Centrifugal pump operation and characteristics

One of the most attractive features of a centrifugal pump is its ability to perform in a 

system under a wide range of operating conditions. 

Pumps are able to operate with satisfactorily under varying operating conditions and 

with a range of fluid types. These could be variations in: 

• Flow rate 

• Suction and discharge heads 

• Speed 

• Type of fluids handled and its many properties 

• Fluids with varying properties. 

The pump is designed for a discrete value of flow rate, differential head, and speed. 

This is the best efficiency point of operation or ‘BEP’. However, in  applications, 

the pumps are rarely operated at the operating parameters for which the pump has been 

designed. 

Among the parameters stated, the flow rate Q and differential head H of the pump vary 

a great deal during normal operation. 

Consider this case where a pump discharges into a delivery pipe that is connected to the 

bottom of a vessel situated at a certain height. As liquid is discharged into the vessel, 

the height of the liquid in the vessel increases and this increases the differential head 

that the pump has to generate. As the differential head H increases, the flow rate of the 

pump Q decreases. 

If in the above case, the power requirement increases then the load on the motor could 

result in a possible drop in speed of the prime mover. 

Other cases include where process and utility requirements to cover a greater range of 

flow rate and differential head may demand a simultaneous operation of multiple pumps 

within a single system. The performance of one pump in a common system is certainly 

affected by the behavior of the other pumps. 

Even though a pump may perform with wide variations in the parameters and 

conditions, the pump performance is not unaffected by these changes. 

It is therefore important to determine the behavior of the pump as it responds to the 

variation in the parameters under operating conditions that are different from parameters 

that were considered during the design of the pump.The basics of the pump hydraulics have been covered in chapter 3 and this chapter 

would cover the behavior of the pump in response to the changes in its environment. 

We may revisit some of the fundamentals covered in the earlier chapters to understand 

the variation in the behavior of the pump