Abstract:

The flow rate of raw gas compressor fluctuated greatly, with a fluctuation of 10961.65 Nm³/h, and then the flow rate decreased from 51768.7 Nm³/h to 35768.94 Nm³/h. The compressor anti-surge valve was opened for unloading, resulting in shutdown of the whole unit. When the flow rate fluctuated, the working point on the right side of the anti-surge control line came back and forth 9 times with the same magnitude, the minimum flow rate was 40807.04 Nm³/h, the compressor speed fluctuation was 347.14 r/min, and the flow fluctuation caused by the fault of the unit itself was eliminated. When the flow rate fluctuated, the regulating valve PV2002 valve position and downstream pressure PSI2002 fluctuated synchronously. The valve position fluctuation of regulating valve reached 29.163%, resulting in fluctuations in compressor flow rate. The PID of regulating valve was modified 18 times, the P value was changed from 150 to 28, the system response slowed down, and the control output diverged. At the same time, the pressure of the incoming raw gas fluctuated significantly, leading to a greater fluctuation in the valve position of regulating valve and a greater fluctuation in the downstream flow rate. The PID of regulating valve was changed from automatic mode to manual mode, resulting in a further decrease in the flow rate. The working point came into the surge line, and the anti-surge valve was opened suddenly. The PID parameters of regulating valve were restored. The compressor speed control valve, anti-surge valve and regulating valve PV2002 were statically tested, and the requirements for management and technical measures were proposed. The changes in PID parameters of regulating valve, the fluctuations in raw gas pressure and the changes in state mode of regulating valve are the fundamental causes of compressor unloading and unit shutdown.

Key words:  ')">

 , compressor anti-surge valve, action, PID of regulating valve, modification, natural gas pressure, fluctuation