Condensate pump installed for cooling tower
Condensate pump installed for cooling tower
(OP)
there is chilled water system having cooling towers.the suction pipe from the cooling tower outlet to the inlet of the condensate pump is sized having a flow velocity of 9 feet/second(it is quite high).when calculated NPSHa for the same system and compared it with NPSHr then it was found that the difference between NPSHa & NPSHr is about 7 feet.NSPHa is more than required.
my question is that will there be cavitation in system because of smaller suction pipe even though NPSHa is more than NPSHr. if there will be cavitation then how to get rid of it?
my question is that will there be cavitation in system because of smaller suction pipe even though NPSHa is more than NPSHr. if there will be cavitation then how to get rid of it?





RE: Condensate pump installed for cooling tower
RE: Condensate pump installed for cooling tower
Fast enough reply?
P.S.
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It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Condensate pump installed for cooling tower
If it cavitates then either increase the static head, lower the friction losses (bigger pipe) or install a bigger slower speed pump or a pump with an inducer on.
PS, A 5 hour delay in responding on a Sunday afternoon isn't something to get upset at....
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Condensate pump installed for cooling tower
So to answer your question, no that won't be sufficient to completely suppress cavitation. To do that you'd need a NPSHa of > 80ft.
However what is more important is that you operate with the NPSH margins recommended by HI 9.6.1 (2012). For cooling tower pumps the ratios recommended are 1.1 in the POR and 1.3 in the AOR.
RE: Condensate pump installed for cooling tower
RE: Condensate pump installed for cooling tower
RE: Condensate pump installed for cooling tower
In mean time may i know what is recommended maximum velocity limit for the suction line?
let me explain a bit about the project. there are 3 cooling towers(counter flow)having capacity of each 1500 TR.cooling towers are installed on a steel structure that is 2.5 meter high from floor level. Condensate pumps(3D+1S)having a flow rate of 4500 USGPM each are located on same floor level. Total water flow from cooling towers is 1500 TR x 3gPM/TR x 3 cooing tower= 13500 GPM.Suction header pipe from cooling towers is sized to be 600 mm having velocity of about 3 M/s.
As per Manufacture curve,NPSHr is 4 meter where as NPSHa is 6 meter.
Today pumps are started again but unable to get design flow & head when run at 50 HZ. all pumps are equipped with VFD.we are getting 70% of design flow rate.Thanks
RE: Condensate pump installed for cooling tower
Below about 1m/second the friction losses start to be come nearly negligible, especially for short distance lines, but other than that the maximum velocity is what your system needs to perform in the lowest possible cost
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way