Process Description
The process gas to be compressed enters the suction of the first stage of the reciprocating compressor through a suction pressure control valve. The make-up process gas is mixed with the kickback flow before passing through the inlet cooler.
The process gas leaving the first stage of the compressor passes through an inter cooler before being compressed by the second stage of the compressor.
The compressed process gas is then drawn off by users from the discharge of the second stage. Excess gas may either by sent back to the suction of the first stage through the discharge pressure control valve, or may be vented.
Instrumentation
Stage 1 suction pressure is controlled by PIC-101. Upstream process gas temperature and pressure are indicated by TI-100 and PI-100 respectively. Makeup gas flow is indicated by FI-100.
The mix temperature of the makeup gas and the kickback gas is indicated by TI-101. Suction temperature to the first stage is controlled by TIC-102.
The discharge temperature and pressure of stage 1 is indicated by TI-103 and PI-102 respectively. The flow through stage 1 is indicated by FI-101.
The suction temperature of stage 2 is controlled by TIC-104. The discharge temperature of stage 2 is indicated by TI-105 and the flow through stage 2 is indicated by FI-102.
The gas demand is controlled by FIC-105 and the pressure of the downstream process is indicated by PI-105.
Discharge pressure of the second stage is controlled by the kickback controller PIC-103 and the kickback flow is indicated by FI-103. Discharge pressure may also by controlled by the vent controller PIC-104. Vent flow is indicated by FI-104.
Compressor speed is controlled by SIC-100. The compressor may be started and stopped with switch HS-100. The horsepower consumed by the motor is indicated by HP-100.