Lessons Learned 

from Natural Gas STAR Partners 

Replacing Gas-Assisted Glycol Pumps 

with Electric Pumps 

Executive Summary 

Approximately 36,000 glycol dehydrators in the natural 

gas production sector are used to remove water from the

gas. Most glycol dehydration systems use triethylene 

glycol (TEG) as the absorbent fluid and rely on pumps to 

circulate TEG through the dehydrator. Operators use two 

types of circulation pumps: gas-assisted glycol pumps, also 

referred to as “energy-exchange pumps,” and electric 

pumps. 

Gas-assisted pumps are the most common circulation 

pumps in remote areas that do not have an electrical 

power supply. They are basically pneumatic gas driven

pumps, specially designed to take advantage of the energy

of high-pressure natural gas entrained in the rich (wet) 

TEG leaving the gas contactor. Additional high-pressure 

wet production gas is necessary for mechanical advantage,

and therefore more methane rich gas is carried to the TEG

regenerator, where it is vented with water boiled off of the

rich TEG. The mechanical design of these pumps places

wet, high-pressure TEG opposed to dry, low pressure TEG,

separated only by rubber seals. Worn seals result in 

contamination of the lean (dry) TEG making it less 

efficient in dehydrating the gas, requiring higher glycol

circulation rates. Typical methane emissions are about

1,000 cubic feet (Mcf) for each million cubic feet(MMcf) of 

gas treated. 

Replacing gas-assisted pumps with electric pumps

increases system efficiency and significantly reduces 

emissions. For example, a 10 MMcf per day dehydrator

could save up to 3,000 Mcf of gas a year, worth $21,000. 

Technology Background 

Most natural gas producers use triethylene glycol (TEG)

gas dehydrators to remove water from the natural gas 

stream to meet pipeline quality standards. TEG is 

circulated through the dehydration system using pumps

powered either by an electric motor or by a gas expansion 

piston or turbine driver. The latter is called a “gasassisted” or “energy-exchange” pump. In some operations,

a combination gas-assist/electric pump system may be 

used. 

The gas dehydration process includes the following 

elements: 

Wet natural gas is fed into a glycol contactor, where 

it bubbles up counter-current through “lean 

TEG” (triethylene glycol without absorbed water) in

the contactor tower trays. 

Lean TEG absorbs water and under pressure, some 

methane from the natural gas stream-becoming “rich

TEG.” 

 Dry gas goes to the sales pipeline. 

 A reboiler operating at atmospheric pressure

regenerates the rich TEG by heating the glycol to

drive off water, absorbed methane and other 

contaminants, which are vented to the atmosphere. 

 The regenerated (lean) TEG is pumped back up to 

contactor pressure and injected at the top of the 

contactor tower. 

Method for Reducing 

Natural Gas Losses 

Volume of Natural 

Gas Savings (Mcf) 

Value of Natural Gas Savings 

($) Cost of 

Implementation ($) 

Payback (Months) 

$3 per 

Mcf 

$5 per 

Mcf 

$7 per 

Mcf 

$3 per 

Mcf 

$5 per 

Mcf 

$7 per 

Mcf 

Replace gas-assisted 

pumps on glycol 

dehydrators with 

electric pumps 

360 to 36,000 per 

dehydration system1 

$1,150 -

115,000 

$1,900 -

191,000 

$2,680 -

268,000 $2,700 - $15,100 2– 29 1 - 17 

1 Depending on TEG circulation rate and inlet gas temperature and pressure, as reported by Natural Gas STAR partners. 

1 - 12 

Economic and Environmental Benefits 

1 
 

 

Replace Gas-Assisted Glycol Pumps With Electric Pumps 

(Cont’d) 

Exhibit 1 is a diagram of a typical glycol dehydrator

system. The atmospheric vent stack on the glycol reboiler/ 

regenerator is the main source of methane emissions. 

Reduction of methane emissions is achieved by reducing

the amount of wet gas bypassed to supplement the rich

TEG that is regenerated in the reboiler. There are three 

ways to reduce the methane content of the rich TEG 

stream: 

Reducing the TEG circulation rate. 

Installing a flash tank separator in the dehydration

loop. 

Replacing gas-assisted pumps with electric pumps. 

Exhibit 1: Dehydrator Schematic 

Replacing gas-assisted pumps with electric pumps is the 

subject of this Lessons Learned paper. The other 

methane emission reduction options are discussed in 

EPA’s Lessons Learned: Optimize Glycol Circulation and

Install Flash Tank Separators in Glycol Dehydrators. 

Gas-Assisted Pumps 

The most common circulation pump used in dehydrator

systems is the gas-assisted glycol pump. An example of a 

popular piston type is shown in Exhibit 2. These 

mechanical pumps are specially designed to use rich TEG

and natural gas at high pressure for power. By design, gasassisted glycol pumps increase emissions from dehydrator 

systems by passing the pneumatic driver gas entrained 

with rich TEG to the reboiler. A basic overview of the 

pump’s operation is described below: 

The high-pressure natural gas entrained in rich TEG 

from the contactor (plus additional wet, high 

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 

pressure gas) expands from contactor pressure (200 

to 800 psig) down to reboiler pressure (zero psig),

pushing against the driver side of the main cylinder

piston. 

The other side of that piston pushes a cylinder full of 

low-pressure lean TEG out to the contactor at highpressure. 

The driving piston is connected to a mirror-image

piston, which simultaneously expels low-pressure

rich TEG to the regenerator, while sucking in lowpressure lean TEG from the regenerator. 

At the end of the stroke, slide valves switch the 

position of the pilot piston, redirecting high-pressure 

rich TEG to the opposite drive cylinder. Check valves 

on the suction and discharge from the lean TEG 

cylinders prevent back-flow. 

The pistons are then driven back in the other 

direction, one expanding gas in the rich TEG while 

pressuring lean TEG to the contactor, the other 

expelling the now low-pressure rich TEG to the 

regenerator while filling the other side with lowpressure lean TEG from the regenerator. 

The driver-side rich TEG mixture with low-pressure 

natural gas passes to the reboiler where the 

entrained gas separates and water is boiled out of 

solution with the TEG. 

The water vapor and separated gas mixture of 

methane and other hydrocarbon gas contaminants 

(VOCs and HAPs) are vented to the atmosphere. 

At the end of each stroke, the flow paths are 

switched, and high-pressure rich TEG pushes the 

pistons back. 

This type pump has an inherent design requirement that 

extra high-pressure gas be added to supplement the gas 

2 
 

 

 

Replace Gas-Assisted Glycol Pumps With Electric Pumps 

(Cont’d) 

absorbed in the rich TEG from the contactor (about two 

volumes for one) to provide mechanical advantage on the 

driver side. This means that a gas-assisted pump passes

about three times as much gas to the regenerator as an 

electric motor driven pump would. Furthermore, gasassisted pumps place high-pressure wet TEG opposite lowpressure dry TEG in four locations with rings on the two 

pistons and “O-rings” on the central piston connecting rod

separating them. As the piston rings becomes worn, 

grooved, or the O-rings wear, rich TEG leaks past, 

contaminating the lean TEG. This contamination 

decreases the dehydrator’s capacity to absorb water and

reduces system efficiency. Eventually, the contamination

becomes sufficient to prevent the gas from meeting

pipeline specifications (commonly 4 to 7 lb of water per 

MMcf). 

As little as 0.5 percent contamination of the lean TEG 

stream can double the circulation rate required to 

maintain the same effective water removal. In some cases, 

operators can over circulate the TEG as the dehydrator

loses efficiency, which in turn, can lead to even greater 

emissions. 

Economic and Environmental Benefits 

Electric Pumps 

In contrast to gas-assisted pumps, electric motor driven 

pumps have less design-inherent emissions and no 

pathway for contamination of lean TEG by the rich stream. 

Electric pumps only move the lean TEG stream; the rich 

Exhibit 2: Electric Drive Gear Pump 

Source: Kimray, Inc. 

TEG flows by pressure drop directly to the regenerator, 

and contains only dissolved methane and hydrocarbons. 

Exhibit 2 shows an example of an electric glycol pump 

assembly. 

Using electric pumps as alternatives to gas-assisted pumps 

can yield significant economic and environmental benefits,

including: 

Financial return on investment through 

reduced gas losses. Using gas-assisted glycol

pumps reduces methane emissions by a third or 

more. All of the wet production gas remains in the 

system to be dehydrated and sold as product. In 

many cases, the cost of implementation can be

recovered in less than 1 year. 

Increased operational efficiency. Worn O-rings 

in gas-assisted glycol pumps can cause contamination

of the lean TEG stream in the dehydrator, reducing

system efficiency and requiring an increase in glycol

circulation rate, compounding the methane 

emissions. The design of electric pumps eliminates 

the potential for this contamination to occur and 

thereby increases the operational efficiency of the 

system. 

Reduced maintenance costs. Replacing gasassisted glycol pumps often results in lower annual 

maintenance costs. The floating piston O-rings in gas

-assisted pumps must be replaced when they begin to

leak, typically every 3 to 6 months. The need for this

replacement is eliminated when electric pumps are

employed. 

 Reduced regulatory compliance costs. The cost 

of complying with federal regulations of hazardous

air pollutants (HAPs) can be reduced through the use 

of electric pumps. Dehydrator HAP emissions, 

including volatile organic compounds such as 

benzene, toluene, ethyl benzene, and xylene (BTEX),

are significantly lower in units powered by electric 

pumps. 

Five Steps to Evaluate the Use of Electric Pumps 

1. Determine whether an electricity source is available. 

2. Determine the appropriate size of the electric pump. 

3. Estimate capital, operation, and maintenance costs. 

4. Estimate the quantity and value of gas savings. 

5. Calculate the net economic benefit of replacement. 

3 
 

 

 

 

 

 

 

 

 

 

 

Replace Gas-Assisted Glycol Pumps With Electric Pumps 

(Cont’d) 

Decision Points 

A five-step process can be used to evaluate replacement of

gas-assisted glycol pumps with electric pumps. Each step 

requires field data to accurately reflect conditions at the

site being evaluated. 

Step 1: Determine whether an electricity source is 

available. 

Electricity to power an electric pump can be purchased

from a local grid or generated onsite using lease or casing

head gas that might otherwise be flared. If a source of 

electricity is available or can be obtained cost-effectively,

the operator should proceed to Step 2. When no electricity 

source is available, a gas-assisted glycol pump might be

the only option. Combination hydraulicelectric pumps 

should also be considered for field situations where only

single-phase power is available, purchased power costs are 

high, or there is insufficient electrical service for a large 

electric motor. A combination pump uses high-pressure,

wet glycol to drive a hydraulic rotary gear motor/pump; a 

small single-phase electric motor is added for mechanical 

advantage, in place of the bypassed wet gas in the gasassisted pump. In either case, using a properly sized, wellmaintained, efficient pump maintained at the correct 

circulation rate can minimize gas loss. 

Step 2: Determine the appropriate size of the electric 

pump. 

A variety of electric pumps are available to meet sitespecific operational requirements. Electric TEG pumps can 

be powered by AC or DC, single phase or 3-phase, 60 Hz or 

50 Hz. They are available with a choice of variable or 

constant operating speeds. Pump capacities range from 10 

to 10,000 gallons per hour (GPH). 

The correct pump size for a dehydrator system should be 

calculated based on the circulation rate and the operating

pressure of the system. Exhibit 3 illustrates how to 

calculate the horsepower needed (in Brake Horsepower or 

BHP) for an electric pump using typical system

information. 

In the example shown in Exhibit 3, an operator would need 

Exhibit 3: Sizing the Pump 

Given: 

Calculate: 

Q = Circulation rate (gallons per minute) = 5 gal/min 

P = Pressure (in psig) = 800 psig 

E = Efficiency = 0.85 

BHP = (Q x P) x (1/E) 

= (5 x 800/1,714) x (1/0.85) 

BHP = 2.75 

at least a 2.75 horsepower pump, and would therefore 

round up to the next available size (i.e., a 3.0 BHP pump). 

Operators might wish to obtain a pump one size larger 

than called for by the formula above. A larger pump

provides additional capability to increase the glycol

circulation rate, if needed, to accommodate input gas with

higher water content, or to meet more stringent output 

specifications. Variable speed electric pumps are also 

available. Although larger pumps or variable speed pumps

can cost slightly more to operate, a larger size provides an

additional measure of safety and flexibility to cover 

contingencies. 

Step 3: Estimate capital , operation, and maintenance 

costs. 

Costs associated with electric pumps include capital to 

purchase the equipment, installation, and ongoing 

operation and maintenance. 

Capital and installation costs 

Electric pumps can cost from $1,425 to nearly $12,953, 

depending on the horsepower of the unit. Exhibit 4 

presents a range of sample capital costs for electric pumps 

of different sizes typically used for glycol dehydrators. 

Operators should also consider installation costs when 

evaluating the overall economics of electric pumps. 

Estimate 10 percent of capital costs for installation. 

Coordinating replacements with planned maintenance 

Exhibit 4: Capital Cost of Electric Pumps 

Pump Motor Size 

(BHP) 0.25 0.50 0.75 1.0 1.5 2.0 3.0 5.0 7.5 10 

Pump and Motor 

Cost ($) 1,420 1,485 1,550 1,630 1,680 1,770 1,845 3,795 3,995 4,205 

4 
 

 

 

 

 

 

 

 

 

 

 

Replace Gas-Assisted Glycol Pumps With Electric Pumps 

(Cont’d) 

shutdowns can minimize installation costs. 

Operation and maintenance costs 

The primary operational cost of an electric pump is the 

electricity needed to power the unit. In general, the 

kilowatt (kW) requirement to run a pump is nearly the 

same as BHP. For example, a 3.0 BHP pump would

require approximately 3.0 kW to operate. 

In 2006, the average cost of purchased electricity in the

commercial and industrial sectors ranged from $0.061 to

$0.094 per kilowatt-hour (kWh) nationally; site-generated 

electricity cost approximately $0.02 per kWh. If electricity 

costs are assumed to be approximately $0.075 per kWh,

the estimated cost for purchased power for the 3.0 BHP 

pump identified above would be $1,971 per year (3.0 kW x 

8,760 hrs/yr x $0.075/kWh). The cost for site generated

electricity would be about $525 per year (3.0 kW x 8,760 

hrs/yr x $0.02/kWh). 

Typical maintenance costs for gas-assisted glycol pumps

range from $270 to $530 annually. Maintenance cost is 

primarily associated with internal O-ring replacements 

and related labor costs. Normally, these replacements are

necessary once every three to six months. 

Electric pumps are usually gear-driven. They have no

reciprocating pump parts and do not depend on 

elastomeric parts, slides, pistons, check valves, or internal

O-rings, which are all subject to wear, deterioration, and

replacement. As a result, maintenance costs for electric 

pumps are generally less than maintenance costs for gasassisted glycol pumps. Annual costs for electric pumps can 

be expected to be about $263 per year for labor, 

consumables (lubrication and seals), and inspection. 

Step 4: Estimate the quantity and value of gas savings 

Because electric pumps emit no methane, emissions 

savings from an electric pump installation are equal to the

emissions from the gas-assisted pump being replaced. The 

quantity of avoided emissions can then be multiplied by

the market price of gas to determine the total value of gas

savings. Note: if the glycol dehydration unit has a flash 

tank separator, and a beneficial use for all gas recovered, 

then the gas savings might not, by itself, provide enough

justification for installing an electric pump. 

(A) Estimate methane emissions from gas-assisted 

pump. 

Estimating emissions is a two-step process, which consists 

of calculating an emissions factor for the unit’s operational 

Exhibit 5: Estimate Methane Emissions from 

Glycol Dehydrators1 

Step 1: Calculate Emissions Factor 

Given: EF = Emission Factor (scf natural gas emitted/MMcf gas

 processed) 

PGU = Pump Gas Usage (scf natural gas emitted/gallon of 

 TEG)2 

G = Glycol-to-Water Ratio (gallons of TEG/lb water

 removed) 3 

WR = Water Removed Rate (lb water removed/MMcf gas 

 processed) 

OC = Over Circulation Rate 

Calculate: EF = PGU x G x WR x OC 

Step 2: Calculate Total Emissions 

Given: TE = Total Emissions 

AF = Activity Factor (MMcf gas processed annually) 

Calculate: TE = EF x AF 

1

 Calculation methods and standard values are presented in EPA’s Lessons 

Learned: Optimize Glycol Circulation and Install Flash Tank Separators in Glycol 

Dehydrators. 

2

 Industry Rule-of-Thumb: 3 cubic-ft/gal for gas-assisted pump, 1 cubic-ft/gal 

for electric pump; the difference being 2 cubic-ft/gal 

3 Industry accepted Rule-of-Thumb: 3 gal TEG/lb water. 

characteristics (pressure, temperature, moisture specs) 

and then multiplying the unit emissions factor by an

activity factor (amount of gas processed annually). Exhibit 

5 presents formulas for estimating the potential methane

emissions for a gas-assisted pump and, consequently, the 

potential methane savings from replacing the gas-assisted 

pump with an electric pump. 

Field operators often know or can calculate the pump gas

usage and the glycol-to-water ratio. To determine the 

quantity of water that needs to be removed (WR), refer to

Appendix A, which presents a set of empirically derived 

curves. Using the gas inlet temperature and system

pressure, the saturated water content can be determined

by reading the corresponding value where the psig curve 

intersects the temperature. Subtract 4 lb/MMcf to 7 lb/

MMcf of water from the water content value to determine 

WR. The 4 lb/MMcf to 7 lb/MMcf water content limitation

is based on typical pipeline specifications for water content 

in the gas stream. 

To estimate the over circulation ratio, use a 1:1 ratio (OC = 

1) if there is no over circulation and a 2.1:1 ratio (OC = 2.1)

if over circulation is an issue. These ratios are based on the 

average of measured ratios from 10 field units reported by 

5 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Replace Gas-Assisted Glycol Pumps With Electric Pumps 

(Cont’d) 

the Gas Research Institute. 

Two examples of determining water removal (WR),

emission factor (EF), and total emissions (TE) are provided 

on the pages that follow. Each example shows a range of

savings based upon the two different inlet assumptions.

Example 1 presents a high-pressure gas stream, and

Example 2 presents a low pressure stream. 

Example 1: High-Pressure Gas Stream: 

This example dehydration system has an inlet pressure of 

800 psig, a temperature of 94o F, and a glycol-to-water

ratio of 3.0 gallons of TEG per lb water recovered. Using

Appendix A, the saturated water content for the gas

stream is estimated by reading the corresponding value 

where the 800-psig curve intersects the 95o F line. In this 

example, the water content is about 60 lb per MMcf.

Subtracting the pipeline requirement of 7 lb/MMcf, results 

in 53 lb of water, which must be removed from the gas 

stream and absorbed by the TEG. The pump gas usage is 2 

scf of natural gas per gallon of TEG. 

Applying these data to the emissions factor formula results 

in a range of 318 to 668 scf gas emitted for every MMcf gas 

processed. Assuming the dehydrator processes 10 MMcf of

wet gas daily, the additional volume of the gas recovered

would be 1,160 to 2,440 Mcf per year. Exhibit 6 

summarizes this example. 

Example 2: Low-Pressure Gas Stream: 

The system uses an inlet pressure of 300 psig and a 

temperature of 94o F, and a glycol-to-water ratio of 3.0 

gallons of TEG per lb water recovered. Again referring to

the Smith Industries’ curves (Appendix A), the water

content is about 130 lb per MMcf. Therefore, 123 lb of 

water must be removed from the natural gas stream and 

absorbed by the TEG to meet the pipeline standards. In 

this example, the pump size is 3.0 BHP, and the pump gas 

usage is 2.8 scf of natural gas emitted per gallon of TEG.

Using the formula, an Emissions Factor (EF) of 1.03 to 

Exhibit 6: Example 1—Estimated Methane 

Emissions from a Glycol Dehydrator with High 

Pressure (800 psi) Inlet Gas 

Where EF = Emission Factor (scf natural gas emitted/

 MMcf gas processed) 

PGU = Pump Gas Usage (scf natural gas emitted/

 gallon of TEG) 

G = Glycol-to-Water Ratio (gallons of TEG/lb

 water removed) 

WR = Water Removed Rate (lb water removed/

 MMcf gas processed) 

OC = Over Circulation Rate 

TE = Total Emissions 

AF = Activity Factor (MMcfd gas processed) 

Given: PGU = 2 scf natural gas emitted/gallon TEG 

G = 3.0 gallons of TEG/lb of water removed 

WR = 53 lb of water remove/MMcf gas processed 

OC = 1:1 to 2.1:1 

AF = 10 MMcfd gas processed 

Calculate: EF = PGU x G x WR x OC

 = 2 x 3.0 x 53 x (Range: 1 to 2.1) 

 = 318 to 668 scf/MMcf 

TE = EF x AF

 = (318 to 668) x 10 

= (3,180 to 6,680) scfd x 365 days/

 year /1,000 scf/Mcf

 = 1,160 to 2,440 Mcf/year 

Exhibit 7: Example 2—Estimated Methane 

Emissions from a Glycol Dehydrator with Low 

Pressure (300 psi) Inlet Gas 

Where EF = Emission Factor (scf natural gas emitted/

 MMcf gas processed) 

PGU = Pump Gas Usage (scf natural gas emitted/

 gallon of TEG) 

G = Glycol-to-Water Ratio (gallons of TEG/lb

 water removed) 

WR = Water Removed Rate (lb water removed/

 MMcf gas processed) 

OC = Over Circulation Rate 

TE = Total Emissions 

AF = Activity Factor (MMcfd gas processed) 

Given: PGU = 2.8 scf natural gas emitted/gallon TEG 

G = 3.0 gallons of TEG/lb of water removed 

WR = 123 lb of water remove/MMcf gas 

processed 

OC = 1:1 to 2.1:1 

AF = 10 MMcfd gas processed 

Calculate: EF = PGU x G x WR x OC

 = 2.8 x 3.0 x 123 x (Range: 1 to 2.1) 

= 1,030 to 2,170 scf/MMcf 

TE = EF x AF

 = (1,030 to 2,170) x 10 

= (10,300 to 21,700) scfd x 365 days/ 

year /1,000 scf/Mcf

 = 3,760 to 7,921 Mcf/year 

6 
 

 

Replace Gas-Assisted Glycol Pumps With Electric Pumps 

(Cont’d) 

2.17 Mcf/MMcf is estimated. Assuming the dehydrator 

processes 10 MMcf of wet gas daily, the additional volume

of the gas recovered would be 3,760 to 7,921 Mcf per year. 

Exhibit 7 summarizes this example. 

(B) Calculate the value of the methane savings 

To determine the total value of the methane savings, 

simply multiply the total emissions reduction by the price 

of gas. Assuming a value of $7.00 per Mcf, both the highand low-pressure examples presented above yield

significant annual savings. Increased gas sales from the 

high-pressure system will range from $8,120 to $17,080 

per year, while the low-pressure system will yield savings 

from $26,320 to $55,447 per year. 

Step 5: Calculate the net economic benefit of 

replacement. 

To estimate the net economic benefit of replacing a gasassisted glycol pump with an electric pump, compare the 

value of the gas saved to the initial cost of the electric 

pump, plus the electricity and the operation and 

maintenance costs. 

As a general rule, if the cost of electricity exceeds the value

of recovered methane and avoided operation and 

maintenance costs, replacing the gasassisted glycol pump

cannot be justified on a cost-only basis. Even in such cases, 

however, other factors, such as lower cross contamination 

rates and environmental benefits (e.g., reduced VOC and 

HAP emissions) might still make the electric pumps an 

attractive option at certain sites. 

Exhibit 8 uses the low-pressure example from Step 4 to 

demonstrate the possible savings available to operators 

who purchase electricity. 

Nelson Price Indexes 

In order to account for inflation in equipment and 

operating & maintenance costs, Nelson-Farrar 

Quarterly Cost Indexes (available in the first issue of 

each quarter in the Oil and Gas Journal) are used to 

update costs in the Lessons Learned documents. 

The “Refinery Operation Index” is used to revise

operating costs while the “Machinery: Oilfield Itemized 

Refining Cost Index” is used to update equipment 

costs. 

To use these indexes in the future, simply look up the 

most current Nelson-Farrar index number, divide by 

the February 2006 Nelson-Farrar index number, and, 

finally multiply by the appropriate costs in the Lessons 

Learned. 

It is important to note that larger pump sizes require a 

larger up-front investment, and higher electricity costs 

might result in longer payback periods. It is therefore

important to correctly calculate the pump size required 

and to circulate the TEG at the optimal rate. 

In addition, as part of looking at the overall replacement 

Partner Reported Savings 

One Natural Gas STAR Partner reported recovering an 

average of 15,000 Mcf/year of methane by replacing 

four gas-assisted glycol pumps with electric pumps. At 

$7.00 per Mcf, this amounted to an average of $105,000

in additional product sales. 

Exhibit 8: Economic Benefit of Replacing Gas-Assisted Glycol Pump with an Electric Pump—Low 

Pressure Inlet Gas Example 

a Gas Valued at $7.00 per Mcf. 

b Including capital costs and installation cost, which is assumed to be 30 percent of the capital cost for this example. 

Gas Volume 

Saved per Year 

(Mcf) 

Value of Gas 

Saved per Yeara 

3.0 BHP ElectricPump Costb Electricity Cost 

per Year 

Electric Pump 

Maintenance ($/ 

Year) 

Gas-Assisted 

Pump Maintenance ($/Year) 

3,760 - 7,921 $26,320- $55,447 $2,400 $1,971 $263 $530 

Payback in 

months 

1-2 

7 
 

Replace Gas-Assisted Glycol Pumps With Electric Pumps 

(Cont’d) 

economics, operators should consider the timing of any 

replacements. Older gas-assisted glycol pumps, at the end 

of their useful lives, are typically good candidates for

replacement with an electric pump. Gas-assisted pumps 

that might not be at the end of their useful life, but that 

Exhibit 9: Gas Price Impact on Economic Analysis 

$3/Mcf $5/Mcf $7/Mcf $8/Mcf $10/Mcf 

Value of Gas $11,280 $18,800 $26,320 $30,080 $37,600 Saved 

Payback Pe- 3 2 2 2 1 riod (months) 

Internal Rate 

of Return 415% 729% 1042% 1199% 1512% 

(IRR) 

NPV $35,384 $63,891 $92,397 $106,651 $135,157 

have started to need more frequent maintenance as a

result of increased contamination, might also be good

candidates for replacement. 

When assessing options for glycol pumps and dehydrators,

natural gas price may influence the decision making

process. Exhibit 9 shows an economic analysis of installing 

an electric pump on a low pressure glycol dehydrator at 

different natural gas prices. 

Lessons Learned 

Installing electric pumps to replace gas-assisted glycol 

pumps can offer significant operational, environmental, 

and economic advantages. Natural Gas STAR partners 

offer the following lessons learned: 

 Gas-assisted glycol pumps can often be costeffectively replaced with electric pumps if there is a 

readily available source of electricity. 

Electric pumps are available with varying 

capabilities and efficiencies. Operators are 

encouraged to work with various pump

manufacturers to find the most appropriate type. 

In sizing an electric pump, operators might wish to 

obtain a pump that is one size larger than normal.

This will allow for additional circulation capacity that

can prove useful if the water content increases as the

field matures or “waters out.” 

Glycol pumps, whether gas-assisted or electric, 

represent only one element of a dehydration system. 

Operators should consider the dehydration process as 

a whole, including glycol composition, circulation 

rates, contactor temperature and pressure, inlet gas 

composition, dew point requirements, and reboiler 

temperatures. 

Partners considering replacing gas-assisted pumps 

with electric pumps should review the other 

opportunities for reducing methane emissions from

dehydration systems. See EPA’s Lessons Learned: 

Optimize Glycol Circulation And Install Flash Tank 

Separators In Glycol Dehydrators. 

Glycol dehydrators with flash tank separators might 

not be good candidates for replacing the gas-assisted 

pump, because most of the excess gas is recovered 

and put to beneficial use or recycled. 

Include reduction in methane emissions from 

replacing gas-assisted glycol pumps with electric 

pumps in annual reports submitted as part of the 

Natural Gas STAR Program. 

References 

American Petroleum Institute. Specification for Glycol-Type Gas 

Dehydration Units (Spec 12GDU). July 1993. 

American Petroleum Institute. Glycol Dehydration. PROFIT Training Series, 

1979. 

Ballard, Don. How to Improve Glycol Dehydration. Coastal Chemical 

Company. 

Collie, J., M. Hlavinka, and A. Ashworth. An Analysis of BTEX Emissions 

from Amine Sweetening and Glycol Dehydration Facilities. 1998 

Laurance Reid Gas Conditioning Conference Proceedings, Norman, 

OK. 

Garrett, Richard. Making Choices—A Look at Traditional and Alternative 

Glycol Pump Technology 

Gas Research Institute. Technical Reference Manual for GRI-GLYCalc TM 

Version 3.0 (GRI-96/0091). 

Gas Research Institute and U.S. Environmental Protection Agency. 

Methane Emissions from Gas-Assisted Glycol Pumps. January 1996. 

8 
Replace Gas-Assisted Glycol Pumps With Electric Pumps 

(Cont’d) 

The Hanover Compressor Company. Personal Contact. 

Kimray, Inc. Personal Contact. 

Radian International LLC, “Methane Emissions from the Natural Gas 

Industry. Volume 15: Gas-Assisted Glycol Pumps” Draft Final report, 

Gas Research Institute and U.S. Environmental Protection Agency, 

April 1996 

Rotor-Tech, Inc. Personal Contact. 

Tannehill, C.C., L. Echterhoff, and D. Leppin. “Production Variables Dictate 

Glycol Dehydration Costs.” American Oil and Gas Reporter, March 

1994. 

Tingley, Kevin. U.S. EPA Natural Gas STAR Program. Personal Contact. 

U.S. Environmental Protection Agency. National Emission Standards for 

Hazardous Air Pollutants for Source Categories: Oil and Natural Gas 

Production and Natural Gas Transmission and Storage-Background 

Information for Pro-posed Standards (EPA-453/R-94-079a, April 

1997). 

U.S. Environmental Protection Agency. Lessons Learned: Reducing the 

Glycol Circulation Rates in Dehydrators (EPA430-B-97-014, May 

1997). 

U.S. Environmental Protection Agency. Lessons Learned: Installation of 

Flash Tank Separators (EPA430-B-97-008, October 1997). 

U.S. Environmental Protection Agency. “Methods for Estimating Methane 

Emissions from National Gas and Oil Systems”. Emissions Inventory 

Improvement Program, Vol. III, Chapter 3, October 1999. 

9 
Replace Gas-Assisted Glycol Pumps With Electric Pumps 

(Cont’d) 

Appendix A 

Exhibit 10: Electric Drive Gear Pump 

Source: Kimray, Inc. 

10 
Replace Gas-Assisted Glycol Pumps With Electric Pumps 

(Cont’d) 

United States 

Environmental Protection Agency 

Air and Radiation (6202J) 

1200 Pennsylvania Ave., NW 

Washington, DC 20460 

October 2006 

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. 

11