A question regarding sequential control configuration
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I am currently developing a sequence control program, and I would like to ask about the control of control valves. At a certain stage, it is necessary to force the control valve to close, while at another stage it needs to be set to an automatically regulated position. There is also a minimum limit required – for example, the minimum opening degree can only be 20%; below that level, automatic regulation is not possible. What I know is that the control valve adjusts its opening degree based on signals such as temperature and pressure; at this point it is in AUTO mode, and manual adjustments to the opening degree are not accepted. It is possible for the sequential control program to send a signal to force the valve to close, but is it feasible to have it return to AUTO mode automatically afterward?
This post was last edited by yuyongyao1983 on 2011-12-1 17:10. The person above – the sequence control programs vary from one manufacturer to another, and the ways in which they are implemented also differ. Do you mean the CL programs of HONEYWELL TPS when you talk about programming? What you’re talking about is definitely achievable; it’s just that different companies use different methods to do it. If it is CL, please refer to the following method: Set the output limit at 20% in the PID configuration. In the sequence control program, use the following instructions (test after implementing them): STEP SET tagname.MODATTR=PROGRAM **** Change the PID module’s control mode to program control SET tagname.MODE=man **** Switch the PID to manual control via the sequence control program SET tagname.OP=0 **** Set the PID’s manual output to 0 (take into account FC/FO values for valve opening). wait 3 secs SET tagname.MODE=AUTO **** Switch the PID back to automatic control via the program SET tagname.MODATTR=OPERATOR **** Change the PID module’s control mode from program control back to operator control
Could you explain why the code needs to be controlled in this way?
This is a feature of CL. Changing the settings of its RC parameters can meet the original poster’s requirements.