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What's National Pipe Thread Taper (NPT)?

Views:5     Author:Site Editor     Publish Time: 2017-04-11      Origin:Site

National Pipe Thread Taper (NPT) is a U.S. standard for tapered threads used on threaded pipes and fittings. In contrast to straight threads that are found on a bolt, a taper thread will pull tight and therefore make a fluid-tight seal. In America, William Sellers set the standard for nuts, bolts, and screws which became the National Pipe Tapered Thread (NPT) in 1864.

Threaded pipes can provide an effective seal for pipes transporting liquidsgasessteam, and hydraulic fluid. These threads are now used in materials other than steel and brass, including PTFE,[2] PVCnylonbronze, and cast iron.

The taper on NPT threads allows them to form a seal when torqued as the flanks of the threads compress against each other, as opposed to parallel/straight thread fittings or compression fittings in which the threads merely hold the pieces together and do not provide the seal. As the thread body is tapered (0.75 in/ft or 62.5 mm/m) a larger diameter keeps compressing into a smaller diameter and finally forms a seal (no clearance remains between the crests and roots of the threads because of the taper). This means that NPT fittings should be burr-free and lubricated using a lubricating material like lubricating paste or tape. The use of tape also helps to limit corrosion on the threads, which otherwise can make future disassembly nearly impossible.

Commonly used sizes are 1⁄8, 1⁄4, 3⁄8, 1⁄2, 3⁄4, 1, 1 1⁄4, 1 1⁄2, and 2 inch, appearing on pipes and fittings by most U.S. suppliers. Sizes smaller than 1⁄8 inch are occasionally used for compressed air, while sizes larger than 2 inches are uncommon, due to the use of alternative methods of joining that are used with these larger sizes.

Name Introduction Size Downloads Update Category Copy Link Rigid Aluminum Conduit Catalogue Download
haimei catalogue 2020.pdf Haimei catalogue and data sheet, including rigid aluminum conduit, couplings, elbows and nipples. 12.00MB 82 2020-07-21 download Copy Link Download

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