliance. The specific amount of information required (pertaining to leak
detection and repair) varies depending upon the regulations applicable to that particular
facility. The regulations should be checked to determine the specific recordkeeping
requirements for each facility. Recordkeeping is usually required in three different
categories of the control program: leak monitoring; control equipment; and equipment
capable of meeting a "no detectable emission" limit. In general, the following information
must be kept in the plant log:
1. Leak monitoring
• Instrument and identification number of any source found to be leaking
• Date that the leak was detected and dates of each attempt to repair
• Repair methods applied, expected date of successful repair if it must be delayed
(usually by more than 15 days), and the date of successful repair
• Weatherproof and readily visible tag on leaking source, which will be removed
after repair and remonitoring (usually two inspection cycles)
2. Control equipment (refers to closed-vent systems, combustion devices, dual
mechanical seals with pressure indicators, and vapor recovery systems)
• Schematics, design specifications, and piping and instrumentation diagrams of
these systems
• Dates and description of any changes to these systems
• Dates of any shutdowns or malfunctions
3. Equipment meeting a "no detectable emission" limit
• A listing with identification numbers of equipment designated as meeting the "no
detectable emission" limit
• Dates of verification test for "no detectable emission" limit
• Background level and maximum VOC concentration from source measured at
each verification test.
Records such as the above are examined to determine compliance, but can also be used
as a guide for the inspection to determine the process units to monitor. Two general
approaches can be used: chronic leakers can be checked to ensure proper repair; or leak-
free units may be monitored to verify the plant data.
Individual Source Surveys
Before each use, the portable VOC detector must be calibrated. The detector is assembled
and started according to the manufacturer's instructions. The detector must be allowed to
warm up for the appropriate period of time; for example, five minutes for the Century
6-5
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Systems OVA and ten minutes for the TLV Sniffer. The instrument is then adjusted to
zero. (In some cases, zero may be adjusted up-scale to enable the operator to read any
negative deflections). Calibration gas is then injected into the analyzer and the meter
readout adjusted to the corresponding calibration gas value. If the meter readout cannot
be adjusted to the proper value, a malfunction of the analyzer is indicated and corrective
actions are necessary before using the analyzer.
The definition of what constitutes a leak determines the procedure used in an individual
source survey. Definitions of a leak are given in the regulations for each source category
and are either based on a concentration (e.g., 10,000 ppmv) or stated as "no detectable
emission" limit. The following procedures used to screen process components are taken
directly from Reference Method 21.
Leak Definition Based on Concentration
Place the probe inlet at the surface of the component interface where leakage could
occur. Move the probe along the interface periphery while observing the instrument
readout. If an increased meter reading is observed, slowly sample the interface where
leakage is indicated until the maximum meter reading is obtained. Leave the probe inlet
at this maximum reading location for approximately twice the instrument response time.
If the maximum observed meter reading is greater than the leak definition in the
applicable regulation, record and report the results as specified in the regulation reporting
requirements. Examples of the application of this general technique to specific pieces of
equipment follow (Figures 6-2 and 6-3).
Valves—The most common source of leaks from valves is at the seal between the stem
and housing. Place the probe at the interface where the stem leaves the packing gland.
Sample the stem circumference. Also, place the probe at the interface of the packing-
gland-take-up-flange seat and sample the periphery. In addition, survey valve housings of
multipart assemblies at the surface of all interfaces where leaks could occur.
Flanges and other connections—For welded flanges, place the probe at the outer edge
of the flange-gasket interface and sample the circumference of the flange. Sample other
types of nonpermanent joints (such as threaded connections) with a similar traverse.
Pumps and compressors—Conduct a circumferential traverse at the outer surface of the
pump or compressor shaft and seal interface. If the source is a rotating shaft, position the
probe inlet within 1 cm of the shaft seal interface. If the housing configuration prevents a
complete traverse of the shaft periphery, sample all accessible portions. Sample all other
joints on the pump or compressor housing where leaks could occur.
Pressure relief devices—The configuration of most pressure relief devices prevents
sampling at the sealing seat interface. For those devices equipped with an enclosed exten-
sion, or horn, place the probe inlet at approximately the center of the exhaust area to the
atmosphere.
Process drains—for open drains, place the probe inlet at approximately the center of
the area open to the atmosphere. For covered drains, place the probe at the surface of the
cover interface and conduct a pheripheral traverse.
Open-ended lines or valves—Place the probe inlet at approximately the center of the
opening to the atmosphere.
6-6
-------
Seal system degassing vents and accumulator vents—Place the probe inlet at approx-
imately the center of the opening to the atmosphere.
Access door seals—Place the probe inlet at the surface of the door seal interface and
conduct a peripheral traverse.
Leak Definition Based on "No Detectable Emission"
Determine the background concentration around the source by moving the probe inlet
randomly upwind and downwind at a distance of 1 to 2 meters from the source. If an
interference exists with this determination due to a nearby emission or leak, the local
ambient concentration may be determined at distances closer to the source, but in no case
shall the distance be less than 25 centimeters. Move the probe inlet to the surface of the
source and conduct the same survey described in the preceding section. If an increase
greater than 5% of the leak definition concentration is obtained, record and report the
results as specified by the regulation.
For those cases where the regulation requires installing a specific device, or ducting or
piping specified vents to a control device, the existence of these conditions shall be visually
confirmed. When the regulation also requires that "no detectable emissions" exist, visual
observations and sampling surveys are required. Examples of this technique are as follows:
Pump or compressor seals—If applicable, determine the type of shaft seal. Perform a
survey of the local area ambient VOC concentration and determine if detectable emissions
exist as described above.
Seal system degassing vents, accumulator vessel vents, pressure relief devices—If
applicable, observe whether or not the applicable ducting or piping exists. Also, deter-
mine if any sources exist in the ducting or piping where emissions could occur in front of
the control device. If the required ducting or piping exists, and there are no sources where
the emissions could be vented to the atmosphere in front of the control device, then it is
presumed that "no detectable emissions" are present.
Figure 6-2. Field intpection.
6-7
-------
Figure 6-3. Field inspection.
Common Operating Problems
One of the main problems in monitoring; organic vapors is locating or pinpointing the
leaking source. Organic vapors are dispersed by the wind, sometimes making it difficult to
determine their source. It is important that the probe be moved slowly; the slower the
instrument response time, the slower the probe must be moved. Placing a notebook or
something similar (to block the wind) on the upwind side of the suspected leaking source
may help locate the leak, but is not required by Reference Method 21.
In some cases, it may be difficult to determine whether a meter response is caused by
high ambient air hydrocarbons or by a source leak, particularly when the ambient reading
is highly variable. This problem is commonly experienced in enclosed areas. One method
to determine if the source is leaking is to place the probe at the leak source and then
remove it from the leak source. This operation is repeated at regular intervals. If the
movement of the needle corresponds to the placement and removal of the probe (keeping
in mind the analyzer response time), the source is probably leaking. The screening value is
then determined by subtracting the ambient reading from the measured screening result.
A variety of such situations may be encountered and a judgment on the part of the
operator may be required to obtain a representative reading.
6-8
-------
Occasionally, a source may be encountered which has a highly variable leak rate. In
general the maximum sustained reading or the maximum repeatable reading should be
recorded. Again, a judgment on the part of the operator may be required to obtain a
representative reading.
A further screening difficulty may arise when screening sources contain heavier
hydrocarbon streams, particularly hot sources. When these sources are screened, some of
the vapor tends to condense on the internal surfaces of probe-sample hoses. The response
of the meter is considerably slower for these sources than for lighter hydrocarbons. And,
the meter may require more time to return to zero. When screening heavier hydrocarbons,
the meter should be allowed to stabilize before recording the result. The meter should be
allowed to return to about 20% of the recorded value. Before screening the next source,
sufficient time should be allowed for the meter to stabilize or return to zero. Often the
meter will not return completely to zero and a considerable adjustment may be required.
Under no circumstances should the end of the probe be placed in contact with liquid. If
liquid is drawn through the sample hose, it may damage the analyzer. A liquid trap, con-
nected between the analyzer and the sample probe, can be used. In addition, equipment
components may be covered with a film of grease or dirt. If the probe touches these com-
ponents the grease may plug the probe. The inspector can carry a package of pipe
cleaners to clean out the probe, or he/she can use a Teflon extension, and if it gets
clogged simply cut off the end.
Safety Considerations
Some components might be considered unsafe to monitor because process conditions
include extreme temperatures or pressures. Less frequent monitoring intervals for these
components may be required because of the potential danger that may be presented to
monitoring personnel. For example, some pumps might be monitored at times when
process conditions are such that the pumps are not operating under extreme temperatures
or pressures. When using a portable VOC detector, the following safety practices are
suggested:
1. Do not place a rigid probe in contact with a moving pan such as a rotating pump
shaft. A short, flexible probe extension tip may be used.
2. Do not place the umbilical cord from the detector on a heated surface such as a
pipe, valve, heat exchanger, or furnace.
Some components may be difficult to reach because they are located in elevated areas.
Occasionally these components might be reached by using a ladder or scaffolding.
However, extreme caution should be used in attempting to monitor any component which
requires that the inspector climb higher than two meters above permanent support
surfaces.
Also, it should be mentioned that each plant will have its own safety procedures. These
procedures may involve wearing of protective clothing, restrictions on the use of tools in
certain areas and contacting the safety officer. Since these procedures are different for
each plant it is not the intent of this manual to cover them. However, before inspecting
any facility, the plant safety officer should be contacted.
6-9
-------
Review Exercise
1. True or False? Equipment that meets a "no detec-
table emission" limit never has to be monitored for
leaks.
2. True or False? Leaking equipment must be tagged
with a weatherproof and readily visible marker until
it is repaired and rescreened.
1. Fake
3. Immediately before each use a portable VOC
detector must be
a. tested for calibration precision.
b. tested for response time.
c. used to determine the response factor.
2. True
4. For screening potential leaking components, the
probe is placed
a. at the surface where leakage could occur.
b. 5 cm from where leakage could occur.
c. 10 cm from where leakage could occur.
d. 25 cm from where leakage could occur.
3. a. tested for calibration
precision.
When a leak is found, the probe is moved until
the maximum meter reading is obtained. The probe
is then left at this location for approximately twice
the instrument
a. response factor.
b. response time.
c. precision time.
4. a. at the surface where
leakage could occur.
True or False? For a leak definition based on
"no detectable emissions", the ambient concentra-
tion near the source must be obtained. This is done
by moving the probe upwind and downwind at a
distance of at most 1 to 2 meters or no closer than
25 centimeters from the source.
5. b. response time.
7. True or False? When an inspector notices liquid
on equipment components, he should place the
probe tip in the liquid to determine if it is a VOC.
6. True
7. False
6-10
-------
8.
9.
True or False? Some equipment components might
be considered unsafe to monitor because process
conditions include extreme temperatures or
pressures.
One of the main problems in monitoring organic
vapors is the leaking source.
8. True
9. locating (or pinpointing)
Sources
The text for this lesson was adapted primarily from the following EPA documents.
Environmental Protection Agency (EPA). March 1980. Petroleum Refinery Enforcement
Manual. EPA 340/1-80-008.
Smith, C. D. March 1980. Methodology—Sampling and Analysis of Atmospheric Emis-
sions from Petroleum Refineries in Proceedings: Symposium on Atmospheric Emissions
from Petroleum Refineries (November 1979, Austin, TX). EPA 600/9-80-013.
6-11
-------
Appendix A
Method 21. Determination of Volatile
Organic Compound Leaks
1. Applicability and Principle
1.1 Applicability. This method applies to the determination of volatile organic com-
pound (VOC) leaks from process equipment. These sources include, but are not limited
to, valves, flanges and other connections, pumps and compressors, pressure relief devices,
process drains, open-ended valves, pump and compressor seal system degassing vents,
accumulator vessel vents, agitator seals, and access door seals.
1.2 Principle. A portable instrument is used to detect VOC leaks from individual
sources. The instrument detector type is not specified, but it must meet the specifications
and performance criteria contained in Section 3. A leak definition concentration based on
a reference compound is specified in each applicable regulation. This procedure is
intended to locate and classify leaks only, and is not to be used as a direct measure of
mass emission rates from individual sources.
2. Definitions
2.1 Leak Definition Concentration. The local VOC concentration at the surface of a
leak source that indicates that a VOC emission (leak) is present. The leak definition is an
instrument meter reading based on a reference compound.
2.2 Reference Compound. The VOC species selected as an instrument calibration basis
for specification of the leak definition concentration. [For example: If a leak definition
concentration is 10,000 ppmv as methane, then any source emission that results in a local
concentration that yields a meter reading of 10,000 on an instrument calibrated with
methane would be classified as a leak. In this example, the leak definition is 10,000
ppmv, and the reference compound is methane.]
2.3 Calibration Gas. The VOC compound used to adjust the instrument meter reading
to a known value. The calibration gas is usually the reference compound at a concentra-
tion approximately equal to the leak definition concentration.
2.4 No Detectable Emission. The local VOC concentration at the surface of a leak
source that indicates that a VOC emission (leak) is not present. Since background VOC
concentrations may exist, and to account for instrument drift and imperfect reproduci-
bility, a difference between the source surface concentration and the local ambient con-
centration is determined. A difference based on meter readings of less than 5 percent of
the leak definition concentration indicates that a VOC emission (leak) is not present. (For
example, if the leak definition in a regulation is 10,000 ppmv, then the allowable increase
in surface concentration versus local ambient concentration would be 500 ppmv based on
the instrument meter readings.)
A-l
-------
2.5 Response Factor. The ratio of the known concentration of a VOC compound to the
observed meter reading when measured using an instrument calibrated with the reference
compound specified in the application regulation.
2.6 Calibration Precision. The degree of agreement between measurements of the same
known value, expressed as the relative percentage of the average difference between the
meter readings and the known concentration to the known concentration.
2.7 Response Time. The time interval from a step change in VOC concentration at the
input of the sampling system to the time at which 90 percent of the corresponding final
value is reached as displayed on the instrument readout meter.
3.0 Apparatus
3.1 Monitoring Instrument.
3.1.1 Specifications.
a. The VOC instrument detector shall respond to the compounds being processed.
Detector types which may meet this requirement include, but are not limited to, catalytic
oxidation, flame ionization, infrared absorption, and photoionization.
b. The instrument shall be capable of measuring the leak definition concentration
specified in the regulation.
c. The scale of the instrument meter shall be readable to ± 5 percent of the specified
leak definition concentration.
d. The instrument shall be equipped with a pump so that a continuous sample is pro-
vided to the detector. The nominal sample flow rate shall be V£ to 3 liters per minute.
e. The instrument shall be intrinsically safe for operation in explosive atmospheres as
defined by the applicable U.S.A. standards (e.g., National Electrical Code by the
National Fire Prevention Association).
3.1.2 Performance Criteria.
a. The instrument response factors for the individual compounds to be measured must
be less than 10.
b. The instrument response time must be equal to or less than 30 seconds. The response
time must be determined for the instrument configuration to be used during testing.
c. The calibration precision must be equal to or less than 10 percent of the calibration
gas value.
d. The evaluation procedure for each parameter is given in Section 4.4.
3.1.3 Performance Evaluation Requirements.
a. A response factor must be determined for each compound that is to be measured,
either by testing or from reference sources. The response factor tests are required before
placing the analyzer into service, but do not have to be repeated at subsequent intervals.
b. The calibration precision test must be completed prior to placing the analyzer into
service, and at subsequent 3-month intei-vals or at the next use whichever is later.
c. The response time test is required prior to placing the instrument into service. If a
modification to the sample pumping system or flow configuration is made that would
change the response time, a new test is required prior to further use.
3.2 Calibration Gases. The monitoring instrument is calibrated! in terms of parts per
million by volume (ppmv) of the reference compound specified in the applicable regula-
tion. The calibration gases required for monitoring and instrument performance evalua-
tion are a zero gas (air, < 10 ppmv VOC) and a calibration gas in air mixture approx-
A-2
-------
imately equal to the leak definition specified in the regulation. If cylinder calibration gas
mixtures are used, they must be analyzed and certified by the manufacturer to be within
± 2 percent accuracy, and a shelf life must be specified. Cylinder standards must be either
reanalyzed or replaced at the end of the specified shelf life. Alternately, calibration gases
may be prepared by the user according to any accepted gaseous standards preparation
procedure that will yield a mixture accurate to within ± 2 percent. Prepared standards
must be replaced each day of use unless it can be demonstrated that degradation does not
occur during storage.
Calibrations may be performed using a compound other than the reference compound
if a conversion factor is determined for that alternative compound so that the resulting
meter readings during source surveys can be converted to reference compound results.
4. Procedures
4.1 Pretest Preparations. Perform the instrument evaluation procedures given in Section
4.4 if the evaluation requirements of Section S.l.S have not been met.
4.2 Calibration Procedures. Assemble and start up the VOC analyzer according to the
manufacturer's instructions. After the appropriate warmup period and zero or internal
calibration procedure, introduce the calibration gas into the instrument sample probe.
Adjust the instrument meter readout to correspond to the calibration gas value. [Note: If
the meter readout cannot be adjusted to the proper value, a malfunction of the analyzer is
indicated and corrective actions are necessary before use.]
4.3 Individual Source Surveys.
4.3.1 Type I —Leak Definition Based on Concentration. Place the probe inlet at the
surface of the component interface where leakage could occur. Move the probe along the
interface periphery while observing the instrument readout. If an increased meter reading
is observed, slowly sample the interface where leakage is indicated until the maximum
meter reading is obtained. Leave the probe inlet at this maximum reading location for
approximately two times the instrument response time. If the maximum observed meter
reading is greater than the leak definition in the applicable regulation, record and report
the results as specified in the regulation reporting requirements. Examples of the applica-
tion of this general technique to specific equipment types are:
a. Valves—The most common source of leaks from valves is at the seal between the
stem and housing. Place the probe at the interface where the stem exits the packing gland
and sample the stem circumference. Also, place the probe at the interface of the packing
gland take-up flange seat and sample the periphery. In addition, survey valve housings of
multipart assembly at the surface of all interfaces where leaks could occur.
b. Flanges and Other Connections—For welded flanges, place the probe at the outer
edge of the flange-gasket interface and sample the circumference of the flange. Sample
other types of nonpermanent joints (such as threaded connections) with a similar traverse.
c. Pumps and Compressors—Conduct a circumferential traverse at the outer surface of
the pump or compressor shaft and seal interface. If the source is a rotating shaft, position
the probe inlet within 1 cm of the shaft seal interface for the survey. If the housing con-
figuration prevents a complete traverse of the shaft periphery, sample all accessible por-
tions. Sample all other joints on the pump or compressor housing where leakage could
occur.
A-S
-------
d. Pressure Relief Devices—The configuration of most pressure relief devices prevents
sampling at the sealing seat interface. For those devices equipped with an enclosed exten-
sion, or horn, place the probe inlet at approximately the center of the exhaust area to the
atmosphere.
e. Process Drains—For open drains, place the probe inlet at approximately the center of
the area open to the atmosphere. For covered drains, place the probe at the surface of the
cover interface and conduct a peripheral traverse.
f. Open-Ended Lines or Valves—Place the probe inlet at approximately the center of
the opening to the atmosphere.
g. Seal System Degassing Vents and Accumulator Vents —Place the probe inlet at
approximately the center of the opening to the atmosphere.
h. Access Door Seals—Place the probe inlet at the surface of the door seal interface and
conduct a peripheral traverse.
4.3.2 Type II-"No Detectable Emission".
Determine the local ambient concentration around the source by moving the probe inlet
randomly upwind and downwind at a distance of one to two meters from the source. If an
interference exists with this determination due to a nearby emission or leak, the local
ambient concentration may be determined at distances closer to the source, but in no case
shall the distance be less than 25 centimeters. Then move the probe inlet to the surface of
the source and conduct a survey as described in 4.3.1. If an increase greater than 5 per-
cent of the leak definition concentration is obtained, record and report the results as
specified by the regulation.
For those cases where the regulation requires a specific device installation, or that
specified vents be ducted or piped to a control device, the existence of these conditions
shall be visually confirmed. When the regulation also requires that no detectable emissions
exist, visual observations and sampling surveys are required. Examples of this technique
are:
(a) Pump or Compressor Seals—If applicable, determine the type of shaft seal. Perform
a survey of the local area ambient VOC concentration and determine if detectable emis-
sions exist as described above.
(b) Seal System Degassing Vents, Accumulator Vessel Vents, Pressure Relief Devices —If
applicable, observe whether or not the applicable ducting or piping exists. Also, deter-
mine if any sources exist in the ducting or piping where emissions could occur prior to the
control device. If the required ducting or piping exists and there are no sources where the
emissions could be vented to the atmosphere prior to the control device, then it is pre-
sumed that no detectable emissions are present.
4.4 Instrument Evaluation Procedures. At the beginning of the instrument performance
evaluation test, assemble and start up the instrument according to the manufacturer's
instructions for recommended warmup period and preliminary adjustments.
4.4.1 Response Factor. Calibrate the instrument with the reference compound as
specified in the applicable regulation. For each organic species that is to be measured dur-
ing individual source surveys, obtain or prepare a known standard in air at a concentra-
tion of approximately 80 percent of the applicable leak definition unless limited by
volatility or explosivity. In these cases, prepare a standard at 90 percent of the saturation
concentration, or 70 percent of the lower explosive limit, respectively. Introduce this mix-
ture to the analyzer and record the observed meter reading. Introduce zero air until a
A-4
-------
stable reading is obtained. Make a total of three measurements by alternating between the
known mixture and zero air. Calculate the response factor for each repetition and the
average response factor.
Alternatively, if response factors have been published for the compounds of interest for
the instrument or detector type, the response factor determination is not required, and
existing results may be referenced. Examples of published response factors for flame
ionization and catalytic oxidation detectors are included in Section 5.
4.4.2 Calibration Precision. Make a total of three measurements by alternately using
zero gas and the specified calibration gas. Record the meter readings. Calculate the
average algebraic difference between the meter readings and the known value. Divide this
average difference by the known calibration value and multiply by 100 to express the
resulting calibration precision as a percentage.
4.4.3 Response Time. Introduce zero gas into the instrument sample probe. When the
meter reading has stabilized, switch quickly to the specified calibration gas. Measure the
time from switching to when 90 percent of the final stable reading is attained. Perform
this test sequence three times and record the results. Calculate the average response time.
5. Bibliography
5.1 DuBose, D. A., and G. E. Harris. Response Factors of VOC Analyzers at a Meter
Reading of 10,000 ppmv for Selected Organic Compounds. U.S. Environmental Protection
Agency, Research Triangle Park, N.C. Publication No. EPA 600/2-81-051. September
1981.
5.2 Brown, G. E., et al. Response Factors of VOC Analyzers Calibrated with Methane
for Selected Organic Compounds. U.S. Environmental Protection Agency, Research
Triangle Park, N.C. Publication No. EPA 600/2-81-022. May 1981.
5.3 DuBose, D. A., et al. Response of Portable VOC Analyzers to Chemical Mixtures.
U.S. Environmental Protection Agency, Research Triangle Park, N.C. Publication No.
EPA 600/2-81-110. September 1981.
A-5
-------
Appendix B
Response Factors of VOC Analyzers
for Selected Organic Chemicals
This appendix presents the results of a laboratory study on the sensitivity of two portable
volatile organic compound (VOC) analyzers to a variety of organic chemicals. The two
analyzers tested were the Century Systems OVA-108 and the Bacharach TLV Sniffer.
In Table B-l are response factors for a 10,000 ppmv meter reading of the instruments
along with the 95% confidence intervals. The instruments were calibrated to 7993 ppmv
methane gas.
Most of the response factors and associated confidence intervals were calculated using
the classical regression method; those computed using the inverse regression method are
noted in this table with the explanatory code "I". Other explanatory codes used indicate
data availability, date applicability, and possible data uncertainties such as the presence
of outliers.
Table B-2 lists compounds tested which do not appear to respond at a 10,000 ppmv
reading at any concentration. Questionable or borderline cases were included in Table
B-l rather than Table B-2.
Reference
Environmental Protection Agency (EPA). September 1981. Response Factors of VOC
Analyzers at a Meter Reading of 10,000 ppmv for Selected Organic Compounds. EPA
600/2-81-051. Research Triangle Park, NC.
B-l
-------
Table B-l. Response factors with 95% confidence intervals estimated at 10,000 ppmv response.
OCPDB*
ID no.
70
80
90
100
no
120
125
ISO
150
170
200
250
2855
330
S60
380
450
490
530
570
590
640
650
660
592
600
630
670
680
690
750
760
780
790
830
890
1740
930
960
210
970
980
990
1010
1040
1060
1120
1130
1140
1150
1160
1190
1270
1215
1216
1244
Compound
name
Acetic acid
Acetic anhydride
Acetone
Acetone cyanohydrin
Acetonitrile
Acetophenone
Acetyl chloride
Acetylene
Acrylic acid
Acrylonitrile
Allene
Ally! alcohol
Amyl alcohol, N-
Amylene
Anisole
Benzaldehyde
Benzene
Benzonitrile
Benzoyl chloride
Benzyl chloride
Bromobenzene
Butadiene, 1,3-
Butane, N-
Butanol, N-
Butanol, Sec-
Butanol, Ten-
Butene, 1-
Butyl acetate
Butyl acrylate, N-
Butyl ether, N-
Butyl ether. Sec-
Butylamine, N-
Butylamine, Sec-
Butylamine, Tert-
Butylbenzene, Tert-
Butyraldehyde, N-
Butyric acid
Butyronitrile
Carbon disulfide
Chloroacetatdehyde
Chlorobenzene
Chloroethane
Chloroform
Chlorophenol, O-
Chloropropene, 1-
Chloropropene, 3-
Chloro toluene, M-
Chlorotoluene, O-
Chiorotoluene. P-
Cresol, 0-
Crotonaldehyde
Cumene
Cyclohexane
Cyclohexanol
Cyclohexanone
Cyclohexene
Cyclohexylamine
Decane
Diacetone alcohol
Diacetyl
Dichloro-1-propene, 2,3-
Dichlorobenzene, M-
Dichlorobenzene, O-
Dichloroethane, 1,1-
Dichloroethane, 1,2-
VoUtility
clax**
LL
LL
LL
HL
LL
HL
LL
G
LL
LL
G
LL
HL
LL
LL
HL
LL
HL
HL
HL
LL
G
G
LL
LL
S
G
LL
LL
LL
LL
LL
LL
LL
HL
LL
HL
LL
LL
LL
LL
G
LL
HL
LL
LL
LL
LL
LL
S
LL
LL
LL
HL
LL
LL
LL
HL
HL
LL
LL
HL
HL
LL
LL
OVA
Response
factor
1.64
1.39
0.80
3.51
0.95
18.70
2.04
0.39
4.59
0.97
0.64
0.96
0.75
0.44
0.92
2.46
0.29
2.99
22.10 D
15.30 D
0.40
0.57
0.50
1.44 I
0.76
0.53
0.56
0.66
0.70
2.60
0.35
0.69
0.70
0.63
1.32
1.29
0.80
0.52
B
9.10
0.38
5.S8 I
9.28
4.56
0.67
0.80
0.48
0.48
0.56
0.96
1.25
1.87
0.47
0.85
1.50
0.49
0.57
0.09 N
1.45
1.54
0.75
0.64
0.68
0.78
0.95
Confidence
intervals
1.11, 2.65
1.09, 1.86
0.57. 1.20
0.69, > 100.00
0.85. 1.06
5.52, > 100.00
1.72, 2.48
0.36, 0.43
3.38, 6.57
0.80, 1.20
0.60, 0.69
0.76. 1.27
0.57, 1.04
0.34, 0.61
0.65. 1.46
1.38. 5.62
0.28, 0.31
1.18, 15.30
3.43, > 100.00
3.96, > 100.00
0.34, 0.48
0.54, 0.60
0.46, 0.55
0.89, 2.34
0.70, 0.83
0.38, 0.81
0.51, 0.62
0.54, 0.83
0.63, 0.78
0.81, 95.60
0.21, 0.95
0.53, 0.98
0.58, 0.87
0.58, 0.70
0.89, 2.20
1.07, 1.61
0.38, 3.14
0.40, 0.74
5.73, 16.20
0.32, 0.47
1.87, 26.40
5.19, 20.00
1.72. 27.20
0.61, 0.73
0.72, 0.90
0.45, 0.51
0.42, 0.55
0.52, 0.61
0.70, 1.45
0.82, 2.24
1.10. 3.71
0.39, 0.58
0.65. 1.20
0.97, 2.76
0.42, 0.57
0.42, 0.86
0.05, > 100.00
0.96, 2.48
1.25, 1.92
0.56, 1.09
0.55, 0.77
0.47, 1.11
0.62, 1.02
0.77, 1.22
TLV
Response
factor
15.60
5.88 I
1.22
21.00 N
1.18
B
2.72
B
B
3.49 I
15.00
X
2.14
1.03
3.91
B
1.07
B
B
B
1.19
10.90
0.63
4.11 I
1.25
2.17
5.84
1.38
2.57 1
3.58 1
1.15
2.02
1.56
1.95
B
2.30
10.70 I
1.47 I
3.92
5.07
0.88
3.90 P
B
18.30 I
0.87
1.24
0.91
1.06
1.17 I
4.36 I
B
B
0.70
B
7.04
2.17
1.38
0.16 I
0.98
3.28
1.75
2.36
1.26
1.86
2.15
Confidence
interval!
7.05, 46.20
2.71, 12.80
0.81, 2.00
1.09, > 100.00
0.94, 1.52
1.65, 5.32
0.44, 27.90
9.68, 26.50
0.45. > 100.00
0.59. 2.59
0.52, > 100.00
0.96, 1.20
0.27, > 100.00
8.11, 15.40
0.58, 0.70
2.16, 7.83
0.99, 1.66
1.34. 4.43
4.20, 8.89
1.15, 1.70
1.17, 5.68
1.82, 7.04
0.75, 2.17
1.14, 4.97
0.77, 5.24
1.42, 2.91
0.96, 12.80
6.53, 17.60
0.62, 3.48
1.87, 12.60
3.08, 9.79
0.77, 1.00
1.58, 14.10
6.50, 51.50
0.69, 1.16
1.08. 1.42
0.40, 7.47
0.33, > 100.00
0.77, 1.77
0.40. 47.40
0.62, 0.80
1.59, > 100.00
1.78, 2.74
1.28, 1.48
0.07, 0.35
0.44, 5.93
2.25, 5.12
1.14, 3.18
0.58, > 100.00
0.35, > 100.00
1.56, 2.25
1.66. 2.92
B-2
-------
OCPDB*
ID no.
1235
12S6
2620
3110
1440
1870
1490
1495
1520
1480
1650
1660
1910
1670
1680
1690
1750
1990
1710
1770
1980
1800
2060
2105
2200
2350
2360
2370
2390
2450
2460
2500
1930
2510
2560
2640
2645
2665
2650
2660
2550
2540
2570
2670
2690
2700
2770
2790
2791
2795
Compound
name
Dicbloroethylene, CIS1.2-
Dichloroethylene, TRANS 1.2-
DichJoromethane
Dichloropropane, 1,2-
Diisobutykne
Dimethoxy ethane, 1,2-
Dimethylformamide, N.N-
Dimethylhydrazine 1,1-
DimethyUulfoxide
Oioxane
Epichlorohydrin
Ethane
Ethanol
Ethoxy ethanol. 2-
Ethyl acetate
Ethyl acetoacetate
Ethyl acrylate
Ethyl chloroacetate
Ethyl ether
Ethylbenzene
Ethylene
Ethylene oxide
Ethylenediamine
Formic acid
Glycidol
Heptane
Hexane, N-
Hexene, 1-
Hydroxyacetone
Isobutane
Iiobutylene
Iioprene
bopropanol
bopropyl acetate
bopropyl chloride
Isovaleraldehyde
Mesityl oxide
Methacrolein
Methacrylic acid
Methanol
Methoxy-ethanol, 2-
Methyl acetate
Methyl acetylene
Methyl chloride
Methyl ethyl ketone
Methyl formate
Methyl methacryiate
Methyl-2-pemanol, 4-
Methyl-2-pentanone, 4-
Methyl-3-butyn-2-OL, 2
Methylal
Methylaniline, N-
Methylcyclohexane
Methylcyclohexene, 1-
Methylpentyno!
Methylstyrene, A-
Morpholine
Nitrobenzene
Nitroethane
Nitrornethane
Nitropropane
Nonane-N
Octane
Volatility
claw**
LL
LL
LL
LL
LL
LL
LL
LL
HL
LL
LL
G
LL
LL
LL
HL
LL
LL
LL
LL
G
G
LL
LL
LL
LL
LL
LL
LL
G
G
LL
LL
LL
LL
LL
LL
LL
HL
LL
LL
LL
G
G
LL
LL
LL
LL
LL
LL
LL
HL
LL
LL
LL
LL
LL
HL
LL
LL
LL
LL
LL
OVA
Roponw
factor
1.27
1.11
2.81
1.03
0.35
1.22
4.19
1.03
0.07 I
1.48
1.69
0.65
1.78
1.55
0.86
3.82
0.77
1.99
0.97
0.73
0.71
2.46
1.73
14.20
6.88
0.41 I
0.41
0.49
6.90
0.41
3.13
0.59
0.91
0.71
0.68
0.64
1.09
1.20
0.82
4.39 P
2.25
1.74
0.61
1.44
0.64
3.11
0.99
1.66
0.56
0.59
1.37
4.64
0.48
0.44
1.17
13.90
0.92
B
1.40
3.52
1.05
1.54
1.03
Confidence
interval!
1.05. 1.56
0.98. 1.27
2.13. 3.87
0.82, 1.33
0.29, 0.44
0.64, 3.61
2.90, 6.58
0.77, 1.45
0.05, 0.11
1.04, 2.33
1.56, 1.84
0.44, 1.58
1.59, 2.01
1.26, 1.96
0.77, 0.95
1.89, 10.70
0.63, 0.97
1.70, 2.36
0.77, l.SO
0.52, 1.11
0.63, 0.82
1.95, 3.29
1.29, 2.46
10.60, 19.80
3.33, 19.70
0.28, 0.60
0.38, 0.45
0.39, 0.66
4.45, 12.10
0.29, 1.04
0.90, 38.50
0.46, 0.80
0.72, 1.20
0.62, 0.83
0.60, 0.77
0.57, 0.74
0.94, 1.29
0.90, 1.71
0.31. 14.70
9.61. 5.60
1.62, 3.34
1.46, 2.1S
0.58. 0.64
1.22, 1.76
0.51, 0.84
2.42, 4.14
0.90, 1.10
1.27, 2.32
0.46, 0.69
0.44. 0.86
1.06, 1.83
3.91, 5.57
0.28, 1.39
0.36, 0.54
0.71, 248
9.50, 21.50
0.67. 1.40
1.20, 1.65
3.03, 4.15
0.80, 1.48
0.94, 2.98
0.89, 1.21
TLV
Re^ionae
factor
1.63
1.66
3.85
1.65
1.41
1.52
5.29
2.70
8.45 I
1.31
2.03
0.69 I
X
1.82
1.43
5.60
X
1.59
1.14
4.74 D
1.56
2.40
3.26
B
5.66
0.73
0.69
4.69 D
15.20
0.55
B
X
1.39
1.31
0.98
2.19 D
3.14
3.49 D
1.06 I
2.01
3.13
1.85
6.79
1.84
1.12
1.94
2.42
2.00
1.63
X
1.46
9.46
0.84
2.79
3.42
B
2.59 I
0.01 I
3.45
7.60
2.02
11.10
2.11
Confidence
interval!
0.99. 3.47
0.67, 12.60
2.46, 6.88
1.06, 3.05
0.96, 2.40
0.65. 8.38
4.05, 7.20
0.51, > 100.00
4.15. 17.20
0.70, 3.60
1.79. 2.33
0.21. 2.30
0.96. 5.12
1.07, 2.00
1.93, 38.80
0.40, > 100.00
0.94. 1.42
1.38, 61.30
1.26, 2.06
0.96, > 100.00
0.78, > 100.00
2.08. 34.70
0.33, 6.10
0.63, 0.76
0.85, > 100.00
6.11, 66.40
0.41, 0.81
0.94, 2.31
1.04, 1.72
0.82, 1.22
1.14, 6.65
1.43. 12.00
1.51, 19.80
0.24, 4.56
1.66, 2.48
1.13, 27.40
1.44, 2.49
4.86. 10.40
0.73, > 100.00
0.93, 1.38
1.72, 2.21
1.39. 5.38
1.40, 3.15
1.22. 2.35
1.24, 1.74
2.55, 35.20
0.68, 1.09
1.79, 5.12
1.83, 8.54
0.64, 10.50
0.00, 82.80
1.56, 13.00
1.91, > 100. 00
1.17, 4.47
3.13, > 100.00
1.68, 2.75
B-3
-------
OCPDB«
ID no.
2851
2973
3063
3066
3070
3090
3120
3130
3230
3290
3291
2860
3349
3393
3395
3400
3410
3420
3450
3510
3520
3530
3570
3550
3560
Compound
name
Pen lane
Picoline, 2-
Propane
Propionaldehyde
Propionic acid
Propyl alcohol
Propylbenzene, N-
Propylene '
Propylene oxide
Pyridine
Styrene
Tetracbloroethane, 1,1.1,2-
Tetrachloroethane, 1,1,2,2-
Tetrachloroethylene
Toluene
Trichlorobenzene, 1,2,4-
Trichloroethane, 1,1,1-
Trichloroethane, 1,1,2-
Trichloroethylene
Trichloropropane, 1,2,3-
Triethylamine
Vinyl acetate
Vinyl chloride
Vinyl propionate
Vinylidene chloride
Xylene, P-
Xylene, M-
Xylene, O-
Volatility'
claw**
LL
LL
G
LL
LL
LL
LL
G
LL
LL
LI
LL
LL
LL
LL
HL
LL
LL
LL
LL
LL
LL
G
LL
LL
LL
LL
LL
OVA
Response
factor
0.52
0.43
0.55 I
1.14
1.30
0.93
0.51
0.77
0.83
0.47
4.22
4.83 D
7.89
2.97
0.39
1.21 I
0.80
1.25
0.95
0.96
0.51
1.27
0.84
1.00 I
1.12
2.12
0.40
0.43
Confidence
interval!
0.42, 0.66
0.38. 0.50
0.46, 0.72
1.00, 1.32
1.03, 1.70
0.77, 1.16
0.45, 0.58
0.44, 2.66
0.74, 0.95
0.40, 0.55
3.45. 5.27
1.24, > 100.00
5.01, 13.80
1.71, 6.11
0.36, 0.43
0.50, 2.94
0.72, 0.90
1.05, 1.50
0.83, 1.09
0.64, 1.78
0.40, 0.70
0.95, 1.82
0.61, 1.38
0.57, 1.74
0.87, 1.52
1.71, 2.68
0.36, 0.46
0.28, 0.85
TLV
Roponie
factor
0.63
1.18
0.60 P
1.71
5.08 D
1.74
B
1.74 I
1.15
1.16
B
6.91
25.40
B
2.68 D
0.47 1
2.40
3.69
3.93
1.99
1.48
5.91 D
1.06
1.21 I
2.41
7.87
5.87 D
1.40
Confidence
intervals
0.57. 0.70
1.08, 1.29
0.59, 0.69
1.11, 3.06
0.73. > 100.00
1.06, 3.50
0.15, 20.30
0.69, 2.46
1.03, 1.34
3.14, 22.50
8.06, > 100.00
0.79, > 100.00
0.32, 0.68
1.81, 3.35
2.77, 5.16
2.68, 6.32
1.27, 3.82
0.96, 2.76
1.26, > 100.00
0.59, 4.60
0.46, 3.20
1.82, 3.35
3.49, 24.90
0.91, > 100.00
0.61, 9.33
•Organic Chemical Producers Data Base
**G-gas; LL = light liquid; HL= heavy liquid
Definition of explanatory data codes:
I =• inverse estimation method
D = possible outlien in data
N = narrow range of data
X * no data available
B= 10.000 ppmv response unachievable
P = suspect points eliminated
B-4
-------
Table B-2. Tested compounds which appear to be unable to achieve an
instrument response of 10,000 ppmv at any feasible concentration.
OVA
OCPDB*
—
790
810
—
—
—
—
1221
2073
—
1660
2770
2910
—
Compound name
Acetyl-1-propanol, 3-
Carbon disulfide
Carbon tetrachloride
Dichloro-1-propanol, 2,3-
Dichloro-2-propanol, 1,5-
Diisopropyl benzene, 1,3-
Dimethylstyrene, 2,4-
Freon 12
Furfural
Methyl-2,4-pemanediol, 2-
Monoethanolamine
Nitrobenzene
Phenol
Phenyl-2-propanol, 2-
TLV
OCPDB
120
—
130
160
360
450
490
530
— '
810
930
1040
1060
1130
—
—
—
—
2060
1221
2073
2200
—
2690
1660
2910
—
—
3230
2860
Compound name
Acetophenone
Acetyl-1-propanol, 5-
Acetylene
Acrylic acid
Benzaldehyde
Benzonitrile
Benzoyl chloride
Benzyl chloride
Butylbenzene, Ten-
Carbon tetrachloride
Chloroform
Crotonaldehyde
Cumene
Cyclohexanol
Dichloro-1-propanol, 2,5-
Dichloro-2-propanol, 1,3-
Diisopropyl benzene, 1,5-
Dimethylstyrene, 2,4-
Formic acid
Freon 12
Furfural
Isobutylene
Methyl-2,4-pentanediol
Methylstyrene, A-
Monoethanolamine
Phenol
Phenyl-2-propanol, 2-
Propylbenzene, N-
Styrene
Tetrachloroethylene
'Organic chemical producers data base ID number.
B-5
-------
Appendix G
Portable VOC Detection Devices
The three tables listed in this Appendix were taken from:
Environmental Protection Agency (EPA). March 1980. Summary of Portable VOC
Detection Instruments. EPA 340/1-80-010.
The instruments are classified as ionization detectors, infrared detectors, or combustion
detectors. These tables are only a general guide as to the instruments that are being
marketed for various uses. Specific applicability for VOC leak detection must be deter-
mined by an analyzer's ability to meet the specifications and performance criteria listed in
EPA Reference Method 21.
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-------
Appendix D
Number of Fugitive VOC Emission
Sources for a Typical Refinery,
Chemical Unit and Gas Plant
The three tables in this appendix give an idea of the number of fugitive VOC sources in a
typical petroleum refinery, a synthetic organic chemicals plant, and a natural gas/gasoline
processing plant. These numbers are estimates based on plant surveys and emission inven-
tory data. In some cases, where emission factors are available, these numbers give an
indication of the relative contribution of each equipment type to the total emissions.
Table D-l. Estimated fugitive VOC emissions from a hypothetical 10-unit
petroleum refinery (15,900 m'/day capacity).
Equipment type
Pump seals
Light liquids
Heavy liquids
Valves
Gas
Light liquid
Heavy liquid
Safety/relief valves
Gas
Open-ended lines
Flanges
Sampling connections
Compressor seals
Totals
Number of
pieces of
equipment
125
125
6,000
9,750
9,750
130
1,750
64,000
250
14
93.339
Uncontrolled
emissions"
(kg/day)
340
62
3,800
2,500
50
500
96
400
90
210
8,048
Percentage of
total
emissions
4
1
47
31
1
6
1
5
1
3
• The number of equipment pieces multiplied by their uncontrolled emission factors (given in
Table 3-1) yields the uncontrolled emissions per refinery.
Source: Environmental Protection Agency (EPA). April 1982. VOC Fugitive Emissions in
Petroleum Refining Industry—Background Information for Proposed Standard
(preliminary draft).
D-l
-------
Table D-2. Fugitive emission sources for three model synthetic
organic chemical manufacturing units.
Equipment component*
Pump seals
Light liquid service
Single mechanical
Double mechanical
Sealless
Heavy liquid service
Single mechanical
Packed
Valves
Gas service
Light liquid service
Heavy liquid service
Safety/ relief valves
Gas service
Light liquid service
Heavy liquid service
Open-ended valves and lines'
Gas service
Light liquid service
Heavy liquid service
Compressor seals
Sampling connections'
Flanges
Cooling towers
Number of components in unit plant*
Model A
5
3
0
5
2
90
84
84
11
1
1
9
47
48
1
26
600
*
Model B
19
10
1
24
6
365
S35
335
42
4
4
37
189
189
2
104
2400
•
Model C
60
31
1
73
20
1117
1037
1037
130
13
14
115
581
581
8
320
7400
«
"Equipment components in VOC service only.
*52 percent of existing SOCMI units are similar to Model A.
33 percent of existing SOCMI units are similar to Model B.
15 percent of existing SOCMI units are similar to Model C.
'Sample, drain, and purge valves.
''Based on 25 percent of open-ended valve's.
'Data not available.
Source: Environmental Protection Agency (EPA). August 1981. Control of Volatile Organic
Compound Fugitive Emissions from Synthetic Organic Chemical, Polymer and Resin
Manufacturing. Control Technology Guideline (CTG) Draft.
D-2
-------
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-------
TECHNICAL REPORT DATA
(Please read Inunctions on the reverse before completing)
1 REPORT NO. 2.
4. TITLE AND SUBTITLE
Controlling VOC Emissions from Leaking Process
Equipment
7. AUTMOR(S)
Gerald T. Joseph, P.E.
Marilyn M. Peterson
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Northrop Services, Inc.
P.O. Box 12313
Research Triangle Park, NC 27709
12. SPONSORING AGENCY NAME AND ADDRESS
U. S. Environmental Protection Agency
Manpower and Technical Information Branch
Research Triangle Park, NC 27711
3. RECIPIENT'S ACCESSION^NO.
S. REPORT DATE
8/19/82
6. PERFORMING ORGANIZATION CODE
il. PERFORMING ORGANIZATION REPORT f
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-02-3573
13. TYPE OF REPORT AND PERIOD COV6RE
Student Guidebook
14. SPONSORING AGENCY CODE
15'SEPA"EPrEoject o'fjficer for this Student Guidebook is R. E. Townsend, EPA-ERC,
MD 20, Research Triangle Park, NC 27711
16. ABSTRACT
This Student Guidebook is designed for technical personnel involved in
monitoring VOC emissions from leaking process equipment. The course reviews
in detail the sources of fugitive VOC emissions and the procecdures and
equipment used to detect the leaks. Course topics include: overview of
regulations, potential sources of VOC emissions, equipment and procedures
used to control VOC leaks, portable VOC detection devices, and inspection
procedures.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
Fugitive VOCs
Process Equipment Leaks
VOC Inspection
13. DISTRIBUTION STATEMENT unlimited
Available from National Technical
Information Service. 5285 Port Royal
Road. Stprinefield. VA 22161
b. IDENTIFIERS/OPEN ENDED TERMS
Self-Instructional
Student Guidebook
19. SECURITY CLASS (This Report)
unclassified
20. SECURITY CLASS (This page)
unclassified
c. COSATI Field/Group
13B
51
68A
21. NO. OF PAGES
102
22. PRICE
EPA Form 2220-1 (9-73)
D-4
-------
Course 417
Final Examination A
This test is closed book. You will be given one hour to complete the test. Each question is
worth 2.5 points. Circle answers on the answer sheet on the last page of this test.
1. Ozone is seldom emitted directly into the atmosphere, but results primarily from a
series of complex chemical reactions in the presence of sunlight.
a. between organic compounds and nitrogen oxides
b. involving TGNMO
c. between organic compounds and sulfur oxides
d. involving VOCs
2. Which of the following is not a Federal regulation?
a. NSPS
b. NESHAPs
c. CTG
S. Liquid service is classified as light or heavy liquid depending on the of
the liquid.
a. total pressure
b. barometric pressure
c. absolute pressure
d. vapor pressure
4. Any organic compound which participates in atmospheric photochemical reactions
is a(n)
a. CO
b. VOC
c. ozone
d. CO,
5. The Federal Control Technique Guidelines (CTGs) are generally applicable to existing
sources
a. in attainment areas.
b. in PSD reviews.
c. in nonattainment areas.
d. regardless of location.
6. Most pumps have a moving shaft which requires a to isolate the fluid
being pumped from the atmosphere.
a. seal
b. motor
c. diaphragm
d. rupture disk
EA-1
-------
7. Mechanical seals often use a barrier or seal fluid to provide for the
moving parts.
a. rust protection
b. pressure relief
c. lubrication
d. better sealing
8. Canned-motor and diaphragm are two types of
a. packed seals
b. sealless pumps
c. centrifugal pumps
d. rotary pumps
9. Compressors are basically that are used in service.
a. pumps, gas
b. seals, liquid
c. pumps, heavy duty
d. valves, continual
10. One of the most common pieces of equipment in an industrial plant is the
a. pump seal.
b. compressor seal.
c. valve.
d. pressure relief device.
11. Like pumps, compressors may leak from the
a. fan
b. motor
c. seal
d. diaphragm
12. or seals are more effective for preventing process fluid leaks
than conventional packing in valves.
a. Diaphragm or bellows
b. Double or tandem
c. Single or double mechanical
d. Vent or relief
13. valves are installed so that they operate with the downstream side open to
the atmosphere.
a. Check
b. Control
c. Block
d. Open-ended
EA-2
-------
14. are designed to open when the process pressure exceeds a set value,
allowing the release of vapors or liquid until system pressure is reduced to its normal
operating level, then it reseats.
a. Rupture disks
b. Pressure relief valves
c. Mechanical seals
d. Flanges
15. Under normal operating conditions, rupture disks totally prevent the release of any
VOC emissions.
a. True
b. False
16. A cap, plug, blind, or second valve can prevent emissions from a(n)
a. pump seal
b. compressor seal
c. open-ended line
d. open-ended valve stem
17. Using a portable VOC detection device to locate a single leaking component is
referred to as
a. a unit area survey
b. fixed-point monitoring
c. calibrating
d. screening
18. have been shown to have a very low emission rate and even though there
are many of them in an industrial plant, they contribute little to the total VOC
emissions.
a. Valves
b. Flanges
c. Pump seals
d. Compressor seals
19. The most effective way to locate a leaking source of VOC is to
a. spray the source with a soap solution and check for bubbles.
b. use a portable VOC detection device.
c. visually check the components.
d. none of the above
20. The hydrocarbon level that indicates that a component needs repair (definition of a
leak) is referred to as the
a. action level.
b. response factor.
c. concentration.
d. emission level.
EA-S
-------
21. repair refers to repairing a leaking component without interrupting the
process.
a. Directed
b. Undirected
c. On-line
22. The most commonly used concentradon-based definition of a leak is any concentra-
tion equal to or greater than ppmv at the source.
a. 100
b. 1000
c. 10,000
d. 100,000
23. For the first attempt at repair, most valves have that can be tightened
while the valves are on-line.
a. stems
b. packing glands
c. yokes
d. bonnets
24. If a second valve is installed on an open-ended line, the valve must always
be closed first to prevent trapping fluid between the two valves.
a. downstream
b. upstream
25. A flame ionization detector measure!! the produced by combustion of the
sample in a hydrogen flame.
a. heat
b. carbon ions
c. CO,
d. CO
26. Unless specially equipped, an FID normally measures
a. TGNMO.
b. individual hydrocarbon components.
c. total carbon content.
d. nonmethane organics.
27. An FID analyzer is capable of accurately measuring any organic vapor leak.
a. True
b. False
28. A photo-ionization detector uses to ionize and then detect organic vapors.
a. ultraviolet light
b. sound
c. pressure
d. hydrogen
EA-4
-------
29. Federal Reference Method 21 requires that any portable VOC analyzer that is used be
equipped with a pump to provide a continuous sample.
a. True
b. False
SO. The calibration gases (reference compounds) to be used are specified
a. in Reference Method 21.
b. in Reference Method 5.
c. in the applicable regulations.
d. by the manufacturer of the analyzer.
31. For hydrocarbon monitoring, NDIR detectors are generally used only for the detec-
tion and measurement of single components.
a. True
b. False
32. A calibration precision test is required to be performed only before placing the
analyzer into service for the first time.
a. True
b. False
S3. Federal Reference Method 21 requires that the portable VOC detector have a
response time equal to or less than
a. 1 second.
b. SO seconds.
c. 1 minute.
d. 5 minutes.
34. The term is defined as the actual concentration of a compound divided
by the observed concentration from the detector.
a. response time
b. calibration precision
c. response factor
d. no response
35. The definition of a leak or action level is specified for the affected facility in
a. the appropriate regulations.
b. Reference Method 21.
c. Reference Method 25.
d. the manufacturer's guide.
36. Most regulations for VOC leaks use the as the affected facility.
a. entire plant
b. individual component
c. process unit
d. all of the above
EA-5
-------
37. For screening potential leaking components, the probe is placed
a. at the surface where leakage could occur.
b. 5 cm from where leakage could occur.
c. 10 cm from where leakage could occur.
d. 25 cm from where leakage could occur.
58. When an increase in VOC concentration is found, the probe is moved until the
maximum meter reading is obtained. The probe is then left at this location for
approximately twice the instrument's
a. response factor.
b. response time.
c. precision time.
39. Equipment that meets a "no detectable emission" limit never has to be monitored for
leaks.
a. True
b. False
40. For a leak definition based on "no detectable emissions" the background concentration
near the source must be measured. "This is done by moving the probe upwind and
downwind at a distance of at most 1. to 2 meters or no closer than 25 centimeters
from the source.
a. True
b. False
EA-6
-------
Date
Course 417
Final Examination A
Answer Sheet
i.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
I certify that
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
this
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
test
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
was administered in
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
accordance with the specified test
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
instructions.
EA-7
Quiz Supervisor
6/82
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