Nominal pipe size. In 1862, Robert Briggs (superintendent of Philadelphia “Pascal Iron Works”) had the task of drawing up some specifications for iron pipes. And he using specifications of his company nuts. Later, he sent these specifications to all the companies in the area which could adapt to this “Standard Briggs”.
What is the nominal pipe size?
Nominal Pipe Size (alias NPS) is a North American set of standard sizes for pipes used for high or low pressures and temperatures. “Nominal” refers to pipe in non-specific terms and identifies the diameter of the hole with a non-dimensional number. Specific pipe is identified by pipe diameter and another non-dimensional number for wall thickness referred to as the Schedule. NPS is often incorrectly called National Pipe Size, due to confusion with national pipe thread (NPT).
The European and international designation equivalent to NPS is DN (diamètre nominal/nominal diameter/Durchmesser nach Norm), in which sizes are measured in millimetres, see ISO 6708. The term NB (nominal bore) is also frequently used interchangeably with NPS.
Do you k
now what this values represents?
The Nominal pipe size is related to :
- metallic and cement materials: for the nominal internal diameter value of the element
- plastic materials: for the nominal outer diameter value.
But this fact doesn’t match the value in millimeters of:
- internal diameter
- outer diameter
In fact, the nominal diameter value hasn’t unit of measure.
Therefore, it is always necessary to indicate the value of the same nominal diameter, prefixed with DN. So you don’t run into misunderstandings relating to units of measurement. Furthermore, two elements (in order to be directly coupled) must have not only the same nominal diameter (DN) but also the same nominal pressure. (PN)
In practice, the nominal pipe size.
But as shows the nominal diameters. These are indicated by the abbreviation DN followed by a numerical value.
For example you are referring to:
- DN/ID SERIES: if the hydraulic component is sized according to its standardized internal diameter (for example, you must indicate DN / ID for stainless steel tubes)
- DN/OD SERIES: if the component is sized as a function of its standardized outer diameter.
How should the manufacturer must be have?
It should always indicate whether the DN refers to the series DN / ID or DN / OD. However, you will need also to know the thickness for other diameters.
For this reason, it is essential to have the diameter and the nominal pressure.
(All the various sizes, from the American designation to the European too are set out in Table below)
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