Minimum Allowable Pump Suction Pressure.
Px = Pa + (NPSHa - NPSHs) x S.G.
Feedwater pressure (absolute) at pump suction, psia
Minimum feedwater pressure (absolute) at pump suction,
PSIA, plus the difference between NPSHa and NPSHs.
NPSH available in feet of liquid of system at shut-off
(Usually static suction head if water in heater is at its
vapor pressure point.)
NPSH in feet of liquid required of pump at shut-off.
Specific gravity of feedwater at pumping temperature.
(b) Maximum Allowable Temperature Rise Across the Pump:
R = Ts - Ti
Allowable temperature rise in degrees F.
limited to 15 degrees F (8.3 degrees C).
Temperature in degrees F corresponding to saturation
temperature of P.
Temperature in degrees F of feedwater at inlet of pump.
Temperature rise and by-pass requirements to prevent damage to the
pump due to cavitation are generally available from the manufacturer.
(c) Minimum Pump Flow
BHP x 5.1
R x S.G. x S
By-pass capacity in gpm
Maximum allowable temperature rise degrees F.
Specific heat of liquid.