PID control
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What do ZSTC and ZSTO stand for in the picture?
Personally, I think it's the valve position opening and associated lock feedback. Your valve is associated with interlock point 102/104
Thank you for your answers. What is the reason for these two alarms? There is no interlocking. ZSTC -10401 Discrete input monitor with alarm
TV10401 seems to be a regulating valve, but in the drawing it should be an on-off valve. ZSTC/O is the valve open or closed position feedback. The reason why you are alarming is that the DCS does not detect the open or closed position of the valve. So call the police. Normally, it should be that the valve is either in the open or closed position. reason: 1. Maybe your valve position switch is damaged or the position is misaligned, and the proximity switch does not sense the position signal. 2. The valve is stuck and is really not in the fully closed or fully open position.
This is normally the temperature regulating valve. When 102 and 104 interlock operates, the positioner output will be cut off through the solenoid valve. The regulating valve will be fully open. The alarm message cannot be clearly seen. It should be an interlocking action but the valve position response is wrong.
The alarm on DCS depends on how it is done in DCS. After interlocking TV valve FO on pid, you need to see the open signal ZSTO. ZSTC on DCS depends on how it is done. The alarm is of little significance and there is no requirement on PID.
Thanks to the people above for their detailed answers. Basically, I have an understanding of this ZSTO/C alarm. There are almost no related answers on Baidu. It is difficult for those who are not instrument professionals to understand this. Thank you again for your enthusiastic answers!