SOLUTION

Centrifugal pumps are the prime fluid movers in membrane plants for liquid separations. In general, centrifugal pumps are used in moderate-to-high flow under low-head conditions and operate within the rated ranges of head and velocity.

Pump specifications depend on process requirements, for example, fluid flow rate determines the capacity of the pump whereas pump head depends on fluid density and viscosity. A pump head is commonly used as a measure of energy.

Pump selection criteria

Material and energy balances are used to calculate the required flow rate while the maximum pump pressure or ‘shutoff pressure is the maximum pressure a pump will develop under no-flow conditions, e.g, when the pump outlet line is fully blocked The amount of work needed to drive the pump, increases with increase in fluid density and viscosity. The maximum values of these properties usually occur during start-up, shut down, and process upsets.

Centrifugal Pump Water horse power= Q x H x S.G./3960,

where

Q = flow rate,

H = head,

S.G. = Specific gravity.

Hence from the above equation, it is clear that the flow rate is directly proportional to the water horsepower hence if we double the flow rate then the horse-power will also get doubled.