Replacing High-Bleed Pneumatic Devices

1. Replacing High-Bleed Pneumatic Devices Lessons Learned from Natural Gas STAR Small and Medium Sized Producer Technology Transfer Workshop Bill Barrett Corporation, Evergreen Resources Inc, Southern Gas Association and EPA’s Natural Gas STAR Program June 29, 2004

2. Pneumatic Devices: Agenda Methane Losses Methane Recovery Is Recovery Profitable? Industry Experience Discussion Questions

3. What is the Problem? Pneumatic devices are major source of methane emissions from the natural gas industry Pneumatic devices used throughout the natural gas industry Over 250,000 in production sector ~ 13,000 in processing sector 90,000 to 130,000 in transmission sector By design, most pneumatic devices vent (bleed) gas to the atmosphere. Gas bleed is part of the mechanism that translates process changes (pressure, level, flow, and temperature) to adjustment in valve position. Controllers are defined as "high-bleed" if they bleed more than 6 scf per hour. This hourly bleed rate equates to greater than 50 Mcf/yr for each device. Typically, high-bleed devices have average bleed rates of 140 Mcf/yr - this is as much gas as is used by the average household on an annual basis. Some Partners have reported devices with bleed rates of 1,100 Mcf/yr. Low-bleed devices vent an average of 8-12 Mcf/yr. Note that manufacturers’ definitions of low-bleed devices vary (may use different units, etc.). Be sure to check the specifications to see if a device is truly low-bleed. Some process conditions require the speed and precision of high-bleed controllers. Most process needs can be satisfied by low-bleed devices. By design, most pneumatic devices vent (bleed) gas to the atmosphere. Gas bleed is part of the mechanism that translates process changes (pressure, level, flow, and temperature) to adjustment in valve position. Controllers are defined as "high-bleed" if they bleed more than 6 scf per hour. This hourly bleed rate equates to greater than 50 Mcf/yr for each device. Typically, high-bleed devices have average bleed rates of 140 Mcf/yr - this is as much gas as is used by the average household on an annual basis. Some Partners have reported devices with bleed rates of 1,100 Mcf/yr. Low-bleed devices vent an average of 8-12 Mcf/yr. Note that manufacturers’ definitions of low-bleed devices vary (may use different units, etc.). Be sure to check the specifications to see if a device is truly low-bleed. Some process conditions require the speed and precision of high-bleed controllers. Most process needs can be satisfied by low-bleed devices.

4. Location of Pneumatic Devices at Production Sites Pneumatic devices are found in several places at a typical production site. There are normally several automatic shut-off valves to isolate individual wells, trunk lines, and compressor suction and discharge manifolds. Wellhead gas often passes through a liquid knock-out vessel to separate water and gas liquids from production gas. These typically have level controllers to transfer those liquids to a storage tank. Dehydration units are automatically controlled with several pneumatic controllers: Level controllers on the TEG-Gas contactor, in a flash-tank separator (where installed) and in the TEG reboiler; Fuel gas burned in the TEG reboiler is often controlled with a temperature controller; The TEG circulation rate is flow controlled; and Gas vented off the FTS and reboiler/regenerator is normally pressure controlled. Where compressors are installed, there are normally many controllers: Suction and discharge pressures; Bypass flow; Fuel gas. Pneumatic devices are found in several places at a typical production site. There are normally several automatic shut-off valves to isolate individual wells, trunk lines, and compressor suction and discharge manifolds. Wellhead gas often passes through a liquid knock-out vessel to separate water and gas liquids from production gas. These typically have level controllers to transfer those liquids to a storage tank. Dehydration units are automatically controlled with several pneumatic controllers: Level controllers on the TEG-Gas contactor, in a flash-tank separator (where installed) and in the TEG reboiler; Fuel gas burned in the TEG reboiler is often controlled with a temperature controller; The TEG circulation rate is flow controlled; and Gas vented off the FTS and reboiler/regenerator is normally pressure controlled. Where compressors are installed, there are normally many controllers: Suction and discharge pressures; Bypass flow; Fuel gas.

5. Methane Emissions As part of normal operations, pneumatic devices release natural gas to atmosphere High-bleed devices bleed in excess of 6 cf/hr Equates to >50 Mcf/yr Typical high-bleed pneumatic devices bleed an average of 140 Mcf/yr Actual bleed rate is largely dependent on device’s design The major sources of methane loss from natural gas facilities include the following:1 Compressor seals; Valve/piping connectors; Vents; and Pneumatic controllers. Of all of these sources, pneumatic devices contribute the largest methane loss: Most natural gas industry sites use natural gas; Refineries, chemical plants, and some gas processing plants use compressed air; There are over 250,000 such devices in the production sector; There are between 90,000 and 130,000 in the transmission sector. The major sources of methane loss from natural gas facilities include the following:1 Compressor seals; Valve/piping connectors; Vents; and Pneumatic controllers. Of all of these sources, pneumatic devices contribute the largest methane loss: Most natural gas industry sites use natural gas; Refineries, chemical plants, and some gas processing plants use compressed air; There are over 250,000 such devices in the production sector; There are between 90,000 and 130,000 in the transmission sector.

6. Pneumatic Device Schematic There are three basic designs for pneumatic devices: controllers; valve actuators; and self-contained devices. While controllers bleed gas continuously, valve actuators bleed gas only when the valve is stroked open and closed. Self-contained devices vent gas into the downstream pipeline, rather than the atmosphere. Pneumatic devices typically work as described below: A source of clean, high pressure gas is pressure controlled by a pressure regulator valve to a constant pneumatic gas supply pressure (typically 20 psi). Mechanical process measuring devices further regulate the supply gas pressure to a weak pneumatic signal (typically between 3 and 15 psi) depending on the process measurement: High to low level, pressure, temperature, and flow rate. The weak pneumatic signal flows into a controller which, through a precision set of nozzles and orifices, directs the pneumatic supply gas to or from the valve actuator. The valve actuator contains a movable diaphragm connected to the valve plug. When supply gas is routed to the actuator, the diaphragm pushes the valve plug open (or closed). When supply gas is vented, an opposing spring pushes the diaphragm back, closing (or opening) the valve. The weak control signal is often vented continuously (bled) to the atmosphere. The strong signal is vented intermittently – only when the valve opens or closes.There are three basic designs for pneumatic devices: controllers; valve actuators; and self-contained devices. While controllers bleed gas continuously, valve actuators bleed gas only when the valve is stroked open and closed. Self-contained devices vent gas into the downstream pipeline, rather than the atmosphere. Pneumatic devices typically work as described below: A source of clean, high pressure gas is pressure controlled by a pressure regulator valve to a constant pneumatic gas supply pressure (typically 20 psi). Mechanical process measuring devices further regulate the supply gas pressure to a weak pneumatic signal (typically between 3 and 15 psi) depending on the process measurement: High to low level, pressure, temperature, and flow rate. The weak pneumatic signal flows into a controller which, through a precision set of nozzles and orifices, directs the pneumatic supply gas to or from the valve actuator. The valve actuator contains a movable diaphragm connected to the valve plug. When supply gas is routed to the actuator, the diaphragm pushes the valve plug open (or closed). When supply gas is vented, an opposing spring pushes the diaphragm back, closing (or opening) the valve. The weak control signal is often vented continuously (bled) to the atmosphere. The strong signal is vented intermittently – only when the valve opens or closes.

7. Emissions from Pneumatic Devices Gas Industry Oil Industry Production 34.9 Bcf 21.7 Bcf Processing 0.6 Bcf --- Transmission 14.1 Bcf --- Total 49.6 Bcf 21.7 Bcf Total Gas/Oil 71.3 Bcf/yr Recent studies estimate methane losses from pneumatic devices at 71 Bcf per year. At $3.00 per thousand cubic feet, this equals $213 million per year. Note that throughout these presentations and the Lessons Learned in the handouts, we use a nominal $2.00 per thousand cubic feet as a wellhead value of gas. This varies by location, season, and production economics. You would use your most realistic value when following the economic examples. The production sectors of the gas and oil industries contribute nearly 80 percent of this loss. The gas industry production sector alone loses 34.9 Bcf per year. Recent studies estimate methane losses from pneumatic devices at 71 Bcf per year. At $3.00 per thousand cubic feet, this equals $213 million per year. Note that throughout these presentations and the Lessons Learned in the handouts, we use a nominal $2.00 per thousand cubic feet as a wellhead value of gas. This varies by location, season, and production economics. You would use your most realistic value when following the economic examples. The production sectors of the gas and oil industries contribute nearly 80 percent of this loss. The gas industry production sector alone loses 34.9 Bcf per year.

8. How Can Methane Emissions be Reduced? Option 1: Replace high-bleed devices with low-bleed devices Option 2: Retrofit controller with bleed reduction kits Option 3: Maintenance aimed at reducing losses Field experience shows that up to 80% of all high-bleed devices can be replaced or retrofitted with low-bleed equipment

9. Option 1: Replace High-Bleed Devices Most applicable to: Controllers: liquid-level and pressure Positioners and transducers Suggested action: evaluate replacements Replace at end of device’s economic life Early replacement Most liquid level and pressure controllers are in process services that will allow replacement with low-bleed devices. Exceptions include very large valves and valves (such as compressor bypass) that must act very fast and with precision. Valve positioners can sometimes be eliminated, otherwise they can function as low-bleed devices. Separate pneumatic transducers can be replaced with single unit, low-bleed electro-pneumatic transducers. Producers should evaluate the cost-effectiveness of replacing high-bleed devices in two situations: at the end of the device’s useful life or early replacement of a device that is functioning adequately. Early replacement is a more common scenario. When the instrument has become obsolete, repair parts are hard to find and repair will cost more than replacement. EPA/Gas STAR Partner “Rule of Thumb”: Average useful life of pneumatic devices is 7 years based on increased bleed and leakage from deterioration. When replacing a high-bleed controller for any reason, replace it with a low-bleed equivalent. Use caution when evaluating conversion to low-bleed devices and make sure the supply gas and piping are clean enough to avoid excessive plugging. Most liquid level and pressure controllers are in process services that will allow replacement with low-bleed devices. Exceptions include very large valves and valves (such as compressor bypass) that must act very fast and with precision. Valve positioners can sometimes be eliminated, otherwise they can function as low-bleed devices. Separate pneumatic transducers can be replaced with single unit, low-bleed electro-pneumatic transducers. Producers should evaluate the cost-effectiveness of replacing high-bleed devices in two situations: at the end of the device’s useful life or early replacement of a device that is functioning adequately. Early replacement is a more common scenario. When the instrument has become obsolete, repair parts are hard to find and repair will cost more than replacement. EPA/Gas STAR Partner “Rule of Thumb”: Average useful life of pneumatic devices is 7 years based on increased bleed and leakage from deterioration. When replacing a high-bleed controller for any reason, replace it with a low-bleed equivalent. Use caution when evaluating conversion to low-bleed devices and make sure the supply gas and piping are clean enough to avoid excessive plugging.

10. Option 1: Replace High-Bleed Devices (cont’d) Costs vary with size Typical costs range from $700 to $3,000 per device Incremental costs of low-bleed devices are modest ($150 to $250) Gas savings often pay for replacement costs in short periods of time (5 to 12 months)

11. Option 2: Retrofit with Bleed Reduction Kits Applicable to most high-bleed controllers Suggested action: evaluate cost effectiveness as alternative to early replacement Retrofit kit costs ~ $500 Payback time ~ 9 months For some high-bleed controllers, early replacement will not be cost-effective. Retrofitting the controller with a bleed reduction kit is a second option. Bleed reduction kits replace the nozzle-flapper design of conventional pneumatic controllers with a control valve. This valve controls the weak signal relay without continuous bleed. Generally, producers can realize 90 percent savings in gas consumption. For some high-bleed controllers, early replacement will not be cost-effective. Retrofitting the controller with a bleed reduction kit is a second option. Bleed reduction kits replace the nozzle-flapper design of conventional pneumatic controllers with a control valve. This valve controls the weak signal relay without continuous bleed. Generally, producers can realize 90 percent savings in gas consumption.

12. Option 3: Maintenance to Reduce Losses Applies to all pneumatic devices Suggested action: add to routine maintenance procedures Field survey of controllers Where process allows, tune controllers to minimize bleed Option 3 is to perform maintenance aimed at reducing gas losses. The suggested action is to modify routine maintenance procedures to incorporate the best management practices described below. First survey all installed controllers. The survey should identify high-bleed devices that are candidates for replacement, retrofit or repair. Record each device by location, function, make and model, condition, age, estimated useful life and bleed characteristics (continuous, intermittent or self-contained). Some Partners conduct pneumatic device surveys and have measuring devices available (e.g., High Flow Sampler) to measure bleed rates directly. Vendor reported bleed rates are typically less than in-service field measurements. Where the process allows, tuning controllers to minimize bleed is also a good way to reduce gas losses. Some controllers bleed as much as 10 scfh more at a narrow mid-range band than over a broad proportional band. Option 3 is to perform maintenance aimed at reducing gas losses. The suggested action is to modify routine maintenance procedures to incorporate the best management practices described below. First survey all installed controllers. The survey should identify high-bleed devices that are candidates for replacement, retrofit or repair. Record each device by location, function, make and model, condition, age, estimated useful life and bleed characteristics (continuous, intermittent or self-contained). Some Partners conduct pneumatic device surveys and have measuring devices available (e.g., High Flow Sampler) to measure bleed rates directly. Vendor reported bleed rates are typically less than in-service field measurements. Where the process allows, tuning controllers to minimize bleed is also a good way to reduce gas losses. Some controllers bleed as much as 10 scfh more at a narrow mid-range band than over a broad proportional band.

13. Option 3: Maintenance to Reduce Losses (cont’d) Suggested action (cont’d) Re-evaluate the need for pneumatic positioners Repair/replace airset regulators Reduce regulated gas supply pressure to minimum Routine maintenance should include repairing/replacing leaking components Cost is low Valve positioners are often unnecessary; removal cuts gas losses by 15 to 30 scfh. Repair or replace airset regulators with metal seat relief valves. Soft seat models leak less gas and are more easily maintained. Reducing the regulated gas supply pressure to the controllers’ minimum specification reduces bleed losses from all controllers. Lower gas supply pressure has the added benefit of reducing fugitive leakage from gaskets, tubing fittings and seals. Routine maintenance should look for, and repair, fugitive leaks. Relative to the other options, routine maintenance is the most cost-effective way to reduce gas loss. Valve positioners are often unnecessary; removal cuts gas losses by 15 to 30 scfh. Repair or replace airset regulators with metal seat relief valves. Soft seat models leak less gas and are more easily maintained. Reducing the regulated gas supply pressure to the controllers’ minimum specification reduces bleed losses from all controllers. Lower gas supply pressure has the added benefit of reducing fugitive leakage from gaskets, tubing fittings and seals. Routine maintenance should look for, and repair, fugitive leaks. Relative to the other options, routine maintenance is the most cost-effective way to reduce gas loss.

14. Five Steps for Reducing Methane Emissions from Pneumatic Devices In summary, the decision process follows five steps. Step 1: Locate and inventory all high-bleed pneumatic devices. Step 2: Whenever practical, use a measuring device, such as a Hi-Flow Sampler, to measure and record bleed rates. Alternatively, use vendor specification, recognizing that they are often understated. EPA defaults can also be used. Step 3: Establish the technical feasibility of alternatives. Vender or in-house expert advice may be necessary for determining the feasibility of certain alternatives. Step 4: Evaluate the economics of alternatives. Step 5: Develop a plan for the most cost-effective implementation. This may include procuring replacement, retrofit, and repair equipment in time for major maintenance events. In summary, the decision process follows five steps. Step 1: Locate and inventory all high-bleed pneumatic devices. Step 2: Whenever practical, use a measuring device, such as a Hi-Flow Sampler, to measure and record bleed rates. Alternatively, use vendor specification, recognizing that they are often understated. EPA defaults can also be used. Step 3: Establish the technical feasibility of alternatives. Vender or in-house expert advice may be necessary for determining the feasibility of certain alternatives. Step 4: Evaluate the economics of alternatives. Step 5: Develop a plan for the most cost-effective implementation. This may include procuring replacement, retrofit, and repair equipment in time for major maintenance events.

15. Suggested Analysis for Replacement Replacing high-bleed controllers at end of economic life Determine incremental cost of low-bleed device over high-bleed equivalent Determine gas saved with low-bleed device using manufacturer specifications Compare savings and cost Early replacement of high-bleed controllers Compare gas savings of low-bleed device with full cost of replacement

16. Economics of Replacement The above table shows the results of studies evaluating the cost-effectiveness of pneumatic device replacement. These are examples taken from Partners’ experiences to illustrate typical results achievable. For a variety of pneumatic devices, the analysis reflects that it is highly cost-effective to replace high-bleed devices. The analysis shows that such replacements pay for themselves within three years. All data is based on Partners’ experiences. The gas price is assumed to be $3/Mcf. For more information, refer to the Lessons Learned document for this BMP. The above table shows the results of studies evaluating the cost-effectiveness of pneumatic device replacement. These are examples taken from Partners’ experiences to illustrate typical results achievable. For a variety of pneumatic devices, the analysis reflects that it is highly cost-effective to replace high-bleed devices. The analysis shows that such replacements pay for themselves within three years. All data is based on Partners’ experiences. The gas price is assumed to be $3/Mcf. For more information, refer to the Lessons Learned document for this BMP.

17. Suggested Analysis for Retrofit Retrofit of low-bleed kit Compare savings of low-bleed device with cost of conversion kit Retrofitting reduces emissions by average of 90% In conducting this analysis, producers should take field measurements of bleed rates from the existing high-bleed device and also the retrofitted device.In conducting this analysis, producers should take field measurements of bleed rates from the existing high-bleed device and also the retrofitted device.

18. Economics of Retrofit This sample analysis of a pneumatic device retrofit demonstrates the cost-effectiveness of such an action. Within 14 months, the retrofit has paid for itself through the value of the recovered gas. All data is based on Partners’ experiences. The gas price is assumed to be $3/Mcf. For more information, refer to the Lessons Learned document for this BMP. This sample analysis of a pneumatic device retrofit demonstrates the cost-effectiveness of such an action. Within 14 months, the retrofit has paid for itself through the value of the recovered gas. All data is based on Partners’ experiences. The gas price is assumed to be $3/Mcf. For more information, refer to the Lessons Learned document for this BMP.

19. Suggested Analysis for Maintenance For maintenance aimed at reducing gas losses Measure gas loss before and after procedure Compare savings with labor (and parts) required for activity

20. Economics of Maintenance This table shows the compelling results reported by Gas STAR Partners who performed routine maintenance on pneumatic devices. Four procedures are shown: reducing supply gas pressure to minimum; repairing and re-tuning; changing settings; and removing valve positioners. Gas saving range from 44 Mcf/yr to a high of 175 Mcf/yr (latter value includes the cumulative bleed and leak reductions from all controllers affected by the lower supply pressure). Paybacks range from immediate (for changing settings and removing valve positioners) to 4-5 months (for reducing supply pressure or repairing and re-tuning). Include maintenance as part of an existing I/M program or contract for maintenance agreements to keep costs low. All data is based on Partners’ experiences. The gas price is assumed to be $3/Mcf. For more information, refer to the Lessons Learned document for this BMP.This table shows the compelling results reported by Gas STAR Partners who performed routine maintenance on pneumatic devices. Four procedures are shown: reducing supply gas pressure to minimum; repairing and re-tuning; changing settings; and removing valve positioners. Gas saving range from 44 Mcf/yr to a high of 175 Mcf/yr (latter value includes the cumulative bleed and leak reductions from all controllers affected by the lower supply pressure). Paybacks range from immediate (for changing settings and removing valve positioners) to 4-5 months (for reducing supply pressure or repairing and re-tuning). Include maintenance as part of an existing I/M program or contract for maintenance agreements to keep costs low. All data is based on Partners’ experiences. The gas price is assumed to be $3/Mcf. For more information, refer to the Lessons Learned document for this BMP.

21. Pneumatic Devices Factors affecting economics of replacement Operating cost differential and capital costs Estimated leak rate reduction per new device Price of gas ($/Mcf)

22. Lessons Learned Most high-bleed pneumatics can be replaced with lower bleed models Replacement options save the most gas and are often economic Retrofit kits are available and can be highly cost-effective Maintenance is low-cost and reduces gas loss Partners’ experiences with this BMP lead to a number of important lessons. Natural Gas STAR Partners have found that many high-bleed devices can successfully be replaced with lower bleed models. Field experience shows that up to 80 percent of all high-bleed devices can be either replaced or retrofitted with low-bleed devices. Replacement options (either replacement at the end of useful life or early replacement) save the most gas and are often economical. Retrofit kits are available for most high-bleed controllers and can be highly cost-effective. Maintenance strategies are low-cost, apply to all pneumatic devices and reduce gas loss. One thing to consider when evaluating low-bleed devices is that the smaller orifices can be subject to clogging with debris from corroded pipes: Pipe condition should be evaluated before retrofitting with smaller orifice, low-bleed equipment; and More frequent maintenance attention should be given to the low-bleed equipment at the beginning of its use. Partners’ experiences with this BMP lead to a number of important lessons. Natural Gas STAR Partners have found that many high-bleed devices can successfully be replaced with lower bleed models. Field experience shows that up to 80 percent of all high-bleed devices can be either replaced or retrofitted with low-bleed devices. Replacement options (either replacement at the end of useful life or early replacement) save the most gas and are often economical. Retrofit kits are available for most high-bleed controllers and can be highly cost-effective. Maintenance strategies are low-cost, apply to all pneumatic devices and reduce gas loss. One thing to consider when evaluating low-bleed devices is that the smaller orifices can be subject to clogging with debris from corroded pipes: Pipe condition should be evaluated before retrofitting with smaller orifice, low-bleed equipment; and More frequent maintenance attention should be given to the low-bleed equipment at the beginning of its use.

23. Case Study – Marathon Surveyed 158 pneumatic devices at 50 production sites Half of the controllers were low-bleed High-bleed devices included 35 of 67 level controllers 5 of 76 pressure controllers 1 of 15 temperature controllers One Gas STAR Partner, Marathon Oil Company, conducted a survey of pneumatic devices at 50 of its production sites and found that many of the devices were high-bleed. Measured gas emissions totaled 583 scfh (5.1 MMcf/yr). One Gas STAR Partner, Marathon Oil Company, conducted a survey of pneumatic devices at 50 of its production sites and found that many of the devices were high-bleed. Measured gas emissions totaled 583 scfh (5.1 MMcf/yr).

24. Marathon Study:Hear It? Feel It? Replace It! Measured gas losses total 5.1 MMcf/yr Level controllers account for 86% of losses Losses averaged 7.6 cf/hr Losses ranged up to 48 cf/hr Concluded that excessive losses can be heard or felt Based on this survey, Marathon concluded that if a leak could be felt or heard then it warranted further attention. Based on this survey, Marathon concluded that if a leak could be felt or heard then it warranted further attention.

25. Recommendations Evaluate all pneumatics to identify candidates for replacement and retrofit Choose lower bleed models at change-out where feasible Identify candidates for early replacement and retrofits by doing economic analysis Improve maintenance Develop an implementation plan

26. Discussion Questions To what extent are you implementing this BMP? How can this BMP be improved upon or altered for use in your operation(s)? What are the barriers (technological, economic, lack of information, regulatory, etc.) that are preventing you from implementing this technology?