How to control the change rate of DCS instrument setpoints (SV)
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I would like to ask the experts: In the Yokogawa DCS3000 system, to change the setpoint (SV) of 1FIC1130 from 100 KG/H to 200 KG/H, it takes 2 hours for this change to occur. The SV value rises gradually from 100 KG/H to 200 KG/H over a period of 2 hours, rather than jumping straight to 200 KG/H. I’ve heard that the VELLIM or FUNC-VAR function blocks can be used for this purpose, but I’m not sure how to connect these function blocks to 1FIC1130. Are there any other better methods? I would appreciate it if someone could provide a connection diagram; thank you very much!!
Is Yokogawa’s flow control that slow? It’s probably due to the requirements of the process
1FIC1130 control scheme? It is necessary to examine the original control scheme for 1FIC1130, as well as the process control requirements and constraints, in order to provide recommendations on how to connect it to 1FIC1130.
1FIC1130 is a PID instrument. The production requirement (setpoint) SV has been changed from 100 KG/H to 200 KG/H. After changing the setpoint from 100 to 200, the SV value rises gradually from 100 to 200 over a period of 2 hours (rising in a gradual manner), rather than changing suddenly from 100 KG/H to 200 KG/H. This approach is more conducive to maintaining production stability. I’ve heard that it’s possible to achieve this using the VELLIM or FUNC-VAR function blocks, but I’m not sure how to connect them to 1FIC1130. I hope everyone can offer some guidance! Or perhaps there are other better methods
I think the PID parameters can be adjusted, of course, as long as it is within the limits permitted by the process
With the VELLIM module, this is how we handle all our SV ramps. The OUT pin of the VELLIM module is connected to the SET terminal of the PID module. After installation, in the TUNING section of the VELLIM module, set the rates for SV increase and decrease respectively for DMVP and DMVM (pay attention to the setting of the time unit, i.e., the TU parameter)
Connect the OUT(MV) of the VELLIM module to the SET(SV) of the 1FIC1130 PID module in order to set the DMVP (Upward velocity limit value) and DMVM (Downward velocity limit value); other parameters can be set as needed. Set 1FIC1130 to CAS, set VELLIM to AUT/MAN, and adjust the SV of the VELLIM module.
It’s not necessary to use a connection module; you can set up the line chart in FUNC-VAR and then write a CALCU routine to assign the CPV value from FUNC-VAR to SV
The SV value changes automatically; this should be referred to as program control. The slope of the SV should be adjustable by modifying the parameters of the corresponding functional block.
Using VELLIM is simpler and more convenient – one functional block does the job, and it also looks more intuitive in the control diagram. For those who are not familiar with CALCU, they need to open CALCU and look at the calculation formulas in order to understand what’s going on.
Could you please draw a detailed configuration diagram showing the connection between the VELLIM function block and the 1FIC1130 function block? My knowledge of DCS systems is limited, so I would appreciate it if the diagram could be as detailed as possible. Thank you very much! ! !