Sharing this post from a user in the DeltaV Group
Hello,
I have a puzzling question or concern. I am still a bit new to Automation, but learning.
Often operators at my plant will show me a control loop (flow, pressure, etc) and state the the valve is swinging (oscillating) all over the place. Then there is a request for me to tune the loop.
One of my biggest concern is that, "what if there is some other instrument, I/O communication, valve, positioner, etc malfunction that causing the overshoot or instability in the loop". I don't want to just start tuning a loop without proper investigation of the entire loop to make sure maybe valve is not funcitoning correctly.
Is there anything I can read related to proper diagnoistics of a valve assembly as it relates to tuning a loop?
Is there a program in DeltaV I can use to monitor the loop performance to see how the loop performs for all process conditions?
Like now, I have a loop with PV Scale of 0 - 3000 pph, loop is in manual, the PID out is 10% (and valve is showing 10% open), and the PV is 1600 pph. It doesn't make sense to me how the valve can be only 10% open while operating at 1600pph which is the mid range of the scale. maybe I am confusing my self.
Thanks for the help.
Best Regards,
Rachelle McWright: Business Development Manager, Dynamic Simulation: U.S. Gulf Coast
You are correct in thinking that all loop problems can't be corrected by tuning alone. "Bump" testing the valve is one way to determine the health of the assembly. There is a class for that... www2.emersonprocess.com/.../9006.aspx
"Bump" testing for stick/slip and deadband are discussed as well as various loop tuning methods.