SIROGAS is a computer programme for the simulation of steady state and transient behaviour of gas flowing in a complex network which may include a wide range of the hydraulic devices normally found in industrial flow networks. These include high pressure natural gas transmission networks. This paper describes a model of a 2 unit compressor station recently added to SIROGAS. The model includes all control modes and allows starting and stopping of either unit or the entire station. Comparison is made with measured data from an operating station, and a demonstration calculation is discussed in which several mode changes occur, including unit and station shutdown and startup.


In recent years, computer modelling of pipeline networks in high cost plant has become an increasingly important tool for the optimisation of their design and operation. CSIRO is working with the Pipelines Authority of South Australia and The Pipeline Authority of the Australian Government to develop improved methods of natural gas pipeline networks. This has resulted in the SIROGAS computer programme (Turner, Bakker and Severs 1982; Turner and Rainbow 1983) for modelling the steady state and transient behaviour of natural gas in pipeline networks. Co-operation with The Pipeline Authority (an agency of the Australian Government) has resulted in a highly interactive, user friendly programme which enables a gas engineer to carry out rapidly analysis on all or part of the network of interest. The programme is used regularly by two large Australian gas transmission organisations for analyses required for operation, such as pipeline break studies, and planning. Selection of a license for worldwide marketing is in progress. Application to two-phase flow problems in the oil and gas industry is being investigated. In Australia, gas pipeline networks transport natural gas over the long distances between sources and markets. In the early life of such networks compressor stations within the network may not be required, but to get the best return on the capital invested in the pipeline, compressor stations are eventually installed. Up to 5 per cent of gas transported in such pipelines may be burnt to drive the compressors which raise gas pressure and density, hence reducing gas speed and increasing the rate at which gas can be transported through the network. The choice of compressors and their operating speed is a complex matter usually involving a computer model of the pipeline network. The first priority is to meet the needs of the market, the second to optimise the operation of the network. Limits on pipeline pressures and compressor operation must be observed, and gas must be supplied to customers according to contracts which often specify pressure limits. Currently available software packages use steady state models of the network and compressors. However, natural gas transmission networks are rarely operated in steady state; demands for gas vary in daily, weekly, and annual cycles. In this paper, a realistic transient model of a compressor station is given which is intended for use in such optimisation studies.

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