An oil and gas company was facing process and mechanical related problems on the multiple-stage compressor trains at two important booster installations. The frequency of these problems has increased lately, and this has led to frequent trips and shut downs. These interruptions affect the operation of the plant leading to a loss in production and consequences of lost revenue for the company. The two platforms each contain one compressor train comprising 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. The analysis included a review of the existing compression systems including all the equipment and hardware related with the compression anti-surge system. In addition, a site visit was performed to review and understand the existing anti-sure control system at each facility. 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 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. In addition, parametric studies were conducted for each of the most important parameters of the system to quantify their effect of any possible modification.
The results of this analysis provide recommendations to solve some of the existing issues while understanding more of the dynamics of the system. It was found that any propose recommendation or change in the sequence or timing of one stage will affect the surrounding stages since they are not only connected through the piping as they are 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.