Natural gas compressor failure investigation

Integrity and remaining life assessment of over 1400 electrical assets for PDO Gas, North Oil Directorate and South Oil Directorate



Start date: 2013


During the commissioning of a gas plant extension project, a reciprocating compressor failed catastrophically causing a small hydrocarbon release. The unit was rebuilt but failed again on commissioning. At this point, a Root Cause Analysis (RCA) team was assembled and RINA was awarded the role as a third party independent expert to assist in the investigation.
The repeated failure of the compressor held up the successful commissioning of the plant. The delay of the commissioning of the plant meant that the only safe alternative was to flare the gas. This has disadvantages both to the environment and the profitability of the plant. Re-instatement of the compressor and the successful commissioning and operation of the plant was critical to enable operations to recommence and minimise fines and other financial losses.


Members of our forensics team conducted a site visit to obtain evidence and interview personnel. Relevant components and information was then sent us for investigation and analysis. The work undertaken onsite allowed us to highlight a number of issues that contributed to the repeated failure of the compressor. The RCA team reviewed all of the investigation results and came up with several solutions for the client to choose from.

The recommended course of action, agreed by all parties, was to change the operating mode of the compressor and to modify the process resulting in the safe operation of the compressor. We made a number of other recommendations to ensure that the package would remain reliable in the future:

Manufacture of the piston – our metallurgical specialists reviewed the material composition and formation of the high stressed areas of the compressor pistons
Assembly of the compressor – we analysed the assembly reports for the second build of the compressor to ensure that checks had been carried out to help confirm that thecompressor was built adequately

Design of the package – our rotating equipment specialists reviewed the suitability of the design of the package for the intended service maximum value for money

Operating conditions and start-up procedure – our rotating equipment engineers analysed the operating data and procedures to investigate the possibility of liquidingestion into the compressor.


The compressor was designed to boost low-pressure gas, with a flow rate of up to 20 million scf/day. Forensic examination of the components showed that excess pressure had been applied onto the face of the compressor piston. Finite Element Analysis showed that the piston should have been capable of withstanding normal operating pressures. A review of the process drawings showed that, under certain conditions, the compressor could experience high-pressure spikes.