Does frame vibration offer effective and reliable protection for reciprocating compressors?
For decades, reciprocating compressor monitoring was not a high priority; centrifugal machines were always the focus of operators and monitoring equipment investments. The reasons for this are partially based on the high number of centrifugal compressors, in comparison to reciprocating compressors, found in refineries, natural gas or other petrochemical applications. Secondly, operators simply did not fear severe damages due to the low kinetic energy of these comparably slow running machines.
However, reality shows that reciprocating compressors have a reputation as bad actors among the rotating equipment fleet; showing the highest number of damages while simultaneously being process critical. Although this is a dangerous combination, insufficient protection and condition monitoring principles are still being applied on reciprocating machinery.
Operators, engineering procurement contractors (EPC) and original equipment manufacturers (OEM) have always followed the existing, applicable guidelines and standards during the final engineering stage. These standards were valid at the time of construction, and are generally still valid today. Upon reviewing the age of the reciprocating compressor population, it is clear that many of these large, critical machines have never been replaced, remaining in operation since their Initial start up date many decades ago.
Even after numerous catastrophic reciprocating compressor failures, there is still inadequate machinery protection on many of these machines: looking back into the history of applicable standards can help clarify the reasons why.
API standards
The American Petroleum Institute (API) has always been one of the leading organisations in compiling information about available and proven monitoring technologies for critical machinery. This information has been transformed into standards that have become widely used as the guiding
document for operators. It is remarkable that the first revision of the widely known API Standard 670 was originally released in 1976. The standard focused on the application of proximity sensor based machinery monitoring and was named: ‘Noncontacting vibration and axial position monitoring system’. The second revision of the same standard was released in 1986.
As a consequence of evolving vibration monitoring technology, API followed up with a parallel standard covering vibration technology. In 1981, the institute released API 678, named: ‘Accelerometer-based vibration monitoring system (1st edition)’. The 3rd revision of API 670, released in 1993 was more than an extension and update of the previous API 670. It
incorporated and replaced the API 678 standard, which focussed on accelerometer based monitoring. To better reflect its safety relevant character, the API 670 was renamed ‘Machinery protection systems’ for its 4th edition, released 2000 and still valid today.
