A multiple-stage compressor train which is part of an off-shore booster installation was facing process and mechanical related problems. The frequency of these problems has increased lately leading to frequent trips and shut downs. These interruptions affect the operation of the plant and resulted in a loss in production and and a subsequent loss of revenue to the company.
The platform contains two similar compressor trains consisting of a four-stage compressor with a gas turbine driver. Each train is fitted with an integrated turbine compressor control panel. Thus, a detailed dynamic pipeline system simulation of the subject compressor trains was performed in order to provide a series of recommendations that would improve the safe operation and increase the reliability of the compression systems.
A detailed dynamic model of the multi-stage compression system was built for each train. These models included compressor performance maps, gas compositions for each stage and train, piping yard, recycle, isolation, check and blowdown valves, scrubbers, separators, and coolers. Several simulation cases were conducted for both the platform systems. These cases evaluated the effect of the delay and travel times of the existing anti-surge valves, delay of the coast down action, failure of the non-return valves (NRVs), action of a blowdown valve on the emergency shutdown (ESD) sequences, recycle valve bypasses, check valve arrays, and process upset conditions.
The results of this analysis provide recommendations in solving some of the existing issues and creating more understanding of the dynamics of the system. It was found that any proposed recommendations or changes in the sequence or timing of one stage would affect the surrounding stages, since they are not only connected through the piping but also driven by the same gas turbine shaft. Therefore, a very comprehensive analysis was conducted for each train to provide recommendations that would be feasible for implementation while reducing the constant risk of mechanical failure and surge events. Thus, results of the analysis and some of the recommendations obtained are presented in this paper.