Negative pressure

• Less than atmospheric pressure.

N.P.S.H.A.

• The net positive suction head available to prevent cavitation of the pump. It is defined as: Atmospheric pressure + gage pressure + static pressure - vapor pressure - friction loss in the suction piping.

N.P.S.H.R.

• Net positive suction head required to stop a pump from cavitating. This number is given to you by the pump manufacturer. Since the number was generated by testing with cold fresh water, it can be lowered in some cases if you are pumping hot water or some hydrocarbons.

Newton

• A metric unit of force. Kilogram x gravity.

Newtonian fluid

• A fluid that does not change viscosity as it is agitated.

Non lubricant

• The fluid that will not maintain a film thickness of at least one micron at its operating temperature and load. A concern with mechanical sealing.

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