We found that there is a flow lag below the set point. Controller is slow to react to a set point change. Though we set the standard temperature and pressure conditions to 25oC and 14.696 psia, it increases to 34oC and 78 psia respectively. The control valve also heats up.
What could be the possible problems? How can we tune the PID values? we set the values as shown in the manual. But still, the problem occurs. Kindly give us the guidelines to rectify it.
Hey Cyril,
You may want to contact Alicat Field Service Engineer on this issue.
From your description, it seemed that the performance is a little sluggish. Perhaps the values of PID gains shown in the manual are designed to be over-conservative.
If you are authorized to tune the PID gains, try the following:
- increase Kp for faster rise time,
- increase Ki for faster rise time,
- increase Kd to reduce the overshoot and to raise the stability.
Good luck!
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