I am writing this email looking forward for your technical advice in a specific situation.
Earlier this year we worked in a project, in which we didn’t provide the fire pump, at this moment, this new pump is not delivering the desirable pressure, but only at 150% capacity.
During the project, the client wanted to place the water tank 70-ft apart from the fire pump suction flange, we didn’t agree because of the negative pressure in the suction piping, so the client decided to elevate 3ft the water tank and keep the 70-ft apart, and now having -2.4 psi in the suction pump (this according to our friction loss calculation, considering an empty water tank).
a couple months ago, the fire pump supplier made its first fire pump testing having the next results:
Fire pump test:
The pump supplier claims that the suction piping arrangement has trapped air causing the effective piping diameter to decrease.
we have some options that may be causing this problem, including bad procedure during the fire pump test, semi-closed valves, unproper calibration of the measurement equipment, or obstructions on suction piping.
Suction Piping @ water tank
Hope you can help us with your comments