Calculators for Pumps, Piping, and Fitting

Head & Pressure Formula

Head in Feet

=

(Head in psi) x 2.31 (Sp. Gr.)

 

Head in psi

=

(Head in feet) x (Sp. Gr.) 2.31

Net Positive Suction Head

h_a = the absolute pressure in feed of liquid on the surface of the supply liquid
h_v = the vapor pressure of the liquid being pumped expressed in feet of head
h_s = the height in feed of the supply liquid surface with respect to the pump inlet
h_l = suction line friction losses express in feet of head
These calculations yield the available net positive suction head for a given system.
This must be compared to the required net positive suction head NPSHR calculated
by the manufacturer. NPSH_A must exceed NPSH_R.

Affinity Laws

Centrifugal Pumps

For constant speed:
D1 D2	=	Q1 Q2	=	√H1 √H2
BHP1 = (D1)3 BHP2 = (D2)3

 

For constant impeller diameter:
S1 S2	=	Q1 Q2	=	√H1 √H2
BHP1 = (S1)3 BHP2 = (S2)3

D = Impeller diameter in inches     H = Head in feet
S = Speeds in RPM     Q = Capacities in GPM
BHP = Brake Horsepower

Vacuum Pressure Equivalents:

1 Atmosphere = 29.92 in. Hg = 760mm Hg = 14.7 psi
1 mm Hg = 1 Torr = (3.937x10-2) in. Hg = 1000µ Hg = 1.333 millibars
1 bar = 103 millibars = 106 microbars = 750.06 mm Hg
1 microbar = 0.75 micron
1 inch Hg = 2.54 x 101 mm Hg
x in. Hg vacuum = (29.92–x) in. Hg absolute
y mm Hg vacuum = (760-y) mm Hg absolute
z PSIG = (z + 14.7) PSIA
w PSIA = (w-14.7) PSIG

PUMPING POWER FORMULA

Centrifugal pumps:
Brake hp	=	gpm x Hft x Sp. Gr. 3960 x Efficiency

 

Rotary and reciprocating pumps:
Brake hp	=	gpm x psi 1714 x Efficiency
KW	=	pump bhp x 0.7457 motor efficiency

GENERAL INFORMATION

1 HP = .746 KW or 746 Watts
GPM = Bbls. / Hr. x 0.70
GPM = Bbls. / Day x 0.2917
One Barrel Oil = 42 Gallons

VISCOSITY

Relationships

Centistokes

=

Centipoises Density

(usually the same as specific gravity)

ft² / sec = Centistokes x 1.07639 x 10^-5
Centistokes = ft² / sec x 92903.4

Approximate Conversions
(50 < SSU ± 100) Centistokes = SSU x 0.226 – 205.3 / SSU
(100 < SSU ≤ 350) Centistokes = SSU x 0.220 – 147.7 / SSU
(SSU > 350 @ 100° F) Centistokes = SSU x 0.21576
(SSU > 350 @ 210° F) Centistokes = SSU x .021426

FLOW

Lbs. Of Water / Hr x 0.002 = Gal Min.
Gal / Min. x 500 = Lbs of Water / Hr
 

Lbs of Fluid / Hr Specific Gravity

=

Gal Min.

Liter Min. x 0.264 = Gal / Min. (US)
GPM x 3.785 = Liters / Min.
Cu. Meters / Hr x 4.4 = Gal / Min. (US)
Gal / Min. x 227 = Cu. Meters / Hr
Kg of Water / Min. x 0.264 = Gal / Min. (US)
Gal Min. x 3.8 = Kg of Water / Min.

PRESSURE

Ft of Water x 0.433 = PSI
PSI x 2.31 = Ft of Water
Inches Hg. X 0.491 = PSI
Inches Hg. X 1.133 = Ft of Water
ATM x 14.7 = PSI
ATM x 33.9 = Ft of Water
Kg / Sq cm x 14.22 = PSI
Meters of Water x 1.42 = PSI
ATM x 760 = mm Hg.
mm Hg. X 0.39 = Inches Hg.
Bar x 14.5 = PSI
Newton / Meter2 x 1 = Pascal
PSI x 6.9 = kPa (Kilopascal)
kPa x 0.145 =PSI

VOLUME

Lbs Water x 0.119 = Gal
Gal (Brit) x 1.2 = Gal (US)
Gal x 128 = Fluid Ounces
Cubic Ft x 7.48 = Gal
Cubic in. x 0.00433 = Gal
Gal x 3.785 = Liters
Liter x 0.264 = Gal
Cubic Meters x 264.2 = Gallons
Cubic Meter x 1000 = Liters
Liters x 1000 = Cubic Centimeters
Cubic Centimeters x 0.338 = Fluid Ounces
Fluid Ounces x 29.57 = Cubic Centimeters

MASS

Gal of Water x 8.336 = Lbs
Cubic Ft of Water x 62.4 = Lbs
Ounces x 0.625 = Lbs
Kilograms x 2.2 = Lbs
Lbs x 0.454 = Kilograms
Metric Ton x 2205 = Lbs

LENGTH

Mils x 0.001 = Inches
Meters x 3.281 = Feet
Centimeters x 0.394 = Inches
Millimeters x 0.0394 = Inches
Microns x 0.0000394 = Inches