Electric VIL Fire pump data plate: Net 500 gpm @ 90 psi, 150% = 79 psi, max = 100 psi. Assume suction side is always 50 psi. The fire pump is in a mechanical space with a test header that requires 100' of 2 1/2" hose. We are using a 2 1/2" Hosemonster with a 1 3/4" orifice (we have the tables but the coefficient is .975). Start fire pump by dropping pressure at the control sensing line. Pump is operating in churn at 150 psi. Take rpms and controller v/a readings etc., typical of all stages. Now here is where the Hosemonster procedure becomes problematic when plotting curves. If we throttle the test header valve so that the discharge reads 140 psi expecting to get our 500 gpm, we're not actually going to see that at the pitot correct? Would we not have to account for the friction loss of the hose at 500 gpm and add that number to the psi we are attempting to throttle the discharge psi to in order to see an actual 500 gpm? Hose length doesn't matter. If the hose is so long it causes enough pressure drop that the flow cannot be met, then use two of the longer hoses or shorten up the one hose.. If needed, use three hoses, or more. I've seen 8 used.. The maybe-not-so-obvious fact here is: if you hit the desired FLOW out of the hose monster(s) then you will ALSO by default have the desired PRESSURE differential (aka TDH or total dynamic head) across the pump. This is because the pump follows its supply curve. Using a shorter hose would mean the test gate valves would be closed more.. For example, lets say 150 ft of hose and valve is open 75%. Change to 25 ft of hose and you have to adjust valve to 40% open to get the same flowrate.. In both cases the pump differential pressure is 90 psig. Lightecho, I hope this helps answer your questions. I know it is hard to "see" this concept through our words. I suggest learning a bit about pump curves until it sinks in. The pump MUST follow its supply curve, unless the laws of physics breaks down. And physics are hard to get around. This means if you know the flowrate (out of the monster) then by default you know the differential pressure it should be at. If the pressure is not the same as the time before then you know there is a problem, such as impeller corrosion or a clearance issue.. Thus is the purpose of the test.

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