Conversion of Legacy PIDs to a modern system like DeltaV is not always easy. We continually get questions, sometime late in the project, i.e. at start-up when the loops are not performing correctly or wildly oscillating. For sure not all PIDs are created equal. PID forms may be different on and between systems. PID Structures typically are selectable and thus different as well. Then you have complications on selection of units. There are choices like Standard, Classic, Series, Parallel among others for PID forms. Conversion units are also variable (seconds, minutes, hours, repeats/ time, or time/repeats), selection can be on a system basis, some can be selectable on a on a per loop basis. Below is an example of APACs to DeltaV Conversion tips. Please share any other conversion tips, tricks, or lessons learned that you have used successfully on APACs or other Legacy conversions.
Reset (DELTAV) = 60* TI(APACS)
Rate (DELTAV) = 60* TD(APACS)
If you find a TI(APACS) = 4000, then the integral is turned off and you should choose a DeltaV PID Structure = PD.
Be sure to set DeltaV PID ARW low and high limits equal to the DeltaV OUT_SCALE.
Remember, the APACS filter block setting TLAG is in minutes. DeltaV filters, including PIV/PF_FILTER, have units of seconds so the DeltaV filter setting is 60*TLAG (APACS).