BSPT thread British standard pipe tapered thread

BSPT thread sizes – tapered threads in hydraulics

BSPT thread sizes cover the tapered standard of inch threads used in power hydraulics, pneumatics, and industrial installations where a tight threaded connection sealed on the thread is required. BSPT threads originate from British standards and are commonly found in European and international technical installations. In practice, information regarding BSPT thread dimensions is very often sought because their designation does not directly correspond to the diameter measured with a caliper. Correct identification of the BSPT tapered thread is crucial for selecting the appropriate fittings, adapters, and measuring elements.

What is a BSPT thread

A BSPT thread is a tapered thread whose diameter decreases along the length of the thread. As a result, after tightening, the connection seals on the thread, without the need for a face seal, as is the case with BSPP cylindrical threads. The BSPT thread profile angle is 55 degrees, which distinguishes it from NPT, threads, where this angle is 60 degrees. Due to the tapered design, BSPT threads require the use of appropriate sealing materials, such as PTFE tape or sealing paste. This is a standard practice in hydraulics and pneumatics, allowing for a durable and secure connection tightness.

BSPT thread sizes dimensions

BSPT thread sizes include a range of nominal diameters used in installations for various purposes. BSPT thread dimensions are determined by the number of threads per inch and the tapered profile, so the measurement of the outer diameter alone is not sufficient for their unambiguous recognition. Incorrect identification of a BSPT thread, for example, confusing it with a BSPP thread or NPT, can lead to leaks, seat damage, or installation problems. For this reason, when selecting threaded elements, it is recommended to use dimension tables and verified technical summaries.

Application of BSPT threads in installations

BSPT threads are commonly used in power hydraulics, pneumatics, and industrial installations where a tight and compact threaded connection is required. They are most commonly found in valves, control valves, pumps, control elements, and in measuring equipment connections. In installation practice, BSPT threads are used both in new hydraulic systems and during modernization or repair of existing installations. Thanks to the tapered profile, they work well in places where it is not possible to use additional flat seals.

BSPT vs other thread standards

One of the most common installation problems is confusing BSPT threads with BSPP or NPT threads. Despite similar markings, differences in design, profile angle, and sealing method mean that these threads are not compatible with each other. A BSPT thread seals on the thread and has a 55-degree profile angle, while BSPP is a cylindrical thread requiring a face seal, and NPT has a 60-degree profile angle. Awareness of these differences is crucial for correct installation and system durability.

BSP vs BSPT thread key differences

The BSP thread comes in two varieties: cylindrical BSPP and tapered BSPT, which, despite similar markings, are not identical. The BSPP thread is a cylindrical thread and requires a seal at the face of the connection to achieve tightness, most commonly in the form of a washer or O-ring. On the other hand, the BSPT thread is a tapered thread that seals on the thread during tightening. Differences in construction mean that BSPP and BSPT threads should not be joined directly without using an appropriate adapter, as this can lead to leaks or damage to the thread seat.

How to correctly select a BSPT thread

Selecting the appropriate BSPT thread should take into account its nominal size, the purpose of the installation, and operating conditions such as pressure and working medium. In practice, this means checking the thread dimensions, number of threads per inch, and using the correct sealing material. Correct installation of the BSPT thread, while maintaining the appropriate tightening torque, allows for a durable and safe connection that remains tight even during long-term operation.

BSPT thread dimension table

Related installation elements

Elements with tapered BSPT threads most commonly work with hydraulic fittings and pneumatic, such as valves, fittings, thread adapters, and measuring equipment. In many installations, adapters are also used to connect BSPT threads with other hydraulic thread standards.

FAQ – BSPT thread sizes

What is a BSPT thread?

BSPT thread is a tapered inch thread that seals on the thread. The thread diameter decreases along its length, so after tightening, the connection becomes tight without a face seal.

How to distinguish BSPT from BSPP?

BSPT is a tapered thread and seals on the thread, while BSPP is a cylindrical thread and usually requires a face seal, e.g., using a washer or O-ring.

Does a BSPT thread fit NPT?

No. BSPT and NPT differ in thread profile angle and geometry. An attempt to connect them may result in leakage or damage to the thread seat.

How to seal a BSPT connection?

PTFE tape or sealing paste intended for tapered threads is most commonly used to seal BSPT. Proper tightening of the connection is also important.

Why does the BSPT size not match the diameter measured with a caliper?

The BSPT designation is a nominal size. The actual outer or inner diameter of the thread may differ, so for identification, it is worth using dimension tables and checking the number of threads per inch.

Where are BSPT threads most commonly used?

BSPT threads are found in power hydraulics, pneumatics, and industrial installations, including in valves, control valves, pumps, control elements, and measuring equipment.