hydraulic separation walls 4

[broekie]

I have a questions regarding water pump station design. I have a 25' diameter pump station with 3 submersible pumps.

On rectangular pump stations that I have seen, there are divider walls/hydraulic separation walls between the pumps, I'm assuming to avoid cavitation type issues. Are these required for a circular pump station? Is there some sort of minimum distance between the pumps that I need to have to avoid needing those walls?

I have the NHI "Highway Stormwater Pump Station Design" Cirular #24. They talk about separation walls for rectangular pump station, but nothing for circular ones.

Any further input/design references would be appreciated. Thanks.

 

[BigInch]

Those are antivortex walls and are supposed to keep the flow moving straight into the pump suction area. Maintain at least the minimum distances from intake to surface, bottom and sides as are given for the quad shapes.

http://virtualpipeline.spaces.msn.com

 

[rcooper]

You will almost certainly have difficulties with a circular sump as you have proposed. The water will enter the sump, presumably directly opposite one pump. It will then flow across the sump and split in two, moving in a clockwise direction for one of the side pumps and an anticlockwise direction for the other side pumps (pre-rotation). This will result in one of these pumps pumping more than expected and drawing more power than expected, possibly overloading the motor and the other pumping less than expected, possibly leading to the pumping station failing to meet its design criteria.

They are also likely to form floor vorticies under the pumps, which will damage the pumps, particularly the seals and possibly the bearings.

What you want to achieve is a uniform flow to the pumps. A baffle wall at the inlet to slow the flow down and distribute it across the sump will help, as will side walls around each pump intake.

For a sump of this size, I would seriously consider having it hydraulically modelled. This will be able to show that it will be able to transport grit and scum through the pumping station with no build up and that the conditions for the pumps are adequate.

Alterantively, get a copy of the Flgyt design manual for submersible pump sumps and follow the guidance in there. The manuals were based on hydraulic testing and are excellent.

 

[BigInch]

rcooper, great answer. It didn't occur to me that he might be thinking about not having some kind of flow direction. That's one big jacouzzi he's got there.

http://virtualpipeline.spaces.msn.com

 

[broekie]

Thanks for the input. I do have a baffle for the pump station. The storm water enters the pump station directly opposite one of the pumps. However, the water hits a solid wall and splits in 2 directions. This water then goes through trash racks before it has a chance to enter the pumps.

This should help with the flow, but I still wonder about having the walls. Any direct links to the Flygt design manual - I couldn't find it on their web page. Thanks.

 

[bimr]

Don't believe the brochure is online. The brochure is titled:

design recommendations for pump stations with large centrifugal wastewater pumps

http://www.flygt.co.uk/26267.asp