Minimum submergence level for positive displacement (PD) pumps
Minimum submergence level for positive displacement (PD) pumps
(OP)
Hi all
1. Is formation of vortices (and air being sucked into) a general concern for positive displacement (PD) pumps?
2. If yes, how can the minimum submergence level be calculated? Can the equation available in HI 9.8-1998 Par.9.8.7.3 be used??
Thanks.
1. Is formation of vortices (and air being sucked into) a general concern for positive displacement (PD) pumps?
2. If yes, how can the minimum submergence level be calculated? Can the equation available in HI 9.8-1998 Par.9.8.7.3 be used??
Thanks.





RE: Minimum submergence level for positive displacement (PD) pumps
1) Not really. Especially oscillating PD pumps like piston (not plunger!) and diaphragm pumps can handle entranced air but also peristaltic pumps are not sensitive to that. Rotating PD pumps like progressive cavity (eccentric screw) pumps are more sensitive but triple screw pumps for example are very suitable to work with gas/fluid mixture. It all depends upon the amount of gas and its distribution.
2) HI = Hydraulic Institute? I do not know the corresponding chapter but as long as the suction entry is flooded all PD pumps work well - not considering NPSH, but that is a different topic.
RE: Minimum submergence level for positive displacement (PD) pumps
2) Not come across this before, but looked it up and seems to be the business for pump inlets (I learnt something new...). As said there are other easy things you can do apart from submergence depth to reduce or eliminate vortices such as bigger inlet, orientation of inlet, inlet guide vanes, end plate and side entry slots.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way