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The Story Behind Nominal Pipe Size March 9, 2006

Therefore, the dimensional requirements of ASME B36.10 apply to stainless steel pipe of the sizes and schedules not covered by ASME B36.19. Pipes with suffix " S" have in that range thinner wall ticknesses.ĪSME B36.19 does not cover all pipe sizes. Schedule 10, 40 and 80 are in many cases the same as schedule 10S, 40S and 80S.īut watch out, from NPS 12 - NPS 22 the wall thicknesses in some cases are different. Schedule 40 and 80 approaching the STD and XS and are in many cases the same.įrom NPS 12 and above the wall thickness between schedule 40 and STD are different, from NPS 10 and above the wall thickness between schedule 80 and XS are different. The inside diameter is determined by the wall thickness ( WT). Such as above defined, no inside diameter corresponds to the truth 1" (25,4 mm). = 12.3/4" (323.9 mm)Īctual inside diameters of a 1 inch pipe. I'm really curious how people in other countries indicates a pipe. In this case, the Dutch talking about a "8 duimer". NPSįor NPS ≥ 4, the related DN = 25 multiplied by the NPS numberĭo you now what is "ein zweihunderter Rohr".Germans means with that a pipe NPS 8 or DN 200. Below a table with equivalents for NPS and DN pipe sizes. For example, DN 80 is the equivalent designation of NPS 3.

It indicates standard pipe size when followed by the specific size designation number without a millimeter symbol. The International Standards Organization (ISO) also employs a system with a dimensionless designator.ĭiameter nominal ( DN) is used in the metric unit system. Sizes without an " S" suffix are to ASME B36.10 which is intended for carbon steel pipes.

Note that stainless wall thicknesses to ASME B36.19 all have an " S" suffix. Stainless Steel Pipe dimensions determined by ASME B36.19 covering the outside diameter and the Schedule wall thickness. Pipe size is specified with two non-dimensional numbers,Īnd the relationship between these numbers determine the inside diameter of a pipe. The inside diameter will depend upon the pipe wall thickness specified by the schedule number. For NPS 14 and larger, the NPS is equal to 14inch.įor a given NPS, the outside diameter stays constant and the wall thickness increases with larger schedule number. The NPS is very loosely related to the inside diameter in inches, and NPS 12 and smaller pipe has outside diameter greater than the size designator. For example, NPS 6 indicates a pipe whose outside diameter is 168.3 mm. It indicates standard pipe size when followed by the specific size designation number without an inch symbol. Nominal pipe size ( NPS) is a dimensionless designator of pipe size. By adding schedule numbers to the IPS standards, today we know a range of wall thicknesses, namely. The designation known as nominal pipe size replaced iron pipe size, and the term schedule ( SCH) was invented to specify the nominal wall thickness of pipe. In March 1927, the American Standards Association surveyed industry and created a system that designated wall thicknesses based on smaller steps between sizes. So, at the IPS time only three walltickness were in use. Note that on this website only terms XS and XXS are used. Accordingly, pipes were made with double extra strong (XXS) or double extra heavy (XXH) walls, while the standardized outside diameters are unchanged. The higher pressure requirements increased further, with thicker wall pipes. The outside diameter of the pipe was standardized.Īs the industrial requirements handling higher pressure fluids, pipes were manufactured with thicker walls, which has become known as an extra strong (XS) or extra heavy (XH). To begin, each pipe size was produced to have one thickness, which later was termed as standard (STD) or standard weight (STD.WT.). Users started to call the pipe as 2inch, 4inch, 6inch pipe and so on. An IPS 6" pipe is one whose inside diameter is approximately 6 inches. The size represented the approximate inside diameter of the pipe in inches. That IPS system was established to designate the pipe size. The name NPS is based on the earlier "Iron Pipe Size" (IPS) system. Nominal Pipe Size ( NPS) is a North American set of standard sizes for pipes used for high or low pressures and temperatures.