Throttle Pump Outlet?
Throttle Pump Outlet?
(OP)
I currently have a tank water pump that is cavitating. I can throttle the flow by closing the butterfly valve on the discharge, and this stops the cavitation. But I was wondering if there was a more suitable permanent solution (not looking to install an orifice plate since there are 4 pumps in a row that run at different rates). I was thinking of changing the impellar size or its housing.





RE: Throttle Pump Outlet?
RE: Throttle Pump Outlet?
RE: Throttle Pump Outlet?
RE: Throttle Pump Outlet?
Throttling is acceptable, if you don't have to throttle too much, as long as the throttled flow is still adequate for downstream needs and you can keep above 50% of the pump's BEP flowrate. If the throttled flow where cavitation stops is not adequate, there is little you can do about it except increase suction pressure of that low flow. That would be much better than trimming the impeller. You need a pump with less flow and trimming is more suited to lowering discharge head. Depending on the % flow you need, trimming can be very inefficient. The best way to get less flow w/o throttling is by reducing speed. Any chance of that?
http://virtualpipeline.spaces.msn.com
RE: Throttle Pump Outlet?
RE: Throttle Pump Outlet?
RE: Throttle Pump Outlet?
RE: Throttle Pump Outlet?
Sounds like a tank is just the thing for this installation, then you could stop that pump, use tank flow to feed a continuous process while you wait for supply pressure to build, or otherwise, I hate to say it, try putting one pump on a VSD (or two if you think this condition will last long enough that you'll have to rotate duties) and keep running continuously on low speed.
http://virtualpipeline.spaces.msn.com
RE: Throttle Pump Outlet?
RE: Throttle Pump Outlet?
Johnny Pellin
RE: Throttle Pump Outlet?
http://virtualpipeline.spaces.msn.com
RE: Throttle Pump Outlet?
RE: Throttle Pump Outlet?
RE: Throttle Pump Outlet?
http://virtualpipeline.spaces.msn.com
RE: Throttle Pump Outlet?
Without this information it makes it difficult to recommend solutions- although since you've now discovered your on the right hand side of the curve for the pump it's relatively easy to pick out the solution(s) from those offered above.
RE: Throttle Pump Outlet?
RE: Throttle Pump Outlet?
Now, my question is; why not just start a second pump which will half the flow and push the first pump back on its curve and hopefully far enough back so that both pumps will run in a non cavitating mode?
rmw
RE: Throttle Pump Outlet?
RE: Throttle Pump Outlet?
Starting a second pump might work. But it depends on the system curve. If the downstream system is pretty much wide open with a very flat system curve, starting a second pump might just result in two pumps running with cavitation. If there is no flow control valve downstream, you cannot assume that you will end up with two pumps running at 50% of the original flow rate. But, you will be using up a lot more horsepower and might still have a problem. I would stick with flow control, back-pressure control or simple throttling.
Johnny Pellin
RE: Throttle Pump Outlet?