Reliability Evaluation of Compressor Systems Based on Universal Generating Function Method

At present, universal generating function (UGF) is a reliability evaluation technique which holds the bare-looking and easily program-realized merits in multi-state system. Thus, it is meaningful to apply this method to an actual industry system. Compressor systems in natural gas pipelines are series-parallel multi-state systems, where the compressor units in each compressor station work in a parallel way and these pressure-boosting stations in the pipeline are series connected. Considering the characteristic of gas pipelines, this paper develops two different UGFs to evaluate the system reliability. One (Model 1) establishes a system model from every compressor unit while the other (Model 2) considers the whole system as a combination of multi-state components. Besides, all the parameters of “weight” in UGFs are obtained from thermal-hydraulic models based on the actual engineering and “probability” from Monte Carlo simulation. The results show that the system reliabilities calculated by different UGFs are approximately equal. In addition, the demand of gas and the gas pipeline transportation system show a reverse trend. Because the number of parameters needed in Model 2 is far less than that needed in Model 1, Model 2 is simpler programming and faster solved.