# Pump performance assessment

Pump performance assessment

1 How would you measure the flow by using tracer method?

2 What are the various ways of measuring flow?

3 A pump motor draws 75 A current. The voltage is 415 V. Assuming a power factor of 0.9. Calculate the power drawn?

4 The suction head is 1m below the pump centerline. The discharge pressure shows 3 kg/cm2. The flow is calculated to be 100 m3/hr. Find out the pump efficiency.

5 The pump efficiency is 70%. The hydraulic power is calculated to be 22 kW. Find out the motor power required to drive the pump.

### Purpose of the Performance Test

• Determination of the pump efficiency during the operating condition

• Determination of system resistance and the operating duty point of the pump and compare the same with design.

### Performance Terms and Definitions

Pump Capacity, Q = Volume of liquid delivered by pump per unit time,m3/hr or m3/sec

Q is proportional to N, where N- rotational speed of the pump

Total developed head, H= The difference of discharge and suction pressure

The pump head represents the net work done on unit weights of a liquid in passing from inlet of the pump to the discharge of the pump.

There are three heads in common use in pumps namely

The frictional head in a system of pipes, valves and fittings varies as a function (roughly as the square) of the capacity flow through the system.

System resistance: The sum of frictional head in resistance & total static head.

Pump Efficiency: Fluid power and useful work done by the pump divided by the power input in the pump shaft.

### Field Testing for Determination of Pump Efficiency

To determine the pump efficiency, three key parameters are required: Flow, Head and Power. Of these, flow measurement is the most crucial parameter as normally online flow meters are hardly available, in a majority of pumping system.

The following methods outlined below can be adopted to measure the flow depending on the availability and site conditions.

### Flow Measurement, Q

The following are the methods for flow measurements: