Vortex in suction of multiple pump sump 1

[CCA]

When adding an extra pump to a cooler tower bassin, the question rose : "where should I place this suction pipe in the bassin to avoid strong vortex and negative effects on flow and pump?"

Are there recommendations for minimum distance you should keep between suction pipes (of different pumps) and what about the distance to walls?

Is there equipment that can be used for reducing vortex-effects

Thanks...
Michel

 

[quark]

If you just search this site by the keyword vortex breaker, you can find many discussions.

Vortex breakers ( + shape, atleast upto half the height of suction pipe) are generally used to prevent vortexing. You can also find among past threads, a formula for minimum submergence of suction pipe to avoid vortexing of air.

My thumb rule, to prevent cross flow of water, is to keep a distance of 10D between the suction pipes.

Regards,

 

[MJCronin]

CCA, QUARK,

I am assuming that this is a vertical axis centrifugal pump that you are adding to a cooling tower basin

You should be aware that this is a classic problem that has been addressed by the Hydraulic Institute in some of thier design guidelines. (ANSI/HI 9.8)

See:

http://www.pumps.org/bookstore/

There is also a good discussion of pump spacing, water levels and sump layout in the "Piping Handbook" by Nayaar. Generally speaking, unless the sump was designed for the extra pump, you may be causing a lot of problems by adding it to the basin. You may have to consider an extension to the basin for the new pump

Its a good thing that yor boss will not hold you responsible for any decision made by others.....

Come back and tell us more about the pump design, size and capacity......

My opinion only

MJC

"There comes a time in the affairs of man when he must take the bull by the tail and face the situation." W.C. Fields

 

[CCA]

MJCronin, Quark,

Thanks for your information, I'm indeed going to check out ANSI HI 9.8.

Concerning the pump this is a horzontal centrifugal pump of 1500m³/h placed next to the pit. There are already three identical pumps present, the distance between there (18&quotsuctions is 5.1m(Cl-CL). The new suction will be unfortunately placed at 1.5m from one of the existing suctions.

I already calculated (with the ANSI HI 9.8 formula)the vortex of the 2 pipes together, which should be 2.7m (assuming 3000m³/u in a 20"pipe). And as the water level to the suction is 3m, there doesn't seem to be a problem.

I'm more preoccupied that pump damage might occure. I'm thinking on cavitation, but as the water is not more than 20°C and the water level in the sump is minimum 0.6m higher than the pump inlet, this also doesn't seem to be problem.

So, what do you thing? What might be the problem that we should consider?

Thanks,

M