p
p
p
p
p
p
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Unhed Slates
Environmental Protection
Agency
GR1-94/0257.29
EPA -eaO«-96 -0801
June 1996
                 501
                                                    PB97-l
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                               TECHNICAL ttEPORT DATA
                            e read In&Mctlmts 
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                                  FOREWORD
       The U. S,  Environmental Protection Agency is charged by Congress with pro-
       tecting the Nation's land,  air, and water resources. Under a mandate of national
       environmental laws, the Agency strives to formulate and implement actions lead-
       ing to a compatible balance between human activities and the ability of natural
       systems to support     nurture life.  To meet     mandate,  EPA's research
       program is providing     and technical support for solving environmental pro-
       blems today and building a science knowledge     necessary to         our eco-
      -logical resources wisely, understand how pollutants affect our health, and pre-
       vent or reduce environmental risks in  the future,

       The National Eisk Management Research Laboratory is the Agency's center for
       investigation of technological and management approaches for reducing risks
       from threats to human health     the environment.  The focus of the Laboratory's
       research program is on mettiods for the prevention and control of poEution to air,
       land, water,  and subsurface resources i protection of water quality in public water
       systems; remediation of contaminated  sites     groundwmterj and prevention and
       control of indoor air pollution.  The goal of this research effort is to catalyze
       development and implementation of innovative,  cost-effective environmental
       technologies; develop scientific and engineering information needed by EPA to
       support regulatory and policy decisions; and provide technical support and infor-
       mation transfer to ensure effective implementation of environmental regulations
       and strategies.

       This publication          produced as  part of the Laboratory's strategic long-
       term research plan. It is published and made available by EPA's Office of Re-
       search     Development to assist the user community    to link researchers
       with their clients.


                                 E. Timothy Oppelt,  Director
                                 National Bisk Management Eesearch Laboratory
                                 EPA

            This     has        and                    by the U.S.
            Protection Agency, and approved for publication. Mention of     names or
                     products     not        endorsement or             for yse,

            This document is available to the public through the National Technical Information
            Service, Springfield, Virginia 22161.
              INTERNATIONAL COPYRIGHT
ALL
NATIONAL TECHNICAL
U,S.           OF

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                               EPA-600/R-96-0801
                               June 1996
        METHANE EMISSIONS FROM
       THE NATURAL GAS INDUSTRY,
     VOLUME 12: PNEUMATIC DEVICES
              FINAL REPORT
                Prepared by;

              Theresa M. Shires
             Matthew R, Harrison

           Radian International LLC
             8501 N, Mopac Blvd.
              P.O. Box 201088
           Austin, TX  78720-1088
            DCN: 95-263-081-09
                    For

      GRI Project Manager: Robert A. Lott
         GAS RESEARCH INSTITUTE
          Contract No. 5091-251-2171
          8600 West Bryn Mawr Ave,
             Chicago, IL 60631

                    and

  EPA Project Manager:  David A.  Kirchgessner
U.S. ENVIRONMENTAL PROTECTION AGENCY
           Contract No. 68-D1-0031
  National Risk Management Research Laboratory
       Research Triangle Park, NC 27711

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                                  DISCLAIMEE

LEGAL NOTICED  This report             by Radian International LLC as an account
of work sponsored by Gas Research Institute (GRI) and the U.S. Environmental  Protection
Agency (EPA),  Neither EPA, GRI, members of GRI, nor any person acting on behaif of
either;

a.     Makes  any warranty or representation, express or implied, with respect to the
       accuracy, completeness, or usefulness of the information  contained in this report, or
       that the use of any apparatus, method, or process disclosed in this       may not
                       owned       or

b.              any liability with       to the use of, or for                      the
       use of,  any information,                   or                 in this report,

NOTE;  EPA's  Office of Research     Development quality  assurance/quality control
(QA/QC)              are applicable to      of the count              by this project.
Emission data  and additional count data are from industry  or literature sources, and are not
subject to EPA/ORD's QA/QC policies.  In all cases,  data and results were reviewed by the
panel of experts  listed in  Appendix D of Volume 2,

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 Title                      Emissions  from the Natural Gas Industry,
                  Volume 12: Pneumatic Devices
                  Final Report

 Contractor               International LLC
Principal
Investigators

Report Period


Objective
Technical
Perspective
Results
GM Context Number 5091-251-2171
EPA Contract Number 6S-D1-G031

Theresa M, Shires
Matthew R, Harrison

March 1991 - June 1996
Final Report

This report describes a study to quantify the annual  methane
from pneumatic  devices, which are a significant source of methane
          within the gas

The          use  of        gas has                as a        for
reducing the potential for global warming.  During combustion,
gas          less                (COZ) per unit of
      coai or oil.  On the      of the        of CO2        the
potential for global warming       be        by  substituting        gas
for coal or oil.  However, since natural     is primarily methane, a potent
greenhouse gas,  losses of natural gas during production, processing,
transmission, and distribution could reduce  the inherent           of its
lower C02 emissions.

To investigate this, Gas Research Institute (GRI) and the U.S.
Environmental Protection Agency's Office of Research  and Development
(EPA/ORD) cofunded a major study to quantify methane emissions from
U.S. natural gts  operations  for the 1992 base year. The results of this
study can be used  to construct global methane budgets  and to determine
the relative impact on global warming of natural gas versus coal  and  oil

The       national              for           devices for
industry segment are as follows; production, 31.4± 65% Bscf; gas
           0.60 ± 64% Bscf; and              14.1 ± 60% Bscf.
(Distribution          are           in another report.)
                                          in

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                  Based on data from the entire program, methane emissions from natural
                  gas operations are estimated to be 314 ±  105 Bscf for the 1992 base
                  year,   'This is about 1.4 ± 0.5% of gross natural gas production.  This
                  study also showed that the percentage of methane emitted for an
                  incremental         in natural gas      would be significantly  lower
                  than the baseline case.

                  The program reached its accuracy goal and provides an arcurate estimate
                  of                   that can be      to construct  U.S. methane
                  inventories and         fuel switching strategies,

Technical         Emission rates for pneumatic devices were determined by developing
Approach         average annual emission factors for devices used in each  industry
                  segment and extrapolating these data based on activity factors to develop
                  a national estimate, where the rational emission rate is the product of the
                  emission factor and activity factor.

                  The        gas industry has two primary       of          devices
                                     1} control valves              flow, and 2) gas-
                  actuated1 block valves,          each          of the industry follows its
                  own specific practices regarding "typical" pneumatic device  installations,
                  emission factors were developed based c.i the types of devices observed
                  from site visits.

                  Emission factor data for the various  device types were collected from
                          sources:                     provided from  other studies,
                  manufacturers*      and                    site visits,       collected
                         site      included: the         of      type of            device,
                               and        numbers,           conditions  (e.g., supply gas
                  pressure and supply  gas type),     annual  device actuation frequency.
                  Equations relating these parameters were developed for the different
                  types  of devices to develop  an annual emission factor for a generic
                  pneumatic device in each industry segment,

                  The development of activity factors for each industry segment are
                  presented in a separate report.  In  general though, the population of
                  pneumatic devices in each industry          was determined from counts
                  of devices                 site visits.  The                  for
                  industry         were            on the product of the emission  factor
                  for a generic           device and die activity factor.

Project           For the 1992      year, the        methane emissions         for the
Implications       U.S. natural gas industry L  314 Bscf ± 105 Bscf (± 33%),  This is
                  equivalent to 1.4% + 0.5% of 1992 gross natural gas production.  Results
                  from this program were used to compare greenhouse gas  emissions  from
                                           IV

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the fuel cycle for natural gas, oil, and coal using the global warming
potentials (GWPs) recently published by the Intergovernmental Panel on
Climate Change (IPCC).  The analysis showed that natural gas
contributes less to potential global warming than coal or oil, which
supports the fuel switching strategy suggested by IPCC and others.

In addition, results from this study are being used by the  natural  gas
industry to reduce operating costs while reducing emissions.  Some
companies are also participating in the Natural Gas-Star program, a
voluntary program sponsored by EPA's Office of Air and Radiation  in
cooperation with the American Gas Association to implement cost-
effective emission reductions and to  report reductions to the EPA, Since
this program was begun after the 199? baseline  year, any reductions in
methane  emissions from this program are not reflected in this study's
total emissions.
Robert A. Lott
Senior Project Manager, Environment and Safety

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                             TABLE OF CONTENTS

                                                                           Page

 1.0    SUMMARY  	I

 2.0    INTRODUCTION  	,	   2

 3.0    PNEUMATIC DEVICE CHARACTERISTICS  	   3
       3.1    Overview 	   3
       3.2    Gas-Actuated Control Valves  	 10
             3.2.1  Operating Principles	 10
             3.2.2  Data Requirements	22
       3.3    Gas-Actuated Isolation Valves	24
             3,3.1  General Description  	24
             3.3.2  Data Requirements	 29
       3.4    Other Pneumatic Devices 	29

4.0    PNEUMATIC DEVICE EMISSION FACTORS  	 34
       4.1    Production Segment	34
             4.1.1  General Emission Factor Characteristics  	 34
             4.1.2  Production Emission Factors	35
       4.2    Transmission and Storage Segment  	46
             4.2.1  General Emission Factor Characteristics  	46
             4.2.2  Transmission Emission Factors 	47
       4.3    Gas Processing Segment	55
       4.4    Distribution Segment	59

5.0    PNEUMATIC DEVICE ACTIVITY FACTORS  	 61
       5.1    Production Segment	61
       5.2    Gas Processing Segment	61
       5.3    Transmission and Storage Segment  	 61

6.0   NATIONAL  EMISSION RATE  	63

7.0   REFERENCES  . .	64


      APPENDIX A - Source Sheets 	 A-l
                                       VI

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                                 LIST OF FIGURES

                                                                                Page

3-1    Example of a Pneumatic Controller T'r.J for Level,
       Flow Rate, Temperature, or Pressure Control	5

3-2    Self-ContF ined,  Spring-Loaded Pressure  Regulator  	7

3-3    Pneumatic Device with Positioner - Force Balaace Piston Type  	8

3-4    Example Isolation Valve - Piston  Operator	   9

3-5    Operating Principles	  12

3-6a   Throttling Continuous  Bleed Pneumatic Controller —
       Orifice Flapper Design	  13

3-6b   Throttling Continuous  Bleed Pneumatic Relay -
       Ori%e Flapper Design	  13

3-7    Actuator Types  	  15

3-8    Force Balance P-ston Device	  18

Lt-9    Tli-ottling Continuous  Bleed Controller with Proportional Adjustment	19

3-10   On-Off Snap Devices  .	21

3-11   Pneumatic/Hydraulic Rotary Vane Operator 	26

3-12   Pneumatic/Hydraulic Rotary Vane Operator - Cross Section	  27

3-13   Turbine Op?rator	  28

3-14   Solenoid Reky	31

3-15   Self-Contained Pressure Regulation Valve   ,	32
                                         Vll

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                                LIST OF

                                                                             Page

3-1    Pneumatic Dsvice Classifications  ..,,.,,.	4

3-2    Typical Pneumatic Device              	,	,	  10

4-1            Uses of Pneumatic Devices ....,,.,	 34

4-2    Results from the Canadian  Petroleum Association Pneumatic
       Emission Rate Study	, ,	36

4-3    Manufacturer Bleed Rates for Continuous Bleed Pneumatic Devices 	 39

4-4    Measured Emission Rates for Continuous Bleed Devices	41

4-5    Summary of Production Site Data	 44

4-6    Production Emissi&a Factor Calculation	46

4-7    Pneumatic/Hydraulic Rotary Vane Isolation
       Valve	,	49

4-8    Manufacturer Data for Turbine Operated Isolation Valves	 52

4-9    Transmission Device Counts — Turbine     Displacement Devices  ......... 53

4-10   Transmission Device Counts — Continuous Bleed	 54

4-11   Gas Processing Site Emission Estimates for Natural Gas	 56

4-12   Gas Use Information for Pantex Devices  ,	58

6-1     Emission Rate Results	63
                                       VIM

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 1.0           SUMMARY

              This report is one if several volumes that provide background information
 supporting the Gas Research Institute and U.S. Environmental  Protection Agency Office of
 Research and Development (GRl-EPA/ORD)  methane emissions project. The objective of
 this comprehensive program is to quantify the methane emissions from the gas industry for
 the 1992 base year to within ±0.5% of natural gas production starting at the  wellhead and
 ending  immediately downstream of the customer's  meter.

              This report describes a study to quantify the annual methane emissions from
 pneumatic devices, which are a significant source of methane emissions within the gas
 industry.  The gas industry  has two primary types of pneumatic devices that  discharge
 natural  gas: control va'ves that regulate flow,  and gas-actuated isolation (block) valves.
 Because each segment of the industry follows its own specific practices regarding "typical"
 pneumatic device installations,  emission factors were developed based on the types of
 devices observed from site visits,  Emission factor data were collected from  several sources:
 measured emissions provided from other studies,  manufacturers' data, and data collected
 from site visits.

              The population of pneumatic devices in each -i.viustry segment was generally
 determined from counts of devices observed during site visits.  The national  emission factor
 for each industry segment was then based on  the  product of the emission factor for a
 generic  pneumatic device and activity factor.

             The annual emissions for pneumatic devices for each industry  segment are as
follows:  production 31.4 ± 65% Bscf; gas processing, 0.60 ± 64% Bscf; and  transmission,
 14.1 ± 60% Bscf.  (Distribution emissions are included in Volume  10 on metering and
pressure regulating  stations.1)
                                     PISTON ACTUATOR
                                             r*—•*<-  PNEUMATIC
                                             1        SiGNAL FROM

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 2.0

              A                  is a                           by      type of
 compressed gas. In the oil and gas industry, many devices, especially
 valves, are          by                    of                       the power gas (also
 called supply     to the atmosphere.

              This report is concerned with all "pneumatic devices," but focuses on  devices
 that release natural gas to the atmosphere, with the exception of gas-powered pumps and
 gas-powered compressor starters, which are characterized  in other parts of the GRI/EPA
 study,2'3'4  Also, it is important to note that some pneumatic devices do not emit gas. For
 example,  gas supply regulators and flow measurement devices such as Barton Chart
 recorders  and strip chart recorders  are        and do not bleed gas to  the atmosphere.

              The gas         has                  of pneumatic devices
 natural      1) control valves that  regulate flow,     2) gas-actuated  block valves.  Section
 3 describes           of pneumatic       and the          of      collection      for
 type of device.

              Section 4         emission        developed for each type of pneumatic
 device. Because each         of the gas  industry follows its own specific practices
 regarding  "typical"  pneumatic device installations,  this section contains separate discussions
 for each segment of the gas industry:  production,  gas processing, and transmission and
 storage.  Enissions from pneumatic devices in the distribution segment  are characterized in
 a separate report on meter  and regulation station emissions.'  Section  5 describes  activity
 factors for each segment of the gas industry, and Section 6 provides annual national
emissions calculated for each         of the gas industry.

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 3.0          PNEUMATIC  DEVICE CHARACTERISTICS

              This section describes the characteristics  of the various types of pneumatic
 devices used  in the natural gas industry, the data collected,  and the methods used to
 extrapolate 'the data.

 3.1           Overview

              Pneumatically operated equipment became the standard in the oil and gas
 industry since electricity  was not readily available at remote production sites.  Some
 pneumatic devices are powered by pressurized air from an instrument air compressor.
 However, the majority  of pneumatic instruments and valves in the gas industry are powered
 by natural gas.

              The pneumatic device can be used to move a valve or make a measurement.
 Most pneumatic measurement  devices in the gas industry  are sealed and do not emit natural
 gas unless they have a  defect.  However, many of these measurement devices send a signal
 to a control valve that regulates flow and thus controls process variables such as pressure,
 temperature,  flow rate,  and level. The controller for the control valve, if powered by
 natural gas, will discharge methane  to the  atmosphere.   In gas processing and transmission,
 isolation valves on large pipelines (also called block valves) can be actuated by natural gas,
whereas, most of the isolation valves in the production  and distribution industry segments
are operated manually.

              Table 3-1 presents the pneumatic device classifications  that will  be used  for
the purpose of this report.  The function that a control  valve affects, such as level, flow
rate, temperature,  or pressure, usually dictates the type of control device and therefore the
controller bleed rate. Pneumatic controllers linked to valves that control process
temperature, flow  rate,  or  level (Figure 3-1) bleed  gas.  The controller bleed rate may be
intermittent - alternating between bleeding  gas to the atmosphere and not bleeding gas  - or

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                                      34.
Valrc
Information

Function/Service
Level. Flow Rate,
Temperature, or
Pressure Control



Pressure Control
Isolation

•.::•.,;•:.• i ... \PnBBitJatic; Contftitter Information
Type '<£•::.
Control ' •
Snap-acting
ThrottliBg

Throttling
Throttling
N/A

:• -Controller Blecfl Frequency " ;
Intermittent
Stationary Bleed Rate = 0
Continuous
Non-zero Stationary Bleed
late

Intermittent
Stationary Bleed Rate = 0
No-bleed (discharges to
gas line)
Intermittent
Stationary Bleed Rate = 0
• Controller Bleed Rats '
. (upon valve actuation)
High rate, discharges
full volume of actuator
Small to large volume
discharged

Small to volume
discharged
No-Weed (discharges to
gas tine)
High rate, discharges
full volume of actuator
. Controller Device
Desi,ga
On-off
(Figure 3-10)
Orifice-flapper
(Figure 3-6)
Force-balance
piston
(Figure 3-3)
Self-contained
spring/diaphragm
(Figure 3-2)
Piston, rotary vane,
or turbine
(Figures 3-4, 3-11,
3-12, and 3-13)
Pneumatic Positioner*
Information

Bleed Status
N/A
Continuous or
intermittent

Continuous or
intermittent
N/A
N/A
Positioners are optional devices.

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                                       Actystor
                  tnnm uu ujrtnr

                   Valve

Figure 3-1.  Example of a Pneumatic Controller      for
  Level, Flow Mate, Temperature, or Pressure Control

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 the controller may continually bleed gas at various      (throttling).  Pressure controllers
 may       gas to the atmosphere, or may be self-contained (Figure 3-2), Self-contained
 devices bleed gas from a high-pressure  source to a lower pressure source without
 gas to the atmosphere.

              Throttling pneumatic control valves     be          with a valve positioner
 (shown in Figure 3-3), which is a type of mechanical feedback device            the actual
 valve stem position, compares it to the desired  position, and adjusts the gas pressure to the
 valve accordingly. In addition  to gas bleeding  through the valve controller, the positioner
 also bleeds gas to the atmosphere.

              Isolation valves are used to isolate a segment of pipe or a piece of equipment
 rather than for process  control.  An example  is shown in Figure 3-4.  The valve is either
 open or closed.  Gas is released only when the valve is moved, so the bleed frequency is
                        This type of          is fairly infrequent  The          for
devices            the       of the

              Table 3-2     the                   commonly used in the        gas
Industry      wnether gas would be emitted in             operation or during the
cycle.  This table            the bleed modes  of the various devices           in Table 3-
 1. The pneumatic device bleed modes and classifications are           in more detail in
the following sections.

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                                                   SET POINT
DOWNSTREAM
  PRESSURE
 GAS INTO
 REGULATOR
   DOWNSTREAM
     PRESSURE


;,OWER
GAS OUT OF
REGULATOR
            Figure 3-2. Self-Contained, Spring-Loaded Pressure Regulator5


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  VALVI
ACTUATOR
CONTROL
 VALVE
                                                                  SUPPLY
                                                                  S-li PSIQ
        Figure 3-3. Pneumatic Device with Positioner-force Balance Piston Type1

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                                     VALVE BODY
  SUPPLY
EXHAUST
  QAS
         ACTUATOR
  Figure 3-4. Example Isolation Valve - Piston Ojrs

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           TABLE 3-2,  TYPICAL
Pneumatic Device Type
Device
- Recording
- Control
Control Valve (Operator/ Actuator)
Valve Controller
- Snap-Acting
- Throttling
a. Force Balance
b. Orifice/Flapper
Valve Feedback Positioner
a. Force Balance
b. Orifice/Flapper
Self-Contained Regulators
Gas-Actuated Isolation Valves
Does the Device
Steady-State
Operations?
No
No
No
No
No
Yes
No
Yes
No
No
During:
Actuation Cycle
'(Valve
No
No
No
Yes
Yes
Yes
Yes
Yes
No
Yes
3.2
Cat-Actuated  Ccstrol Valves
3.2.1
Operating
              Pneumatic devices (valve controllers) linked to control valves are the largest
source of pneumatic emissions in the gas industry.  These devices can have two distinct
bleed modes:  a stationary bleed rate and an actuating bleed rate.  The stationary bleed is
the rate of gas released when the signal is constant, and the device is not moving.  For
intermittent bleed pneumatic controllers, the stationary  bleed rate is zero.  For continuous
bleed controllers, the stationary bleed rate is non-zero;  it is required to maintain a constant
gas supply to the device to provide for a quick response to changes in the controlled
process.
                                           10

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              When the pneumatic device is moving  the control valve, there is an unsteady
 and different rate of bleed (actuation bleed rate). If the signal is adding pressure to the
 actuating chamber, the bleed rate drops from the stationary  level.  If the signal  is to release
 pressure from the actuating  chamber, the bleed rate increases  above the stationary late.
 Actuating  bleed rates must be considered over a long period to determine average
 emissions.  Since the rate varies with the frequency of control, the actuating bleed rate is
 not available from the device manufacturers.

              Various parameters such as pressure, temperature, flow rate, and  liquid  levels
 are ali controlled by opening or closing a control valve  in the process line.  The necessary
 elements for controlling a parameter are a parameter measurement device, a valve,  a valve
 controller,  and possibly a feedback positioner.  For example, Figure 3-5 illustrates a device
 to control  the volume of liquid in a vessel.  A level float in the vessel indicates the  volume
 of liquid based on the level  measurement.  The measurement device sends a weak signal to
 the controller.  The  controller receives  the weak pneumatic signal  and converts  it to a
 stronger pneumatic signal which is sent to the valve actuator to move the valve stem.  The
 flow rate of liquid from the  tank is measured and recorded.  Each of the elements -
 measurement, valve,  and valve  controller - is described  in detail below.

              Measurement

              Weak signals from a measurement device are translated by sealed transmitters
 into P stronger signal  that can physically change valve position, and thus affect  flow
control.  For example, measurement of level using a level float produces a weak mechanical
signal that can be used to move the flapper shown in  Figure 3-6a.   Other measurement
media can  also serve as the controlling parameter.  For example, process flow is typically
measured by a drop in pressure across a restriction. The pressure  taps on either side of the
restriction  in the process flow are tied to a diaphragm that deflects when the pressure
changes. The deflection of the diaphragm produces a weak mechanical signal that can be
used to move the flapper (baffle) shown in Figure  3-6b.
                                           11

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                                                {SEA8UREMENT
                                                (LEVEL)
                              VALVE
Figure 3-5.             Principles
                    12

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                   r
                                                        PMEUflATIC
            PRESSURE
                        g§ PSI
                      AIR
L
                         0.01
                                                  ORIFICE
                                          SUPPORT PIVOT
                                                                     TO
                                          AN»
Figure 3-6a. Throttling Continuous Bleed Pneumatic Controller;  Orifice
                          Flapper Design5

                                   BAFFLE
                                           nm.


                                                    BESTRICTION
                                                    SB
                                                               OUTPUT
                                                               TO
                                                               ACTUATOB
  Figure 3-6b. Throttling Continuous       Pneumatic Mclay; Orifice
                          Flapper Design*

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              Valve
              Flow is          by a         valve.  The valve         by moving a valve
      and a valve             to the        The movement of the valve           the
 valve body can then restrict or stop process flow through the valve.  The stem can be
 moved  by any force method,

                    valves in the field are        by small electrical motors;  however, a
 pneumatic device is the most common.  In the      of pneumatic actuated valves, the
 is moved by force from the actuator chamber  The actuator chamber is either a diaphragm
 or a piston  device (see Figure 3-7), which deflects or moves because pressure is applied to
 one side of the          A permanent coiled spring        the valve  stem In the
 direction when the pneumatic force is reduced.  The valve     valve          never bleed
 directly unless there is a defect.  Emissions from such defects are considered fugitive
 emissions and are considered in the Equipment  Leaks7 report.  All actuation gas discharge
 is emitted back through the valve controller.

              Valve  Controller

              A valve controller is the device that  enables  a process variable to be changed.
The controller device links  the valve and the measurement  signal to produce a control loop,
The controller checks the current              of the variable against the desired set  point
of the variable.  If      is a difference, a pneumatic       is     to the control valve to
open or close the  valve. If the measurement  matches the set point,  equilibrium is
maintained  and  the s>:6nal holds a constant level. The controller may bleed  at the stationary
    depending on the design.

              In the field, the              device, valve, and valve controller are often
integral.  However, the controller  is the one element in the measurement/valve/valve-
controller loop that discharges gas to the  atmosphere.  Controllers are highly variable in
design.  Depending on  the        of the controller, the stationary position may or may not
                                           14

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               PISTON ACTUATOR
     POSITIONER —
PISTON
CYLINDER
                              PNEUMATIC
                              SIGNAL FROM
                              CONTROLLER
FEEDBACK
SPl  '!G
                                   -
                           VALVE SEAT
             _PIAPHRAGM_ACT»ATOa

                       I—

                                            HEIGHT
          Figure 3-7, Actuator Types*
                      15

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 involve a continuous bleed rate.  However, the actuation  cycle, which is the actual
 movement or stroke of the valve stem from open to closed and back, always results in the
 release of gas.  This cycle only occurs when -the signal changes and control  is needed.  The
 frequency of this occurrence will be different for every application.

              Pneumatic Relay

              The key component of the controller is the pneumatic relay  (also called a
 booster, transmitter, or amplifier).  In the simplest case, a controller is only a supply gas
 regulator and a pneumatic relay.  Since the signal from the measurement device is usually
 weak, it can not produce enough force to open the valve.  A controller device amplifies the
             a higher-pressure supply gas.  The supply gas is often taken directly from the
 produced  gas at the field site.

              The pneumatic relay Is a kind of mechanical amplifier that produces a
 stronger pneumatic signal.  The mechanical amplifier in the controller uses the small force
 of the measurement deflection to change the supply  gas flow path, which alters the resulting
 downstream  supply gas pressure.  The change in pressure  is a pneumatic signal that is sent
to the valve actuator. Controllers      not       at all when      is an
An                       higher-pressure gas into the actuator, deflecting the diaphragm
and             the spring.  When the                 the          reduces the  i^ssure
on the actuator by          gas to the atmosphere.

              There are several types of pneumatic relays which, as the  main component of
the controller, define the type of controller. The most common are throttling and snap-
acting.  Throttling implies     the valve can be moved to any position proportional to the
signal.  These devices are most often used for their quick          to system         or
            precise         is
                                           16

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              A simplified drawing of a throttling controller's pneumatic relay shows one
method that a pneumatic device may use to change a weak mechanical        into a
stronger pneumatic        (Figure 3-6b).  Basically, the pneumatic device       a
amount of                  to alter the flow  and         of a supply gas at higher
pressure.  This higher pressure stream then becomes the amplified control signal.  The
higher          gas         is "altered"  by        partially diverted through a       orifice
that bleeds  to the atmosphere.  The weak mechanical signal moves a "flapper"  that alters
the flow of gas  out of the orifice.  If the flapper is fully extended towards the orifice, the
device bleeds at a very low rate, and the pneumatic output is at its highest level,  If the
orifice is fully open, most of the supply stream bleeds  to the  atmosphere, and the pneumatic
output is at its lowest value.  This type of throttling device has a  continuous  bleed rate,
even in the stationary position (no movement of the valve or  change of signal) because the
orifice opening  is not completely  closed.

              Figure 3-6a shows that a small  mechanical  force can be used to deflect a
flapper          covers or uncovers an  orifice,          the gas supply  into an. amplified
measurement         Other types  of pneumatic       uce a chamber         of an orifice
flapper apparatus.  The most common chamber relay is called a "force balance piston
device,"  One              shown in Figure 3-3, and another is showa in Figure
3-8, This type of device only bleeds when it is out of the neutral position;  its continuous
bleed     is zero,

             In addition to the primary relay amplifier, many throttling controllers have
adjustment devices that allow the  operator to alter the set point and response  (proportional
gain, proportional-integral  gain, or proportional-integral-derivative gain), and  devices that
allow the controller to be reset.  These  additional devices may also bleed gas, but their rates
are steady and are included in the manufacturers' reported total gas consumption rate for
the controller. Figure  3-9 shows a device with a proportional  set  point     reset knob.
                                           17

-------
    WEAK
   APPLIED
    FORCE
3-8. Force Balance      Device1
        18

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CONSTANT SUPPLY PRESSURE
INLET EHB OF
RELAY VALVE

SMALL DIAPHM&M

LARGE DIAPHRAGM





PIVOTIM8
                                EXHAUST

                     END OF      VAiVI
                                                  OR
                                              LGSDiNG

                                                    NOZZLi PRESSURE

                                                    PROPORTIONAL
          Figure 3-9.  Throttling Contimooiis Bleed Controller with Proportional

-------
This knob contains  an exhaust port with a continuous bleed line from the actuator
diaphragm.  These additional bleed locations are typical of proportional controllers.

              For throttling controllers,               car.        for any              rate
by sizing the orifice        or the force         piston relay.  In         devices with a
lower         bleed      are slower to         to       changes, and have longer response
times; therefore, some applications that require fast response also require higher bleed rates.

              Snap-acting controllers are another type of device common to the gas
industry.  A snap-acting or "on/off device is either fully open or fully closed.  A snap-
acting controller has no continuous  bleed, it only bleeds when the actuator is depressured.
Figure 3-10 shows two examples of on/off relay devices. As the diagram shows, when the
device is on,  the full supply-gas  pressure is applied to the control valve actuator, and the
vent/exhaust line is  blocked off.  When the device is off, the actuator is vented to the
atmosphere     the  supply gas is blocked off,

                                    an           feedback device: a valve
measures, amplifies, and      a                    the position of the valve stem.  These
positioner         Introduce a second           relay device to the         control loop;
therefore, a second  bleed rate can also be introduced.  Positioners are typically used for
"slow systems"       as             control, where more precise movement of the valve is
needed.

              Figure 3-3 illustrates a force balance spool relay and the valve positioner that
the relay controls.  These devices can be easily  identified in the field by the positioner  arm
attached to the valve stem. Only a small percentage  of control valves in the gas industry
have positioners since this  level  of fine tuning is not generally required.
                                            20

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ON/OFF SNAP
       WEAK
      APPLIED
       FORCE
      WEAK
      APPLIED
      FORCE
                           SUPPLY
                             GAS
                        «~ TO/FROM
                          ACTUATOR
                             PORT
PNEUMATIC SWITCH
                                  VENT
                                   GAS
                                 TO/FROM
                                ACTUATOR
                                                    SUPPLY
                Figure 3-10.  On-Off Snap Devices5
                              21

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 3.2.2
Data Requirements
              As mentioned  in the previous section, pneumatic controllers can have two
distinct bleed modes, based on the type of relay.  There is an actuating Weed rate and a
stationary  or steady-state bleed rate.  The  stationary  bleed rate occurs  when the signal is
constant     the valve is not moving; the  actuating rate occurs       the  valve          is
depressured.  The stationary  bleed      for a device     be zero, depending  on its
              However,                  controller has a non-zero

              The various characteristics that can affect the stationary bleed  rate for a
production controllei are;
              1.           device type (controller, positioner, self-contained device);
              2.     Pneumatic relay construction  (orifice-flapper       force         pis-
                     ton, number of Internal control adjustments, such as proportional
                         set point »caobs);
              3.     Device condition (old or worn devices may leak more);
              4.     Design response time (faster response devices require higher bleed
                     rates); and
              5,     Supply gas pressure and supply gas type (air produces no
                     emissions).
              All controller types      an                rate.  The actuation       occurs
when the controller moves the valve stem by either releasing pneumatic pressure or
applying pneumatic pressure.  As the pneumatic pressure is released, the actuator must be
vented.  The venting occurs through the controller  device.

              For throttling controllers  with                  rates, the           will
         above the stationary level so     the actuator can be depressured.  For all
                                            22

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throttling controllers, actuation bleed rates depend on how far and how often the valve is
moved, and must  be considered over a long period to determine average emissions.


              For snap-acting valves,  the actuating bleed depressures the entire  actuator to

the atmosphere.  The actuation Weed rate depends on the  size of the device and on how

often the valve is moved.


              The various parameters  that can affect the yearly average actuating bleed rate

for a snap-acting or throttling device are:


              1.     Number of full stroke - rtes per year (how often the valve makes a
                    full stroke cycle);

              2.     Actuating chamber size; and

              3.     Supply gas pressure.


              Based on the characteristics  of continuous bleed and intermittent bleed

pneumatic  devices, the following approach was used to gatl ".r pneumatic data from site

visits for this report:


              1.     Basic device type (intermittent versus continuous bleed), the
                    instrument manufacturer,  and model  number were gathered from
                    several sites by visual inspection;

              2.     Instrument populations;

              3.     Supply gas pressure and type; and

              4.     Field measurements of continuous  bleed devices were provided  from
                    existing sources.



              The bleed rate will vary with the supply gas pressure.   The two common
signal pressure ranges are:  1) 3 to 15 psig; and 2) 6 to  30 psig.5 These supply  ranges can
                                           23

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be easily identified  by the gauge dials on the front of the controller box.  The 3-15 range
will operate at approximately 20 psi gauge; the 6-30 range  will operate  at about 35 psi
gauge.

              The site data were combined  with manufacturers' data and field
measurements (provided from existing sources)10'"  to produce an annual estimate of
emissions for intermittent and continuous bleed actuated controllers.

3.3           Gas-Acttiated  Isolation Valves

              Transmission compressor stations, transmission pipelines,  storage stations,
and gas plants have large-diameter pipelines, and therefore  have large pipeline isolation
valves.  These valves block the flow to or from a pipeline,  and can isolate the facility for
maintenance work or in the case of an emergency.  The valves are usually actuated
remotely by a power source.  The valves are so large that manual operation  would be
extremely slow, and certainly unsuitable in the case of an emergency. The valves are most
often actuated pneumatically (by natural gas or compressed  air) or  by an electric motor.

3.3.1          General Description

              Most  gas operators on isolation valves discharge gas only  when actuated.
Once they reach the open or closed position, they do not bleed gas.  These valves are
actuated  infrequently, so their emissions  are very intermittent.

              The pneumatically actuated isolation valves can generally  be divided into two
types:  1) displacement operators, and 2) turbine operators.  Displacement  operators are
attached  to  quarter-turn plug valves or quarter-turn ball  valves.  These operators  use  gas
pressure  (pneumatic force) to move an actuator element in one direction.  Sometimes the
pneumatic force is applied directly to the actuator element,  and  sometimes it is applied to
oil, so that hydraulic force moves the actuator;  in either case, gas is discharged when the
                                           24

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 valve Is actuated.  The actuator element is displaced from its original position by tfte
 pneumatic or hydraulic force.  Displacement  operators in the gas industry are of two basic
 types: 1) rotary vane, and 2) piston.

              The rotary vane displacement operator uses natural gas to force a fixed
 amount of oil from    pressure bottle to another.  The oil moves through she vane
 operator, delivering hydraulic force to the vane,    moving it      the attached  valve stem
 one quarter turn.  The oil moving into the bottle forces gas in the top of the  receiving
 pressure bottle to vent to the atmosphere.  The most common manufacturer of this  type of
 operator is Shafer Vaive Company.12  Figures 3-11  and 3-12 show a typical pneumatic/
 hydraulic rotary vane operator from the Shafer catalogue.

              Similarly,        Valve          & Systems, Inc.,              a displace-
              that            gas to       a piston,6  The            en an "arm" or lever
           the valve       Gas is         to one     of the       and          from the
 other to move the arm in each direction, either opening 01 closing the valve.  An example of
 this type of operator  is shown in Figure 3-4.

              Supply gas for     operators is usually pipeline gas, so pressure varies from
 site to                  air can be      if it is         in          volumes. The volume
of gas               on the      or                       and on the supply gas
pressure.

              Turbine operators, the second major type of isolation valve operators, are
usually attached to gate valves.13 The turbine operators simply release gas  to the  atmosphere
across a small turbine similar to a gas starter turbine for a reciprocating compressor.  The
gas      the turbine blades, and the turbine shaft then turns       that move the      valve
stem.  A turbine         on a      valvi is          in Figure 3-13.
                                           25

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Figure 3-11. PB€umatici«Iydranlk Rotary Vane Operator12
                          26

-------

                                       HAND      FOR MANUAL
                                       OPERATION
Figure 3-12. Pneumatic/Hydraulic Rotary Vane Operator - Cross Section12
                                27

-------
BOI

         GAS IN
          Figure 3-13.  Turbine Operator
                      28

-------
              Pipeline gas is typically used as the supply gas for the turbine devices, so the
 pressure varies from site to site.  The volumes vented depend on the duration of operation to
      or      the valve and on the supply gas pressure.

 3,3.2         Data Requirements

                     upon the                             above, the various
                   affect the          for         valve          are:

              1.     Basic device type (turbine or displacement);
              2,     Manufacturer ?nd model number;
              3,     Supply gas pressure, supply gas type {air         no
                               and
              4.     Number of full        cycles per year.

              The following approach was used to gather pneumatic data for  this report from
     site
              I.     During site visits, instrument populations and the instrument
                    manufacturer and model number were gathered from several sites; and
              2.     Based oa observations and interviews, the frequency of operation cycles
                    per year     estimated.
              The site data were combined with manufacturers*      and measured data from
other studies to produce an emission factor for a typical device type.

3.4           Other Pneumatic

              Numerous other devices in the field can bleed methane but do not neatly fit
into the categories listed above.  Because these devices are rare,  or rarely bleed, they were
                                           29

-------
 ignored for the purpose of this study.  They are       in this section only for the      of
 completeness.  Some key examples are:

              8      Solenoid snap-acting valve controllers;
              »      Self-contained         regulators;
              *      Pneumatic transmitters; and
              »      Older flow computers.

              The solenoid "snap-acting" controller acts like the pneumatic snap-acting
 controller, except that its signal is not a weak mechanical signal but an electrical one.  The
 solenoid either opens a valve that puts full supply gas pressure  to the top of the valve
 actuator or closes off     supply and vents the actuator to the atmosphere.  Like snap-acting
          relays, it only              the         is             Figure 3-14       a
        of a          relay.  These         are                           are
     in the gas industry,

              A common example of a self-contained pressure  regulator is the small "gas
supply regulator" shown in Figure 3-2, This is a small device  that lowers pneumatic gas
supply         to a        downstream pressure.  These devices are commonly found
                                 and the            use the              Gas supply
regulators only bleed if the                                 set-point. Since      are
                  of the gas, the                     is              lower, so
devices rarely bleed gas.  Another common, large,  self-contained device is the transmission
and distribution pressure letdown regulator (Figure  3-15), These regulators handle the entire
gas stream but do not bleed at all. They release actuator pressure to the downstream side
and do not bleed  to the atmosphere.
                                           30

-------
   FRCm
 ACTUATOR
   TO
ACTUATOR
                          DE-ENERGIZED;
                        TO VENT
(SUPPLY OAS
IS BLOCKED)
                                                        ELECTRONIC
                                                           SIGNAL
                                                    	I
                                                        ELECTRONIC
                                                          SIGNAL
                                                              I
                                                              I
                                                         	1

                                                          (SIGNAL IS ON)
  SUPPLY GAS
                        (VENT IS
                        BLOCKED)


                         Figure 3-14.  Soieaoid Relay5
                                     31

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3-15.                                   ¥alve
                  32

-------
              The pneumatic transmitters and older flow computers are examples of devices
originally installed in older facilities that are out-of-date by today's standards of technology.
It is difficult to list, characterize, or group all of the diverse devices  in this category.  Their
total contribution to emissions is considered to be minimal.
                                            33

-------
 4.0

              The various segments of the gas industry have different equipment and
 different standards for using pneumatic devices.  Table 4-1 shows the general uses of devices
 in each segment.

 	        4-1.                     OF
                     "Production                -Transmission    Distribution
    Control valves        Yes       Very Few        Yes             Yes
   operated by gas?
    Isolation valves        No          Some          Yes            Some
   operated by gas?

 The                             the       of                 in              and the
                         with       devices.

 4.1          Production Segment

             Valve controllers (pneumatic devices on control valves that regulate flow) are
 the                  of                in the production                      gas to
 the             As       earlier,                     devices,             the initial
       in the         variable, are       and do not directly      or        to the
atmosphere.  In addition, the production pipelines are small, so the isolation valves that
are manually operated and do not Weed gas.

4,1,1        General Emission Factor Characteristics

             Typical
Infrequently,                                 valve positioners.  There are
components (such as set-point adjustment, gain adjustment, and      knobs) within a
                                          34

-------
 controller or positioner that may bleed.  These are considered part of the controller device.
 Certain valves or valve packages may have these emitting elements combined into one field-
 located box.

              The production                             of           controllers;  1)
 throttling, and 2)             Throttling           relays of the  "force        piston"
 (Figure 3-8)      only when they move from the       position. They are
            emitters and      a                    of zero.  Throttling orifice
 relays (Figure 3-6) bleed continuously, even when the valve is not moving, but their bleed
 rate varies with the strength of the signal from the process  variable.  Orifice flapper relays
 are considered continuous emitters since there is no position where the Meed rate is zero.
                           a                    of     and are         considered


 4.1.?         Production

              Five sources of information were used to determine the methane emissions
 from pneumatic devices      in the production segment: the results from a study performed
 by the Canadian Petroleum Association,11 manufacturers' data,           emission rates,10
     collected from     visits, and literature data for         composition.  Each of
 sources is discussed in detail,

              Canadian Petroleum  Aisociation (CPA) Report

              As part of Canada's effort to reduce atmospheric emissions, the Canadian
Petroleum                      a project to quantify         and VOC          in
upstream oil and gas operations.11                        from  19
devices and 16 throttling         were collected during this study.  The       are
in Table 4-2.  The         natural gas emission     for snap-acting devices     213
scfd/device  ±57% (90% confidence interval),  and the average emission rate  for throttling
                                           35

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TABLE 4-2. RESULTS FROM THE CANADIAN PETROLEUM ASSOCIATION PNEUMATIC
                        EMISSION RATE STUDY
• : • ' .



' -\ •;.•:;:."• ',•;•'•::•.-•''• , . • • ' ^is'j :-'f ;: ' /'Quantity Minimum Flow, -
-.-• InstruBteni Type '''
Snap-Acting
Controller











Throttling
Controller





*} F-atipty Type - EqaipmenfT-ype' . ': Measured
Oil Battery Group Treater
Test Treater
Group Treater
Group Treater
Group Treater
Group Treater
Group Treater
Group Treater
Group Treater
Test Treater
Test Separator
Group Separator
Average Emission for Snap-Acting
Oil Battery Dehydrator
Line Heater
Line Heater
Line Heater
Group Treater
Test Separator
Test Separator
1
2
1
2
2
2
2
1
1
2
2
1
Controllers
3
1
I
1
6
1
3
'• 'scfd
0.0
172

0.0
0.0
0.0
0.0
0.0


0.0
0.0

0
55
11
31
7
529
9

• Maximum Plow,
- scfd
690
172

>95I
>933
>959
573
>1,911


430
1397

10
55
11
31
7
529
240
Average Emission for Throttling Controllers
Average Natural
Gas Emission,
scfd
33
179
14
226
59
140
81
695
12
210
233
677
213 ± 57%
2
60
U
34
8
529
11
94 + 152%

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 devices     94 scfd/device ±  152%," The CPA report concluded               no
 statistically           difference between the           of the            and throttling
 controllers.

              It should be noted that the CPA report did not distinguish between throttling
 controllers with intermittent bleed rates and throttling controllers with continuous bleed rates.
 In addition, only one of the throttling devices actuated while they were measuring it.  The
 measurements recorded for the other throttling devices only represent the stationary or
 continuous bleed emissions.14 Therefore,  the Canadian measurements are lower than field
 measurements of similar devices in the U.S., but do agree with the manufacturer's data for
 similar devices.  The CPA measurements  were treated as additional data sources and
 combined with field measurements provided by another source to         emission factors
 for            and continuous bleed devices.10

              Manufacturers*

                            of                      report a "gas consumption" for
specific devices      on laboratory       of     devices. However,  the manufacturers
indicate               in the field can be             the reported gas consumption due to
operating conditions, age, and wear of the device, 15'i6'"-ls  Examples of circumstances or
factors that can contribute to this increase include:

              8     Nozzle coiTosion resulting in more flow  through a larger  opening;
              «     Broken or worn diaphragms, bellows, fittings, and nozzles;
              •     Corrosives in the gas leading to erosion or corrosion of control loop
                    internals;
              *     Improper installation;
              *     Lack of                                  replacement of the filter
                         to remove       From the supply gas and             of o-rings
                    and/or seals);
                                           3?

-------
              •      Lack of calibration of the controller or adjustment of the distance
                     between the flapper and nozzle;
              »      Foreign material lodged in the pilot seat; and
              •      Wear in the seal seat.

              The manufacturers contacted did  net have  field measurements of devices in
service and did not simulate the  aging of devices with laboratory measurements, so they
coiild not provided an indication of the. expected increase in emissions due to the factors
listed above.  Since manufacturers' emission rates are based on new devices, actual emission
measurements from pneumatic devices in field service, including worn or defective devices,
were used as the basis for developing emission  factors.1041

              Several pneumatic device manufacturers provided information on the gas
consumpti >n rates for their continuous bleed devices.9'16-18'19'20'21'22'23'24'25  Table 4-3 shows the
bleed rates for the model series observed during site visits.  The manufacturers'  reported gas
consumption rates represent the gas usage at the specified supply gas pressure for the
controller only (unless otherwise noted).  Additional emissions may occur from other
components of the control loop (i.e., set point exhaust and valve positioner).

              For the types of de vices listed, gas consumption rates for the controllers can
vary from  0 to 2,150 scfd per device. However, the manufacturers indicated that emissions
from these devices in field operation  may be higher than  the reported "maximum,"  Some
manufacturers provided a maximum gas flow rate or delivery capacity that the controller
pilot could withstand (4,320 scfd for  the Bristol 624II and 8,880 for the Fisher 4100).  This
flow rate indicaits the maximum amount of gas that can be supplied to the control loop. It is
possible ths: .-xnsje pneumatic  devices could continue to operate up to these flow rates,  but
TT-:-I ji'tK.'ve the4,£ rates.

              The manufacturers' data serve as a sanity check for  the field measurements
provided by other sources (discussed  in the next section).  The data reported in Table 4-3 are

                                           38

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4-3.                             FOE
Manufacturer/
Model
Norriseal 1000 (A)
Norriseai 1001 (A)
Bristol 624, 624 II
Fisher 2400
2500
Fisher 2900
Fisher 4100
Invalco AB 155
lavaleo CT series
' Gas jbodiswnptibn, • Rates ; ': Scfd
"Minimam"
"Marinaum"
Mode! discontinued in the 1960s
0-10
72-144
2,150
4,320
Model discontinued in 1957
168
1,008
Model discontinued in 1991
24
1,200
8,880
Model discontinued — 1975
510
960
Comments on Specified Rate
No bleed rate information available.
Max. bleed rate is not specified by Norriseal. Es'irriated for 1001 model ba.;ed
on volume of gas required for one complete actuation @ 30 psig supply
(provided by manufacturer) and assuming one actuation/min.
Min. on gas consumption of the controller only.
Bristol does not manufacture actuators, so they do not specify a gas consumption
for the actuator. Max. bleed rate shown is based on the pilot capacity
(maximum amount of gas that the controller pilot can accommodate).
No bleed rate information available.
Bleed rate for 35 psig supply pressure. Min. represents the steady state pilot
bleed (device not actuating). Max, represents gas consumption when the
relay is completely open.
Gas consumption not listed in device brochure, but Fisher representative
provided a laboratory measurement of 555 scfd for 35 psig supply pressure.
Bleed for 3S psig supply pressure. Min. represents the steady state pilot
bleed rate of the controller. Max. represents maximum gas consumption (1200
scfd) and delivery capacity of the controller (8800 scfd).
No bleed rite information available.
Minimum bleed rate specified for supply gas pressure of 20-30 psi. Maximum
bleed rate shown here is reported by the manufacturer as a typical bleed rate for
Ibis device, A retrofit kit is available for this series of devices *D reduce the
typical bleed rate from 960 scfd to less than 22 scfd.

-------
 consistent with emission measurements in the field, in that the manufacturers confirmed that
 the        can     at                 the manufacturers*         gas consumption rates,
 In addition, the delivery capacity reported by the manufacturers for some devices serves as
 an absolute maximum Meed rate. Any measured emission     higher than the deliver}'
         for a given device       indicate an error in the             and would justify
 discarding the measurement.

                                           for Continuous

              Field              of          devices with
 available from companies participating in a         contractor's program,10 For
 measurements, a contractor connected a flow meter to the supply gas line between the
         regulator and  the controller to         the gas             of the controller,  A
 cumulative flow rate and the current flow (scfh) were recorded and extrapolated to gas
 consumption per day.  ""he duration of the test depended on the variability of the gas use,
 For                 conditions, one                    for 15-20 minutes.  For
 flow rates, several one-hour measurements were taken.

                       the                            not performed under the direction
 of this study, the results are believed to  be an accurate representation of pneumatic devices in
 operation In the U.S.        gas industry. Through           with site           and the
contractor               the measurements,10 the
protocol, and equipment calibration procedures were reviewed.  Two measurements were
              the      set because     did not follow the                      for a
device (in both      a sinyle                          reported for an unknown        of
devices).  The final data set was deemed acceptable by the industry review  panel.

             After the QA/QC review, the     set contained a     of 41 measurements
from a combination of  continuous bleed  devices from offshore platforms, onshore production
sites, and                      Table 4-4            the
                                          40

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 TABLE 4-4. MEASURED EMISSION RATES FOR CONTINUOUS BLEED DEVICES
Production Production Total
Onshore Offshore Production Transmission
Number of
Measurements
Minimum,
scfd/device
Maximum,
scfd/device
Average,
scfd/device
9 9 18 23

380 108 108 152

2,334 962 2,334 4,215

1,189 ± 39% 556 ± 33% 872 + 30% 1,363 ± 29%

              The use of pneumatic devices in onshore versus offshore production operations
is similar.  Both use continuous bleed devices primarily for liquid level control in separators.
Comparing the average measurements in Table 4-4, the average emission rate for pneumatic
devices in offshore operations is much smaller than the emission rate for these devices in
onshore operations.  However, the offshore emission measurements shown in Table 4-4 are
from one company.  Therefore, any difference between onshore and offshore device
emissions might also be attributed to a company difference.  Because most industry reviewers
of this study believe  that there is no technical  reason to divide the data set between onshore
and offshore, and additional data were not available to validate a distinction between onshore
and offshore, the measurements for these  two  categories are combined into one emission
factor for continuous bleed devices in the production segment.

              Continuous bleed pneumatic devices are used for different functions  in
production versus transmission operations. As mentioned previously, most continuous bleed
pneumatic devices  in production are used  to control the liquid level in separators. In the
transmission segment, the same types of devices are used for liquid level control in filter-
separators, but are also used for pressure  reduction.  In addition, the higher pressures and
larger pipeline sizes associated with transmission operations require larger actuators and
                                          41

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 larger valves than are typically found in production, and therefore pneumatic devices used in
 transmission operations would be expected to result in higher emission rates. For these
 reasons, separate emission factors were developed for production and transmission.

              Comparing the measured emissions for devices in production versus
 transmission indicates that there is a difference between the industry segments.  The
 combined onshore and offshore production devices have a lower average emission rate of 872
 scfd, while transmission devices have an average emission rate  of 1,363 scfd.  When the
 Canadian data are included, the production emission factor is 654  ±31% scfd/device.  The
 transmission emission factor is unchanged because the Canadian measurements were only
 from onshore production facilities.

              The measured emission rates compare well with the gas consumption ranges
 provided by the manufacturers, although a direct comparison for all device types can not be
 made since manufacturer values are not available for all of the models measured.  In general,
 most of the measurements are less than 2,000 scfd (only seven out of the 41 measurements
 are greater than 2,000 scfd), and  all of the measurements are below the reported controller
 delivery capacities of 4,320 and 8,880 scfd (two devices had emission measurements of
 4,215 scfd).

             As stated previously, the manufacturers' bleed rates represent laboratory
measurements of the gas consumption for new pneumatic devices.  In reality, the pneumatic
devices in the field have various states of wear  and may emit gas at rates higher than the
manufacturers' gas consumption data suggest.  The measured emission are in the range of
values provided  by the manufacturer ar.d are believed to reflect  more typical operating
conditions for these devices and account for increased emissions due to wear. For the
purpose of this report, the measured emissions provided by CPA are combined with the
contractor's direct measurements to estimate the emission factor from continuous bleed
throttling devices.  The resulting natural gas emission factor for the production segment is
654  ±31% scfd per continuous bleed device.
                                           42

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              Measured           for Intermittent Bleed Devices

              Field              for                 devices, using the      technique
          for the                 devices,           available from companies participating
 in this study.10  Based on the criteria described for continuous bleed devices, measurements
 for the intermittent       devices were reviewed and judged to be acceptable,  A      of
 seven measurements were provided from intermittent bleed devices found in onshore
 production service.  No measurements were available for these types of devices in offshore
 service or the transmission segment.  The average emission rate for the  seven devices is 511
 scfd +  36%.  The measurements ranged from 211 to 950 scfd/device, as compared to the
 CPA measurements of similar devices which ranged  from  12 to 695 scfd/device (average of
 211  scfd from Table 4-2), Combining the 19 measurements from both sources (Canadian
 and  U.S.  field measurements) results in a natural gas emission factor of 323 ± 34%
 scfd/device for intermittent bleed devices in production.

              Site

              For this study,      ware               a     of 22      to          a
of                   for production     and to           the fraction of intermittent
continuous bleed        at           The        of     device               to      the
emission factor to generate one emission factor for & "generic™ pneumatic device.   Table 4-5
summarizes  the data collected at production sites. For each site, the number of snap-acting
devices and  the number of throttling devices were collected.  Where possible, the
manufacturer and model number were recorded for each device.

              As discussed in Section 3, throttling devices  can be either intermittent or
continuous bleed, while snap-acting devices are alwa' f intermittent bleed. The number of
throttling continuous bleed devices at each site     determined based on the manufacturer
and model type of the devices observed.             two device types     distinctly
different               the fraction of                  versus continuous       devices is
                                           43

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      TABLE 4-3.  SUMMARY OF PRODUCTION SITE DATA
Site
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
!8
19
20
21
22
TOTALS
FRACTION
Total
Count of
Devices
136
18
405
68
2!
13
3
3
6
14
76
600
107
69
13
1
2
4
46
5
11
31
4,204
BY DEVICE
Power
Media
Gas
Gas
Gas
Gas
Gas
Gas
Gas
Gas
Gas
Gas
Gas
Gas
Air
Gas
Gas
Gas
Gas
Air
Air
Gas
Gas
Gas

TYPE
Number of
Snap-Acting
Devices
114
75
405
48
26
94
999
667
3
0
0
0
71
42
8
1
3
3
6
4
5
0
2,574
Number of
Throttling
Devices"
22
95
0
20
83
534
0
0
3
14
76
600
36
27
5
0
0
!
40
1
42
31
1,630
Non Continuous Bleed
0.65 ± 43%
Number of
Continuous
Bleed Devices'1
22
29
0
20
21
534
0
0
3
0
76
600
25
20
0
0
0
0
40
0
42
31
1,463
Continuous Bleed
0,35 ± 43%
*  Throttling devices can be either continuous or intermittent bleed,
b  Continuous bleed devices are a sub-category of throttling devices.
                                   44

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 required to develop an emission factor.  From the site data, the fraction of continuous bleed
 devices is 0,35 ±43%,  By difference, the fraction of intermittent      pneumatic devices
 is 0.65 ±43%.

              Methane Composition

              The           by volume of         in product .d natural gas was determined
 to be 78.8%  ± 5%. Details about this       are          in th? report, Methane Emissions
from the Natural Gas Industry,  Volume 6; Vented and Combustion Source Summary.w

              Emission Factor Calculation

              The weighted         factor per device was calculated for production
         as follows:
              /Fraction rf                     tf    f     Qmtimieras BleeA
    1 *™   — fatemuttenf .,   Bleed    4. _   ..     „,  . .,    _ .  .       „  MeJhane
    Emission -           X  ^^  + Ctoatonous Bleed X    BmraoD     X       ifal
     Factor     \ Devfces       Factor          Devices            Factor     j
                                                                                    (1)
              The site      were used to        the fraction of intermittent bleed versus
continuous bleed devices;  65% ±43%             bleed and 35% ± 43% continuous bleed
(Table 4-5),  Table 4-6            the         factor terms,        the emission        for
the individual device      (intermittent        continuous bleed) were       on the
measurements from the United States and Canada discussed previously.

              The final result is an average device methane emission factor of 345
scfd/device ± 40% (90% confidence interval), or 126,000 scf/device annually.
                                          45

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          TABLE 4-6.  PRODUCTION EMISSION FACTOR CALCULATION
                                                               Selected Natural Gas
                                   Fraction of Device Type        Emission Factor,
          Device Type                                              scfd/device
  Intermittent Bleed                      0.65 ± 43%                 323  ± 34%
  Continuous Bleed                       0.35 ±43%                 654  ± 31%
          Methane Emission Factor for Average Device  - 345 ±40% scfd/device
4.2           Transmission and Storage Segment

              The transmission segment is composed of pipelines, compressor stations, and
storage stations. Very few pneumatic devices of any type are associated with the pipelines.
Within the storage and mainline compressor stations, most of the pneumatic devices are gas-
actuated isolation valves and continuous bleed controllers.

4.2,1         General Emission Factor Characteristics

              The type of continuous bleed devices in the transmission segment are
essentially the same as those in the production segment.  The difference is in the use of the
devices.  In the transmission segment, continuous bleed pneumatic devices are used to
regulate pressure on compressors and are sized larger due to the higher pressures  in
transmission.  In production, smaller devices are used primarily to control the liquid level in
separators.  Since most of the same manufacturers are used,  this section will not repeat the
discussion from Section 4.1.1.

              Isolation valve actuators are predominately found in the transmission segment.
Isolation valve actuators emit gas whenever the valve is moved to either the open or closed
position. Most compressor stations and storage stations have many valves, since valves are
needed to make normal changes in pipeline and equipment flow configurations,  as well as to
                                          46

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 isolate aed            equipment for            or in     of an emergency.  Most
 use natural gas rather than compressed air to actuate these large valves, A large volume of
 gas is needed to move multiple valves and this requires a large investment in equipment if
 compressed air is used,

 4.2.2         Transmission          Factors

              Manufacturer and

              The transmission emission factors were determined from information gathered
 during site visits and from manufacturers' data.  The gas-operated devices used in the
 transmission        were classified     three categories:  continuous      devices,
         valves with turbine operators, and         valves with displacement-type
 pneumatic/hydraulic operators.  Devices          on air      not included in the
 calculation,

              The natural gas emission factor for the continuous bleed devices used in
 transmission  is based on measured emissions  from these devices at transmission stations
 (measurement procedure and     quality checks were discussed in Section 4.1.2).10 As
shown in Table 4-4,                         23 devices ranged from 152 to 4,215 scfd of
       gas per device,      an                gas                of 1,363  ± 29%
sefd/device (497,583 scf/deviee annually). It       be      that                 devices
were not observed at transmission stations,

              Data on the following characteristics of isolation valves were gathered at 16
transmission  sites:

              1.           device     (continuous Heed, turbine, or pneumatic/hydraulic);
              2,     Manufacturer  and        number;
                                           47

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              3.     Supply gas pressure, supply gas type (air produces no methane
                     emissions); and
              4,     Number of full stroke cycles per year (each cycle consists of two valve
                     movements; open and close).
              All of the displacement isolation valves observed at the transmission      were
 the pneumatic/hydraulic rotary      type (Figures 3-11 and 3-12).  The        of actuation
 cycles per                on site data.  The manufacturer provided the volume of gas
 based on the discharge pressure.  These values (shown in Table 4-7) were combined to
 calculate the annual emission factor for each type of displacement-operated isolation valve:
                  — Device Gas  Usage v Discharge Pressure v  Frequency   v  2 Valve Movements  ,
                        (scf/psta:>             
-------
4-7,
   ISOLATION VALVE OPERATORS
Supply
Gas ' - Gas Usage
Pressure, Actaator per Cycle,
Site psig scf/psi
1 935 6.5 x 3.5 0.0042
6.5 x 3.5 0.0042
9x7 0.0123
11x7 0.022
14,5 x 14 0,0852
16.5 x 16 0.1183
16.5 x 16 0.1183
18x8 0.0489
18 x 8 0.0489
18 x 12 0,0852
25 i 16 0.318
25 x 16 0.318
Total Emissions for Site 1
Site Weighted Average = 1,879
2 935 25 x 16 0.318
25 x 16 0.318
25 x 16 0.3!8
20 x 16 0.1981
12.5 x 12 0.0482
12 n 12 0.0482
15 x 8 0.0279
11 x 8 0.0489
18x8 0.0489
20 x 16 0.1981
20 x 16 0.1981
26 x 36 0.7565
25x16 0.31*
9x7 0.0123
9x7 0,0123
Total Emissions for Site 2 *
Site Weighted Average = 16,680
Number
of
Devices
4
1
I
1
1
3
2
3
J
!
5
1
= 45,086
seffdevice
4
2
2
6
4
i
I
I
I
I
1
1
1
5
2
= 583,803
Cycles/
Year
12
1
t
1
1
I
12
1
12
t
12
1
scf
± 54%
92
64
50
5
92
5
6
6
50
2
15
36
2
5
2
scf
Anniuil
Gas Usage,
•scf/
Device Type
383
8
23
42
162
674
5,393
279
1,115
162
36,242
604


237,496
82,60?
64,537
147,649
1,467
587
34(1
4,962
198
6,031
14,473
3,071
19,36!
624
100

scf/device- i 37%
                                    Continued
               49

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                  TABLE 4-7.  (CONTINUED)
Site
3










Supply
Gas
Pressure,
pstg
1000










Actuator
Size
5,5 x 3.5
6.5 xS
9x7
11 x 10
12,5 x 10
12.5 x 12
20 x 16
25 x 16
16.5 x 16
14.5 x 14
12.5 x 12
Gas Usage
per Cycle,
sef/psi
0,0035
0.008
0.0123
0.0318
0.0279
0.0482
0,1981
0.318
0.1183
0.0852
0.0482
Number
of
Devices
7
14
8
1
1
5
3
12
9
1
1
Cycles/
Year
1S.2*
15.2
15.2
15.2
15.2
15.2
15.2
15.2
15.2
15.2
15,2
Annual
Gas Usage,
scf/
Device Type
705
3,224
2,833
915
803
6,938
17,108
109,853
30,650
2,453
1,388
                Total Emissions for Site 3 = 176,870 scf
             Site Weighted Average = 2,853 scf/device ± 27%
       950
12.5 x 12
6.5 x 3.5
 11 x 10
 16 wkm
0.0482
0.0042
0.0318
0.072
12
12
12
12
                 Total         for Site 4 = 7,688 scf
             Site Weighted Average = 1,091 scf/device ±
3,348
 97
 736
3,507
AVERAGE                                   FACTOR = 5,627 ± 112%
                             scf/device
                                50

-------
              Discharge  volumes for the turbine-operated isolation valves depend on the supply
 gas pressure, the         of full stroke cycles      year             cycle         of two
 valve movements), and the          that the                to complete a valve movement, as
 follows:
        pp       — Device Gas Usage ^ Operating Duration ..  Frequency   <2 Valve Movements]
                       (sef/min)                          (cycles/year)X I      Cycle      I  ®
           liolatlsfi
           Wve
              Information on the approximate turbine  motor gas consumption for a given gas
pressure was provided  by Limitorque Corporation.l3 The manufacturer also provided a typical
value for the time required to open or      a valve.  Two sites furnished the supply gas
          the         of           per year, and the        of             to       or
the valve. This information is       in Table 4-8.  Average or                     on
information provided by sites or manufacturers) were used for other sites with turbine
operators.  As with the rotary vane isolation valve emission factor, the emission factor for
                               was also       on an         of the site       The
                factor for                 is 67,599 ± 276% scf/device.

              Methane Composition

              The          composition for the             and
to be        ± 1.5%.*

              Emission Factor Calculation

              Site                to         a relative         of     type of              in
the                       Data on        and                                 collected from
16 sites.  For continuous bleed devices,  data, for an additional 38 sites were available from a
large transmission company participating in this project. Based on the average number of
devices at     site, the             of devices for a typical                   and the
                                             51

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          TABLE 4-8.  MANUFACTURER DATA FOR TURBINE OPERATED
                                  ISOLATION VALVES


Site
1

2
3
(Typical Values)
4
(Typica! Values)
5
{Typical Values)

Supply
Gas
Pressure,
psig
900-970

800
«0§

800

SCO

AVERAGE ANNUAL TURBINE
gis/devioe


Gas
Consumption,
scfm
SOO-520

470
470

470

470


Time/
Operation,
sec
30
120
180
90

90

90

DEVICE FACTOR




Gas Usage,
scf/Opcration
255
1020
1410
705

705

705

, scf natural



Cycles/
Year
11
1
75
29

29

29



Annual
Natural
Gas
Emissions,
set/device
3,825

211,500
40,890

40,890

40,890

67,599 ±

fraction of each type of device were determined.  Tables 4-9 and 4-10            the
           for            type.


             The annual transmission segment emission factor (scf/site) was determined from

the following
            EF — I EFceatffiOTs X FraetiGiiasrfisTOs  *  EF tw«ne  X Fraction twkine
                        bleed              bleed         epera^ois            operators          , ,,
                                                                                     (4)

                      '  EFdispjacemcnt X FtactioDdispbcanent 1 X  % methane
                            opemtom             ©peratffls /
             EF           (497,584 scf/device x 0.32 cont.       devices/total
                           + 67,599 scf/device x 0.16 turbine devices/total
                           + 5,627  scf/device x 0.52 displacement devices/total)
                           x 0.934  mol methane/mol gas

             EF    =      162,197  ± 44%

                                         52

-------
4-9.                                          -
Site
i
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Average Number
of Devices/Site
Fraction Device/Site
Annual Natural
Factor
scf/device
Turbine
Devices/Site
3
16
12
35
44
0
0
0
0
0
0
0
0
0
0
0
6.25 ± 94%
0,1 56 ±94%
±
Rotary Vane
Displacement
Devices/Site
26
62
34
0
0
11
17
35
69
6
18
4
50
2
0
0
20.9 ± 48%
± 48%
5,627 ± 1 12%
                        53

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TABLE 4-10, TRANSMISSION DEVICE COUNTS - CONTINUOUS BLEED
Sit*
t
2
3
4
5
6
7
8
9
10
11
12
13
K
15
16
17
18
19
20
21
22
23
24
25
26
27

Continuous Bleed Devfces/Stte
39
16
4
3
4
!
1
4
6
2
2
127
IS
4
22
3
4
4
4
1
1
I
15
92
3
6
i
Site
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
Average Number Devices/Site
Fraction of Device/Site
Annual Natural Gas Emission Factor, scWevice
Continuous Bleed Devices/Site
11
H
32
9
12
4
21
12
3
15
3
11
10
44
3
3
9
12
4
26
2
7
11
11
15
6
1
12,9 ± 69%
0 ,32 ± 69%
497,583 ± 29%
                           54

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 4.3          tSas Processing. Segment

              The gas processing segment     plants)                  air to power the
 majority of pneumatic devices within the plant.  Of the nine gas       visited  for
 study, only one             gas-powered,            bleed devices in the plant. Approxi-
 mately one-half of the plants visited            gas-driven  pneumatic controllers for the
 isolation valves on the main pipeline emergency shut-down  system for the plant or for
 isolation valves used for maintenance work on specific sections  of the plant. All of the
 other sites used compressed  air to power their pneumatic continuous bleed devices  and
 isolation valves.

              Unlike the production and transmission industry segments, a mix of
 pneumatic devices was not observed at each gas processing  site.  Instead, the gas plants
 visited generally  used only one type of natural gas powered pneumatic device throughout
 the plant.               by device            not be            so           '.vere
 calculated  on a site     rather      a device

              Manufacturers* and      Data

              The          of             in the                      are
 commonly used in the gas processing  segment — continuous bleed throttling devices,
 displacement-operated isolation valves, and turbine-operated isolation valves. For the  sites
where  specific information was provided, emission calculations were based on that
 information.  However, for some sites, the information provided included little  more than
the type of actuator, supply gas pressure, and an estimate of the number of operations.  In
these cases, average values from the transmission segment were  used to complete the
calculations.  The site data with the emission estimates are shown in Table 4-11, The
technique      to develop  emission  factors for     site is           separately.
                                           55

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TABLE 4-11. GAS PROCESSING SITE EMISSION ESTIMATES FOR NATURAL GAS


Site
1


2

3
4

5


6




7
8
9



Pev Ice Type
Continuous
Bleed
(Fisher)
Isolation
(Fisher)
Air
Isolation
(Turbine)
Isolation
Piston Type
(Rotary Vane)
Isolation
(Turbice &
Pneumatic/
Hydraulic-type
Rotary Vane)
Air
Air
Air

Number .
of Operations/
Devices Year
2 Continuous


3 12

-
25 1

7 12
18 1

1 1
16 12



--
--
„
Total
(for gas sites)
• ' Natural

Device, scf set/Site
497,584 995,168 ± 29%


214,675 ±29%

—
780 ± 112%

48 1,206 ± 49%


660 44,115 4- 68%
2,716



--
-
..
1,704 Mscf ± 21%
341 site ± 103%

-------
              Site 1:  Continuous       devices, such as those      in the transmission
              segment, were observed at this site.  Since the application of these devices is
              similar to the transmission segment, the annual  emission factor of 497,584 scf
              per device  (based on 1,363 scfd/device from Tabie 4-4) was used.

              Site 2:  Fisher devices were used to operate isolation vahes at this site.
              Information on the            for the specific dt»;ce type     provided by the
              site.

              Site 4:  Manufacturer's  data from Limitorque were used to estimate emissions
              for the turbine operators observed  at this site.13  The plant provided  the
              supply gas pressure of 400 psig, and a typical actuation time of 1.5  minutes
              was used (based on manufacturer data).

              Site 5:  Piston-type isolation valve operators were found at only one site;
              information for the  specific device types were provided by Pantex, the
              manufacturer.6  Table 4-12 lists the manufacturer's data for the model types
              identified at this site. The weighted average annual emission factor for this
              type of device was determined to be 48 scf/device ± 49%.
                   6:  For the pneumatle/hydraufle-type rotary      devicp" observed at this
              site, the emission factor was       on  the         volume 01 natural
                      per actuation for the                   In Table 4-7. Manufacturer's
                   frorr> Limitorque,       on a supply gas         of 350 psig, were
              to estimate the emissions for the turbine operator at this site.

              Methane Composition

              The percentage of         in  gas      in gas
           to be 87.0% ± 5%.  Details about this       are           in the GRI/EPA
report, Methane Emissions from the Natural  Gas Industry, Volume 6: Vented and
Combustion Source Summary.26
                                           57

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    TABLE 4-12. GAS USE INFORMATION FOR PANTEX DEVICES
           (PISTON DISPLACEMENT ISOLATION DEVICES)
No.
Devices
6
2
1
2
5
1
1
2
Piston
Diameter
(in.)
8.0
3.0
3.5
2.0
8.0
2.5
6.0
6.0
Stroke
Length
(in.)
20
4
4
4
16
8
16
12
Gas
Usage
(acf/stroke)
0.5818
0.0164
0.0222
0.0073
0.4654
0.0227
0.2618
0.1964
Annual Site Gas Consumption, scf

Weighted Annual
Average per Device,
scf
Annual Gas
Consumption *
(scf/device)
512
4.8
3.3
2.1
341
3.3
38.4
57.6
965
48.1
' Gas consumption calculated based on supply pressure of 250 psig, an average of
 4.1 operations per year, and two strokes (open and close) per operation.
                                 58

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 equation:
where:
              Emission Factor Calculation
              The gas processing emission factor was calculated according to the following
                       J^  Annual Site Emissions,  scf Natural Gas                       /g*
           EF= K X ——	 X % methane
              K     =      fraction of sites that use natural gas rather than air (0.556 +
                            59%)
              n      =      number of sites operating devices with natural  gas
              Assuming that the sites surveyed are representative of the United States, the
average emission rate for sites using natural gas was adjusted based on the ratio of sites
using gas-operated  devices to the total number of sites surveyed.  The annual gas
processing methane emission factor of 165 Mscf/site ± 133% was calculated as shown:
              EF
              EF
              0.556 ± 59% gas sites/total sites surveyed x 341  ± 103%
              Mscf/gas site x 0.87 ± 5% mol methane/rno! gas
              165 + 133% Mscf/site
4.4
Distribution Segment
              The pneumatic devices in the distribution segment primarily consist of
pressure reduction throttling valves at vneter and pressure regulation (M&R) stations.  The
actuators and  controllers for there valves are generally gas  powered, but may or may not
bleed gas to the atmosphere, depending  on their design. Emissions from these devices  were
                                           59

-------
          as part of the                for M&R         and included in the M&R
emission rates.1 Distribution  pneumatic emissions are therefore excluded from this report.

              Isolation valve           at distribution M&R stations are usually manually or
motor-operated. There were so few pneumatic operators on isolation valves that this
emission source is considered negligible.
                                           60

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 5.0           PNEUMATIC DEVICE ACTIVITY FACTORS

              Pneumatic device activity        are           in detail in Volume 5 on
 activity factors,2'  The techniques      to develop pneumatic device activity factors for the
 various industry segments are summarized in this section.  For each industry segment, the
 activity factor            to the         factor      presented in Section 4, That is, a
 count of pneumatic        is      for the production and                      while the
        of gas plants is      for the gas

 5.1           Production Segment

              The      number of pneumatic devices in the U.S. production         was
 determined from regionalized site data.  The number of pneumatic devices at each    were
 weighted based on the number of gas  wells and the  marketed  gas production  at each site.
 The  site data were extrapolated  by the number of gas wells and tbe marketed gas
                      region.  In production, the               of
          Is         ±

 5.2           Gas Processing Segment

              The activity       for gas            is      on the        of gas
                         annually by tbe Oil and Gas Journal. For the     year 1992,
the U.S. activity factor for gas processing is  726 gas plants.30  A confidence  bound of ± 2%
was  assigned based on engineering judgement.

5.3          Transmission and Storage Segment

             The number of natural gas-operated pneumatic  devices  in the transmission
and storage segment WB.S calculated based on the average  number of devices p".r station
                                          61

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multiplied by the total number of transmission  and storage stations nationally using the
following equation:
                AT,   Average Number of Devices  ., „   ,     ,, _. ..               tf--.
                AF = 	§	  X          of                   (6)
                                 Station
The average number of pneumatic devices per  station is the sum of the average number of
turbine devices per site, the average number of rotary vane displacement devices per site,
     the average number of continuous bleed devices per site.  Using the numbers shown in
Tables 4-10 and 4-11, the average number of pneumatic devices per site is 40 ± 37%.
Therefore, the pneumatic device activity factor for transmission  stations is:

                           AF = (6.25 ±
                                  + 20.9 ± 48%      vane devices/site
                                  + 12.9 ± 69% continuous bleed devices/site)
                                  x 2,175 ± 8% stations
                           AF = (40 ± 37%                 x (2,175 ± 8%
                           AF = 87,206 ±

The activity factor includes only pneumatic devices operated by natural gas.  Mechanical,
electrical, and air-operated  devices were excluded from the site counts and are therefore
         from the         activity  factor.
                                          62

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6.0

              National emission rates from pneumatic  devices for each industry segment
were calculated by multiplying the                by  the activity factor:

                National Emission Rate = Emission Factor x Activity Factor

Table 6-1          the final results of the          rate calculations for      industry
segment.

                               6-1.

Production
Gas Processing
Transmission
.Metfcane .Emission
. .Factor .
125,925 ± 40%
scf/de¥iee
165 ±
162,197 ± 44%
sef/device
Activity Factor
249,111 ±48%
devices
726 ± 2% sites
87,206 ± 38%
devices
Annual Emission
Rate
31.4±65%Bscf
0.12 ± 133% Bscf
14.1 ± 60% Bscf
                    on      results,                            a      of 45.6 ± 48%
Bscf of methane for 1992.
                                           63

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7.0
 L           Campbell, L.M. and B.E.                 Emissions from the Natural Gas
             Industry, Volume 10: Metering and Pressure Regulating Stations in Natural
             Gas Transmission and Distribution, Final Report, GRJ-95/G257.27 and EPA-
             600/R-96-080J, Gas Research Institute and U.S. Environmental Protection
             Agency, June 1996,

2,           Myers, D.B. and M.R, Harrison.  Methane Emissions from the Natural Gas
             Industry, Volume 15: Gas-Assisted Glycol Pumps,       Report, GRI-
             95/0257.33 and EPA-600/R-96-08Q0, Gas                 and U.S.
             Environmental Protection Agency, June 1996.

3.           Shires, T.M.  Methane Emissions from the Natural Gas Industry,  Volume 13:
             Chemical Injection Pumps,              GRI-95/0257,30 and EPA-6Q0/R-96-
             080m, Gas                 and U.S.              Protection Agency,
             June 1996.

4.           Shires, T.M. and M.R. Harrison.  Methane Emissions from the Natural Gas
             Industry,  Volume 7: Blow and Purge Activities, Final Report, GRI-95/0257.24
             and EPA-6QO/R-96-080g, Gas Research Institute and U.S. Environmental
             Protection Agency,      1996.

5.           Perry, J.H, (ed.) Chemical Engineers Handbook, 5th Edition,  McGraw-Hill,
             New York, NY, 1973.

6.           Paiitex Valve Actuators and Systems, Inc. Stmngarm Series S Actuators for
             Rotating Stem Valves, Bulletin No. SS-5-91,  Stafford, TX.

7.           Hummel, K.E., L.M. Campbell, and M.R. Harrison. Methane Emissions
             from the Natural Gas Industry, Volume 8: Equipment Leaks, Final Report,
             GRI-95/0257.25 and BPA-600/R-96-080h, Gas                 and U.S.
             Environmental Protection Agency, June 1996.

8,           Norriseal Controls.  Norriseal Level Controller Series 1Q01-A Catalog.
                      TX,

9.                                      lac. 4150K and 4160K Series Pressure
             Controllers and Transmitters,        34:3:4150K. Marshalltown, IA,  1992.

10.          Controller survey data provided by Tenneco Gas Transportation,  1994 and
             Chevron, 1995.
                                        64

-------
 11.          Picard, D.J., B.D, Ross, and D.W.H. Koon.  "A Detailed Inventory of CH4
             and VOC          From Upstream Oil and Gas          in Alberta."
                                           Calgary, Alberta, 1992,

 12.          Shafer Valve Operating Systems.  Rotary Vane Valve Operators, Bulletin RV-
             110.  Houston, TX, 1980.

 13.          Personal correspondence with Belva Short of  Limitorque Corporation,
             Lynchburg, VA, April 5, 1994

 14.          Personal               with Brian      of Clearstone Engineering, Alberta,
                             16, 1995.

 15.          Personal correspondence with Bob Finley of Bristol Babcock Inc., Watertown,
             CT, October 3, 1995.

 16.                   correspondence with Clark Crowno¥er of Puffer Sweiven, Inc.,
                      TX,         6, 1995.

 17.          Personal correspondence with Maurice Hoss of Invalco Inc., Hutchinson, KS,
             October 6, 1995.

 18.                                 with Quin Kroll of Noiriseal, Houston, TX, October
             4, 1995.

 19.          Dover Corporation,  Norriseal Controls Series 1000 Liquid Level Control,
             Manufacturer Bulletin 1.1, Catalog Section 1,  W.C. Morris Division, Houston,
             TX, My 1963.

20.          Bristol Babeock.  624-11 Indicating Pneumatic Transmitters Specifications,
                              A103-la, Watertown, CT,

21.          Bristol Babcoek.  Series 5453 Indicating Pneumatic Pressure Controllers,
             Specification      A118-2c, Watertown, CT.  1992,

22.          Fisher Controls International, Inc.  3582 Series Pneumatic and Type 35821
             Electro-Pneumatic Valve Positioners,         62.1:3582.               IA,


23.                Controls             Inc. 361QJ and 36203 Series Positioners,
             Bulletin 62.1:3610, Marshalltown, IA, 1992.

24.          Invalco.  Low Energy Pilot Retrofit Kit for CT Series Flextube, CT Series,
                   1,      IVC-801-AH, Tulsa, OK,           1, 1990.
                                         65

-------
25.          Invafco,  CT Series Flextube Displacer Type Level Controller, CT Series,
             1, Page IVC-801-A3, Tulsa, OK, April 30, 1990,

26,          Shires, T.M, and M.R. Harrison.  Methane Emissions from the Natural Gas
             Industry, Volume 6: Vented and Combustion Source Summary. Final Report,
             GRI-94/0257.23 and EPA-6G0/R-96-08Gf, Gas Research Institute and U.S.
             Environmental Protection Agency, June 1996.

27,          Shafer Valve                   Gas Consumption Calculation Method for
             Rotary Vane, Gas/Hydraulic Actuators.  Technical         Data, Bulletin GC-
                               OH, June 1993.

28.          Shafer Valve Operating Systems. Gas Consumption Calculation Method for
             Rotary Vane, Gas/Hydraulic Actuators, Technical Bulletin Data, Bulletin GC-
             2-00394. Mansfield, OH, March 1994.

29.          Stapper, B.E. Methane Emissions from the Natural Gas Industry, Volume 5:
             Activity Factors,             GRI-94/0257.22 and EPA-600/R-96-080e, Gas
             Research Institute and U.S. Environmental Protection Agency, June 1996.

30.          Bell, L. "Worldwide Gas Processing," Oil and Gas Journal, My 12, 1993, p.
             55,
                                        66

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APPENDIX A
   A-!

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                                                 P-4
                                  PRODUCTION SOURCE SHEET

 SOURCES:
                                              (wells, heaters, separators, dehydrators, compressors)
                                                        Devices
 OPERATING                                 Normal Operation
            TYPE:                            Unsteady, Vented
 ANNUAL EMISSIONS!                       31.4 Bscf ± 65 %

 BACKG1OUNB:
 Most 01 the pneumatic devices in the industry are valve actuators and controllers that use natural gas pressure as
 the force for valve           There is a      population of          devices throughout the gas industry,
 Gas from the valve actuator is vented to the atmosphere during every valve stroke, and gas     be continuously
 bled from the valYe controller     as well.

 EMISSION FACTOR:          125,925 sef per average device ± 40%

        (This was a«yusted for  the production methane fraction of naturiii gas at 78,8 moi%.)

 Pneumatic       (valve controllers)       to control       are the              of pneumatic          in
 the production          There are two      of                        modes: intermittent and continuous.
           bleed devices emit methane to the           only when the control valve         when the device
 is not moving the bleed rate is zero.  Continuous Weed devices emit methane both when the valve actuates and
 when the device is not moving.  An emission rate for a generic pneumatic device combines the bleed rates of the
 two types of devices, weighted by the population of the device types as follows:

        EF»»p«m,.**e          =       (Fraction ,„,„„,„„, x IP ,«,„»„, + Fraction
                                        x % inethine
where:
        Fractionlmemmai          =      0.65 ± 43%
        Fraction„„,„„„,          =      0.35 ± 43%
        % Methane             =      78.8 mol % ± S%
          for           and continuous bleed devices were based on         data provided by A Canadian
study and U.S. field measurements from a separate contractor's program.  The average measured emissions for
intermittent and continuous Meed devices are 323 ±34% and 654 ±31% scfd/device, respectively.  The
fraction of each type of device was determined from site visits.

Therefore the                       factor for a generic           device is:

       EF ».. pro** **e        =      125,925 ± 40 %

EF DATA

        1.      Methane Emissions from the Natural Gas industry,  Volume 12: Pneumatic Devices (1)
               establishes the important emission-affecting characteristics.
                                                A-2

-------
        2.      Site visit device counts establish the fraction of continuous bleed versus intermittent bleed
                devices for multiple sites.
        3.      The Canadian Producers Association fCPA) determined ac average         factor per device
                      on 19 measurements.
        4.      An independent contractor provided 18              of pneumatic devils in onshore and
                offshore production services.
 EF
        Basis:
                EF accuracy is      on error propagation from the spread of site device counts and measured
                emission rates.
ACTIVITY FACTOR:  249,111 pneumatic controllers ± 48 %

The average count of devices per equipment type was determined from multiple site visits.  The ratios for the
number of devices per gas well and the number of devices per marketed gas production were compiled by
region. The regional values were summed to give national device counts based on well counts and marketed gas
production.  These values were averaged to give the final national device count of 249,111.

AF DATA SOURCES:

        1.      Methane Emissions from the Natural Gas Industry,  Volume 5: Activity Factors (2) establishes
                the methodology for extrapolating the site      to a        count,
        2.      Site visit device counts, well counts,    production rates establish the number of devices per
                well and the number of devices per gas production,
        3.      Total regional gas well counts     1992 marketed gas production rates are from A.G.A,  Gas
                     (3).
        4.      The oil wells that market gas were calculated by this report and World Oil (4).  Total oil wells
                for 1992 are         as 602,197 by the Oil A Gas Journal (5).  The active oil wells that
                market gas arc determined by multiplying the     national active wells by Jhe fraction that
                       gas. The         is                a Texas Railroad Commission         (6) on oil
                      and gas disposition from      leases; an        that shows the percent of oil
                that        the           gas in Texas is 34.7%.


AF PRECISION:
        Basis:
        1.      The accuracy for the devices per well and devices per gas production rate are calculated from
                the spread of site data collected for each region (a total of 36 sites).
        2.      The accuracy for wells that market gas are based on the spread of data from  the Texas
                Railroad Commission database.
ANNUAL                           31.4 Bsef ±65%

The national annual emissions were determined by multiplying an emission factor for an average pneumatic
device by the population of devices in the production segment.

        125,925 scf x 249,111         =  31 Bsef
                                                 A-3

-------
REFERENCES

I.       Shires, T.M. and M.R, Harrison,  Methane Emissions from the Natural Gas Industry, Volume 12:
        Pneumatic Devices, Final Report, GRI-94/0257.29 and EPA-60Q/R-96-OS01, Gas Research Institute and
        U.S. Environmental Protection Agency, June 1996.

2.       Stapper, B.E. Methane Emissions from the Natural Gas Industry,  Volume 5: Activity Factors. Final
        Report, GRI-94/0257.22 and EPA-6QO/R-96-080e, Gas Research Institute and U.S. Environmental
        Protection Agency, June 1996.

3,       American Gas Association.  Gas Facts: 1993 Data, Arlington, VA, 1994.

4,       Gulf Coast Publishing Company, World 0(7, Annual Forecast/Review, Vol. 214, No. 2, February 1993.

5.       Oil and Gas Journal.  1992 Worldwide Gas Processing Survey Database, 1993.

6.       Texas Railroad Commission, P-l, P-2 Tapes, Radian files, Austin, TX,  1989.
                                                A-4

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                                                   T-4
                          TRANSMISSION AND STORAGE  SOURCE SHEET

 SOURCES:                                     Various Equipment (vessels, compressors,  piping)
 OPERATING  MODE:                          Normal  Operation
 EMISSION TYPE:                             Unsteady, Vented
 COMPONENTS:                                Pneumatic Devices
 ANNUAL EMISSIONS:                         14.1 Bscf ± 60%

 BACKGROUND:
 The transmission segment is comprised of compressor stations, pipelines, and storage stations. There are
 essentially no pneumatic devices associated with the pipelines. Within the storage and compressor stations,
 most of the pneumatics are gar.-actuated isolation valves, and there are a few continuous bleed controllers.

 Meter-only stations  do not have venting pneumatics.  Meter and regulation (M&R)  stations do have regulating
 pneumatic controllers  (the pressure regulator valves), but all of the M&R station pneumatic emissions are
 counted in the fugitive calculation for M&R stations and  so are not included in this sheet.

 The continuous bleed  controllers in transmission compressor stations are used for liquid level  control in filter-
 separatois and pressure reduction. The higher pressures anJ large pipe diameters associated with transmission
 operatir.is require larger actuators and valves than typically found in production, resulting in larger emissions
 than r,milar devices in production.

 Within the storage and mainline compressor stations, most of the pneumatic  devices are gas-actuated isolation
 valves.  These valves  block the flow  to or from a pipeline and can isolate the facility for maintenance work or
 in the  case of 5,1 emergency.  Therefore, the isolation vaives are actuated infrequently  and their emissions are
 intermittent.

 EMISSION FACTOR:          162,197 scf/device ± 44%

         (This was adjusted for frit- transmission methane fraction of natural gas at 93.4 mo!%.)

 The average pneumatic device emission factor was determined from a compilation of information from several
 sites.   Counts  of devices per site were taken during Radian  site visits.  The devices  were classified  into three
 categories: continuous  bleed valves, isolation valves with  turbine  operators, and isolation valves with
 displacement operators. The emission factor was determined based on the following equation:
        PF
        cr pneumatic devices
                                        operator! " nai/uuii turbine operaton
                                       e^n, op.,™,, x Fraction disptoCHBK11 „„„,,„„ ) x % methane
Listed below are the average fraction of devices for each of the three valve categories:

        Fraction «,„, Mecdv,,VB      =       0.32 ± 69%
        Fraction ^^ opm,M      =       0.16 ± 94%
        Fraction di!pl!cl!ment 0|1MUOtt   =       0.52 ± 48%

Emissions from continuous bleed pneumatics in the transmission segment were measured by an independent
contractor. The average emission factor, based on 23 measurements, is 1,363  scfd/device ± 29% (497,584
scfdeviee).
                                                  A-5

-------
 For the isolation valves with turbine operators, the emission factor depends on the gas usage for a given
 supply gas pressure, the time required to complete one movement of the valve, and the number of operations
 per year.  The annual emission factor Is then:

        EF ^Mnctftnnn   ~ Gas Usage {scf/Biin) x Operating Duration (into/operation) x 2
                                 (operations/cycle) x Frequency (cycles/year)

        EF „««»„«„   -        ± 276%

 The equation for isolation valves with displacement operators is similar;

        EF di,pi,OTS!» „,,„,„       = Gas                x Supply Pressure       x 2
                                 (operations/cycle) x Frequency (cycles/year)

        EF „«„»„„, afmuu       = 5,627 ± 1 12% scf/deviee

 EF DATA SOURCES:

        1.      Methane Emissions from the Natural Gas Industry, Volume 12: Pneumatic Devices (1)
                establishes the important emission-afeeting characteristics of transmission pneumatic
                devices,
        2,      Device counts from 16  compressor and storage stations establish the fraction of turbine valve
                operators, and displacement valve operators. Counts from a total of 54 stations were used to
                establish the fraction of continuous bleed devices.
        3,      The emission factor for the continuous bleed valv«s was based on 23 field measurements,
        4,      Qas        for the turbine valve operators were provided by Litnitorque. Operating duration
                and frequency were estimated based on information from two transmission stations.
        5.      Gas        for the displacement valve operators were provided by Shafer Valve Operating
                Systems.  Supply pressure and frequency of operation were estimited based on information
                from four transmission stations.

EF ACCURACY:
        Basis:
        1.      EF accuracy is      on error propagation from the combination of site  information and
                measured data.
        2.      It was assumed that the manufacturers' data are completely accurate,


ACTIVITY FACTORS:        87,206 pneumatfe devices. ± 3S%

The number of gas operated  pneumatic devices in the transmission  and storage segment was calculated based
on the average number of devices per station and multiplied by the total number of transmission and storage
stations nationally.  The average number of devices per site was determined to be 40 ± 37%.  The total count
of transmission compression  facilities is 2,175,  based on 1,700 compressor stations, 386 UG storage stations,
and 89 LNG storage station?.

AF MATA SOURCES;

        1.      The number of transmission compressor       . was compiled from  1992 Fossil Energy
                Commission Form No. 2:  Annual Report ot Majnr Natural Qas Companies (2).
                                                A-6

-------
        2.      The number of underground storage facilities is taken directly from A.G.A. Gas Facts:
                "Number of Pools, Wells, Compressor Stations, and Horsepower in Underground Storage
                Fields."  Data from base year 1992 were used (3).
        3.      The number of liquefied natural gas storage facilities was summed from A.G.A. Gas Facts,
                "Liquified Natural Gas Storage Operations  in the U.S. as of December 31, 1987 (4)." The
                table lists 54 complete plants, 32 satellite plants, and 3  import terminals for a total of 89
                facilities.
        4,      The number of devices per site is based on the total number of devices ob.eived during site
                visits.

AF ACCURACY:  38%
        Basis:
        1.      Extremely tight confidence limits are expected due to the well documented and reviewed
                numbers published in A.Q.A. Gas Facts and FERC forms.  A 10% confidence bound was
                assigned to the number of compressor stations and a 5% confidence bound was assigned to
                the number of storage stations.
        2.      The confidence bound on the number of devices per station was detsrmined based on the
                spread of site data.
ANNUAL METHANE EMISSIONS:  14.1 Bscf ± 60 %

The annual emissions were determined by multiplying  an emission factor per device (corrected for the
methane composition) by  the population of pneumatic  devices in the transmission segment.

                            162,197 scf/device x 87,206 devices = 14.1 Bscf

REFERENCES

1.      Shires, T.T/I, and  M.R. Harnson. Methane Emissions from the Natural Gas Industry,  Volume 12:
        Pneumatic Devices.  Final Report, GRI-94/0257.29 and EPA-600/R-96-0801,  Gas Research Institute
        and U.S. Environmental Protection Agency, June 1996.

2.      Department of Energy.  FERC Form No. 2:  Annual Report of Major Natural Gas Companies  OMB
        No, 1902-0028, Department of Energy Federal Energy Regulatory Commission, Washingtoi:, DC,
        December  1994.

3.      American Gas Association. Gas Facts:. 1993 Data,  Arlington, VA, 1994.

4.      American Gas Association. Gas Facts:. 1991 Data,  Arlington, VA, 1992.
                                               A-7

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                                              GP-6
                               GAS PROCESSING SOURCE SHEET

SOURCES;                                  Various Equipment (vessels,  compressors, piping)
COMPONENTS:                             Pneumatic Devices
OPERATING MODI;                        Normal Operation
            TYPE;                                    Vented
                                             0.1Bsef±133%

BACKGROUND:
The gas processing segment uses compressed air to power the majority of the pneumatic devices within the
plait, although some devices may be powered by natural gas. Many  plants use  gas driven pneumatic
controllers on isolation vaivs for emergency shut-down or maintenance work.

The           of devices     in the                    are also commonly      in the gas processing
        — continuous bleed throttling/regulating valves, displacement operators,     turbine operators,

EMISSION FACTOR;  165 Mscf per average plant ±  133%

        (This was adjusted for the gas processing methane fraction of natural gas at 87 nio!%.)

The average device gas emission faetsr was determined from a combination of vendor information on device
emission rates and device counts from  several sites. The                 factor     calculated using the
following equation:
                              n
                             ]P (Annual  Site Emissions, scf Natural  Gas)

        K              =      fraction of sites that use natural gas rather than air (0.56 ± 59%)
        n              =      number of sites operating with natural gas

Each term in this equation was           from site specific information.  The summation of the site
    was                  on the number of      with gas        devices       the     number of
    surveyed.  The site       are       in the following table.
                                              A-S

-------
"''Site
1
2
3
4
5
6

Number Operations/
Device Type of Devices Year
Throttling (Fisher)
(Fisher)
Air
Isolation (Turbine)
Isolation (Rotary Vane)
Isolation
(Turbine & Rotary Vane)
2 Continuous
3 12
..
25 1
7 12
18 I
1 1
16 12
Annual
Displacement/
Device, scf
497,584
214,«75
-
780
48
3,376

Displacement/
Site, scf
995,168 ±29%
± 29%
--
19,500 ± 112%
1,206 ± 49%
44,115 + 68%

                   Air

                   Air

                   Air
TOTAL
                                                                                      1,704 Msef ±21%
Average (for gas sites)
                                                                                      341 Mscf ±
BF DATA SOURCES:
        1,      Methane Emissions from the Natural Gas Industry, Volume 12; Pneumatic Devices
                          the important emission-affecting characteristics.
        2.      Site visit device       establish the number of continuous bleed devices,  turbine operators,
                and displacement operators far      site.
        3,      The emission factor for continuous      devices was estimated using data provided by one
                site and measurements for transmission pneumatic devices.
        4,      Gas usages for the displacement operators were provided by Pantex Valve Actuators and
                Systems and Shafer Valve Operating Systems.  The number of devices, supply gas pressure,
                and operating frequency were       on site information,
        5.      Gas        for the turbine operators were provided by Limitorqie Corp,  Operating duration,
                frequency, and supply gas pressure were      on site infoimatjon.
EF ACCURACY;
        Basis:
        1.      EF accuracy is based on error propagation from the spread of data for the nine sites visited.
        2.      It WES assumed that the manufacturers' data are completely accurate.
ACTIVITY FACTOR; 726 gas                  ± 2%

The activity factor for the gas processing segment was taken from published information from the year 1992.
                                                A-9

-------
 AF DATA SOURCES:

        I,     The number of gas processing plants was taken from the Oil and Gas Journal (2),


 AF PRECISION:
        Basis:
        1.      AF accuracy is based on engineering judgement.


 ANNUAL                             0,12 Bscf ±

 The annual emissions were determined by multiplying an average site emission factor (adjusted for the
 methane composition) by the     number of gas           sites,

                                 165 Msef/site x 726     -0.12 Bscf

 REFERENCES

 1,     Shires, T.M. and M,R. Harrison. Methane Emissions from the Natural Gas Industry,  Volume 12:
       Pneumatic Devices. Final Report, GRI-94/0257.29 and EPA-600/R-96-0801, Gas Research Institute
       and U.S. Environmental Protection Agency, June 1996.

2.     Bell, L. "Worldwide Gas Processing," Oil and Gas Journal, My 12, 1993, p. 55.
                                             A-10

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