Types of threads: BSP, BSPT, NPT

What are the types of threads? Where are BSP, BSPT, and NPT threads used? How can threads be connected? You will find all of this information in this blog.

The thread commonly used in hydraulics in Europe, and widely in other parts of the world, originates from the British BSP standard. This standard refers to a pipe thread based on the Whitworth profile, with measurements expressed in inches, and includes both parallel BSPP threads and tapered BSPT threads. The term BSP is the traditional name, but the forms of pipe threads have now been standardized as follows:

• The ISO 228-1 standard defines a thread connection without sealing at the metal-to-metal contact point of the threads, and applies to both external and internal parallel threads marked as G. This type also refers to the ISO 228-1 description BSPP or simply BSPP; that is, BSPP = G,

• The EN 10226-1 standard defines a thread connection with sealing achieved on the thread itself, which is equivalent to the ISO 7-1 standard and incorporated into the DIN 2999 standard. This standard is also used to define the tapered BSPT thread. The EN 10226-1 standard, or as we call it, the "BSPT tapered thread system," includes three types of threads:
• External tapered thread R, also referred to as EN 10226-1 R, EN 10226-1 BSPT R, or BSPT R.
• Internal tapered thread Rc, also referred to as EN 10226-1 Rc, EN 10226-1 BSPT Rc, or simply BSPT Rc.
• Internal parallel thread Rp, with descriptions such as EN 10226-1 Rp, EN 10226-1 BSPT Rp, or simply BSPT Rp.

 

Here are some examples of products with BSP threads:

 

 

 

 

 

 

Stainless steel nipple BSP                     Plug with 60-degree sealing                          BSP threaded coupling

 

BSP, G, and Rp threads, as well as BSPP, are essentially the same. The three fittings in the images above feature the same type of thread.

In the USA and Canada, the NPT thread is dominant: both external and internal tapered threads. Due to advanced global industrialization, the NPT thread is also common in Europe, and in Poland, particularly in the petrochemical industry and pneumatics. The NPT thread has a different profile than the Whitworth thread, and it is not compatible with BSP or BSPT.

Examples of products with NPT threads:

 

 

 

 

 

 

 

 

Stainless steel NPT nipple                                 Steel NPT plug                                     NPT reducing nipple

 

Which Threads Can Work Together?

Of course, threads within the same system that match nominal diameters can work together:

• External G (BSPP) parallel thread ↔ Internal G (BSPP) parallel thread
• External R (BSPT R) tapered thread ↔ Internal Rc (BSPT Rc) tapered thread
• External R (BSPT R) tapered thread ↔ Internal Rp (BSPT Rp) parallel thread
• External NPT thread ↔ Internal NPT thread (both tapered),

Additionally:

• External R (BSPT R) tapered thread ↔ Internal G (BSPP) parallel thread: This connection can work, and sealing on the thread is possible. However, due to the increased spaces between the threads, it requires more care than an R-Rp connection.

On the other hand, the connection "External G (BSPP) parallel thread -- Internal Rp (BSPT Rp) parallel thread," despite having the same diameter, thread profile, and pitch, may cause issues in fitting, and the connection will not work.

Also, you should avoid connecting NPT threads with BSPT threads (or with G threads).

Fittings, reducers, couplings, nipples, and unions with the above types of threads are available at our PolBeris store, here>>