Pump design for maximum flow 2

[mirza057]

Guys,

I have 2 duty pumps for a storm water pumping station. Is it absolutely necessary that we design these 2 pumps for 100% of the flow capacity? What are the factors that would determine this decision.

 

[PEDARRIN2]

At a minimum, the total gpm of the pumps will be what is the peak flow into the station. You will want to be able to pump out what comes in.

How quickly can a pump be replaced? How soon will it be noticed that a pump is not operating. If this is a short time with respect to the flow coming in, then each pump could be less than 100% of the peak flow. If not, they should be 100%.

If you go less than 100%, I would not go less than 66% on each pump, 75% would be preferred. That way, if there is ever a time the real peak flow is more than the calculated flow, then you have built in safety factor.

 

[mirza057]

Thanks Pedarrin..

 

[LittleInch]

Is this a follow on from your earlier post? -

http://www.eng-tips.com/viewthread.cfm?qid=386694

If I understand you correctly you're asking do we need to have 2 x 100%?

There is no absolute in this - it depends on what your operational issues are and the consequences of one unit not working. Only you and the client know that.

The factors would include cost, space, control equipment to turn one off / auto switchover from duty to standby, actual capacity of a single pump, consequence of failure, time to repair / replace, how often they are needed, run time per year, probability of failure / reliability, maintenance undertaken, testing of operation, confidence about the maximum inlet flow etc.

I have seen a few systems where influx of water is such that to cope with the rare peak demand, you have 2 x 100%, but if one is overwhelmed then you have 2 x 100%, but haven't oversized the pumps and power supply.


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[IRstuff]

What are the operational requirements? Requirements analysis should have parsed the top-level requirement into number of pumps and total/partial capacity.

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[mirza057]

Thanks little inch...great answer

 

[MikeHalloran]

You might enjoy a few hours Googling the 'Wood Screw Pump' as used in New Orleans, and focus on the layout of the various pump stations. Swap-out time is irrelevant because they don't make the pumps anymore. The minimum complement seems to be four, or eight or more of the pathetically puny modern pumps that are being introduced.



Mike Halloran
Pembroke Pines, FL, USA