pump control using VSDs


Thread Starter

ziad khudr

could u please lead me to web sites on pump control using VSDs, my case is replacing choke valves with VSDs on a constant head pulp network. is it doable? my suggetsed change is less than 40% reduction in speed, is this ok?
please help
I have no direct experience in controlling a pulp network at constant pressure but do have experience of controlling dilution water networks in both pulp and paper mills using VSDs.

No problems, it works really well. You will be amazed at the control loop response. I think the dynamics of a VSD are much faster than a butterfly
valve (when controlling water pressure) or a vee-ball valve (when controlling pulp). We have not experienced problems with pump characteristics even on plant start up.

You will save loads of energy.

If you want details, please contact me off-list

Good luck

Peter Green
Semi-retired Control Systems Engineer - New Zealand

Bill Sandidge

The answer is... maybe. It depends on the type of pump and its characteristics ( head vs. flow vs. speed).

A pump running at 60% speed will likely have very
different characteristics from one running at 100%
speed. This may or may not cause problems.

If you can get a copy of the pump curves (head vs. flow, and if you're lucky at different speeds) from the manufacturer I might be able to help answer your questions. If you find them you can send them to me at the number below and I'll take a look at them. I put in hundreds of pumping systems at my old job; I kind of miss it.

Whether or not it is doable depends on where your
application falls on the pump curves. Usually it's
not a problem but you need to be sure before you
install an expensive new VSD.

Another possible consideration is motor overheating. The motor's cooling fan also runs slower and its effectiveness falls off exponentially with speed. This can be dealt with if need be however.

Bill Sandidge
Instrumentation Design, Inc.
Atlanta, GA
[email protected]
Phone: (404) 874-1151
Fax: (404) 872-5522