Nominal Diameter (DN)

Definition - What does Nominal Diameter (DN) mean?

Nominal Diameter (DN), in the context of trenchless technology, refers to the internal diameter of a pipe that has to be laid in a horizontally drilled bore hole. DN is of paramount importance in the process of pipeline laying, as this is what determines the size of pipe fittings such as bends, tees and elbows that are used for connecting pipes.

Trenchlesspedia explains Nominal Diameter (DN)

Any standard pipe is characterized by two numbers that are dimensionless. 1. Nominal Diameter (DN) in inches (USA) or mm (UK); 2. Schedule. Reference tables are used to arrive at the outside diameter and pipe thickness based on the nominal pipe size and schedule. Pipes are available in different DN sizes. DN does not necessarily indicate the exact internal diameter. The DN is used to arrive at the pipe dimensions using standard tables and schedules.

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