RECIPROCATING COMPRESSORS

 RECIPROCATING COMPRESSORS

RECIPROCATING COMPRESSORS

Reciprocating compressor ratings vary from fractional to

more than 40,000 hp per unit. In gas processing it would be

unusual for units larger than 10,000 hp to be used. Pressures

range from low vacuum at suction to 30,000 psi and higher at

discharge for special process compressors.

Reciprocating compressors are furnished either single-stage

or multi-stage. The number of stages is determined by the over-

all compression ratio.

 The compression ratio per stage (and valvelife) is generally limited by the discharge temperature and usu-ally does not exceed 4, although small-sized units (intermittentduty) are furnished with a compression ratio as high as 8.Gas cylinders are generally lubricated, although a non-lubricated design is available when warranted example: nitrogen, oxygen, and instrument air On multistage machines, intercoolers may be provided between stages. These are heat exchangers which remove theheat of compression from the gas and reduce its temperature to approximately the temperature existing at the compressor intake. 

Such cooling reduces the actual volume of gas going to the high pressure cylinders, reduces the horsepower required

for compression, and keeps the temperature within safe operat-

ing limits.

Reciprocating compressors should be supplied with clean gas

as they cannot satisfactorily handle liquids and solid particles

that may be entrained in the gas. Liquids and solid particles tend

to destroy cylinder lubrication and cause excessive wear. Liquids

are non-compressible and their presence could cause major dam-

age to the compressor cylinder or frame components.

Reciprocating compressors are typically designed to one of

the following industry standard specifications:

API Standard 618 “Reciprocating Compressors for Petro-

leum, Chemical, and Gas Industry Services.”

ISO Standard 13631: 2002, “Petroleum and Natural Gas In-

dustries — Packaged Reciprocating Compressors.”

Low to moderate speed compressors, typically 300–700 rpm,

have historically been used in refineries, chemical plants and

also can be used in gas plant service. They are normally driven

by electric motors. These compressors are typically applied in

accordance with API Standard 618 “Reciprocating Compressors

for Petroleum, Chemical and Gas Industry Services.”

Moderate to high speed compressors, typically 600–1800

rpm packaged separable compressors are used for field gas

compression, mid-stream compression, gas plant and mainline

compression. These units are normally driven by gas engines

or electric motors. These compressors are typically applied in

accordance with ISO Standard 13631.