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BP owns and operates the Milne Point oil production facility on Alaska’s North Slope. Processing facilities are enclosed in heated, adjoining modules. The gas compression module houses two 3,450 HP electric motor driven reciprocating compressors. Over time, the frequency and severity of compressor component failures have increased significantly. An intensive discovery effort identified both mechanical and process-related causes of failure, including entrainment of water and natural gas liquids (NGL) in the compressor suction. Damage caused or exacerbated by ingested liquids includes bearing failures, damaged cylinder lining, sheared wrist pins, sheared cylinder attachment bolts, and cracked pistons. The main focus of this paper will discuss the discovery and analysis, leading to better control of liquids in the process. Poor separation performance of existing suction scrubbers was predicted by computational fluid dynamics (CFD) modeling and confirmed by laser isokinetic probe sampling to quantify liquid entrainment. Analysis of operating data also indicated condensation of liquids in suction piping downstream of the scrubbers. Solubility of NGL in compressor lube oil was also determined to be a contributing factor to compressor damage, especially cracked pistons due to interstage slugging of diluted lube oil. NGL solubility issues became even more severe with a change from synthetic lube oil to mineral oil. Lab analysis confirmed significantly higher solubility of NGL in mineral oil compared to synthetic oil. A multi-faceted solution was required, including 1) reconfiguration of suction cooler temperature control logic, 2) upgrades to suction scrubber level control, alarm and shutdown systems, 3) installation of inline, axial flow cyclonic demisters immediately upstream of compressor suction bottles, and 4) heat tracing and insulation of piping and suction pulsation bottles downstream of the new demisters. Several other options were considered but rejected for vario
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List Price $195.00