Spillback control on compressor return line

[koba78]

Dear members:

A gas feed by varying the compressor discharge pressure by
spillback control on compressor.

The flow from compressor discharge drum
is measured by FT and temperature and pressure compensation (on Train 1 & Train 2 line)

If the pressure is rising, too much gas is being delivered.Flows greater than setpoint will open the spillback valve to increase the spillback flow(Is it bypass control mode?).

The discharge pressure is allowed to rise and fall between set pressure boundaries.

My question is:
Is it necessary to set up a FT-B located on the discharge line of the drum or another location such as,the inlet line of the drum (FT-A) to control the spillback valve on the minimum flow return line(Minimum flow seems only occurs in centrifugal compressor?)

Or setting up FT-A or FT-B are all redundant cause already
got FT on the train 1 & 2 line and these FT will also send signal to spillback control valve to control the return flow?

Hope any professional members can kindly help me out.

Thank you.

 

[KiwiMace]

The hot gas bypass would typically be controlled with a mechanical diaphragm pressure regulating valve.

 

[knapee]

usually reciprocating compressor with capacity control is initiated by pressure sensors on the discharge gas line from the compressor.
It the pressure is rising, means too much gas is being delivered and too little if the pressure is falling. The control can alternatively be applied from suction pressure variations.