Specifying Pump Head or Discharge Pressure

This has always been an issue all the while .Users tend to give pump head without actually determining the correct discharge head .For convenient purpose ,we will assume the head as
correct and this often leads to problems like motor tripping etc

What will happen ?
When the actual system head is 30 M instead of 60 M , the pump will be operating on the
extreme right of the curve ,maximum flow and low head ( 140 m3/hr at 30 m instead of
90 m3/hr at 60 M)

The result
a) 90 m3/hr at 60 M, the BHP is approx 40 Hp
b) 140 m3/hr at 30 M , the BHP is 55 HP

For the case ,you can either trim the impeller to smaller diameter
or Throttle the discharge valve ( never throttle the suction line )

This pump is open Impeller Slurry pump and supplied with 60 Hp motor 2900 rpm
A 40 hp could be used if the head is 30 M ( 90 m3/hr at 30 M

Take note the power difference

It must be emphasize that giving the actual operating head is extremely important
much saving can be made from

a) smaller pump being used
b) Pump can operate at 1450 rpm instead of 2900 rpm if head is low ,lower wear& tear
c) smaller motor Kw and in long run energy saving
d) long term lower maintenance cost for smaller pumps