API 618 and Pulsation Studies

Pulsation analysis is the study and control of acoustic resonances in gas pipe systems caused by strong harmonic forcing from reciprocating gas compressors. When the frequency of these acoustic resonances coincides with mechanical resonances in the attached pipework, there can be excessive vibration and fatigue failure. In addition the acoustic resonances can reduce the efficiency of compressors and increase the wear-rate of their valves.

The majority of pulsation studies carried out worldwide follow the requirements detailed in API Standard 618: Reciprocating Compressors for Petroleum, Chemical and Gas Industry Services. The standard includes criteria for pulsation dampener performance, pulsation levels in pipework and at the cylinder flange, pulsation induced shaking forces and resulting pipework vibration and stress levels.

Pulsation analysis is used as a design tool, especially for new process gas compressors purchased to API 618. In some cases existing compressor systems also need re-evaluating when gas conditions change significantly or if the pipework is significantly altered. Pulsation analysis is also used for dampener design or as part of the trouble shooting process where pipe failure has arisen and system modifications are required.

Spectrum Fluid Dynamics is a world leader in the provision of pulsation analysis, for which we use our own well-established PIPAC® acoustic analysis software. Mechanical analysis of compressors, their pipework, and support structures is carried out using ANSYS finite element software. Over the last 25 years, simulations and site measurements have been undertaken for all the world’s main compressor manufacturers, and many of the leading engineering contractors and oil companies – a total of over 550 studies. Spectrum carry out site troubleshooting services worldwide.

Projects undertaken include:

  • Shell Pohokura Gas Field, New Zealand, for Howden Thomassen Compressors
  • Lukoil Neftochim Refinery, Bulgaria, for Dresser Rand UK
  • Exxon Mobil Singapore Refinery, for Burckhardt Compression AG
  • KPI fertilizer plant, Indonesia, for Mikuni Engineering
  • Repsol Cartegena refinery, Spain, for ABC Compressors
  • Air Liquide H2/CO Plant, Dormagen, Germany, for LMF Compressors
  • Solutia, Newport Plant, Newport, UK, for SIAD Macchine Impianti
  • Troubleshooting at Reliance Jamnagar Refinery, India, for Howden Thomassen Compressors