This tutorial presentation will build on the introductory pulsation topics by expanding the basic theory into advanced topics in gas piping systems. Topics in this tutorial will address complex problems that many operators face today including: wet gas compression and pulsation bottle design, the impact of changing gas compositions for reverse direction flow on pulsations and horsepower requirements, adding pulsation control for integral (Enbloc) compressors, and mixed compression with different unit types sharing a common header. Each topic will be presented with an overview of the subject, case studies and mitigation techniques or analysis methodologies. In addition, an overview of the latest research and development for novel pulsation attenuation methods will be presented as well as the level of technology development for each concept.
Pulsations in piping systems can be generated by reciprocating compressors, centrifugal compressors, flow-induced vortex-shedding, pressure reducing valves, or turbulent flow. Of these sources, reciprocating compressors and flow-induced vortex-shedding produce the majority of pulsations that cause noise and vibration problems in pipelines. This paper will focus primarily on pulsations created in a gas piping system by positive displacement compressors.
Pulsation is a periodic fluctuation in local pressure imposed on the fluid in a piping system by a machine or occurring locally as a result of a flow disturbance phenomenon. The Bernoulli principle describes that a variation in pressure will produce a corresponding variation in velocity (see Equation 1 for a simplified form). While the Bernoulli principle is rarely used in calculating pulsation amplitudes in piping systems, it is an important relation to understand when solving flow related problems. Figure 1 gives a visual example of the molecular redistribution of molecules imposed on a gas by a reciprocating compressor to create a pressure wave that travels through a piping system.
