PID Control Question....

One quick question about PID control on a pump using an SLC 5/05 processor. Can I adjust some of the parameters on the PID function that will increase the pump flow rate.

I have this system were a pump was being used to pump a liquid (X) with viscosity (Y) and everything was working correctly. Now the liquid was change to (X') with a higher viscosity (YY) which is causing the system to fault constantly due to low flow rate

Since you haven't given a lot of information, I have to assume the same Flow Setpoint in both cases.

If the Flow is not increasing fast enough, it could be the settings of your PID. i.e. Gain etc.

There are things like Feed Forward in the PID Instruction that can give you a kick start until the PID has time to catch up.

Have a look at the PID Chapter 9 of the Instruction Reference.

http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1747-rm001_-en-p.pdf

You might want to post your PLC Program (Zip it first) so that the PID experts can have a look at your Scaling and PID setup.

Stu....

Sthompson,, you assume right. The flow rate before the switch from liquid X to liquid X' has not change. The only thing I know about this new liquid X' is that it is a little bit more viscous than liquid X, due to this fact that is why I feel that an adjustment to PID function is necessary to perhaps increase the flow a few points up.

What type of flowmeter are you using? What type of pump is it?