Every reciprocating compressor transmits pulsations into the piping system. These pulsations my or my not result in problems such a high vibrations, poor performance, or measurement error. Given that pulsations are inherent in reciprocating compressor installations there are basically two approaches from and 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 ad vibration problems. At start-up try to fix ay problems that occur.
Have a acoustical/mechanical study performed ad implement the necessary modifications prior to fabricating the package.
This paper discusses the benefits of performing a acoustical/ mechanical study on and 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 ad 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 a 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 ad indirectly have a adverse effect on the piping system. Some of the concerns, all of which have associated cost, are:
Lower volumetric efficiency leading to decrease incapacity.
Higher valve losses resulting in increased brakehorse-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 ad excited torsional shaft vibrations, which my lead to possible failure.
Acoustical response coincident with torque mechanical natural frequency, which my 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 ad failed parts or downtime (lost revenue) and increased fuel consumption of the compressor unit.