What concepts/rules apply for multi-stage pumping of water?

Question

For single-stage (ie one pump) water transfers calculations for pressure loss are commonly done by adding the elevation difference of the start and end of the pipeline to the friction losses that occur within the pipe system.  Friction losses can be determined through such formula such a the Hazen–Williams equation.

If you have a pipeline with a series of pumps in line are there any additional effects besides the increase in inlet pressure at the booster pump that needs to be considered?  Specifically, I am wondering if there is any effect from the momentum or velocity of the water that is being delivered to the booster pump that needs to be considered?

user3823992 · Answer

I don't believe that this would be necessary.

Most pumps (not constant volume ones) have a relationship between flow rate and pressure jump (often called a pump curve). Since the entrance diameter of the pump doesn't change, you've got (basically) the same momentum in the pipe at a given flow rate regardless of how it gets that way.

Another way of looking at it is that any effect of the momentum is already taken into account experimentally when the manufacturer generates the pump curve.

My memory is a bit hazy on this, but I do seem to recall that some kinds of pumps don't respond well to particularly non-uniform and/or turbulent flows entering them. The net result was that you'd want to have a decent (ten-ish diameters) section of straight pipe leading up to the pump after any bends,valves etc.

What concepts/rules apply for multi-stage pumping of water?

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