Surge Prevention Control

The primary function of S&C’s Surge Prevention Controller Application (SPCA) is to control gas flow through a compressor to prevent surge, avoiding potential equipment damage and process upsets. When the program detects that the compressor operating point is approaching surge conditions, the application opens and throttles the surge control valve to recycle (or vent) the downstream gas, preventing the compressor from experiencing surge.

SPCA uses advanced techniques to accurately determine how close the compressor is operating to the surge limit. That distance is a function of the compression ratio, flow measurement, and compressor speed as well as the gas composition, pressure, and temperature. The application uses a variety of algorithms to determine how the surge limit changes as the process conditions change.

Opening and closing the surge control valve at the optimal time, rate, and amount is a delicate balance and a complex function. If the valve is opened too liberally, surge is avoided, but power is needlessly wasted. Conversely, if the control is too conservative, power may be conserved, but surge may also occur. SPCA incorporates two levels of PID control (Surge Control and Enhanced Surge Control) to act at exactly the right time and by the right amount for maximum operating envelope and reliable protection. Furthermore, in the event that a surge occurs due to a process upset, the program automatically increases the safety margin to prevent a second event and sends an alarm to notify operators.

SPCA can be calibrated according to the manufacturer’s specifications and compressor maps or through field testing to determine true installed compressor performance and surge characteristics. SPCA simplifies calibration for the field engineers by recording surge events and conditions and by automatically defining parameters. A dynamic compressor performance map with the operating point and surge defense lines can be displayed on the local panel and on the DCS screen. Like all of S&C’s turbomachinery solutions, SPCA can operate on all leading hardware and software control platforms.