This is a quick Overview of the Most common operating formulas in the pump industry:
TOTAL DIFFERENTIAL HEAD (THD)
System Head = total discharge head – total suction head
H = hd – hs
hd = hsd + hpd + hfd hs = hss + hps = hfs
hd = total discharge head hs = total suction head
hsd = discharge static head hss = suction static head
hpd = discharge surface pressure hps = suction surface pressure
hfd = discharge friction head hfs = suction friction head
AVAILABLE NPSH
Available NPSH is “the difference between the total suction head and the vapor pressure of the liquid, in feet of liquid, at the suction flange.”
hsv = hsa – hypa
hsv = available net position suction head, in feet of liquid
hsa = total suction head, in feet of liquid, absolute
hypa = vapor pressure of liquid at suction nozzle, in feet of liquid, absolute
Pressure Conversion
Head (ft.) = psi x 2.31 / sp. gr.
PSI = head (ft.) x sp. gr. / 2.31
Lbs./sq. in. = In. of Mercury x .491
Lbs./sq. in. = Atmospheres x 14.7
mm hg. = Atmospheres x 760
Viscosity
Centistokes x 4.64 = SSU(approx.)
Centipoise Sp. Gr. = Centistokes
Flow
Gallons per minute (GPM) x 3.785 = Leters per minute
Temperature Conversion
°C = 5/9 (°F – 32)
°F = 9/5°C + 32
Specific Gravity
sp. gr. = weight of liquid
sp. gr. = weight of water
weight of water = 62.4 Lb./cu.
weight of water = 8.3 Lb./gal.
Power
BHP = GPM x TDH x sp. gr.
BHP = 3960 x Eff.
BHP = GPM x PSI
BHP = 1715 x Eff.
KW = 0.746 x H.P.
Torque = (Ft. Lb.) = HP x 5260
Torque = (Ft. Lb.) = RPM
HP = E(volts) x I(Amps) x Eff. X P.F. x 1.732
HP = E(volts) x I(Amps)746
I(amps) = HP x 746
I(amps) = E(volts) x Eff. X P.F. x 1.732
O-Ring Temperature Limitations
Polytetrafluorethylene [TM]
Low: -100 °F (-73 °C) High: 300 °F (149 °C)
Viton [VA]
Low: -20 °F (-29 °C) High: 400 °F (204 °C)
Perfluoroelastomer (Kalrez) [KAL]
Low: -36 °F(-38 °C) High: 550 °F (287 °C)
