National Pipe Thread (NPT) is a widely used standard for tapered pipe threads in the United States. These threads are commonly found in pipes, fittings, and valves used for the transportation of fluids and gases. The specifications for NPT are spelled out in ANSI B1.20.1.
NPT pipe threads are characterized by several key features:
- Tapered Threads: One of the defining features of NPT threads is their taper. Unlike parallel threads, which have a consistent diameter along the thread length, NPT threads gradually narrow as they approach the end of the pipe or fitting. This taper is typically 1/16 inch per inch, meaning that for every inch of thread length, the diameter decreases by 1/16 of an inch.
- Thread Angle: NPT threads have a thread angle of 60 degrees. This means that each thread makes a 60-degree angle with the centerline of the pipe or fitting.
- Flank and Crest: The “flank” refers to the sloping sides of the threads, while the “crest” is the topmost point of each thread. The shape of NPT threads is designed to create a wedging action as they are tightened, creating a seal.
- Tapered Seal: The sealing in NPT threads occurs at the point where the threads make contact with each other. This is known as the “interference fit,” and it is what creates the seal. Because of this design, it’s important not to overtighten NPT connections, as it can damage the threads and compromise the seal.
There are several variations of NPT threads, each with its specific designation:
- NPT: National Pipe Taper – This is the standard tapered thread used in the United States for general-purpose pipe connections. This is the pretty much only style you will see in the beverage industry.
- NPTF: National Pipe Taper Fuel – NPTF threads have a modified crest and flank design that provides a more robust sealing surface, making them suitable for applications involving hydraulic and pneumatic systems.
- NPS: National Pipe Straight – Unlike NPT, NPS threads are straight and do not have a taper. They are typically used for mechanical connections where a seal is not required.
QC Hydraulics supply many kinds of NPT fittings in widely used in various industries, including plumbing, construction, Industrial Machinery, Hydraulics and Pneumatics, automotive… Please contact us to choose the right fittings for your applications.
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