Answer / vinay mishra

Every pump ie designed on certain temp. of liq. further at
certain vapour pressure of liquid . if pressure at suction
line of pump becomes low means pressure reduce below vapour
pressure then cavity or coalapse of bubble will occour on
eye of impellor this phenomenon is called as cavitation ,
if their will cavitation in pump following event occour
1. it can harm the vanes of impellor
2. viberation or noise can reduce bearing or seal life
3. it reduce the pump performance
so to avoid above event the pressure will be alaways
exceeds some value above vapour pressur in the suction line
of pump , npsh is a characteristic of pump design
so NPSH is define as difference of net suction head and
head due to vapour preessure.
so NPSH is alaways greater than NPSHR

Answer / ganesh r.k

Net positive suction head(NPSH)

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