Solutions beyond products...

Sour Gas CompressorsOil & Natural Gas Applications

Model NFT391 two-stage compressor

Corken’s reciprocating gas compressors are utilized in the completion and production phases of an oil well. Vapor recovery and casing gas removal are common applications. When a well is not connected to a pipeline, the extracted crude oil is temporarily stored in a tank battery at the well site. During this time, the natural gas within crude oil will build vapor pressure. To prevent the vapor from emitting to the atmosphere, a reciprocating gas compressor is used to recover and distribute to a gas gathering system. In a casing gas application, casing head gas collects in the annular space between the tubing and casing dramatically reducing the flow of the well. Our reciprocating gas compressors are used to reduce the back pressure allowing gas and crude to flow easily into the well bore.

When applying a reciprocating gas compressor into an oil and gas application, it is important to know whether it is a sweet or sour crude oil application. Sweet crude contains less than 0.5% hydrogen sulfide and is friendlier to the environment and the compressor. Our standard off-the-shelf compressor with carbon steel components is acceptable for sweet crude applications. In contrast sour crude has 0.5% or more hydrogen sulfide and is not friendly to the environment or the compressor. It is necessary to use proper materials of construction on several components to prevent sulfide stress cracking.

When choosing a compressor technology, one of the primary factors to consider is the maintenance capability of the user. All compressors will require maintenance, but reciprocating compressors do not generally require special training or equipment in order to maintain them. Corken compressors are simple to understand and maintain. Typical top end repairs can be done in the field in a few hours. This results in minimal down-time and maximum productivity.

Materials of ConstructionCorken NFD/NFT compressors use a number of material substitutions. These are based on NACE (MR-0175) recommendations, field experience, and industry standards. In general, carbon steel components have been replaced by stainless steel in order to prevent sulfide stress cracking. As a result, compressor failures will be significantly reduced ensuring the NFD/NFT series will provide safe operation and long service life.

Single and Double Distance Pieces ExplainedA distance piece is what makes any gas compressor unique and separates it from an ordinary air compressor. This is the center sect ion of the compressor that contains the compressor’s packing (seals). Corken NFD/NFT compressors use “long” type distance pieces that provide no rod over-travel from one set of packing to the next. This allows oil-free compression when needed, and provides one (D-style) or two (T-style) chambers that can collect any condensed liquids before they can contaminate the crankcase oil. Additionally, these chambers can be purged to control process gas leakage.

Purge systems are often customized for the particular application or operating conditions. Purge gas can be nitrogen, propane, sweet gas, or other suitable gas. A very low purge gas flow rate will generally suffice (see page 8 for a detailed illustration).

Cylinder LubricationLarge oilfield compressors always use cylinder lubrication to maximize the life of the piston rings, packing, and valves. These are the primary performance and wearing components of any piston type compressor. In Corken compressors, cylinder lubrication extends the life of these components by a factor of 4 or 5, and provides higher volumetric efficiency. This results in a significant decrease in downtime, lower repair parts cost and labor costs, and more efficient operation.

Cylinder lubrication also helps prevents corrosion – particularly in sour gas applications. The reduced corrosion minimizes or eliminates the need to replace the heavier iron parts of the compressor like the pistons, cylinders, etc. Cylinder lubrication is generally unavailable in other small gas compressors, but is a recommended option on all Corken NFD/NFT compressors.

Vertical Reciprocating Gas Compressors

Our material selections were carefully chosen with three things in mind:1. Safety—Less toxic gas released to the atmosphere

2. Economic Relief— Reduced maintenance costs, downtime, and compressor overhauls

3. Environmental Protection—Significantly reduces leakage of volatile organic compounds (VOCs)

2

Benefits:Safety benefits

• Reduces leakage of toxic H2S and health hazards

• Minimizes failures and leakage of flammable & toxic process gas

• Less maintenance and fewer site visits means less potential exposure to toxic gas

Environmental benefits

• Helps maintain environmental compliance

• Reduces greenhouse gas

• Lower toxic H2S emissions

Economic benefits

• Decreased downtime

• Lower long-term repair/replacement costs

• Significantly longer service life

Applications:

Features & Benefits

Features:• Materials of construction suitable for

sour gas

• Corken’s MC1002 corrosion resistant coating used on all wetted ductile iron parts

• Flanged process gas connections (RF ASME 300#)

• Single (NFD) and double (NFT) distance piece versions available

• Cylinder lubrication available (recommended)

• Available with optional crankcase heater

Adjustable packing screwLower packing (V-ring)

Oil deflector ring

Lower distance pieceBarrier 2(purge, pad, or vent)

Middle packing (V-ring)

Upper distance pieceBarrier 1(purge, pad, or vent)

Upper packing (V-ring)

300 lb RF ANSI Flange

Color Key:Parts containing MC1002 corrosion resistant coating.

Model NFT391 shown above

• Wellhead Casing Gas Reduction

• Vapor Recovery (VRU)

• Flare Elimination

• Gas Boosting

• Gas Gathering

• Gas Evacuation

• Gas Blanketing

• Fuel Gas Boosting

• Enhanced Oil Recovery

3

Performance Curves and Specifications

0

20

40

60

80

100

120

140

160

Suction Pressure (psig)

Cap

acit

y (M

CFD

)

0 20 3010 40 50 60 70 80

50 psig

100 psig

200 psig

500 psig

00

2

4

6

8

10

12

14

16

20 3010 40 50

Suction Pressure (psig)

Hor

sep

ower

60 70 80

50 psig

100 psig

200 psig 500 psig

Two-Stage NFD391/NFT391 Performance Curves

Curves based on Natural Gas, Specific gravity = 0.7, N = 1.26All data at maximum RPM or HP

Lubricated cylindersSite elevation = 1000’ ASL (305 m)

Bore - first stage inches (mm) 4.5 (114.3)Bore - second stage inches (mm) 2.5 (63.5)Stroke inches (mm) 3.0 (76.2)Speed range RPM 350–825Maximum power rating HP (kW) 15 (11)MAWP psig (barg) 600 (41.3)Rod load rating lb (kg) 4000 (1814)Maximum temperature rating °F (°C) 350 (177)

SpecificationsNFD391 D-style (double packed) NFT391 T-style (triple packed)

Available with a lubricatorViton®1 (standard), PTFE (optional)

Standard packing, Vacuum & Purge (optional)Available with optional crankcase heater

Extended crankshaft & heavy duty flywheel standard

1 Registered trademark of the DuPont Company.

4

Bore - x2 cylinders inches (mm) 4.0 (101.6)Stroke inches (mm) 3.0 (76.2)Speed range RPM 350–825Maximum power rating HP (kW) 15 (11)MAWP psig (barg) 335 (23.1)Rod load rating lb (kg) 4000 (1814)Maximum temperature rating °F (°C) 350 (177)

Performance Curves and Specifications

0

100

200

300

400

500

600

700

800

Suction Pressure (psig)

Cap

acit

y (M

CFD

)

0 10050 150 200 250 300

50 psig

100 psig

200 psig

300 psig

00

2

4

6

8

10

12

14

16

50 100 150

Suction Pressure (psig)

Hor

sep

ower

200 250 300

50 psig

100 psig

200 psig300 psig

Single-Stage NFD491/NFT491 Performance Curves

Curves based on Natural Gas, Specific gravity = 0.7, N = 1.26All data at maximum RPM or HP

Lubricated cylindersSite elevation = 1000’ asl (305 m)

SpecificationsNFD491 D-style (double packed) NFT491 T-style (triple packed)

Available with a lubricatorViton®1 (standard), PTFE (optional)

Standard packing, Vacuum & Purge (optional)Available with optional crankcase heater

Extended crankshaft & heavy duty flywheel standard

1 Registered trademark of the DuPont Company.

5

OutlineDimensionsTwo-Stage NFT391 with Lubricator

18-3/4(476)

LubricatorAssembly

4-11/16(119)

13-7/8(352)

4-11/16(119)

9-3/8(238)

1/2" Holes(13)

40-3/8(1,025)

35-11/16(907)

Cylinder Oil Drain1/4" NPT

PressurizationTube For

“F” PackingOnly

5 GrooveFlywheel

3-1/2(89)

4-1/8(105)

13-7/8(352)

27-1/16(687)

13-3/16(335)

5-7/8(149)

5(127)

Inlet:1-1/4" 300 lb.

RF ANSI Flange

Outlet:1-1/4" 300 lb.

RF ANSI Flange

All dimensions in inches (centimeters)

6

OutlineDimensions Single-Stage NFT491

5 GrooveFlywheel

4-1/8(105)

13-3/8(340)

5(127)

26-9/16(675)

35-5/8(905)

39-1/16(992)

Inlet:1-1/4" 300 lb.

RF ANSI Flange

5-5/8(143)

18-3/4(476)

5-5/8(143)

Outlet:1-1/4" 300 lb.

RF ANSI Flange

11/16(18)

1/2" Holes(13)

4-11/16(119)

4-11/16(119)

5-7/8(149)

All dimensions in inches (centimeters)

7

SG100 PRINTED IN THE USA JULY 2015

CORKEN, INC. • A Unit of IDEX Corporation3805 N.W. 36th St., Oklahoma City, OK 73112 U.S.A.

Phone (405) 946-5576 • FAX (405) 948-7343Visit our website at http://www.corken.com • E-mail us at cocsalesdept@idexcorp.com

Solutions beyond products...

@CorkenInc

A Distance Piece Purge System is Available for All D- and T-Style Compressors

PI

Purge GasTank

PI

Regulator A

Regulator B

Suc

tion

Scr

ubbe

r

Gas

Entrained Liquid

Purge Gas Flow

Gas Discharge

PI

Gas Suction

PI

Purge gas, process gas leakage, and condensed liquids are returned to the compressor’s suction scrubber

Virtually all gas leakage from the crankcase vent is purge gas

Contact your local distributor for more information.