Nominal pressure

from Wikipedia, the free encyclopedia

The nominal pressure is a reference value for pipes and fittings .

The specification is made according to DIN, EN, ISO by the designation PN ( Pressure Nominal ) followed by a dimensionless whole number, which indicates the design pressure in bar at room temperature (20 ° C).

According to EN 1333, certain nominal pressure levels are specified: PN 2.5 - PN 6 - PN 10 - PN 16 - PN 25 - PN 40 - PN 63 - PN 100 - PN 160 - PN 250 - PN 320 - PN 400.

A pipeline with the maximum permissible pressure of 10 bar at a fluid temperature of 20 ° C would therefore be marked as "PN 10". On (older) valves there is occasionally the indication "ND 10" instead as an abbreviation for "nominal pressure of 10 bar".

After the nominal pressure , the set wall thickness of pipes as well as the design and dimensions of links and connections. By specifying the nominal pressure level PN and nominal diameter DN, the interchangeability of pipeline components such as fittings , flanges and valves is guaranteed.

Plastic pipes are often available in different pressure levels, each with an adapted wall thickness.

In American standards ( ASME B 16.5) and now alternatively also in European standards, the designation "Class" can be used instead of "PN". The class designation specifies a load capacity by specifying specified pressure / temperature combinations. The specification Class 150 (150 psi ) roughly corresponds to a permissible pressure load (depending on the material class) at 100 ° F of approx. 16.3 to 20.0 bar (1.63 to 2.0 MPa). ASME pressure ratings refer to a higher reference temperature than the PN standard. Therefore, a Class 150 pipeline can be loaded with a higher pressure under nominal pressure conditions.

At higher temperatures, the permissible pressure is lower, due to the decrease in the permissible material parameters ( yield point ). The operating pressure permissible at a certain temperature is often given as a percentage of the nominal pressure.

Relevant standards:

  • EN 1333: Definition and selection of PN
  • EN 1092-1 steel flanges with PN designation
  • EN 1759-1: Steel flanges with class designation
  • EN 1514-1 to 8: Gaskets for flanges with PN designation
  • EN 12560-1 to 7: Seals for flanges with class designation
  • ASME B16.5 pipe flanges

See also


  1. ^ Franz Schwedler: Handbook of Pipelines: General Description, Calculation, Production ... , P. 185, Springer Verlag