Compressor Surge Precursors

[neo]

How do you identify compressor surge precursors before the control system reacts?

[tiror]

Before full surge, compressor flow often becomes unstable like small rapid fluctuations in suction flow, hunting around the recycle valve position, oscillating differential pressure, and pulsation-like trends.
The compressor may enter mild surge, incipient surge, rotating stall before deep surge happens.
A good operator watches for repetitive flow trends, unstable recycle valve movement, fast oscillations not previously present.

This often appears before the antisurge controller fully opens.

[ivani1]

If the antisurge valve repeatedly opens/closes in small cycles, starts chattering, cannot stabilize flow then the machine is often operating near surge margin.
This indicates controller struggling to maintain stable operating point, compressor map instability, insufficient surge margin.
And this is especially important during low throughput, startup, rundown, and compressor parallel operation.

[tuan]

One of the earliest signs is instability in compressor flow.
Instead of a smooth trend, operators may observe:
Small cyclic fluctuations in flow
Rapid changes in flow measurement
Difficulty maintaining a constant operating point
Even though the average flow may appear acceptable, the compressor may already be operating very close to its stability limit.
It is better to focus on:
Oscillating flow transmitter readings
Increasing flow variability
Short-term fluctuations not seen during normal operation