Tandem control of a gas pressure reduction station

In general, a typical pressure reduction control system is configured as two parallel flow streams each containing two pressure regulators connected in series. The main controlling elements used for the analysis presented in the paper are IGA axial flow regulators and the installations are usually referred to as pressure reduction stations (PRS´s). Initial investigations revealed the need for a better understanding of the operation and limitations of this particular regulator since, in certain circumstances, its behaviour was unpredictable. It was therefore decided that a mathematical model would be derived which emulated the regulator under all operational conditions, which would then enable the development of an appropriate microprocessor control system. Following this, a complete system specification could be derived leading to physical implementation. The paper presents the initial development of the model for the axial flow regulator, together with results obtained from a preliminary validation exercise. In addition, the paper describes the development of a control system which will enable tandem operation throughout the PRS´s operational envelope