p.1 

OAR Box 1168 

Prepped by Ollie Stewart 

Document Number: 

64) ll-A-2 

Docket Number: 

A-89-10 

Printed 4/29/2008 11:23:18 AM Sheet 64 of 131 
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/*• V * 

&EPA 

United States Office of Air Quality 

Environmental Protection Planning and Standards 

A

9ency Research Triangle Park NC 27^ * "-

EPA-450/3-86-002 

January 1986 

Air 

Emission Factors 

For Equipment Leaits 

Of VOC And HAP 

A-89-10 

II-A- 2 

EPAAIRDOCXCT_ 
P.3 

* ' * 

EPA-450/3-86-002 

Emission Factors for Equipment Leaks 

of VOC and HAP 

Prepared by: 

Radian Corporation 

3200 E. Chapel Hill Road/Nelson Highway 

Research Triangle Park, NC 27709 

Under EPA Contract 

No. 68-02-3889 

U.S. ENVIRONMENTAL PROTECTION AGENCY 

Office of Air and Radiation 

Office of Air Quality Planning and Standards 

Emission Standards and Engineering Division 

Research Triangle Park, North Carolina 27711 

January 1986 
P.4 

V 

DISCLAIMER 

This report has been reviewed by the Office of Air Quality Planning and Standards, U.S. Environmental 

Protection Agency, and approved for publication as received from the Radian Corporation. Approval does 

not signify that the content necessarily reflect the views and policies of the U.S. Environmental Protection 

Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. Copies of this report are available from the National Technical InformationServices, 5285 Port 

Royal Road, Springfield, Virginia 22161. 
TABLE OF CONTENTS 

P.5 

£iae 

LIST OF TABLES . . : iii 

LIST OF FIGURES iv 

Section 1.0 - OVERVIEW 1-1 

Section 2.0 - FUGITIVE EMISSION SOURCES 2-1 

2.1 VALVES , -.-.'. 2-3 

2.2 PUMPS . . . 2-6 

2.3 COMPRESSORS . . . . . 2-10 

2.4 RELIEF DEVICES . 2-11 

2.5 OPEN-ENDED VALVES AND LINES . 2-15 

2.6 SAMPLING SYSTEMS. 2-15 

t.7---FfcANGES-AND-OTHER-CONNECTORS. ; . . . 2-17 

Section 3.0 - EMISSION FACTORS \ 3-1 

3.1 STUDIES CONSIDERED IN SOCMI EMISSION FACTOR DEVELOPMENT . 3-1 

3.1.1 Petroleum Refining Assessment Study. ....... 3-2 

3.1.2 Four Unit EPA Study , . . . * 3-5 

3.1.3 EPA 6-Unit Study 3-5 

3.1.4 DuPont Study 3-5 

3.1.5 Exxon Cyclohexane Study 3-5 

3.1.6 EPA 24-Unit Study 3-6 

3.1.7 Maintenance Study 3-6 

3.1.8 Analysis Report and Revision 

of SOCMI Emission Factors 3-7 

3.1.9 German Studies on Fugitive Emissions 3-7 

3.1.10 Union Carbide Study 3-8 

3.1.11 Analysis of Allied HDPE Unit Data 3-9 

3.1.12 SCAQMD Study 3-9 

3.1.13 Coke Oven By-product Recovery and 

Gas Plant Studies 3-10 
P.6 

TABLE OF CONTENTS (CONTINUED) 

' E-%31 

3.2 EPA'S CHOICE OF DATA FOR SOCMI EMISSION FACTORS 3-10 

3.3 EMISSION FACTOR DEVELOPMENT 3-12 

3.3.1 Detailed Procedural Method. . 3-12 

3.3.2 Statistical Considerations 3-14 

3.3.3 Leak/No-Leak Approach . 3-17 

3.3.3.1 Generation of Leaking and 

Nonleaking Emission Factors 3-19 

3.3.3.2 Computation of Average Emission Factors. 3-20 

3.4 EMISSION FACTORS PRESENTED IN THE AID . . 3-22 

3.5 EXAMPLE HYPOTHETICAL CASE, 3-27 

Section 4.0 - EMISSION REDUCTION . . 4-1 

4.1 OVERVIEW OF TECHNIQUES . . . 4-1 

4.2 LEAK DETECTION AND REPAIR (LDAR) 4-2 

4.3 SUMMARY OF EMISSION REDUCTIONS 4-7 

Section 5.0 - LIST OF REFERENCES T 5-1 

n 
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LIST OF TABLES 

Table ' Page 

3-1 FUGITIVE EMISSION STUDIES IN THE AID 3-3 

3-2 LEAK FREQUENCIES AND EMISSION FACTORS: 

REFINING ASSESSMENT STUDY 3-4 

3-3 LEAKING AND NONLEAKING EMISSION FACTORS FOR 

FUGITIVE EMISSIONS (kg/hr/source) 3-21 

3-4 AVERAGE EMISSION FACTORS FOR FUGITIVE EMISSIONS 

IN SOCMI 3-23 

3-5 LEAK FREQUENCIES BY PROCESS FOR EQUIPMENT 

IN 24 SOCMI UNITS. . . . . 3-28 

3-6 ESTIMATE OF "UNCONTROLLED" FUGITIVE EMISSIONS FOR 

A HYPOTHETICAL CASE. 3-29 

4-1 LDAR INPUTS AND COMPUTED REDUCTIONS FOR 

SOCMI/MONTHLY MONITORING 4-4 

4-2 LDAR MODEL RESULTS FOR SOCMI VALVES AND PUMPS 4-6 

4-3 CONTROL LEVELS FOR SOCMI FUGITIVE EMISSIONS: 

NSPS AND CTG 4-8 

m 
P.8 

LIST OF FIGURES 

Figure ' Page 

2-1 Estimated Emissions by Source Subcategories of SOCMI . . 2-2 

2-2 Diagram of a Gate Valve 2-5 

2-3 Diagrams of Valves with Diaphragm Seals. 2-/ 

2-4 Diagram of a Double Mechanical Seal 

(a) Back-to-back Arrangement 2-9 

(b) Tandem Arrangement 2-9 

2-5 Simple Single-stage Reciprocating Compressor 2-12 

2-6 Pressure Relief Valve in a Basic RD/PRV Combination. . . 2-13 

2-7 Schematics of Closed Purge Sampling Systems 2-16 

3-1 Cumulative Distribution: Cumene Gas Valves 3-13 

3-2 Cumulative Mass Emissions Distribution: 

Cumene Gas Valves * 3-15 

3-3 Cumulative Distribution of Total Emissions by Screening 

Values - Comparison of Confidence Intervals ... . 3-18 

3-4 Comparison of Emission Factors: Gas Valves ...... . 3-25 

3-5 Comparison of Emission Factors: Light Liquid Valves 

and Pumps . 3-26 

4-1 Schematic Diagram of the LDAR Model 4-3 

iv 
GLOSSARY 

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Average emission factor - the per component mass emission rate applicable to 

populations of sources, not individual component measurements. 

Leak definition - the'monitoring instrument reading selected as the trigger 

value for initiating some action such as maintenance; e.g., 10,000 ppmv 

is the leak definition used by EPA. 

Leak frequency - the percentage of sources (a particular equipment type and 

service) determined to be leaking based upon a chosen leak definition. 

Leak rate - see mass emissions rate. 

Leaking emission factor - the per component mass emission rate associated with 

the population of sources with screening values at or above the leak 

definition. 

Mass emissions rate - the quantity of volatile organic compound(s) released to 

the atmosphere in terms of total mass per unit time. 

Monitoring instrument - portable hydrocarbon analyzer meeting the performance 

specifications given in Method 21. 

Non-leaking emission factor - the per component mass emission rate associated 

with the population of sources with screening values less than the leak 

definition. 

Screening value - monitoring instrument reading generally given in 

-^concentration units; e.g., ppmv. 
P.10 

1.0 .OVERVIEW 

One of the first major efforts in the field of fugitive hydrocarbon 

emissions was the Joint Refinery Study initiated by the Los Angeles County 

APCD, the California State Department of Public Health, and the U. S. Public 

Health Service in August 1955. Additional studies were made subsequent to 

this original work. But it was not until the mid- to late-1970's that a 

renewed interest was sparked by two events. 

The Clean Air Act, originally passed in 1970, laid out the groundwork for 

the U. S. Environmental Protection Agency (EPA) to set standards of 

performance for newly constructed, modified, or reconstructed sources of air 

pollution which may endanger the public health or welfare. Since these New 

Source Performance Standards (NSPS) were to be promulgated for a large number 

of industries or industry segments, a ranking was developed in accordance with 

the 1977 amendments so that those industries with the highest potential for 

impacting public health would be examined first. The Synthetic Organic 

Chemical Manufacturing Industry (SOCMI) was placed first on the Priority List 

of industry categories as the single most significant contributor to air 

pollution. 

Around this same time, an extensive study of atmospheric emissions from 

petroleum refining was conducted. The study was initiated to evaluate 

existing and developing refining emissions control technologies and to assess 

the potential impact of atmospheric emissions from refining on the surrounding 

environment. As the program began, fugitive emissions (i.e., emissions from 

various types of equipment such as valves, pumps, compressors, pressure relief 

devices, and connectors) were found to be a large (if not the largest) source 

of hydrocarbon emissions from refining. As a result, the scope of the Refining 

Study was expanded to include the quantification of fugitive emissions. This 

particular objective was given added emphasis as a result of the Clean Air Act 

and its emissions offsets regulations, which require emission factors for 

evaluating compliance. 

Subsequent to the refinery assessment, EPA's research group conducted 

additional studies in chemical plants. Twenty-four separate chemical units 

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were evaluated. Of these units, six were studied more closely for the effectiveness of emission control techniques. These new data, coupled with a 

review of data from other studies', were compiled into an Additional Information Document (AID) on fugitive emissions of VOC in SOCMI. The AID details 

EPA's conclusions abcfut how to estimate emissions and emissions reductions for 

fugitive emissions of VOC. 

. The concepts behind fugitive emissions and their control are relatively 

simple; however, the understanding of fugitive emissions data is quite 

complex. Not surprisingly, the estimates of emissions, emission reductions, 

and costs still draw the bulk of comments' and questions from regulatory 

personnel as well as industry representatives. This document addresses the 

development of emission factors for fugitive VOC emissions (or equipment leaks 

of VOC). The comments and questions most often raised are given below with a 

brief response. Detailed responses, are contained in the substantial 

literature generated by EPA to support the fugitive emission standards. 

1. My emissions are already low because of OSHA regulations. Why, then, are 

there also environmental emissions standards for equipment leaks? 

Environmental emissions standards for equipment leaks have different 

purposes from OSHA regulations. Indeed, they may even result in different 

environmental benefits. Environmental standards focus on reducing the total 

quantity of emissions, in this case VOC emissions, to the atmosphere. On the 

other hand, OSHA regulations, unlike environmental standards, do not 

necessarily limit mass emissions directly. OSHA regulations permit control of 

emission sources by substitution of,, chemicals with less hazardous materials, 

process modifications, worker rotation, process or worker isolation, 

ventiTation controls, or modification of work practices. Such control 

measures, are focused on reducing occupational exposure (as a concentration),-

not necessarily reducing mass emissions of VOC to the atmosphere. 

The idea of workplace concentration reduction is the key to OSHA 

regulations. It is often thought that OSHA regulations result in 

concentrations in the workplace well below 10,000 ppmv, the concentration 

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f? * 

'***•• . 

level used to identify leaking components under the environmental regulations. 

An important distinction is that environmental standards call for measurement 

of VOC concentration at the leak interface, not in the surrounding area. 

Field studies have shown that the concentration of VOC decreases exponentially 

with increasing distance from the leak interface. Thus, a leak determined at 

the interface will rarely be seen at a distance only 20 cm from the surface 

and yet substantial quantities of VOC may be emitted from such a leak. 

Dispersion and dilution of the VOC into the surrounding area mask the severity 

of emissions from the leak. As a result, while OSHA regulations zzj ne.. 

reduce the concentration of VOC in the workplace^ they do not guarantee that 

the total mass emissions from leaks are also reduced. 

I already control my emissions under the Control Techniques Guideline. 

Am I subject to more environmental standards for equipment leaks? 

There are several environmental regulatory programs in existence: 

National Ambient Air Quality Standards (NAAQS), State Implementation Plans 

(SIP's), National Emission Standards for Hazardous Air Pollutants (NESHAP's), 

and New Source Performance Standards (NSPS's).' All of these types of 

regulations work toward meeting the goals of the Clean Air Act. 

The control techniques guideline documents (CTG) are presentations of 

what is considered by EPA to be "reasonably available control technology" 

(RACT). RACT-based environmental regulations are established by States to 

correct existing air pollution problems, focusing on existing sources in 

particular. The control techniques discussed in the CTG for SOCMI fugitive 

emission sources are completely consistent and compatible with standards set 

under other environmental programs. The resultant control levels may vary due 

to differences in the frequency of monitoring or the use of equipment control 

techniques. 

RACT-based standards would not be duplicative with standards set under 

other environmental programs. NSPS's are applicable only to newly 

constructed, modified, or reconstructed facilities. Since they apply to new 

facilities, the requirements of NSPS are. generally more stringent than those 

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of RACT-based standards set for existing facilities. In the case of fugitive 

emissions control, for example, NSPS-based standards would require monitoring 

of equipment more frequently than required under RACT-based standards. 

Similarly, NESHAP's are established for all facilities, new or existing. 

Again, the difference between requirements of NESHAP's and RACT-based 

standards is basically the degree of stringency. NESHAP's require more 

frequent monitoring than RACT-based standards for fugitive emission sources. 

Furthermore, NESHAP's often require the use of control equipment where 

RACT-based standards may only require work practices such as leak detection 

and repairs. Since NESHAP's are applicable to existing sources, as well as 

new sources, their more stringent requirements would need to be met, in excess 

of RACT-based standards for existing sources. 

In terms of emissions estimates, process units complying with the 

RACT-based standards presented in the CTG would indeed exhibit lower emissions 

than would be presented by the simple use of the SOCMI emission factors. As 

shown in Table 4-3 of this document varying degrees of emission reduction are 

achievable under the different standards (NSPS, NESHAP, CTG). Emissions from 

process units complying with the CTG can be estimated by applying the proper 

efficiency to the estimated uncontrolled emissions. 

2. Emissions from my process unit are lower than the SOCMI factors indicate. 

I control the emissions by looking for leaks, sometimes smelling for 

them. Why should my unit be covered by these standards? 

The chemical industry is comprised of numerous processes producing a 

large number of chemicals. Each process unit may by itself emit a relatively 

small amount of VOC; however, the total amount of VOC from the industry is 

significant. Therefore, individual processes or units are not exempted. 

EPA recognizes the wide variability of leak percentages on a unit process 

basis throughout the industry. Of the 24 units surveyed in the 24-unit study, 

15 demonstrated overall leak frequencies for valves in gas/vapor and light 

liquid services of less than 2 percent. Environmental standards, therefore, 

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provide alternatives for units that exhibit low-leak characteristics. For 

example, an owner or operator of a process unit may elect to comply with a 

performance limit of 2 percent leaking valves. In such a case, the routine 

leak detection and repair practices required by the basic rule would not be 

followed. Instead, the process unit would be screened (using Reference Method 

21) on an annual basis to demonstrate that the unit does indeed demonstrate 

the low leak characteristics of less than 2 percent of valves leaking. 

EPA selected this value based upon cost and emissions analyses which 

showed that monthly leak detection and repair for valves is not a cost 

effective control technique for process units exhibiting very low leak 

characteristics. These characteristics may result from the nature of the 

chemicals processed, tight plant design, or enhanced maintenance. 

Fugitive emissions from my process unit are lower than estimated using 

SOCMI factors. I have verified the low leak rates by measuring the 

concentration and flow rate at the ventilation outlet. 

It may well be true that actual fugitive emissions from any given process 

unit are lower than the emissions estimated using the average SOCMI emission 

factors. The SOCMI factors, however, are applicable to the industry at large, 

and should be applied to any individual unit where the leak frequencies for 

equipment have not been established by a rigorous application of Reference 

Method 21. Concentration and ventilation flowrates give an indication of the 

magnitude of fugitive emissions; they would not necessarily provide an 

accurate estimate of total VOC fugitive emissions. For process units that 

would have ventilation outlets, all potential sources of fugitive emissions 

are not generally enclosed in the building. Also, large buildings that house 

chemical process units are not generally air tight; therefore, some VOC may 

not be accounted for in the ventilation air. 

Furthermore, the evaluation of fugitive emissions from an enclosed 

building represents a complex measurement problem. All emission points from 

the building would need to be measured simultaneously for 3 hours to 

constitute an emissions test. This is the only way to ensure that all 

emissions from non-vented sources would be accounted for. Since fan curves 

1-5 
P.15 

are inaccurate for emissions measurements, EPA flow measurement methods would 

need to be employed. These methods require obstruction-free ducting on either 

side of the fan, a situation not always found in ventilation applications. 

Finally, when applied to the estimation of hazardous air pollutants, the 

analytical techniques' used must be capable of speciation of organic 

constituents. Common detectors are not always adequate for this task. 

' Concentration and ventilation flow rate could indicate that emissions are 

lower than estimated by SOCMI factors. This technique, however, would not be 

sufficient to prove that emissions are low. There is an acceptable 

alternative to estimating emissions. Conducting a rigorous Method 21 survey 

would lead to computing percent leaking values (leak frequency) for all 

equipment types. These values could then be used to construct unit-specific 

overall emission factors using "leaking" and "nonleaking" emission factors as 

described in Section 3.3.3. Using such a procedure would develop emission 

factors consistent with the vast amount of fugitive VOC emissions data 

gathered to date. The unit-specific emission factors,, applied to the 

equipment counts for the process unit, lead to the overall-estimate of VOC 

emissions. As noted in this document, pre-survey maintenance would invalidate 

the results of the survey and estimates. 

3. It is not appropriate to use petroleum refinery test data to determine 

SOCMI emission factors. 

The development of VOC emission factors for equipment leaks is founded on 

the concept that equipment leaks VOC at the same, rate regardless of the 

industry or process unit. Total emissions or average emission rates may vary, 

however, based upon the relative percentage of leaks found in different 

process units. In developing VOC emission factors for equipment leaks in 

SOCMI, EPA examined and considered every study available. This evaluation, 

explained in the AID, makes it clear that the data contained in the 

Maintenance Study and 24-Unit Study are not the sole source of data on 

fugitive emissions. Numerous studies have been conducted and these were 

reviewed in the AID, pointing out both strengths and weaknesses associated 

with each study. To gain maximum utility of the data from these studies, 

interpretation of the data is required, drawing upon the strong points of a 

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study while considering its weaknesses. This evaluation and interpretation of 

the data was done in the context of the whole base of fugitive emissions work; 

it was not done just for isolated studies. Based upon this review and . 

analysis, it was determined that the relevant data from different studies had 

to be merged and transformed to provide a useful method for estimating 

emissions. One of the most important studies was the Petroleum Refining 

Assessment. 

The Petroleum Refining Assessment was an enormous study of VOC emissions 

from all facets of refining. A major goal of the work was the investigation 

of fugitive emissions and the development of emission factors that could be 

used to estimate fugitive VOC emissions. The research program, therefore, was 

designed to gather data that would lend itself to generation of such factors. 

As a result, the mass emissions data collected during the Petroleum Refining 

Assessment represent the best available data on VOC emissions from fugitive 

emission sources. Mass emissions data were gathered on sources in chemical 

units to evaluate the effects of maintenance on emissions. The data were not 

collected with emission factor development as the primary goal; therefore, 

these mass emissions data do not represent the highest quality data on mass 

emission of VOC from fugitive emission sources. * 

The work done in petroleum refineries and subsequent studies in chemical 

process units indicated that actual mass emissions (as described by emission 

factors) are related to the number of leaking components compared to the 

number of non-leaking components. The mass emissions data from the Petroleum 

Refining Assessment served as the basis of emission factor development for 

fugitive VOC sources in SOCMI. Recognizing that leak frequencies for 

equipment in SOCMI were different from those reported in the Refining 

Assessment, EPA used leak frequency data for SOCMI to weight the mass 

emissions data from the Petroleum Refining Assessment in generating the SOCMI 

average emission factors. This procedure is detailed in the AID and in this 

report. In the AID, EPA compared the emission factors generated using this 

approach with the factors developed as part of the study of maintenance 

effects in chemical units. The factors were found to be similar except in the 

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case of gas/vapor service valves. Therefore, the chemical unit data were used 

to generate the emission factor for valves in gas/vapor service. 

4. Using average SOCMI emission factors overestimates emissions from my 

process unit, because of the inherent nature of the chemicals I use, 

their volatility, their value, etc. 

In gathering data on the SOCMI, EPA sampled a number of vastly different 

chemical process units. Characteristics of individual chemicals were 

considered in selecting the process units sampled during the 24-Unit Study. 

Hi-volume, low-priced chemicals were included, as were lower-volume, 

higher-priced chemicals. Chemicals with widely divergent volatilities were 

included along with chemicals that are particularly odoriferous. Not 

surprisingly, the frequencies of leaks found ranged from nearly zero to thirty 

percent. Leak frequencies provide an indication of the relative quantity of 

mass emissions and it is apparent from this range of leak frequencies that 

fugitive emissions from some units will be higher and some lower than 

estimates based on the SOCMI factors'. The mass emissions estimates generated 

by EPA using the average SOCMI emissions factors" represent an average that is 

applicable to industry-wide emissions estimates. Without conducting a 

rigorous Method 21 survey to determine the leak frequency (thereby generating 

average emission factors based on the leak/no-leak factor components), the 

average SOCMI emission factors stand as the best estimators of fugitive VOC 

emissions currently available. 

5. I have measured emission rates for some sources in my plant. Why aren't 

these measurements better than the estimates EPA supports? 

The emission factors supported by EPA are based upon a vast amount of 

data gathered on fugitive VOC emission sources using rigorous sampling 

protocols. The factors for each equipment type have been developed 

considering two types of data: leak frequency data and mass emissions data. 

The entire distribution of mass emissions from each class of sources has been 

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considered. For example, 76 individual measurements of mass emission from gas 

valves were taken across the distribution of screening values (i.e., analyses 

measurements) to develop a mass emissions correlation to be applied to 

screening data. Similar distributions of mass emissions measurements are 

necessary for each equipment type to develop the correlations used in 

generating average emissions factors. 

Furthermore, the correlations represent only part of what cc«_> into the 

emissions factors. Screening data (i.e, screening values for all equipment 

components are needed to ensure that the entire distribution of screening 

values is included in emission factor development. 

Limited, isolated measurements of emission rates for "some" sources, 

therefore, are not representative of the entire distribution of sources in the 

process unit. Only*by considering the entire distribution can the emission 

factor be representative. 

6. How do I estimate emissions for my plant... 

(A) if I have no data? 

(B) if I have some measurements? 

(C) if I have done a rigorous Method 21 survey? 

For process units where no emissions data are available, estimates of 

fugitive VOC emissions should be made using equipment counts and the typical 

average emission factors developed for SOCMI. The development of these 

factors given in this document, was explained in the Additional Information 

Document (AID) for VOC equipment leaks. 

In some cases, isolated emission rate measurements may have been made. 

These measurements serve to give the owner or operator a "sense" of the 

quantity of mass emissions that might be emitted from the process unit. 

Again, however, the average SOCMI factors must be employed to estimate 

emissions when only isolated mass emissions measurements have been made. 

Isolated measurements do not represent the entire distribution of screening 

values and mass emission rates present in a process unit. 

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The alternative to using the average SOCMI factors is to employ complete 

leak frequency data gathered using a rigorous Method 21 survey on all 

equipment types. In so doing, the leak/no-leak approach described within can 

be used to estimate emission factors for the specific process unit screened. 

The resultant "custom? emission factors would then be applied to the equipment 

counts for the specific process unit to derive the total fugitive VOC 

emissions estimate for the process unit. This procedure is illustrated for an 

example case in Section 3.5. 

The initial step in generating surrogate emission factors is to use a 

rigorous Method 21 survey on all sources fn the process unit. Method 21 

survey is the promulgated method developed by EPA that is used to monitor 

equipment for leaks. "Rigorous" means that a U sources must be screened and 

that no maintenance of sources should be conducted prior to screening. 

Conducting maintenance immediately prior to conducting the Method 21 survey 

would bias the leak frequencies generated and thus invalidate the subsequent 

emissions estimates based upon the leak frequencies. 

Emissions estimated in this manner should be reviewed on a continual, 

i.e., annual, basis. For example, as time passes^ the leak frequencies noted 

for individual equipment types in a process urrit may change. An annual 

testing using a rigorous Method 21 survey would ensure that emissions 

estimates made using "custom" emission factors would remain representative"^ 

the process unit. 

7. I am not interested in total VOC emissions. How do I estimate emissions 

of a specific pollutant? 

The estimates of VOC emissions represented by the average SOCMI emission 

factors are total VOC emissions. In many instances, only one component in the 

VOC stream is of interest and the estimate of emissions need only reflect thespecific pollutant. In order to reflect compound-specific emissions, the 

estimates, (or emission factor) should be apportioned to reflect the single 

compound (or component) of interest. As illustrated in Section 3.5, a simple 

mass fraction approach can be applied; that is, for equipment in VOC service 

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containing X weight percent of the compound of interest, the emission factor 

could be apportioned by X/100 to reflect emissions of only the single 

compound. 

8. The control costs associated with leak detection and repair are too high, 

particularly in light of low emissions reduction. 

EPA based its estimates of cost on cost data gathered from industrial 

sources during standards development activities. The time estimates used for 

equipment monitoring (i.e., screening) and for repair (of valves) were based 

on information supplied by industry. Cost and cost effectiveness analyses 

were conducted for control of individual equipment types and for complete 

process units. The costs of regulatory alternatives for equipment types were 

judged to be reasonable. Likewise, for process units considered on the 

average, the costs were found to be reasonable. 

EPA recognized, however, that not all process units could be considered 

the model unit average SOCMI norm, described by model equipment counts and 

average SOCMI emission factors. There are tools to examine regulatory 

alternatives, as applied to an entire industry.* Therefore, EPA considered 

alternative control options for those situations where costs became 

unreasonable with respect to the amount of emissions controlled. An example 

of alternative standards allowed by EPA is the 2 percent leaking performance 

limit for valves. In its analysis of regulatory alternatives, EPA determined 

that the costs of control for process units with less than 1 percent leaking 

valves were too high for the relatively small emissions reductions achievable 

by routine leak detections and repair (monthly). To allow for variability in 

measurements, EPA provided a limit of 2 percent leaking. As evidenced by data 

gathered during the 24-Unit Study, there are process units which exhibit low 

leak' characteristics. Owners or operators of such units could opt for meeting 

a 2 percent (or lower) performance limit of leaking valves, as demonstrated by 

an annual Method 21 performance test. 

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P.21 

2.0 FUGITIVE EMISSION SOURCES 

The term fugitive emissions used in the context of volatile organic 

compounds (VOC) refers to leaks from equipment such as valves, pumps, compressors, etc. The term fugitive emissions, also called equipment leaks, 

means the loss of VOC through the sealing mechanism separating the process 

fluid (contained in the equipment) from the atmosphere. 

Fugitive emissions are generally more diffuse than most point sources of 

emissions, especially when considering the collective emissions from widely 

dispersed equipment within a processing plant. *As noted by the emissions 

estimates presented in Figure 2-1, fugitive emissions contribute a large 

proportion of VOC emissions from the chemical industry overall (about 35 percent).1 

As with process-related sources, fugitive emissions sources are readily 

identifiable pieces of equipment within a processing plant. But a major 

difference is in the number of sources found in any given process unit. While 

there may be only a few process-related sources within a process unit (e.g., a 

reactor train and associated distillation columns for purification), there can 

be hundreds or thousands of valves, pumps, flanges, compressors, and other 

fugitive emission sources within a process unU . And while fugitive emissions 

on a per component basis can be small, the collective total of emissions from 

all fugitive sources within a process unit can be large. 

No single control technique is applicable to the control of all types of 

equipment leaks. Neither is a single emission limit universally applicable to 

equipment leaks. Rather, each type of fugitive emission source must be 

considered individually in establishing appropriate, applicable control 

techniques. Equipment controls, operational practices, and work practices are 

all valid approaches to reducing or eliminating VOC emissions from equipment 

leak's, depending on the equipment type. 

Chemical process plants are comprised of numerous major equipment components such as reactors, accumulators, storage tanks, distillation columns, 

condensers, and heaters. There is also a large class of ancillary equipment, 

2-1 
ro 

i 

Organic Chealcal Manufacturing 

544 Gg/yr (1001) 

Process Sources 

1 

I 

Reactor Operations 

I 

I 

Air Oxidation 

Processes 

U O Gg/yr 

(201) 

1 

Reactor 

Processes" 

32 Gg/yr 

(61) 

« 

Non-Process Sources 

\ 

Distillation 

Operations 

H O Gg/yr 

(261) 

Equipnent 

Leaks 

189 Gg/yr 

(351) 

-Storage of 

Organic Liquid: 

47 Gg/yr 

(ax) 

m 

Secondary 

Sourcesc 

26 Gg/yr 

(5X) 

aEstlnates for process emissions sources estlnated using best available Infornation froa current standards 

development prograas (25 October 1902). 

Reactor processes category encovpasses all processes other than air oxidation procosscs. 

Secondary and nlscellaneous enissions estlnated as 5 percent of the total of the other sources. 

Figure 2-1. estimated Emissions by Source Subcategories of SOCMI^ 
most of which involves the transport of chemicals and control of chemical flow 

through the process unit. These components include: 

- Valves 

- Pumps 

- Compressors 

- Pressure Relief Devices 

- Open-Ended Valves or Lines 

- Sampling Connections 

- Flanges and Other Connectors 

These ancillary items of equipment are fugitive e'mission sources. 

2.1 VALVES 

The valve is one of the most basic, common elements found in the chemical 

plant. Valves are available in numerous designs for widely varying applications: gate, globe, control, plug, ball, check, and relief. Most of these 

valve designs (check and relief valves excepted) have a va-lve stem which 

operates to restrict or to open the valve for fluid flow. Typically the stem 

is sealed by a packing gland or 0-ring to prevent leakage of process fluid to 

the atmosphere. Packing glands are the most commonly used sealing mechanism 

for valves, and a wide variety of packing materials are available to suit most 

operational requirements of temperature, pressure, and compatibility. Because 

of design and materials limitations, 0-rings are much less common as the 

sealing mechanism for valves in chemical plants. 

With time and prolonged use, the packing or sealing 0-ring in the valve 

can fail. To eliminate the VOC leakage resulting from the seal failure, the 

valve packing and seals must be replaced or the valve body repaired or 

replaced. Leak detection and repair methods are effective means of reducing 

the leakage of VOC from this class of sources in a plant. Basically, a' leak 

detection and repair (LDAR) program is a systematic program of routinely 

monitoring individual sources (in this case, valves) to identify those sources 

which are leaking. Those leaking sources would then be targeted for repair 

For different source types or industries, the definition of a leak may vary. 

For the purpose of this document, the leak definition is a screening value 

greater than or equal to 10,000 ppmv read on a portable organic compound 

analyzer, in accordance with Method 21. 

2-3 

______• 
(i.e., elimination of the "leak") and for subsequent follow-up monitoring to 

ensure that the repair had indeed been effective in eliminating the leak. 

Maintenance or repair techniques can range from simple, on-line maintenance to complex techniques. Some basic types of maintenance that can be. 

performed on a valve while it remains in-place and in service are: 

(1) tightening or replacement of bonnet bolts, 

(2) tightening of packing gland nuts, and 

(3) injection of lubricant into the packing or seal. 

These valve components are illustrated in Figure 2-2. But simple on-line 

techniques are not always applicable or effective in reducing emissions. For 

example, operational or safety requirements may prohibit repair of some valves 

such as control valves by simple means. Other valves simply cannot be 

repaired effectively on-line and cannot be removed from service. In some 

instances, repair of valves can be effected through more sophisticated repair 

techniques. An example would be the injection of a sealing fluid into the 

equipment. Though relatively expensive, sealant injection has been proven 

effective in petroleum refining applications in California where virtually 

3 

complete elimination of leaks has been mandated. In cases where maintenance 

or repair of valves is not possible, valve replacement may be required. 

There are some valve types and designs that have little or no potential 

for leakage of process fluids: valves with "leakless" or "sealless" 

technology. Two examples are bellows sealed valves and diaphragm valves. 

Bellows seals are the most effective sealing mechanism for valves. Since the 

service life of the bellows can be quite variable, bellows seals are typically 

backed up with conventional packing glands. Bellows seals have been used 

primarily in the nuclear power industry where the relatively high cost can be 

justified by stringent safety requirements. Diaphragm valves, the other major 

type of "leakless" valve, use a diaphragm of some appropriate material to seal 

the process fluid from the stem of the valve. In,some designs, the diaphragmacts as the flow control element as well as the sealing mechanism. Two 

2-4 
P.25 

PACKING 

GLAND 

PACKING 

VALVE 

STEM 

POSSIBLE 

LEAK AREAS 

70-1769-1 

FIGURE 2-2. DIAGRAM OF A GATE VALVE 

2-5 
P.26 

typical designs of diaphragm valves are shown in Figure 2-3. Diaphragm 

valves, however, are a source of fugitive emissions if the diaphragm fails. 

2.2 PUMPS 

0 

Pumps are integral pieces of equipment in most chemical processes, 

providing the motive force for transporting fluids throughout a plant. The 

centrifugal pump is the chief design used in the SOCMI, but other pump lypei. 

are also used. Leakage of process fluid to the atmosphere can occur where the 

moving pump shaft meets the stationary casing. To minimize such leakage, two 

sealing techniques are commonly applied: packed seals and mechanical seals. 

Leak detection and repair programs, described earlier for valves, are 

also applicable to pumps with the potential to leak at the seal. Pumps with 

maintained mechanical seals generally leak less than do pumps with packed 

seals. Failure of a mechanical seal, however, can result in large emissions 

from the pump. Routine monitoring can effectively identify pump seal leaks 

and maintenance repair can reduce emissions. < 

Packed seals consist of a "stuffing box" in the pump casing. Specially 

selected packing materials (chosen on the basis-of the process materials and 

environment) are compressed into the stuffing box with a packing gland, 

resulting in a tight seal around the shaft. Since the shaft must move, either 

rotationally or laterally, lubrication must be supplied to the packing and 

shaft to prevent excessive heat generation from the friction between the shaft 

and packing which could shorten the life of the equipment. Leaks may result 

from the degradation of the packing. 

Leaks from packed seals can often be reduced by tightening the packing 

gland. But at some point, the packing will have deteriorated to the extent 

that it must be replaced. Often, pump packing can only be replaced when the 

pump is out of service. 

Mechanical seals, single and dual, are used to seal pumps with rotating 

shafts. Both have the common attribute of a lapped seal face between a 

stationary element and a rotating seal ring. Although mechanical seals are 

not leakless sealing devices, the leakage of process fluid from the seal can 

be minimized by a properly installed and operating mechanical seal. 

2-6 
P.27 

/ , 

DIAPHRAGM 

DISK 

(A) 

STEM 

DIAPHRAGM 

70-1771-1 

FIGURE 2-3. DIAGRAMS OF VALVES WITH DIAPHRAGM SEALS 

2-7 
P.28 

Since a mechanical seal will leak (unless routinely replaced), the 

ultimate potential for leakage can be reduced through redundancy of sealing 

mechanisms. For instance, a single seal may employ a packed seal as an 

auxiliary sealing mechanism to reduce fugitive emissions. Or the same purpose 

might be just as easily accomplished with some dual mechanical seal 

arrangements (either back-to-back or tandem.) As shown in Figure 2-4, the 

dua.1 mechanical seals in both arrangements form a cavity. 

In the back-to-back arrangement, a barrier fluid circulates between the 

two seals. With the barrier fluid pressure maintained above the pump 

operating pressure, any leakage is across the inboard seal face into the 

process fluid and across the outboard seal face to the atmosphere. The tandem 

arrangement basically has a single seal backed up by another single seal; both 

seals are mounted facing the same direction. The seal fluid (also referred to 

as the buffer or barrier fluid) is circulated through the space between the 

seals. Any process fluids that may leak into the barrier fluid across the 

inboard seal interface may be removed with the barrier fluid or degassed in a 

reservoir. The degassed materials could then be treated in a control system. 

In general, mechanical seaTs have the advantage of improved sealing 

characteristics and auxiliary control for VOC th-at may leak into the barrier 

fluid system. However, repair of mechanical seals can be both costly and time 

consuming. To eliminate a leak from a pump equipped with a mechanical seal, 

the pump must be taken off-line and dismantled to permit repair or replacement 

of the seal. Additionally, care must be exercised to minimize emissions 

resulting from dismantling the pump. 

In addition to these pump types and seal designs, there are several types 

of sealless technology available. Three designs have been applied in the 

chemical industry where leakage cannot be tolerated. The canned-motor pump is 

a shaftless design in which the pump bearings run in the process fluid. The 

motor rotor housing and pump casing are interconnected. Diaphragm pumps 

eliminate all seals and packing exposed to the process fluid through the use 

of a flexible diaphragm (constructed of metal, rubber, or plastic material) as 

the driver for moving the fluid. Magnetic-drive pumps also have no seals in 

contact with the process fluid; the impeller in the pump casing is driven by 

2-8 
P.29 

POSSIBLE LEAK 

INTO SEALING 

FLUID 

FLUID END 

SEAL LIQUID. 

IN (BOTTOM)£ 

PRIMARY 

SEAL 

SECONDARY 

SEAL 

FIGURE 2-4a. DIAGRAM OF A DOUBLE MECHANICAL SEAL 

(BACK-TO-BACK ARRANGEMENT) 

GLAND 

PLATE 

FLUID 

END 

PRIMARY 

SEAL 

BUFFER-LIQUID 

OUT IN 

(TOP) (BOTTOM) 

GLAND 

PLATE 

SECONDARY 

SEAL 70-1767-1 

FIGURE 2-4b. DIAGRAM OF A DOUBLE MECHANICAL SEAL 

(TANDEM ARRANGEMENT) 

2-9 
P.30 

an externally-mounted magnet coupled to the motor. Examples of uses of 

sealless technology for pumps include the handling of organic solvents, 

organic heat transfer liquids, toxic or hazardous materials, and expensive 

materials. 

2.3 COMPRESSORS 

Compressors provide motive force for transporting gases throughout a 

process unit in much the same manner that pumps are used to transport liquids. 

Compressors are driven with rotating or reciprocating shafts. Thus, the 

sealing mechanisms for compressors are similar to those for pumps; that is, 

packed and mechanical seals are the designs primarily used. Again, it is the 

sealing mechanism that is the potential source of fugitive VOC emissions. 

The mechanical seals used on compressors reduce but do not eliminate 

leakage of the process fluid. The types of seals commonly used on compressors 

include: 

- Labyrinth, comprised of interlocking teeth to restrict flow; 

- Restrictive carbon rings, comprised'of multiple stationary 

carbon rings; 

- Mechanical contact, which is similar to the mechanical seal for 

pumps; and 

- Liquid film, which employs an oil film between the rotating 

shaft and stationary gland. 

These mechanical seals can be vented in various manners to a control device 

for elimination of VOC which may leak from the process. The use of packed 

seals is generally restricted to reciprocating compressors where mechanical 

seal designs cannot be used. 

Leakage of VOC to the atmosphere from compressor seals can be detected by 

instrument monitoring at the seal. Repair of mechanical seals requires 

removing the compressor from service. Since compressors in the SOCMI do not 

typically have spares, immediate repair may not be practical or possible 

2-10 
P.31 

without a process unit shutdown. There are optional control techniques that 

are considered effective means of controlling emissions from mechanical seals 

on compressors. One example is venting the barrier fluid system or the seal 

to a control system (for example, a closed vent system connected to a control 

device). » 

Leakage from packed seals may be reduced by tightening the packing gland. 

Figure 2-5 shows a typical arrangement of a single stage reciprocating 

compressor. On some reciprocating designs (particularly newer compressors), 

the distance piece between the compressor cylinder and the drive crankcase can 

be vented to a control device to treat any "leakage through the packing. On 

the older designs, however, this practice may not be possible without 

replacing (or possibly recasting) the distance piece to accommodate the vent 

line or completely replacing the older compressor with a newer design 

incorporating a vent line connection. 

2.4 RELIEF DEVICES 

Relief devices are safety devices commonly used to prevent operating 

pressures from exceeding the maximum allowable working pressures of process 

equipment. The most common pressure relief device is a spring-loaded valve 

(as shown in Figure 2-6) designed to open when the operating pressure exceeds 

a set pressure. The pressure relief valve (PRV) is constructed so that it 

will reseat after the operating pressure has decreased to a level below the 

set pressure. 

Leaks of VOC from relief devices occur through the valve seat. Basically 

two mechanisms are cited for relief device leaks: (1) leakage resulting from 

improper reseating of the valve after a release and (2) leakage resulting from 

process operation at or near the valve set pressure. The latter condition is 

often referred to as "simmering" or "popping." 

Rupture disks (RDs) are pressure relief devices that allow no fugitive 

emissions, if the integrity of the disk is maintained. Upon pressure relief, 

however, the disk bursts and the process vents directly to the atmosphere 

2-11 
Distance Piece 

ro 

i 

Figure 2-5. Simple Single-stuge Reciprocating Compressor 
, <• I 

P.33 

f—•Ttmion-*dju«mtfit 

thimbtt 

CONNECTION FOR 

PRESSURE GAUGE 

* BL.EEO VALVE 

RUPTURE OlSK 

FROM SYSTEM 

Figure 2-6. Pressure Relief Valve in. a Basic RD/PRV Combinati ion 

2-13 
P.34 

until the process pressure has normalized with the atmosphere. Replacement of 

the rupture disk restores the process to a condition of no fugitive emissions. 

Rupture disks should be used in conjunction wi.th relief valves to 

eliminate potential fugitive emissions from relief valves. When mounted . 

upstream of a relief"valve, fugitive emissions are blocked prior to the 

potential leak source, the valve seat. (Leakage may occur if the integrity of 

the-disk is not maintained.) A typical arrangement of an RD/PRV combination 

is shown in Figure 2-6; such systems have been specified by ASME Codes which 

establish the design constraints and criteria to avoid potential safety 

hazards from the practice. For instance, to meet ASME requirements, the space 

between the RD and the PRV must be equipped with a bleed valve and pressure 

gauge that would indicate any pressure build-up resulting from a leaking 

disk.4 

To ensure no fugitive emissions to the atmosphere, the rupture disk must 

be replaced after an overpressure relief. One option that accommodates this 

procedure consists of block valves mounted upstream of the relief devices. 

This option is only possible where safety rules permit the use of a block 

valve in relief line service. (Even where permitted, this practice generally 

includes provisions for locking the block valve°in the open position during 

normal operation.) The other options are dual relief valve systems equipped 

with 3-way valves. By using a 3-way valve, a relief system will always remain 

in service, even when replacing a rupture disk on the other relief 

combination. A number of possible configurations are possible, for this 

option. For instance, the "primary" side (which would be used normally) could 

employ the RD/PRV combination, while, the."secondary" side (which would be for 

back-up service only) could consist of a rupture disk, a pressure relief 

valve, or another RD/PRV combination. 

Soft-seat technology for relief valves consists of using an elastomeric 

0-ring to provide an improved seal when the valve reseats after an overpressure release. The applicability of soft-seat technology is limited by 

materials compatibility and operating conditions. Furthermore, soft-seat 

technology has no impact on emissions from "simmering." 

Fugitive emissions from all mechanisms can be stringently controlled by 

routing the discharge of the pressure relief device to an appropriate control 

2-14 
device via a closed vent system. The most prevalent example of this procedure 

is the use of a flare header. 

2.5 OPEN-ENDED VALVES AND LINES 

0 

Open-ended valves and lines are found throughout chemical plants; they 

are generally drain valves, purge valves, and vent valves. Process fluids m_y 

be emitted to the atmosphere through the valve seat as a result of faulty 

seats or incompletely closed valves. To prevent any atmospheric emissions 

from valve seat leakage, a pipe plug, cap, or blfnd flange can be installed on 

the open end. Another option is the use of a second valve, in something like 

a "block-and-bleed" arrangement. Using this arrangement, after the valves^have 

been opened to allow flow of process fluid, it is best to close the upstream 

valve first. In this manner, no process fluid can be trapped between the two 

valves. f 

2.6 SAMPLING SYSTEMS -

Routine periodic checks of process unit operation are often made by 

sampling process streams to evaluate the performance of reactors, distillation 

units and other operations, and to verify purity and composition of 

feedstocks, intermediates, and products. Process fluids contained in sample 

lines must be purged prior to sampling to obtain a representative sample for 

analysis. The purged fluid is often merely drained onto the ground or into 

the sewer drains, where VOC may be released to the atmosphere. 

Sampling emissions can be reduced by using a closed purge sampling 

system, designed to return the purged VOC to the process or to send the VOC to 

a closed disposal system (e.g., a closed vent system connected to a control 

device).' Examples of closed purge sampling systems are shown schematically in 

Figure 2-7. In one case, the sample is collected as a side-cut stream from 

the purge stream, which flows around a flow-restricting device (e.g., an 

orifice or valve) in the main process line. In the second example, the purge 

is directed through the sample container. These two examples are not the only 

2-15 
-£& 

PROCESS L-l ME. 

«3- -c& 

PROCE.SS LIME. 

X 

i 

tr» V 

SAMPLE . 

COMTAIME R 

SAMPLE. 

COMTAIM6. R 

Figure 2-7. Schematics of Closed Purge Sampling Systems 
P.37 

closed purge sampling systems possible. For instance, closed purge sampling 

may also be done with partially-evacuated sample containers. 

a 

2.7 FLANGES AND OTHER CONNECTORS 

Flanges and other connectors comprise the single largest class of 

fugitive emission sources in a process unit, in terms of total numbers. 

Flanges are gasket-sealed junctions used to mate pipe and other equipment such 

as valves, vessels, and pumps. Flanges may be used in pipe sizes 50 mm 

(2 inches) or greater in diameter. Other connectors, such as threaded connections and nut-and-ferrule connections, perform the same function as flanges, 

but they are used primarily on line sizes less than 50 mm in diameter. 

Flanges and other connectors may leak VOC as a result of: 

- improperly selected gaskets; f 

- poorly assembled flanges; * ' 

- poorly assembled nut-and-ferrule combinations; pr 

- cross-threaded pipe connections. 

The major cause of VOC leakage from flanges and other connectors is 

deformation of sealing surfaces as a result of thermal stress. VOC leaks from 

flanges and other connectors can be determined using instrument monitoring 

techniques; potential leaks may be evidenced through other means such as 

visual, auditory, or olfactory means. Tightening bolts on flanges is one 

method of effectively sealing VOC leaks from some flanges. Generally, 

however, flange gasket replacement or correction of a leaking connector 

requires partial or complete process unit shutdown. And emissions from the 

shutdown or repair procedure could even exceed the long-term emissions from 

the 'leak itself. 

2-17 
P.38 

3.0 EMISSION FACTORS 

In evaluating standards of performance or even the effectiveness of 

individual programs of emissions reduction, the estimation of emissions from 

a given source is a key element. Source testing for process emission 

sources, such as reactor vents, etc., is a relatively .^trcightForward 

procedure. Estimating emissions from widely dispersed fugitive emission 

sources canbe somewhat more difficult. 

One of the first published studies of fugitive emissions was conducted 

in several petroleum refineries in the Los Angeles County Air Pollution 

Control District. The estimates of this 1950's joint study showed that 

potentially a large quantity of hydrocarbons could be lost to the atmosphere 

from various sources such as valves, pump and compressor seals, cooling 

towers, flanges, and pressure relief valves. 

It was., the middle 1970's t*efare_ another comprehensive- .^esogjt^Mr- t 

emissiofls^fj-^^prtr^e^.. reftnegt*?> fas mad*.^-i }n_ tbfcSy rawrv -"ife^pft^ 

emissions measurements^ wepe m«_e.;atv 1£ refineries located throug^ou* the 

United States. Emission factors, screening relationships, and correlations 

were generated from data collected on valves, flanges, pump seals, 

compressor seals, drains, and pressure relief valves. The focus of this 

study was the assessment of atmospheric emissions in petroleum refineries, 

and it was surprising to many people to find that fugitive emissions were a 

major contributor to the total air emissions from a refinery. 

The Refining Assessment Study was subsequently used as a primary 

reference in standards development activities by EPA. The Refining 

Assessment Study was then augmented with other information available in the 

literature and additional studies of fugitive emissions conducted in 

chemical process units. 

3.1 STUDIES CONSIDERED IN SOCMI EMISSION FACTOR DEVELOPMENT 

Since the initial fugitive emissions work done in the 1950's LA County 

studies, numerous research efforts have focused on understanding fugitive 

3-1 
P.39 

emissions of VOC. Studies have considered leak frequency, leak rate, 

emission factors, methods of leak prevention, and the effectiveness of leak 

prevention techniques on reducing the number of leaks and mass emissions 

associated with them. The studies listed in Table 3-1 are briefly described 

below. Each study Is summarized with respect to method and results. Actual 

numerical results have been summarized in the Additional Information 

Document (AID) for Fugitive Emission Sources of Organic Compounds. 

3.1.1 Petroleum Refining Assessment Study 

The Refining Assessment Study was designed to provide comprehensive 

emissions data from a representative number of fugitive emission sources in 

each refinery tested. In each of the 13 refineries tested, equipment in 

several process units were sampled. A total of 500 to 600 emission sources 

in each refinery were screened or sampled. To eliminate potential bias from 

source sele-ction, all individual sources were preselected from piping and 

instrumentation drawings before entering the refinery. 

Unlike previous studies, data were gathered on screening value (i.e., 

portable organic vapor detector instrument reading) and mass emissions. 

These data permitted the development of average emission factors and the 

correlation of the maximum observed screening value and the measured 

non-methane leak rate of VOC. The leak frequencies determined from field 

measurements and the average emission factors computed are shown in 

Table 3-2. These results served as the principal data against which other 

fugitive emissions work by EPA would be compared. 

The Refining Assessment Study also provided some other very important 

results. The only equipment or process variable found to correlate with 

fugitive emission rates was the volatility of the stream components. This 

result led to the separation of equipment component emissions by service: 

gas/vapor, hydrogen, light liquid and heavy liquid. These classifications 

have been used in most fugitive emissions standards to direct effectively 

the major effort toward equipment most likely tp leak. 

3-2 
P.40 

Table 3-1. FUGITIVE EMISSIONS STUDIES IN THE AID 

Reference 

No. 

6 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19,20 

Petroleum Refining Assessment Study 

Four Unit EPA Study 

EPA 6-Unit Study 

Du Pont Study 

Exxon Cyclohexane Study 

EPA 24-Unit Study 

Evaluation of Maintenance for Fugitive VOC Emissions Control 

Analysis of Fugitive Emissions Data 

Revision of Emission Factors/SOCMI Processes 

German Studies 

Union Carbide Study 

Evaluation of Allied HDPE Study 

Coke Oven By-Product Recovery and Gas Plants Studies 

1 

3-3 
P.41 

TABLE 3-2. LEAK FREQUENCIES AND EMISSION FACTORS: 

REFINING ASSESSMENT STUDY 

Equipment 

Emission Factor 

Percent of 

Sources 

Service kg/hr/source >10,000 ppm 

Valves 

Pump Seals 

Compressor Seals 

Pressure Relief Valves 

Gas 

LLb 

HLC 

LL 

HL 

Gas 

Gas 

0.0268 

0.0109 

0.00023 

0.114 

0.021 

0.636 

0.16 

10 

11 

0.2 

24 

2 

36 

7 

Flanges All 0.00025 0.5 

Open-Ended Lines All 0.0023 7.7 

From Appendix B of the Refining Assessment report 

(EPA-600/2-80-075C). Reference 21. 

bLL - light liquid service; i.e., compounds with vapor pressure greater than 

kerosene. 

CHL - heavy liquid service; i.e., compounds with vapor pressure of kerosene 

and lower. 

3-4 
P.42 

3.1.2 Four Unit EPA Studv8 

Although designed along the same lines as the Refining Assessment 

Study, this study conducted by EPA-IERL (RTP) was too limited in scope to 

yield results with reasonable confidence intervals for most source types. 

The most important result of the Four Unit Study was that of illustrating 

the need for more intensive sampling and screening. 

3.1.3 EPA 6-Unit Studv9 

The 6-Unit Study was the next level in testing of fugitive emissions 

conducted by EPA. For this study, leak frequencies (as determined using a 

portable organic analyzer and considering a 10,000 ppmv leak definition) 

were evaluated for all potential sources on an individual component basis. 

Plant personnel identified those equipment believed to handle organics. And 

no attempt was made to segregate equipment by service (e.g., in gas/vapor 

service, in light liquid service, etc.). No emission rate measurements were 

made, so no emission factors were determined. 

3.1.4 Du Pont Studv10 

E. I. duPont de Nemours conducted an independent survey of two of their 

process units to evaluate the leak frequencies of pumps and valves and the 

leak rates of valves. A portable organic analyzer (calibrated to hexane) was 

used to identify leaks of 10 ppm or greater. Du Pont evaluated actual leak 

rates on only 6-8 valves. The study had a limited data base for pumps and 

valves and was restricted to two older process units. Du Pont's leak 

definition was inconsistent with EPA work. And finally, there was no 

determination of an average emission factor. 

3.1.5 Exxon Cyclohexane Study 

Exxon Chemical Company conducted a study of fugitive emissions sources 

at its Baytown cyclohexane unit. Valves were screened using a soap solution 

(soaping); pump seals, compressor seals and safety valves were instrument 

3-5 
P.43 

screened using an undefined leak definition. Valve leaks were classified as 

small, medium, or large for selection for mass emissions sampling. The 

percentage of leaks and emission factors determined from the study could not 

be related to EPA's work due to the inconsistencies in leak definitions 

between the two studies. 

3.1.6 EPA 24-Unit Study12 

In 1980, EPA coordinated a study of 24 individual chemical process 

units. The process units were selected to represent a cross-section of the 

population across SOCMI. Among the chemical compounds included in the 

survey were acrylonitrile, ethylene dichloride, formaldehyde, 

perchloroethylene, and vinyl chloride. Selections of equipment to be 

screened were made prior to screening activities; screening was conducted by 

two-person teams Using portable organic analyzers. Calibration was done 

daily at a minimum. A large number of the following types of equipment were 

screened in the 24 units for determination of leak frequency: flanges, 

process drains, open-ended lines, agitator seals, relief valves, valves, 

pump seals, and compressor seals. These sources were further grouped by the 

chemical phase of the material being handled: in gas/vapor service, in light 

liquid service, and in heavy liquid service. 

3.1.7 Maintenance Study 

A study of the effects of maintenance on emissions was performed 

concurrently at six of the units screened in the 24-Unit Study. This work 

yielded quantitative estimates of leak occurrence and recurrence rates and 

of the effects of maintenance on fugitive emissions. Coincident with these 

estimates, correlations of screening values and leak rates were made. 

The Maintenance Study focused on gas valves, light liquid valves, and 

light liquid pumps in three types of process units: ethylene, cumene, and 

vinyl acetate. The units selected were considered to be representative of 

the level of control existing in the chemical industry. 

3-6 
P.44 

14 1 5 

3.1.8 Analysis Report and Revision of SOCMI Emission Factors 

Data gathered during the 24-Unit Study and the Maintenance Study were 

subjected to a more in-depth analysis. The data analysis tasks included in 

the report were generation of average emission factors, analysis of leak 

frequency as a function of process parameters and equipment design, analysis 

of the impact of instrument response factors on leak frequency, and analysis 

of the impact on mass emissions of leak occurrence and recurrence rates. 

Leak frequencies for the various source types varied among the 15 process 

units and among source types. Higher leak frequencies were found to be 

associated with higher line pressures, while line temperature appeared to 

have no consistent effect. 

Average emission factors were developed for gas valves, light liquid 

valves, and light liquid pumps in the three process unit types examined in 

the Maintenance Study. In this case, emission factors were generated only 

for these processes since the leak rate/screening value correlations 

developed depend on process type. These emission factors were later revised 

to account for data biasing due to off-scale instrument readings and 

maintenance effects. The values determined were generally found to be lower 

than the average emission factors determined for petroleum refineries. 

3.1.9 German Studies on Fugitive Emissions 

Four studies conducted by industry and government groups in West 

Germany investigated fugitive emissions and methods of prevention in 

chemical and petrochemical plants. The sources studied included flanges, 

threaded connections, compressor seals, pump seals, agitator seals and 

valves. Four different methods of leak rate determination or estimation 

we're employed. 

The studies were inconclusive in giving the quantitative dependence of 

leakages on chemical, physical, and design parameters of sealing elements. 

Insufficient data were cited as the reason. Leak rates found for the 

sources investigated were in general about 1/10 of the values previously 

published in the literature. It is important to note that the low values 

represent leakage rates for well-maintained facilities. In addition, 

3-7 

________ 
_P_45 

the studies noted that prior to any directed maintenance activity, the leak 

rate for valves was 200 percent of the published value. Most of these 

emissions were reduced by repair of a single large leak prior to additional 

measurements. 

0 

17 

3.1.10 Union Carbide Study 

Union Carbide conducted a study of a single process unit to 1) find all 

leaking points in the unit, 2) quantify the leak rates for these points, and 

3) develop a statistical fugitive emissidn sampling plan for future work. 

Leaks were determined using a portable organic analyzer calibrated with 

hexane for a 1,000 ppmv leak definition. An overall leak frequency of 6.7 

percent was found for the 1,569 points screened. Pump seals and open-ended 

lines demonstrated the highest leak frequencies at over 30 percent. 

Point leak rates were determined by various means for all sources 

determined to be leaking (i.e., screening at or above 1,000 ppmv). The 

method of determining the leak rate depended upon the rate of leakage (high; 

medium; low) and temperatures. .The leak rates were not classified by source 

type (eg., pump seal, valve, etc.). Rather,,they were reported by the 

degree or extent of leakage: (1) small leak (0:001 - 0.02 lb/day); (2) wet 

surface (0.1 - 0.5 lb/day); (3) dripping or strong unbearable odor (1 - 20 

lb/day); and (4) continuous flow (50 - 150 lb/day). No leak rates were 

established for sources screening less than 1,000 ppmv. The leak rates were 

not used in developing EPA's factors since they could not be compared to 

data gathered by EPA. 

In its recommendations, Union Carbide cited development of a leak 

rate/screening value correlation as an improvement in estimating emissions. 

In addition, the work done by Union Carbide recognized that, in order to 

establish leak rates for 13 equipment types, some 23,000 sources would have, 

to be screened and 1,000 leak measurements made to obtain data within the 90 

percent levels of confidence desired. 

3-8 
P.46 

3.1.11 Analysis of Allied HDPE Unit Data18 

Kemron Environmental Corporation, in conjunction with Allied Chemical, 

conducted a 10-month study of flanges and valves in a new high density 

polyethylene (HDPE)'unit. Basically focusing on maintenance effects, six 

screening and emissions measurement tests were performed on valves and 

flanges over the course of the study. Screening was done using a portable 

organic analyzer calibrated to 1,000 ppmv hexane. (Unlike the EPA studies, 

a high concentration calibration standard was not used, nor was calibration 

verified at the completion of daily screening*. While leak rates were 

determined for sources screening at 10,000 ppmv or greater, these rates are 

not comparable to average emission factors. (Average emission factors 

consider emissions from all valves across an entire distribution of 

screening values, not just values higher than 10,000 ppmv.) Further, some 

of the valves sampled for leak rate had been subjected to a directed 

maintenance program prior to sampling. This action resulted in lower 

emissions than would be expected in the absence of any maintenance efforts. 

3.1.12 SCAQMD Study22 

To evaluate the effectiveness of fugitive emission control regulations, 

EPA conducted a survey of two refineries in the South Coast Air Quality 

Management District (SCAQMD) in California. Accessible valves, pumps, 

agitators, open-ended lines, drains, and relief valves in 8 process units 

were screened using EPA Reference Method 21/ No flanges were surveyed 

during this study. Since this was a maintenance-oriented study, no mass 

emission rate measurements were made. 

3-9 
P.47 

3.1.13 Coke Oven By-Product Recovery19 and Gas Plant Studies20 

Three coke oven by-product recovery plants were tested for fugitive 

benzene emissions. Source screening was done with two different types of 

portable organic analyzers. Emissions data gathered were categorized 

according to source type and stream benzene, content, but no distinction of 

service was made. Non-methane hydrocarbon emission factors were generated 

for valves, pump seals, and exhausters (i.e., compressors mainly in hydrogen 

service). 

A total of six natural gas processing plants were tested by EPA and the 

23 American Petroleum Institute (API). Screening was done by both soaping 

and portable organic analyzers. Leak rate data collected during the 

combined study were used to estimate leak rates for emitting sources. These 

results were then applied to the population to estimate the average emission 

factors for connections and flanges, open-ended lines, pressure relief 

devices, valves, pump seals, and compressor seals. 

3.2 EPA'S CHOICE OF DATA FOR SOCMI EMISSION FACTORS 

EPA used three major criteria in evaluating data to use to estimate 

fugitive VOC emissions: 1) relevance to fugitive emissions, 2) validity of 

the testing and analytical procedures, and 3) comparability to other studies 

to allow validation of results. 

The studies of fugitive emissions summarized above were evaluated in 

the AID with respect to their relevance to estimating fugitive emission 

factors. For example, the emission factors generated in the Maintenance 

Study were not considered the highest quality, best available data on mass 

emissions; estimation of emission factors was not the principal purpose of 

the Maintenance Study. The factors were used, however, to evaluate the 

results of the emission factor estimates made. • 

The second criterion was used to eliminate from consideration data that 

were not collected by clear, consistent, acceptable test procedures. For 

example, the result of studies under scrutiny would need to be evaluated 

with respect to 1) how the samples were collected, 2) how the measurements 

were made (field or laboratory), and 3) what type of equipment was 

3-10 
P.48 

represented by the reported data (only leaking equipment, complete distribution of equipment, etc.). This same sort of evaluation was needed to 

consider differences in leak definition, method of determining leaks . 

(soaping, instrument screening), and monitoring instruments. 

The final criterion was comparability of the studies. Data from both 

the Refining Assessment Study and the combined SOCMI studies were gathered 

in the same manner using comparable instrumentation and leak detection 

criteria. Statistically, the data were handled in a similar manner in 

studying emissions and the various effects of various parameters on 

emissions. It was only because the data from the Refining Assessment Study 

and the combined SOCMI studies were comparable that the two studies could be 

evaluated against'one another. Mass emissions data from the Refining 

Assessment Study and leak frequency data from the SOCMI work were then 

combined to form a single set of emission factors. 

As detailed in the AID, EPA determined that the best data available for 

estimating emission factors for fugitive VOC emissions from SOCMI was from 

the Petroleum Refining Assessment Study and from the SOCMI 24-Unit Study. 

These studies satisfied the three major criteria for emissions estimate 

data. EPA compared the two data sets and "acknowledged there were 

differences that could not be explained conclusively. The Petroleum 

Refining Assessment data were considered the best data on mass emissions 

from fugitive emissions sources. The Refining Assessment Study was planned 

with estimation of VOC fugitive emissions as one of its objectives. VOC 

emissions data were gathered according to equipment type and service (i.e., 

gas/vapor, light liquid, heavy liquid). These data are considered 

applicable to VOC fugitive emissions, regardless of industry. The 24-Unit 

Study best represented the leak frequencies that might be expected across 

SOCMI. Therefore, fugitive source emission factors for SOCMI were based on 

the Refining Assessment and SOCMI emissions data, adjusted using the results 

of the 24-Unit Study. This procedure is detailed in Section 3.4. 

Several approaches to estimating the emission factors were considered. 

The estimation procedure presented in the AIO maintained consistency with 

the mathematical procedure followed in developing the emission factors 

presented in the Refining Assessment Study and SOCMI Maintenance Study. 

Before detailing the estimation procedure presented in the AID, the methods 

3-11 
followed in the Refining Assessment and SOCMI Maintainance Studies are 

presented. 

3.3 EMISSION FACTOR DEVELOPMENT 

3.3.1 Detailed Procedural Method 

The development of average emission factors for individual fugitive 

21 emission sources was laid out in the Petroleum Refining Assessment Study. 

Since then, embellishments have been added to this procedure to account for 

censoring of data (i.e., sources screened at the maximum instrument reading) 

and other sampling effects (eg., pre-maintenance screening, post-maintenance 

screening, etc.). The average emission factor is not merely the average of 

the mass emissions measurements made on any given type of equipment. The 

process is somewhat more involved than a simple average. 

Two types of fugitive emissions data were gathered for the development 

and analysis of emission factors. First, screening . data (i .e., 

concentration measurements) were collected for a set of sources. Using 

these raw screening data, empirical cumulative" distribution functions were 

generated. The empirical distribution function would be a key element in 

estimating an average emission factor. It was found that the cumulative 

distribution functions were adequately described by . a log-normal 

distribution. This led to the generation of modeled cumulative distribution 

functions for source screening. These functions relate the screening value 

of a source to a leak frequency. An example of a modeled cumulative 

distribution function is found in Figure 3-1. From such a figure, the 

percentage of sources "leaking" (based upon a selected leak definition) can 

be established. 

The second type of fugitive emissions data gathered for average 

emission'factor development was mass emissions data. Individual sources 

were "bagged" and measured for mass emission rate (leak rate) and screening 

value. The mass emissions rate data pairs were regressed to yield leak 

rate/screening value correlations for the various source types. As with any 

experimental program, there will be some degree of variability in* the data 

gathered, especially as it is applied to estimate other emissions from 

sources not tested. Confidence intervals give an indication of the range 

3-12 
3-13 

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LOGI0COVA SCREENING VALUE) 

t 

3-1 . Cumulative Distribution : Cuniene Gas Valves. 

0 
P.51 

and the degree over which the results are applicable. The number of data 

pairs necessary to develop this correlation depends upon the confidence 

intervals desired in the final value. For example, for the 95 percent 

confidence level currently used in fugitive emissions work, 76 data pairs 

distributed over the range of screening values found are needed to generate 

the screening value/mass emissions rate correlation for valves. 

By combining these two data sets, cumulative mass emissions 

distributions were established. The leak rate/screening value correlation 

(from mass emissions data) was applied to the cumulative distribution 

function (from screening data) to result" in a cumulative mass emissions 

distribution function for each source type. Figure 3-2 shows an example of 

this distribution for cumene gas valves. The cumulative mass emissions 

distribution yields the percentage of mass emissions (of a source type) 

associated with a selected leak definition. This value is important in 

generating the leaking and non-leaking emission factors discussed in Section 

3.3.3. 

The generation of the average emission factor made use of the empirical 

screening distribution data and the leak rate/screening value correlation. 

Using the correlation (developed from mass emi-ssions data), leak rates were 

estimated for all sources that had been screened. The sum of the individual 

leak rates represented the total mass emissions leak rate for the class of 

sources being considered. The average emission factor was derived by 

averaging the sum over the total number of sources that were screened. The 

resultant average emission factor, therefore, considered the entire 

distribution of sources (and screening values). It was not merely the 

average of measured leak rates determined for some sources out of the 

population. Because the result of the procedure is an average emission 

factor, it should only be applied to populations of sources, and not to an 

individual component. 

3.3.2 Statistical Considerations 

Of course, in generating emission factors and in evaluating their 

quality, statistical considerations must be made. For example, there is a 

3-14 
3-15. 

• 

• • 

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P 100 

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Figure 2 

. •-••_ . *" ,T»-^5___ = _ C - ^ 

\ \ \ 

\ \ \ 

\ \ \ 

\ \ \ 

\ \ \ 

\ \ \ 1V 

— Eetlaated Percent of Total . \ 

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to Suurcea With Screening V 

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LOGI0COVA SCREENING VALUE) 

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1-2. Cumulative Mass Emissions Distribution : Cumene Gas Valves. 

-

-
P.53 

minimum number of data pairs (screening value and mass emission measurement) 

required to generate a statistically valid screening value/leak rate 

correlation. And the number of data collected in the screening survey of 

any population of sources will have a direct impact on the confidence 

intervals associated with the modeled results. 

From the previous discussion on the emission factor development 

procedure used 1n the Refining Assessment and the SOCMI Maintenance Studies, 

three models are necessary to generate average emission factors. The 

screening value distribution is first modeled to a log-normal distribution 

for sources screening at more than 10 ppmv. The confidence intervals for 

the cumulative function are evaluated using the published values for the 

Binominal Distribution. At the 95 percent confidence level, the estimated 

A 

cumulative percent leaking (p) is given as: 

i ± 1.96 [p (1 - p)/nl1 /2 

where n is the number of screening values for the particular source type 

under consideration. From this equation, it is evident that, since the 

width of the confidence interval varies with the inverse square root of the 

number of sources screened, a larger population of screened sources yields a 

smaller confidence interval. 

Next, the screening value/leak rate correlations should be considered, 

again with respect to the confidence interval. Leak rates are modeled in a 

log-log relationship assuming a binomial distribution, according to: 

Log (leak rate) ° @+{l (log(screening value)) + Z (standard error) 

where: a , p -=» model parameters; 

Z ° standard normal random number; and standard error is 

associated with the individual predictor equation. 

Again, published Binomial Confidence Interval tables are used to generate 

the confidence intervals around the average of the log (leak rate) 

estimates, (y). For example, the value at the lower confidence interval is: 

3-16 
P.54 

C] - y - 2.24 [s2/(n-r)]1 /2 

2 

where: s - variance of the estimate; and 

(n-r) • number of leaking sources. 

The equation shows the effect of the number of data points in the survey on 

the size of the confidence interval. During studies of fugitive emissions 

in On-Shore Gas Production units, a minimum of 76 data pairs were necessary 

to develop the screening value/leak rate .correlation within the 95 percent 

24 confidence interval required of the final emission factor. 

The final confidence interval values for the emission factor are 

actually the product of the value for the (bias-corrected) leak rate 

estimate (shown above) and the value for the percent of sources leaking. 

The confidence intervals for percent of sources leaking are obtained by 

iterative solution of summation series equations. For example, the lower 

confidence limit, P., should be determined from: 

J . (?)

 pi

 (1" V " * ' 

where: (l-a) represents the confidence level, n is the number of sources 

screened, and k is the number of leaking sources. As the number of sources 

screened increases, the confidence level increases and the confidence 

interval narrows. This.is vividly illustrated in Figure 3-3 which shows 

95 percent confidence intervals for a cumulative distribution function, 

assuming 100 and 1,000 components. 

3.3.3 Leak/No-Leak Approach 

The leak/no-leak approach to estimating emission factors, as presented 

in the AID, is an extension of the complicated process described above. The 

expanded process considers a leak rate/screening value correlation 

integrated over a continuous distribution function; the leak/no-leak 

approach instead assumes only two emission rates and two populations: 

sources that "leak" (with screening values greater than or equal to 

. 3-17 
I 

CO 

M 

3 

Mi 

Mi 

Mi 

Mi 

2 

3 

a 

»— 

a Perctnt 

100 

90 

80 

70 

60 

SO 

40 

30 

20 

10 

0 

-i~iVC_!*f'—_Z__^~_T— __. 

————— Estlntad Par-cant of \ ». \ \ 

Total Mats Eaissions \ \ N \ 

— \ '* \\ .  — —-90 X Confidence Intarval

 N \ \ x x 

for ParcanC of Eaissions v N 

froa Total Population of \ \ \\ \ 

Valval (n - «) 

•90t Confidence Interval 

for Porcant of Eaissions 

In a (Uitdoa Ser_plt of 

1000 Valval 

- — - — 90% Confldanca Intarval for 

Percent of Eaissions in a 

Randaa Saaple of 100 Val vas 

\ \ \ 

\ 

\ 

V 

\ 

• • ' 1

 ' • • • < _L 

I 2 34 5 10 SO 100 1000 10.000 100.000 1.000.000 

Screening Value (ppav) (Loq1Q Scale) 

Figure 3-3. Cumulative Distribution of Total Emissions by Screening Values 

Comparison of Confidence Intervals . 
10,000 ppmv) and sources that do not leak (with screening values less than 

10,000 ppmv). 

The basis of this extension is as follows: when a group of sources 

"leak" (i.e., have a screening value > 10,000 ppmv),.they leak at a certain 

mass emission rate dn, the average. Similarly, as a group, sources screened 

at less than 10,000 ppmv (i.e., non-leaking sources) have on the average a 

certain mass emission rate associated with them. Thus, the overall average 

emission factor for a population of emission sources consists of two 

components: leaking source emissions and non-leaking source emissions. 

It is important to remember that fugitive emissions are found 

distributed over a wide range of screening values. Mass emissions associated 

with fugitive emission sources are similarly distributed. Therefore, only 

emission factors generated using distribution data can be used in estimating 

emissions from equipment leaks. Finally, only those emission factors 

generated in such a manner can be used in the extended procedure discussed 

below. 

3.3.3.1 Generation of Leaking and Nonleaking Emission Factors. 

Leaking and non-leaking emission factors are generated using three data: 

(1) the average emission factor, (2) the'leak frequency associated with the 

average emission factor, and (3) the percent of mass emissions associated 

with leaking sources. As an example, consider the data for light liquid 

valves in the Refining Assessment Study: 

Average Emission Factor 0.0109 kg/hr/source 

Leak Frequency 11% 

Percent of Mass Emissions, Leakers 86% 

Assuming 1,000 valves, the total mass emissions would be 10.9 kg/hr; and 

110 valves of the total 1,000 would account for 86 percent of the mass 

emissions, or 9.37 kg/hr. Since this amount of emissions would be shared, 

on the average, by all leaking valves, the individual leaking emission 

factor would be (9.37 kg/hr)/(110 valves) or 0.0852 kg/hr/source. The 

non-leaking emission factor is similarly computed. For this example, 890 

valves that are "non-leaking" account for only 14 percent of the total 

3-19 

y U 
P.57 

emissions, or 1.53 kg/hr. This yields an average nonleaking emission factor 

of (1.53 kg/hr)/(890 valves) or 0.00171 kg/hr/source. 

Put in more general terms, the emission factors for leaking sources 

(LEF) and the emission factors for nonleaking sources (NLEF) were computed 

according to the following equations: 

LEF ° OEF * PCM and NLEF = OEF « flOO-PCM) 

PCL (100 - PCL) 

where: LEF •**- emission factor for leaking sources 

NLEF ° emission factor for nonleaking sources 

OEF ° overall average emission factor 

PCM = percent of mass emissions due to leaking sources 

PCL •**• percent of sources found leaking 

The leaking and nonleaking emission factors generated by this procedure and 

presented in the AID are shown in Table 3-3. 

3.3.3.2 Computation of Average Emission Factors. Having computed 

leaking and nonleaking emission factors in 'the above manner, average 

emission factors can be determined by merely applying a leak frequency 

determined from field studies. Continuing with the example from above, the 

leak frequency for light liquid valves in SOCMI was found to be 6.5 percent 

on t_he. average (based on the 24-Unit Study). For 1,000 valves in light 

liquid service, an estimated 65 would leak at a rate, on the average, of 

0.0852 kg/hr/valve, or 5.5 kg/hr. The 935 valves predicted to be not 

leaking would account for an estimated 0.0017 kg/hr/valve, or 1.6 kg/hr. So 

all 1,000 valves in light liquid service would! have a predicted composite 

leak rate of 7.1 kg/hr, for an average emission factor of 

0.0071 kg/hr/source. This procedure, restated below 1n a more general form, 

can be applied to a population of sources to determine the average emission 

factor (AEF), provided the leak frequency of the population has been 

established. 

AEF ° LEF * PCL + NLEF « (100 - PCL) 

100 

3-20 
P.58 

./ 

-•FABLE 3-3. LEAKING AND NON-LEAKING EMISSION FACTORS FOR 

FUGITIVE EMISSIONS (kg/hr/source) 

Equipment 

Valves 

Pump Seals 

Compressor Seals 

Pressure Relief Valves 

Flanges 

Open-Ended Lines 

Service 

Gas 

LLb 

HLC 

LL 

HL 

Gas 

Gas 

-All 

All 

Leaking 

(>'10,000 ppm) 

Emission Factor 

0.0451a 

0.0852 

0.00023d 

0.437 

0.3885 

1.608 

1..691 

0.G375 

0.01195 ' 

Non-leaking 

(< 10,000 ppm) 

Emission Factor 

0.000483 

0.00171 

0.00023 

0.0120 

0.0135 

0.0894 

0.0447 

0.00006 

0.00150 

aThe leaking and non-leaking emission factors for valves in gas/vapor 

service are based upon the emission factors determined for gas valves in 

ethylene, cumene, and vinyl acetate units during the SOCMI Maintenance 

Study. 

LL - light liquid service. 

CHL - heavy liquid service. 

Leaking emission factor assumed equal to non-leaking emission factor since 

the computed leaking emission factor (0.00005 kg/hr/source) was less than 

non-leaking emission factor. . 
P.59 

3.4 EMISSION FACTORS PRESENTED IN THE AID 

Table 3-4 presents the results of this estimation process for the leak 

frequencies determined in the SOCMI 24-Unit Study. As the AID discussed, 

these leak frequencies were considered to be representative values for a 

cross-section of the large, diverse industry that is SOCMI. The average 

emission factors computed based on these leak frequencies were used to 

estimate emissions for the entire industry. As applied to the entire 

population of sources in the industry, these "typical" average emission 

factors were deemed appropriate for standards-setting activities. This was 

particularly true because they were applied consistently to different 

regulatory alternatives to arrive at comparisons. 

EPA considered the variability of leak frequency in the industry in 

developing its fugitive emission standards. The extension of the procedure 

for generating emission factors considers the "typical" average emission 

factor to be a function of leak frequency considered typical of the 

industry. Also, in evaluating valve standards for low leak-frequency plants, 

the technical analysis included emission factors that varied with leak 

frequency for valves. Results of this analysis provided support for the 

provision in the SOCMI standards allowing annual monitoring for process 

units with 2 percent or less valves leaking. 

The average emission factors given in Table 3-4 were derived in a 

straightforward manner using the leaking and non-leaking emission factors 

from the Refining Assessment Study (derived in the manner just discussed) 

and the leak frequencies from the SOCMI 24-Unit Study. There are two 

instances where this approach was not used, however. These two cases 

deserve specific mention. 

First, the emission factor for sampling connections is based on the 

amount of sample purge and not on a field-measured emission factor like 

other source types. In essence, a sampling connection is considered either 

"uncontrolled" (that is, the sample purge was assumed drained to the 

environment) or "controlled" with the sample purge collected and returned to 

the process line or disposed of properly. The actual value used for.the 

emission factor is based on the quantity of sampling purge reported for 

3-22 
P.60 

TABLE 3-4. AVERAGE EMISSION FACTORS FOR FUGITIVE EMISSIONS IN SOCMI' 

Equipment Component , 

"Average" SOCMI Factors 

kg/hr/source 

Pump Seals 

Light Liquid 

Heavy Liquid 

Valves 

Gas 

Light Liquid 

Heavy Liquid 

Compressor Seals 

Safety Relief Valves 

Flanges 

Open-Ended Lines 

Sampling Connections 

Gas 

0.0494 

0.0214 

0.0056 

0.0071 

0.00023 

0.228 

0.104 

0.00083 

0.0017 

0.0150 

3-23 
P.61 

25 

1,000 barrels of refining throughput and the average count of sampling 

connections reported for every 1,000 barrels of refining throughput 

capacity. The ratio of these two values yields an emission factor of. 

0.0150 kg/hr/source* It is important to emphasize that emissions from 

sampling connections do not include emissions through the seal or stem of 

the sampling valve. These emissions are considered part of the emissions 

from the valve and open-ended line categories. 

The second case worthy pf specific mention is the emission factor for 

valves in gas service. After computing average, emission factors using the 

Refining Assessment leaking and non-leaking emission factors, a comparison 

was made with the values determined for the three equipment types in 

ethylene, cumene, and vinyl acetate process units presented in the SOCMI 

Maintenance Study. From this comparison, the emission factor for gas valves 

calculated from the Refining Assessment data appeared different from the 

SOCMI values.. The four emission factors for gas valves determined for 

petroleum refining, ethylene units, cumene units, and vinyl acetate units 

were then compared visually as in Figure 3-4. The confidence intervals for 

the SOCMI gas valve emission factors are much-narrower than those for the 

refining emission factor. Furthermore, there is almost no overlap between 

the SOCMI confidence intervals and those for petroleum refining. This 

comparative analysis indicates that (1) the SOCMI gas valve factors are 

different from the factor for petroleum refining and (2) the SOCMI gas valve 

factors are better estimators of SOCMI gas valve emissions. 

As a result of this comparative analysis, new leaking and non-leaking 

emission factors for SOCMI gas valves were computed, based on data from the 

SOCMI Maintenance Program. The final values used in forming the average 

emission factor for SOCMI gas valves were: 

- 0.0451 kg/hr/leaking source and 

- 0.00048 kg/hr/nonleaking source. 

The factors for valves and pumps in light liquid service, shown in Figure 

3-5, were not found to be different. Therefore, the emission factors 

developed during the Refining Assessment Study (being based upon a more 

substantial data base) were used as the basis for leaking and non-leaking 

source emission factors. 

3-24 
P.62 

0.050 

0.040 .. 

u 

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o as 

(/> 

sn 

0.010 

Petroleum 

Refining 

Cumene 

Vinyl 

Acetate 

Ethylene 

15 

Leak Frequency (10,000 ppm), % 

Figure 3-4. Comparison of Emission Factors: Gas Valves. 

3-25 
92-e 

Emission Factor, kg/hr/source 

(952 confidance) 

o 

b 

3 

© 

b 

ro 

O 

o 

b 

s 

£ • : 

rs : 

3 

__ 

o 

b 

Emission Factor, kg/hr/scurce 

(95S confidence) 

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b 

o 

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P.64 

These "typical" average emission factors presented in Table 3-4 would 

also be appropriate for use in estimating emissions for process units where 

no additional data are available. Taken on an individual basis, the factors 

themselves represent a hypothetical "average", not necessarily any specific 

unit or process. Given data on a specific process unit, average emission 

factors could be generated using the procedure illustrated above for the 

average SOCMI factors. For example, assume a process unit has been surveyed 

for leaks (sources with screening values > 10,000 ppmv) and 4 percent of 

light liquid valves were determined to be leaking. Then an average emission 

factor for that unit could be computed as follows: 

AEF - 0.0852 * (0.04) + 0.0017 * (1 - 004) 

= 0.0051 kg/hr/source 

The concept of an emission factor that varies with leak frequency is 

also consistent with the data gathered during the SOCMI studies. Close 

examination of Figure 3-14 shows some relationship of leak frequency and 

average emission factor for gas valves in the three process units studied in 

the Maintenance Study. Furthermore, there is wide variation in process unit 

types across SOCMI, as evidenced in Table 3-5 by the variation in leak 

frequencies for the process units in the 24-Unit Study. The causes of such 

variation are many, but include chemicals processed, process parameters such 

as operating temperatures and pressures, and the safety and maintenance 

practices at a given site. 

3.5 EXAMPLE HYPOTHETICAL CASE 

In this section, an example of estimating emissions for a hypothetical 

chemical process unit will be considered. This case assumes that the 

process unit has been surveyed in accordance with Reference Method 21 and 

that the leak frequencies have been established. 

Table 3-6 shows this hypothetical process unit and a procedure for 

estimating emissions using data in this report. The first column presents 

3-27 

BUB 
P.65 

TABLE 3-5. LEAK FREQUENCIES BY PROCESS FOR EQUIPMENT IN 24 SOCMI UNITS12 

Process 

Vinyl Acetate 

Ethylene 

Cumene 

Acetone/Phenol 

Ethylene Dichloride 

Vinyl Chloride 

Formaldehyde 

Methyl Ethyl Ketone 

Acetaldehyde 

Methyl Methacrylate 

Adipic Acid 

Chlorinated Ethanes 

Acrylonitrile 

1,1,1-Trichloroethane 

0 

Valves, 

Gas 

3.7 

14.8 

14.1 

0 

1.0 

7.3 

2.4 

9.2 

4.5 

0 

0 

0 

2.3 

-

Percent 

Valves, 

Light Liquid 

0.4 

23.2 

10.5 

0.3 

1.1 

1.0 

0 

5.1 

0.5 

0.1 

0 

0.6 

0.9 

1.1 

L 

-

of Sources 

Pumps, 

ght Liquid 

4.5 

26.3 

16.0 

2.3 

5.2 

10.8 

0 

3.2 

9.4 

4.4 

-

8.3 

8.2 

10.0 

Leaking 

Flanges 

1.0 

5.7 

2.9 

0 

1.1 

3.2 

10.0 

0 

0 

0 

0 

0 

0.4 

0 

Open-Ended 

Lines 

3.7 

12.8 

9.1 

1.3 

2.8 

5.1 

0 

9.9 

5.7 

0.3 

0 

1.4 

2.7 

1.8 

3-28 
P.66 

TABLE 3-6. ESTIMATE OF "UNCONTROLLED" FUGITIVE EMISSIONS 

FOR A HYPOTHETICAL CASE 

Source 

Pump Seals 

Light Liquid 

Heavy Liquid 

Valves 

Gas/Vapor 

Light Liquid 

Heavy Liquid 

Pressure Relief Valves 

Gas/Vapor 

Open-Ended Lines 

Compressor Seals 

Sampling Connections 

Flanges 

Number 

Screened 

47 

3 

625 

1180 

64 

31 

278 

4 

70 

2880 

Number 

Leaking 

3 

1 

19 

13 

0 

1 

9 

0 

-

20 

Percent 

Leaking 

6.4 

33.3 

3-°c 

l.lc 

0 

3.2 

3.2 

0 

-

0.7 

Computed 

Emission Factor 

kg/hr/source 

0.0256 

0.1385 

0.0018 

0.0026 

0.00023 

0.0978 

0.0018" 

0.0894 

0.0150 

0.00032 

Annual 

Emissions 

Mg/yr 

10.5 

3.6 

9.9 

26.9 

0.1 

28.2 

4.1 

3.1 

9.2 

8.1 

aBased on values from Table 3-3, using AEF = (LEF * PCL + NLEF * (100-PCL))/100. 

Assumes 8,760 hours of operation annually. 

Composite percent leaking for valves is 1.8%. NOTE - In this case, valves would only 

need monitoring annually to ensure less than 2 percent leaking. 

3-29 
P.67 

the number of sources identified in the process unit for each source type. 

The second column shows the number of sources with screening values greater 

than or equal to 10,000 ppmv (I.e., leaking sources). The. resulting 

percentage of sources leaking is shown in the third column. The average 

emission factors for this hypothetical process unit can then be computed 

using the leaking and non-leaking emission factors found in Table 3-3. For 

example, 6.4 percent of pump seals in light liquid service were found to be 

leaking. Using the leak/no-leak approach, the unit-specific emission factor 

is estimated as: 

(0.437 kg/hr/source)(0.064) + (0.012 kg/hr/source)(1 - 0.064), 

or 0.0256 kg/hr/source. The total estimated emissions for pumps in light 

liquid service would then be computed by multiplying the unit-specific 

emission factor by the equipment count. The last column in Table 3-6 shows 

the results of this process for the hypothetical unit. 

A further extension of this procedure would be to examine the procedure 

to estimate the emission factor for a certain specie in the line. For 

example, consider this same hypothetical case,.where the light liquid pumped 

contained 20 percent of compound A. The compound A emission factor for 

light liquid pumps is easily computed by applying the weight percent (20 

percent in this case) to the emission factor generated above: 

(0.20)(0.0256 kg/hr/source) = 0.0051 kg/hr/source. 

Emission factors calculated in this manner could then be applied to the 

equipment counts (where the material in the process line contained 20 

percent of compound A) to estimate emissions of compound A. 

3-30 
4.0 EMISSION REDUCTION 

No single emission reduction technique can be used for all fugitive 

emission sources. The techniques applicable to fugitive emission sources 

range from equipment*to work practices. The various control techniques 

considered were described briefly in the earlier section on fugitive 

emission sources. They are covered in this section in the context of their 

emissions reduction potential. 

4.1 OVERVIEW OF TECHNIQUES 

The techniques used to control emissions from equipment leaks can be 

classified into two categories: equipment and work practices. An equipment 

control technique means that some piece of equipment is used to reduce or 

eliminate emissions. A common example is an add-on control device such as an 

incinerator that is used to reduce organic emissions from a process vent. 

For fugitive emission sources, equipment controls include: (1) leakless 

technology for valves and pumps; (2) plugs, caps, blinds, etc. for 

open-ended lines; (3) rupture disks and soft-se-ats (O-rings) for PRVs; (4) 

dual mechanical seals with non-VOC barrier fluid/degassing vent systems for 

rotary equipment; (5) closed loop sampling systems; and (6) enclosure of 

seal area/vent to a combustion control device for dynamic seals. These 

equipment control techniques can generally attain up to 100 percent 

reduction of emissions, depending upon the control efficiency of the control 

device. Mechanical seals and those techniques that rely upon a combustion 

control technique have been assigned an overall control efficiency of 95 

percent, which is consistent with the efficiency assigned to some typically 

applfed recovery techniques. 

The control techniques used for the largest number of fugitive emissionsources are work practices. The primary work practice applied to PRVs,. 

valves, pumps, and other sources is leak detection and repair of sources. 

4-1 
P.69 

4.2 LEAK DETECTION AND REPAIR (LDAR) 

The emissions reduction potential for LDAR as a control technique is 

highly variable depending upon several factors. The principal element 

impacting emissions reduction is the frequency of monitoring (surveying) 

sources for leak detection. For example, a monthly monitoring plan would 

typically be more effective in reducing emissions than a quarterly 

monitoring plan since leaks would be found and corrected more quickly. Some 

characteristics of individual sources also affect emissions reduction: 

leaking emission factor (as compared to the nonTeaking emission factor), 

leak occurrence rate, leak recurrence rate, and repair effectiveness. 

Gathering of these data for valves and pumps through extensive field testing 

was the focus of the SOCMI Maintenance Study. 

Using specific source characteristics, an evaluation of control 

effectiveness can be made for different monitoring plans using the LDAR 

27 Model. The model is a set of recursive equations that operates on an 

overall population of sources that can be segregated into the following 

subgroups for any given monitoring interval: (1) sources that leak due to 

the leak occurrence rate; (2) sources that leak*and cannot be repaired below 

the 10,000 ppmv leak definition; (3) sources that leaked, were repaired 

successfully, but leaked again soon after the repair (i.e., leak 

recurrence); and (4) sources that do not leak (i.e., those screening below 

the 10,000 ppmv leak definition). The relative numbers of sources in each 

subgroup change with each monitoring interval step, based on the 

characteristics for the sources. Figure 4-1 shows these subgroups and how 

they may interact according to the individual source characteristics. 

The LDAR Model also has the capability to examine complex monitoring 

plans such as the plan permitted by EPA under its fugitive emissions 

standard for valves in SOCMI. This plan allows quarterly monitoring of all 

valves, supplemented with monthly monitoring of those valves that leaked and 

were repaired. 

4-2. 
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Perhaps the best way to illustrate the LDAR Model is to present an 

example. The particular example considered here is the "typical" SOCMI unit 

presented ih the AID. Table 4-1 shows the inputs used in examining a LDAR. 

program for valves and pumps based on monthly monitoring. The input values 

were derived primarily from the SOCMI Maintenance Study. The selection of 

each input value is detailed in the AID. The LDAR Model used to estimate 

emissions reductions gives incremental results as well as results for a 

program that has been established. For the example, once a monthly 

monitoring plan is in place, emissions reductions of 73 percent and 59 

percent can be expected for valves in gas and light liquid services; 

likewise a 61 percent reduction in emissions can be achieved for pumps in 

light liquid service under a monthly LDAR plan. 

Table 4-2 presents the results of LDAR modeling published in the AID 

for valves and pumps in SOCMI. The table presents results for simple 

monthly, quarterly, semiannual, and annual monitoring of valves and pumps. 

Additionally, the monthly/quarterly hybrid program allowed by EPA for valves 

is shown. These results show that, as monitoring frequency, is increased, 

the anticipated emissions reduction increases. Further, the results 

indicate some instances where there is no positive effect in reducing 

emissions due to monitoring and repair on too infrequent a schedule. Such 

results, however, are subject to interpretation for specific cases since 

they are based on "average" input values for an entire industry. 

The ability to model the results of LDAR programs provided the means to 

examine alternative standards for valves. The LDAR Model was used to 

consider monthly LDAR programs for process units exhibiting low leak 

frequencies. With decreasing leak frequency, there is an associated decline 

in the average emission factor and emissions reduction. Coupling this 

information with the costs of the LDAR program, an analysis of the resultant 

cost effectiveness values led to the selection of 2 percent leaking as-the 

performance limit. Thus, process units with low Teak rates (and low leak 

frequencies) were given a special provision in the NSPS for SOCMI fugitive 

VOC emissions. 

4-4 
P.72 

TABLE 4-1. LDAR 

Input 

Emission factor, 

kg/hr/source 

Occurrence rate 

Initial leak 

frequency 

Fractional emission 

reduction from 

unsuccessful repair 

INPUTS AND COMPUTED REDUCTIONS 

» 

Description 

Initial average emission 

factor for all sources 

Fraction of nonleakers that 

became leakers over the " 

interval 

Fraction of sources leaking 

at initiation of LDAR program 

Reduction from sources not 

repaired below 10,000 ppmv 

FOR SOCMI/MONTHLY MONITORING 

Valves, 

Gas/Vapor 

0.0056 

0.013 

0.114 

0.63 

Valves, 

Light 

Liquid 

0.0071 

0.013 

0.065 

0.63 

Pumps, 

Light 

Liquid 

0.0494 

0.034 

0.088 

0 

Fractional emission 

reduction from 

successful repair 

Fraction of unsuccessful repairs 

Fraction of early 

failures 

Turnaround frequency, 

months 

Reduction from sources ; •.;.••:•:_• 0..9&--

<repaired below 10,000 ppmv 

Sources that leaked but * 0.10 

attempted repair below 

10,000 ppmv failed 

Sources repaired below 0.14 

10,000 ppmv but leaked 

within the next interval 

Period between plant 24 

shutdowns 

0.98 

0.10 

0.14 

24 

0.972 

24 

EMISSION REDUCTION COMPUTED: 0.73 0.59 0.608 

4-5 
P.73 

TABLE 4-2. LDAR MODEL RESULTS FOR SOCMI VALVES AND PUMPS 

0 

Monitoring Interval 

Monthly 

Monthly/Quarterly3 

Quarterly 

Semi-annual 

Annual 

Val ves, Gas 

0.73 

0.65 

0.64 

0.50 

0.24 

Source Tvoe 

Valves, 

Light Liquid 

0.59 

0.46 

0.44 

0.22 

(0.19) 

Pumps, 

Light Liquid 

0.61 

-

0.33 

(0.076) 

(0.80) 

aMonthly monitoring with quarterly monitoring of "low leak" components. 

NOTE: Numbers in parentheses indicate a negative control efficiency. Negative 

numbers are generated when the occurrence rate for the monitoring interval 

exceeds the initial leak frequency. Negative results are subject to interpretation and may not be meaningful. 

4-6 
P.74 

4.3 SUMMARY OF EMISSION REDUCTIONS 

Emissions reductions for fugitive emissions control techniques can be 

extremely variable, particularly for work practices like leak detection and 

repair programs. In terms of standard-setting activities, criteria for 

selection qf a given control technique or a particular level of control 

(eg., monitoring interval of a leak detection and repair program) can be 

quite different. For example, the criterion used in establishing the best 

demonstrated technology (BDT) for NSPS may not necessarily be equivalent to 

the choice in setting the reasonably available control technology (RACT) 

presented in control techniques guidelines (CTG) documents used by States. 

These two levels of control are compared in Table 4-3 for VOC equipment 

;leaks (fugitive emissions) from SOCMI; the associated control effectiveness 

values are also presented. " 4 

4-7 
TABLE 4-3. CONTROL LEVELS FOR SOCMI FUGITIVE EMISSIONS: NSPS AND CTG 

Source 

_£IS_ J4SES_ 

Control Technique 

Percent 

Control Control Technique 

Percent 

Control 

Pumps. Light Liquid Quarterly leak detection and repair 33 Monthly leak detection and repair 61 

Dual mechanical seal/heavy liquid 100 

barrier fluid 

Valves. Gas 

Light Liquid 

Quarterly leak detection and repair 64 Monthly leak detection and repair 73 

59 

Pressure Rellef 

Valves. Gas 

Open-Ended Lines 

Compressors 

Sampling Connections 

Quarterly leak detection and repair 

Plugs, caps, blinds, etc. 

Quarterly leak detection and repair 

— 

44 

100 

33 

-

Rupture disk, soft seats (O-rlngs). 100 

vent to control device 

Plugs, caps, blinds, etc. 100 

Seal enclosed/vented to control device 100 

Closed purge sampling 100 
5.0 LISTS OF REFERENCES 

1. U.S. Environmental Protection Agency. VOC Emissions in Synthetic Organic 

Chemicals Manufacturing Industry - Background Information for Promulgated 

Standards. Research Triangle Park, N.C. Publication No. 

EPA-450/3-80-033b. June 1982. 

0 ' 

2. Memo from Stelling, J.H.E., Radian Corporation, to SOCMI Docket. 

November 1, 1982. 10 p. Estimate of VOC Emissions from SOCMI. 

3. Honerkamp, R. L. and M. L. Schwendemen. (Radian Corporation.) 

Evaluation of Maintenance Effect on Fugitive Emissions for Refineries in 

the South Coast Air Quality Management district. (Prepared for U.S. 

Environmental Protection Agency.) Research Triangle Park, N.C. 

Publication No. EPA-600/7-82-049. June 1982. 

4. American Petroleum Institute. Guide for Pressure Relief and Depressuring 

Systems. API RP 521, First Edition. September 1969. 

5. Palmer, R. K. Hydrocarbon Losses, from Valves and Flanges. Joint 

District, Federal and State Project of the Evaluation of Refinery f 

Emissions'. ReportNe. 2. Hireh 1957. j 

:,e.. Steigefe^jferg^"JvVr^K^.-P9CJor£^UjLeafuL^'ia*-^ire^^Prros-aiHre:-" Relief Valvesv 

... Joint;.01 s!tWst* F<itfm?yc ai^ Sia ^ of Refinery 

. Emissions. Report' MJJTr Vtiip' 1957.7 ' • ;* 

Steigerwald, B. J. Emissions of Hydrocarbons to the Atmosphere from 

Seals on Pumps and Compressors. Joint District, Federal and State 

Project of the Evaluation of Refinery Emissions. Report No. 6. April 

1958. 

6. Wetherold, R.G., L.P. Provost, and CD . Smith. (Radian Corporation.) 

Assessment of Atmospheric Emissions from Petroleum Refining, 

(Prepared for U.S. Environmental Protection Agency.) Research Triangle 

Park, N.C. Publication No. EPA-600/2-80-075a-d. April 1980. 

7. U.S. Environmental Protection Agency. Fugitive Emission Sources of 

Organic Compounds - Additional Information on Emissions, Emission 

Reductions, and Costs. Research Triangle Park, N.C. Publication No. 

EPA-4S0/3-82-010. April 1982. 

8. Memo from Hustvedt, K.C , EPA:CPB, to Durham, J.F., EPA-.CPB. 

December 2, 1980. 170 p. MRC SOCMI Fugitive Testing. 

9. U.S. Environmental Protection Ageney. Air Pollution Emission Test at 

Dow Chemical Company. Research Triangle Park, N. C EMB Report 

No. 78-0CM-12C 

U.S. Environmental Protection Agency. Air Pollution Emission Test at 

Union Carbide Corporation. Research Triangle Park, N.C. EMB Report 

No. 78-0CM-12A. 

5-1 

E_______U 
J____Z_ 

U.S. Environmental Protection Agency. Air Pollution Emission Test at 

Stauffer Chemical Co. Research Triangle Park, N.C. EMB Report 

No. 78-0CM-12D. 

U.S. Environmental Protection Agency. Air Pollution Emission Test at 

Phillips Petroleum Co. Research Triangle Park, N.C. EMB Report 

No. 78-0CM-12E. . 

U.S. Environmental Protection Agency. Air Pollution Emission Test at 

Refinery E. Research Triangle Park, N.C. EMB Report No. 78-OCM-12F. 

10. Meeting Report. Honerkamp. R., Radian Corporation, to Hustvedt, K.C , 

EPA:CPB, and distribution list. June 12, 1979. 14 p. Minutes of 

meeting between EPA and DuPont representatives about fugitive emission 

sampling. 

11. Letter and attachment from Cox, J.B., Exxon Chemical Company, to 

Weber, B., EPA:CPB. February 21. 1978. 4 p. Copy of letter about 

cyclohexane unit fugitive loss data sent to Hydroscience. 

Letter and attachment from Cox, J.B., Exxon Chemical Company, to Walsh, 

R.T., EPA:CPB. March 21, 1979. 4 p. Information about cyclohexane 

unit. 

12. Blacksmith, J. R., et al. (Radian Corporation.) Problem-Oriented 

Report: Frequency of Leak Occurrence for Fittings in Synthetic Organic 

Chemical Plant Process Units. (Prepared for U.S. Environmental 

Protection Agency.) Research Triangle Park, N.C. Publication No. 

EPA-600/2-81-003. September 1980. 

13. Langley, G. J. and R. G. Wetherold. (Radian Corporation.) Evaluation of 

Maintenance for Fugitive VOC Emissions Control. (Prepared for U.S. 

Environmental Protection Agency.) Research Triangle Park, N.C. 

Publication No. EPA-600/52-81-080. May 1981. 

14. Langley, G. J. et al. (Radian Corporation.) Analysis of SOCMI VOC 

Fugitive Emissions Data. (Prepared for U.S. Environmental Protection 

Agency.) Research Triangle Park, N.C. Publication No. EPA-600/2-81-111. 

June 1981. 

15. Langley, G.J., and L.P. Provost. (Radian Corporation.) Revision of 

Emission Factors for Nonmethane Hydrocarbons from Valves and Pump Seals 

• in.SOCMI Processes. Technical Note. (Prepared for U.S. Environmental 

Protection Agency.) Research Triangle Park, N. C November 1981. 

16. Schwanecke, R. "Air Pollution Resulting from Leakage from Chemical 

Facilities." Luftverun-reinigung. 1970, pp.: 9-15. Translated for the 

U.S. Environmental Protection Agency by SCITRAN. Santa Barbara, 

California. 

5-2 
<*.*% 

P.78 

Kremer, H. "Leakages from Static and Dynamic Seals in Chemical and 

Petrochemical Plants." 4th Meeting OG EW/DGMK. Salzburg. October 1976. 

Translated for the U.S. Environmental Protection Agency by SCITRAN, Santa 

Barbara, California. 

Bierl, Alois, et al. "Leakage Rates of Sealing Elements." Chem. Ino. 

Tech. 49 (No. 2^ 1977, pp. 89-85. Translated for the U.S. Environmental 

Protection Agency by SCITRAN. Santa Barbara, California. 

Schwanecke, R. "Air Pollution Through Small Leakages for Equipn.e.il 

the Chemical Industry and Ways for Their Prevention." Translated for 

U.S. Environmental Protection Agency by SCITRAN. Santa Barbara, 

California. 

the 

17. 

18. 

19. 

20. 

21 

Lee, Kun - Chich, et al. (Union Carbide Corporation. South Charleston, 

West Virginia.) "A Fugitive Emission Study in a Petrochemical 

Manufacturing Unit." Presented at the 73rd Annual Meeting of the Air 

Pollution Control Association in Montreal, Quebec. June 22-27, 1980. 

Harvey, Cynthia M. and A. Carl Nelson. (PEDCo Environmental Inc.) 

Fugitive Emission Data - High Density Polyethylene Process Unit 

(Prepared for U.S. Environmental Protection Agency.) Research Xri 

Park, N. C Publication No.• EPA.-600/2-81-1O9-. June 

VOC 

DuBOM'i D.&.V:'tt ll 

Frequencies for Fittings in 

Protection Agency.) 

N.C. July 1982. 

O R .) Eiefssim Faetars--:tMr 

ants.. {?r%p&re<_ for U.S. Environasntal 

Mo. SO-FOL-1. Research Triangle Park, 

Wiesenborn, D.P., et al. (Radian Corporation.) Leak Frequency and 

Emission Factors for Fittings in Coke Oven By-Product Plants. (Prepared 

for U.S. Environmental Protection Agency.) EMB Report No. 81-BYC-12. 

Research Triangle Park, N. C January 1982. 

Wetherold, R. G., L. P. Provost, and C. D. Smith. (Radian Corporation.) 

Assessment of Atmospheric Emissions from Petroleum Refining, Appendix B: 

Detailed Results. (Prepared for U.S. Environmental Protection Agency.) 

Research Triangle Park, N.C. Publication No. EPA-600/2-80-075c. April 

1980. 

22. Reference 3. 

23. Eaton, W.S., et al. Fugitive Hydrocarbon Emissions from Petroleum 

Production Operations. American Petroleum Institute Publication 

No. 4322. 1980. 

24. Harris, G. E. (Radian Corporation.) Emission Test Report: Fugitive 

Test Report at the Gulf Venice Gas Plant, Volume I. (Prepared for U.S. 

Environmental Protection Agency.) Research Triangle Park, N.C. EMB 

Report No. 81-0SP-8. July 1981. 

5-3 

m n 
P.79 

«-fc: 

Harris, G. E. (Radian Corporation.) Emission Test Report: Fugitive VOC 

Testing at the Texas Paradis Gas Plant, Volume I. (Prepared for U.S. 

Environmental Protection Agency.) Research Triangle Park, N.C. EMB 

Report No. 80-0SP-7. July 1981. 

25. U.S. Environmental Protection Agency. Compilation of Air Pollutant 

Emission Factors. Research Triangle Park, N.C. AP-42. February 1980. 

26. Powell, D., et al. (PES, Inc.) Development of Petroleum Refinery Plot 

Plans. (Prepared for U.S. Environmental Protection Agency.) Research 

Triangle Park, N.C. Publication No. EPA-450/3-78-025. June 1978. 

27. Williamson, H. J., et al. (Radian Corporation.) Model for Evaluating 

the Effects of Leak Detection and Repair Programs on Fugitive Emissions. 

Technical Note DCN 81-290-403-06-05-03. September 1981. 

5-4 
4 ' * 

P.80 

TECHNICAL REPORT OATA 

(Please read Instructions on the reverse before completing) 

1. REPORT NO. 

EPA-450/3-86-002 

3. RECIPIENTS ACCESSION NO. 

4. TITLE ANO SUBTITLE 

Emission Factors for Equipment Leaks of VOC and HAP 

8. REPORT OATE 

February 10. 1986 

6. PERFORMING ORGANIZATION COOE 

7. AUTHOR(S) 

John H. E. Stelling III 

8. PERFORMING ORGANIZATION REPORT NO. 

DCN 86-203-024-63-06 

9. PERFORMING ORGANIZATION NAME ANO ADDRESS 

Radian Corporation 

3200 E. Chapel Hill Road/Nelson Highway 

Research Triangle Park, N.C. 27709 

10. PROGRAM ELEMENT NO. 

11. CONTRACT/GRANT NO. 

68-02-3889, WA 63 

12. SPONSORING AGENCY NAME ANO AOORESS 

U.S. Environmental Protection Agency 

Office of Air Quality Planning and Standards 

Emission Standards and Engineering Division 

Research Triangle Park, N.C. 27711 

13. TYPE OF REPORT AND PERIOD COVERED 

14. SPONSORING AGENCY COOE 

15. SUPPLEMENTARY NOTES 

Project Officer is Robert E. Rosensteel, Mail Drop. 13, (919) 541-5605. 

16. ABSTRACT 

..9 The report summarizes the development of emission factors for volatile orgpsfc 

compound (VOC) equipment leaks- The.-background information used in emissi-PJtJ*G&fe'--

development is reviewed. The. estimation techniques for generation of VOt emis si dinfactors are described and illustrated with an example. The application of the 

estimation techniques is demonstrated for both VOC and hazardous air pollutants 

(HAPs). 

17. KEY WORDS AND DOCUMENT ANALYSIS 

DESCRIPTORS b.lOENTlFIERS/OPEN ENOED TERMS c. COSATi Field/Group 

Fugitive Emissions 

Volatile Organic 

Compounds 

Hazardous Air Pollutants 

18. DISTRIBUTION STATEMENT 

Release to Public 

19. SECURITY CLASS (This Report) 

Unclassified 

21. NO. OF PAGES 

70 

20. SECURITY CLASS (This page I 

Unclassified 

22. PRICE 

EPA Form 2220-" (R»». 4-77) PREVIOU S EDITIO N IS OBSOLET E