What is a tapered thread pipe fitting?

Thread Pipe Fitting

What is a tapered thread pipe fitting?

Threaded fittings are commonly used to make connections between pipes and certain treatments. The most common design of threaded pipe fittings is the tapered pipe thread design. The purpose of the tapered thread is to allow the pipe and fitting to "wedge" together when engaged, creating a mechanically tight and leak-free joint. When male and female tapered pipe threads are first engaged, they form a loose junction. There are several different standards available for tapered-thread fittings. For each standard, the angle of the thread is determined in the same way as the angle of the taper. The number of threads per unit length of thread varies with the diameter of the pipe fitting.

Some type of sealant is applied to the NPT pipe threads to ensure a pressure tight seal. Teflon tape as well as various liquid pipe dope compounds work well for these purposes. Sealants with NPT threads are needed for two reasons. Lubricate the male and female parts and protect the metal surface from leakage, as well as fill or reverse the spiral gap between the root of the female thread and the tip of the male thread.

NPTF pipe threads, also known as National Pipe Threads, are engineered with the same thread angle and pitch as NPT threads, but are carefully machined to avoid the spiral leakage paths inherent in NPT threads. This design - at least in theory - avoids the need to use sealant with NPTF threads to achieve a pressure-tight seal between the male and female pieces, which is why NPTF threads are commonly referred to as dry seals.

ANPT, also known as Aeronautical National Pipe Tapered, is similar to NPT, except for greater precision and quality for its intended use in aerospace and military applications.

Pipe Threads

There are various national as well as international standards for pipe threads. They vary according to purpose. Two basic categories of pipe threads are parallel or straight pipe threads, tapered pipe threads

Tapered Pipe Threads

Piping and fittings are mainly used to carry liquids and gases. Because of this, they must have a threaded connection. Tapered threads help make a good seal. The male and female threads contract and join together. Hence, thread connections are strong and leak resistant. The two most common standards for tapered pipe threads are the NPT American National Standard Taper Pipe Thread and the BSPT British Standard Pipe Taper Thread. NPT pipe thread is the most commonly used pipe thread and is incompatible with BSPT pipe threads. NPT threads have a 60-degree angle and BSPT threads have a 55-degree angle. Also, NPT threads have flat peaks and valleys and BSPT threads have rounded peaks and valleys and thread pitch (TPI, threads per inch). Each NPT as well as BSPT pipe has a thread size variation and that is a specific number of threads per inch