Strategy to share load between duty and assist pumps

Hello,

I have to design a irrigation pump station for a capacity of 180 lps at 75 m head. How to decide the capacity of duty assist and standby pumps?.

Is there any thumbrule like 60% should be duty and 40% by assist like. what are the possible cobinations i can go for and which is the best?.what should be the capacity of standby pump?.


Thanks
JR

There isn't really any rule. The most common techniques are cascade and parallel (or balanced) flow rates.

Generally the pumps are sized equally. I am going to assume you have a flow control technique for both pumps - VFD or automatically controlled throttling valve.

In both methods when the second pump is started both pumps are reduced to 50% of desired flow. Then as demand increases the flow of the lead pump is increased and the lag is maintained at 50%. Once the lead pump reaches maximum then the flow of the lag pump is increased.

With parallel or balanced flow as demand increases both pumps are increased to maintain equal flow on each. This is my preference, but both will work fine.

Thank you Mr. Tom

I would like to design a pump station of capacity 150 lps @ 75m head. Now what should be the ratings of duty assist and standby pumps?.

what are the intruments,controls and valves to be used and how to decide the size of suction and delivery piping?.