Different thread sealing depends on the geographical region, size of the pressure system, and the environment. For example, In Aisa, such as China, Korea, Japan, etc normally use BSPT; In the U.S, Canada, etc always use NPT, Then the BSP thread is most popular in the UK, Europe, Australia, New Zealand, and South Africa. While one sealing style is not inherently better than another each style has its application.
There are two types of BSP threads: (Normally female thread uses the BSPP parallel thread, the male thread uses the BSPT tapped thread).
BSPT: British Standard Pipe Taper 55 degree – also know as “R” or “Rc” threads.
It is a popular thread in China, Korea, Japan, Malaysia, and other Asia market, but it is very rarely used in North America.
BSPP: British Standard Pipe Parallel – also know as ” G” or “Rp” threads
This thread is common in the UK, Europe, Australia, New Zealand, and South Africa.
NPT & NPS (American National Pipe)
NPT & NPS are the most popular thread type in the United States and Canada.
American National pipe has two basic types of threads:
NPT: National pipe Taper- 60 Degrees
NPS: National Pipe Straight
Both NPT and NPS have the same thread angle, shape, and pitch (threads per inch).
NPT threads are tapered and NPS threads are straight (parallel). Both threads have a 60 degree included angle and have flat peaks and valleys.