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Anonymous Poster

Common suction for pumps in parallel

04/09/2009 9:02 AM

Three pumps are running in parallel,the suction of all pumps is connected to common pipe by using cross and elbow. on one side of cross is common suction pipe and on opposite side is suction of one pump and on remaning two sides of cross remaning two pumps are connected by using elbows.The water level is 2m below pump axies

so my question is that wehter the pump performance will effect by this type of suction connection
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user-deleted-1105
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#1

Re: Common suction for pumps in parallel

04/09/2009 9:17 AM
Re: Common suction for pumps in parallel
If the pipe bore is big enough it will be ok.
On any suction system there is only atmospheric pressure driving the liquid, any restiction on the inlet will impede the flow, any non-return valves/strainers etc need to be big enough to handle the total flow (or twice as much to give some lee way).

There is also the question of the smoothness of the flow, if you are talking about high flow rates, then a load of 90 degree bends won't help, especially if you are pumping a viscous product.

Del

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sb
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#2

Re: Common suction for pumps in parallel

04/09/2009 9:39 AM

1) If your cross and elbows are properly sized so as to not create a low suction head (NPSH value should be maintained)

2) Put a sufficiently long straight line between the last of the cross/elbow and the pump suction flange/port. this is to ensure that the flow is laminar (at least almost) as it enters the pump.

3) Check the flow velocities and the turbulence at the cross when all the three pumps are switched on.

If all these are OK then it will work.

However in our designs we prefer to have a large suction header pipe and take individual tapping connections for the three pumps. Why do you want to have this type of tree structure ?

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PWSlack
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#3

Re: Common suction for pumps in parallel

04/09/2009 10:23 AM

<...so my question is that wehter the pump performance will effect by this type of suction connection...>

For a non-self-priming pump, provided there is a net positive suction head, then no.

<...The water level is 2m below pump axies...>

That would indicate that there might be a problem, which is, how do the pumps get primed when empty?

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