Maximum suction velocity

[Lan123]

What could be the maximum permissible velocity through a pump suction pipe. According to Hydraulic institute standards this is 2.4 m/s. However some of my colleagues say to limit the max. velocity to 1.5 m/s. The suction Pipe run is straight and about 13 ft long. Application is sewage. Maximum flow rate is 2.1 m3/s.

Thanks is advance

 

[bimr]

Those are examples of rules of thumb or general guidelines. Here is another rule of thumb. Suction piping should generally be at least one size larger than the suction flange at the pump

You need to analyze the proposed installation with the specific pump and piping layout. You need to verify the Net Positive Suction Head Required by the pump.

http://www.gouldspumps.com/pag_0006.html

http://www.mcnallyinstitute.com/02-html/2-7.html

 

[DubMac]

Like Bimr says, size the suction pipe next size larger (2 sizes max) than the pump's suction flange and be done with it.

Unless there are vortexing or air entrainment issues; there is no reason to make piping any larger; just wasting money.

The only pump internal fluid velocity "rules of thumb" I am aware of are for discharge columns in verticals, where they should be kept above 5fps to keep solids from dropping out and max of around 15 fps to keep from washing out the lineshaft bearings and keeping friction loss in check.

 

[cvg]

8 fps versus 5 fps - I would keep it closer to 5fps, no reason to be close to the maximum. Also, I assume this is a header for multiple pumps judging by the high flow rate? Or is this really a 33,000 gpm pump?

 

[Lan123]

cvg,

Each pumping unit can pump 33,000 gpm. Each pump has its own individual suction pipe (14 ft in length) out of the wet well. There are no suction headers.