Pump efficiency measures how well the pump converts electrical power to useful work moving the water.
Pump efficiency = power output/power input
Pump efficiency = Hydraulic power, Ph/Power input to the shaft x 100
Steps for find out pump efficiency are given below:
Step 1. Measure flow rate
The following are the methods for flow measurements:
- Installation of an on-line flow meter
- Ultrasonic flow measurement
- Tank filling method
Flow rate (Q) = cum fluid pumped / time in seconds
Step 2. Determine discharge head
This is taken from the pump discharge side pressure gauge. Discharge head, is the pressure read from the pressure gauge fitted at the pump when the system is at full operational pressure.
Step 3. Determine suction head
Suction head is the distance between the centre line of the pump and the water level plus losses in the suction pipe. This is taken from the pump inlet pressure gauge readings and the value to be converted in to meters (1kg/cm2 = 10. m). If not the level difference between sump water level to the center line of the pump.
Step 4. Determine total head
Total head (Hd-Hs) is discharge head minus suction head.
Step 5. Determine motor efficiency
Electric motors have an efficiency (Me). During running, they lose some of the energy going into them as heat. This energy loss changes with the size of the motor and the load on the motor.
Step 6. Determine motor input power
Measurement of motor input power The motor input power Pm can be measured by using a portable power analyzer.
Step 7. Determine Pump shaft power
The pump shaft power Ps is calculated by multiplying the motor input power by motor efficiency
at the existing loading.
Ps = Pm x Me
Step 8. Calculate pump efficiency
ηPump = Ph/Ps
Hydraulic power, Ph (KW) = Q x (Hd-Hs) x Density x g/1000
Where,
Q = volume flow rate, cum/sec
Density = density of fluid, Kg/cum
g = acceleration due to gravity, m/square sec
(Hd-Hs)= total head in mtrs
Step 2. Determine discharge head
This is taken from the pump discharge side pressure gauge. Discharge head, is the pressure read from the pressure gauge fitted at the pump when the system is at full operational pressure.
Step 3. Determine suction head
Suction head is the distance between the centre line of the pump and the water level plus losses in the suction pipe. This is taken from the pump inlet pressure gauge readings and the value to be converted in to meters (1kg/cm2 = 10. m). If not the level difference between sump water level to the center line of the pump.
Step 4. Determine total head
Total head (Hd-Hs) is discharge head minus suction head.
Step 5. Determine motor efficiency
Electric motors have an efficiency (Me). During running, they lose some of the energy going into them as heat. This energy loss changes with the size of the motor and the load on the motor.
Step 6. Determine motor input power
Measurement of motor input power The motor input power Pm can be measured by using a portable power analyzer.
Step 7. Determine Pump shaft power
The pump shaft power Ps is calculated by multiplying the motor input power by motor efficiency
at the existing loading.
Ps = Pm x Me
Step 8. Calculate pump efficiency
ηPump = Ph/Ps
Hydraulic power, Ph (KW) = Q x (Hd-Hs) x Density x g/1000
Where,
Q = volume flow rate, cum/sec
Density = density of fluid, Kg/cum
g = acceleration due to gravity, m/square sec
(Hd-Hs)= total head in mtrs
Efficiency of pump, ηPump = Ph/Ps
Where, Ps = Pm x Me
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