centrifugal pump minimum flow control
centrifugal pump minimum flow control
(OP)
What would be the criteria to select the use of an automatic flow control valve vs. an restriction orifice installed on the spill-back line?
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centrifugal pump minimum flow control
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RE: centrifugal pump minimum flow control
There's one other factor that sometimes comes into play, and that is plugging tendency. If it's a potentially plugging service, then a continuous recirculation flow (e.g. using an RO) is less likely to become plugged.
RE: centrifugal pump minimum flow control
RE: centrifugal pump minimum flow control
If only used occasionally, low power and most of the time in standby/low flow mode then an orifice is a cheap and simple solution.
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RE: centrifugal pump minimum flow control
RE: centrifugal pump minimum flow control
RE: centrifugal pump minimum flow control
What is stopping forward flow?
I've seen a lot of "spill backs" - I hate that term - installed just because that's what they did last time.
If your pump is intermittent on a level switch, why do you need this waste of energy? What causes the flow to go below min continuous flow or no flow for long periods of time?
The orifice or valve should be sized such that the outlet head is maintained and the pressure drop taken across the orifice.
Those flows seem quite high for min flow. It means you have a pump 30 to 50% Bigger than you need.
Strange sounding design.
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RE: centrifugal pump minimum flow control
RE: centrifugal pump minimum flow control
I can't see enough of your design and operation to know how it might work without it, but often designers are just lazy and stick one in and don't concern themselves about the electricity bill you get...
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RE: centrifugal pump minimum flow control
2) A globe valve on each pump discharge may work for a limited range of built up backpressures in the common dishcharge line going offsite. If you find your forward flows vary beyond the operating range for the globe valve, then would suggest a PIC - PCV on each pump discharge.
RE: centrifugal pump minimum flow control
I attach one sketch to explain better the case. Hope it helps. Regards!
RE: centrifugal pump minimum flow control
RE: centrifugal pump minimum flow control
RE: centrifugal pump minimum flow control
Your sketch is interesting, but doesn't really tell us anything about the d/s system, how it works, what flows and pressures etc are present.
I can only assume that whoever devised this system thought that there was a potential that if the other users all used the system at the same time, the back pressure would be enough to either stop flow from your pump or severly reduce it.
However your idea of the globe valve shouldn't be required if the orifice is sized correctly. The differential pressure across the orifice plate should be sized based on realtively low flow through the pump, hence a high head. The globe valve won't help to increase pressure, but would, of course, mean that more of the flow through the pump went down the line instead of back into the tank.
If you enough flow then simply put an isolation valve there and turn it off if this is a manual operation.
Like I've been saying, unless you really understand the operation, flow, pressure etc being or likely to be experienced you can't make judgements or design it properly. If things keep changing you can't just set an orifice or a globe valve and expect it to magically change when things change. That's why ARV valves do this automatically without any electrical or instrumentation input, Then you get "spillback" when you need and more flow though the system when you don't. This sort of thing is what they were invented for.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: centrifugal pump minimum flow control