Recirculation loop to boost NPSH
Recirculation loop to boost NPSH
(OP)
I have a water based product that I need to pump from a tank that will result in a NPSH of 3 ft. All the pumps I can locate need at least 5 ft to operate. I have heard the a Recirculation loop can be installed to increase the NPSH. The velocity pressure from the loop directed into the suction will increase the NPSH. Where can I find info on how much to recirculate?





RE: Recirculation loop to boost NPSH
Off the top of my head, just quickly thinking about it, it doesn't sound right.
Have you tried talking to the source that you heard this solution from?
Typcially, if we are only out 2 feet on NPSHa, we dig deeper.
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RE: Recirculation loop to boost NPSH
Can the layout of the pump relative to the minimum liquid level in the tank be changed?
Mark McLean
WorleyParsons
RE: Recirculation loop to boost NPSH
Shallow well pumps may have the venturi mounted on the pump or inside the pump casing.
respectfully
RE: Recirculation loop to boost NPSH
Naresuan University
Phitsanulok
Thailand
RE: Recirculation loop to boost NPSH
Visit thread407-130418.
RE: Recirculation loop to boost NPSH
I don't know the flow rate. The pumps are generally manufactured in sizes from 1/3 hp. to 2 hp. The control is typically but not always a pressure switch on the discharge or a connection to the pump housing; on at 30 psig., falling and off at 50 psig., rising.
The shallow well versions will easily lift water 20 or 25 feet.
Some models are constructed with the venturi in a removable housing bolted to the front of the pump housing. The venturi housing may be removed from the pump and lowered down the well on two pipes for deep well applications.
respectfully
RE: Recirculation loop to boost NPSH
Thnx, however, my question was to "jimdvfd" - is the flow rate 1gpm or 10000 as it will make a big difference to the recommendations.
Naresuan University
Phitsanulok
Thailand
RE: Recirculation loop to boost NPSH
RE: Recirculation loop to boost NPSH
RE: Recirculation loop to boost NPSH
A similar query was treated in thread407-130418. Have you considered inducers ?
RE: Recirculation loop to boost NPSH
Before you get nervous about the NPSHa you need to account for the atmospheric pressure. Talk with your manufacture.
D23
RE: Recirculation loop to boost NPSH
RE: Recirculation loop to boost NPSH
RE: Recirculation loop to boost NPSH
I would think that recirculating more flow back to the pump suction would only make the situation worse, as it pushes the pump performance farther right on the curve which generally has a higher NPSHr.
Are you working with an existing pump? Or are you buying new? If you have the option of buying new, you could select a vertical canned pump to get some additional NPSH. This option keeps the pump out of a pit and saves major piping modifications. It does require a hole to sink the can into however. I've seen it used fairly regularly for pumping out tanks that are near full vacuum.