Problem Statement

A thick black hydrocarbon formation was found on centrifugal gas compressors’ discharge end wall and in the downstream discharge isolation valves that were installed in one of Saudi Aramco’s gas-oil separation plants (GOSPs) shortly after the plant commissioning. This phenomenon instigated a thorough process and material compatibility investigation. The mechanical part of this paper explores the reasons behind the compressors’ end wall and discharge isolation valves’ O-rings failure despite the fact that these were made of a material designed to withstand higher than actual and design discharge temperatures. The process section looks at sources of the residue formation at the compressor’s discharge, in particular, the compressor’s suction knock out drums demisters pad design.

Background

The problem was encountered in a gas-oil separation plant (GOSP) that compresses associated gas to a discharge pressure of 450 psig and an operating temperature that can reach 340 °F during the summer season. Thick black liquid was observed leaking from the barrel of the discharge end flange of two high-pressure (HP) gas compressors about a year after the plant commissioning.

The liquid was also observed at the compressor’s balance line (discharge end) on both compressors. A third compressor that operates at a lower discharge pressure and temperature, 105 psig and a maximum temperature of 300 °F, did not develop any symptoms of leaks in spite of operating under sour conditions. After nearly two years of operations, one of the HP gas compressors was dismantled and overhauled to investigate the source of the problem.

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