Spectrum Fluid Dynamics complete API 618 Design Approach 3 (5th Edition) Pulsation Study for large Howden Thomassen Reciprocating Compressor

14 June 2019 by Paul Scourfield, Director

Spectrum were pleased to be asked by Howden Thomassen Compressors (HTC) to undertake a full API 618 Design Approach 3 (5th Edition) Acoustic and Mechanical Pulsation Study for the SASREF Project, Saudi Arabia.

Although Spectrum have undertaken many API 618 pulsation studies for HTC, this one was marked out by the large size of the compressor, with 5 stages of compression and cylinder bores from 480mm to 1130mm.

API 618 Design Approach 3 studies are undertaken on reciprocating compressor installations to ensure that pressure pulsations generated by the opening and closing of the compressor valves do not translate into potentially damaging dynamic forces in the connected process piping.

Pulsation dampeners attenuate the basic pressure pulsation close to each cylinder, but natural acoustic resonances in the pipe system may also require detuning (e.g. with orifice plates or dimensional changes) to avoid coincidence with the dominant pulsation frequencies.

Finally, natural mechanical resonances of the piping must also be assessed, to avoid coincidence with both the pulsation excitation frequencies and natural acoustic resonances, in order to ensure vibration and stress levels in the piping are acceptable.

The studies use Spectrum’s own specialist software (PIPAC) to calculate the acoustic pressure pulsation levels and resulting dynamic forces throughout the system, and ANSYS Finite Element Software to assess the resulting vibration and stress levels in the piping.

For this project Spectrum recommended orifice plates to detune acoustic resonances in the piping and additional pipe supports to detune mechanical natural frequencies. Spectrum also worked with the engineering contractor to ensure that the stiffness of the pipe support structure was sufficient to provide the required dynamic restraint.