SRI/USEPA-GHG-VR-04
September 1999
Environmental Technology
Verification Report
C. Lee Cook Division, Dover Corporation
Static Pac™ System
Phase I Report
Prepared by:
Southern Research Institute
Under a Cooperative Agreement With
A EPA U.S. Environmental Protection Agency
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ET
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EPA REVIEW NOTICE
This report has been peer and administratively reviewed by the U.S. Environmental Protection Agency, and
approved for publication. Mention of trade names or commercial products does not constitute endorsement or
recommendation for use.
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SRI/U SEPA-GHG-VR-04
September 1999
Greenhouse Gas Technology Verification Center
A U.S. EPA Sponsored Environmental Technology Verification Organization
C. Lee Cook Division, Dover Corporation
Static Pac™ System
Phase I
Technology Verification Report
Prepared By:
Southern Research Institute
Greenhouse Gas Technology Verification Center
PO Box 13825
Research Triangle Park, NC 27709 USA
Under EPA Cooperative Agreement CR 826311-01-0
U.S. Environmental Protection Agency
Office of Research and Development
National Risk Management Research Laboratory
Air Pollution Prevention and Control Division
Research Triangle Park, NC 27711 USA
EPA Project Officer: David A. Kirchgessner
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TABLE OF CONTENTS
ACKNOWLEDGMENTS iv
1.0 INTRODUCTION 1-1
1.1 BACKGROUND 1-1
1.2 TIIH STATIC PAC™ TECHNOLOGY 1-2
VERIFICATION GOALS 1-6
2.0 TECHNICAL BACKGROUND AND VERIFICATION APPROACH 2-1
2.1 METHANE EMISSIONS FROM NATURAL GAS COMPRESSORS 2-1
2.2 DESCRIPTION OF THE TEST SITE AND STATIC PAC™ INSTALLATION ... 2-2
2.3 VERIFICATION APPROACH 2-3
2.3.1 Establishing Baseline Conditions 2-3
2.3.1.1 Case 1 2-4
2.3.1.2 Case 2 2-5
2.3.1.3 Impact on Normal Running Emissions 2-7
2.3.2 Emission Measurements and Calculations 2-8
2.3.2.1 Rod Leak Rate Measurements 2-8
2.3.2.2 Component Leak Rate Measurements 2-11
2.3.2.3 Natural Gas Composition Measurements 2-12
2.3.2.4 Blowdown Volume Determination 2-12
2.3.3 Site Operational Data 2-12
3.0 RESULTS 3-1
3.1 ROD PACKING EMISSIONS 3-1
3.1.1 Emissions During Idle/Shutdown 3-1
3.1.2 Emissions During Compressor Operation 3-2
3.2 OTHER EMISSION SOURCES 3-3
3.2.1 Valve Leaks and Blowdown Volume 3-3
3.2.2 Miscellaneous Fugitive Sources 3-4
3.3 NET GAS SAVINGS 3-5
3.3.1 Compressor Operational Characteristics 3-5
3.3.2 Case 1 and Case 2 Gas Savings 3-7
3.3.3 Estimated Gas Savings For Other Compressor Rods 3-8
3.4 INSTALLATION REQUIREMENTS 3-11
4.0 DATA QUALITY 4-1
4.1 BACKGROUND 4-1
4.2 ROD PACKING EMISSION RATE MEASUREMENTS 4-1
4.2.1 Unit Valve, Blowdown Valve, and Pressure Relief Valve 4-4
4.2.2 Gas Composition 4-6
4.2.3 Blowdown Volume 4-6
4.3 OVERALL UNCERTAINTY IN THE MEASUREMENTS, NET GAS
SAVINGS, AND METHANE EMISSIONS VALUES 4-6
5.0 REFERENCES 5-1
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APPENDIX A
APPENDICES
Static Pac™ Operator's Manual - Automatic Control System
Page
A-l
Figure 1-1
Figure 1-2
Figure 1-3
Figure 1-4
Figure 2-1
Figure 2-2
Figure 2-3
Figure 3-1
Figure 3-2
Figure 4-1
Figure 4-2
LIST OF FIGURES
Schematic of a Gas Compressor Engine and Rod Packing
Rod Packing - Ring Detail
Rod Packing Cutaway with Static Pac™
Static Pac™ Actuation and Deactuation Process
Simplified Floor Plan of the Test Site
Compressor/Engine Configuration and Emissions Sources
Flow Tube Calibration at Low Flows (6/2/99)
Idle-mode Emissions
Operating Emissions
Flow Tube Repeatability (6/2/99)
Flow Tube Calibration at High Flows (8/12/99)
Page
1-3
1-4
1-5
1-6
2-3
2-6
2-10
3-2
3-4
4-3
4-5
Table 2-1
Table 3-1
Table 3-2
Table 3-3
Table 3-4
Table 3-5
Table 3-6
Table 3-7
Table 4-1
Table 4-2
Table 4-3
Table 4-4
LIST OF TABLES
Common Shutdown Scenarios and Emissions
Rod Seal Emissions of Natural Gas (Unit Idle & Pressurized)
Rod Seal Emissions of Natural Gas (Unit Operating)
Component Emissions
Engine Operating Schedule for Phase I
Overall Average Emission Factors
Case 1 and Case 2 Gas Savings (scf Natural Gas)
Static Pac™ Capital and Installation Costs
Flow Tube Calibration Results (Low Flows)
Flow Tube Calibration Results (High Flows)
Rotameter Calibration Results
Summary of Instrument Performance Data
Page
2-5
3-1
3-3
3-5
3-6
3-8
3-9
3-11
4-2
4-4
4-5
4-6
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ACKNOWLEDGMENTS
The Greenhouse Gas Technology Verification Center wishes to thank the staff and employees of ANR
Pipeline Company for their invaluable service in hosting this test. They provided the compressor station
to test this technology, and gave technical support during the installation and shakedown of the
technology. Some key individuals who should be recognized include Curtis Pedersen, Dwight Chutz,
Marilyn Wenzel, and Ron Sander. Thanks are also extended to Gary Swan of CMS Panhandle Eastern
Pipeline Company, and to the Center's Oil and Natural Gas Industry Stakeholder Group for reviewing
this report.
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1.0 INTRODUCTION
1.1 BACKGROUND
The U.S. Environmental Protection Agency's Office of Research and Development (EPA-ORD)
has created a program to facilitate the deployment of innovative technologies through
performance verification and information dissemination. The goal of the Environmental
Technology Verification (ETV) program is to further environmental protection by substantially
accelerating the acceptance and use of improved and more cost-effective technologies. The ETV
program is funded by the Congress in response to the belief that there are many viable
environmental technologies which are not being used for the lack of credible third-party
performance testing. With performance data developed under this program, technology buyers,
financiers, and permitters in the United States and abroad will be better equipped to make
informed decisions regarding environmental technology acquisitions.
The Greenhouse Gas Technology Verification Center (the Center) is one of 12 independent
verification entities operating under the ETV program. The Center is managed by EPA's partner
verification organization, Southern Research Institute (SRI), and conducts verification testing of
promising GHG mitigation and monitoring technologies. This Center's verification process
consists of developing verification protocols, conducting field tests, collecting and interpreting
field and other data, and reporting findings. Performance evaluations are conducted according to
externally reviewed Verification Test Plans and established protocols for quality assurance.
The Center is guided by volunteer groups of Stakeholders. These Stakeholders offer advice on
technology areas and specific technologies most appropriate for testing, help disseminate results,
and review test plans and verification reports. The Center's Executive Stakeholder group consists
of national and international experts in the areas of climate science, and environmental policy,
technology, and regulation. It also includes industry trade organizations, environmental
technology finance groups, various governmental organizations, and other interested groups. The
Executive Stakeholder Group helps identify and select technology areas for verification. For
example, the oil and gas industry was one of the first areas recommended by the Executive
Stakeholder Group as having a need for high quality performance verification.
To pursue verification testing in the oil and gas industries, the Center established an Oil and Gas
Industry Stakeholder Group. The group consists of representatives from the production,
transmission, and storage sectors. It also includes technology vendors, technology service
providers, environmental regulatory groups, and other government and non-government
organizations. This group has voiced support for the Center's mission, identified a need for
independent third-party verification, prioritized specific technologies for testing, and identified
broadly acceptable verification strategies. They also indicated that technologies that reduce
methane leaks from compressor rod packing are of great interest to the technology purchasers. In
the natural gas industry, interstate gas pipeline operators use large gas-fired engines to provide
the mechanical energy needed to drive pipeline gas compressors. In the U.S., fugitive natural gas
leaks from these compressors represent a major source of methane emissions, and a loss of
economic and natural resources.
To pursue verification testing on compressor rod packing technologies, the Center placed formal
announcements in the Commerce Business Daily and industry trade journals to invite vendors of
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commercial products to participate in independent testing. C. Lee Cook Division of the Dover
Corporation responded, and committed to participate in a medium-term independent verification
of their static sealing technology. The technology is referred to as the Static Pac™ and is
designed to reduce methane leaks from compressor rod seals during periods when the compressor
is in a standby and pressurized state.
Performance testing of the Static Pac™ was carried out at a compressor station operated by ANR
Pipeline Company (ANR) of Detroit, Michigan. The verification test was planned to be executed
in two phases where: Phase I evaluates short-term gas savings and documents installation costs;
and Phase II addresses longer-term technical and economic performance. This report presents the
results of the Phase I test, which occurred between July 15 and August 6, 1999.
Details on Phase I and II verification test design, measurement test procedures, and Quality
Assurance/Quality Control (QA/QC) procedures can be found in the Testing and Quality
Assurance Plan for the C. Lee Cook Division, Dover Corporation Static Pac™ System (SRI
1999/ It can be downloaded from the Center's Web site at www.sri-rtp.com. The Test Plan
describes the rationale for the experimental design, the testing and instrument calibration
procedures planned for use, and specific QA/QC goals and procedures. The plan was reviewed
and revised based on comments received from C. Lee Cook, ANR Pipeline, selected members of
the Oil and Gas Industry Stakeholder Group, and the EPA Quality Assurance Team. The plan
meets the requirements of the Center's Quality Management Plan (QMP), and conforms with
EPA's standard for environmental testing (E-4). In some cases, deviations from the Test Plan
were required. These deviations, and the alternative procedures selected for use, are discussed in
this report.
The remaining discussion in this section describes Static Pac™ technology and the goals of the
verification tests. Section 2 presents a background discussion of methane emissions from natural
gas compressors, descriptions of the test site, and the measurement system employed at the site.
Section 3 presents Phase I test results, and Section 4 assesses the quality of the data obtained.
1.2 THE STATIC PAC™ TECHNOLOGY
One of the largest sources of fugitive natural gas emissions from compressor operations is the
leakage associated with operating and idle-mode compressor rod packing. During standby
conditions, natural gas leaks into the atmosphere from the packing case and other compressor
emission sources. Based on an EPA/GRI study, reciprocating compressors in the gas
transmission sector were operating 45 percent of the time in 1992 (Hummel et al., 1996). If rod
leaks during standby operations are reduced or eliminated, significant gas savings and emissions
reductions could be realized. The C. Lee Cook Static Pac™ device is intended to provide this
benefit.
In general, compressor packing provides a seal around the rod shaft, keeping high-pressure gas
contained in the compressor from leaking out into the atmosphere. A typical compressor packing
case is shown in Figure 1-1 (see location No. 3). It consists of one or more sealing rings
contained within a case that serves several functions. These functions include: lubrication,
venting, purging, cooling, temperature and pressure measurement, leakage measurement, rod
position detection, and sealing for standby mode operations (GRI 1997). In conventional
packing, the sealing rings are configured in series to successively restrict the flow of gas into the
distance piece between the compressor and the engine. The sealing rings are held in separate
grooves or "cups" within the packing case, and are free to move laterally along with the rod and
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"float" within the grooves. The distance piece, shown between locations 3 and 4 in Figure 1-1,
typically vents rod packing leaks to the atmosphere.
Figure 1-1. Schematic of a Gas Compressor Engine and Rod Packing
1 Compressor Valves and Unioaders
2 Piston & Rider Rings
3 Packing Rings & Case
4 Oil Wiper Rings & Cases
A conventional packing case usually contains seven to nine cups. Each cup houses one or more
seal rings, which restrict the flow of natural gas into the atmosphere or out into the distance piece.
Each ring seals against the piston rod and also against the face of the packing cup. The first cup
is occupied by the breaker ring (see Figure 1-2), designed to reduce the pressure on the packing
rings by providing an orifice restriction to flow. A second function of the breaker ring is to
regulate the reverse flow of gas from the packing case into the cylinder. This reverse flow occurs
as the piston begins the intake stroke, and the pressure is rapidly reduced in the cylinder.
Cups 2 through 6 are occupied by conventional three-ring packing sets which consist of a "radial
cut" ring, a "tangent cut" ring, and a "backup" ring (see Figure 1-2). During the discharge stroke,
while the compressor is operating, pressure is exerted on each ring. This forces the rings to mate
against each other, and reduce leakage laterally along the rod. During this time, the tangent cut
ring constricts against the rod, reducing leakage past the rod surface. During the intake stroke,
pressure is rapidly reduced in the cylinder and gas flows from around the sealing rings back
toward the cylinder. During this cycle, the rings are free to move back and forth within the cups
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(depending on how much differential pressure is experienced between the discharge and intake
strokes and the movement of the rod). The final cup houses a vent control ring which can be used
to transport the leaking gas for subsequent use or discharge into the distance piece. A more
detailed description of rod packing is given in GRI's report documenting existing compressor rod
packing technology and emissions (GRI 1997).
Figure 1-2. Rod Packing - Ring Detail
During idle periods the unit remains pressurized, and pressure equalizes around the rings and they
can float within the cups. While they are floating, the pressure breaker rings and other rings
downstream of the packing do not stop gas leakage. As a result, rod packing leaks continue when
the rod motion has stopped. The leakage encountered during idle periods is due to the loss of
lubrication oil which normally fills the leak paths, changes in the shape of the ring as it cools, and
changes in rod alignment as the temperature changes (GRI 1997).
The Static Pac™ is a gas leak containment device designed to prevent rod packing leaks from
escaping into the atmosphere during compressor shutdown periods. The Static Pac™ system is
installed in a conventional packing case by typically replacing two cups in the low-pressure side
of the packing case (see Figure 1-3). When the compressor shuts down, an automatic actuation
valve is opened, admitting pressurized gas behind the internal piston. As shown in Figures 1-3
and 1-4, the movement of the piston wedges a lip seal into contact with the rod. When the
actuating pressure is lowered during compressor startup, the piston retracts, causing the Static
Pac™ seal to lift from the rod surface. A vent to atmosphere or some other low pressure area
such as the "doghouse", must be located downstream of the Static Pac™ in order for the seal to
actuate or release. A doghouse is an access port which is located between the engine and the
compressor. By removing this access port, site operators can perform routine maintenance on the
rod packing and its seals. Each doghouse contains an oil drain and a vent pipe; through which
leaks are routed out of the compressor building into the atmosphere. Leaks that normally occur
during periods of shutdown are reported by Cook to be completely or nearly eliminated.
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Figure 1-3. Rod Packing Cutaway with Static Pac™
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To allow room for the addition of the Static Pac™, a packing case with the Static Pac contains
one less ring set than conventional packing. It is speculated that this "missing seal" can cause
increases in rod emissions while the compressor is in operating mode. However, industry
experience suggests that the Static Pac™ should not affect normal sealing during compressor
operation. The Center was unable to locate reliable data to verify this claim. Therefore, the
verification test approach, described in Section 2.2, assesses the effect (if any) of the Static Pac
on normal sealing performance during compressor operation. This was accomplished by fitting
one rod on the test engine with a Static Pac and the second rod with a new conventional
packing. A second engine was fitted in the same manner to provide duplicate measurements.
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Figure 1-4. Static PacT Actuation and Deactuation Process
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"Static Pac" is a registered trademark of C. Lee Cook
covered by Patent No, 4469017.
1.3 VERIFICATION GOALS
Normal compressor shutdown and standby procedures vary from station to station. Some
operators depressurize and blow down all pressure from a compressor before standby. Others
depressurize the compressor to a lower but elevated pressure, while still others maintain full
1-6
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pressure during standby. Adding the Static Pac™ to a compressor may result in varying levels of
net gas savings and emission reductions depending on the shutdown procedure used. The
evaluation of the Static Pac™ focused on two shutdown procedures that represent the most
common approaches to compressor shutdown: remain pressurized during idle; and depressurized
(blowdown) before idle. Shutdown modes are discussed in Section 2.1. The Phase I and II
verification goals and parameters associated with these two compressor shutdown scenarios are
outlined below.
Phase I Evaluation:
Verify initial gas savings for primary baseline conditions
Document installation and shakedown requirements
Document capital and installation costs
Phase II Evaluation:
Document annualized gas savings for primary baseline conditions
Verify annual methane emission reduction
Calculate and document Static Pac™ payback period
Phase I goals were achieved through observation, collection and analyses of direct gas
measurements, and the use of site logs and vendor supplied cost and operational data. The
evaluation was completed after about a 3-week period. Initial gas savings were based on two sets
of manual emission measurements. The number and duration of shutdowns were determined
from site records provided by ANR Pipeline Company for the testing period, and for previous
years. Measured emission rates, site operational data, estimated gas savings, and installation
requirements are documented and verified in this report.
A primary goal of the Phase II evaluation is to determine the Static Pac™ payback period. As a
practical matter, the Center cannot conduct testing for the number of years that would be required
to determine payback from direct measurements. Thus, several Phase II goals will be
accomplished through a combination of medium-term measurements (several months) and data
extrapolation techniques. A Phase II report is planned for release in 2000.
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2.0 TECHNICAL BACKGROUND AND VERIFICATION APPROACH
2.1 METHANE EMISSIONS FROM NATURAL GAS COMPRESSORS
Fugitive natural gas emissions from compressor stations account for a significant loss in revenue
for gas companies and increase a company's unaccounted for gas losses. These emissions also
contribute to the release of methane, a potent greenhouse gas, into the atmosphere. Prior EPA
and Gas Research Institute studies estimated that reciprocating compressors emitted
approximately 21 percent of the total gas emissions (314 BCF) from the natural gas industry in
1992 (Harrison et al., 1996).
Methane emissions from compressors are liberated from a variety of different sources. These
sources include leaks from the rod packing, unit valves, blowdown valve, pressure relief valve,
and miscellaneous valves, fittings, and other devices. Emissions from blowdown operations are
also significant. One source of fugitive natural gas emissions is the leakage associated with
compressor rod packing. Most leaks occur from operating compressors, but emissions also occur
when some compressors are placed into a standby or idle mode while remaining pressurized.
According to an ongoing, multi-year compressor station fugitive emissions study conducted by
the Pipeline Research Committee (PRC), very little difference was observed between the overall
average value of running rod packing emissions and pressurized, but idle, rod emissions. The
overall average leak rate was approximately 1.86 cfm per rod (GRI 1997). This emission rate is
higher than the 0.86 cfm per rod reported previously in an EPA/GRI study (Hummel et al., 1996).
The PRC results are based on data collected from nine compressor stations, containing 56
reciprocating compressors and readings taken at 365 individual rod packings, compared to 135
measurements at six compressor stations in the EPA/GRI study. Nevertheless, both data sets are
very useful in quantifying average rod emission rates throughout the natural gas industry.
Fugitive emissions from standby or idle mode compressors are affected by the compressor
shutdown mode which varies from station to station. In general, the following procedures are
used:
• Maintain full operating pressure when idle (either with or without the unit
isolation valves open),
• Depressurize and blow down all pressure when idle (except a small residual
pressure to prevent air in-leakage) and vent the gas, either partially or
completely, to the atmosphere,
• Depressurize to a lower pressure, venting the gas either to the atmosphere or
to the station fuel system, or
• A combination of these procedures.
Based on the EPA/GRI study, the first two operating procedures represent the most common
approaches to compressor shutdown (Harrison et al., 1996). The study estimated that about 57
percent of idle transmission compressors are maintained at operating pressures and 38 percent are
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blown down to the atmosphere. A smaller percentage (less than 5 percent) are blown down to a
lower pressure, in some cases venting to the station's fuel system.
2.2 DESCRIPTION OF THE TEST SITE AND STATIC PAC™ INSTALLATION
Reciprocating compressors are the type most commonly used within the gas industry, and are a
primary source of compressor-related emissions. Thus, the Static Pac™ verification was
conducted at a transmission station that uses reciprocating compressors. ANR Pipeline Company
expressed interest in hosting the verification, and assisted the Center in identifying a
representative compressor station within their pipeline system. ANR reviewed its operations and
identified facilities where: the Static Pac™ was not currently used; at least one compressor
operates in a shutdown mode several times a year; and site operators could cooperate in support
of the short- and long-term evaluations.
The natural gas transmission engine/compressor selected to host the Static Pac™ operates six
Cooper-Bessemer engines (8-cylinder, 2000 hp), each equipped with two reciprocating
compressors operating in series (4,275 cubic inch displacement, 4-inch rods). The low-speed
engines at the site are typical of many used in the industry, but may not be typical of newer, high-
speed engines in use. The rods and packing cases have the same basic design and function as
most reciprocating compressors currently used and planned for use in the future in the
transmission sector. The rod packing is essentially a dry seal system, using only a few ounces of
lubricant per day. Wet seals, which use high-pressure oil to form a barrier against escaping gas,
have traditionally been employed. According to the Natural Gas STAR partners, dry seal systems
have recently come into favor because of lower power requirements, improved compressor and
pipeline operating efficiency and performance, enhanced compressor reliability, and reduced
maintenance. The STAR industry partners report that about 50 percent of new seal replacements
consist of dry seal systems.
Two engines, designated 801 and 802, were selected to verify the performance of the Static Pac™
system (see Figure 2-1 for a simplified floor plan). These two engines are the same age and have
similar operating hours, which is ANR's normal operating practice. Actual operating hours on
each engine are logged continuously. Each engine contains two compressor rods, and nine cups
are contained in each packing case. All rods are made of chrome-plated steel.
The Static Pac™ was installed on one compressor rod on each of the two engines. This rod is
referred to as the Test Rod. The packing material on the second rod on each engine was replaced
with new packing at the same time the Static Pac™ was installed. The second rod with the
conventional packing served as the Control Rod against which Static Pac™ performance could be
compared. The conventional packing normally used at the site is manufactured by C. Lee Cook.
The comparisons were conducted both for idle periods and while the engine was running (i.e., to
determine if the elimination of one of the seals in the Static Pac™ design affects normal sealing
performance during compressor operation).
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Figure 2-1. Simplified Floor Plan of the Test Site
Control Rod with Test Rod with
Conventional Packing Emissions Packing
Control Rod with Test Rod with
Conventional Packing Emissions Packing
2.3 VERIFICATION APPROACH
2.3.1 Establishing Baseline Conditions
According to C. Lee Cook, the Static Pac™ can provide static sealing during idle periods,
provided the compressor remains pressurized. The gas savings achieved depends on the emission
characteristics of the compressors packing, both before and after installation of the Static Pac™.
These savings also depend on the shutdown procedures used, and the number and duration of
shutdowns experienced. For example, a station that currently leaves compressors pressurized
during shutdown will achieve net savings from the decrease in rod packing leaks during idle
periods. Alternatively, if a station currently blows down compressors before shutdown, installing
the Emissions Packing would be associated with a change in operating practice to a pressurized
shutdown condition. A likely scenario for such a change would be that the station wishes to
eliminate blowdown emissions, and employs a static sealing system at the same time to reduce or
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eliminate any additional emission from the newly pressurized, rod packings. In this case, gas
savings occur by eliminating blow down emissions and unit valve leaks. However, there is a
potential for increases in emissions from components now exposed to high pressure during
shutdown.
For the two most commonly used compressor shutdown scenarios described in Section 2.1, Table
2-1 shows the relationship between compressor shutdown procedures and emissions. Because
use of the Static Pac™ system is associated with pressurized compressor standby operation, the
table indicates how compressor emissions may change from the emissions that occurred during
the original standby mode. Using this table as a guide, a verification plan was developed to
characterize all the emissions changes that may occur with the installation of the Static Pac™ and
the possible adoption of a different shutdown procedure.
The evaluation of the Static Pac™ performance at ANR Pipeline Company focused on the two
shutdown scenarios that collectively represent practices employed by about 95 percent of the
transmission compressors (Shires and Harrison 1996). Case 1 represents compressors that remain
pressurized when idle, and Case 2 represents compressors that completely depressurize and blow
down all gas. The host site was asked to follow these practices during testing, although their
normal practice is to maintain idle pressures of about 120 psig and recover all blowdown gas into
the engine fuel system. The following discussion highlights the verification issues for each case
and outlines measurements and data collection activities implemented in the verification test.
2.3.1.1 Case 1
Case 1 represents a compressor that normally maintains full operating pressure during idle
periods. For this case, a change in emissions was anticipated to occur only at the rod packing due
to the static sealing action of the Static Pac™. To quantify this potential change in rod packing
leaks, direct methane emission rate measurements were conducted on the distance piece or
doghouse vent pipes associated with the Control Rods and Test Rods for each of the two engines.
Because the unit pressure is essentially unchanged during both operating and idle periods, all leak
rates from other components (pressure relief valve, blowdown valve, unit valves, and
miscellaneous flanges, valves, and fittings) can be assumed to remain constant after the
installation of the Static Pac™. The idle-mode emissions from the two Control Rods are
compared to idle-mode emissions from the two Test Rods. The difference between these two
values are determined, and used to quantify the static sealing abilities of the Static Pac™.
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Table 2-1. Common Shutdown Scenarios and Emissions
Matrix of Shutdown Procedure Changes
Procedure or Emission
Source
CASE 1
CASE 2
Current shutdown
procedure
Pressurized shutdown with
unit valves open or closed3
Blowdown/100% vent to
atmosphere
Procedure with emissions
packing
n/c
Pressurized shutdown
Matrix of Possible Emissions Changes Due to Shutdown Procedure Changes or
Installation of the Emissions Packing
Rod seals
Decrease
Little or no increase
Blowdown volume
n/cb
Decrease
Unit valve seat (via open
blowdown line)
n/c
Decrease
Blowdown valve
n/c
Increase
Pressure relief valve
n/c
Increase
Misc. valves, fittings,
flanges, stems etc.
n/c
Increase
a Most sites leave the unit valves closed for safety reasons (i.e., sites may not want problems in the shutdown
engine to affect the integrity of the entire station).
b n/c - no change/effectively no change
Shaded area represents measured parameters.
For Case 1, the savings consist solely of gas prevented from leaking from the rod packing during
idle periods. This is the difference between the leak rate without the Static Pac™ (measured for
the Control Rods) and the leak rate with the Static Pac™ (measured for the Test Rods). Equation
1 states how gas savings will be calculated.
G1 = [Qu - Qs] * t (Eqn. 1)
where,
G1 = average gas savings for the Phase I test period (Case 1), scf
Qu = average uncontrolled leak rate during idle (Control Rod), scfm
Qs = average controlled leak rate during idle (Test Rod), scfm
t = total shutdown or idle time during Phase I, minutes
2.3.1.2 Case 2
Case 2 represents a compressor that normally blows down from operating pressure to a minimum
pressure during idle periods. At such times the pressure on compressor components is reduced to
near atmospheric. Consequently, leaks from rod packing, pressure relief valves, and blowdown
valves cease to exist. However, leaks from the unit valves, which are closed to isolate the
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compressor from the pipeline, are liberated into the atmosphere. This gas leaks past the unit
valves, into the compressor system, and out into the atmosphere via the open blowdown valve.
Figure 2-2 is a simplified diagram of these emission sources. Because emissions associated with
leaking unit valves can be substantial, measurements were made to quantify these emissions after
blowdown was completed. When the Static Pac™ is installed, and a pressurized shutdown
eliminates the unit valve leaks, this gas represents a savings associated with the use of the Static
Pac™. In addition, the compressed gas contained in the compressor and lines is lost during
blowdown. This gas must also be considered as a savings associated with the Static Pac™, and
was calculated based on known volumes of compressor components and the measured operating
pressure. All of these emission savings are added to the savings determined for the rod packing
as described above, resulting in a total gas savings value for the Static Pac™.
Figure 2-2. Compressor/Engine Configuration and Emissions Sources
Blowdown Valve and Vent
In contrast, emissions can increase from several components which are now exposed to high
pressure. Ultimately, these leaks decrease the net gas savings associated with the Static Pac™.
To verify this, methane emission rate measurements were conducted (during pressurized idle-
mode) on all components newly exposed to elevated pressures as a result of the pressurized
shutdown. These components include the pressure relief valve, the blowdown valve, and various
flanges, connectors, and valves. Emissions from these devices are subtracted from the total
savings above, to yield the net savings associated with the Static Pac™.
2-6
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It is assumed that, following installation of the Static Pac™ and after a pressurized shutdown is
adopted, the unit valve would be placed closed during shutdown (this was the host site's
procedure). Compressor pressures were monitored during shutdown to determine if the pressure
slowly dropped due to this closed valve, or if leaks from the closed valve were sufficient to
maintain full compressor pressure.
For Case 2, gas savings consist of the blowdown volume (times the number of idle periods) and
the unit valve leak rate (times the duration of idle periods). In addition, there are gas leakages
from the blowdown valve, pressure relief valves, and miscellaneous components. Additionally,
any gas that escapes past the Static Pac™ is lost (i.e., pressurized conditions may result in
packing case leaks which are essentially zero during non-pressurized/blowdown conditions). For
Case 2, the gas savings for each idle period were calculated as follows.
G2 = BDV + Quv * t — [Qprv Qbdv Qmisc Qs] * t (Eqn. 2)
where,
G2 = gas savings for each idle period (Case 2), scf
BDV = blowdown volume times the number of blowdowns during the Phase I period, scf
Quv = unit valve leak rate, scfm
Qprv = pressure relief valve leak rate, scfm
Qbdv = blowdown valve leak rate, scfm
Qmisc = aggregate leak rate for miscellaneous components, scfm
Qs = test rod leak rate, scfm
t = idle time over the Phase I test period, minutes
2.3.1.3 Impact on Normal Running Emissions
With the Static Pac™ system, the packing case is modified, resulting in one less set of rings than
conventional packing cases. With this change, there is a potential to alter the emission sealing
performance of the overall packing system (i.e., cause an increase or decrease in packing
emissions compared to the standard packing). To address this, measurements were conducted on
the test and control rods, with the compressors in a normal operating state. It is assumed that
after installation of the Static Pac™, the unit valve position (i.e., closed or open) would remain
the same as before the Static Pac™ was installed. Any implied running emission changes were
integrated into the assessment of net gas savings for the Static Pac™ system.
For example, if it was determined that the Static Pac™ caused any increase in emissions during
normal compressor operation (see later discussion on running emissions), these emissions were
subtracted from the gas savings. The following equation states how the total gas savings will be
calculated for each case. The total gas savings, G1T and G2T, for Case 1 and Case 2, respectively,
Are given in equations la and 2a.
G1j — G1 - Vm (Eqn. 3)
Where, Vm is any increase in operating emissions that occurred over the test period due to the
Static Pac™. Vm is the difference in operating emissions (i.e., emissions during non-idle periods)
between the Test and Control rods, times the number of minutes the compressor operated during
the Phase I test period.
2-7
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G2t = G2 -Vm
(Eqn. 4)
2.3.2 Emission Measurements and Calculations
The following discussion provides an overview of the measurements made, instruments used,
field procedures followed, and key calculations made in the Phase I tests. For more detail on
these topics, the reader should consult the Test Plan titled Testing and Quality Assurance Plan for
the C. Lee Cook Division, Dover Corporation Static Pac™ System (July 1999). It can be
downloaded from the Center's Web site at www sri-rtp.com.
To characterize the running emissions and Case 1/Case 2 idle emissions, manual emission
measurements were collected on the following sources: doghouse vent, unit valve seat (via the
open blowdown line), pressure relief valve vent, blowdown valve vent, and miscellaneous
components (e.g., fittings, connections, valve stems). Tests were performed when the engine was
pressurized and running, pressurized and idle, and depressurized and idle. For the rod packing
leaks, tests were performed when the engine was pressurized and running, and pressurized and
idle. Measurements of the leak rate for the blowdown valve, pressure relief valve, and
miscellaneous other components were made when the unit was pressurized and idle. The unit
valve leak rate measurement was made with the unit blowndown and the blowdown valve closed.
The measurements made and operating conditions under which testing was performed are listed
below. One full day was needed to conduct this suite of measurements on both engines.
• With both units shut down and pressurized: natural gas leak rates for the
pressure relief valve, blowdown valve, miscellaneous components, and rod
packing vents (test rod and control rod)
• With both units blown down: natural gas leak rates for the unit valve and unit
valve stem
• With both units running: natural gas leak rates for the doghouse vents (Test
Rod and Control Rod)
Measured natural gas leak rates were converted to methane leak rates using natural gas
compositional measurements (about 97 percent methane) provided by ANR Pipeline.
The station agreed to a limited number of scheduled shutdowns for the purpose of conducting the
measurements described above. Results from these tests were used to characterize emission rates
at the time of testing, and to characterize emissions differences between Cases 1 and 2, above.
Net gas savings were calculated based on the number and duration of idle periods encountered at
the site for the test period.
2.3.2.1 Rod Leak Rate Measurements
Emissions from the packing case vent and leaking rod seals are both vented into the distance
piece or doghouse described in Section 1.2. Both emission sources vent gas that has escaped the
2-8
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sealing action of the packing, and are included together when measuring emissions. After
emissions are discharged into the doghouse, they are vented to the atmosphere through the
doghouse vent. After soap screening all doghouse seals and connections and monitoring the
long-term compositional trends of the gas exiting the doghouse, it was determined that no other
gas was entering the doghouse. The doghouse vent and oil drain were the only paths by which
emissions escaped into the atmosphere. For the test, the doghouse oil drain was sealed using ball
valves, which forced all emissions to exit through the doghouse vent.
To measure these emissions, a Flow Tube was used to measure vent gas velocity, and a
hydrocarbon analyzer was used to measure vent gas total hydrocarbon (THC) concentration
before flow measurement started. In the original Test Plan, sensitive, low-pressure-drop
continuous flowmeters were planned for use, but after their installation, it was determined that the
pressure in the doghouse vents was so low that reliable flow detection could not be established.
With this discovery, the decision was made to proceed with testing, and to use sensitive manual
methods to conduct the measurements.
The Flow Tube consists of a sensitive 1-inch vane anemometer mounted on the inside walls of a
polyvinyl chloride (PVC) tube that measures 30 inches in length and 1 inch in diameter. Just
before taking velocity readings, the hydrocarbon concentration in the doghouse vent was
measured using a portable hydrocarbon analyzer. The analyzer used was a Bascom-Turner CGI-
201, with a 4-100 percent total hydrocarbon range, and an accuracy of 2 percent of the measured
concentration. The CGI-201 measures all primary hydrocarbon compounds found in natural gas
including methane, ethane, propane, and butane.
Before each trip to the site for on-site measurements, the Flow Tube was laboratory-calibrated
using a NIST-traceable Laminar Flow Element and a wide range of simulated natural gas flow
rates (99 percent methane, 0.3 to 4 scfm). These calibrations were used to generate a calibration
curve which spanned the range of flow rates anticipated for the site. This curve was used to
select a natural gas flow rate based on the indicated velocity from the flow tube. An example
calibration chart is shown in Figure 2-3.
2-9
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Figure 2-3. Flow Tube Calibration at Low Flows (6/2/99)
Gas Velocity (fpm)
For each doghouse vent, a minimum of 10 separate gas velocity readings were measured with the
Flow Tube. These measurements were made after the doghouse emissions were observed to
stabilize (15 to 20 minutes after the vents were opened). In most cases, the 10 readings showed
stable emissions. Each measurement represents a 16-second average value and, after completion,
all values were averaged to yield an overall average total gas flow rate in feet per minute. Using
this value, a natural gas flow rate was selected from the flow tube calibration curve.
The Flow Tube has a Lower Detectable Limit (LDL) of 0.12 scftn (i.e., flow rates below this
value cannot be reliably detected with the instrument). When gas flows lower than the LDL were
encountered, the anemometer inside the Flow Tube was visually inspected to confirm that the
vane was turning. In these cases, a confirmation of the movement of the vane suggested that gas
was indeed flowing through the tube, but at a rate less than the LDL. For these measurements, a
gas flow rate equal to half the LDL (0.06 scfm) was assigned. If the vane anemometer was
observed to be not turning, a gas flow reading equal to 0 scfm was assigned.
It should be noted that, after opening the doghouse vent for measurement, air typically enters and
mixes with the natural gas leaking from the rod packing. The average THC level in the gas flows
measured on the Control Rod was 85 percent, and on the Test Rod the level was 91 percent
(running and idle). Given sufficient time, the rod leaks would completely purge all air from the
doghouse, allowing direct measurement of pure natural gas with the Flow Tube. As a practical
matter, this could not be done routinely. Based on the Center's experience with characterizing
doghouse vent emissions at several compressor facilities, it is believed that the rod packing leak is
the driving force which results in gas escaping through the vents (i.e., only one outlet stream is
2-10
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present for the gas to escape and no other gas can enter the doghouse). As such, it is assumed that
the flow rate measured during testing is representative of the flow rate of pure natural gas. This
assumption was verified by monitoring composition on two vents over time (about 1 hour), and
verifying that the composition eventually reached 92 to 94 percent THC.
2.3.2.2 Component Leak Rate Measurements
Manual measurements were made for the pressure relief valves, unit valves, blowdown valves,
and miscellaneous components. The Center was unable to obtain a license in time to use the GRI
Hi-Flow device as described in the Test Plan. Consequently, the Flow Tube, proven to be reliable
on other similar measurements conducted by the Center, was used for this test.
The leak rates for the blowdown valve and pressure relief valve were measured with the unit
shutdown and pressurized. Measurements for miscellaneous components were also made with
the unit pressurized. Leak rates for the unit valve were measured with the unit depressurized and
the valve closed.
The pressure relief valves vent through a 6-inch standpipe extending to the roof of the compressor
building. Access to the roof was limited, and posed a hazard to the testing personnel. Thus, a
hydrocarbon analyzer was first used to determine if leaks were present. If hydrocarbons were
detected, the Flow Tube was to be used to quantify the gas flow rates. With the exception of
making a direct connection to the 6-inch standpipe outlet, the sampling and calibration procedures
described in the previous section apply to this emission source as well.
Flow measurements were conducted at an existing port, located immediately downstream of the
unit valves in the suction line of each compressor. During compressor shutdown, any leaks from
the seats of the unit valves will exit through this opened port. The leak rate for the unit valves
was the highest flow measured at the host site. The leak rate was measured using the same Flow
Tube applied to the rod packing vents. The anemometer mounted within the tube has the capacity
to measure the high flows that occurred (e.g., a maximum of 6,500 fpm or about 25 cfm of natural
gas could be measured). However, a different calibration chart from the one presented in Figure
2-1 was used to determine emission rates at the higher flows encountered with unit valves leaks
(see Section 4 for more information on calibration).
The leak rate for the blowdown valve was measured at the flange located at the exit of the valve.
To make this measurement, it was necessary to unbolt the flange, then separate the two sides by
about 1 inch and then insert a disk. The disk contained channels that allowed the leak to be
captured and directed into a small, sensitive low-flow-rate rotameter (Dwyer VB Series, 0 to
lOOOmL/min with a published accuracy and precision of +3 percent). The Flow Tube could not
be used here because early field results indicated that relatively low flow rates existed at this
location. The low-flow-rate rotameter was used because of the poor performance of the Flow
Tube at these low flows.
The miscellaneous components at the test site consist of pressure and temperature metering taps,
fittings that connect the taps to data transmitters, and valves used to recover gas for the fuel
recovery system. The host station normally vents to a specially designed gas recovery system
during shutdown, but performed a blowdown procedure for this verification, allowing an
assessment of the Case 1 and Case 2 shutdown scenarios described above. Significant leaks were
not expected at these locations; however, all components were soap screened and any leaks
identified were to be quantified using the EPA protocol tent/bag method.
2-11
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2.3.2.3 Natural Gas Composition Measurements
On-site natural gas compositional analysis is performed by ANR personnel. The site operators
use a gas chromatograph (Daniel Model #2251) to determine the concentration of methane,
hydrocarbons, and inert gas species present in the pipeline gas. The gas chromatograph is
capable of measuring 0 to 100 percent methane, with an instrument accuracy and precision of
+0.02 percent of full range. The instrument is calibrated each month using 97.0 percent certified
methane gas.
The Center obtained copies of the fuel gas analyses results and their calibration records which
corresponded to the Phase I measurements. An average methane concentration was calculated for
those days when sampling was conducted. This value was multiplied by the natural gas savings
measured for each case to calculate the standard cubic feet of methane saved.
2.3.2.4 Blowdown Volume Determination
The blowdown volume represents gas contained in the test compressor, engine, auxiliary piping,
and all components located downstream of the unit valves. Based on records obtained from ANR,
the total gas volume present in this equipment is 176 cubic feet. ANR engineers determined that
at 700 psig pressure, 9,200 standard cubic feet natural gas occupies this volume (corrected for the
compressibility factor). Because it is not feasible to directly measure the blowdown volume,
9,200 scf was used to represent the total gas that would be released into the atmosphere each time
the test compressor was depressurized from 700 to 0 psig.
2.3.3 Site Operational Data
The number and duration of shutdown/idle periods must be specified to calculate the gas savings
that occurred during the 3-week Phase I evaluation. Site records, provided by ANR pipeline, were
used to determine the number and duration of shutdowns for the Phase I period. The ANR
records identify daily compressor operating hours and the total hours the compressor was
available (i.e., scheduled shutdown for maintenance is not included in the available hour values).
Subtraction of the total available hours from the total operating hours yields the number of hours
each unit was on idle. Because the number and duration of shutdowns were manipulated by the
Center to ensure collection of the necessary measurements, those shutdowns that occurred at the
Center's request were also subtracted.
The number of blowdowns was determined by accounting for each occurrence of an idle period.
(It should be noted that this is an estimated value because the test site does not normally
blowdown, but rather maintains a minimum pressure of 120 psig operating pressures during idle
periods.) The number of blowdown occurrences assigned for the Case 2 evaluation is a synthetic
value for sites that follow blowdown procedures.
2-12
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3.0 RESULTS
3.1 ROD PACKING EMISSIONS
3.1.1 Emissions During Idle/Shutdown
Table 3-1 presents the measured packing vent emissions for Engines 801 and 802 during
pressurized idle states, and Figure 3-1 illustrates the relative differences in emissions between the
two engines. Five daily measurements were collected over the Phase I sampling period. These
data span the range of time from when the packing was new until the packing had logged about
1900 hours of wear. Measurements were generally started 20 minutes after shutdown occurred,
and required about 30 minutes to complete. Thus, the values reported below are representative of
average emissions that occurred within about 45 minutes of compressor shutdown (unless the
engine had been shut down overnight).
Table 3-1. Rod Seal Emissions of Natural Gas
(Unit Idle & Pressurized)
Date
Approx. Run
Time on New
Seals (hrs)
Control Rod /
Test Rod
Engine Idle,
Pressurized a 700 psi
Difference Between
Control Rod and
Test Rod,c
scfm natural gas
Control Rod With
Conventional Packing,
scfm natural gas
Test Rod With
Static Pac™,
scfm natural gas
ENGINE 801
7/15/99
17/1340
0.92
<0.12 a
0.86
7/16/99
37/ 1365
0.72
<0.12a
0.66
8/4/99
520/ 1850
<0.12a
0b
0.06
8/5/99
540 / 1870
<0.12a
0b
0.06
8/6/99
563 / 1893
0.50
0b
0.50
ENGINE 802
7/15/99
1/1
2.44
<0.12a
2.38
7/16/99
19/19
0.79
<0.12a
0.73
8/4/99
509 / 509
<0.12a
<0.12a
0
8/5/99
533 /533
1.13
0b
1.13
8/6/99
559/559
0.40
0b
0.40
a For these samples, half the Lower Detectable Limit (0.06 scfm) was assigned because the vane anemometer inside
the Flow Tube was visually confirmed to be moving during low flow conditions.
b For these samples, no movement of the vane anemometer was observed. An emission rate of 0 scfm is assigned.
c Difference = (Control Rod Emissions - Test Rod Emissions), positive values indicate gas savings are achieved.
In all cases, no flows were detected with the Static Pac™ during standby operation (i.e., gas
velocities were less than the instrument LDL). For 50 percent of the samples, the vane
anemometer was observed to be turning, but the emission rate was below the LDL to display a
reading. For these samples, a flow reading equal to half the LDL (0.06 scfm) was used to
calculate gas savings. For the remaining samples with flows less than the LDL, an emission
value of 0 scfm was assigned.
3-1
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Figure 3-1. Idle-Mode Emissions
7/15 7/16 8/4 8/5
-Control Rod ^^^Test Rod
On Engine 801, the Static Pac™ was installed for the longest duration (about 1900 hours), and
had time to be broken in. The average idle emissions on this Test Rod were 0.43 scfm natural gas
lower than on the Control Rod. The performance was just as good for Engine 802, which
contained the newest set of Static Pac™. The average emission reduction achieved on this engine
was 0.93 scfm natural gas. Averaging the data from both engines, the overall average emission
reduction with the Static Pac™ was 0.68 scfm natural gas (or 0.66 scfm CH4). This is equivalent
to a net emissions reduction of 96 percent with the use of a Static Pac™.
3.1.2 Emissions During Compressor Operation
Table 3-2 presents the measured packing vent emissions for Engines 801 and 802 during
compressor operation. As before, five daily average natural gas emission rates are reported for
each vent, and these data span the range of time from when the packing was new, until the
packing had logged about 1900 hours of wear. Measurements were initiated at least 30 minutes
after startup.
3-2
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Table 3-2. Rod Seal Emissions of Natural Gas
(Unit Operating)
Date
Approx. Run
Engine Running @ 700 psi
Difference Between
Time on New
Control Rod and
Seals, hrs
Control Rod With
Test Rod With Static
Test Rod,c
Control Rod /
Conventional Packing,
Pac™,
scfm
Test Rod
scfm of natural gas
scfm of natural gas
ENGINE 801
7/15/99
17/1340
0.87
0.43
0.44
7/16/99
37/ 1365
0.71
0.38
0.33
8/4/99
520/ 1850
0.48
0b
0.48
8/5/99
540 / 1870
0.42
0b
0.42
8/6/99
563 / 1893
0.49
0b
0.49
ENGINE 802
7/15/99
1/1
1.67
2.35
-0.68
7/16/99
19/19
0.92
1.06
-0.14
8/4/99
509 / 509
<0.12a
0.70
-0.64
8/5/99
533 /533
0.76
1.35
-0.59
8/6/99
559/559
0.47
0.68
-0.21
a For these samples, half the Lower Detectable Limit (0.06 scfm) was assigned because the
vane anemometer inside
the Flow Tube was visually confirmed to be moving during low flow conditions.
For these samples, no movement of the vane anemometer was observed. An emission rate of 0 scfm is assigned.
c Difference = (Control Rod Emissions - Test Rod Emissions), positive values indicate gas savings are achieved.
For Engine 801, the Static Pac™ had overall average emissions that were 0.43 scfm natural gas
lower than the conventional packing. Conversely, on Engine 802, the Static Pac™ running
emissions were about 0.45 scfm natural gas higher than the conventional packing. Figure 3-2
plots the running emissions for both engines. As these data suggest, the variability between the
Test and Control Rod emissions is similar, with the exception that the Static Pac™ emissions are
lower for Engine 801 and higher for Engine 802. It is speculated that Engine 801 is showing
improved performance because the Static Pac™ on this engine was older, and had ample time to
be broken in. Averaging the data from both engines together, the Test Rod and Control Rod
produced overall average emissions that were 0.70 scfm natural gas (or 0.68 scfm CH4),
indicating no change in running emissions due to the Static Pac™.
3.2 OTHER EMISSION SOURCES
3.2.1 Valve Leaks and Blowdown Volume
Measurements were conducted to quantify emissions associated with the closed and pressurized
blowdown valve, pressure relief valve, and unit valves. These measurements represent the
emissions leaking past the valve seats on each device. Estimates of the emissions associated with
compressor blowdown operations are also presented, and are based on ANR-supplied gas
pressures and equipment volumes. The sources addressed in this section are among the most
significant fugitive emission sources associated with compressor operations. Measurements
associated with the remaining minor sources (e.g., valve stems, fittings, and other minor fugitive
sources) are addressed in Section 3.2.2.
3-3
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Figure 3-2. Operating Emissions
Sampling Dates
Control Rod ^^^Test Rod
The results of these measurements are presented in Table 3-3. There were no detectable
emissions from the blowdown valve and the pressure relief valve. Emissions from the unit valve
were high and relatively consistent. The overall average emission rate was 4.86 scfm. The blow-
down volume is constant (9,200 scf/event) because the operating pressure and equipment volume
remained the same.
3.2.2 Miscellaneous Fugitive Sources
Once each day, miscellaneous fugitive emission sources were soap screened to identify
components that were leaking significantly and in need of emission-rate measurement. The types
of components screened are:
• Flanges - Valve, meter, pipe, and other flanges
• Miscellaneous fittings (tees, elbows, couplings, drains, ports, small valves)
• Blowdown gas recovery system components
The soap screening revealed no leaking components. This is not surprising, because most of
these components are located in confined working areas, and any leaks could result in a
significant safety hazard or triggering of the gas detection alarm system located at the site.
3-4
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Table 3-3. Component Emissions
Date
Blowdown Valve,
Pressure Relief
Unit Valve,b
Blowdown
scfm natural gas
Valve,
scfm natural gas
Volume,0
scfm natural gas"
scf natural gas/event
ENGINE 801
7/15/99
0.00
0
3.31
9,200
8/4/99
0.00
0
6.22
9,200
8/5/99
0.00d
0
6.46
9,200
8/6/99
0.00d
0
5.39
9,200
ENGINE 802
7/16/99
0.00
0
2.82
9,200
8/4/99
0.00
0
5.49
9,200
8/5/99
0.00d
0
5.00
9,200
8/6/99
0.00d
0
4.20
9,200
a Zero
emissions are assigned because screening with a hydrocarbon analyzer did not detect
measurable levels.
Represents total emissions from both unit valves on the engine.
0 Based on calculations performed by ANR engineers. This value represents the total volume of gas
present in the test compressor, piping, and all equipment located downstream of the unit valves (at
700 psig).
Zero values are assigned based on readings taken on August 4.
3.3 NET GAS SAVINGS
The primary verification parameter determined for the Phase I evaluation is net gas savings. The
Phase I test period began after the new seals were installed and the engines were started (July 15,
1999), and ended on the last day of sampling (August 6, 1999). Net gas savings for the Phase I
period were calculated for the Case 1 and Case 2 baseline shutdown scenarios based on the
overall average emission rates presented in Sections 3.1 and 3.2 and engine operational data
presented in the next section.
3.3.1 Compressor Operational Characteristics
To calculate net gas savings, the operational characteristics of both engines were defined on a
daily basis. The operating characteristics of interest include the number of shutdowns, the
number of hours in the idle mode, the number of hours in the running or operating mode, and the
number of hours in the out-of-service mode (i.e., non-idle-mode such as maintenance and repair).
These operating characteristics, presented in Table 3-4, were defined for Engines 801 and 802
using data supplied by ANR Pipeline. The gray areas in the table correspond with sampling
conducted by the Center. Although several idle-mode shutdowns occurred on these days, they are
not included in the determination of gas savings because these shutdowns were performed at the
request of the Center. For the Phase I test period, Engine 801 was operating in the idle mode
about 10 percent of the time, while Engine 802 was idle about 15 percent of the time.
3-5
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Table 3-4. Engine Operating Schedule for Phase I
Engine
Date
Number of
Shutdowns
Operational Data (Hrs)
Running
Out of Service
Idle
801
15-Jul
16-Jul
*
17-Jul
24
0
0
18-Jul
24
0
0
19-Jul
1
15.2
0.1
8.7
20-Jul
13.8
2.8
7.4
21-Jul
24
0
0
22-Jul
24
0
0
23-Jul
24
0
0
24-Jul
24
0
0
*
25-Jul
24
0
0
26-Jul
24
0
0
27-Jul
1
13.9
0
10.1
2 8-Jul
9.7
6.4
7.9
2 9-Jul
23.7
0.3
0
30-Jul
24
0
0
31-Jul
24
0
0
1-Aug
24
0
0
2-Aug
24
0
0
3-Aug
24
0
0
4-Aug
5-Aug
6-Aug
TOTAL
2
340.3
9.6
34.1
802
15-Jul
16-Jul
*
17-Jul
0
0
24
18-Jul
1
0
0
24
19-Jul
0
0
24
20-Jul
14
0.1
9.9
21-Jul
24
0
0
22-Jul
24
0
0
23-Jul
24
0
0
24-Jul
24
0
0
*
25-Jul
24
0
0
26-Jul
24
0
0
27-Jul
24
0
0
2 8-Jul
24
0
0
2 9-Jul
24
0
0
30-Jul
24
0
0
31-Jul
24
0
0
1-Aug
24
0
0
2-Aug
24
0
0
3-Aug
24
0
0
4-Aug
5-Aug
6-Aug
TOTAL
1
350
0.1
81.9
* Engine operating data were not available for these days. It was assumed that the operational schedule for these days was
similar to the schedule that occurred on the following day.
Gray areas correspond with sampling conducted by the Center/
3-6
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3.3.2
Case 1 and Case 2 Gas Savings
This section presents calculated gas savings associated with the Cook Static Pac™ for Engines
801 and 802. Savings are computed by comparing compressor emissions when the Static Pac™
is installed, with compressor emissions without the Static Pac™. The Static Pac™ requires that a
pressurized shutdown/idle mode be used, and the gas savings achieved will be affected by how
shutdown and idle mode operations are used prior to installing the Static Pac™.
Two base-case shutdown/idle modes are assumed. Case 1 represents the original use of a
pressurized shutdown (same as Static Pac™ requires), and Case 2 represents the original use of
compressor depressurization and blowdown. As a result of changing the packing, and possibly
the shutdown/idle mode, a variety of emission changes will occur in both cases. Each change is
quantified here, and the bullets below describe how each value is calculated. The emission
factors referred to below are described in Sections 3.1 and 3.2, and are summarized in Table 3-5.
CASE 1 (no change in shutdown/idle mode; i.e., pressurized shutdown/idle continues):
• Rod seal savings while idle:
Description: Rod packing emissions that are reduced by the Static Pac™ during idle periods
Calculation: Idle hours *(Control Rod emission factor - Test Rod emission factor)
• Rod seal losses due to emissions increases while running:
Description: Rod packing emissions increases caused by the Static Pac™ during operation
Calculation: Running hours*(Control Rod emission factor - Test Rod emission factor)
CASE 2 (change from depressurize/blowdown mode to a pressurized mode):
• Rod seal increases while idle:
Description: Idle-mode rod packing emissions from Static Pac™ (with new pressurized shutdown/idle
mode, these emissions must now be added)
Calculation: Idle hours* (Test Rod emission factor)
• Rod seal losses due to emissions increases while running: same as in Case 1
• Blowdown volume savings:
Description: Gas contained in the compressor and piping released during shutdown (with new
pressurized shutdown/idle mode, these emissions are no longer released)
Calculation: Number of shutdowns* (blow down volume emission factor)
• Blowdown valve leak losses:
Description: Gas released from the closed blowdown valve (with new pressurized shutdown/idle mode,
these emissions must now be added)
Calculation: Idle hours* (blow down valve emission factor)
• Unit valve leak savings:
Description: Gas released from the closed unit valves (with new pressurized shutdown/idle mode, these
emissions are no longer released)
Calculation: Idle hours *(unit valve emission factor)
• PRV and miscellaneous component losses
Description: Gas released from the pressure relief valve and miscellaneous fugitive sources (with new
pressurized shutdown/idle mode, these emissions must now be added)
Calculation: Idle hours* (PRV + Miscellaneous components' emission factors = 0)
3-7
-------
Table 3-5. Overall Average Emission Factors (scfm gas)
Control Rod ldk-
0.71
Test Rod idle
0.03
Control Rod running
0.70
Test Rod running
0.70
Blowdown Volume
9,200 / shutdown
Blowdown Valve
0.00
Unit Valve
4.86
Pressure Relief Valve and Misc.
Components
0
Table 3-6 presents the gas savings for Cases 1 and 2. The definitions above correspond to
specific columns in the table. The results show there are significant differences in gas savings
between Engines 801 and 802, but these differences are driven primarily by differences in the
number of idle hours that occurred during Phase I. Total natural gas savings for both engines
under Case 1 were calculated to be 4,733 scf natural gas, or savings of about 41 scf natural
gas/standby hour for each Test Rod. These gas savings occurred because the Static Pac™
reduced to 96 percent of emissions during the idle mode compared to the Control Rod. Total
natural gas savings for both engines under Case 2 were calculated to be 61,217 scf natural gas, or
savings of about 528 scf natural gas/standby hour for each Test Rod. For this case, the change in
operating characteristics provided significant benefits. Elimination of the blowdown volume in
Case 2 was the primary factor contributing to the gas savings that occurred.
From a greenhouse gas emissions standpoint, the natural gas savings and losses cited above were
converted into methane emissions/losses by using natural gas compositional data routinely
measured by ANR pipeline (see Section 2.3.2.3). An average 97.18 percent methane composition
was measured during the Phase I test period by ANR and, based on this value, total methane
reductions (savings) and increases were:
Case 1: Total methane decrease of 4,597 scf (1,352 and 3,245 scf CH4 for Engines 801 and 802,
respectively)
Case 2: Total methane decrease of 59,491 scf (27,484 and 32,006 scf CH4 for Engines 801 and 802,
respectively)
3.3.3 Estimated Gas Savings For Other Compressor Rods
The natural gas emission rates encountered at the test site were lower than the emission rates
reported for rod packing leaks in the natural gas industry. Specifically, the EPA/GRI study
reported an average rod packing leak rate of 1.0 cfm per rod (Hummel et al., 1996), while the
PRC study reported an average leak rate of 1.9 cfm per rod (GRI 1997). To estimate potential gas
savings that could be achieved for rods with higher emission potentials, the verification test data
summarized above were used. An emission reduction of 96 percent was applied to represent gas
savings achieved with the Static Pac™. All other parameters, including engine operating data
and component emission rates, were assumed to be identical to the test site. The following
summarizes natural gas savings expected to be achieved for sites characterized by the average rod
packing leak rate of 1.9 cfm:
Case 1: Total gas savings equal 12,695 scf (3,732 and 8,963 for Engines 801 and 802, respectively)
Case 2: Total gas savings equal 60,897 scf (28,188 and 32,709 for Engines 801 and 802, respectively)
3-8
-------
TABLE 3-6. Case 1 and Case 2 Gas Savings, scf Natural Gas
Engine
Date
CASE 1
CASE 2
Rod Seal
Savings While
Idle
Rod Seal Loss
Due to Increase
While Running
Total
Savings
Rod Seal
Increase
While Idle
Rod Seal Loss
Due to Increase
While Running
Blowdown
Valve
Savings
Blowdown
Valve Leak
Loss
Unit Valve
Leak Savings
Pressure
Relief Valve
and Misc.
Comp. Loss
Total
Savings
801
15-Jul
0
0
0
0
0
0
0
0
0
0
16-Jul
0
0
0
0
0
0
0
0
0
0
17-Jul
0
0
0
0
0
0
0
0
0
0
18-Jul
0
0
0
0
0
0
0
0
0
0
19-Jul
355
0
355
-16
0
9,200
0
2,537
0
11,721
20-Jul
302
0
302
-13
0
0
0
2,158
0
2,145
21-Jul
0
0
0
0
0
0
0
0
0
0
22-Jul
0
0
0
0
0
0
0
0
0
0
23-Jul
0
0
0
0
0
0
0
0
0
0
24-Jul
0
0
0
0
0
0
0
0
0
0
25-Jul
0
0
0
0
0
0
0
0
0
0
26-Jul
0
0
0
0
0
0
0
0
0
0
27-Jul
412
0
412
-18
0
9,200
0
2,945
0
12,127
2 8-Jul
322
0
322
-14
0
0
0
2,304
0
2,289
2 9-Jul
0
0
0
0
0
0
0
0
0
0
30-Jul
0
0
0
0
0
0
0
0
0
0
31-Jul
0
0
0
0
0
0
0
0
0
0
1-Aug
0
0
0
0
0
0
0
0
0
0
2-Aug
0
0
0
0
0
0
0
0
0
0
3-Aug
0
0
0
0
0
0
0
0
0
0
4-Aug
0
0
0
0
0
0
0
0
0
0
5-Aug
0
0
0
0
0
0
0
0
0
0
6-Aug
0
0
0
0
0
0
0
0
0
0
TOTAL
1,391
0
1,391
-61
0
18,400
0
9,944
0
28,282
(continued)
3-9
-------
Table 3.6 (continued)
Engine
Date
CASE 1
CASE 2
Rod Seal
Savings While
Idle
Rod Seal Loss
Due to Increase
While Running
Total
Savings
Rod Seal
Increase
While Idle
Rod Seal Loss
Due to Increase
While Running
Blowdown
Valve
Savings
Blowdown
Valve Leak
Loss
Unit Valve
Leak Savings
Pressure
Relief Valve
and Misc.
Comp. Loss
Total
Savings
802
15-Jul
0
0
0
0
0
0
0
0
0
0
16-Jul
0
0
0
0
0
0
0
0
0
0
17-Jul
979
0
979
-43
0
0
0
6,998
0
6,955
18-Jul
979
0
979
-43
0
9,200
0
6,998
0
16,155
19-Jul
979
0
979
-43
0
0
0
6,998
0
6,955
20-Jul
404
0
404
-18
0
0
0
2,887
0
2,869
21-Jul
0
0
0
0
0
0
0
0
0
0
22-Jul
0
0
0
0
0
0
0
0
0
0
23-Jul
0
0
0
0
0
0
0
0
0
0
24-Jul
0
0
0
0
0
0
0
0
0
0
25-Jul
0
0
0
0
0
0
0
0
0
0
26-Jul
0
0
0
0
0
0
0
0
0
0
27-Jul
0
0
0
0
0
0
0
0
0
0
2 8-Jul
0
0
0
0
0
0
0
0
0
0
2 9-Jul
0
0
0
0
0
0
0
0
0
0
30-Jul
0
0
0
0
0
0
0
0
0
0
31-Jul
0
0
0
0
0
0
0
0
0
0
1-Aug
0
0
0
0
0
0
0
0
0
0
2-Aug
0
0
0
0
0
0
0
0
0
0
3-Aug
0
0
0
0
0
0
0
0
0
0
4-Aug
0
0
0
0
0
0
0
0
0
0
5-Aug
0
0
0
0
0
0
0
0
0
0
6-Aug
0
0
0
0
0
0
0
0
0
0
TOTAL
3,342
0
3,342
-147
0
9,200
0
23,882
0
32,935
3-10
-------
As shown in Table 3-4, the total number of standby hours for both engines was 116 hours (Engine
801 total standby hours were 34.1 and Engine 802 total standby hours were 81.9). Assuming an
average rod emission rate of 1.9 scf natural gas, this equates to Case 1 gas savings of 109 scf
natural gas/standby hour for each Test Rod and Case 2 gas savings of 525 scf natural gas/standby
hour for each Test Rod.
3.4 INSTALLATION REQUIREMENTS
Table 3-7 presents the equipment and labor costs for the Control Rod packing material and all
costs related to the Static Pac™ system. These costs were obtained from C. Lee Cook and station
operators.
On a per-rod basis, the capital cost for the Static Pac™ system was $4,088. This is about $2,638
higher than the conventional packing case installed on the Control Rod. The Static Pac™ system
required 48 hours to install on each Test Rod (about 13 hours more than the Control Rod).
Installation of the Static Pac™ was similar to that of a conventional packing case, with the
exception that an automatic actuation system was required. The installation and operating
procedures, as submitted by C. Lee Cook, are provided in Appendix A as a reference. No
deviations from these procedures were observed in the field.
Based on the data presented in Table 3-7, the net incremental cost with the Static Pac™ system is
$3,483.
Table 3-7. Static Pac™ Capital and Installation Costs
Test Rod
Control Rod
Incremental Cost
Increase for a Rod
Equipped with
Static Pac™, $
Description
Cost /
Rod, $
Description
Cost /
Rod, $
Capital Equipment
Packing Case with Static
Pac™
2,200
Conventional Packing Case
1,450
750
Automatic Actuator System
1,638
--
--
1,638
Miscellaneous Materials
250
--
--
250
Installation Labor
Packing Case With Static
Pac™
2,600a
(40 hrs)
Conventional Packing Case
2,275a
(35 hrs)
325
Actuator System
520a
(8 hrs)
--
--
520
Total
$7,208
$3,725
$3,483
a Installation costs of $65 per hour are assumed.
3-11
-------
4.0 DATA QUALITY
4.1 BACKGROUND
Information on data quality is used to characterize the level of uncertainty in measured values and
verification parameters. The process of establishing data quality objectives starts with
determining the desired level of confidence in the primary verification parameters. A primary
parameter for Phase I was the establishment of idle-mode gas savings for the Static Pac™. These
gas savings are used to help quantify the primary Phase II verification parameter the Static Pac™
payback period. The data quality objective that was established for the payback period defines
the quality goals for all measured parameters. It is based on input from gas industry and other
Stakeholder Group members, and allows for an error in payback values of about + 3 to 4 months.
This goal was used to set data quality goals for the following key measured values: rod packing
emissions; valve emissions (unit, blowdown, and pressure relief valves); miscellaneous source
emissions; and natural gas quality measurements. This section identifies these goals and
discusses how they affect the Phase I verification results.
During the Phase I evaluation, field and laboratory measurements were collected in an effort to
quantify uncertainty in the measured values identified above. For example, the accuracy and
precision of the Flow Tube measurement were quantified with frequent calibrations and replicate
samples, and these data were used to quantify uncertainty in the packing emissions rates
presented in Section 3. These calibrations and replicate samples, along with accuracy and
precision data provided by instrument vendors, were used to quantify uncertainty in the key Phase
I verification parameter, natural gas savings. As a practical matter, one limitation on the quality
and representativeness of the measurements collected is their relative infrequency. Although the
level of uncertainty is associated with measurement frequency, it was addressed by repeating all
measurements on two separate occasions. On each occasion, measurements were collected at
least two separate times, and each result represented numerous individual quantifications.
4.2 ROD PACKING EMISSION RATE MEASUREMENTS
The MEM Rangemaster flowmeters originally planned for use on the doghouse vents did not
function properly in the field. As a result, the use of these meters were replaced by manual Flow
Tube measurements. Based on manufacturer supplied performance data for the MEM meters, the
maximum error anticipated was +2 percent of the instrument's full-scale reading. An error of 5
percent would have allowed the achievement of the data quality objectives set for the payback
period and, considering the magnitude of the average emission rates measured at the site, the
MEM meter may have resulted in an error of about 6 percent. Performance data collected on the
Flow Tube suggest that the error associated with the emission rates measured at the site were low,
exceeding the original performance goal for the MEM meters.
Table 4-1 presents Phase I calibration results for the Flow Tube, and shows the accuracy values
developed from these data. The Flow Tube was calibrated with a laminar flow element (LFE),
which itself was calibrated with a NIST-traceable primary standard. The average Flow Tube
accuracy values presented for each run were calculated from the individual measurements in a
run. Individual measurement accuracy values were calculated by determining the differences
between the Flow Tube and LFE flow rates (Flow Tube minus LFE), dividing this value by the
4-1
-------
LFE flow rate, and then multiplying by 100. As the table shows, the average accuracy of the Flow
Tube ranged from -1.54 to -2.73 percent of the value measured by the LFE (overall average of
-2.10 percent). The instrument provided acceptable readings across most of the flow range
represented in Table 4-1, but a relatively consistent negative bias was observed at low flow rates.
Specifically, at flows less than about 0.3 scfin, a negative bias (between -11 and -17 percent) was
observed for all calibration runs. This error applies to the flow readings recorded for the Test
Rod during idle periods which were below the LDL. For these values, the overall average Flow
Tube accuracy was -13.5 percent. This value is used to determine the level of actual uncertainty
in the net gas savings values described in Section 4.3.
Table 4-1. Flow Tube Calibration Results (low flows)
Date
Run
Flow Tube
Flow Tube Methane
LFE Pressure
LFE Methane
Flow Tube
Velocity,
fpm
Flow Rate,
scfm
Drop,
in. H20
Flow Rate, scfm
Accuracy,"
%
6/2/99
1
102
0.2938
0.98
0.3405
238
0.7018
2.00
0.6949
484
1.4398
4.05
1.4072
711
2.1208
6.05
2.1021
905
2.7028
8.00
2.7796
Run Average
-2.46
6/2/99
2
101
0.2969
0.98
0.3405
236
0.7019
2.00
0.6949
486
1.4519
4.05
1.4072
712
2.1299
6.05
2.1021
908
2.7179
8.00
2.7796
Run Average
-1.90
7/2/99
1
113
0.3156
1.02
0.3543
202
0.6983
2.03
0.7052
368
1.4121
4.03
1.3997
528
2.1001
6.02
2.0917
683
2.7666
8.05
2.8033
843
3.4546
10.10
3.5172
Run Average
-2.28
7/2/99
2
103
0.2987
1.04
0.3619
203
0.7187
2.05
0.7136
370
1.4201
3.98
1.3850
535
2.1131
6.01
2.0937
694
2.7809
8.04
2.8075
850
3.4361
10.05
3.5104
Run Average
-2.73
7/23/99
1
109
0.3537
1.11
0.3867
249
0.7457
2.04
0.7107
478
1.3869
4.05
1.4123
733
2.1009
6.03
2.1064
967
2.7561
8.01
2.8132
Run Average
-1.54
7/23/99
2
59
0.3206
1.11
0.3900
219
0.7526
2.02
0.7102
481
1.4600
4.00
1.4077
736
2.1485
5.99
2.1182
978
2.8019
8.04
2.8510
Run Average
-1.68
Overall Average
-2.10
" Rounding error may prevent the reader from calculating the exact run average percentages using the concentration data
presented in the table.
4-2
-------
Precision and/or repeatability were assessed by conducting replicate calibrations. The calibrations
conducted on 6/2/99 represent the only set of calibration replicates where the reference flow rates
(i.e., the LFE flow rate) were precisely duplicated for both runs. In the other calibrations, the
duplication of flow conditions was close, but not exact. Figure 4-1 presents a plot of the
calibration results collected on 6/2/99. The two lines plot the difference between the Flow Tube
flow rates and LFE rates divided by the LFE rates. These values are plotted for each of the five
flow rate conditions examined, so if the Flow Tube values were 100 percent repeatable at all flow
conditions, only one line would be visible. In this case, repeatability is not exact but is acceptable
at all calibration flow conditions. Overall Flow Tube repeatability was calculated for 6/2/99 by:
calculating the average difference between the two Flow Tube rates measured for each of two
runs at the five flow conditions; dividing this value by the average reference concentration across
all flow conditions; and multiplying by 100. This value, calculated to be -0.54 percent, is a
measure of the degree of Flow Tube variability observed relative to the actual or reference flow.
The trends observed in the 6/2/99 data were apparent in plots of all calibration results collected.
-Flow Tube-LFE (Run 1) —¦—Flow Tube-LFE (Run 2)
Figure 4-1. Flow Tube Repeatability (6/2/99)
0.0600 n
.Q
3
H
s
o
E
-0.0800
0.0400
0.0200
0.0000
-0.0200
-0.0400
-0.0600
Flow Condition (1 = lowest flow)
Gas savings for the rod packing are determined as the difference between the packing emission
rates measured on the Test and Control Rods. Thus, the total error in the difference is the sum of
the absolute errors in each measurement. This principle, along with the average accuracy value
of -13.5 percent for Test Rod readings and -2.10 percent for Control Rod readings, was used to
determine potential levels of error in net gas savings. This overall error is presented in Section
4.3.
Finally, the original completeness goal for rod packing emissions measurements required the
completion of 90 percent of hourly measurements throughout Phase I. As discussed in Section
3.1, continuous measurements were not feasible, and an alternate method of manual sampling was
required. The measurements data collected represent 5 days of sampling, and cover the
performance levels immediately after, and several weeks after, the Static Pacs™ were installed.
4-3
-------
4.2.1 Unit Valve, Blowdown Valve, and Pressure Relief Valve
The Test Plan specified using the Hi-Flow device and/or EPA's protocol tent/bag method for
manual testing of the blowdown valve, pressure relief valve, and unit valves. As discussed
earlier, the Center was unable to obtain a license in time to use the Hi-Flow device. Therefore,
measurements were made using other calibrated instruments. In all cases, the data quality
achieved with these alternate methods were higher than the 10 percent accuracy and precision
goals set for the Hi-Flow device. QA results associated with each instrument are described
below. Data quality considerations for the estimated blowdown volume are also discussed.
The pressure relief and unit valve leak rates were measured using the same Flow Tube discussed
earlier. Because flow was not detected for any pressure relief valves, QA and calibration data are
not presented for them. For the unit valve, the Flow Tube calibration data presented in Section
4.2 are applicable to the few low-flow rate measurements collected on this device. In most cases,
flow rates were higher, and a high-flow calibration chart was developed and used after the field
study was completed to convert measured gas velocities into natural gas flow rates. The same
Flow Tube calibration procedures described for the rod packing vent measurements were
followed here, and the calibration data developed at high flows are presented in Table 4-2. A
calibration chart, similar to the Flow Tube calibration chart presented in Section 2 for the rod
packing vent measurements, is shown in Figure 4-2. The Flow Tube accuracy at high-flow
regimes was found to perform as good as or better than the accuracy observed at lower flow
regimes. Figure 4-2 clearly shows that the natural gas flow rate is linearly proportional to the gas
velocity measured with the Flow Tube. The accuracy and precision of the Flow Tube exceeded
the 10 percent goal set with the Hi-Flow device.
Table 4-2. Flow Tube Calibration Results (high flows)
Date
Run
Flow Tube
Flow Tube
LFE Pressure
LFE Methane Flow
Flow Tube
Velocity,
Methane Flow
Drop,
Rate, scfm
Accuracy, %
fpm
Rate, scfm
in. H20
8/12/99
1
120
0.26
0.05
0.32
454
1.36
0.20
1.31
871
2.74
0.40
2.62
1269
4.05
0.60
3.99
1704
5.48
0.80
5.35
2087
6.75
1.00
6.72
Run Average
-1.40
8/12/99
2
140
0.31
0.05
0.33
454
1.35
0.20
1.32
866
2.71
0.40
2.64
1262
4.02
0.60
3.97
1686
5.42
0.80
5.31
2092
6.75
1.00
6.67
Run Average
0.80
Overall Average
-0.30
4-4
-------
Figure 4-2. Flow Tube Calibration at High Flows (8/12/99)
Gas Velocity (fpm)
The Flow Tube was originally planned for use on the blowdown valve as well. However, early
field results suggested that the flow rates from the blowdown valve were very low (i.e., there was
no response), and Flow Tube calibrations suggested performance was poor in this regime.
Therefore, a low-flow rotameter was used to conduct measurements on the blow,-down valve.
The calibration results for this device are presented in Table 4-3. The original accuracy goals for
this measured parameter are also shown for comparison.
Table 4-3. Rotameter Calibration Results
Measurement
Instrument Used
Calibration
Date
Range
Accuracy, %
Precision, %
Goal"
Actual
Goal"
Actual
Rotameter
(Dwyer VB Series)
8/9
0 to 1000
mL/min
10
1.38
10
-0.73
a Represents accuracy and precision goals set for the Hi-Flow device in the Test Plan.
For the miscellaneous components such as flanges and valve stems, it was not possible to
effectively channel the leaking gas to the flow tube. For these types of fugitive sources, soap
screening was used to identify significant leaks and, when flow rate determination was needed,
EPA's protocol tent/bag method was planned for use. Since significant leaks were not found, the
tent/bag method was not applied, and the data quality information is not presented.
4-5
-------
The average accuracy values presented here are used in Section 4.3 to assess how these measured
values may contribute to overall uncertainty in the natural gas savings estimated for Cases 1 and
2.
4.2.2 Gas Composition
Based on average gas compositional data supplied by ANR, the average methane concentration in
the natural gas was determined to be 97.18 percent. The accuracy of these readings was
determined to be 0.12 percent.
4.2.3 Blowdown Volume
Blowdown volume was quantified based on the volume of piping and manifolds in the
compressor system, and is accurate to within the piping specifications (assumed to be 100 percent
accurate). The unit pressure, which was measured at the station by ANR engine monitors, was
used to convert the calculated volume into a volume of natural gas at standard conditions.
Generally, the host site operated at about 700 psig suction pressure. Unfortunately, calibration
records for the pressure monitor are not maintained by ANR, so accuracy estimates for this
measured parameter could not be determined. However, the accuracy of the pressure sensor was
not required because the blowdown volume was calculated based on a typical suction pressure of
700 psig.
4.3 OVERALL UNCERTAINTY IN THE MEASUREMENTS, NET GAS SAVINGS, AND
METHANE EMISSIONS VALUES
Calibrations were conducted by the Center on most of the instruments used in this verification.
These data are summarized in Table 4-4. In a few cases, performance data supplied by either the
instrument vendor or ANR Pipeline were used. These data are also presented in Table 4-4.
Table 4-4. Summary of Instrument Performance Data
Measurement
Instrument Used
Applicable Source
Source of
Performance Data
Accuracy
(%)
Precision
(%)
Flow Tube
Doghouse Vents
The Center
2.10
(-13.5)3
-0.54
Unit Valve Leaks
The Center
-0.30
+ 1.81
Rotameter
Blowdown Valve Leaks
The Center
+ 1.38
-0.73
Gas
Chromatograph
All (convert natural gas
emissions into methane
emissions)
ANR Pipeline
0.12
Not
available
Hydrocarbon
Analyzer
Pressure relief valve and misc.
components
The Center
1.5
0.5
a The value in parentheses represents the accuracy when flows were less than 0.3 scfm. It was used to assess uncertainty in
net gas savings.
4-6
-------
The measurement accuracy values presented above were used to calculate how measurement
error might propagate through the calculation process used to determine net gas savings and
methane emissions for the Static Pac™. Based on these calculations, uncertainty or potential
error in the net gas savings and methane emissions values for Case 1 is estimated to be +2
percent. For Case 2, more individual measurements were collected and a greater opportunity for
error existed. In this case, the overall uncertainty or potential error is estimated to be +4 percent.
It should be noted that the estimated errors above represent uncertainty introduced by the
measurements methods used. They do not include uncertainty or bias that could be introduced
into the results attributable to: differences in the host sites' design or operating characteristics
relative to other sites; the frequency of measurements conducted; or environmental, diurnal,
geographic, or other potential biasing factors. The Center conducted this evaluation over a 3
week period, and collected several separate measurements data sets in an effort to address some
of these potentially biasing factors.
4-7
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5.0 REFERENCES
GRI 1997. Documentation of Existing Rod Packing Technology and Emissions. GRI-97/0393,
Gas Research Institute, Chicago, IL, December 1997.
Harrison, Matthew R., Lisa M. Campbell, Theresa M. Shires, and R. Michael Cowgill 1996.
Methane Emissions from the Natural Gas Industry, Volume 2: Technical Report, EPA-600/R-96-
080b, (NTIS PB97-142939), U.S. Environmental Protection Agency, National Risk Management
Research Laboratory, Research Triangle Park, NC, June 1996.
Hummel, Kirk E., Lisa M. Campbell, and Matthew R. Harrison 1996. Methane Emissions from
the Natural Gas Industry, Volume 8: Equipment Leaks, EPA-600/R-96-080h, (NTIS PB97-
143002), U.S. Environmental Protection Agency, National Risk Management Research
Laboratory, Research Triangle Park, NC, June 1996.
Shires, Theresa M. and Matthew R. Harrison 1996. Methane Emissions from the Natural Gas
Industry, Volume 7: Blow and Purge Activities. EPA-600/R-96-080g, (NTIS PB97-142988),
U.S. Environmental Protection Agency, National Risk Management Research Laboratory,
Research Triangle Park, NC, June 1996.
SRI 1999. Testing and Quality Assurance Plan for the C. Lee Cook Division, Dover Corporation
Static Pac™ System, SRI/USEPA-GHG-QAP-04, Greenhouse Gas Technology Verification
Center, Southern Research Institute, Research Triangle Park, NC, July 1999.
5-1
-------
APPENDIX A
Static Pac™ Operator's Manual
Automatic Control System
A-l
-------
STATIC-PAG - :c-;-r«s=cr Rod Packing S'-tuc-y j co, ' of the Statin-Pac central. Install a
is* fiiting in the ignition ssr-rsand ii.i* from tne engine control ear.sl and
connect tr.e brs-.sh of th« tee to bulx-r.ead raa ¦ 3 of tr.s 5tatic-?ae central 'It
an igmtion-ON co.-sr.and sigr.al is not availsbla, tne ftisl-ON signal car. Uc used
ir.stsaa). Conr.est hul'ifoaad r.s. 2 to pilsr, (operator: of high pressure valva
• CO-"; csriRe=t cish pressure ^as supply ts blacked ir.let pert of valve IPC-'.,
scr.r.eat Stati;-?9!i; 3) ta oppssite porr., pipe third pert ivirit) x.a a safe,
•jnrestristeri vent syatss to atmosphere, Conr;«ct biiiuhesd .r.s. « to ir.dicttar
VJr,-", after indicator has Seen positioned ir. tie&irws LocsiioB. Cswstas &
i; psig filtered Siis?i;' air zq by": 'it-.imc its. S. Installation is coxplate,
3, j?£ SATICM
Ensics/se.-iprsasor is stapled, Supply sir 2nd er.siTie p»r«l Starting Air aftrf
I?,nitisr. {zr fual) co=-?.#tiS signal j are scnn«oied to Static-??.*; control. High
treasur5 gss is to the Iniot of con'trt?- vslve -* h is ^ is pip^d
So Stati-:-r*c{ s) an; vent.
5'jpply air snters throwfii bulkhead ns. 5 tss th* inlet sf valve. 9-'>. If ¦?-' is
nanually latched alssea, air passe® tnre'Jgh 9-' to irXi aiigsc no. 2 ar.c
'3Uli«a
-------
STATIC-PAC - C'-r.-r0—1 to vent the. icatia-Pac(s) ar.rf iridloatcr 1'?>.-•• whtcn
retu-*n$ ts ins D-ack poaiticn, Trie St atlo-Pae (s) are nnw o tsensjigM,
Si-jltar.^usiy, air is flowins flaw cnntrol vn\v>: in the
rej-.rintea direction to slowly fill voi'jne chamber ?.!}-' vnisn is connects*; to
"he pilot of ''3lve -5"' ¦ Valv* is ac'uateci far a *5 «©onn-a eel ay after
-hith valve 3-1 sv.fts to the open position, alltwir.g prassurp. r,o flsw thra'jjh
b-jiaeie no. '1 ta the pilot sf starting air valve, crinking the sngine. The
tise aeiay inserts that the Statin-P-ie; s) are di3cr.si?ed before the cr.gir.e
rails. At t.n« proper tine, cne -rgir.* ccr.trsi panel will aenci a If,^;tlor-CM
>sr F-6.-0N) signal to Star. ia-Pac control bi.'lAa&o no, 1. This signal will
nfiiie engine is running and thrash shuttle valve '5-' --ill keep aigr.sl
t° 9-^&t valve 1 CO-' vendee, keeping -totio-Pacis) on csnprs.ucr cisengnged ,
5tarT4,:"4 sir signal at bull-in can no, 5 will ver.tea after sngir.e has attained
firms steed and valve will rot'jrn ts iha normally cls*«c position,
-"S Pilot 3'-' the starting sir valve, stopping all cranking. Ch#^k
v Cm 7 6 "0-* i.n.yjrea that pilot air is vented from the star tins, air valve
iEEsO .stej.y nn the loss of trsa starting ?ir conir.ar.iJ signs! , Ths er.gir.c is r.nw
run,"ins '-'itS the Static-Pr.cfs) en the ccr.p'isssr tisergsged ,
Whan ;.ne engine control avatar signals a shut down ay venting press-jr* fron
fc»l
-------
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