Compressor API 618 Studies

DRG conducts pulsation studies according to API 618 5th ed. DA3.

The analysis path from DRG features for 4 steps, which are required depends on whether it is an existing plant or a new build and whether the static piping design is also required.


Step 1: Acoustical Analysis

The acoustical analysis is performed using our commercially available software BOSpulse using the time domain solver. This step, which conforms with step M3 of API 618, checks if the pulsation amplitudes arising due to the excitation of acoustical resonance frequencies in the piping system are acceptable.


For a new build system the pulsation dampener can also sized, for which the pulsations between the dampener and the compressor, and the dampener pressure drop will be evaluated. If necessary a pre-study according to M2 of API 618 can be performed in advance of the piping design.


Step 2: Static Stress Analysis

If required a piping flexibility study can be done for the piping design (often this will be performed by another party prior to the pulsation study). This analysis will ensure that the loads on the equipments and flanges are within acceptable limits for static loads.


Step 3: Mechanical Analysis

Here two approaches are possible depending on the compressor and the preference of the client.


1) The piping is subject to a shaking force due to due to the fluctuating difference in pressure caused by a pulsation between an elbow pair. The magnitude of the shaking forces arising in the piping and compressor are checked for conformance according to API 618 M6. To ensure that large shaking forces do not overlap with a mechanical resonance mode, separation between the mechanical and acoustical resonance frequencies is checked according to API 618 M5.


2) A forced mechanical response according to API 618 M7 or M8 to determine how much the shaking forces excite the mechanical resonance modes. The stresses and displacements arising due to the excitation of mechanical resonance modes are assessed.