Union Gas, like many of the natural gas companies across Canada, has seen significant expansion of it’s compression and pipeline facilities in the past few years. Much of this expansion has been dedicated to the gas storage and transmission needs of the Eastern Canadian and American markets. With the capital costs of these facilities continually on the rise it is critical to ensure that each facility will yield maximum utility to the system for the proposed investment.

Union Gas has a unique position within the Canadian gas industry as not only a major distribution company but also an operator of over 120 BCF of underground gas storage and a transmission pipeline system which is an integral part of the transCanadian gas supply infrastructure. Union’s transmission and storage system provides a vital link between the TransCanada PipeLines transmission system running through Northern Ontario and Central Michigan and several delivery points into the Northeastern United States and Eastern Canada. The diverse nature of Union’s operating facilities dictate a system with two distinctively different modes of compression during the winter operating season. These modes being storage withdrawal, which is typically a high head low flow operation and pipeline transmission which is a low head high flow operation. Each of these modes require specific compressor performance designs which do not typically display the flexibility to be utilized in either mode.

With system demands consistently on the increase it can be very difficult to maintain adequate backup in the event of a compressor plant outage; this is particularly evident’ when considering the different operating requirements at various locations in the system. In an effort to maximize the operational flexibility of a new facility, Union Gas has implemented a new design consisting of a triple case compressor train driven off a single engine gas turbine package. With the external unit piping configured for both series and parallel operation this new design can effectively duplicate all possible modes of operation in Union’s present operating system, for both storage withdrawal and pipeline transmission.

This paper will discuss the extent of operational flexibility this system can offer and the various design concerns associated with this type of compression plant facility.

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