A key function for a control system in a gas turbine train is to keep the operation of all components within a range of parameters that keep the unit safe. If the operating parameters of components fall outside the desired range for safe operation, the control system will detect these and create an alarm. For critical parameters, the control system may initiate an alarm and a shutdown of the unit. In many instances, an alarm may precede the shutdown command.
Frequent discussions evolve around situations that lead to a shutdown of the train, as shutdowns impact the availability of the turbomachinery equipment, but in a wider sense also the availability of the compressor station. Therefore, shutdowns impact the profitability of a system. On the other hand, shutdowns may prevent significant, costly damage to the equipment, with significant downtime, and financial implications.
In this lecture, we will discuss different methodologies for shutdown requirements, in the effort to maximize availability of units. Particular emphasis will be given to aging machines as well as machines where the instrumentation, and the control algorithms may no longer be state of the art, or where unnecessary or spurious shutdowns plague an installation.