British Standard Pipe Fit

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British Standard Pipe (BSP) is a family of technical standards for screw threads that has been adopted internationally for interconnecting and sealing pipes and fittings by mating an external (male) thread with an internal (female) thread. It has been adopted as standard in plumbing and pipe fitting, except in the United States, where NPT and related threads are the standard used.

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Types

Two types of threads are distinguished:

• Parallel (straight) threads, British Standard Pipe Parallel thread (BSPP; originally also known as British Standard Pipe Fitting thread/BSPF and British Standard Pipe Mechanical thread/BSPM), which have a constant diameter; denoted by the letter G.
• Taper threads, British Standard Pipe Taper thread (BSPT), whose diameter increases or decreases along the length of the thread; denoted by the letter R.

These can be combined into two types of joints:

Bsp Fitting Video

Thread form

The thread form follows the British Standard Whitworth standard:

• Symmetrical V-thread in which the angle between the flanks is 55° (measured in an axial plane)
• One-sixth of this sharp V is truncated at the top and the bottom
• The threads are rounded equally at crests and roots by circular arcs ending tangentially with the flanks where r=0.1373P
• The theoretical depth of the thread is therefore 0.6403 times the nominal pitch

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Pipe thread sizes

At least 41 thread sizes have been defined, ranging from ¹/₁₆ to 18, although of these only 15 are included in ISO 7 and 24 in ISO 228. The size number was originally based on the inner diameter (measured in inches) of a steel tube for which the thread was intended, but contemporary pipes tend to use thinner walls to save material, and thus have an inner diameter larger than this nominal size. In the modern standard metric version, it is simply a size number, where listed diameter size is the major outer diameter of the external thread. For a taper thread, it is the diameter at the "gauge length" (plus/minus one thread pitch) from the small end of the thread. The taper is 1 to 16, meaning that for each 16 units of measurement increase in the distance from the end, the diameter increases by 1 unit of measurement.

These standard pipe threads are formally referred to by the following sequence of blocks:

• the words, Pipe thread,
• the document number of the standard (e.g., ISO 7 or EN 10226)
• the symbol for the pipe thread type:
  • 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
• the thread size

Threads are normally right-hand. For left-hand threads, the letters, LH, are appended.

Example: Pipe thread EN 10226 Rp 2½

The terminology for the use of G and R originated from Germany (G for gas, as it was originally designed for use on gas pipes; R for rohr, meaning pipe.)

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Pipe and fastener dimensions

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ISO 7 (Pressure Tight threads)

The standard ISO 7 - Pipe threads where pressure-tight joints are made on the threads consists of the following parts:

• ISO 7-1:1994 Dimensions, tolerances and designation
• ISO 7-2:2000 Verification by means of limit gauges

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ISO 228 (Non Pressure Tight Threads)

The standard ISO 228 - Pipe threads where pressure-tight joints are not made on the threads consists of the following parts:

• ISO 228-1:2000 Dimensions, tolerances and designation
• ISO 228-2:1987 Verification by means of limit gauges

Source of the article : Wikipedia