2 identical parallel centrifugal pumps ?

[maxx_payne]

2 identical parallel centrifugal pumps ?

hello everyone i have a very confusing problem with a cold water system sonsists of 2 identical centrifugal pumps their position is under the tank so there is always a +ve suction head then those pumps takes water from the tank and deliver it to a very simple pipes network to achieve the required processes with the water such as cooling gases via heat exchangers and this water is used also as feed water to some other water systems but to make cooling """other words """"""""" closed circuit

so the problem now is that some times when i operate one pump i found out that there is no water at all in the circuit althoug i can see the vortex of suction in the tank
also all of the heat exchangers are okay no mixing
i don't know where does the water go ?


and when i work both of them everything is okay
but each pump is 100 hp and 196 m3/hr and has a head of more than 100 mt
so can this be an impeller problem of the pump ?
or what's the problem i don't know ?

 

[maxx_payne]

its a very big problem i know can anyone help me ?

 

[Jobrag]

Is it possible that the flow is going back to the tank via the second pump? If you have isolating valves try shuting off the non-running pump.

 

[maxx_payne]

well i have also check those valves

 

[maxx_payne]

but u know there is a phase in the flow in pipes nammed syphon ?? can it be this problem ?

 

[maxx_payne]

but the pump head is very high for this application

 

[lotfiplan]

Dear MR or Modam:

I think you don't have the CHECK VALVE in the discharg of pumps. yor prolem hapend in the time tath you don't close the shoted pump discharg valve .
the water circulate inthe shoted pump .and it cuse the rotation of shoted pump in on usual rotation side and probably cuse to open the impeller nut of shoted pump.

close the shoted pumps valves to solve the problem.


Mortaza Lotfi


lotfiplan@hotmail.com