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Calculators

Calculators will help you to properly size up your pump, piping and fittings. With these tools, you can determine suction loss, friction loss, specific gravity, along with the useful conversion tables.

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

Suction Lift:
NPSH = ha – hv – hs – hl
Flooded suction:
NPSH = ha – hv + hs – hl

ha = the absolute pressure in feed of liquid on the surface of the supply liquid

hv = the vapor pressure of the liquid being pumped expressed in feet of head

hs = the height in feed of the supply liquid surface with respect to the pump inlet

hl = 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. NPSHA must exceed NPSHR.

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

MASS

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

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