NPSH Safety factor of chemical pumps
Chemical process pump
Chemical process pumps usually have the following characteristics: they often operate at different flow rates, use impeller with anti cavitation materials and relatively low NPSHa.
Considering these conditions, the following minimum NPSH margins are recommended for chemical process pumps:
a) For pumps with suction specific speed less than 210 metric units (11000 US units), the minimum margin ratio for each specific flow is 1.1 or 0.6 meters, whichever is greater, when operating in the AOR.
b) For pumps with suction specific speed ≥ 210 metric units (11000 US units), the minimum margin ratio is 1.1 or 0.6 meters for each specific flow, whichever is greater; for pumps frequently operating outside the por (but within the AOR), the NPSH margin ratio for each specific flow shall be 1.2 or 1.0 meters, whichever is greater.
Power plant (non nuclear) pumps: The pump for power plant is water pump. Different from hydrocarbon liquid treated by oil pump, cold water will expand rapidly when evaporated (flashed). When the steam bubble with higher destructive energy breaks, it will lead to higher impact speed and serious damage to pump parts; and the characteristics of hot water are similar to hydrocarbon liquid.
