Must the suction lines of parallel pumps be equidistant? In our plants (petrochemical), we normally have two pumps installed in parallel, one running and the other stand-by. Every 20 days we change the pumps (stop the one that is running and start the one that is in stand-by). During change of pumps, we do not have a problem, except with two pumps, which pump cyclohexane (cold) and there is not a equidistant arrangement between the suction lines of the pumps. But the problem is only with one of the pumps. For example, we have two pumps -- A and B. When A is running and we change to pump B, we do not have problem, but when are going to do the contrary, (Change B to A) we note a discharge pressure reduction.
Have an insight or suggestion?
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Re: Why is there a difference in pump output?
4 January 2010 at 1:29pmIn approaching this problem, it must be remembered that the centrifugal pump is a slave to the system, so when there is a difference in pump output, there must be a difference in the system to require that change.
With a discharge pressure reduction from Pump B to Pump A, (and assuming these pumps are identical!) there must be a difference in the total head required by Pump A. Such differences can only come from the system. As you indicate there is a difference in the suction side of the two pumps, then it would be logical to assume that the difference is the source of the problem.
Hope that helps.
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