Iron pipe size

Iron Pipe Size (IPS) is an old system still used by some industries, including major PVC pipe manufacturers, and legacy drawings and equipment.

The iron pipe size standard was initiated in [1801 - 1810] and remained in effect until after World War II. The IPS system was primarily used in the US and the United Kingdom. In the 1920s, the Copper Tube Size (CTS) standard was combined with the IPS standard.

During the IPS period, pipes were cast in two halves and welded together, and pipes' dimensions were sized by reference to the outside diameters ("ODs") of the pipes [ http://www.thomas-insulation.com/publications/products/ips-cts-sizinggraphic.pdf ] . The ODs under IPS were roughly as we know them today under the Ductile Iron Pipe Standard (DIPS) and Nominal Pipe Size (NPS) Standards, and some of the wall thicknesses were also retained with a different designator. In 1948, the DIPS came into effect, when greater control of a pipe's wall thickness was possible.

CTS diameter always specifies the OD of a tube, where pipe diameter specifications only approximate the pipe ID for sizes of 12 inch or less, and STD wall thickness.The IPS number (reference to an OD) is the same as the NPS number, but the schedules were limited to Standard Wall (STD), Extra Strong, (XS) and Double Extra Strong (XXS). STD is identical to SCH 40 for NPS 1/8 to NPS 10, inclusive, and indicates .375" wall thickness for NPS 12 and larger. XS is identical to SCH 80 for NPS 1/8 to NPS 8, inclusive, and indicates .500" wall thickness for NPS 8 and larger. Different definitions exist for XXS, but it is generally thicker than schedule 160. [ http://www.mcelroy.com/fusion/chartsreference.htm ]

References

ee also

*Pipe (material)#Sizes