Head-flange O-rings on Barrel Type Centrifugal Compressor Units at RasGas: Issues & Resolutions

Abstract

RasGas is operating many centrifugal compressors from different major OEM’s. Of an OEM product-line, twenty-four (24) centrifugal compressors with a total rated power of roughly ~ 900 Mega-watt are in operation, out of which 16 are barrel type (BCL). Driven by an end-cover or Head-Flange (HF) O-ring failure during early months of operation, indicated via gas leak in to atmosphere, a series of actions were taken due to serious uncertainties of the HF O-rings reliability, for both the units already in operations and the ones under Pre-Mechanical Completion. Actions included materials properties, tests data, selection (e.g. spliced versus single piece) and manufacturing processes and O-ring makers and supplier’s traceability. A comprehensive Risk Assessment led by Project Team and supported by EM experts was carried-out to determine whether HF O-rings already installed in similar unit shall be replaced right away prior to putting it in to full operation. Test schedule to accept or reject assembled HF at site was defined. Small modifications for continues monitoring of the HF O-rings during operation was also established. This Case Study is intended to share some lessons of technical aspects reviewed including selection processes. Site challenges to replace the HF O-rings for such barrel type centrifugal compressors and the site test schedule are also covered.