Centrifugal Compressors Flashcards
What is surge?
Surge is the occurrence of backflow of a gas in a centrifugal compressor
What’s bad about surge?
It can damage the compressor (overheating, damage bearings and cause rub)
Discharge check valve will slam shut (shaking pipe)
Cause process upset
What is the surge point?
The surge point is the point where flow rate is at its minimum
Indications of surge
Flow reversal
Discharge check valve slams shut
Drop in downstream discharge pressure
Forward flow resumes
Consequences of surge
- Flow reversal can be violent
- axial thrust on rotor can damage bearings or cause rub
- overheating of compressor
- cause process upset
Surge control observation
Vibration, noise, process upset (lack of supply)
What is stonewall/choke
Maximum flow at low pressure
Capacity control options
Speed variation (most efficient)
Suction throttling (2nd efficient)
Discharge throttling (3rd efficient)
Recycling (least efficient)
What is a centrifugal compressor
Increase gas pressure by increasing the velocity of gas molecules
Why does centrifugal pump need a live oil system?
Compressors easily overheat- lubrication is critical. The compressor, driver bearings and gearbox (if it has one) need lubrication.
Components of a lube oil system
Reservoir
Main pump/spare pump
Duplex filters and coolers
Temperature control loop
Pressure control loop
