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
