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Flow Control Logic Case

03/29/2012 1:51 PM

We are having 3 pumps (2W+1S) for supplying water via common header to two different locations (Say Location1 & 2) using piping now,

Location 1 is at a distance of 25m from the pump house at required head at this location shall be 30m and same from the same header another pipe runs to take this water to location 2 which is at a distance of 450m.

Now flow requirement varies at both the locations but for the process the pressure at both the points should not vary with flow.

How to control this flow seq. using the instrumentation or logic?

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#1

Re: Flow Control Logic Case

03/29/2012 4:50 PM

You say that "pressure should not vary with flow", but there will be pipe friction losses, so there will be some pressure loss.

You will also need to nominate the boundary conditions for the system, like what volumes are being pumped (peak and base loads), intended pipe diameters, datum height differences between the locations and so on.

Your solution might be as simple as a VSD on the pumps using feedback from a pressure transducer in the pipeline, or could require a full ring main with "constant" flow at around 10x your maximum demand, or even "header" tanks that may or may not be pressurised.

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#2

Re: Flow Control Logic Case

03/29/2012 5:19 PM

As stated above, as the fluid flow changes so does the friction. No amount of pump logic or control can change that. If the changes in pipe friction is tolerable, then a VFD could work.

The other option I see would be to install pressure regulating valves in the lines near where you need constant pressure and maintain the supply line charged high enough to handle the variations in flow.

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