What is NPT thread?

NPT (National Pipe Taper) thread is a tapered pipe thread originating from American standards, widely used in power hydraulics, pneumatics, and industrial installations. A characteristic feature of the NPT thread is the taper, which is 1:16. This means that the thread diameter decreases along its length, and the seal is created by the wedging of the thread turns during screwing. In practice, the NPT thread seals on the threads themselves, without the use of face seals. To achieve full tightness, PTFE tape, sealing pastes, or anaerobic adhesives are most commonly used. Such a solution provides a durable and pressure-resistant connection, even in demanding operating conditions.

NPT thread dimensions:

NPT threads are available in a wide range of sizes, which are specified in inches.

• 1/8" NPT,
• 1/4" NPT,
• 3/8" NPT,
• 1/2" NPT,
• and 1" NPT.

As the thread size increases, its diameter and the number of threads per inch increase, adapted to the given nominal dimension.

Each NPT thread size has a specific number of threads per inch (TPI – threads per inch), which is important for the correct selection of fittings and adapters. It should be remembered that NPT thread is not compatible with metric nor with BSPthreads, despite apparent similarity in some sizes. In the Hydron store offer, power hydraulic elements equipped with NPT threads are available, such as fittings, adapters, pressure gauge connections and other installation components. The assortment includes various NPT thread sizes, which allows for easy fitting of elements to existing hydraulic and pneumatic systems. Thanks to Hydron's experience in power hydraulics, customers can count on professional technical support in selecting suitable solutions and safe components adapted to work under pressure.

NPT thread types:

• NPT thread is a tapered thread that seals on the threads. PTFE tape, pastes, or thread adhesives are used for assembly. It is the most common variety in hydraulics and pneumatics.
• NPTF thread is the so-called dry thread, designed for self-sealing without additional sealing materials. It is mainly used in fuel installations and systems requiring very high tightness.
• NPSM thread is a cylindrical variety of pipe thread. It does not seal on the threads and requires a face seal, e.g., a washer. Structurally, it resembles BSPP, but it is not compatible with it.

NPT vs BSP – differences between threads in power hydraulics

Comparison of NPT vs BSP is one of the most frequently appearing issues when selecting fittings and connections in power hydraulics, as both types of threads are visually similar but are not compatible with each other. NPT thread is a taperedthread, in which sealing occurs on the thread turns through their wedging, while BSP thread occurs in both cylindrical (BSPP) and tapered (BSPT) versions, where sealing is most often achieved using a gasket, ring, or face surface. In practice, this means that despite the similar thread angle and similar diameters, connecting NPT with BSP can lead to leakage or thread damage. Therefore, when analyzing npt vs bsp, not only the thread size is of key importance, but also its geometry, sealing method, and manufacturing standard. In hydraulic installations, elements of the same thread type should always be used, in accordance with the system's technical documentation.