Reciprocating compressors are generally classified as either low-speed (integral) compressors or high-speed (separable) compressors. API has provided a standard and specification for each type of compressor to help the user and the facility engineer provide reliable compressor installations.
API Standard 618 “Reciprocating Compressors for Petroleum, Chemical, and Gas Industry Services” covers moderate- to low-speed compressors in critical services. Integral compressors and low-speed, long stroke balanced-opposed compressors with speeds from 200 to 600 rpm generally fall into this type of construction. The use of this standard with highspeed packaged separable compressors generally results in pages of exceptions by the compressor packager.
API Specification IIP “Specification for Packaged Reciprocating Compressors for Oil and Gas Production Services” covers packaged high-speed separable compressors with speeds from 600 to 1,200 rpm. The majority of reciprocating compressors sold in today’s market fall into this category.
The user and facilitiy engineer must determine the critical nature of each installation and determine the type of construction desired. He or she must consider such things as intended service, compressor location, the consequences of downtime, and frequency of up-set or abnormal conditions.
When specifying compressor packages to API IIP, it may be necessary to specify certain sections of API 618 to ensure satisfactory installations, An example of this would be the supply of multiple compressors to be located in pipeline booster stations. In this case, an analog or digital pulsation and vibration study per API 618 Section 3.9 would be advisable to improve reliability and to minimize system problems and potential damage caused by gas pulsations and interaction between the individual compressor packages.