Surge Control In Compressors

Surge Control In Compressors

The design of compressor control systems is not complete without consideration of surge control, because it affects the stability of the machine.

Surging begins at the positively sloped section of the compressor curve. In Figure 1 this occurs at S1 on the 100% speed curve at 4400 lbm/hr (1980 kg/hr).

If the flow never drops below this limit, that will ensure safe operation for all speeds, but some power will be wasted at speeds below 100% because the surge limit decreases at reduced speed

Various schemes to control surge are outlined in the following 

• Compressor pressure rise ( ΔP = PD−PI) vs. Differential across suction flow meter ( h).
• Pressure ratio (PD/PI) vs. actual volumetric flow (Q)
• Break horsepower vs. mass flow (m)
• Pressure ratio (PD/PI) vs. Mach number squared
• Incipient surge
• Surge spike detection