Example 3-8 Closed System Steam Surface Condenser NPSH Requirements

This is a closed steam surface condenser system with condensate being pumped out to retreatment facilities. From the conditions noted on the diagram, 

Friction loss in suction line side = 2.92 ft Absolute pressure in condenser = p = 1.5 in. Hg Abs 

The suction head or lift for the pump (separate calculation from NPSHA) is  

Applied Process Design for Chemical and Petrochemical Plants 

Note that the equivalent suction lift must be added to the total discharge head for Lhe pump system to obtain the total system head. Keep in mind that the work the pump must accomplish is overcoming the suction losses (+ or -) plus the discharge losses, that is, + discharge loss (all) — (+ if head, or — if lift 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 Lhe pump must work to overcome. 

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Example 3-8 Closed System Steam Surface Condenser NPSH Requirements, Use Figure 3-44... 

Example 3-6 NPSH Available in Vacuum System, 191 Example 3-7 NPSH. Available in Pressure System, 191 Example 3-8 Closed System Steam Surface Condenser NPSH Requirements, 191 Example 3-9 Process Vacuum System, 192 Reductions in NPSHr, 192 Example 3-10 Corrections to NPSHr for Hot Liquid Hydrocarbons and Water. 192 Example 3-9 Process Vacuum System, 192 Example 3-10 Corrections to NPSHr for Hot Liquid Hydrocarbons and Water, 192 Example 3-11 Alternate to Example 3-10, 194 Specific Speed,... 

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