Hello everyone -
I have a problem with two identical fire pumps rated at 145 psi at 2,500 gpm.
When testing for 0% flow and 100% flow the pump gives the correct pressure, but, when testing 150% flow the pressure drops dramatically, it has to show 125 psi and the result is 92 psi.
The pumps has a 10-inch flange suction an as NFPA allows it was installed a 10-inch pipe directly to the pipe, no suction reducer, having 16-ft (5 m) long of distance for one pump and 19'-6" (6 m) for another one, the second one with two 45-degree elbows installed more than 10 times the diameter from pump suction.
The tank is 23-ft (7 m), full of water. The test outlet is installed on the other side of the tank, so the flow does not fall over the suction inlets. The antivortex inlet has a plate of 7.5 inches above the floor.
The pump discharge is 10 inch.
The flow meter is 8-inch diameter with 8 diameters before and more than 5 diameters after.
Any idea why the pressure at 150% is so low?
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