18-10-2010, 04:50 PM
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Compressor Anti-Surge Control Application Introduction
Surges occur when the compressor outlet pressure is too high in relation to the flow through the compressor. The flow can change rapidly when there is a sudden change in the load that the compressor is expected to deliver. If the surge is not controlled, the compressor can be destroyed. An anti-surge control strategy is designed to protect a compressor from these surges. The typical methods for accomplishing surge control are either a blow-off to atmosphere or recirculation from the outlet to the inlet of the compressor. The anti-surge control strategy is tightly integrated with the compressor load control strategy. Installation Details The application comprised a 3.2 MW compressor supplying air to an air separation plant. The air from the compressor was passed through a molecular sieve into a column (coldbox) in a fairly steady flow (approx. 90,000 Nm3/h). The hardware that was used for this application comprised standard DeltaV I/O (analog and digital) connected to standard Rosemount transmitters (non-HART). A DeltaV M3 controller was used for the load control and antisurge control. The compressor was a multi-stage "turbo". The incoming air was compressed in the first stage and then passed through a heat exchanger to be cooled off before being injected into the second stage.
