Sheet 46
Field note, first posted on LinkedIn.
Anti-surge control, in plain words.
A centrifugal compressor needs a minimum flow. Below it the flow breaks down and reverses. That is surge.
How the control keeps it away:
- 1.Surge line. The left edge of the compressor map. Past it, the machine is unstable.
- 2.Control line. A margin to the right of the surge line. The controller acts here.
- 3.Operating point. Calculated live from suction flow, pressure, temperature and head.
- 4.Recycle valve. Opens at the control line and sends discharge gas back to suction, normally via a cooler.
- 5.Start and stop. Open on start, ramps closed once online, fully open on a stop or trip.
- 6.Surge detected. The valve holds a minimum position until the operator resets it.
What do you check first when you commission anti-surge? Valve stroke time, transmitter ranges, or the map?
