How do you calculate the efficiency of a pump?
Efficiency of the pump is the ratio of output power to the
input power
Pump efficiency = Output power X 100 / Input power
Centrifugal pumps efficiency varies from 40% to 95% well.
Pump efficiency is equal to the power of the water/liquid
produced by the pump divided by the pump’s shaft power input.
A pump’s output power is determined by how much water and how much pressure it delivers
On what factors pumps efficiency depends on?
Pumps efficiency depends on
- In put power
- Output power
- Type of liquid
- Fluid temperature
- Flow
- Suction & discharge head
- Losses & leakages
- Fluid viscosity
- Pump operating load
- Pumps internal frictions
What do you mean by volumetric efficiency of a pump?
It is the ratio of actual flow delivered by the pump to the
theoretical flow
How do you calculate the Mechanical or hydraulic efficiency of
the pump?
Mechanical/Hyd.efficiency = Pump output power X 100 / Pump
input power or pump shaft power
Mechanical efficiency is also calculated as
= Theoretical torque required
to drive the pump X 100 / Actual torque provided to drive the pump
Calculations:
A centrifugal pump delivers 0.2 m3/sec flow
at total head 27 m, calculate its hydraulic power. Assume density of water 995
kg/m3
Pump hydraulic power = Pump flow in m3/sec X pump total head
in meter X Fluid density in kg/m3 X 9.81 m/sec2 / 1000
Pump hydraulic power = 0.2 X 27 X 995 X 9.81 / 1000
Pump hydraulic power = 52.7 KW
A centrifugal pump of capacity 0.05 m3/sec
flow has to lift the water from 3.5 m deep well & has to discharge the
water at 45 meter height. Calculate the pump efficiency if its shaft power is 30
KW
Assume water density 998 kg/m3
Pump hydraulic power = Pump flow in m3/sec X pump total head
in meter X Fluid density in kg/m3 X 9.81 m/sec2 / 1000
Total head = Discharge head + Suction lift
Total head H = 45 + 3.5 = 48.5 meter
Pump hydraulic power = 0.05 X 48.5 X 998 X 9.81 / 1000
Ph = 23.74 KW
Pump efficiency =Pump hydraulic power X 100 / Pump shaft
power
Pump efficiency =23.74 X 100 / 30
Pump efficiency =79.13%
A centrifugal pump of delivering 0.65 m3/sec flow at 75 meter discharge head,
pump has positive suction head around 2.7 meter from overhead tank.Pump efficiency
is 59%, calculate the motor input power if efficiency power if efficiency of
motor is 92.5%.
Assume water density 1000 kg/m3
Pump hydraulic power = Pump flow in m3/sec X pump total head
in meter X Fluid density in kg/m3 X 9.81 m/sec2 / 1000
Total head = Discharge head -Suction head
Total head H = 75 -2.7 = 72.3 meter
Pump hydraulic power = 0.65 X 72.3 X 1000 X 9.81 / 1000
Ph = 461 KW
Pump efficiency =Pump hydraulic power X 100 / Pump shaft power
= Ph X 100 / Ps
59 =461 X 100 / Ps
Ps = 781.35 KW
Motor efficiency = Pump shaft power X 100 / Motor input
power =Ps X 100 / Pm
92.5 = 781.35 X 100 / Pm
Pm = 844.7 KW
A centrifugal pump of efficiency 63% develops hydraulic
power 27.5 KW, calculate the motor efficiency if motor input power is 45 KW
Pump shaft power, Ps = Pump hydraulic power Ph / Efficiency
of pump
Ps = 27.5 / 0.63 =43.65 KW
Motor efficiency = Pump shaft power X 100 / Motor input power
Motor efficiency= 43.65 X 100 / 45
Motor efficiency = 97%
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