Pump Suction Press Vs. Vap. Press.
Pump Suction Press Vs. Vap. Press.
(OP)
In the data sheets of some new pumps I noticed that the pump Suction Press. is equal to or a bit less than the pumped liquid Vapour Press. at the pumping temp.
Wouldn't that cause a cavitaion problem?
In addition, the data sheets shows that there is NPSHa (few meters). But how come we have NPSHa, while the pump suction press. is already less than the pumped liquid vap. press?!!
Thanks,
Wouldn't that cause a cavitaion problem?
In addition, the data sheets shows that there is NPSHa (few meters). But how come we have NPSHa, while the pump suction press. is already less than the pumped liquid vap. press?!!
Thanks,





RE: Pump Suction Press Vs. Vap. Press.
Then, of course, check whether the suction pressures, as given, are absolute or gage. Kindly report back.
RE: Pump Suction Press Vs. Vap. Press.
RE: Pump Suction Press Vs. Vap. Press.
In addition, tow values are given for the Suction Press. Max. and Rated. So, I would assume they mean the suction at pump inlet.
And both suction and vap. press. are given in Abs.
RE: Pump Suction Press Vs. Vap. Press.
RE: Pump Suction Press Vs. Vap. Press.
1. Since NPSH is defined as the difference between total head (static and dynamic) and the vapor pressure, both at the pump intake, the only "contributor" left for the NPSHA is the velocity head u2/2g, which is usually negligible, except when using inducers, which are, in effect, small "booster" pumps that are capable to handle a bit of vaporization without suffering cavitation problems.
2. However, if the suction pressure Ps is taken at the reservoirs, you still have the elevation difference between the reservoir and the pump's eye less the friction loss in the suction pipe, as a contributor to the NPSHA, a difference that may be larger than the small positive or negative (Ps-Pv) difference you mentioned.
Kindly comment.