Air entrainment in sump

[bumpjones]

We are looking at installing sump tanks for our cooling tower. The tanks will be in side the building and above the pumps. Is there any way to prove that the vortex that will be created does not reach the suction of the pump. The tanks are 10 feet tall and 7 feet in diameter. The flowrate is 2300 gpm maximum.

 

[MJCronin]

Why don't you just install a vortex breaker in the pump suction nozzle and ensure that the suction velocity is low ?

Vortex breakers are commonly installed in low-NPSHa applications, and Cooling Tower Pumps are classic examples.... for several reasons. Vortex breakers ar simply "X" type plates that have about 1.5 times the nozzle diameter as the edge length. Usually 3/8 inch mild steel stock is acceptable....

Additionally, you can ensure that the suction velocity is about 3 to 5 feet per second (always use pipe one size larger than the suction nozzle) and you should have no problem. Any elevation head that you can build into the system will help.... but a long term penaly will be paid in electric charges......Big Pipe rules !!!!

Ask your MBA boss to purchase the "bible" for the department....I'm talking about the "The Pump Handbook" by Igor Karassik.... and many of your questions will be answered..... then again..... if he has an MBA, there is probably no money in the project budget and he is off travelling to a conference.....


MJC

 

[Gerryod2]

Where could I find literature on airbinding (vapor lock is the same thing, right?) of centrifugal pumps? With examples showing piping and pump configurations where it has actually occurred from air (or gas) entrainment or sudden influxes of gas. Also literature with examples of how much air or noncondenseable gas caused cavitation that caused catastrophic sudden failure of cent. pump. The situation that I'm concerned about is a 13,000 gpm single stage, double suction vertical Byron Jackson pump with a 20 inch diameter intake suction and areas of the pump volute 8 inches higher than the outlet of the pump which is a 16 inch line. The air would have to go about 25 horizontal ft and down about 3 vertical ft once it got in pipe. I don't imagine that when the pump is on min flow (about 500 gpm) that the air would be pulled into the pump but rather when the pump is running at about 13,000 gpm. Also, wouldn't the most likely part on a pump to fail under these severe cavitation conditions be the mechanical seals or bearings before the impeller? Also at the pump inlet would be jagged pressure pulsations where the absolute pressure would vary between 2 and 3 atmospheres. Could I find literature with actual examples and detailed descriptions of cavitation or damage caused by pressure pulsations such as these? Thank you very much for your kind attention.