Traditionally, pipeline transmission systems have been designed using steady state simulations. Steady state simulations are sufficient for optimizing a pipeline when supply/demand scenarios are relatively stable. In the case of a gas pipeline, it is also important that flows in and out of storage are not highly variable. In general, steady state simulations will provide the designer with a reasonable level of confidence when the system is not subject to radical changes in mass flow rates or operating conditions.

However, situations do arise which require more than a conventional analysis such as large load factors, surges in mass flow rates, the loss of facilities and facility operation (e.g. pigging procedures). In these and other instances, the designer will want to perform a dynamic (or transient) analysis to test the capability of the system, choose the system components and maintain the appropriate level of safety.

This paper will illustrate the importance of transient simulations when designing transmission systems subject to aggressive conditions. Example scenarios, taken from current major projects, are used to depict a diverse range of dynamic problems. The examples help identify the need for a transient analysis and exemplify the downfalls in a system when the analysis is not employed during the optimization and design process.

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