United States       Industrial Environmental Research  EPA-600/2-79-044
Environmental Protection   Laboratory           February 1979
Agency         Research Triangle Park NC 27711
Research and Development	
Emission Factors and
Frequency of Leak
Occurrence for Fittings
in Refinery Process Units

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                 RESEARCH REPORTING SERIES


Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination  of  traditional grouping was consciously
planned to foster technology transfer and a maximum interface in  related fields.
The nine series are:

    1. Environmental Health Effects Research

    2. Environmental Protection Technology

    3. Ecological Research

    4. Environmental Monitoring

    5. Socioeconomic Environmental Studies

    6. Scientific and Technical Assessment Reports (STAR)

    7- Interagency Energy-Environment Research and Development

    8. "Special" Reports

    9. Miscellaneous Reports

This report has been assigned to the  ENVIRONMENTAL PROTECTION TECH-
NOLOGY  series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment,  and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
                        EPA REVIEW NOTICE
This report has been reviewed by the U.S. Environmental Protection Agency, and
approved for publication. Approval does not signify that the contents necessarily
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This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.

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                                    EPA-600/2-79-044

                                        February 1979
Emission Factors  and Frequency
 of Leak  Occurrence for  Fittings
     in  Refinery  Process  Units
                         by

                Robert Wetherold and Lloyd Provost

                    Radian Corporation
                      P.O. Box 9948
                    Austin, Texas 78766
              Contract Nos. 68-02-2147 and 68-02-2665
                  Program Element No. 1AB604
                 EPA Project Officer: Dale A. Denny

              Industrial Environmental Research Laboratory
               Office of Energy, Minerals, and Industry
                 Research Triangle Park, NC 27711
                      Prepared for

              U.S. ENVIRONMENTAL PROTECTION AGENCY
                Office of Research and Development
                   Washington, DC 20460

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                         TABLE OF CONTENTS
                                                             Page
List of Figures	     iv
List of Tables	     vii
Section 1 - Executive Summary 	      1
Section 2 - Introduction  	      4
Section 3 - Program Design and Source Selection 	      5
Section 4 - Results of Screening and Sampling
            Program	     11
Appendix A - Emission Factor Development - Statistical
             Considerations
References
                                 iii

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                              LIST OF FIGURES
Figure 4-1.    Nomograph for Predicting Total Nonmethane Hydrocarbon
               Leak Rates from Maximum Screening Values - Valves
               and Flanges - Gas/Vapor Streams - Part I	    13

Figure 4-2.    Nomograph for Predicting Total Nonmethane Hydrocarbon
               Leak Rates from Maximum Screening Values - Valves
               and Flanges - Gas/Vapor Streams - Part II	    14

Figure 4-3.    Nomograph for Predicting Total Nonmethane Hydrocarbon
               Leak Rates from Maximum Screening Values - Valves
               and Flanges -Light Liquid/Two-Phase and Heavy
               Liquid Streams Part I	    15

Figure 4-4.    Nomograph for Predicting Total Nonmethane Hydrocarbon
               Leak Rates from Maximum Screening Values - Valves
               and Flanges - Light Liquid/Two-Phase and Heavy Liquid
               Streams Part II	    16

Figure 4-5.    Nomograph for Predicting Total Nonmethane Hydrocarbon
               Leak Rates from Maximum Screening Values - Pumps, Com-
               pressors, Drains, Relief Valves - Part I	    17

Figure 4-6.    Nomograph for Predicting Total Nonmethane Hydrocarbon
               Leak Rates from Maximum Screening Values - Pumps, Com-
               pressors, Drains, Relief Valves - Part II	    18

Figure 4-7A.   Cumulative Distribution of Total Emissions by Screening
               Values - Valves - Gas/Vapor Streams 	    28

Figure 4-7B.   Cumulative Distribution of Sources by  Screening  Values  -
               Valves - Gas/Vapor Streams 	    29

Figure 4-8A.   Cumulative Distribution of Total Emissions by Screening
               Values - Valves - Light Liquid/Two-Phase Streams ...    30

Figure 4-8B.   Cumulative Distribution of Sources by  Screening  Values  -
               Valves - Light Liquid/Two-Phase Streams	    31

Figure 4-9A.   Cumulative Distribution of Total Emissions by Screening
               Values - Valves - Heavy Liquid Streams 	    32

Figure 4-9B.   Cumulative Distribution of Sources by  Screening  Values  -
               Valves - Heavy Liquid Streams	    33
                                    iv

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                                                                       Page

Figure 4-10A.  Cumulative Distribution of Total Emissions by Screening
               Values - Pump Seals - Light Liquid Streams 	  34

Figure 4-10B.  Cumulative Distribution of Sources by Screening Values -
               Pump Seals - Light Liquid Streams	  35

Figure 4-11A.  Cumulative Distribution of Total Emissions by Screening
               Values - Pump Seals - Heavy Liquid Streams 	  36

Figure 4-11B.  Cumulative Distribution of Sources by Screening Values -
               Pump Seals - Heavy Liquid Streams	  37

Figure 4-12A.  Cumulative Distribution of Total Emissions by Screening
               Values - Compressor Seals - Hydrocarbon Service	38

Figure 4-12B.  Cumulative Distribution of Sources by Screening Values -
               Compressor Seals - Hydrocarbon Service 	  39

Figure 4-13A.  Cumulative Distribution of Total Emissions by Screening
               Values - Compressor Seals - Hydrogen Service 	  40

Figure 4-13B.  Cumulative Distribution of Sources by Screening Values -
               Compressor Seals - Hydrogen Service	41

Figure 4-14A.  Cumulative Distribution of To'tal Emissions by Screening
               Values - Flanges	42

Figure 4-14B.  Cumulative Distribution of Sources by Screening Values -
               Flanges	43

Figure 4-15A.  Cumulative Distribution of Total Emissions by Screening
               Values - Drains	44

Figure 4-15B.  Cumulative Distribution of Sources by Screening Values -
               Drains	45

Figure 4-16A.  Cumulative Distribution of Total Emissions by Screening
               Values - Relief Valves 	  46

Figure 4-16B.  Cumulative Distribution of Sources by Screening Values -
               Relief Valves	47

Figure A-l.    Valves and Flanges - Leak Rate/Screening Relationship -
               Gas/Vapor Streams	A-9

Figure A-2.    Valves and Flanges - Leak Rate/Screening Relationship -
               Light Liquid/Two-Phase and Heavy Liquid Streams.  .  .  .  A-10

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Figure A-3.    Pumps, Compressors, Drains, Relief Valves - Leak vs
               Screening - All Process Streams	A-ll

Figure A-4.    Distribution of Logio (Max Screening Value)_Valves -
               Gas/Vapor Streams  	 A-13

Figure A-5.    Cumulative Distribution of Total Emissions by Screening
               Values - Valves - Light Liquid/Two-Phase Streams -
               Comparison of Confidence Intervals 	 A-17

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                               LIST OF TABLES
                                                                       Page
Table 1-1.   Estimated Vapor Emission Factors for
             Nonmethane Hydrocarbons from Selected
             Sources 	     2

Table 3-1.   Process Units Sampled in Nine Refineries  	     6

Table 3-2.   Range of Choice Variables for Screened
             Baggable Sources  	     7

Table 3-3.   Process Stream Classification by Group	     9

Table 4-1.   Confidence Intervals for Mean and
             Individual Leak Rates - Valves and Flanges -
             Gas/Vapor Streams 	     19

             Confidence Intervals for Mean and
             Individual Leak Rates - Valves and Flanges - Light
             Liquid/Two-Phase and Heavy Liquid Streams 	     20

             Confidence Intervals for Mean and
             Individual Leak Rates - Pump Seals, Compressor
             Seals, Drains, Relief Valves - All Process
             Stream Types  	     21

Table 4-2.   Summary Statistics and Estimated Vapor
             Emission Factors for Nonmethane Hydrocarbons
             from Baggable Sources 	     22

Table 4-3.   Hypothetical Refinery - Based on ADL Texas
             Gulf Cluster Model (330,000 BPCD) 	     25

Table 4-4.   Distribution of Measured Leak
             Rates	     26

Table 4-5.   Percent of Total Mass Emissions Released
             by the Upper Ten Percent of Screened
             Sources	     49

Table A-l.   Prediction Equations for Nonmethane Leak Rates
             Based on Maximum TLV Screening or Rescreening
             Values	    A-2
                                     vii

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                                  SECTION 1

                              EXECUTIVE SUMMARY
     For the past three years, the Environmental Protection Agency has been
sponsoring a petroleum refinery assessment program.  As part of this program,
fugitive hydrocarbon emissions have been measured from a number of types of
sources in refineries.  This report has been prepared to distribute some of
the data and results obtained thus far in the program.  These data should
prove to be of value in the development of state and federal regulations in-
volving fugitive hydrocarbon emissions from sources in petroleum refineries.

     The results presented in this report have been developed from data ob-
tained at nine refineries throughout the country.  The data for compressor
seals and relief valves represent thirteen refineries.  A wide variety of
equipment, process units, and crude oils were included in this study.  In
this report, the nonmethane hydrocarbon emissions from selected fugitive
sources are described.  These sources include valves, flanges, pump seals,
compressor seals, relief valves, and process drains.

     At each refinery, random sample sets of each type of source were selec-
ted, "screened", and if necessary, sampled.  The "screening" of sources was
accomplished with portable hydrocarbon detectors.  The "screening values"
were defined as the maximum hydrocarbon concentrations detected at the sel-
ected source.  Extensive data were taken for each of the selected sources.

     One of the important results of this study has been the establishment
of relationships between the screening values and the measured leak rates of
'the various sources.  Nomographs were developed which relate the predicted
mean leak rates to the maximum screening values for the various source types.
Confidence intervals for the true mean leak rate are included in the nomo-
graphs .

     The emission factors for nonmethane hydrocarbon emissions from selected
types of sources were developed.  These emission factors are summarized in
Table 1-1.  A very high correlation was found between mass emission rates
from sources and the -type of stream service in which' the sources were em-"
ployed.   Except for compressed gases, streams were classified into one of
three"stream groups; (1) gas/vapor streams (2) light liquid/two-phase streams,
and (3)  kerosene and heavier liquid streams.  Gases passing through compressors
were classified as either hydrogen or hydrocarbon service.  It was found that
sources in gas/vapor stream service had higher emission rates than those
sources in heavier stream service.  This trend was especially pronounced for
valves and pump seals.  Overall emission factors for these two sources are
not presented.  The distribution of valves and pump seals within the three
stream groups must be known or estimated to develop applicable overall pro-
cess unit and refinery emission factors for these two source types.

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TABLE 1-1.   ESTIMATED VAPOR EMISSION FACTORS FOR NONMETHANE EYDROCARBONS  FROM SELECTED SOURCES
ESTIMATED
PERCENT
SOURCE TYPE LEAKING
VALVES
Gas/Vapor Streams 29.3
Light Liquid/Two-Phase Streams 36.5
Heavy Liquid Streams 6.7
FLANGES 3.1
PUMP SEALS
Light Liquid Streams 63.8
Heavy Liquid Streams 22.6
COMPRESSOR SEALS
Hydrocarbon Service 70.3
Hydrogen Service 81.2
DRAINS 19.2
RELIEF VALVES 39.2
95% CONFIDENCE
INTERVAL FOR PERCENT
LEAKING

(25.9
(33.6
( 4.6
( 2.2

(58.9
(17.1

(62.9
(71.2
(14. f,
(25.1

, 32.7)
, 39.5)
, 8.9)
, 3.9)

, 68.8)
, 28.1)

, 77.7)
, 88.8)
, 24.0)
, 40.6)
EMISSION 95% CONFIDENCE
FACTOR INTERVAL FOR
ESTIMATE EMISSION FACTOR
(Ib/hr - Source) (Ib/hr - Source)

0.047 (0.027
0.023 (0.016
0.0007 (0.0002
0.00058 (0.0002

0.26 (0.17
0.045 (0.02

0.98 (0.46
0.10 (0.04
0.070 (0.02
0.19 (0.07

, 0.084)
, 0.034)
, 0.002)
, 0.001)

, 0.39)
, 0.11)

, 2.0)
, 0.24)
, n..?0)
, 0.52)
    'Leaking sources in this report are defined as sources with screening values
     >_200 ppmv or sources with measured leak rates greater than 0.00001 Ibs/hr.

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     Emission factors are given for compressor seals in each of the two gas
service classifications.  The number of seals in each type of service must
be known to develop overall process unit or refinery emissions.

     Valves, because of their number and relatively high emission factor are
the major emission source among the source types discussed in this report.
This conclusion is based on an analysis of a hypothetical refinery coupled
with the emission rates developed herein.

     Nomographs have also been prepared which relate the maximum screening
values to the percentage of sources leaking and to the percentage of total
emissions represented by these leaking sources.  These nomographs can be
used to predict the potential maximum* reduction of emissions due to mainte-
nance programs.  Data have been collected at four additional refineries to
determine the effectiveness of maintenance in reducing fugitive emissions.
These data  are not discussed  in this report, but will be available in the
final report for this program.
 * Maximum,  because  the  percentages  from  the nomographs can only be eliminated
  if maintenance will result  in zero  emissions  for any given source.

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                                  SECTION 2

                                INTRODUCTION
     Because of the amount of current activity in the development of state
and federal regulations involving fugitive hydrocarbon emissions from refining
activities, it is imperative to place available current data in the hands of
all concerned parties.

     This report has been prepared solely for the purpose of distribution of
data.  For that reason, only minimal detail has been provided on the experi-
mental and computational aspects of the program.  The discussion of the data
is also brief pending the development of complete sets of all correlation
factors.

     The emission factors presented in this report are completely general
(i.e., they are neither region nor refinery specific), and for that reason,
they have a wider applicability than previously generated data.

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                                   SECTION 3

                      PROGRAM DESIGN AND SOURCE SELECTION


      The results presented in this report have been developed from data
 taken primarily at nine refineries.  Data for compressors and relief  valves
 were also obtained at four additional refineries.   The refineries  were lo-
 cated in major refining areas throughout the country.   Large, small,  new and
 old refineries were sampled.  Thus, a wide variety of  equipment, process
 units, and crude oils were included in this study.

      All of the major refinery processing units were studied in this  program.
 In each refinery, sources in six to nine refinery units were selected for
 study.  The number of each type of process unit sampled are presented in Table
 3-1.

      In this report, the emissions from "baggable" sources are presented.
 Baggable sources are those that can be completely enclosed to measure their
 emission rates.  Included in this catagory are valves, flanges,  pump  seals,
 compressor seals, relief valves, and process drains.

      Variables which might affect the fugitive emissions from baggable
 sources were classified as either choice or correlating parameters.   A choice
 parameter is defined as a variable that may directly affect fugitive  emission.0
 and is used in selecting the source distribution.   These choice parameters
 for the five types of baggable sources are listed in Table 3-2.

      All other variables which might affect the level of fugitive  emissions
 are considered as correlating parameters.  Jhe^v^ues^f__aii^BeIect.ed cor-
 relatj.ng variables._,ar^_r_ecorded__for each selected source.  The number of
'correlating parameters ranges from 17 for pumps to 2 for drains.

      Obtaining a statistically significant sample population for all  com-
 binations of even the choice variables~wbuld require a prohibitively  large
 number of samples.  Therefore, a sampling plan was devised that  required a
 minimum number of measurements to determine leak rates within the  desired
 accuracies.  By assuming that interactions between the variables were un-
 Impdrtant~7~the number of necessary measurements were reduced.  A factorial
 experimental design procedure was used to select combinations of the  vari-
 ables so that the relationship of each variable with the leak rates could be
 determined.  Regression analysis and analysis of variance were used to deter-
 mine which vaTiabT^^r"^signiTicantTy7ferated to the_ leakage.  The sampling
 ""plans for~suceessive selected refineries were adjusted according to the re-
 sults from the refineries that had been sampled previously.

      The distribution of selected sources in the first six refineries en-
 compassed the full range of choice and correlating variables.  One of the
 most important of the correlating parameters is the type ofjyrpcess stream
 associated with each of the various selected source types.  Hydrocarbon

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           TABLE 3-1.  PROCESS UNITS SAMPLED IN NINE REFINERIES
                                                         NUMBER OF
  REFINERY PROCESS  UNIT                                  SAMPLED UNITS
Atmospheric Distillation                                     7
Vacuum Distillation                                          4
Thermal Operations (Coking)                                  2
Catalytic Cracking                                           5
Catalytic Reforming                                          6
Catalytic Hydrocracking                                      2
Catalytic Hydrorefining                                      2
Catalytic Hydrotreating                                      7
Alkylation                                                   6
Aromatics/Isomerization                                      3
Lube Oil Manufacture                                         2
Asphalt Manufacture                                          1
Fuel Gas/Light-Ends Processing                              11
LPG                                                          2
Sulfur Recovery                                              1
Other                                                        3

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    TABLE 3-2.  RANGE OF CHOICE VARIABLES FOR SCREENED BAGGABLE SOURCES
 BAGGABLE SOURCE
 CHOICE VARIABLE
     VARIABLE RANGES
   FOR SCREENED SOURCES
Valves
Flanges
Pump Seals
Compressor  Seals
Drains

Relief Valves
Pressure
Temperature
Fluid State
Service
Function
Size

Pressure
Temperature
Fluid State
Service

Size

Pressure
Temperature
Capacity
Shaft Motion
Seal Type
Liquid RVP

Pressure
Temperature
Capacity
Shaft Motion
Seal Type
Lubrication Method

Service

Pressure
Temperature
Fluid State
-10 - 3000 psig
-190 - 925°F
Gas, Liquid, Two-Phase
In-line,  Open-ended
Block, Throttling, Control
0.5 - 36 inches

-14 - 3000 psig
-30 - 950°F
Gas, Liquid, Two-Phase
Pipe, Exchanger, Vessel,
  Orifice
1-54 inches

0 - 3090 psig
0 - 800°F
0 - 100,000 gpm
Centrifugal, Reciprocating
Mechanical Seal, Packed Seal
Complete range

0 - 3000 psig
40 - 300°F
0.06 - 66.0 MMSCFD
Centrifugal, Reciprocating
Packed, Labyrinth, Mechanical
Hydrocarbon lubricant

Active, Wash-up

0 - 1350 psig
40 - 1100°F
Gas, Liquid

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stream groups were developed, and all process streams were placed in one of
these classifications.  Three major stream groups were defined.  The three
groups and the descriptions of the streams within each group are shown in
Table 3-3.  The "Gas/Vapor" group contains those hydrocarbon streams which
were completely vaporized at the process conditions.  Light hydrocarbon
liquids and two-phase streams are included in the "Light Liquid/Two-Phase"
group.  The "Heavy Liquids" group contains those streams which consist primari-
ly of kerosene and heavier hydrocarbon  liquids.  Compressor seal emissions do not
vary according to these three process streams,  instead the emissions are bro-
ken down by a) hydrocarbon service and  b) hydrogen  service.  The stream group
is determined by the most volatile stream component present in a concentra-
tion of 20% or more.

     The approximate numbers of each type of source selected for study and
testing in each refinery were:

                       valves                       250-300

                       flanges                      100-750

                       pump seals                   100-125

                       compressor seals            10- 20

                       drains                       20- 40

                       relief valves                20- 40

 There were normally 500-600  sources  studied  in  each refinery.

      The  distribution of  sources  among  the process  units was determined be-
 fore the  selection and testing  of individual sources was begun.  Individual
 sources were selected from piping,  instrumentation  and process flow diagrams
 before a  refinery processing  area was entered.  Only those preselected sources
 were screened.   In this way,  bias based on observation of individual sources
 was eliminated,  and an approximate  random sample set within the required
 source distribution was  achieved.

      The  screening of sources was accomplished  with sensitive portable hydro-
 carbon detectors.   The principal  device used in this study was the  J. W.
 Bacharach Instrument Co.  "TLV Sniffer". The Century Instrument Co. Organic
 Vapor Analyzer (Model OVA-108)  was  used for  some screening, but these values
 were not  included in the correlation calculations which follow.  The instru-
 ments were calibrated with standard mixtures of hexane in air.  The OVA-108
 and TLV Sniffer give direct  readings of hydrocarbon concentrations  in ppm by
 volume.  In this report,  the terms  "screening values" and "TLV screening
 values" refer to the maximum hydrocarbon concentration detected at  selected
 baggable  sources.

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            TABLE  3-3.  PROCESS  STREAM CLASSIFICATION BY GROUP
  STREAM GROUP
              i
 Gas/Vapor
 Light  Liquids/Two-Phase.
  Heavy Liquids
HYDROCARBON  STREAM DESCRIPTION2

Ci-C2 Hydrocarbons
Ca-Cit Hydrocarbons
Cs-Ca Hydrocarbons
GIO+ Hydrocarbons
Mixed Molecular Weight Hydrocarbon
      Streams
Aromatic Hydrocarbons
Miscellaneous Organic Compounds
Hydrocarbon Streams Containing Ha,
      and H20
Cz Hydrocarbons
Cs-Cij Hydrocarbons
C5-C6 Hydrocarbons
Cy-Cg Hydrocarbons
Naphtha
Light Distillate
Aromatic Hydrocarbons (low molecular
      weight)
Miscellaneous Streams

Kerosene, Diesel, Heating Oil
Gas Oils
Atmospheric Resid/Vacuum Gas Oil
Vacuum Resid/Asphalt
Aromat ics /Polymer s
Mixed Molecular Weight Streams
Non-distillate Solvents
Miscellaneous Organic Streams
'stream group is determined by the stream conditions within the process lines

LThe most volatile stream component present at a  concentration  of 20% or more
 dete
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     When screening valves, pumps or compressors, the probe of the hydro-
carbon detector was normally placed as close as possible to the intersection
of the shaft with the sealing device (0 cm).  The probe was held at this
location for a minimum of five seconds.  The detector reading was recorded.
This was repeated at three other points 90° apart around the shaft.  The
maximum reading was used as the sampling criterion.

     Flanges were screened by placing the detector probe at 2-inch intervals
all around and right against the outside perimeter of the flange interface.
The maximum detector reading was recorded.  Drains were similarly screened.
The detector probe was placed at 2-inch intervals around the perimeter of the
drain.  The maximum measured hydrocarbon concentration was recorded.

     Relief valves were screened by placing the instrument probe at the valve
"horn" exit.  The screening value obtained at that point was used as the
sampling criterion.

     The values of all choice variables and correlating parameters were re-
corded at the time of screening.  The leak rates from sources with screening
values below 200 ppmv hydrocarbon were considered to be negligible.  All
sources with screening values of 200 ppmv or greater were candidate sources
for sampling to measure their leak rates.  Time and equipment constraints pre-
vented all candidate sources from being sampled; emissions from the candidate
sources which were not sampled were estimated as described in Appendix A.
At the time of sampling, all sources were rescreened.  Values of the recorded
source data were checked and, if necessary, changed to conform to the
conditions existing at the time of sampling.
                                    10

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                                  SECTION 4

                  RESULTS OF SCREENING AND SAMPLING PROGRAM


     The results of this program are summarized in this section of the re-
port.  The screening results are described and interpreted.  The frequency
of leaks from the various baggable sources are presented.  The emission fac-
tors which were developed from the sampling results are given.

Relationships Between Screening Readings and Nonmethane Leak Rates

     One of the important results of this study has been the establishment
of relationships between concentrations obtained using portable hydrocarbon
detection devices and measured leak rates.  The use of these portable de-
vices to estimate leak rates has potential for refinery maintenance programs,
as well as in determining total leak rates for regulatory purposes.  The
data analyzed in this section were obtained primarily using a J.W. Bacharach
"TLV Sniffer" calibrated to hexane (by volume).  Another portable device,
the Century Instrument Company's Organic Vapor Analyzer (Model OVA-108), was
also used and evaluated.  The OVA-108 screening values were found to have
similar, but not identical, correlations with leak rates.  Most readings
were obtained by placing the detector probe directly on the sources.  How-
ever, for evaluation purposes, some readings were also obtained five centi-
meters from the source.  It is possible to relate the various kinds of
screening values to one another.  For this report, however, the correlations
are based on "TLV Sniffer" readings at the source.

     Screening values were obtained when the source was first located, and
rescreening values were taken at the time each source was sampled.  The  re-
screening values are generally more highly correlated with leak rates than
are the original screening results.  For example, the correlation coefficient
for the correlation of maximum screening (original) values with nonmethane
hydrocarbon leak rates of valves is 0.63.  A correlation coefficient of  0.72
is obtained when the maximum rescreening values are correlated with non-
methane hydrocarbon leak rates of valves.

     Appendix A contains detailed descriptions of the statistical procedures
used to develop the results presented in this report.  The least-square
linear regression equations developed for predicting leak rates from un-
sampled sources in the data base are described.  For potential prediction
purposes outside this data base, a statistical analysis of covariance was
done to determine whether different linear equations are required for each
baggable source and stream type.  The results of this analysis are presented
in Appendix A.  It was found that the source and stream types could be
grouped such that three equations were adequate for predicting leak rates
from screened sources.  The three groups are as follows:
                                    11

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     •  Valves and Flanges - Gas/Vapor Streams

     •  Valves and Flanges - Light Liquid/Two-phase and Heavy Liquid Streams

     •  Pump Seals, Compressor Seals, Drains, Relief Valves

     The equations were used to develop nomographs which relate the predicted
leak rate and maximum screening values for the various source and stream
types.  These nomographs are presented in Figures 4-1 through 4-6.

     Each nomograph gives the predicted mean leak rate for different values
of maximum TLV screening readings taken directly on the source of the leak.
Ninety percent confidence intervals for the true mean leak rate are also
given.  These confidence limits are for the mean leak rate and should not be
confused with confidence intervals for individual leak rates for given
screening values.  Table 4-1 compares the 90% confidence intervals for the
mean leak rate and the 90% confidence intervals for individual leaks for
selected screening values.

Emission Factors and Frequency of Leaks

     The estimated emission factors for nonmethane hydrocarbon emissions from
six types of sources are summarized in Table 4-2.   Overall emission factors,
as well as factors for sources in different process stream services,  are in-
cluded.  The process stream breakdown for flanges,  drains and relief valves
are included for information purposes.  Summary statistics are tabulated for
each source type.  These include (1)  95% confidence intervals for both the
emission factors and for percent of leaking sources,  (2)  percentile for in-
dividual leaks, and (3) emission factor percentile.   The  95% confidence inter-
val is the interval or range of values expected to  include the true emission
factor or true percent of leaking sources,  with 95% confidence.   For example,
the true emission factor for relief valves  (if all  relief valves could be
sampled and averaged) should be between 0.06 and 0.52 Ib/hr.

     If a random selection of sources are sampled and ranked according to
their emission rates, the range of emission rates excluding the  first 1% and
last 1% of the sampled sources is the expected range of leak rates (1st and
99th).  As an example, the 1% of relief valves with the lowest emission rates
would emit nothing.  The 1% of relief valves with the highest emission rates
are expected to emit more than 4.9 Ib/hr from each valve.   Therefore,  98% of
all relief valves would be expected to have leak rates between zero and 4.9
Ib/hr.

     The population percentile for emission factors represents the leak rate
percentile at which the emission factor is  expected to be located in a ran-
dom sample of a particular source type.  For instance, the percentile for
relief valves is 91.9 which means that one  could expect about 92% of  the leak
rates from relief valves to be less than the emission factor of  0.19  Ib/hr.
About 8% of the relief valve leaks could be expected to be greater than the
emission factor.  The fact that most of the emission factor percentiles are
                                    12

-------
                     (Part I:  Screening Values  from  0-10,000 ppm)
W
H
O


1
f-J
B
H
U
H

R
        0.05 -
        0.04
        0.03
        0.02
0.01
                                                         Upper Limit of 90S Confidence

                                                       / Interval  for Mean
                                                        Mean
                                                         Lower Limit of 90S Confidence

                                                      /Interval  for Mean
           Equation for Predicted Mean Ling:


           NM Leak Rate * 8.59  do'7) (Max Screening)1"16

           I past. Squares Equation IKpri to Develop Chart;


           Log(NM Leak)= -7.00  + 1.16 Log  (Max Screening)


           Correlation Coefficient • 0.71

           Standard Error = 0.91 Log(Leak Rate)

           Number of Data Pairs = 106

           Scale Bias Correction Factor = 8.59
                   2000
                    4000
6000
3000    10,000
                               Maximum Screening Value (ppmv as Hexane)

                         Using J.  W. Bacharach TLV Sniffer at the Source.
       Figure 4-1.   Valves  and  Flanges  - Gas/Vapor Streams -  Part  I


                       Nomograph for Predicting Total Nonmethane Hydrocarbon

                       Leak Rates  from Maximum Screening Values
                                               13

-------
w
I
25
O
CJ
o
Pi
w
g
H
O
M


I
Pi
          0.9
          0.3
           0.7
           0.6
0.5
           0.4
           0.3
0.2
0.1
           0.0
                    (Part II:   Screening Values from  0 - 100,000 ppm)
                                                         , Upper Limit of 90% Confidence
                                                        / Interval  for Mean
                                                          Mean
                                                          Lower Limit of 90% Confidence
                                                        ' Interval for Mean
Equation for Predicted Mean Line

 NM Leak Rate = 8.59 (10"7) (Max Screening)1'16

 Least Squarat  FqnaHnn Used t.o Develop Chart;

 Log(NM Leak) - -7.00 + 1.16 Log (Max Screening)

 Correlation Coefficient - 0.71
 Standard Error = 0.914 Log (Leak Rate)
 Number of Data Pairs * 106
 Scale Bias Correction Factor • 8.59	 	
                    20,000   40,000   60,000   80,000   100,000



                        Maximum Screening Value  (ppmv as Hexane)

                      Using J. H. Bacharacn TLV Sniffer at the Source
   Figure 4-2.   Valves and Flanges - Gas/Vapor Streams - Part  II

                   Nomograph  for Predicting Total  Nonmethane Hydrocarbon

                   Leak Rates from Maximum Screening Values
                                           14

-------
                       (Part I:  Screening Values from 0-10,000  ppra)
§

i
O
§
w
H
a
     0.07 -
      0.06 -
      0.05 -
                                                      Upper Limit of 90S
                                                   / Confidence Interval  for Mean
                                                      Mean
                              Lower Limit of 90*
                              Confidence Interval for Mean
      0.01  -
              Equation for Predicted Mean Line:
              NM Leak Rate - 4.75 (TO"5) (Max Screening)0'76\
              Least Squares Equation used ta Develop Chart!
              Log(NM  Leak) = -4.80 + 0.76 Log (Max  Screening)

              Correlation Coefficient = 0.76
              Standard Error = 0.648 Log(Leak Rate)
              Number of Data Pairs = 147
              Scale Bias Correction Factor = 2.997
                 2000
4000
6000
8000
10,000
                    Maximum Screening Value (ppmv as Hexane)
                  Using J. U.  Bacharach TLV Sniffer at the Source
        Figure 4-3.   V.alves and Flanges  - Light Liquid/Two-Phase and
                        Heavy  Liquid Streams -  Part  I

                 Nomograph for Predicting  Total Nonmethane  Hydrocarbon
                 Leak Rates from Maximum Screening  Values
                                        15

-------
                        (Part II:  Screening Values from 0 - 100,000 ppm)
 M
JA

 co

r-t
N_/

w
52:
I
n
p
H
o
H
a
                                                      ' Upper Limit of 90S
                                                    /  Confidence Interval  for Mean
                                                       Mean
       0.25  _
                                                       Lower Limit of 90% Confidenes
                                                   /^ Interval for Mean
Foliation for Predicted Mean Line:

NM Leak Rate =4.75 (lo~5)(Max Screening) °-7&

Least Squares Equation used to Develop Chart:

Log(NM Leak) =• -4.30 + 0.76 Log (Max Screening)

Correlation Coefficient - 0.76
Standard Error « 0.648 Log (Leak Rate)
Number of Data Pairs « 147
Scale Bias Correction Factor « 2.997
                                        j_
                                                _L
                 20,000   40,000   60,000   80,000   100,000


                         Maximum Screening Value  (ppmv as  Hexane)

                     Using J. W. Bacharach TLV Sniffer at  the Source
     Figure  4-4.   Valves and Flanges -  Light Liquid/Two-Phase and
                     Heavy Liquid Streams  - Part II


                  Nomograph  for  Predicting Total Nonmethane Hydrocarbon

                  Leak Rates from Maximum Screening Values
                                      16

-------
w
55
O
PQ
o
O
53

O
W
H
         0.6 -
         Q.S -
         0.4
         0.3
         0.2
         0.1
                            (Part I:  Screening  Values from 0 - 10.000 ppm)
                        Upper Limit of 90%
                        Confidence Interval for Mean
                                                                     Mean
                                                                    Lower Limit of 90%
                                                                    Confidence Interval  for Mean
Equation for Predicted Mean Line:

NM Leak Rate = 4.9  (10"") (Max Screening)0-73
Least Squares Equation Used to Develop Chart;

Log (NM Leak Rate) = -4.00 + 0.73  Log (Max Screening)
Correlation Coefficient = 0.62
Standard Error = 0.78 Log IQ (NM Leak Rate)
Number of Data Pairs = 168
Scale Bias Correction Factor = 4.90
                1000  2000  3000  4000  5000 6000  7000  8000  9000  10,000



                            Maximum Screening Value  (ppmv as Hexane)
                         Using J. M. Bacharach TLV Sniffer at the Source


    Figure  4-5.   Pumps,  Compressors,  Drains,  Relief Valves -  Part I

                    Nomograph  for  Predicting Total Nonmethane Hydrocarbons
                    Leak Rates  from Maximum Screening Values
                                               17

-------
S5
o
PQ
O
§
§
H
O
                          (Part II:   Screening Values from 0 - 100,000 pom)
                                                                   Upper Limit of 90%

                                                                 / Confidence Interval  for Mean
                                                                    Mean
                                                                  Lower Limit of 90S

                                                                  Confidence Interval for Mean
                                          Equation for Predicted Mean Line:
           NM Leak Rate = 4.9 (10-4)  (Max Screening)0-73

           Least Squares Equation Used to Develop Chart:
           Log (NM Leak Rate) = -4.00 + 0.73 Log  (Max Screening)
           Correlation Coefficient » 0.62
           Standard Error = 0.78 Log IQ (NM Leak  Rate)
           Number of Data Pairs = 168
           Scale Bias Correction Factor = 4.90
                    20,000
40,000
60,000
30,000
100,000
                                Maximum Screening Value (ppmv as Hexane)

                             Using J.  W. Bacharach TLV Sniffer at the Source




    Figure  4-6.   Pumps,  Compressors,  Drains,  Relief Valves -  Part  II


                     Nomograph for Predicting  Total Nonmethane  Hydrocrabon

                     Leak Rates from Maximum Screening Values
                                              18

-------
                         TABLE 4-1.   CONFIDENCE INTERVALS FOR MEAN AND INDIVIDUAL LEAK RATES
                                        VALVES AND FLANGES - GAS/VAPOR STREAMS
vo
MAXIMUM SCREENING
VALUE (ppmv)
1
200
500
1,000
3,000
5,000
10,000
20,000
50,000
100,000
PREDICTED MEAN LEAK
(Ibs/hr)
io-7
io-5
0.001
0.003
0.009
0.017
0.038
0.084
0.24
0.54
RATE
90% CONFIDENCE INTERVAL FOR:
MEAN LEAK
(Ibs/hr)
(0.000 ,
(0.000 ,
(0.000 ,
(0.001 ,
(0.005 ,
(0.01 ,
(0.02 ,
(0.06 ,
(0.17 ,
(0.36 ,
IO"6 )
0.001)
0.003)
0.005)
0.02 )
0.03 )
0.06 )
0.12 )
0.35 )
0.82 )
INDIVIDUAL LEAKS
Clbs/hr)
(0.000 ,
(0.000 ,
(0.000 ,
(0.000 ,
(0.000 ,
(0.001 ,
(0.001 ,
(0.003 ,
(0.007 ,
(0.02 ,
io-* )
0.02)
0.04)
0.09)
0.31)
0.56)
1.2 )
2.7 )
7.9 )
17.7 )

-------
N>
O
           (Cont'd.)        TABLE 4-1.   CONFIDENCE INTERVALS  FOR MEAN AND  INDIVIDUAL LEAK RATES

                                          VALVES  AND FLANGES - LIGHT LIQUID/TWO-PHASE
                                              AND HEAVY LIQUID STREAMS
MAXIMUM SCREENING
VALUE (ppmv)
1
200
500
1,000
3,000
5,000
10,000
20,000
50,000
100,000
PREDICTED MEAN LEAK RATR
(Ibs/hr)
5 x 10~5
0.003
0.005
0.009
0.021
0.031
0.052
0.088
0.18
0.30
90% CONFIDENCE INTERVAL
MEAN LEAK
(Ibs/hr)
(0.000
(0.001
(0.004
(0.007
(0.02
(0.02
(0.04
(0.07
(0.13
(0.22
, 0.004)
, 0.007)
, 0.01 )
, 0.03 )
, 0.04 )
, 0.06 )
, 0.11 )
, 0.24 )
, 0.42 )
FOR:
INDIVIDUAL LEAKS
(Ibs/hr)
(0.000
(0.000
(0.000
(0.001
(0.002
(0.003
(0.004
(0.007
(0.01
(0.02
, 0.001)
, 0.03 )
, 0.06 )
, 0.11 )
, 0.24 )
, 0.36 )
, 0.61 )
, 1.0 )
, 2.1 )
, 3.6 )

-------
(Cont-'d.)        TABLE 4-1.  CONFIDENCE INTERVALS FOR MEAN AND INDIVIDUAL LEAK  RATES
                                PUMP SEALS,  COMPRESSOR  SEALS,  DRAINS,  RELIEF
                                  VALVES   -   ALL PROCESS STREAM TYPES
MAXIMUM SCREENING
VALUE (ppmv)
I
200
500
1,000
3,000
5,000
10,000
20,000
50,000
100,000
PREDICTED MEAN LEAK RATE
(lbs/hr)
0.0005
0.023
0.046
0.076
0.17
0.25
0.41
0.68
1.3
2.2
90% CONFIDENCE
MEAN LEAK
Clbs/hr)
(0.000 , 0.002)
(0.01 , 0.04 )
(0.03 , 0.07 )
(0.06 , 0.10 )
(0.13 , 0.22 )
(0.20 , 0.31 )
(0.32 , 0.51 )
(0.52 , 0.88 )
(0.96 , 1.8 )
(1.5 , 3.2 )
INTERVAL FOR:
INDIVIDUAL LEAKS
Olbs/hr)
(0.000 , 0.01)
(0.001 , 0.47)
(0.002 , 0.9i)
(0.003 , 1.5 )
(0.009 , 3.3 )
(0.01 , 4.8 )
(0.02 , 7.9 )
(0.03 , 13. )
(0.07 , 26. )
(0.12 , 43. )

-------
                                   TABLE 4-2.    SUMMARY  STATISTICS AND ESTIMATED  VAPOR EMISSION  FACTORS
                                                   FOR NONMETHANE HYDROCARBONS FROM  BAGGABLE SOURCES
NJ
ts>
SOURCE TYPE
VALVES
Gas/Vapor Streams
Light Liquld/Tvo-Phase Streams
Heavy Liquid Streams
PUMP SEALS
Light Liquid Streams
Heavy Liquid Streams
FLANGES (ALL)
Gas/Vapor Streams
Light Liquid/Two-Phase Streams
Heavy Liquid Streams
COMPRESSOR SEALS
Hydrocarbon Service
Hydrogen Service
DRAINS (ALL)
Light Liquid/Two Phase Streams
Heavy Liquid Streams
RELIEF VALVES (ALL)
Gas/Vapor Streams
Light Liquid/Two Phase Streams
Heavy Liquid Streams
TOTAL
SCREENED1

683
1019
522

470
292
2030
369
616
325

145
85
255
100
107
148
92
28
23
NUMBER
LEAKING2

200
372
35

300
66
62
10
33
6

102
69
49
26
19
58
42
7
8
PERCENT
LEAKING

29.3
36.5
6.7

63.8
22.6
3.1
2.7
5.4
1.9

70.3
81.2
19.2
26.0
17.8
39.2
45.6
25.0
34.8
95% CONFIDENCE
INTERVAL FOR
PERCENT LEAKING

(25.9
(33.6
( 4.6

(58.9
(17.1
( 2.2
( 0.8
( 3.3
( 0.2

(62.9
(71.2
(14.4
(14.6
( 9.5
(25.1
(35.2
(10.7
(16.4

, 32.7)
, 39.5)
, 8.9)

, 68.8)
, 28.1)
, 3.9)
, 4-6)
, 7.4)
, 3.5)

, 77.7)
, 88.8)
, 24.0)
, 37.4)
, 26.1)
, 40.6)
i 56.4)
, 44.9)
, 57.3)
PERCENTILE 95* OOHI
FOR INDIVIDUAL EMISSION INTERS
LEAKS (lb»/hr) FACTOR ESTIMATE EMISSI01
1st 99th (Ibs/hr-source) (Ibs/hr-

0
0
0

0
0
0
0
0
0

0
0
0
0
0
0
0
0
0

0.61
0.31
0.08

4.0
0.87
0.008
0.008
0.011
0.009

17.0
2.0
1.3
1.9
0.63
4.9
4.0
0.38
0.42

0.047
0.023
0.0007

0.26
0.045
0.00058
0.0005
0.0005
0.0007

0.98
0.10
0.070
0.085
0.029
0.19
0.36
0.013
0.019

(0.027
(0.016
(0.0002

(0.17
(0.02
(0.0002
do'5
(0.0002
(io-s

(0.46
(0.04
CO. 02
(0.02
(0.003
(0.06
(0.10
(0.001
(0.001
?IDENCE
U, FOR EMISSION
) FACTOR FACTOR
-source) PERCENTILE

, 0.084)
, 0.034)
, 0.002)

, 0.39 )
, 0.11 )
, 0.001)
, 0.005)
, 0.001)
, 0.02 )

, 2.0 )
, 0.24 )
, 0.20 )
, 0.32 )
, 0.21 )
, 0.52 )
, 1.30 )
, 0.23.)
, 0.20 )

94.4
89.7
95.8

89.8
88.4
97.4




83.4
86.5
93.3


91.9



             *Sone streams could not be accurately classified Into stream category so the totalb are not the sum of the stream groups.

             2Leaking sources in this report are defined as sources with screening values greater than or equal to 200 ppav or
                       with measured leak* greater than 0.00001 IbWhr.

-------
greater  than 90% is an indication of the extreme skewness of the leak rate
data.

      A very high degree of correlation was found between mass emission rates
and the type of stream service in which the sources were employed.  The pro-
cess stream groups are described in Table 3-3 of this report.

      It  is evident from Table 4-2 that individual sources in gas/vapor stream
service  emit more hydrocarbons than comparable sources  in heavy liquid- service.
On the average, for example,  valves in gas/vapor service emit more than 70
times as much material as valves in heavy liquid service.

      Because of the large influence of stream type on source emissions,  over-
all emission factors for valves and pump seals are not  presented.   Due to
the experimental design, the distribution of sampled valves and pump seals
among the stream groups is not representative of the overall distribution
of sources within refineries.  Thus, overall emission factors for valves and
pump seals, as determined from the sampling programt are not directly appli-
cable to either entire refineries or individual process units.   The stream
group distributions must be known or estimated to develop accurate overall
process unit and refinery emission factors for these two source types.

      The emission factors for valves given in Table 4-2 were developed for
 in-line pipeline valves.  The emission points were around the valve stem
and around the perimeter of the packing gland.  A small number of open-
ended valves were also sampled, such as drain valves and sampling valves.
The screening and sampling point for these valves was the open-end of the
pipe downstream from the valve.  The emission occured through the valve
 seat rather than around the valve stem.  The average emission factor for
 these open-ended valves was 0.007 Ib/hr with a 95% confidence interval of
0.002 - 0.016 Ib/hr.  A total of 129 open-ended valves  were screened, and
 30 were found to have screening values _>_ 200 ppmv hydrocarbon.

Distribution of Sources within a Refinery

      In order to ascertain the relative contribution of the various source
types, the number of sources of each type and stream classification in a
refinery must be known.  Some counting of source types  was done during.this
sampling program, but these counts were not recorded by process stream
groups.   To give an indication of the relative importance-of the various
source types, a hypothetical refinery model has been used.   The model is
based on the ADL-Texas Gulf Cluster Model1 processing 330,000 BPCD of crude.
The total number of fittings in the various process units in this hypotheti-
cal model are estimated from counts of fittings made during this program.

      Since very little information is available on the  number of sources in
the various types of stream service, two cases are presented:

1Kittrell, J.R.,Impact of SOX Emissions Control on Petroleum Refining Industry,
  Volume II. Detailed Study Results, EPA/699/2-76/161B,  June 1976
                                     23

-------
    Case I  - The distribution of stream types for valves is weighted toward
              liquid streams, the distribution for pump seals is weighted
              toward the heavy liquid streams, and the distribution for com-
              pressor seals is weighted toward hydrogen service.

    Case II - The distribution of stream types for valves is weighted toward
              gas service, the distribution for pump seals is weighted
              toward light liquid streams, and the distribution of compressor
              seals is weighted toward hydrocarbon service.

It should be emphasized that these two cases and the hypothetical refinery
model are being used only for exemplary purposes in this report.  An equiva-
lent analysis can be done for any particular situation using appropriate num-
ber of sources and stream classifications in conjunction with the emission
factors in this report.

     Table 4-3 shows the number of sources for the above two cases in the
hypothetical refinery and the results of applying the emission factors from
Table 4-2 to these numbers.  The emissions thus obtained have been divided by
the total emissions from all source types to give the percent of total non-
methane hydrocarbon emissions attributable to each source category.

     For this hypothetical refinery model, it is clear that valves, because of
their number and relatively high emission factors, are the major emission
source among"the source categories included in this report.  Depending on the
case, valves are expected to contribute from 61 to 67 percent of the total
emissions from the six source types in this hypothetical refinery.

     Although flanges represent the greatest number of any source type in the
hypothetical model, their small emission factor results in an expected con-
tribution of only 6 to 8 percent of total emissions.  The contribution from
drains has an expected value of 11 to 15 percent.  Pump seals, compressor
seals, and relief valves each have maximum expected contributions of 9 percent
or less, using this model.

Distribution of Leak Rates

     Table 4-4 gives the distribution of measured and estimated nonmethane
hydrocarbon emission rates for each source type.  It is obvious from this
table that the bulk of the emissions emanate from a small percentage of the
sampled fittings.  The table represents an idealized situation for reducing
emissions by selective maintenance of sources.  For example, the table indi-
cates that if a particular 3.6% of the valves in gas/vapor service in a re-
finery (those with leak rates greater than 0.1 Ibs/hr) could be repaired
such that the leak rate of each such valve was reduced to zero, then 91.1%
of the mass emissions attributable to valves in gas/vapor service could be
eliminated.  The problem in practical implementations of such a repair
program is locating those particular 3.6% of the valves in gas/vapor service
with leak rates greater than 0.1 Ibs/hr without bagging and sampling all
such valves in a refinery.


                                    24

-------
Oi
                                      TABLE  4-3.   HYPOTHETICAL REFINERY - BASED  ON ADL  TEXAS
                                                     GULF  CLUSTER MODEL  (330,000 BPCD)
PERCENT OF TOTAL NONMETHANE HYDROCARBON EMISSIONS
SOURCE TYPE
Valves
Gas/Vapor
Light Liquid/Two-Phase
Heavy Liquid
Pump Seals
Light Liquid
Heavy Liquid
Compressor Seals
Hydrocarbon Service
Hydrogen Service
Flanges
Drains
Relief Valves
(venting to atmosphere )

NUMBER OF SOURCES (PERCENT)
CASE I4 CASE II2
14300
1430
7150
5720
264
106
158
27
14
13
51200
793
64



(10%)
(50%)
(40%)

(40%)
(60%)

(52%)
(48%)





14300
4290
5720
4290

158
106
27
20
7
51200
793
64



(30%)
(40%)
(30%)

(60%)
(40%)

(74%)
(26%)





CASE I
ESTIMATE
61.6
17
43
1
9.1
7
1
. 3.9
3
0
7.7
14.5
3.2

100%

.6
.0
.0

.2
.9

.6
.3





(95/6 CD3
(46.5
(10.1
(29.9
( 0.3
( 6.3
( 4.7
( 0.8
( 2.0
( 1.7
( 0.1
( 2.9
( 4-i
( 1.0


, 86.4)
, 31.4)
, 63.5)
, 3.0)
13.6)
, 10.8)
, 4.5)
, 7.7)
, 7.3)
, 0.8)
, 13.4)
, 41.4)
, 3.9)


CASE II
ESTIMATE
67.3
:40.4
26.3
0.6
9.2
8.2
1.0
4.1
3.9
0.2
5.9
11.1
2.4

100%
(95% CI)S
(48.3
(23.2
(18.3
( 0.2
( 6.3
( 5.4
( 0.4
( 1.9
( 1.8
( 0.01
( 2.2
( 3.2
( 0.8


, 100)
, 72.1)
, 38.9)
, 1.7)
, 13.5)
, 12.3)
, 2.3)
, 8.1)
, 8.0)
, 0.15)
, 10.2)
, 31.7)
, 6.7)


                       1 Case I - distribution of stream types for valves and pump seals is weighted toward heavier streams.

                       2 Case II - distribution of stream types for valves and pump seals is weighted toward lighter streams.
                       3 95% CI - 95% confidence interval for percent of emissions from process fittings attributable
                        to a particular source type.  The width of the Interval is due only to the uncertainty in
                        emission factors;  the percentage of each source type is assumed fixed or known.
                       " Total  is the sum of nonmethane hydrocarbon emissions  from the six source  types discussed In this
                         table.

-------
                                         TABLE  4-4.   DISTRIBUTION OF MEASURED LEAK RATES1
                                                         VALVES
                                                                                                       PUMP SEALS
to
Leak Range
(Ib/hr)
>1.0
0.1 -1.0
0.01-0.1
0.001-0.01
0.00001-0.001
>0. 00001
Leak Range
(Ib/hr)
>1.0
0.1-1.0
0.01-0.1
0.001-0.01
0.00001-0.001
>0. 00001
Gas/Vapor
Streams
A B
1.0 68. A
2.6 22.7
8.6 7.9
8.9 0.9
8.1 0.1
29.2%
Light Liquid/
Two-Phase Streams
A B
0.0 13.8
3.3 58.8
11.5 23.7
13.4 3.5
8.1 0.2
100% 36.3%
COMPRESSOR SEALS
Hydrocarbon
Service
A
15.9
33.1
16.6
4.8
2.1
72. 5Z
B
74.2
• 24.3 ,
1.4
0.1
0.0
100%
Hydrogen
Service
A
0
16.5
25.9
24.7
14.1
81.2%
100%
Heavy Liquid
Streams
A
0
0.2
0.9
2.7
2.9
6.7%
FLANGES
B
0.
33.6
48.0
16.9
1.5
100%
All Stream
Croups
B
0.
75.6
22.5
1.8
0.1
100%
A
0
0.2
0.6
1.4
0.9
3.1%
B
0.0
63.2
30.1
6.0
0.7
100%
Light Liquid
Streams
A
4.0
15.7
22.5
16.4
4.9
63.5%
DRAINS
B
90.5
24.8
4.3
0.4
0.0
100%
All Stream
Groups
A
1.5
4.7
6.7
5.1
1.2
19.2%
B
61.6
33.0
4.9
0.5
0.0
100%
Heavy Liquid
Streams
A
0
5.5
9.6
5.8
1.7
22.6%
RELIEF
B
0.
73.2
25.6
1.2
0.0
100%
VALVES
All Stream
Groups
A
3.4
10.1
14.9
7.4
2.7
38.5%
B
76.0
19.2
4.5
0.3
0.0
100%
                  A - Percent of total sources screened with sampled leak rates within leak range.
                  B - Percent of total mass  emissions attributable to sources within leak range.
                  1  - Most sources were bagged and sampled to obtain leak rates; some were estimated using procedures
                      described in Section 1 of Appendix A.

-------
This is obviously  impractical,  so  the  identification of sources requiring
maintenance must occur  through  some  type of screening program.

Distribution of Emissions  and Sources  Based on Screening Values

     A convenient  tool  both  for monitoring hydrocarbon emission sources and
estimating source  leak  rates is the  portable hydrocarbon detector.  From the
results of this study,  nomographs  have been prepared relating hydrocarbon
concentration  at the  source  (screening value) to the percentage of each
source type expected  to have screening values above any selected value.
Other nomographs have been prepared  relating screening values to the per-
centage of total mass emissions which  can be expected from sources with
screening values greater  than any  given value.   (See Appendix A for a dis-
cussion of nomograph  development.)

     These nomographs for  the six  source types (and stream groups for valves,
compressors, and pump seals) are presented in Figures 4-7 through 4-16.  The
"A"  figures relate the  percent  of  total mass emissions for a given source
category to screening values; the  "B"  figures relate the percent of sources
to screening values.  The  screening  values in these nomographs are the hydro-
carbon concentrations obtained  at  the  source (zero cm) with a Bacharach TLV
Sniffer calibrated with hexane.

     Confidence intervals  are included on each of these nomographs.  The
statistical procedures  used  to  develop these intervals are discussed in
section 4.2 and 4.3 of  Appendix A.   The confidence intervals for both types
of nomographs  indicate  how well the  cumulative function has been estimated
from the data  collected in this program.

     The 95 percent confidence  intervals for the cumulative percent of sources
can  be interpreted as ranges of values which contain the actual percent from
the  population of  sources  studied.   Note that these intervals apply to the
entire population  of  sources (i.e.,  a  composite of all United States refin-
eries), and are not necessarily applicable to a finite number of sources
at any particular  refinery.  Because of the nature of the function, the
confidence intervals  will  be approximately valid anytime a random sample of
greater than 100 sources  is  being  considered.

     The 90% cqnfidence intervals  for  the cumulative percent of total emis-
sions function can be interpreted  as ranges of values which contain the
actual percent of  total emissions  function for the entire population of
sources.  Again, these  intervals describe how well the function has been
estimated for  the  entire population  and are not directly applicable to a
particular refinery situation with a finite number of sources.  The variation
of the function for a particular sample of sources is a complex function of
the  number of  sources.  Section 4-3  of Appendix A discusses this issue
further and gives  an  example of particular confidence bounds for valves in
light liquid/two-phase  service.
                                     27

-------
                       Valves  - Gas/Vapor Streams
  100


   90


   80
I  70
£  60
V)
in

-  50

•W


f  «
O


§  30
fc.


   20



   10
                                                          N   Upper Limit of 90S
                                                              Confidence Interval
                                            Estimated
                                            Total
                                         Lower Limit of
                                         90% Confidence
     X  2345  10      50100    5001000      10,000     100,000   1,000,000
                    Screening Value  (ppmv)  (Log,. Scale)

           Percent of Total  Mass Emissions -  indicates the percent of total emissions
                                         attributable to sources with screening values
                                         greater than the selected value.
   figure 4-7A.   Cumulative Distribution of Total Emissions by
                    Screening  Values - Valves - Gas/Vapor  Streams
                                    28

-------
                    Valves - Gas/Vapor Streams
  100


   90


   80


   70
3  60
c.
8  40


   30


   20


   10
                •Upper Limit of 952 Confidence Interval
                                       Estimated Percent of Sources
                     Lower Limit of
                     the 95S Confidence
                     Interval	
                                              -P
                                               \   .  . 7j--r^r-^
     1  2345  10     50100     5001000        10,000    lOQ-,000   1,000,000
                     Screening Value (ppmv) (Log^.  scale)

       Percent of Sources - Indicates the percent of sources with screening
                          values greater than the selected source.
    Figure 4-7B.   Cumulative Distribution  of Sources  by
                     Screening  Values - Valves - Gas/Vapor
                     Streams
                                  29

-------
                   Valves - Light Liquid/Two-Phase  Streams
      100


       90



       80


     | 70
     t/t
     Vt

     <§ 60
,_  40
o

8  30

I
   20
       10
                            Estimated Percent of
                            Total Mass Emissions
                                               \\\  Upper Limit of 90X
                                           Lower Limit" of the
                                           90S Confidence Interval A \
         1  2345  10     50100        1000     10,000    100,000    1,000,000

                          Screening Value (ppmv) (Log1Q Scale)

              Percent of Total Mass Emissions - Indicates the percent of total emissions
                                           attributable to sources with screening values
                                           greater than the selected value.
Figure 4-8A.   Cumulative  Distribution of  Total Emissions by  Screening
                 Values - Valves  - Light Liquid/Two-Phase  Streams
                                       30

-------
            Valves - Light Liquid/Two-Phase  Streams
   100


   90


   80


   70


   60
    50
   40
 £

   30


   20


   10
Upper Limit of 95Z Confidence Interval
                      timated Percent of Sources
      1  2345 10
         50100      1,000        10,000

          Screening Value (ppmv)  (Log1Q Scaled
,000
       Percent of Sources - indicates the percent of sources with screening
                         values greater than the selected value.
Figure 4-8B.  Cumulative Distribution of  Sources by Screening
                Values - Valves - Light Liquid/Two-Phase Streams
                                  31

-------
    100



     90



     80

 Ul

 5   70
 (A
 «l

 iS   60
 «•
> M
 +.   40
 o
 g   30

 I
     20


     10


     0
                     Valves -  Heavy Liquid  Streams
              \ \ \ Upper Limit of 90S
               .  \ \Ctmfidence Interval
               \ \  \
  Estimated Percent of.
  Total Mass Emissions*
    Lower Limit of the 90S\  \ \
    Confidence Interval    \  \ \

                         \\\
n   I   i
               .L   I I  I i   I

       1  2 345  10      50 100     5001000      10,000     100,000     1,000,000

                          Screening  Value (ppmv) (Log1Q Scale)

          Percent of Total Mass Emissions  - indicates the percent of total  emissions
                                        attributable to sources with screening values
                                        greater than the selected value.
  Figure 4-9A.   Cumulative Distribution  of Total  Emissions  by
                   Screening  Values -  Valves -  Heavy Liquid  Streams
                                    32

-------
                        Valves -  Heavy Liquid  Streams
    §
    I/)
    
-------
I/I
i
100


 90  -


 80


 70


 60


 50


 40


 30


 20


 10
           Pump  Seals  - Light: Liquid  Streams


                         \ ~	—
                                                Up0er Limit of 90%
                                                          Interval
Estimated Percent of
Total Mass Emissions
                                             Lower Limit of the     -\\
                                             Confidence Interval 90%
      I  2345    10    50  100    5001000      10,000    100,000    1,000,000

                       Screening Value (ppmv)  (Log1Q Scale)

        Percent of Total Mass Emissions  - indicates the percent of total emissions
                                     attributable to sources with screening values
                                     greater than the selected value.
Figure  4-10A.   Cumulative Distribution of Total  Emissions by
                  Screening Values - Pump Seals - Light  Liquid
                  Streams
                                   34

-------
           Pump Seals - Light  Liquid Streams
£

-------
                Pump Seals -  Heavy Liquid Streams
                                \ Upper Limit of 90%
                                   \ Confidence Interval
                                \  \   \
               Estimated Percent of v  \   \
                      Confidence Interval 90s
       2 3 45  10
50 100     5001000      10,000     100,000    1,000,000
 Screening  Value (ppmv) (Log   Scale)
        Percent of Total Mass Emissions - indicates the percent of total emissions
                                      attributable to sources with screening values
                                      greater than the selected value.
Figure 4-11A.   Cumulative Distribution of Total Emissions by
                  Screening  Values - Pump Seals  - Heavy Liquid
                  Streams
                                 36

-------
                     Pump Seals  - Heavy Liquid  Streams
       O

       44
 100


  90


  80


  70


  60


i  50






  30


  20


  10
                           Limit of 95% Confidence Interval
                                         Estimated Percent of Sources
                   Lower Limit of the\  x  \
                   the 95S Confidence  \ \ \
                   Interval            N
            1  2345  10     50100    5001000      10.000     100,000    1,000,000
                             Screening Value (ppnrv)  (Log,. Scale)
               Percent of Sources -Indicates the percent of sources with  screening
                                v«1uM greater than the selected value.
Figure  4-11B.   Cumulative Distribution of Sources by  Screening Values
                  Pump Seals -  Heavy Liquid Streams
                                       37

-------
              Compressor Seals - Hydrocarbon Service
VI
c
o


t/l


I






m

o
 0)
 u
                                                 Upper Limit of 90%

                                                 Confidence Interval
                                                           Estimated  Percent of

                                                           Total Mass Emissions
                                 Lower Limit of 9055

                                 Confidence Interval
          2 345  10
                        50 100
500 1000
10,000
100,000    1,000,000
                       Screening Values (ppmv)  (Log1Q Scale)




         Percent of Total Mass Emissions - indicates th« percent of total emissions

                                      attributable to sources with screening values

                                      greater than the selected value.
Figure 4-12A.   Cumulative Distribution of Total Emissions by

                  Screening  Values - Compressor  Seals  -

                  Hydrocarbon Service
                                   38

-------
      Compressor Seals -  Hydrocarbon  Service
                            Upper Limit of 95%
                            Confidence Interval
                                          Estimated Percent of Sources
                 Lower Limit of 95*'     \
   2345  10      50100       1,000      10,000     100,000    1,000,000

              Screening Value (ppmv) (Log-,0 Scale)


     Percent of Sources -indicates the percent of sources with screening
                     value* greater than the selected value.
Figure 4-12B.
Cumulative Distribution of Source by
Screening Values - Compressor Seals  -
Hydrocarbon Service
                           39

-------
                 Compressor Seals -  Hydrogen Service
   100




    90  -




    80 1-

ut
e

•£   70
V)


i

»   60
s   50
o
    30




    20




    10




     0
                                                     Upper Limit of 90%

                                                     Confidence Interval
                                                           Estimated Percent of

                                                       V~ Total Mass Emissions
                                        Confidence Interval     \
          2345  10     50100       1000       10,000     100,000    1,000,000



                     Screening Values (ppmv) (Log 10 Scale)
     Percent of Total Mass Emissions - Indicates tin percent of total emissions
                                  attributable to sources with screening values

                                  greater than the selected value.
        Figure 4-13A.   Cumulative Distribution  of Total Emissions

                         by Screening  Values - Compressor Seals  -

                         Hydrogen Service
                                   40

-------
                 Compressor  Seals  - Hydrogen Service
M

41
o
ft
o

•u
c
at
100




 90




 80




 70




 60




 50




 40




 30




 20




 10
                                           Upper Limit of 95%

                                           Confidence Interval
                                              Estimated Percent of Sources
                      Lower Limit of 95%

                      Confidence Interval
      1   2345  10     50100       1000      10,000      100,000    1,000,000



                     Screening Value (ppmv) (Log1Q Scale)
              Percent of Sources -indicates the percent of sources with screening

                               value* greater than the selected value.
       Figure 4-13B.   Cumulative  Distribution of  Sources by

                         Screening Values  - Compressor Seals -

                         Hydrogen Service
                                    41

-------
                                   Flanges
   100



    90



    80



|   70
IA
in

1   60

1A
VI
£   50

«0

£   40
<*-
o

    3d

-------
                                  Flanges
s
«1-
o
    100


      90


      80


      70


      60


      50


      40
  e
  0)

 I   30
      20


      10


      0
        1
         Lower Limit of the
         the 95% Confidence
         Interval

                     'Estimated Percent of Sources


                               , ^Upper Limit of 95* Confidence Interval


          2345  10      50100        1000       10,000     100,000    1,000,000

                        Screening Value (ppmv)  (Log,- Scale)
          Percent of Sources - Indicates the percent of sources with screening
                             values greater than the selected value.
Figure  4-14B.   Cumulative Distribution of Sources  by  Screening
                   Values -  Flanges
                                     43

-------
                                   Drains
   '100



    90 f-



    80 -



i   70-
»*">
I/I
Irt

1   60

Vt

3.   so
r™
10

£   40
g   30
    20


    10
                         \  \   \  Upper Limit of 90S
                          \   \   XN Confidence '-*	^
                            \   \   \
                             \  \   N
                                   .    ,  \
               Estimated Percent of  \   \   \
               Total Mass Emissions   \^   \
                        Lower Limit of the
                        Confidence Interval 90% \
           i  i i  i   1   i  i i  i
                                                         ,\\\
2345  10      50100     500.1000      10,000     100,000
            Screening Value  (ppmv) (Log^ Scale)
                                                                     1,000,000
           tereent of Total  Mass Emissions - indicates the percent of total emissions
                                          attributable to sources with screening values
                                          greater than the selected value.
   Figjire  4-15A.   Cumulative Distribution  of Total  Emissions by
                      Screening Values  - Drains
                                     44

-------
                                   Drains
g
in
<*-
o
+*
|


-------
                           Relief Valves
                                            \     Upper Limit of 90X
                                             \fr*Confidence Interval
                                                        Estimated Percent of
                                                        Total  Mass Emissions
                            Lower Limit of 90%
                            Confidence Interval
      2345  10      50 100        1000       10,000
                  Screening Value  (ppmv) (Login Scale)
1,000,000
   Percent of Total Mass Emissions - Indicates the percent of total emissions
                                 attributable to sources with screening values
                                 greater than the selected value.
Figure  4-16A.   Cumulative Distribution of  Total Emissions
                  of  Screening Values -  Relief Valves
                                  46

-------
                             Relief Valves
   100



    90



    80



    70

VI

£   60
3
O

t   50
S   40

-------
     The nomographs must be used with caution.  As discussed earlier, the
correlation between screening values and actual leak rates is imperfect.
Because of this, values obtained from the nomographs for percent of total
sources and percent of total emissions at a specific screening value will
not exactly match similar values in Table 4-4, if one converts screening
values to leak rates.  In most cases, the nomographs will indicate a higher
percentage of sources being responsible for a given percentage of total
emissions than Table 4-4.  In this sense, the nomographs are conservative
(i'.e., they will identify more sources than necessary to achieve a given
level of reduction on total emissions).  In a practical sense,  however, un-
less every source with a screening value exceeding a specific level is
bagged and sampled, there is no better method than screening for identi-
fying sources for maintenance.

     The nomographs can be used to evaluate the potential effectiveness of
maintaining and repairing sources for reducing emissions.  For example,
approximately 5% of valves in gas/vapor stream service can be expected to
have screening values above 50,000 ppmv (Figure 4-7B) .   However,  these 5%
of the valves are responsible for an estimated 92% of the mass emissions
(Figure 4-7A).  Similarly, for a screening value of 10,000 ppmv, the percent
of sources and percent of emissions are 10%, and 98%, respectively.  (See
example lines on Figures 4-7A and 4-7B).

     Analyses, using the nomographs, can also be done for other sources and
process streams.  For example, Table 4-5 shows the percent of emissions
for various sources and process streams when the upper  10% of screened
sources are considered.  Confidence intervals are also  shown.  Table 4-5
is presented only to illustrate the use of the nomographs and to emphasize the
fact that a small fraction of the sources within any one source category
account for the majority of emissions in that category.  There is no intent
here to prejudge that a reasonable level of control is  10% of sources, or
any other specific number.  Ultimately, the decision regarding reasonable
control will be based on reducing overall emissions.  Therefore, percentage
reduction goals for each source category may be different.  The variations
in source emissions from a hypothetical refinery (Table 4-3) further illu-
strates the. need to develop different emission reduction goals for various
source categories.

     In summary, Figures 4-7 through 4-16 present continuous distributions
of the percent of emissions and sources versus specific screening values.
These figures can be used to estimate the reduction in emissions which could
ideally occur if a given percentage of leaking sources  were repaired.  It is
emphasized that these figures represent an amalgamation of data from nine
refineries (thirteen for compressor  seals and relief valves) and do not
represent any single refinery.  Therefore,  these results must be used with
caution when analyzing a specific refinery or process unit.
                                     48

-------
VO
                                  TABLE 4-5.   PERCENT OF  TOTAL MASS EMISSIONS  RELEASED BY THE
                                                   UPPER1 TEN PERCENT OF  SCREENED SOURCES
SOURCE
VALVES
Gas/Vapor
Light Liquid/ Two-Phase
Heavy Liquid
PUMP SEALS
Light Liquid
Heavy Liquid
COMPRESSOR SEALS
Hydrocarbon Service
Hydrogen Service
FLANGES
DRAINS
RELIEF VALVES
MINIMUM SCREENING
VALUE (ppmv)
•
11,000
12,000
120

44,000
1,500

50,000
120,000
17
1,200
4,500
95% CONFIDENCE INTERVA1
FOR PERCENT OF SOURCES

( 7
( 7
( 5

( 7
( 5

( 4
(3
( 7
( 4
( 4

, 13 )
, 12 )
, 15 )

, 13 )
, 15 )

, 18 )
, 15 )
, 13 )
, 15 )
, 18 )
PERCENT OF TOTAL EMISSIONS
I.
MEAN

98
82
77

68
60

47
41
98
78
80
90% CONFIDENCE
INTERVAL

( 97
( 78
( 69

( 63
( 47

( 31
( 23
( 97
( 68
( 65

, 99 )
. 86 )
, 85 )

, 75 )
, 78 )

, 64 )
, 57 )
, 99 )
, 90 )
, 87 )
                          1 The upper ten percent of screened sources is defined as the ten percent of sources
                           having the highest screening values.

-------
 Appendix A.  Emission Factor Development - Statistical Considerations

     Because of the high degree of skewness in the distribution of nonmethane
leak rates from baggable sources, conventional statistics are inadequate for
efficient estimation of emission factors and their variances.  In addition  to
the skewness, a large percentage of the sources studied were considered "non-
leaking •   These sources affect the emission factor and therefore must be
considered in developing estimates for these factors.  Another statistical
problem which had to be addressed in developing the emission factors was the
estimation of leak rates for sources which screened greater than or equal to
200 ppmv but were not sampled.

A.I  Estimating Emissions for Nonsampled Sources

     Due to  time and equipment  constraints, it was not always possible to
sample  all sources that  screened greater than 200 ppmv.  At the fifth re-
finery, a sampling strategy was developed to reduce the sampling workload.
All sources  screening greater than 10,000 ppmv were sampled, but only one-
fourth  of the valves and pumps  with screening values between 200 and 10,000
ppmv were sampled.  In order not to bias the distribution of leaking sources,
it was  necessary to develop estimated values for all sources screening
greater than 200 ppmv and not sampled.  The number of  sources sampled and
estimated for  each source type  is shown in the following table:

Baggable Source              Total Sources         Sources         Sources  to
     Type                 Sampled or Screened      Sampled        be Estimated
	           	>200 ppmv	      	        	

 Valves                           627                 474              153
 Pump Seals                       382                 281              101
 Compressor  Seals
   Hydrocarbon Service            102                  83               19
   Hydrogen  Service                69                  60                9
 Flanges                           62                  43               19
 Drains                            49                  28               21
 Relief Valves                     58                  31               27
      Least-squares  regression analyses were done for each device type, re-
 gressing  the logarithm of  the nonmethane leak rate on the logarithm of the
 maximum screening reading.   Both  the original screening value and rescreen-
 ing values  (taken closer to  the time of sampling for leak rate) were evalua-
 ted and a "best" equation  was selected for each device as summarized in
 Table A-l.

      Using  the  equations in  Table A-l, predicted log-nonmethane leak rates
 were  computed for each source not sampled with a screening value greater than
 or equal  to 200 ppmv.   Leak  rates (lb/hr) were then computed using

      leak rate  = explO [Log  leak  +  z  (standard error of estimate)],
                                     A-l

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                     TABLE A-l.  PREDICTION EQUATIONS FOR NONMETHANE LEAK RATES
                                 BASED ON MAXIMUM TLV SCREENING OR RESCREENING VALUES




T
S3

SOURCE TYPE
Valves
Pump Seals
Compressor Seals:
Hydrocarbon Service
Hydrogen Service
Flanges
Drains
Relief Valves
LEAST - SQUARES EQUATION
LOG(NMLK)=
LOG(NMLK)=
LOG(NMLK)=
LOG(NMLK)=
LOG(NMLK)=
LOG(NMLK)=
LOG(NMLK)=
-5
-4
-4
-3
-5
-5
-4
.41 +
.64 +
.77 +
.66 +
.11 +
.02 +
.47 +
0.88
0.89
0.92
0.44
0.84
1.16
0.87
LOG(MKTLV-RS)
LOG(MXTLV-RS)
LOG(MXTLV-RS)
LOG(MXTLV- S)
LOG(MXTLV- S)
LOG(MXTLV- S)
LOG(MXTLV-RS)
NUMBER
OF DATA
PAIRS
177
171
48
44
47
60
53
CORRELATION
COEFFICIENT
(r)
0
0
0
0
0
0
0
.78
.68
.58
.36
.74
.72
.78
STANDARD
ERROR OF
ESTIMATE
0
0
0
0
0
0
0
.736
.820
.791
.884
.535
.807
.637
NMLK - Nonmethane leak rate (Ib/hr)
MXTLV- S - Maximum value - original screening, (ppmv)
MXTLV-RS - Maximum value - rescreening (ppmv)
LOG - Logarithm, base 10

-------
where z is a random number from a standard-normal distribution.  The use of
the random number is an attempt to yield a predicted distribution of leak
rates which would approximate the distribution  if all sources were sampled.
No bias correction factor is needed in going from the Log to arithmetic scale
since the mean leak rate is not being predicted.  These predicted leak rates
were used in further analyses and development of emission factors.

     Because the true  leak rate/screening relationship is unknown, there is a
potential bias introduced when these predicted  leak rates are used in devel-
oping emission factors.  The potential bias is  proportioned to the standard
error of the estimates divided by the number of data pairs used to develop
the equation.  The impact of the bias on emission factors depends on the per-
cent of sources leaking.  The potential bias was found to be less than one
percent for all source types except compressor  seals and relief valves.  The
potential biases were  estimated to be ±9.6% of  the emission factor for
relief valves, ±17.5%  for compressor seals in hydrocarbon service, and ±7.1%
for compressor seals in hydrogen service.  These potential biases were taken
into consideration, in  developing confidence intervals 'as discussed in
Section A.3.

A.2  Statistical Distribution Models for Leak Rates

     A lognormal distribution was used to model the distribution of leaking
sources.  This distribution has the property that when the original data are
transformed by taking  natural logarithms, the transformed data will follow a
normal distribution.   The lognormal distribution is often appropriate when
the standard error of  an individual value is proportional to the magnitude of
the value.  The form of the lognormal distribution is as follows:


                         r_  (In x - y)2-i
               f(x)  = "PL       2cT    J             for    0>x>°°
                               X0/21T

                    = 0                             for   x £ 0
                              2
               Mean = exp[yH	j ^

               Variance = exp[2y + 2a2]  - exp[2y + a2]

      In order to develop estimates for emission factors,  the non-leaking
 sources Cleak rate assumed equal to zero)  also  had to  be  modeled.  A mixed
 distribution, specifically a lognormal distribution with  a discrete probab-
 ility mass at zero,  was used for this purpose.   Letting p equal the fraction
 of  nonleaking sources in the population,  this distribution has the following
 form:
                                      A-3

-------
                     fT  \    r  (In x -
                     (1"P)
              f (x) =           -      2             for   0
                              XCT/2TT

                   = p                             for   x = 0

                   =0                             for   x < 0
                                     2
             Mean  = (1-p) exp[y +  — ^ ]


             Variance = (1-p) [exp(2y + a2)] [exp(a2) -  (1-p)]

Efficient estimates of the mean and variance of the population modeled by
this mixed distribution have been developed [Finney (1941), Aitchison  (1955)],
These estimates are as follows:

The best, unbiased estimator of the population mean emission rate is

                       m = [ (1 - J) exp [ (x) ] g  (f  )

and the best, unbiased estimator of the population variance of the emission
rates is

                v = [ (1 -  ) exp(2x) [g(2s2) - (1 -

where  n = number of sources screened,
       r = number of sources screened <200 ppm or with
           measured leak <10~5 Ibs/hr

 m =s n_r = number of "leaking" sources,

    g(t) = infinite series

         _     (m-l)t       (m-1)3 t2         (m-1)5 t3
                 m          m^2! (m+1)  "*"   m33! (m+1) (m+3)

      x  = average of the logarithm of leaking sources
          n-r
                In (nonme thane leaks) /(.n-r)
      s2 = variance of the logarithm of leaking sources
          n-r
         =T1    fin (nonmethane leaks) - x]2/(n-r^l)-
           i
                                     A-4

-------
The mean and variance  formulas  hold whenever  there  is more than one leaking
source (n-r >1) .  When only  one leaking  source  is identified, the following
estimates are appropriate:
                                    2
       mean  = —  and variance = ^!—
             = —
               n
                                   n
where x, is the  single measured  leak. If no leaks are found  (r=n), then the
best estimate for both the mean  and variance is zero.

     Computer programs were developed for these estimators and the estimator
for the mean was used for all  emission factors presented in  this publication.
Finney (1941) showed that this estimator is more than twice  as efficient as
the arithmetic mean for  data distributed similarly to the leak rates from
baggable sources.

     Since data  distributed lognormally can be transformed to a normal dis-
tribution by taking natural logarithms of the data, the distribution
assumptions can  be tested by examining distributions of the  Log leak rates.
Histograms displaying these distributions were constructed for all important
source type and  process  stream classifications.  The data for most sources
appeared to adequately approximate a normal distribution.  The compressor
seals data from  hydrocarbon service and the heavy stream data for pump
seals both appeared skewed to  the left.  Compressor seals with sampled leak
rates less than  10  3 were considered as negligible (zero) to minimize this
skewness.

     To statistically test the assumption of a normal distribution for the
log-leak rates,  skewness and kurtosis  statistics were computed for each data
group and tested for departures  from their expected values of zero in a nor-
mal distribution.  The following table summarizes these statistics.
      Source Type/
      Stream Group

 Valves (all)
  Gas/Vapor Streams
  Light Liquids/Two-Phase
  Heavy Liquids

 Pump  Seals (All)
  Light Liquids
  Heavy Liquids

 Compressor Seals
  Hydrocarbon Service
  Hydrocarbon Service

 Flanges

 Drains

 Relief Valves
                                    Number of
                                 Leaking Sources

                                      627
                                      200
                                      372
                                       35

                                      382
                                      300
                                       66
                                       99
                                       69
                                       62

                                       49

                                       42
Skewness

 0.02
 0.17
-0.
 0.
15
37
-0.07
 0.01
-0.77*
-0.65*
-0.29

 0.39

-0.04

-0.22
Kurtosis

-0.03
-0.36
-0.25
-0.73

-0.30
-0.38
 0.06
             0.37
             0.69
             0.20

            -0.47

            -0.26
 * probability <.10 given a normal distribution.

                                    A-5

-------
      Only  two  of the  twelve cases  indicated  significant  lack  of normality,
 confirming the conclusions  from the histograms.   It was  decided that  these
 two  cases  did  not merit  fitting of an alternative distribution at  this  time.
 These distributions will be addressed in  the final report when other  potential
 correlating variables are studied.

 A.3   Confidence Intervals for Percent Sources Leaking  and for Emission  Factors
                                     ^ •
      Confidence intervals for the  percent of leaking sources- were  computed
 using the  Binomial Distribution.   The Binomial  is used to model data  when a
 random sample  is selected and each item is classified  into  one of  two cate-
 gories (leaking or non-leaking  here).  Exact confidence  limits  (level 1-a)
 for  the estimate of percent leaking can be obtained by iteration solving  for
     Jji,   ? |  P x   (1 - P )n~1 -  a for the lower limit and for P  in
                                                                  U
                                     f°r the
                                   2
    i-o
where n = number of sources screened and k = number of leaking sources.
Tables of these solutions, available for most cases, were used to develop
95% confidence intervals reported in this publication and for computing  97.5%
confidence intervals which were used in developing confidence intervals for
emission factors.  97.5% was selected so that 95% confidence intervals for
emission factors would result when the estimated percent leaking was com-
bined with the estimated mean leak rate (.0.975 x 0.975 - 0.95)

     Patterson (1966) described how confidence intervals for the mean from a
lognormal distribution can be computed using estimators developed by Finney
(1941).  97.5% confidence intervals were computed for the average, y", of the
transformed data, y = In (.leak) , using

     CT = lower limit = y - 2.24 [ s2/(n-r) ]* and
      LI
                                             h
     0^ = upper limit = y + 2.24 [ s2/(n-r) P


where s2 is the variance of the transformed data and n-r is the number of
leaking sources.  Then, following Patterson's arguments, confidence intervals
for the mean leak rate can be computed using:

     lower limit = exp [CL]g(.s2/2)          and

     upper limit = exp [Cu]gCs2/2)

where g(t) is the series given in Section A. 2.


                                      A-6

-------
     To  obtain 95% confidence limits for the emission factors,  the  confidence
limits for  the percent leaking and for the mean leak rate were  combined  as
follows:

     lower  95% limit for emission factor = PT  (CT)
                                             ij   J_i

     upper  95% limit for emission factor = P  (C  )

These confidence intervals are conservative in the  sense that 95% is a
lower bound for the confidence coefficient for the  intervals.   The  confidence
intervals should be interpreted as follows:

      When  we state that the true emission factor falls  within  the
      limits computed as described above, we expect to be correct
      at least 95% of the time.

     The confidence intervals consider random sampling variation and random
test error, with no adjustments for potential bias  in the sampling  and ana-
lytical  methods.  Standards sampled and analyzed at most refineries have
not indicated any significant bias at this time,  but some results have shown
low recoveries ( <100%) .  A bias factor, if significant, will be computed
when all standards data becomes available.  To account for  potential low
bias at  this time, the upper confidence limits were increased 5% as follows:

     adjusted upper 95% confidence limit = P  (Cu)  + .05 (PU(CU))

In  addition to the above adjustment for all source  types, the upper and lower
confidence  intervals for compressor seals and  relief valves were adjusted to
compensate  for the potential bias due to estimating leak rates as discussed
in  Section  A.I.   The limits were expanded an additional  9-6% for relief valves,
17.5% for compressor seals in hydrocarbon service and  7.1% for compressor
seals in hydrogen service.

A.4  Development  of  Nomographs

     Three  types  of  nomographs were developed as part of this report:

     (1)  Predicting mean  leak  rate from screening values
     (.2)  cumulative percent  of  sources  for  increasing screening values
     03)  cumulative percent  of  total  emissions for increasing screening
          values.

This section describes  how these nomographs  were constructed.

A.4.1 Predicting Mean Leak Rate  from  Screening Values

     Section A.I  describes least-square  linear regression equations developed
for predicting leaks from  non-sampled  sources  in the data base with screening
values greater  than  200 ppmv.  For  prediction purposes outside the data base,
a statistical analysis  of  covariance was done  to determine if different
                                   A-7

-------
equations were required for the various source types and stream groupings.
The results of this analysis showed that one equation using the maximum
rescreening value was adequate for all stream types for pumps, compressors,
drains, and relief valves.  This does not imply that the leak rate versus
screening relationship is identical for these devices, but that the differ-
ences are small relative to the random scatter of the data.  For valves
and flanges, separate equations were required for the gas/vapor streams
and the light liquid/tw-phase and heavy liquid streams.

     The resulting equations are as follows:

I.   Valves and Flanges -  Gas/Vapor Streams

     LOGio  (.NMLEAK) = -7.0 + 1.16 LOGio (Max-rescreening)
     correlation =0.71      number of data pairs = 106
     standard error of estimate = 0.91 LOGio (NMLEAK)
     95% confidence interval for intercept (-7.9, -5.9)
     95% confidence interval for slope CO.94, 1.4)
     scale bias correction factor =8.59

II.  Valves and Flanges -  Light Liquid/Two-Phase  and  Heavy Liquid  Streams

     LOGio  (NMLEAK) - -4.8 + 0.76 LOGio (Max-rescreening)
     correlation = 0.76      number of data pairs = 147
     standard error of estimate =0.65 LOGio (NMLEAK)
     95% confidence interval for intercept (-5.2, -4.3)
     95% confidence interval for slope (0.66, 0.87)
     scale bias correction factor = 3.00

III. Pump Seals, Compressor Seals, Drains, Relief Valves

     LOGio  (NMLEAK) = -4.0 + 0.73 LOGio (Max-Rescreening)
     correlation = 0.62      number of data pairs = 168
     standard error of estimate = 0.82 LOGio CNMLEAK)
     95% confidence interval for intercept (-4.5, -3.4)
     95% confidence interval for slope (0.59, 0.87)
     scale bias correction factor =4.90

     The data used to develop these equations are shown in Figures A-l through
A-3.  These equations were used to develop the three sets of nomographs shown
in Figures 4-1 to 4-6 of this report.  Although the equations were developed
on a logarithmic scale, the nomographs are shown on an arithmetic, scale for
ease in reading and interpolation.  Predicting the arithmetic mean leak rate
for a given screening value is similar to predicting  the mean from a lognormal
distribution as discussed in Section A.2.   The mean value for a given
screening value on the nomograph was computed as follows.:

     mean = expio I B0 + Bj LOGi o (screening)]      g(  Ln/2)

          = (10) ° (screening value) l (scale bias correction factor)
                                   A-8

-------
 FIGURE A-l.   VALVES AND FLANGES - LEAK RATE/SCREENING RELATIONSHIP
                                  Gas/Vapor Streams
                                 LEGEND: A *  1 DBS, B - 2 DBS, ETC.

N
0
N
M
E
T
H
A
N
E

L
E
A
K

R
A
T
E

L
a
G

L
B
S
/
H
R


C
0. B +
C
C
C
0. 0 +
E
C
[
-o. a +
c
c
c
-1. 6 +
t
c
c
-2. 4 +
r
c
c
-3. 2 +
C
C A A
t A
-4. O + A
C A
C
C A
-4. 8 *
[
I
C
-5. 6 +



C
A
D
G
B
A A AA F
B
A A C
A H
A B E
A AA C
A AC
A A D
A A A A A
C
A A
AA B B
A A A
B A
A
•A
A A
AA
A A
A A





_, 	 + 	 —J 	 _J 	 a. 	 _ 	 J — _ 	 __J 	 4. 	 j._ 	 1 	
1.8    2.1     2.4     2.7    3.0    3.3    3.6    3.9    4.2    4.5    4.8    5.1     5.4

                       MAXIMUM SCREENING VALUE AT THE SOURCE LOG (PPMV)

-------
    FIGURE A-2.   VALVES AND FLANGES - LEAK  RATE/SCREENING RELATIONSHIP
                       Light Liquid/Two-Phase Streams
                                    LEGEND: A = 1 DBS, B = 3 DBS,  ETC.
N
O
N
M
E
T
H
A
N
E

L
E
> A
,L K
!—*
R
A
T
E

L
0
G

L
B
S
/
H
R


C
0. 8 +
t
t
C
0. 0 +
C
C
C
-0. B +
C
C
C
-1. 6 +
C
t
t
-2. 4 +
C
t
C
-3. 2 +
r
c
c
-4. 0 +
c
c
c
-4. 8 +
r
r
c
-5. 6 +


A
B


A A
A A B
A A
A B D
AA ED
B A A B A BB
A A B BB A E
A A B BA AA BA
A A B AAA A
A A B A A
A A B AA
A A
A A A A
C A B
A AA A
A


A



A A




B
F
A A
A
A C
A AD
A B
AA C
B
A A AA
AAA
A A






A










0. O    0.4    0.8    1.2    1.6     2.0    2.4    2.8    3.2    3.6    4. O    4.4    4.8    5.2

                         MAXIMUM SCREENING VALUE AT THE SOURCE LOG (PPMV)

-------
FIGURE  A-3.  PUMPS,  COMPRESSORS,  DRAINS,  RELIEF VALVES LEAK VS  SCREENING
                               All  Process  Streams
                                LEGEND:  A = 1  DBS,  B = 2 DBS. ETC.


N
0
N
M
E
T
H
A
N
E

L
E
A
K

R
A
r
E

L
0
G

L
B
S
H
R


C
1.6 +
C
C
I
0. 8 +
C
C
C
0,0 +
C
C
C
-O. 8 +
C
C
C
-t.fe +
r
c
t
-2. 4 +
t A B
L
C A
-3. 2 +
C A
C
C
-4. 0 +
C
C
-4. 8 +•
t
	 1 	 j 	



X

A
B
B B C
B
B A AD
A A A A AD A
A AA C
A A AA B C A A
B AA A A D
A BA A C A AA
AAA AABCAABAAAA D
A ABB BAAB
A BA AAA A AAA
A A A AB A AA AC AA A B B A A
AA AABA A A
A A AA A BAA AAA A
A A BB A C A A
A A A A B AA
A A D A
A B AA A

A A
A A
A A A
A



	 1 	 4- 	 H 	 h 	 h 	 + 	 4. 	 1. 	 4. 	 j 	


A
B
C
C
G
M
D
H
G
A A F
BBB A H
AB AA F
B F
C B

B
B















                      MAXIMUM SCREENING VALUE AT THE SOURCE LOG (PPMV)

-------
 where B0 - Log regression intercept
       BI - Log regression slope
       SET  - standard error of estimate in natural Log scale
       g It)- series described in Section A. 2.

 90% confidence intervals for the predicted mean leak for a given screening
 value were computed in a similar manner to the confidence intervals for the
 mean leak rate as described in Section A.2.

 A.4.2  Cumulative Percent of Sources for Increasing Screening Values

      The nomographs in Figures 4-7B to 4-16B of the report contain the
 estimated cumulative distribution of Log screening values.  The nomographs
 show 100% minus the cumulative percent, or the estimated percent of sources
 which would have screening values greater than any particular screening value.
 These cumulative distribution functions were estimated by fitting a lognormal
 distribution, as described in Section A.2, to the screening data and then
 generating the cumulative distribution.

      There was some difficulty in fitting the lognormal distribution to the
 screening values.  Figure A.4 shows a typical histogram of Log screening
 values for valves from gas streams.  The histogram appears to approximate
 a normal distribution adequately up to 10,000 ppm (4.0 on LOGio  scale).
 The spike at 10,000 ppm was due to the inability of the screening device
 to measure beyond 10,000 without a dilution probe.  The dilution probe was
 used in only a few cases in the screening process during this program.

      To overcome the bias caused by this spike,  only Log screening values
 less than 4.0 were used to estimate the parameters of this distribution.
 Formulas from "censored" normal distribution theory (Cohen,  1959) were then
 used to arrive at unbiased estimates of the entire distribution.  These es-
 timates were used to generate the cumulative distribution function for each
 source type/process stream grouping.

      Confidence intervals for these cumulative functions were obtained using
 the Binomial Distribution as in Section A.3.   The 95% confidence interval
 for individual probabilities were approximated using

                     e ± 1.96 tp ci-&)  /nf2

 where p is the estimated cumulative percent and n is the number of screening
 values for each particular source type and stream group.

      Assuming that the sources screened approximate a random sample from
 the population of a particular source type, these confidence intervals can
 be interpreted as follows:

      When we state that the true percent of sources in the population which
have screening values greater than any selected screening value lies within
the confidence bounds, we expect to be correct about 95% of the time.
                                    A-12

-------
w
S3
    i.
    i.
    i.
0.125
0.375
0.625
0.875
1.125
 ,375
 ,625
 ,875
2.125
2.375
2.625
2.875
3.125
3.375
3.625
3.875
4.125
4.375
4.625
4.875
0.374
0.624
0.874
1.124
1.374
1.624
1.874
2.124
2.374
2.624
2.874
3.124
3.374
3.624
3.874
4.124
4.374
4.624
4.874
5.124
                                       20
                                                30        40
                                                NUMBER OF VALVES
                                                             50
                                                                      60
                                                                               70
                                                                                        80
                                                                                                  90
                                    Figure A-4.
                DISTRIBUTION OF LOG 10 (MAX SCREENING VALUE)
                               Valves - Gas/Vapor Streams

-------
Note that these limits apply to the entire population for a source type and
are not necessarily applicable when addressing a particular situation con-
cerning a small number (say less than 100) of sources.

     The estimated cumulative distribution functions were compared with the
sample distribution function and appeared to fit the data for each case
except compressor seals.   Discrepancies were found at the 10,000 ppmv
screening value, in almost all cases, but this was to be expected since
the sample function had a big jump at this point.

     For compressor seals, censoring the data at 10,000 ppmv eliminated
64% of the observations,  so the lognormal parameters were reestimated
using all the data as recorded.  These estimated resulted in a "better"
agreement between the sample and estimates distribution function, and
were therefore used to generate the cumulative distribution function for
compressor seals in both types of service.

A.4.3 Cumulative Percent of Total Emissions for Increasing Screening Values

     The nomographs in Figures 4-7A to 4-16A of this report contain a
function estimating the cumulative percent of the total emissions attributable
to each particular source type/stream group as a function of increasing Log
screening values.  As before, 100% minus the cumulative function is shown
so that the percent of total emissions attributable to sources with
screening values above any selected screening value can be determined.

     This cumulative function was estimated by integrating the leak/screening
regression relationship over a lognormal distribution of screening values.
This function has the following form:
                                   exp [-(In x -u)2J  dx
                                            2a2
where So - selected upper screening value for integration
      C  - Log /arithmetic scale bias correction factor
      BO - Log 10 regression intercept term
      BI - Logio regression slope term
      u  - mean of the Log (screening values)
      a2 - variance of the  Loge (screening values)
      x  - screening values over which the integration is being done
      CF - cumulative function described above in Ibs/hr.

     The form of the cumulative function can be simplified by algebraic
reduction and change of variables to obtain.
[- "
L
        = C(10)B°  exp    "  - (" + Bia)2 1       LOG   (S0) - u -
                              2a2
                                    A-14

-------
where $ is the cumulative  function  of  a  standard normal distribution.

     This function was used in  developing the cumulative emissions function
shown on the nomographs.   The censored distribution parameter estimates
described in Section A.4.2 were used for the lognormal distribution para-
meters in each case except compressor  seals.  The Log/Log least-squares
regression estimates described  in Section A.4.1 were used for the scale
bias correction  factor and for  B0 and  BI.

     The scale for the above cumulative  function is in Ibs/hr.  To obtain
a cumulative percent function,  the  number obtained in Ibs/hr at each
screening value  was divided by  the  value of the function at a screening
value of one-million ppmv.   This forced  the cumulative function to 1.0 at
one-million ppmv.  These scaled values were then subtracted from 1.0 and
multiplied by 100.0 to obtain the functions shown on the nomograph.

     The estimated cumulative emissions  functions were compared with the
sample functions and found to adequately approximate the data in most
cases.  Again, the biggest discrepancies were near the 10,000 ppmv screening
value where the  sample function has a  big jump.  This area is more critical
for this function than the cumulative  distribution function since most of
the emissions are attributable  to sources with screening values greater
than 10,000 ppmv.  It is important  to  note that very little screening data
is available with screening values  greater than 10,000 ppmv.  Thus, this
portion of the curve is based on extrapolations using models developed
from screening values less than 10,000 ppmv.

     This cumulative function is a  very  complex nonlinear function of five
sample statistics:
                                                          j
      (1)  the intercept and slope from the regression of Log leak rate
          on Log screening value,

      (2)  a bias correction factor  used  when converting the logarithmic
          to the linear scale,  and

      (3)  the mean and variance of  the natural logarithm of the screening
          values.

Due to the complexity of this function,  it was not possible to derive a
closed-form analytical expression for  the  confidence intervals.  Thus, a
Monte-Carlo computer method was used to  generate the confidence intervals.

     This method involved  regenerating the cumulative function 400 times.
Each time, the data collected in the project  (the  exact number of  sources
with screening values greater than  zero) were  regenerated, except with an
independent set  of random  variations.  The distributional properties of
the leak rate and screening data were  used in  computing  the required random
numbers.
                                      A-15

-------
     For each of the 400 trials, sample estimates of the five parameters required
to compute the cumulative function were computed.  Then these estimates were used
to generate a new cumulative function.  The five percent lower result and the
five percent upper result from the 400 trials for any given screening value
were then selected as the 90% confidence limits for the population cumulative
function.  These approximated 90% confidence limits can be interpreted as
follows:

          When we state that the true percent of total emissions, for
     the population of sources, attributable to sources with screening
     values greater than a selected valve, is within the confidence
     bounds, we expect to be correct about 90% of the time.

Since these confidence limits address the uncertainty in the cumulative fun-
ction for the entire sampled population of a particular source type, they are
not necessarily applicable to a finite sample of sources in a particular sit-
uation.  The variation of this function depends on the number of sources in
a complex manner, so it is not possible to draw a general conclusion for the
effect of sample size.  Monte Carlo simulation techniques can be used to
approximate intervals for a finite random sample of a particular source type.

     As  an example, Figure A-5 shows the confidence intervals for the
cumulative percent of emissions functions for valves in light liquid/
two-phase service.  Intervals are shown which are applicable to a random
sample of 100 valves and a random sample of 1000 valves.  Also included
are the  confidence intervals for the entire population (from Figure 4-8A).
As can be seen, the intervals applicable to a finite number of sources are
significantly wider than those for the population.

     These intervals for finite populations were also developed using simu-
lation techniques.  Four hundred Monte Carlo trials generating 100 sets of
data and 400 trials generating 1000 sets of data were run.  In each of the
trials,  the generated sample was ranked according to screening values and a
sample cumulative leak rate function computed.  Each sample function was
scaled by dividing by the total leak rate generated.  Then the five percent
lower result and the five percent upper result from the 400 trials for any
given screening value were selected as the 90% confidence bounds.

     These confidence intervals can be interpreted as follows:

          When we state that the cumulative percent of total emission
     function, which would be generated from a random sample of "m"
     sources, will fall within the confidence bounds, we expect to be
     correct about 90% of the time.

where "m" is the number of randomly selected sources in a particular situation.
                                   A-16

-------
              Valves - Light Liquid/Two-Phase  Streams
100


 90


 80


 70
VI
!   60
LU
£   50


i°   40
<«_
o
c
01
                                        \
          - Estimated Percent of   \
                   Total Mass Emissions

          ---- 90% Confidence Interval    \
                                                 \  \\\
                   for Percent of Emissions    \   x  \ V
                   from Total Population of     \    \   \\\
                   Valves  (n = »)               \    \  \\\
    30
                       (n = »)

               •90% Confidence Interval
                for Percent  of Emissions
                in a Random  Sample of
                1000 Valves
          	90% Confidence Interval for
                   Percent of Emissions in a
                   Random Sample of 100 Valves
OJ
°-   20
    10


     0
                                  LJ	I
      1  2345 10      50100        1000      10,000     100,000    1,000,000

                         Screening Value (ppmv) (Log1Q Scale)
  Figure A-5.   Cumulative Distribution of Total Emissions by
                  Screening Values -  Valves  - Light Liquid/Two-
                  Phase  Streams - Comparison of Confidence
                  Intervals
                                  A-17

-------
                                REFERENCES
Aitchison, J., "On the Distribution of a Positive Random Variable Having a
           Discrete Probability Mass at the Origin",  American Statistical
           Association Journal. 50. C9), 1955,  901-908.

Cohen, A.C.,Jr. "Simplified Estimators for the  Normal Distribution when
           Samples are Singly Censored or Truncated", Technometrics 1,
           (1959) 217-237.

Finney, D. J., "On the Distribution of a Variate Whose Logarithm is Normally
           Distributed", Journal of the Royal Statistical Society.  Series B,
           7 (1941), 155-161.

Patterson, R. L., "Difficulties Involved in the Estimation of a Population
           Mean Using Transformed Sample Data:, Technometrics 8,  No.  3,  (1966),
           535-537.
                                   A-18

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                                TECHNICAL REPORT DATA
                         Iflease read Instructions on the reverse before ci
 EPA- 600/2 -79-044
                           2.
                                                      3. RECIPIENT'S ACCESSION NO.
         SUBTITLE
Emission Factors and Frequency of Leak Occurrence
   for Fittings in Refinery Process Units
             5. REPORT DATE
              February 1979
             6. PERFORMING ORGANIZATION CODE
                                                      8. PERFORMING ORGANIZATION REPORT NO.
 Robert Wether old and Lloyd Provost
*. •		-- ORGANIZATION NAME AND ADDRESS
Radian Corporation
P.O. Box 9948
Austin, Texas  78766
              10. PROGRAM ELEMENT NO.

              1AB604
              11. CONTRACT/GRANT NO.

              68-02-2147 and -2665
 12. SPONSORING AGENCY NAME AND ADDRESS
 EPA, Office of Research and Development
 Industrial Environmental Research Laboratory
 Research Triangle Park, NC 27711
              13. TYPE OF REPORT AND PERIOD COVERED
              Interim: 3/76 - 3/79	
              14. SPONSORING AGENCY CODE
               EPA/600/13
 15'SUPPLEMENTARYNOTESIERL-RTP project officer is Dale A.  Denny, MD-62, 919/541-2547
 i6. ABSTRACT Tne report gives results of sampling fugitive emissions at nine integrated
 oil refineries throughout the U.S. The petroleum refining industry is a significant
 source of atmospheric hydrocarbon (HC) emissions in the U.S.  Each refinery has a
 large number of potential emission sources, both controlled (e.g. ,  stacks and vents)
 and uncontrolled (e.g. , leaks). HC emission data were collected for valves, flanges,
 pump and compressor seals, pressure relief valves, and process drains.  The sam-
 pling techniques are presented.  Potential leaking components were initially screened
 using portable HC detectors; screened devices which indicate signifleant emissions
 were then subjected to fully qualitative and quantitative sampling and analysis. For
 the nine refineries, 5680 sources were screened, 1250 of which were sampled and
 analyzed. Data on non-methane HC emission rates are presented for each fugitive
 source, with statistics on data variability. Information on frequency of leaks is also
 provided. These data show that most HC emissions from fugitive sources occur due
 to a relatively few leaking components. Gas/vapor streams contribute a proportion-
 ately greater amount of emissions than the light and heavy liquid streams.
17.
                             KEY WORDS AND DOCUMENT ANALYSIS
a.
                DESCRIPTORS
                                          b.lDENTIFIERS/OPEN ENDED TERMS
                          c. cos AT I Field/Group
 Pollution             Sampling
 Petroleum Refining   Analyzing
 Hydrocarbons
 Leakage
 Flue Gases
 Vents
  Pollution Control
  Stationary Sources
  Fugitive Emissions
  Nonmethane Hydro-
    carbons
13B
13H
07C
14B
21B
13A
 8. DISTRIBUTION STATEMENT

 Unlimited
  19. SECURITY CLASS (ThisReport)
  Unclassified
                                                                   21. NO. OF PAGES
     78
  20. SECURITY CLASS (Thispage)
  Unclassified
                          22. PRICE
EPA Form 2220-1 (9-73)
A-19

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                               ACKNOWLEDGMENT


     Mr. C. D. Smith and Dr. D. D. Rosebrook of Radian Corporation are
also co-authors of this report.

     The authors wish to acknowledge the assistance of Dr. Dale Denny,
Dr. I. A. Jefcoat, and Dr. Bruce Tichenor of the Environmental Protection
Agency under whose guidance this program has been carried out.

     We wish to thank the members of the Ad Hoc Advisory Panel of the
American Petroleum Institute.  Their assistance in the formulation of the
program and their advice during its duration are greatly appreciated.  The
authors especially wish to thank Mr. Edward P. Crockett of the American
Petroleum Institute for his considerable efforts in support of the project.

     We are grateful to Mr. Herbert W. Bruch of the National Petroleum
Refiners Association for his  substantial assistance in this program.

     The data  upon which this  report is based were obtained at a number of
refineries throughout the country.  The assistance and exceptional cooperation
of  the  staffs  of  these refineries is gratefully acknowledged.

      It would  be  impossible to individually thank everyone on the Radian
staff who participated in this program.  Their outstanding attitude and
dedication have made this project successful.
                                     ii

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