2" BSP thread – description and application

2" BSP thread is a popular pipe thread standard compliant with the Whitworth profile, commonly used in power hydraulics, pneumatics, water systems, and general industry. It is available in two variants: straight (BSPP – designated G 2) and tapered (BSPT – designated R 2), allowing for the choice of sealing method for specific applications.

What is a 2" BSP thread?

It is a pipe thread with a nominal size of 2 inches and a 55° profile. In practice, a 2" BSP thread has 11 threads per inch (11 TPI), and its outer diameter is approximately 59.2–59.6 mm, which facilitates initial size identification when selecting fittings and ends.

Characteristic features of the 2" BSP thread

The 2" BSPP (G) thread is straight, so the thread–thread connection itself does not ensure tightness – this is achieved through face sealing, e.g., on a bonded seal, a flat gasket, or on a 60° cone in the port. In contrast, the 2" BSPT (R) thread is tapered and can seal on the thread itself (using appropriate sealing compounds). Both variants are based on the same number of threads per inch (11 TPI) and a similar outer diameter of ~59.6 mm, which should be considered when identifying installation components.

Application of the 2" BSP thread

In power and general industrial hydraulics, you will find 2" BSP threads in connections of large cross-sections: pump and tank connections, supply manifolds, high-flow return lines, line filters, control valves, large-scale quick couplings, and sections of water and air installations. The 2" size is chosen where low pressure losses, stable flow, and easy maintenance are important.

Seal selection and compatibility (G 2 vs R 2)

For ports with G 2 (BSPP) internal threads, use ends with face seals (e.g., flat port + washer). For R 2 (BSPT) ports, select tapered elements that seal on the thread. In practice, R 2 (ext.) is often combined with Rp 2 (int., straight) – this is a popular and correct arrangement for tapered–straight connections. Always verify the port type before assembly.

Internal threads – what components will you find in the 2" BSP size?

In the 2" BSP variant, available components include: couplings (sleeves), AA connectors (nut–nut), AA female tees, reduction bushings, elbow couplings, as well as nuts and locknuts. These elements enable the construction and expansion of installations and transitions between different standards.

Smaller and larger thread – how to choose the size?

If 2" is too large, the "smaller thread" in the same series is, for example, 1 ½" BSP (outer diameter ~47.3–47.9 mm, 11 TPI) – a common choice for smaller flows. On the other hand, the "larger thread" is, for example, 2 ½" BSP, used in lines with very large cross-sections and flows. Data on outer diameters helps initially confirm the size during on-site identification.

Assembly tips

For BSPP, ensure the cleanliness and quality of the face surfaces and the selection of the correct washer; tighten while controlling the torque to avoid damaging the seal. For BSPT, use an appropriate thread sealant (e.g., PTFE tape or anaerobic thread sealants) and remember that the position of the component after tightening depends on the taper fit – avoid "backing off" the connection.

Technical parameters (2" BSP)

• Nominal size: 2"

• Number of threads per inch (TPI): 11

• Profile: Whitworth 55°

• Outer diameter of external thread: approx. 59.2–59.6 mm

• Variants: BSPP (G 2 – straight, face seal), BSPT (R 2 – tapered, thread seal)