4 Types of Thread Process Connections Your Need Know

Back in the 19th century, screw Threads Process Connections come in a great variety and are incompatible. Nowadays, thanks to the efforts made by people committing to standardizing process connections threads, choices are nailed down to a few when choosing a pressure transmitter. In what follows, three types of thread are introduced: BSP, NPT, and UNF.

British Standard Pipe

BSP, British Standard Pipe, was created by Joseph Whitworth in the middle of 19^th century and is now widely accepted from Europe to Asia, in particular in the UK. BSP is a type of parallel thread and the pressure tight seal is enabled with a sealing washer, which is made of different materials depending on the pressure and the medium being used. The most common sizes are ¼ or ½ inch BSP.

1/2"BSP MALE	1/2"G EN837 DIN16288

1/4"G EN837 DIN16288	1/4"G DIN3852

National Pipe Taper

In the USA, NPT (National Pipe Tapered) is the most popular process connection, especially in businesses of oil and petroleum. Compared with BSP, NPT is easier to cut and user-friendly, and is considered a booster to American Industrial Revolution. Being a kind of screw thread system, NPT is tapered thread with the pressure tight seal being made on the thread itself. The most common sizes are 1/4, or 1/2 inch NPT.

1/2"NPT MALE	1/4"NPT MALE

1/4"NPT FEMALE	1"NPT SEALED

Unified Thread Standard

William Sellers also developed what became the Unified Thread Standard. Straight thread Process Connections known as SAE are now called UNF (Unified National Fine) under the Unified Thread Standard.

A common variation of this Process Connections is the M/F-250, or the autoclave fitting. This fitting has a cone at the end of it for pressure ranges above 10,000 psi. It is also commonly referred to as a Sno Trik® fitting as well – though that is a brand name.

The most common types of UN (Unified National) thread are:

1. UNC – Unified National Coarse Thread, comparable with the ISO metric thread.
2. UNF – Unified National Fine Thread.

*Compared to standard threads (coarse thread), a fine thread has a smaller pitch.

Unified threads come in three different classes:

1. 1A (external) & 1B (internal): for applications where a liberal tolerance is required to permit easy assembly even with slightly nicked threads.
2. 2A (external) & 2B (internal): most commonly used class for general applications
3. 3A (external) & 3B (internal): for applications where closeness of fit and/or accuracy of thread elements are important.

ISO Metric Screw Thread

The ISO metric screw threads are the world-wide most commonly used type of general-purpose screw thread. They were one of the first international standards agreed when the International Organization for Standardization was set up in 1947.

The “M” designation for metric screws indicates the nominal outer diameter of the screw, in millimeters (e.g., an M6 screw has a nominal outer diameter of 6 millimeters). (Source from Wikipedia)

Comparison for Thread Process Connections:

How to Choose Thread Process Connections

There are no criteria to judge which Thread Process Connections mentioned above is better. Actually, each of them appears at a proper time with a proper reason. When it comes to choose a process connection, what really matters is the pipe fitting your pressure transducer is to be used.  It is true that different country has its own standards and it is also a fact that any thread standard is available worldwide.

If you need help in finding what your need. Contact Us! We are always ready to give your support in choosing pressure sensor Thread Process Connections.