Modulated (vsd) pumps versus throttle valves
Modulated (vsd) pumps versus throttle valves
(OP)
Pump experts
As more and more vsd's/vfd's are controlling pumps, a question keeps cropping up in our (VSD) team " will vsd controlled pumps eventually replace throttle valves?". We make both. Just wondered what real users feel.
As more and more vsd's/vfd's are controlling pumps, a question keeps cropping up in our (VSD) team " will vsd controlled pumps eventually replace throttle valves?". We make both. Just wondered what real users feel.





RE: Modulated (vsd) pumps versus throttle valves
RE: Modulated (vsd) pumps versus throttle valves
I know all vfds now have line filters, but there is still a concern about rubbish from the vfd carrier frequency getting onto analogue signals.
Valves on the other hand don't wear out and when used with a suitable surplus valve and a flow meter (burkert have a nice paddle wheel meter system) can give easy to use flow control.
I have seen valves used with a pressure gauge upstream and a set of pump curves to give a fairly easy flow adjustment.
Jeff
RE: Modulated (vsd) pumps versus throttle valves
Quark is right that VSD's provide their best advantages in such duties where flow rates need to vary significantly. Where the flow rate can remain substantially constant, a simple induction motor drive should be used without a VSD. (The VSD would present needless additional costs and complications.)
The details of each application's needs will (and should) dictate the specific equipment selections.
RE: Modulated (vsd) pumps versus throttle valves
Does that put the control valve future in question?
RE: Modulated (vsd) pumps versus throttle valves
RE: Modulated (vsd) pumps versus throttle valves
RE: Modulated (vsd) pumps versus throttle valves
I think your point is true. In Denmark we have very high energy taxes. A kWh costs (approx) 20 cents (US) - so here VFD are more poular than many other places.
Best regards
Morten
RE: Modulated (vsd) pumps versus throttle valves
Valves are here to stay, simple, reliable, and on low specific speed pumps they are often more energy efficient than VFDs (yes, they save more energy than VFDs can on the correct pump).
But one we often forget is no valve no VFD. I like that one best when it can be done, and it can be done more often than people think.
I have replaced many complex pump stations with a simple and carefully selected pump on systems with well known hydraulic characteristics, even when flow rates vary greatly.
I had an exchange with a consulting engineer for the Feds about energy conservation. I was questioning his approach where the Feds go into a factory and analyze then make suggestions about the motors and pumps to save energy. He surprised me when he said that he first tries to eliminate any controls with a more correct pump, trim impeller, change the process, etc. If that is not workable, then step up to a VFD or Control Valve, whichever resulted in the highest energy savings.
notnats brings up a valid point about durability. There are local areas in the world where VFDs just have trouble due to transient surges. The areas I know of with dead VFDs hanging on walls, replaced frequently, or having been replaced by control valves are Central and South Florida, Houston, Venzuela, and any area where daily thunderstorms simply wear out VFDs. In those areas VFDs are still used of course, but in many cases they continue with VFDs because they can actually bring great benefits in the right situation.
Silicon will never be able to resist serious transients, and at some point protecting them becomes impractical.
PUMPDESIGNER
RE: Modulated (vsd) pumps versus throttle valves
"Venditori de oleum-vipera non vigere excordis populi"
RE: Modulated (vsd) pumps versus throttle valves
A $1000 vfd might cost much more in down time of the plant.
To send a 10kg parcel same day by air from Sydney to Darwin costs $500, and you still might have to go another 500km to site.
Don't get me wrong, I like vfd's and am always impressed by how small and cheap each new model is and I know the reliablity is improving all the time, but there are areas where a 5 year life is not very useful.
Jeff
RE: Modulated (vsd) pumps versus throttle valves
What happens in the remote location when the valve breaks or gets clogged or the operator mechanism jams and can't be repaired without a total shutdown? At least with a VFD you can sometimes leave a bypass starter in place and get back running in a pinch.
But you made your point and it is not a bad one. As I prefaced my statement, each application must stand on its own merits.
"Venditori de oleum-vipera non vigere excordis populi"
RE: Modulated (vsd) pumps versus throttle valves
mac
RE: Modulated (vsd) pumps versus throttle valves
This was the Gyrol Fluid Drive on was a system that required a variable torque output.
There is nothing to wear out except some bearings, which are readily available.
http://www.howdenbuffalo.com/index.htm