The British Standard Pipe (BSP) thread Pneumatic Quick Coupling is a standard thread type used extensively across the globe for plumbing connections (but not in North America). The standard defines the number of threads per inch (pitch) as well as the angle that each thread is engineered to. BSP threads have rounded valleys and troughs with a 55 degree pitch (this is known as Whitworth type).

BSP is BRITISH STANDARD PIPE THREAD– Also known as Whitworth 55° Thread Form

BSPT is BRITISH STANDARD PIPE TAPER THREAD – Thread form per AS 1722.1, BS 21, ISO 7

BSPP is BRITISH STANDARD PIPE PARALLEL THREAD – Thread form per AS 1722.2, ISO 228

BSP sizes are always in imperial measurements and some have commonly metricised names. The table below summarises BSP sizes to help with general identification. Major diameter is slightly less than the actual outside diameter of the threads. Minor diameter is the measurement of the inside of a female threaded connection, from thread to thread.

BSPT Fittings and Adapters Connections

BSPT (British Standard Pipe Taper) is similar to NPT except there are important differences. The angle across the flanks of threads (if you sliced the fitting in half long-ways and measured the angle from root to crest to root) is 55 degrees instead of 60 degrees as it is for NPT. Another important difference is that for many BSPT pipe sizes the thread pitch is different than NPT. Thus an NPT male will sometimes fit into a BSPT fitting or vice versa but they will not seal.

This is a popular fitting in China and Japan but is very rarely used in North America unless the equipment to which it is attached was imported. Thread sealant is needed to seal the male and female fitting together. Longwei has adapters to both male BSPT adapters and female BSPT adapters.

BSPP Parallel Thread Fittings and Adapters Connections

BSPP (British Standard Parallel Pipe) is most popular in the UK, Europe, Asia, Australia, New Zealand and South Africa. It is a parallel thread fitting that uses a bonded seal ring to do the sealing. This bonded ring seal is sandwiched in-between a shoulder on the male fitting and the face of the female fitting and is squeezed in place.

BSPP pressure gauges have a longer male thread and use a copper crush washer that is squeezed in between the bottom of the male fitting and the bottom of the female BSPP hole forming a pressure tight seal. No thread sealant is needed to form a seal. Longwei has male BSPP adapters , female BSPP adapters, female BSPP gauge adapters, and female BSPP Quick-disconnect gauge adapters.

You may be interested in our range of Longwei Air Fittings including adaptors, quick coupler connectors, tire gauges, air blow gun, air chuck and tire repair tools kit, etc. If you have any further questions about the type of thread fitting you require, please contact the Longwei team today!