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Centrifugal pump Calculations

Formulas & Calculations

How to Calculate...

  • Head Calculation
  • Hydraulic power calculation
  • Pump Shaft Power
  • Electrical Power
  • Specific Speed
  • Centrifugal Pump Calculations Energy loss in discharge valve throttling
  • NPSHa - Net Positive Suction Head Available
  • Head ↔ Pressure
  • Volumetric flow ↔ Mass flow
  • Break Power Calculation

Formulas

Head

Head is net work done for unit weight of water.

Head of pump

H = Head ; Unit - Meter
P = Water Pressure ; Unit - kPa, psi
Γ = Specific weight of Fluid ; Unit - kN/m³
V = Water Velocity ; Unit - m/s
g = Gravitional force ; Unit = m/s² Value = 9.8m/s²
Z = Elevation to be lift

Horizontal pump - Datum is a horizontal plane from center line of shaft

Vertical pump - Datum is horizontal plane of impeller eye.

See calculations

Pump Capacity ( Volume flow rate of pump)

Capacity is the amount of water pumped per unit time.

Capacity Q = A V

A = Area of pipe
V = Volume flow rate

See calculations

Hydraulic power calculation

Hydraulic power calculation

⍴ = densityGravitional force of fluid ; Unit = kg/m³
g = Gravitional force ; Unit = m/s² Value = 9.8m/s²
H = Total Head = Hd - Hs; Unit = m
Hd = Discharge head
Hs = Suction head
Q = Discharge flow ; Unit = m³/hour

See calculations

Pump Shaft Power

Pump shaft power calculation
ηpump = Pump efficiency

Maximum shaft power 

Mmax = ɑ1 ⍴ g H Q / η0

See calculations

Electrical Power

Pump power requirements
ηmotor = Motor efficiency

See calculations

Pump Efficiency

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