API 618 Analysis

Reciprocating compressor Pulsation & Vibration Analyses


For more information about API 618, click here


Acoustical and Mechanical Response Analyses in Accordance with API 618

Pressure pulsations are generated by the reciprocating action of the compressor piston and are amplified or weakened by the acoustic response of the piping system. Pressure pulsations produce oscillating forces called unbalanced forces. These forces, applied to a more-or-less flexible piping system, generate vibrations that can cause fatigue failures when the cyclic stresses are too great.

Other problems are also linked to pulsation, such as compressor performance, imprecision of flow metering, and behaviour of non-return valves and safety valves.


Pulsation Analysis

In the acoustic study, pressure pulsations and unbalanced forces are controlled by the following techniques:

  • Acoustic filter such as empty or baffled pulsation dampeners
  • Frequency separation by optimising section and/or length of pipework
  • Adding restrictive elements such as a restriction orifices

In accordance with API 618, the acoustic study reports:

  • Pressure pulsations
  • Acoustical unbalanced forces
  • Flow pressure drops
  • Horsepower and capacity deviation


Mechanical Response Analysis

A mechanical response study is used to optimise vibration and cyclic stresses by improving the design of the pipework supports and vessel supports.

In accordance with API 618, the mechanical response study reports:

  • The mechanical natural frequencies
  • The vibration and cyclic stresses on forced response

The Company and our Tools

We have been working in the pulsation and reciprocating compressor analysis field since the late 1970s.

The company “BOËT Stopson”, specializing in the fabrication and installation of industrial soundproofing equipment, outsourced its Simulation in 1996 thus creating its subsidiary “SIM Engineering”.

The pulsation and mechanical response studies of reciprocating compressor systems are carried out in accordance with the most recent edition of the API 618.

Our acoustic modelling and calculation tools have always been developed in-house by our Simulation department. We used an analog simulator until the late 1990s before switching to digital calculation methods. For mechanical studies we use AutoPIPE® Advanced, which is software developed by the Bentley company



The Analog simulator in the late 1970’s