Every reciprocating compressor transmits pulsations into the piping system. These pulsations may or may not result in problems such as high vibrations, poor performance, or measurement error. Given that pulsations are inherent in reciprocating compressor installations there are basically two approaches from a pulsation/vibration point of view to installing a reciprocating compressor package:

Design and build the package with very little conscience consideration given to potential pulsation and vibration problems. At start-up try to fix any problems that occur.

Have an acoustical/mechanical study performed and implement the necessary modifications prior to fabricating the package.

This paper discusses the benefits of performing an acoustical/mechanical study on a reciprocating compressor installation. Recently such a study was completed between Arkansas Western Gas Company (Owner), PAMCO (Equipment packager) and Beta Machinery Analysis Ltd. (Engineering company who performed the study). Predicted As Found versus Final Modification pulsations and unbalanced forces are presented.

Pulsation control, whether it be via a simple volume bottle or a bottle designed with internals, is required for most reciprocating compressor installations. There are capital and operating costs associated with these pulsation control devises. Performing an acoustical analysis enables these devices to be designed to optimize the pulsation control, capital cost and operating cost (pressure drop) over the range of operating conditions expected during the life of the compressor. Excessive pulsations can directly effect compressor performance and indirectly have an adverse effect on the piping system. Some of the concerns, all of which have associated cost, are:

  • Lower volumetric efficiency leading to decrease in capacity.

  • Higher valve losses resulting in increased brake horse-power/MMSCFD.

  • Pulsation induced valve vibration leading to possible failures.

  • Increased rod loading sufficient to cause rod failures.

  • Pulsation induced cyclic rod loading transmitted to the compressor crankshaft as dynamic torque and excited torsional shaft vibrations, which may lead to possible failure.

  • Acoustical response coincident with torque mechanical natural frequency, which may cause rod failure and possible crankshaft failure.

Uncontrolled pulsation will, in the long run, cost money. This will be spent in the repair of worn and failed parts or downtime (lost revenue) and increased fuel consumption of the compressor unit.

You can access this article if you purchase or spend a download.