ND factor - another name for DN factor. See DN factor.
Net Positive Suction Head Available (NPSHA) - the total absolute suction pressure, minus the vapor pressure, expressed in the unit of head (feet) of the pumped liquid, and referred to a datum elevation. The datum elevation is usually the impeller centerline on a horizontal pump, and either the suction nozzle centerline or top of foundation on a vertical pump. See NPSHR
Net Positive Suction Head Required (NPSHR) - the net positive suction head (NPSH) required by a pump without impairing its performance due to cavitation. Impairment is said to occur when the pump suffers a loss of head equal to 3% of the head of the first stage impeller at a given flow rate. The NPSHR is usually referred to the impeller centerline. See NPSHA.
Newtonian liquid - a liquid whose viscosity is independent of the rate of shear at a given temperature. Shear is the movement of one layer of liquid relative to another layer when a shearing force is applied. Examples of Newtonian liquids are water and light oil. See non-Newtonian liquid.
Non-Newtonian liquid - a liquid whose viscosity is dependent on the rate of shear at a given temperature. Shear is the movement of one layer of liquid relative to another layer when a shearing force is applied. Examples of non-Newtonian liquids are paint, grease, molasses, clay slurries, etc. See Newtonian liquid.
Normal operating point - the point at which the pump operates most of the time, or under normal operating conditions. This is different from the rated operating condition which is the point at which the pump performance is guaranteed by the pump vendor subject to the performance tolerance of the applicable standard or user specification.
Nozzle head - the part of a vertical barrel pump that contains the suction and discharge nozzles, and where the driver is mounted. The nozzle head is mounted on top of the barrel.
NPSHA - see Net Positive Suction Head Available.
NPSHR - see Net Positive Suction Head Required.
NPSHR3 - the net positive suction head required by a pump based on three percent (3%) head loss.