Partner Reported Opportunities (PROs) PRO Fact Sheet No. 301 for Reducing Methane Emissions 

Convert Pneumatics to Mechanical 

Controls 

Technology/Practice Overview 

Description 

Remote, non-electrified sites often use 

natural gas powered pneumatic

controllers for process control. The 

controllers are designed to continuously 

bleed natural gas resulting in significant

methane emissions to the atmosphere.

EPA’s Natural Gas STAR Partners 

report gas savings by replacing

pneumatic controllers with mechanical 

devices. 

The most common mechanical control 

device is a level controller, which uses 

mechanical linkages to translate the 

position of a liquid-level float to the 

position of a drain valve. No gas is used

in the measurement of liquid level or in 

the valve actuation, and reliability is 

very high. 

One Partner installed vertical separators 

equipped with mechanical dump valves

at low pressure, low volume producing 

wells, instead of vertical separators 

equipped with pneumatic dump valves.

Other partners have implemented this 

practice at oil and gas production sites 

and midstream dehydration facilities 

resulting in significant environmental 

and economic benefits. 

A separator operating at high pressure

and liquid volume requires the dump 

valve to be continuously throttled, 

allowing fluids to constantly flow out of 

the vessel. As lease production matures,

and working pressure and fluid 

Estimated 

Gas Price 

Annual 

Methane 

Savings 

Value of 

Annual 

Gas Savings* 

Estimated 

Implementation 

Cost 

Incremental 

Operating Cost 

Payback 

(months) 

$7.00/Mcf 227 Mcf $1,690 

$3,000 (full 

replacement cost) 

$1,000 (including 

salvage value)1 

$0 

$0 

20 Months 

7 Months 

$5.00/Mcf 227 Mcf $1,200 $3,000 

$1,000 

$0 

$0 

29 Months 

10 Months 

$3.00/Mcf 227 Mcf $725 $3,000 

$1,000 

$0 

$0 

47 Months 

16 Months 

Economic and Environmental Benefits 

Economic Evaluation 

 Improved equipment reliability at remote sites 

 Lower operating and maintenance costs 

Additional Benefits: 

Estimated annual methane emission reductions 227 Mcf per mechanical dump separator 

Methane Savings 

* Whole gas savings are calculated using a conversion factor of 94% methane in pipeline quality natural gas. 1 In this scenario, the replaced separator is installed at a different site, and therefore, includes a salvage 

value. 

Compressors/Engines 

Dehydrators 

Directed Inspection & 

Maintenance 

Pipelines 

Pneumatics/Controls 

Tanks 

Valves 

Wells 

Other 

Applicable Sector(s) 

Production 

Processing 

Transmission 

Distribution 

Other Related Documents: 

Convert Natural Gas-Driven 

Chemical Pumps, PRO No. 202 

Eliminate Unnecessary 

Equipment and/or Systems, 

PRO No. 504 

Convert Gas Pneumatic Controls 

to Instrument Air, Lessons 

Learned 

Options for Reducing Methane 

Emissions From Pneumatic 

Devices in the Natural Gas 

Industry, Lessons Learned 
Convert Pneumatics to Mechanical Controls (Cont’d) 

 

Water

PRO Fact Sheet No. 301 Continued 

Convert Pneumatics to Mechanical Controls (Cont’d) 

Separator with Mechanical Dump Operating Requirements 

Source: S. Bumgardner, Advanced Resources International, inc. 

Degassing

Baffle

Gas

Inlet Diverter

Demister

Gas

Weir

Drain Plate

Add drain to 

bottom of inlet

Degassing 

Baffle 

Gas 

Inlet Diverter 

Demister 

Water 

Gas 

Weir 

Drain Plate 

Add drain to 

bottom of inlet 

production decline, the need for pneumatic throttle

control on vessel dumps is eliminated. At this point, the 

lease equipment is evaluated and separators with 

pneumatic dump controls are frequently replaced by

separators with mechanical dumps. 

Mechanical Dump Separator 

Source: Chesapeake Energy 

Mechanical level controllers, or ‘dumps’, operate by a float

riding on the liquid phase contained within a separator or

other vessel. The float is coupled by a rod to the external

linkage that moves the dump valve down to open and up

to close. The only maintenance for a mechanical dump is 

to lubricate the linkages and clean the float arm housing.

For separators, the reservoir pressure and water 

production of the lease must be low enough so that

continuous throttling of the fluid stream is not needed. 

Applicability 

This technology is applicable to gas-driven pneumatic

controllers where the process measurement is in close

proximity to the flow control valve, flowing pressure is 

moderate to low, and fine throttling control of the 

discharge stream is not necessary. 

The average methane content of natural gas varies by natural gas 

industry sector. The Natural Gas STAR Program assumes the 

following methane content of natural gas when estimating methane savings for Partner Reported Opportunities. 

Production 79 % 

Processing 87 % 

Transmission and Distribution 94 % 

Methane Content of Natural Gas 

Methane Emissions 

Mechanical controls eliminate both the process controller 

bleed and valve actuation vent emissions. A rule of 

thumb for estimating gas emissions from process controls 

is one standard cubic foot per minute (1 scf/min) of gas for

each control loop, which consists of the process 

measurement and valve actuator. The volume of power 

gas used by separator dump controls and other pneumatic

control devices are also available from the manufacturers 

of the equipment. 

One Partner reports annual methane emissions of 227

Mcf from the pneumatic actuator controls of each of their 

separators. The average methane content of natural gas 

in this Partner’s operations is 89 percent, so estimated 

annual natural gas savings are 255 Mcf per mechanical 

dump installation. 

2 
Convert Pneumatics to Mechanical Controls (Cont’d) 

 

 

 

PRO Fact Sheet No. 301 Continued 

Convert Pneumatics to Mechanical Controls (Cont’d) 

Economic Analysis 

Basis for Costs and Savings 

Partner-reported annual gas savings are 255 Mcf per

each pneumatic-controlled separator replaced by a 

separator with mechanical controls. Assuming a gas

price of $5.00/ Mcf, the value of the gas saved is $1,275 

per separator. The replacement cost of a separator with a 

mechanically-controlled liquid dump valve is 

approximately $3,000. Often the existing pneumatic 

controlled separator can be refurbished and installed on a 

new well with higher gas pressures and water volumes. 

In this case, the replacement cost of the mechanical dump 

separator is effectively offset by moving the 

pneumatically controlled separator to a new high 

pressure, high volume well. 

Another Partner reports a program that replaced the gasliquid separators on 100 wells per year with mechanical 

dump separators. The reporting Partner finds it easier to

replace the entire separator rather than change out only

the pneumatic controls. If the pneumatic-control 

separator can be installed at another well site, 

approximately two-thirds of the replacement cost ($2,000)

is applied to the new site and the remaining replacement 

cost ($1,000) is applied to the mechanical dump 

separator. Mechanical dump separators operate with less 

maintenance effort and operator time, and are 

mechanically simple devices. Incremental operating costs

are virtually zero. If the typical value of gas saved is 

$1,275 per separator per year, project payback ranges 

from approximately 10 months for estimated 

implementation cost of $1,000 to 29 months if the full 

separator replacement cost of $3,000 is assumed. 

Discussion 

The cost of a mechanical process control system may

include the process measurement equipment, the 

mechanical valve actuator, and piping modifications to 

move the control valve closer to the process vessel.

Alternatively, Partners find it easier to replace the entire

separator rather than just the pneumatic control. 

Mechanical process control systems reduce the loss of a 

valuable product while requiring less maintenance effort 

and operator time due to mechanical simplicity. 

EPA provides the suggested methane emissions estimating methods contained 

in this document as a tool to develop basic methane emissions estimates only. 

As regulatory reporting demands a higher-level of accuracy, the methane emission estimating methods and terminology contained in this document may not 

conform to the Greenhouse Gas Reporting Rule, 40 CFR Part 98, Subpart W 

methods or those in other EPA regulations. 

2011 3