NPT / National Pipe Thread Taper | NPTF / National Pipe Taper Fuel
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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. NPT is defined by ANSI/ASME standard B1.20.1. A semi-compatible variant called National Pipe Taper Fuel (NPTF), also called Dryseal American National Standard Taper Pipe Thread, defined by ASME B1.20.3, is designed to provide a more leak-free seal. NPTF threads are the same basic shape as NPT but with crest and root heights adjusted for an interference fit, eliminating the spiral leakage path.
This thread type is the most commonly used tapered pipe thread connection found on equipment made in North America. Additional sealing aids such as Teflon® tape are used with these threads. This connection is often used on fluid power systems, although it is not recommended by the National Fluid Power Association for use in hydraulic applications.
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