Pump Selection

[haniyah]

If I have to pump chilled water at a rate of 850 gpm, how many pumps should be ideal for pumping this amount of water?

On which basis we select that this much pumps should be chosen?

your answers will be highly appreciated.

 

[micalbrch]

One pump is enough unless you want to have a stand-by unit. The pump selection depends upon the head/pressure. But it will be most probably a centrifugal pump. It is not a big deal for a centrifugal pump and there are plenty of suppliers worldwide.

 

[FilipeScherer]

I agree with micalbrch. One pump must be sufficient, but first you've got to know the head of your system, and not only the volumetric rate flow.

 

[haniyah]

Thanks for the reply guys.

Actually i have to serve three building with chilled water and for that the flow is 850 gpm and head is 145' (I just count longest run and found dynamic head and add static head and add minor losses). So if i want to put two pumps in parellel other than a standby, can i go for this or is there any rule of thumb for considering the quantity of pumps and how can i apply the diversity factor on each pump.... any formula?

 

[BigInch]

You must find the maximum head at the pump for the distribution system. That may not be the longest run. It will be the highest head requirement of any circuit running through the pump, taking into consideration the flowrate of each segment of piping in the circuit.

**********************
"The problem isn't finding the solution, its trying to get to the real question." BigInch

http://virtualpipeline.spaces.live.com/

 

[stanier]

Chilled water systems have a very high degree of demand variability. I would think you may be better off with 5 say pumps each operating at their BEP. They may not all be the same size.

District cooling systems rarely pump chilled water from one tank to another. generally they service a number of buildings where demand changes from night to day and summer to winter. Buildings are taken out of a CHW system if they do not have tenants.

First exercise would be to do the hydraulic study for the diurnal and annual loadings. Then you have a basis for investigating the pump sizing and numbers.

 

[MJCronin]

hani...

stainer is correct....a system study is necessary

How about turndown of the system ?

What happens to you system if a pump fails and takes a month to fix (not uncommon)????

-MJC