What causes a surge in a gas compressor?
Surge is a condition that occurs in compressors when the amount of gas they are trying to compress is insufficient for the size of the compressor and the blades lose their ability to transfer energy from the shaft to the fluid, causing a reverse flow of the gas.
When to use an anti surge valve in a compressor?
This condition can have catastrophic effects on the machine, so compressor manufacturers include anti-surge valves that recycle gas from the discharge to the suction when a low flow is detected. Usually compressors are designed such that these valves are only open on startup or under reduced rates.
What’s the difference between surge and stall in a compressor?
In the words of compressor expert Ivor Day, stall is a disturbance of compressor flow in the tangential direction, while surge is a disturbance in the axial direction.
How does surge detection work on a centrifugal compressor?
When a compressor is surging, the system only needs to detect this condition and keep opening the antisurge valve in steps until the compressor stops surging. It’s a discrete, open-loop response that is called Surge Detection and the speed requirements for that function is covered by API Standard 670, 5 th edition.