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This page provided the thread dimensions of 3/8 - 18 NPTF. NPTF stands for National Pipe Thread Fuel, based on ASTM B1.20.3. It is also called Dryseal Pipe Thread. It is a variation of the more popular NPT thread standard based on ASTM B1.20.1.
NPTF stands for National Pipe Tapered Fuel. . The basic profile is identical to the common NPT thread. The main difference is that NPTF provides a leakproof seal without using a sealant. It is obtained by tight tolerances and gauging requirements that create interference fitting in all conditions.
For straight fittings, tighten to recommended torque listed in the following table. For shape fittings, approximately 1/2 turns should be made and then torque to the desired orientation without exceeding maximum recommended torque. Assembly Torque, Adapter Unions and Pipe Fittings.
Follow the NPT/NPTF guidelines for their application. In general, tapered thread connections have the following limitations which should be considered when specifying port
National Pipe Tapered Fuel (NPTF) The male and female threads connect and a seal is formed when the two are mated together (i.e. threads deformation). This is known as a dry seal thread. If additional sealing is required, teflon and pipe dope can be applied.
NPTF Classes of Product Threads. Class 1 Threads - “Acceptability is determined by coordinated use of L1 & L2 gages for external product threads and L1 & L3 internal product threads. Crest and root truncation is generally considered to be controlled by tooling or other means”.
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.
