May 2008Disclaimer
This publication was prepared for the Canadian Association of Petroleum Producers, the Gas Processing Association Canada, the Alberta Department of Energy, the Alberta Energy Resources and Conservation Board, Small Explor ers and Producers Association of Canada and Natural Resources Canada by CETAC-West. While it is believed that the information contained herein is reliable under the conditions and subject to the limitations set out, CETAC-West and the funding organizations do not guarantee its accuracy. The use of this report or any information contained will be at the user’s sole risk, regard less of any fault or negligence of CETAC-West or the sponsors.

Acknowledgements This Fuel Gas Efficiency Best Management Pr actice Series was developed by CETAC WEST with contributions from:

• Accurata Inc.

• Clearstone Engineering Ltd.

• RCL Environmental

• REM Technology Inc.

• Sensor Environmental Services Ltd.

• Sirius Products Inc.

• Sulphur Experts Inc.

• Amine Experts Inc.

• Tartan Engineering

CETAC-WEST is a private sector, not-for-pr ofit corporation with a mandate to encourage advancements in environmental and economic perf ormance in Western Canada. The corporation has formed linkages between technology producers, i ndustry experts, and in dustry associates to facilitate this process. Sinc e 2000, CETAC-WEST has sponsored a high ly successful ecoefficiency program aimed at reducing energy cons umption in the Upstream Oil and Gas Industry.

Head Office # 420, 715 - 5th Ave SW Calgary, Alberta Canada T2P2X6 Tel: (403) 777-9595 Fax: (403) 777-9599 cetac@cetacwest.com

## Table of Contents

1. Applicability and Objectives 1

2. Basic Improvement Strategies 3 2.1 Technology and Equipment 2.2 Efficiency Assessment 2.3 Training and Expertise



## 3. Inspection, Monitoring and Record Keeping 5

4. Rapid Feasibility Assessment 6 4.1 Types of Pneumatic Devices 4.2 Performance of Pneumatic Instrumentation



## 5. Operational Checks, Testing and Adjustments 11 5.1 Field Survey 5.2 Field Measurement 5.3 Data Review 5.4 Economic/Environmental Evaluation 5.5 Implementation



## 6. Appendices 17 Appendix A Types of Pneumatic Devices and Uses Appendix B Instrument Characteristics Appendix C Field Survey Appendix D Flowchart Appendix E Case Study Appendix F References

## Figures Figure 1 Flapper Nozzle Control Loop Figure 2 Wellmark 2001NB Snap Acting Pilot Figure 3 Common Pressure Controller Figure 4 Pressure Control Loop Figure 5 Level Control Loop

## Background

The issue of fuel gas cons umption is increasingly im portant to the oil and gas industry. The development of this Best Management Practice (BMP) Module is sponsored by the Canadian Associati on of Petroleum Producers (CAPP), the Gas Processing Association Canada (GPAC), the Albert a Department of Energy, Small Explorers and Producer s Association of Canada (SEPAC), Natural Resources Canada (NRC) and the Ener gy Resources and Conservation Board (ERCB) to promote the effi cient use of fuel gas in pneumatic instruments used in the upstream oil and gas sector. It is part of a series of 17 modules addressing fuel gas efficiency in a range of devices.

This BMP Module:

• identifies the typical impediments to achieving high levels of operating efficiency with respect to fuel gas consumption,

• presents strategies for achieving cost effective improvements through inspection, maintenance, operating practices and the replacement of underperforming components, and

• identifies technical consi derations and limitations.

The aim is to provide practical guidanc e to operators for achieving fuel gas efficient operation while recognizing t he specific requirements of individual pneumatic instruments and thei r service requirements.

## EFFICIENT USE OF FUEL GAS IN THE UPSTREAM OIL AND GAS INDUSTRY

MODULE 3 of 17: Pneumatic Instruments

FIELD 5

. C

h

e m i ca

l In

j e c ti

o n P

u m

p s

1 .

G

a t h

e r i n g S

y s t e m

s

6 . F i r e d

H

e a t e r s

4

. F l a r i n g

3

. P

n e u m

a t i c I n s t r u m

e n t s

2 .

P

u m

p j a c k

s

7 . E

n g i n e s

1 0

. D

e s i c c a n t D

e h

y d

r a to

r s

8

. C

o m

p r e s s i o n

9

. G

l y c o l D

e h

y d

r a t o r s

1 1 .

F

u e l G

a s M

e a s u r e m

e n t



### SOUR GAS PLANTS 1 7

. A

c i d

G

a s

I n j e c t i o n

1 5

. S

u l p h

u r R

e c o v e r y

1 4

. A

m

i n e

1 3

. R

e f r i g e r a t i o n

1 2 .

F

r a c t i o n a t i o n

5

. C

h

e m i c a l I n j e c t i o n P

u m

p s

6

. F i r e d

H

e a t e r s

4

. F l a r i n g

3

. P

n e u m

a t i c I n s t r u m

e n t s

7 . E

n g i n e s

1 0

. D

e s i c c a n t D

e h

y d

r a t o r s

8

. C

o m

p r e s s i o n

9

. G

l y c o l D

e h

y d

r a t o

r s

1 1 .

F

u e l G

a s M

e a s u r e m

e n t

1 6

. T

a i l G

a s I n c i n e r a t i o n 

### SWEET GAS PLANTS 1 3

. R

e f r i g e r a t i o n

1 2 .

F

r a c t i o n a t i o n

5

. C

h

e m i c a l In

j e c t i o n P

u m

p s

6

. F i r e d

H

e a t e r s

4

. F l a r i n g

3

. P

n e u m

a t i c I n s t r u m

e n t s

7 . E

n g i n e s

1 0

. D

e s i c c a n t D

e h

y d

r a to

r s

8

. Co

m

p r e s s i o n

9

. G

l y c o l D

e h

y d

r a t o

r s

1 1 . F

u e l G

a s M

e a su

r e m

e n t

1 6

. T

a i l G

a s I n c i n e r a t i o nEfficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 1 of 28 

## 1. Applicability and Objectives

Pneumatic instruments of a ll types are used throughout the oil and gas industry to perform the necessary functions which enable the production, processing, transfer and refining of petroleum products . Instrumentation is used to take measurements and control processes typically by sending a signal to a valve to adjust its position based on changes in the process conditions. Controllers can be used to control the process based on pr essure, temperature, flow or liquid level. Because of the simplicity and relia bility of pneumatic instrumentation as well as the lack of available electr icity in many locations, pneumatic instrumentation has become the standard in the industry.

Pneumatic instruments may be powered by compressed air, natural gas or propane. However, the ready availability of pressurized natur al gas has made it the energy of choice for instrumentation. In spite of the cost of natural gas and emissions to the atmosphere, its use as an energy source continues to dominate for the following reasons:

• Pneumatic instrumentation is simple and reliable, making it easy for field operators to adjust and repair.

• Reliable electricity is not availabl e or economical at many locations.

• Electrical instrumentation can be m any times the cost and in some cases does not meet the proce ss control requirements.

• Low Bleed instrumentat ion is now available.

• Retrofit kits are available for high bleed instrumentation still in place.

• Conversion to air at larger facilities still requires pneumatic instrumentation.

• Most operators have considerable ex perience with pneumat ic instruments.

There has long been a misund erstanding in the industry that the amount of gas pneumatic controllers bleed is insignifi cant. Work performed for the United States Environmental Protection Agency ha s shown that the largest source of methane emissions in the industry comes fr om pneumatic instrumentation. Fifty percent of all vented gas and 15 to 20 percent of total emissions in the United States (U.S.) are said to come from pneu matic instrumentation. The production segment accounts for 69 percent of these emissions in the US and it is likely that a similar percentage applies in Canada. Gas storage and transmission account for most of the remainder. In the US , venting from pneumat ic instruments is estimated to be in the order of 61 billion standard cubic feet (Bscf) per year. In Canada the estimate is between 12 and 25 Bscf per year of gas being vented to the atmosphere through pneumatic instrument ation. Assuming a price of CDN$6 per 1000 scf, the value of vented gas is between $75 and $150 m illion dollars per year.Efficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 2 of 28 There are about 100,000 gas wells in Wester n Canada, the majority in remote locations without power. Al though pressurized natural gas is the primary power source for pneumatic controllers, about 30 pe rcent of the wells are sour gas wells which use bottled propane as the energy source to drive the pneumatics. Propane venting, like natural gas, adds to both the cost and environmental impact of operating pneumatic devices. In many cases propane is much more costly than natural gas due to trucking and logistics.

Typical pneumatic instrum ents used in the Canadian oil and gas industry are listed in the Instrument T able (Appendix B) and in general vent between 3 and 50 standard cubic feet per hour (scfh). A si ngle device venting at 30 scfh will use 262,500 ft 3 in a year, more than $1,500 per year in lost reserves (assuming a gas price of CDN$6 per 1000scf) in addition to approximately 97 tonnes of CO 2 equivalent (CO 2 E) emissions. The several hundred thousand pneumatic controllers in operation today, present a significant opportunity to reduce emissions and increase sales of natural gas.

Technology exists today to dramatically re duce this venting and at the same time have a positive economic impact on oil and gas operations. In addition to the large economic benefits there ar e many side benefits including:

• reducing emissions of GHGs,

• reducing odors which reduces landowner complaints,

• increasing worker safety, and

• reducing fire hazards.

This document discusses the different ty pes of pneumatic instrumentation, gas consumption from these devices, and fiel d optimization to improve both the economics and environmental aspects of oper ating pneumatic inst rumentation. The best management practices presented here, both in text and in the form of a flowchart, are practical steps to minimize the amount of vent ing from pneumatic devices.Efficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 3 of 28 

## 2. Basic Improvement Strategy

The critical factors to ensuring a successful long term strategy to optimize fuel gas consumption from field wide oper ations are to educate personnel to recognize opportunities, and to perform fiel d optimization using logical steps. Efficient operation of pneum atic devices requires:

• a database or inventory of pneumatic devices,

• knowledge of the in strumentation, typical field bleed rates and alternatives,

• routine maintenance and r epair of any problems, and

• optimization of existing equipm ent performance by implementing appropriate technology.



### 2.1 Technology and Equipment

When looking at the basic improvements to reduce fuel gas consumption it is imperative that there is understanding of the device, it s application, limitations and the operational conditions that may affe ct its performance. This information provides the basis for an assessment on an individual device. Appendix A provides background on pneumatic devices; types, applications, fuel gas consumption and performance.



### 2.2 Efficiency Assessment In order to optimize the performance of pneumatic instrumentation, it is recommended that the followi ngs steps be implemented.

• Conduct a comprehensive Field Survey

.

• Undertake Field Measurements to establish vent rates.

• Review data to identify opportunities for improvement.

• Evaluate Economic and Environmental options.

• Implement preferred options.

Section 5 provides details on each step and an easy to follow flowchart.Efficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 4 of 28 2.3 Training and Expertise

Pneumatic instruments are not complicated. However, t hey do control important processes which must be understood prior to working on an individual device. The basic assessment of the equipment should be performed by someone with adequate background in instru mentation, or by an ex perienced operator who understands pneumatic instrum ents. Prior to performing large scale field optimization both operational personnel and a local pneumatic instrumentation specialist should be involved.Efficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 5 of 28 

### 3. Inspection, Monitoring and Record Keeping

Operators should record the pneumatic instruments testi ng and improvement program. Proper record k eeping should assist in ens uring that sub-optimal instrumentation and devices are identified and that appropriate follow-up actions are implemented. This information will also assist in establishing the checking/testing frequency, to achieve cost-effective fuel gas efficiency improvements.

Although each company will define its record keeping system, consideration should be given to recording and re taining the following information:

• data sheets for each type of instrument in service,

• expected fuel gas consumption by device or system,

• records of changes/upgrades that have been performed,

• test results, and

• the economic analysis performed on hi gh bleed instruments, where they have been adjusted/modifi ed on economic grounds. Appendix B provides the ex pected fuel gas consumpti on for the most common instruments and devices that are in us e in the upstream oil and gas (UOG) industry.Efficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 6 of 28 

## 4. Rapid Feasibility Assessment

4.1 Types of Pneumatic Devices

Pneumatic devices can be divided into th ree principle categories: Continuous Bleed, Intermittent Bleed, and No-Bleed. These categories are important when looking at the potential oppor tunity for optimizing your processes in terms of reducing gas venting.

The design of the instrument ation is a major factor in how much the device will vent or bleed. Both continuous bleed and intermittent bl eed devices can be either high bleeders or low bleeders. In general terms high bleed devices have been categorized as those that bleed more t han 6 scfh. This bleed rate does not include vent gas from any ac tuators. The instrument table in Appe ndix B outlines the devices that are throttling (continuous bleed) and snap acting (intermittent bleed) as well as manufactured specif ied bleed rates and where available field measured bleed rates. It is important to be aware that not all manufacturers use the same standards to measure bleed rates in the laboratory and typically results in field applications will be higher.

Continuous Bleed Devices or Throttling Devices

These include controllers, transducers and positioners. These devices are used to control flow, pressure, temperatur e and liquid level. Continuous bleed instrumentation is necessary for propor tional control of the process, and is suitable where a steady stat e environment is desired.

Throttling devices continuously bleed bec ause the design requires a constant supply and venting of gas in or der for the controller to func tion. This bleed rate is steady when the process is steady and will change when the process changes. In addition to the continuous bleed of t he controller, additional venting occurs when the actuator strokes.

Figure 1 demonstrates how a continuous bleed device known as a “flappernozzle” arrangement functions. The flap per-nozzle designed pr essure controller (item e) gets its constant feed of supply gas from a pressure regulator (item f). This gas is used to operate the controller. For the controller to function properly it requires a constant source of supply pressure. The industry standard is either 20 or 35 psi. The controller is connected to the pipeline (item b) and the control valve (item c). The pipeline connection is where the measuring takes place. A measuring device, in this case a bourdon tube (item h), is attached to a flapper assembly (item i). As pressure increases or decreases the, bourdon tube reacts by moving the flapper assembly either closer or further away in relation to a fixed nozzle assembly (item k). When the pre ssure increases the bourdon tube will move the flapper closer to the fixed nozzl e assembly creating a restriction of gas flow coming from the nozzle. Back pr essure created in the nozzle will beEfficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 7 of 28 transmitted to a relay device through the outlet (item j), opening a valve within that device, allowing output pressure to be diverted to the control valve. The valve opens according to t he amount of output pressure transmitted. This allows pipeline pressure to decrease back to t he desired set point predetermined inside the controller, bringing balance to the process loop (item a).



### Figure 1 Flapper Nozzle Control Loop

Intermittent Bleed or Snap Acting Devices

These devices bleed only when the process requires a change. These devices are typically used for level control, or emergency shut down (ESD) operations. When no action is required no gas is used. When a situation occurs requiring a valve to operate this type of device reac ts by sending a full output signal to the valve. Intermittent Bleed and snap acting de vices are “all or not hing” controllers, that is, they are either on or off, no proportionality.Efficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 8 of 28 Refer to Figure 2 as an example of a sn ap acting device. When no action is required the supply valve is seated against the suppl y port prohibiting the movement of instrument gas, thus creating a no bleed situation. As level rises in the tank the flapper bar also rises. When the flapper bar rises it lifts the exhaust valve, pushing the supply valve upward. This action results in the closing of the exhaust port and the opening of the supp ly port, allowing gas to flow freely from the supply port through the output port to the control valve. At this time no gas has been vented to the atmosphere. With the liquid in the tank now flowing through the control valve, the level decreases. A decrease in level will eventually lower the flapper bar causing the exhaust valve to lower, allowing the supply valve to reseat the supply port, prohibiting the flow of supply gas. This action will also re sult in the opening of the exhaust port allowing the gas that was used to open the control valve to escape or bleed to atmospher e, eventually closing the valve and completing the cycle.

No Bleed or Self Contained Devices

These devices include regulators, and most switches. These will not be discussed as they do not v ent to the atmosphere.



### 4.2 Performance of Pneumatic Instrumentation

The amount an individ ual instrument vents is dependent on several factors, some of which we have control over after the instrument is purchased and some of which we do not. The factors affecting bleed rates of individual instruments are listed below in order of importance:

Instrument Design

The design of any instrument dictates how the device will bleed (Intermittent or Continuous) and how much it will bleed. As discussed above, instruments are classified as either high bleed or lo w bleed devices. High bleed, meaning they bleed at over 6 scfh and in some cases over 100 scfh. The design can be altered using a low bleed retrofit kit that is adaptable to many instruments, in effect changing the design and lowering the bleed rate. These low bleed retrofit kits are available from several manufac turers. Field results have shown that between 10 and 60 scfh is the typical saving after implementing a replacement 

### Figure 2 Wellmark 2001NB Snap Acting PilotEfficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 9 of 28 low bleed device or retrofitting an existi ng device. In general these devices reduce gas consumption from 65 to 95 percent.

Appendix E is a case study describing two applications of low bleed retrofits. This case study was chosen as it contai ns both a typical controller and one not very typical which has a very low bleed rate for its design. Both have very good gas reductions but the lower bleed dev ice would have a slower payback.

Device Condition

Device condition is a very important factor in keeping the bleed rates low. If the instrument is not maintained the parts will become dirty and worn. Dirt and particles in the moving parts will cause t he device to operate out of its designed parameters and typically result in exce ssive venting. Field results have demonstrated that instrumentat ion in poor condition bleed 5 to 10 scfh more than they should. Typical problems include:

• worn seals, gaskets, and di aphragms resulting in leaks,

• nozzle corrosion or wear from poor quality gas leading to increased flow, and

• loose control tube fittings.

Gas Supply Pressure

The supply gas pressure directly affects the bleed rate of instrumentation. The supply pressure should be either 20 pounds per square inch (psi) (for 3-15 psi signal) or 35 psi (for 6- 30 psi signal) depending on t he instrument design. However it is common to see pressures si gnificantly higher t han the design of the instrument resulting in excess gas being vented through the device. The regulator must be set to the proper suppl y pressure. In some cases the process may have changed significantly and where once a 35 psi signal 6-30 output was needed for proper control, a 20 psi signal 3-15 psi output can now achieve the same result. This will have a significant effect on venting rates.

Controller Tuning

Controllers out of tune are more active, resulting in non-st eady state operation, causing higher bleed rates from both t he controller and the actuator. Tuning controllers on a periodic basis will maintain optimal conditions and reduce emissions.Efficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 10 of 28 Controller Features

The number of internal controls such as proportional band and reset contribute to the overall bleed rate of a controller. The common pressure controller shown in Figure 3 has several adjustments. Depending on the application these internal controls may play a significant role in the bleed rate of the controller. In many applications the reset valve can be removed resulting in less bleeding while still permitting proper control.

Age of Instruments

The age of the instrument can be a factor in vent rates although not as important as condition. Worn parts are typically a sign of age which may increase venting; however, if the device has been properly maintained and tuned then age have less effect on emission rates. 

### Figure 3 Common Pressure ControllerEfficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 11 of 28 

## 5. Operational Checks, Testing and Adjustments

In order to optimize the performance of pneumatic instrumentation, it is recommended that a program including t he followings steps be implemented:

• Conduct a comprehensive field survey

.

• Undertake field measurements to establish vent rates.

• Data review to identify opportunities for improvement.

• Perform economic/environmental evaluation of options.

• Implementation of preferred options.



### 5.1 Field Survey

Before starting a field survey a rough ca lculation can be made to determine the field wide opportunity for fuel gas sa vings. An approximation of the gas consumption can be obtained by taki ng the number of control loops and multiplying it by 60 scfh per control loop. Using this information as a rough guide gives a sense of the opportunity av ailable for reducing emissions.

To determine what the opportunity in any fi eld or operation may be, the first step is to understand what instrumentation is cu rrently in place. The most efficient way to do this is to assign a person fam iliar with the field and instrumentation to complete a table similar to that below. The table should allo w additional room for notes as shown in Appendix C (Field Su rvey). Keeping the table short and concise allows the operator to be efficient during the field survey process. The task should be focused on getting all the co rrect information as efficiently as possible.

The field survey should be restricted to the following pneumatic instrument types: pressure, temperature, level, different ial pressure controllers, transducers, positioners and transmitters.

A quick check to ensure all field data has been collected prior to leaving a location is to count the pneumatic oper ated valves and compare it with the number of control devices; they should be the same.Efficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 12 of 28

Location

LSD Facility Description Manufacturer Model Output Range Supply Pressure Throttle or Snap Condition Gas Type Retrofit

Location LSD - This is the Land Survey Description.

Facility Description - Type of facility: well site, metering station, plant, separator, etc.

Manufacturer - The manufacturer of the instrument should be on the identification plate.

Model - This is also located on the identification plate.

Output Range - This can also be found on the identification plate.

Supply Pressure - If there is a gauge downstream of the regulator read the supply pressure here, otherwise it can be taken from the controller. Many times the controller gauges are inaccurate; however it may be the only option. Ensure the units (kPa or psi) are recorded.

Throttle or Snap Acting - This is important for le vel control only and indicates the design style of the contro ller. This may be indicated on the pilot or relay with an “S” for snap or “T” for throttle. The indication may also be located on the identification plate.

Condition - The condition of the controller shoul d be indicated by either good or poor.

• Good - clean, no visible signs of wear and tear, gauges operating properly, no irregular sound or feel due to excessive venting of gas.

• Poor - any signs of wear and tear, dirt y, fluid in controller, louder than normal venting, venting can be felt with fingers and is clearly high, door gasket in poor condition, non functioni ng gauges, visible corrosion around nozzle/pilot device.

Gas Type - This will typically be either fuel gas, propane, or air.Efficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 13 of 28 Retrofit - Has the device already been retrofi tted with a low bleed kit? The retrofit may be located on the tubing between the inst rument and the valve or directly inside the controller. Some trai ning will be requir ed to recognize these devices.



### 5.2 Field Measurements

The most accurate information for qua ntifying bleed rates from pneumatic instruments comes from field measurem ents, but this data is not always available. The Instrument Table in A ppendix B outlines the field data available for many instruments. If there is no field data for your particular instrument, and you have a significant number of these devices, then you should perform field measurements to obtain accurate data. Statistical methods can be applied to ensure that a representative sample is taken.

Different field measurement techniques have been used to q uantify the amount of vent gas coming from pneumatic instru mentation and some are more accurate than others. Because of the relatively low emission rates and pressures from individual instruments it is important to ensure t hat proper methodology is followed and accurate instruments are used when gathering data from these devices. When dealing with low volumes a small mistak e can lead to a large error in measurement.

Vent gas from controllers does not nece ssarily leave the controller through the vent line. In many cases the contro ller will be leaking gas around the door or through fittings attached to the controller bo dy. Not understanding this may lead to erroneous results when me asuring vent gas. To ensure that all of the gas is vented through the vent line w hen measuring vent rates, the instrument needs to be bagged. A plastic bag encloses the inst rument and is taped tightly using duct tape to force any fugitive emissions thro ugh the vent line. This ensures an accurate measure of the total venting from the controller.

An accurate meter needs to be selected that measures very low flow at near atmospheric pressure. The meter should be attached to the vent line and the fittings “snooped” to ensure no leaks are present. The total flow should be measured over as long a time as practical (at least one hour) to ensure accuracy of the data. A longer time will give a more representative m easure of any flow rate changes that may occur as a result of process variations.

The data should then be converted to standard conditions of pressure and temperature and presented in terms of scfh.Efficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 14 of 28 

### 5.3 Data Review

After the survey is complete the data needs to be reviewed to assess the opportunity for reducing emissions. By comparing the collected field data with the Instrument Table in Appendix B, you can determine how many high bleed devices are in the field. The Instrument Table prov ides bleed rates for these devices based on both manufacturer specif ications and field data gathered from various sources. Experience suggests that manufacturer bleed rates are understated so field measurem ent data should be used when possible. If there is no field data available, field measurements shoul d be performed on your instruments; however, it will be impractica l to physically measure all bleed rates from all instruments. Focu s should be applied to the instruments of which there are significant numbers in the field.

To begin the assessment of the field data refer to the flowchart in Appendix D. The first step in the flowchart is to det ermine the feasibility of converting all instruments to compressed air. The electr ical power source for the instrument air must also be reliable as in strument air is required c ontinuously. Conversion to instrument air is most viable when a fa cility wide change is already planned. A second benefit is the extension of life of the instrumentat ion because, unlike natural gas, no by products are present in air, which can harm the instrument. No effort in this paper has been made to specify t he economic feasibility of converting to instrument air bec ause each facility is different.

Knowing if an instrument is high or low bleed is the mo st relevant variable in assessing the opportunity for savings a nd the best return on investment. Low bleed devices in instrument air packages are also beneficial as maintenance costs can be reduced by reducing air cons umption. If a field has already been converted to low bleed devices then t uning, and maintaini ng instruments will provide continuing benefits.

By referencing the flowchart in Appendix C along with the field data a complete assessment of each device can be made.



### 5.4 Economic/Environmental Evaluation

After reviewing the field survey data, the opportunities for gas savings should be understood, and whether additional field measurements are required. The devices which need to be replaced, retrof itted or repaired should be listed.

The primary driver is almost always economics. Using fi eld measurements where possible, calculate the reduction in gas consumption based on either replacement to a low bleed device or retr ofit with a low blee d conversion kit. Field measurements should be performed if measured data is not available.Efficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 15 of 28 Alternatively if you use manufacturers ’ specifications you will likely be conservative with any savings.

To calculate the amount of gas saved:

Replacement with low bleed - Use the field data bleed rate in scfh from the existing device minus the field data bleed rate in scfh from the new low bleed device.

S = [(scfh) old – (scfh) new ] x 8,760hr/yr x P/1000.

S = Savings in Canadian dollars for each year after installing the new device. Savings do not include the cost of replacement equipment or the additional savings from potential carbon credits.

[(scfh) old = field data bleed rate of existing device in standard cubic feet per hour.

(scfh) new = field data bleed rate of repl acement low bleed device in standard cubic feet per hour.

P = price of gas in Canadian dolla rs per thousand standard cubic feet.

Retrofit with low bleed kit - use the field data ble ed rate in scfh from the existing device multiplied by the perc ent reduction applicable to the retrofit package of choice.

S = [(scfh) old x R percent ] x 8,760hr/yr x P/1000.

S = Savings in Canadian dollars for eac h year after retrofitting the old device. Savings do not include the cost of retrofit or t he additional savings from potential carbon credits.

[(scfh) old = field data bleed rate of existing device in standard cubic feet per hour.

P ercent = reduction in gas consumption applic able to the retrofit system you have chosen. For SER use 65% reduction (R=0.65) and for the Mizer use 95% reduction (R=0.95).

P = price of gas in Canadian dolla rs per thousand standard cubic feet.

When performing these calculations you must include the field time to retrofit or replace the old device, typically about two hours, in addition to the cost of the retrofit kit or replacement device. When replacing a device there is also an environmental impact from the disposal of the older inst rument. In general if a retrofit can be performed it is a more ec onomical and environm entally beneficial way to cut emissions.Efficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 16 of 28 Field experience has demonstrated that over 80 percent of all high bleed controllers can be economic ally retrofitted to become low bleed, or replaced with low bleed controllers. In general payouts are between 3 and 9 m onths based on gas savings. Annual savings by retrof itting or converting a high bleed device, bleeding at 35 scfh (306 mil lion standard cubic feet per year), to a low bleed device are in the order of 250 mscfy or $1,500 in addition to 94 tonnes CO 2 E. If CO 2 credits are applied the payouts may drop by 50%.

Maintenance and Repair - During the Field Stud y and Data Review many controllers will be found to require maintenance or repa ir. Prior to proceeding, the review should be completed to dete rmine which instrument s will need to be replaced or retrofitted. Du e to the various types of instruments in the field it is difficult to provide a formula to a ssess the benefits of repairing a particular instrument. However, there is plenty of evidence to support the economics of a solid maintenance program. Field test s by various operators suggest that paybacks of less than 9 months are typical.



### 5.5 Implementation

The implementation of the pl an is the most important part. Once the economic and technical justifications are comp lete and management has approved the project, implementation c an start. Managing the im plementation will be subject to individual operations and availability of skilled people to perform the tasks.Efficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 17 of 28 

### Figure 4 Pressure Control Loop 

### Appendix A Types of Pneumatic Devices and Uses

A typical process control loop consists of a control device (i.e. pressure, flow, level, or temperature contro ller), a controlled device (i.e. valve, choke, louver, or pump), and a pressure regulator, which s upplies power to the control device, which in turn operates the controll ed device. Pneumatic devices include controllers, switches, transducers, pos itioners, and transmitters. A brief description and application is outlined for each below:

Controllers

These devices typically have a built in sensing device which measures the process variable. This allows the contro ller to transmit a pneumatic signal to the final controlled device bas ed on a predetermined set poin t. It is the difference between this pneumatic signal and the set point that determines how much the final device changes, such as a valve op ening or closing. Controller types include pressure, differential pressure, temperature, and level control devices.

Pressure Controller

These devices are used to control proce ss pressure. For ex ample in Figure 4 (Pressure Control Loop) below the cont roller and control valve are used to maintain the pressure in the pipeline based on a desired “set point” or process parameter. The pressure controller uses the supply gas from the regulator as its en ergy source for operation. The controller senses the pressure in the pipe line, and compares this pressure with the “set point”. The controller then sends a pressure signal to the actuator of the control valve causing the valve to open or close. This results in a change in process conditions to bring the actual pressure closer to the desired pressure or “set point”. In this process the valve is typically never fully open or closed. This type of process control is called proportional cont rol and is achieved with a “throttling” controller.Efficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 18 of 28 Differential Pressure Controller

A differential pressure controller operates in a similar fashion to the pressure controller. The differential pressure cont roller senses pressure from two points, typically across an orifice or nozzle. Th is measurement provides the information the controller needs to adjust a valve in order to maintain the set point. Typically differential pressure controllers are indi rectly measuring and controlling flow in a process.

Temperature Controller

A temperature controller is used to c ontrol a process based on the difference between the “set point” and t he process temperature.

Level Controller

These devices are typically used to control the level in a tank. For example Figure 5 (Level Control Loop) below depicts a process where the tank level will fluctuate and the level controller will maintain a desired “set point” or tank level. The level controller has a float which rises with the liquid level in the tank. Once it rises to a certain limit the controller is tripped and the controller sends a signal for the valve to open. Fluid then leaves the tank until the level lowers to a certain level again tripping the controller. At this point the controller again sends a signal to close the valve.

Transducers

These devices are used to convert an electric signal, usually 4 to 20 mA to a pneumatic signal either 3 to 15 psi or 6 to 30 psi. In general t he application is to allow a feedback from an electronic SC ADA system to operate a pneumatic control valve.

Positioners

Used on some control valves to establis h a certain amount of travel on the valve based on the output signal of the controlle r. Typically positioners are used on larger actuators to get more accurate c ontrol and a quicker response. Bleeding occurs at the positioner in addition to the controller. 

### Figure 5 Level Control Loo pEfficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 19 of 28 Switches

These devices are typically used as a safe ty device to protec t the process during upsets, or if control problems occur. T hese devices typically open or close based on level, pressure or temperature.

Transmitters

These are used to transmit pneumatic sign als to a central control point but with the advancement of electronic technolog ies pneumatic transmitters have nearly all been replaced with no-bleed electronic transmitters.Efficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 20 of 28 

### Appendix B Instrument Characteristics

Controller Model Signal Pressure (psi) Manufacturer Data (scfh) Field Data (scfh) Number in Field Throttling or snap Retrofit choices Low Bleed Alternatives

PRESSURE CONTROLLERS
Ametek Series 40 20 6 N/A low throttling
35 6 N/A low throttling
Bristol Babcock Series 5453-Model 10F 20 3 20 - 30 low throttling SER

35 3 20 - 30 low throttling SER

Bristol Babcock Series 5455 Model 624-III 20 2 20 - 30 low throttling SER

35 3 20 - 30 low throttling SER

Bristol Babcock Series 502 A/D (recording controller) 20 <6 N/A low throttling SER

35 <6 N/A low throttling SER
Fisher 4100 Series (large orfice) 20 50 47 low throttling Replace 4195
35 50 54 low throttling Replace 4195
Fisher 4150 and 4160 20 10-35 11 - 35 high throttling SER/Mizer 4195
35 10-42 24 - 65 high throttling SER/Mizer 4195
Fisher 4194 (differential pressure) 20 3.5 12 - 14 moderate throttling SER
35 5 13-18 moderate throttling SER
Fisher 4195 20 3.5 13-18 moderate throttling SER
35 5 12-115 moderate throttling SER
Foxboro 43AP 20 18 N/A moderate throttling SER 4195
35 18 N/A moderate throttling SER 4195
ITT Barton 338 20 6 20 - 30 moderate throttling SER
35 6 20 - 30 moderate throttling SER
ITT Barton 335P 20 6 18 - 30 low throttling SER 4194
35 6 20 - 30 low throttling SER 4194
Natco CT 20 35 N/A low throttling Mizer
35 35 N/A low throttling Mizer

TRANSDUCERS
Bristol Babcock Series 9110-00A 20 0.42 N/A

35 0.42 N/A
Fisher 546 20 15 - 40 high throttling SER 646
35 30 35 - 60 high throttling SER 646

Fisher 646 20 <1 N/A

35 <1 N/A

Fisher 846 20 <1 N/A

35 <1 N/A

LEVEL CONTROLLERS

Fisher 2900 20 23 22-51 moderate throttling LBC/2901 2001NB/1001A
20 23 18-127 moderate snap LBC/2902 2001NB/1001A

Fisher 2900 (Continued) 35 23 28-51 moderate throttling LBC/2903 2001NB/1001A
35 23 27-153 moderate snap LBC/2904 2001NB/1001A
Fisher 2500 Series 20 42 N/A moderate throttling SER

LEVEL CONTROLLERS (Continued)
35 42 44-72 moderate throttling SEREfficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 21 of 28 Controller Model Signal Pressure (psi) Manufacturer Data (scfh) Field Data (scfh) Number in Field Throttling or snap Retrofit choices Low Bleed Alternatives

Fisher 2660 Series 20 1 N/A moderate

35 1 N/A moderate

Fisher 2100 Series 20 <1 N/A low

35 <1 N/A low

Fisher 2680 20 <1 N/A moderate

35 <1 N/A moderate

Fisher L2

Invalco CT Series 20 N/A low throttling Mizer
35 40 34-88 low throttling Mizer

Norriseal 1001 20 N/A N/A moderate 1001A/2001NB

35 N/A N/A moderate 1001A/2001NB
Norriseal 1001 (A) 20 0.007 N/A high throttling
20 0.2 N/A high snap
35 0.007 N/A high throttling
35 0.2 N/A high snap
Wellmark 2001 20 0.007 N/A low throttling
20 0.2 N/A low snap
35 0.007 N/A low throttling
35 0.2 N/A low snap

POSITIONERS
Fisher 3582 20 14 22 high throttling
35 18 24 high throttling

Fisher 3661 20 8.8 N/A m oderate throttling
35 12.1 N/A moderate throttling
Fisher 3590 (electro-pneumatic ) 20 24 N/A high throttling
35 36 N/A high throttling
Fisher 3582i (electro-pneumatic) 20 17.2 N/A moderate throttling
35 24 N/A moderate throttling
Fisher 3620J (electro-pneumatic) 20 18.2 N/A moderate throttling
35 35 N/A moderate throttling
Fisher 3660 20 6 N/A moderate throttling
35 8 N/A moderate throttling
Fisher Fieldvue Digital 20 14 N/A moderate throttling
35 49 N/A moderate throttling
Masoneilan 4600B Series 20 N/A low throttling
35 18-30 N/A low throttling
Masoneilan 4700B Series 20 N/A low throttling
35 18-30 N/A low throttling
Masoneilan SVI Digital 20 <1 N/A low throttling
Masoneilan SVI Digital (Continued) 35 <1 N/A low throttling
Masoneilan 7400 Series 20 24-50 N/A low throttling
35 24-50 N/A low throttling

POSITIONERS (Continued)
Moore Products – Model 750P 20 N/A moderate throttling

Controller Model Signal Pressure (psi) Manufacturer Data (scfh) Field Data (scfh) Number in Field Throttling or snap Retrofit choices Low Bleed AlternativesEfficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 22 of 28 Moore Products – Model 750P 35 42 N/A moderate throttling
Moore Products 73N-B PtoP 20 36 N/A low throttling
35 N/A low throttling
PMV D5 Digital 20 <1 N/A low throttling
35 <1 N/A low throttling
Sampson 3780 Digital 20 <1 N/A low throttling
35 <1 N/A low throttling

VRC Model VP700 PtoP 20 <1 N/A low

35 <1 N/A lowEfficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 23 of 28Appendix CField SurveyNotes:RetrofitGasTypeConditionThrottleor SnapSupplyPressureOutputRangeModelManufacturerFacilityDescriptionLocationLSDEfficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 24 of 28 

### Appendix D Pneumatic Instruments Optimization FlowchartEfficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 25 of 28 

### Appendix E

Case Study

Setting

Compressor Station - D ehydration/Compression

Initiated

September 2004

Situation

The client, an oil and gas produc er, wished to reduce its greenhouse gas emissions as part of its co rporate environmental stewar dship objectives and to realize fuel gas cost savings. It was dec ided that a low-bleed retrofit kit for minimizing methane emissions from cons tant venting pneumatic controllers would be implemented.

Low-bleed technology was installed on two pressure controllers. One controller was located in the TEG dehydration ski d and the other was located in the compressor skid. Initial readings on the cont rollers indicated a vent rate of 10 scf per hour for the dehydration location and 47 scf per hour for the compressor location, giving a combined venting rate of 55 scf per hour from these pneumatic devices.

Solution

The low bleed technology was in stalled in Septem ber 2004. The installation took approximately 4 hours with no loss of producti on for the field. The installation allowed for full valve stroke. Vent rates from the controllers after this procedure were as follows:

• dehydration location 3 scfh, and

• compressor location 12 scfh.

Conclusion

The combined net reduction in methane em issions to the atmosphere was 40 scfh or 73%. In addition, the client was able to prevent 130 tonnes per year CO 2 equivalent combined from being vented to the atmosphere unnecessarily. Payout of the units is achieved in 12 months using $5 per mcf gas.Efficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 26 of 28 Economics

Consumption 1,368 scf/day Savings (73%) 960 scf/day Price of gas $5 Cdn/mcf SER Cost $ 1,770 (885/ea x 2) Annual Savings $ 1,752 Payout 12 months

Environmental Benefits

Methane Reduction* 73% Methane Volume Reduction* 350 mcf/year CO 2 Equivalent Reduction* 130 tonnes/year

*All figures refer to net reduction in emissions to the atmosphere.Efficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 27 of 28Efficient Use of Fuel Gas Pneumatic Instruments Rev Date 27/05/2008 Module 3 of 17 Page 28 of 28 

### Appendix F

References

1. Estimate of Methane Emissions From the US Natural Gas Industry, David Kirchgessner, Robert Lott, Michael Co wgill, Matthew Harrison, Theresa Shires

2. Lessons Learned from Natural Gas ST AR Partners: Options for Reducing Methane Emissions from Pneumatic Devi ces in the Natural Gas Industry, United States Environmental Protection Agency, , July 2003

3. Methane Emissions from the Natura l Gas Industry, Volume 12 Pneumatic Devices, Theresa M. Shires , Matthew R. Harrison, 1996

4. Technology demonstration Report “Sirius Emission Reducer”, CETACWest, Clearstone Engineering, 2005

5. Success Points to Global Opportuni ties to Cut Methane Emissions, US Natural Gas STAR Program, Fernandez, R. Lieberman, and Robinson, D. Oil and Gas Journal, July 12, 2004.

6. www.epa.gov/gasstar/ Lessons Learned, Converti ng Gas Pneumatics to Instrument Air, Options for Reduci ng Methane Emissions from Pneumatic Devices in the Natural Gas Industry, Convert Pneumatics to Mechanical Controls.