Are you an engineering expert? Do you like putting things together? Are you preparing for an upcoming project?

If you answered "yes" to any of these questions, you've come to the right place. All of these scenarios mean that you need to hear about British Standard Pipe (BSP).

Even if you don't live in Great Britain, it's like that your country has adopted the BSP thread as its own standard. This means that you need to know about the thread standards and specifications that come with BSP pipe fittings.

To learn about all of this and more, keep reading.

What Is British Standard Pipe?

British Standard Pipe (BSP) is the title of the set of technical standards that identifies specific screw threads. Countries all around the world have adopted these standards and put them to use for interconnecting and sealing pipes and fittings.

British Standard Pipe is the standard in plumbing and pipefitting in most countries. The largest exception to this is North America. There, experts use NPT (National Pipe Thread).

To use BSP screw threads correctly, you have to identify the male and female parts. The male thread has an external shape, while the female thread has an internal shape. Sealing these two pieces together requires twisting the external shape into the internal shape tightly.

Types of BSP Threads

There are two easily distinguishable types of BSP threads:

  1. Parallel (straight)
  2. Taper

You may hear "parallel thread" and "straight thread" used interchangeably. However, they mean the same thing.

Both terms identify screw threads with a constant diameter. You may see this thread type denoted in several ways:

  • British Standard Pipe Parallel thread (BSPP)
  • British Standard Pipe Fitting Thread (BSPFT)
  • British Standard Pipe Mechanical Thread (BSPM)

Some of these pipes also have the letter G on them to set them apart from other threads.

Here are a couple more things to consider about parallel threads:

  • They conform to ISO 228-1
  • Their port conforms to ISO 1179
  • Their pitch and diameter are measured in inches
  • They require an o-ring, crush washer, gasket, or metal-to-metal seal between connections to create a pressure-tight seal
  • Their thread angle is 55°

The second kind of BSP thread is the taper thread. The British Standard Pipe Taper thread (BSPT) has a changing diameter. It may increase or decrease along the length of the thread.

Some taper threads have the letter R on them as an identifier.

It's common to incorrectly identify tapered pipes as NPT pipes. However, NPT pipes have a 60° flank angle, while tapered BSP pipes have a 55° angle.

Here are a couple more things to consider about tapered threads:

  • They conform to ISO 7
  • Their pitch and diameter are measured in inches
  • They can seal via metal-to-metal connection, although a sealing compound can ensure a pressure-tight seal
  • Their taper angle is 1° 47'
  • Their thread angle is 55°

Both the parallel and tapered threads for British Standard Pipe standards are different from all National Pipe Thread standards. Be careful to distinguish all of these kinds of threads from one another to ensure that you're using the right kind.

Types of BSP Joints

There are also two kinds of joints:

  1. Jointing threads
  2. Longscrew threads

Jointing threads are the kinds of pipe threads that require the mating of two parts in order to create a proper seal. One of these parts is the taper male thread, and the other part is either a parallel or taper female thread.

Although, taper female threads are not commonly used in Europe.

Longscrew threads identify the use of parallel pipe threads and a soft material, such as an o-ring seal or a washer. The pressure comes from the joining of the pipe thread and the material.

The material lies between the end face of the male thread and a socket or nipple face. To tighten the seal, you must tighten the backnut.

BSP Thread Form

The thread form of these kinds of screw threads follows the British Standard Whitworth thread standards.

First, the creator must form a symmetrical V-thread by creating an angle of 55° between the two planes. To ensure accuracy, the measurer must confirm by measuring the angle via the axial plane.

Next, they must confirm that one-sixth of the V-shape is truncated at the top and the bottom of the screw.

The threads must also round evenly at the tops and bottoms. More specifically, they must have circular arcs that end tangentially with the flanks. In this case, r must be equal to 0.1373P.

Lastly, they must ensure that the theoretical depth of the thread is 0.6403 times the nominal pitch which is h=0.6403P.

These standards ensure that the forms of every thread stay consistent. This ensures that all joining threads will be able to fit one another. Thus, there shouldn't be any difficulty in using BSP threads for projects.

BSP Pipe Thread Sizes

There are at least 41 thread sizes. They range from 1/16 to 18:

  • 1/16
  • 1/8
  • 1/4
  • 3/8
  • 1/2
  • 5/8
  • 3/4
  • 7/8
  • 1
  • 1-1/8
  • 1-1/4
  • 1-3/8
  • 1/1/2
  • 1-5/8
  • 1-3/4
  • 1-7/8
  • 2
  • 2-1/4
  • 2-1/2
  • 2-3/4
  • 3
  • 3-1/4
  • 3-1/2
  • 3-3/4
  • 4
  • 4-1/2
  • 5
  • 5-1/2
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18

It's notable that only 15 of these thread sizes are in ISO 7, and only 24 of these thread sizes are in ISO 228.

Originally, each one of these numbers came from the inner diameter of the steel tube that each thread should fit. This was in inches.

However, the implementation of contemporary pipes changed this method. Modern pipes have thinner walls in order to save material. This construction causes the pipes to have a larger inner diameter than previously.

Therefore, today's modern standard metric version is just a size number. With these numbers, the indicated size is the measurement of the major outer diameter of the external thread.

For a taper thread, this is a little bit different. The diameter at the gauge length goes from the small end of the thread. Gauge length is plus one or minus one from the thread pitch.

If a taper measurement is 1:16, this means that the diameter increases by one unit of measurement for every 16 units of measurement from the end.

Naming a BSP Thread

There are several components of a BSP thread name.

  1. "Pipe thread"
  2. The document number of the standard
  3. The common symbol for the kind of pipe thread
  4. The thread size

Common symbols for pipe threads (step three) are as follows:

  • G, external and internal parallel (ISO 228)
  • R, external taper (ISO 7)
  • Rp, internal parallel (ISO 7/1)
  • Rc, internal taper (ISO 7)
  • Rs, external parallel

For example, a pipe thread may have the following name: Pipe thread EN 10226 Rp 2-1/2.

In most cases, threads are right-handed. However, when a thread is left-handed, we add "LH" to the end of the thread name.

So, the previous example would become the following if it were left-handed: Pipe thread EN 10226 Rp 2-1/2 LH.

BSP Threads vs NPT Threads

Both BSP (British Standard Pipe) and NPT (National Pipe Thread) standards have similar applications. Depending on where you live, these threads can be very different.

Both NPT and BSP threads are pipe thread standards for screw threads that experts use for pipes, pipe fittings, and pressure seals.

However, it's important to jump into the differences so that you can distinguish these threads in practice.

The Location

BSP threads are by far the most popular. Most countries worldwide have adopted these standards:

  • The UK
  • All of Europe
  • Australia
  • New Zealand
  • South Africa

On the other hand, NPT standards are in use in the United States and Canada.

The History

NPT standard for National Pipe Thread. Some refer to this as National Pipe Thread Tapered since the standards specifically state the characteristics fro a tapered thread.

Experts use these standards to craft threads that can join and fit into one another to create tight seals.

These standards came about from the American National Standard Pipe Thread, which is also known as the national pipe thread standards.

NPT states technical standards and exacts required measurements for both tapered and straight thread series. However, tapered is the most common form.

BPS standards come from ISO 228 standards and Whitworth standard threads. Worldwide, this standard is being used for plumbing and pipefitting.

In fact, BPS standards are adopted internationally for interconnecting pipes and fittings. They're also used for projects that need pressure-tight seals.

The Specifications

Both BSP and NPT threads have the same pitch. They also have somewhat similar peaks and valleys.

However, there are two characteristics that distinguish these threads from one another.

First, NPT threads have flat peaks and valleys. BSP standards call for rounded peaks and valleys.

Second, NPT threads have a thread angle of 60°. BSP standards call for a thread angle of 55°.

Get the BSP Threads That You Need

After getting through all of that information, you are an expert in BSP threads. Understanding and getting to know the British Standard Pipe specifications is important, especially if you live in an area of the world where it's the standard.

Even more important than understand the standards themselves, you need to make sure that you're getting the quality equipment that you need to get your projects done.

That's where we come in.

At Wiseman Thread Tools, we can help you find the BSP threads that you need to get your work done. You'll find quality in every single one of our threads and tools.