The Logic Behind The Magic. “1st Stage Compressor Suction Scrubber"

The purpose of suction scrubber is to remove liquid prior to feeding gas into the 1st Stage compressor. Collected liquid is routed to HP flare KO drum, The liquid level in the scrubber is controlled using GAP control by opening/ closing the liquid outlet control valve

  

 Control Loop Description

Level Controller
Level Control is performed via LIC using a GAP control by opening/closing the level control valve LV between On and Off levels. When in auto mode, the controller shall operate the valve at two position only, i.e. fully open or fully closed. When in manual mode, the operator shall be able to enter any required valve position.

Pressure Indicating Controller
Signal PT from inlet compressor suction scrubber is sent to the master controller in the compressor UCP to regulate the turbine speed. The controller is also regulate the suction pressure during start-up via pressure control valve. During normal operation, the pressure control valve shall be fully open and as such set point of PIC shall be higher than set-point of the pressure controller inside the compressor UCP.

The control valve is fail open type. The pressure controller output signal shall be reverse acting and the control valve OPDIR is reverse.  As the pressure falls below the set point. the controller shall open the control valve to increase the pressure