2006-07-21 22:35:29 · 2 answers · asked by Shahrzad T 1 in Science & Mathematics ➔ Engineering
NPSHr (or NPSHR) means Net Positive Suction Head Required). This likely is part of a pump specification and if you have this or more net positive suction head the pump will operate satisfactorily. With too little NPSH the pump may cavitate filling the pump with vapor cavities that will interfere with pump flow or even completely vapor bind the pump. Of course, the distance the eye of the pump is above the water surface it is taking suction on and the temperature of the water are important considerations in avoiding cavitation which can damage a pump's impeller or pump walls.
2006-07-22 00:57:53 · answer #1 · answered by Kes 7 · 0⤊ 0⤋
The NPSHr (NET POSITIVE SUCTION HEAD required) of the pump is the minimum NPSH allowed at the suction flange. It's a property of the pump. The NPSHa (NET POSITIVE SUCTION HEAD available), which is a property of the system, must be greater than NPSHr to avoid cavitation, because NPSHr considers the head loss from the suction flange to the impellers eye. So it must be NPSHa > NPSHr. Always.
Just to remember: NPSH = (Psuction - Pvap(T))/(density*g)
2006-07-22 15:40:05 · answer #2 · answered by Fabio 2 · 0⤊ 0⤋