Nominal Pipe Size
The nominal width is defined as the inner diameter of a pipe / hose line or the size / Connection dimension of a valve (valve, valves). Together with the nominal pressure rating and material class by specifying the nominal width of all dimensions of a pipe, for example, flange dimensions, fixed. Frequently steel is not mentioned as a material, but provided.
Note that the actual internal diameter of the nominal diameter often deviates by several millimeters. One can assume that it is possible tubes from different manufacturers only with certainty when the indication of the nominal diameter DN ( diameter nominal ) is done with reference to the same DIN standard.
The deviations occur among others, as the wall thicknesses of the traditionally used for plumbing installations steel tubes grow with increasing pressure level inside, ie the free cross section decreases. Since then the outer diameter remains constant, can be cut to all tubes with the same nominal size the same thread. This can be used for all pressure levels and the same pipe -joints (fittings ).
Only for very thick-walled pipe for high pressure, the outer diameter grows. The same applies to cables made of glass fiber reinforced plastic ( mostly resin ): These are wound around a mandrel or a plastic tube ( " inline " ), and therefore must grow outward here, the wall thickness.
The indication of the nominal diameter in accordance with EN ISO 6708 followed by approximately the inner diameter in millimeters corresponding dimensionless number by the name DN ( engl. Diameter Nominal ). ( Thus internal diameter 53 mm) tube with the outer diameter of 60.3 mm and a wall thickness of 3.65 mm; For example, denotes DN 50 according to EN 10255 ( moderate threaded pipes formerly DIN 2440 ).
According to ANSI, the nominal width in " NPS " is ( Nominal Pipe Size ) in inches. A pipe NPS 2 " is roughly equivalent to the nominal size DN 50
Threaded pipe EN 10255 (medium hard steel) ( boiling tube )
For threaded pipes, the pipe size is usually stated in inches. In copper tubes usually is the outer diameter in mm (10, 12, 15, 18, 22, 28, 35, 42, 54, 64, etc.) specified; The pipe wall thickness of 10-22 mm 1 mm, 1.5 mm at 22-42 and at 54 64 2 mm.