Processing and use of stainless pipe

On the basis of existing standards, the outer diameter (OD) and wall thickness can be specified from the reference tables based on ASME standards B36.10M and B36.19M. For example, NPS 14 Sch 40 has a diameter of 14 inches and a wall thickness 0,437 inches. However, the ratio of NPP and the OP are not always identical, which can lead to confusion.

For NPS? up to 12 inches, the values of NPP and the OP are different. For example, the outside diameter NPS 12 pipe is actually 12.75 inches. To find the actual diameter for each value of the NPS, it is necessary to consult with the special tables.

For NPS 14 inches or more, the ratio of the values of NPP and OP are identical. That is, the pipe NPS 14 actually has a diameter of 14 inches. The reason for the discrepancies in the NPS? up to 12 inches is that the values of the nuclear power plant was originally installed for the same internal diameters (ID) from the calculation of standard wall thickness at that time. However, with the expansion of the range of values of wall thickness, ID has changed and the standard NPS it was only indirectly correlated to the tables ОD.

Values of NPP and the OP remain fixed wall thickness and increased according to the table. In these tables, the diameter of the NPS increases and the wall thickness remains constant or also increases. Using equations and technological standards ASME B31.3 for piping, we can show that the nominal pressure decreases with increasing diameter of the NPS.

In some specifications for pipes featured the so-called standard wall (STD) or very strong (XS) extra strong (XXS), although in fact these values belong to the old system for iron pipe size (IPS). The sizes of the IPS as well as nuclear power plants. STD is identical to SCH 40S, and 40S is identical to 40 for NPS 1/8 to NPS 10, inclusive. XS identical SCH 80S, 80S and also 80 NPS 1/8 to NPS 8, inclusive. Pipe XXS standard, normally thicker, approximate size, indicated in the table.

The «S» designation, for example «NPS Sch 10S», usually indicates a stainless steel pipe. However, some stainless steel pipe may be referred to differently, so that, strictly speaking, the designation «S» refers only B36.19M tubes, pipes B36.10M. Pipes made of polyvinyl chloride (PVC) pipe and chlorinated polyvinyl chloride (CPVC) is produced in sizes NPS.

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