Pump Total Differential Head

Let us consider a system curve of a pump system.

 A misconception of the total system head can either decrease the output i.e., flow rate 

or runs the flow out of the pump hydraulics.

 

Hence the estimation of TDH plays a vital role prior to the pump sizing. 

 

The total differential head has two components, Discharge Head and Suction Head. 

It is basically  a difference between the total discharge head and total suction head

 

Now let's look at the suction head

 

Suction head has three components in their calculation, static suction head (hss), pressure head ( hps) &  friction loss head at suction (hfs)

 

Where

 

Static suction head is the elevation height from the suction level to the suction flange.

 

If the suction is from the below the centreline of the pump, then it is called suction lift and it is expressed in a negative value.

 

Then the surface pressure at the inlet side. It is zero for atm tank/ sump

 

Then friction loss at suction which can be due to the elbows or due to valves and fittings.

 

Similarly , Total Discharge head has components such as  static discharge head, pressure head required at discharge and friction loss from the discharge flange to the destination.

 

In the next segment, we are going to look at NPSH and its significance on pump design.

If you would like to listen to this segment, the above link is for you to understand the concept a bit better. 

 

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