Choosing the Correct Regulator: Part III – Porting

Porting . . . NPT or BSP?

This blog addresses the third question in ‘How to Determine the Appropriate Regulator‘ as part of our ‘Choosing the Correct Regulator’ series: What type of porting? NPT or BSP?

There are many options for port sizes for a pressure regulator.  Generally, port size will be dictated by the flow requirements in a particular application.  Then there are different types of threads.  The two main thread types are NPT and BSP.  Here are the main differences between NPT and BSP threads:

• NPT (National Pipe Thread) is a tapered thread type, while BSP (British Standard Pipe) is a parallel thread type. This means that NPT threads have a slight taper that allows them to create a tight seal as they are tightened, while BSP threads have a consistent diameter throughout their length.
• NPT threads are more commonly used in the United States, while BSP threads are more commonly used in Europe and Asia.
• NPT threads have a 60-degree included angle, while BSP threads have a 55-degree included angle.
• NPT threads are measured in inches, while BSP threads are measured in millimeters.
• The pitch (distance between threads) of NPT threads is coarser than that of BSP threads. For example, a 1/2-inch NPT thread has 14 threads per inch, while a 1/2-inch BSP thread has 14 threads per 20 millimeters.
• NPT and BSP threads are not interchangeable. An NPT fitting cannot be threaded onto a BSP fitting, and vice versa, without the use of an adapter or conversion fitting.
• Some BSP threads are used in combination with o-ring to complete the seal.

Identifying the size of a thread is sometimes important when trying to find a replacement regulator.   Please note that the OD of the thread on a 1/2” NPT port is not 1/2”.  It is closer to 3/4”.   We have a table of the thread OD for the 4 most popular thread sizes.

Some regulators have different port size options.  The smaller port size options can be the choke point for the airflow.  If the larger port sizes are used, the choke point becomes the internal valving in the regulator.