NPSHa Ha Hs Hvp Hf Hi

1. To determine the Ha, atmospheric head, you only need observe the vessel being drained by the pump. Is it an opened, or vented atmospheric vessel? Or is it a closed and scaled vessel? If the vessel is open, then we begin with the atmospheric pressure expressed in feet, which is 33.9 feet at sea level. The altitude is important. The atmospheric pressure adds energy to the fluid as it enters the pump. For closed un-prcssurized vessels the Ha is equal to the Hvp and they cancel themselves. For a closed pressurized vessel remember that every 10 psia of pressure on a vessel above the vapor head of the fluid will add 23.1 feet of Ha. To the Ha, we add the Hs.

2. The Hs, static head, is the static height in feet observed from the level in the vessel to be drained to the centerline of the pump. If the

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