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© 2013 Tuthill Corporation. All rights reserved. Tuthill confidential. Pump Hydraulics Terms and Definitions
© 2013 Tuthill Corporation. All rights reserved. Tuthill confidential.
Pump Hydraulics Terms and Definitions
© 2013 Tuthill Corporation. All rights reserved. Tuthill confidential.
Common Pump Terms & Definitions
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• Viscosity • Specific Gravity • Flow Rate • Pressure • Differential Pressure • Working Pressure • Vapor Pressure
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Viscosity Saybolt Universal Seconds (SSU)
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SSU = Centipoise cps × 4.55
Specific Gravity
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Viscosity Inverse Relationship With Temperature
As pumping temperature decreases, the viscosity increases
As pumping temperature increases, the viscosity decreases
4 Viscosity Te
mpe
ratu
re
Viscosity
Tem
pera
ture
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Specific Gravity • Ratio of the Relative Density of a Material
Compared to Water at 60°F (15 °C) • Specific Gravity of 1.0
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Flow Rate Gallons Per Minute (GPM) • Volume of Fluid, Not Weight • 1 US Gallon is 231 Cubic Inches / 1 m3/h = 0.59 cu ft/min • Rate Expressed as Volume per Unit of Time • Typically Gallons per Minute • Kitchen Faucet • One Gallon Pitcher • Pitcher Fills in One Minute • Flow Rate on Faucet = 1 GPM (0.22 m3/hr.)
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© 2013 Tuthill Corporation. All rights reserved. Tuthill confidential.
Flow Rate Conversion of Mass Flow to GPM
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GPM =Lb./Min.
8.33 × Specific Gravity
© 2013 Tuthill Corporation. All rights reserved. Tuthill confidential.
Pressure • Amount of Force Exerted on a Surface
Divided by the Area of the Surface • Pounds Per Square Inch (PSI)
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Conversion of Head to PSI
• Column of Water at 60º F (15 °C) • Open to Atmosphere • Filled with Water to
2.31 Feet (0.7 Meters) High • Water Height will Exert
1 PSI (.06 bar) of Pressure on the Bottom
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Conversion of Head to PSI Convert 1 Foot of Head to PSI
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PSI =Head in Feet × Specific Gravity
2.31
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Pressure
• Higher Specific Gravity Means Heavier Liquid • Heavier Liquid Means More Work • Higher Horsepower • Already Factored Into Pressure and PD Pump Curves
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PSI =Head in Feet × Specific Gravity
2.31
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Pressure Basics
• Zero Pressure Gauge = 14.7 PSI Absolute (at sea level) / 1.01 bar
• Absolute Pressure = Gauge + 14.7 • Add 14.7 PSI to Gauge Pressure for
Expression as Absolute Pressure, PSIA
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Differential Pressure • The difference between pump discharge
and suction pressure
• The work that the pump must do
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© 2013 Tuthill Corporation. All rights reserved. Tuthill confidential.
Working Pressure • The maximum system pressure that the
pump may see
• Pump must be designed to withstand working pressure
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© 2013 Tuthill Corporation. All rights reserved. Tuthill confidential.
Vapor Pressure • The pressure that the vapor of a liquid
exerts at a given temperature • Atmospheric pressure pushes liquid into
the pump suction • Vapor pressure acts to offset atmospheric
pressure
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Vapor Pressure • Vapor pressure of a liquid generally goes up with
temperature • Vapor pressure is a physical property that is specific
to liquids • Solvents and thin hydrocarbons generally have high
vapor pressures • Thick viscous liquids generally do not have high
vapor pressures
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Vapor Pressure Atmospheric Pressure at Sea Level is 14.7 PSIA
Vapor Pressure of Water Boiling at 212º F (100°C) is 14.7 PSIA (1.01 bar)
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Vapor Pressure of Various Liquids
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© 2013 Tuthill Corporation. All rights reserved. Tuthill confidential.
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