What does DN mean for pipes?

DN (nominal diameter) is a dimensionless key figure for the approximate inside diameter of a pipeline, e.g. DN 100. It serves to match components that belong together.

What is the difference between PN and Schedule?

PN describes the pressure rating (permissible nominal pressure, e.g. PN 16 = 16 bar), Schedule describes the wall thickness of the pipe to ASME (e.g. Sch. 40).

DN, PN and Schedule: pipe key figures simply explained

Anyone ordering pipes, flanges and fittings constantly comes across three abbreviations: DN, PN and Schedule. They ensure that components from different manufacturers fit together. We explain what lies behind them.

DN – the nominal diameter

DN stands for "Diamètre Nominal", i.e. the nominal diameter. It is a dimensionless key figure for the approximate inside diameter of a line – for example DN 100. The number does not correspond exactly to a millimetre measurement, but serves to clearly match components that belong together (pipe, flange, bend, valve).

PN – the pressure rating

PN stands for "Pression Nominale", the nominal pressure rating. PN 16 means the component is designed for 16 bar at reference temperature. Important: as the temperature rises, the permissible operating pressure falls. Common ratings in piping construction are PN 6, PN 10, PN 16, PN 25 and PN 40; in high-pressure and power plant applications up to PN 100 and above.

Schedule – the wall thickness

While DN and PN come from European standardisation, Schedule (Sch.) comes from the American system (ASME B36.10 for steel, B36.19 for stainless steel). The Schedule number describes the wall thickness of a pipe at a given outside diameter – such as Sch. 40 or Sch. 80. The higher the number, the thicker the wall and the higher the pressure capacity.

How the key figures work together

In practice they are combined: a specification such as "DN 100 / PN 16" describes a line with around 100 mm nominal diameter for 16 bar. When wall thickness comes into play, Schedule or a specific wall thickness in millimetres is added. Anyone stating nominal diameter, pressure rating and material in an enquiry quickly receives a reliable quote.