Glossary of Compressed Air Terms :: N :: Glossary Index A B C D E F G H I J K L M N O P Q R S T U V W X Y Z N cu m/min N cu m/hr Volume flow rate measured in normal cubic metres per minute (or hour), i.e. related back to normal inlet conditions Natural frequency A projecting aperture at the end of a tube, pipe etc. serving as an outlet for compressed air. Reduces the demand on the compressor by generating the highest thrust and volume for the lowest possible air consumption. N.B. ACRONYM - National Board of Boiler and Pressure Vessel Inspectors. NEC ACRONYM - National Electrical Code Needle gauge A measuring tool used to check air pressure at the tool by inserting a hypodermic needle into the rubber hose. Needle scaler A hand held pneumatic chipping tool which the blows are transmitted through a group of floating needles or metal rods. Negative pressure A pressure below that of the existing atmospheric pressure taken as a zero reference. NEMA ACRONYM - National Electrical Manufacturers Association. NFPA ACRONYM - National Fluid Power Association. NL ACRONYM - non-lubricated compressor. NM³/HR Unit of free air flow rate. Normal cubic meter per hour. The air in the following conditions:1.013 bar(a) of pressure; 0 degrees Celsius of temperature and 0% of relative humidity . No load The air compressor continues to run, usually at full RPM, but no air is delivered because the inlet is either closed off or modified, not allowing inlet air to be trapped. Nominal efficiency An arbitrary filter efficiency rating. Nominal filter rating Filter rating indicating the approximate particle size for which the majority will not pass through a given filter. It is generally interpreted as meaning that 85% of the particles of size equal to the nominal filter rating will be retained by the filter. Nominal micron rating A term that means that 98% of all particles larger than a stated micron size have been removed from the product being filtered through the filter element. Noncondensables Are those constituents in the suction gas that cannot be condensed to a liquid with the cooling medium available. Noncooled compressor cylinders Reciprocating type compressor used mainly in oil and gas field applications. The compressor cylinders operate at low compression ratios and experience small temperature rise. Noncorrosive gas Is one that does not attack normal materials of construction. Nonlubricated compressor A compressor designed to compress air or gas without contaminating the flow with lubricating oil. Piston rings and packing are usually made of TFE-based materials or carbon or other synthetic material that operate without lubrication. Normal air Is the term used for average atmospheric air at sea level in a temperature zone where it contains some moisture. It is defined in the ASME Test Code For Displacement Compressors as being at 14.696 psiA, 68 °F, 36% RH and weighing 0.075 lb/cu ft. The k value is 1.395. Nozzle A projecting aperture at the end of a tube, pipe etc. serving as an outlet for compressed air. Reduces the demand on the compressor by generating the highest thrust and volume for the lowest possible air consumption. Nozzle (valves) The stationary seating surface, the inlet of a valve. NPT ACRONYM - National Pipe Thread standard. A description of a specific pipe thread NPTT ACRONYM - National Pipe Thread tapered. A description of a specific pipe thread Glossary Index A B C D E F G H I J K L M N O P Q R S T U V W X Y Z