Total Discharge Head

Total Dynamic Head The total dynamic head H of a pump is the total discharge head minus the total suction head h,. 

Before installation it is possible to estimate the total discharge head from the static discharge nead and the discharge friction head hj as follows ... 

This applies because the total head for a pump is total discharge head a( + ), minus ( —) the [suction head, a( + )J, or [suction lift, a( —)]. 

Note that the equivalent suction lift must be added to the total discharge head for the pump system to obtain the total system head. Keep in mind that the work the pump must accomplish is overcoming the suction losses (-f or —) plus the discharge losses, that is, + discharge loss (all) — (-f if head, or — iflift on suction losses, all). Thus, the suction lift becomes a ( — )( — ) or a ( + ) to obtain the total system head. Keep in mind that a vacuum condition on the suction of a pump never helps the pump, but in effect is a condition that the pump must work to overcome. 

Total Discharge Head. The pressure reading at the pump discharge in feet of liquid, corrected to a datum, plus the velocity head. 

Total Head. The algebraic difference between the discharge and suction heads. A suction lift is added to the total discharge head a positive suction head is subtracted from the discharge head. 

In pumps the difference between the heights of the suction and discharge connections is usually negligible, and Z and Zj, can be dropped from Eq. (8.1). If is the total suction head, H, the total discharge head, and AH = — Eq. 

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