Pressure transmitter thread types such as NPT, BSP, G thread, and metric thread must be identified correctly before installation or replacement. Similar-looking threads are not always interchangeable. Choosing the wrong thread can cause leakage, poor sealing, damaged connections, or complete installation failure.
This problem is especially common in replacement orders. Buyers may only provide photos or say “1/2 inch thread,” but different thread standards can look close while sealing in different ways.
NPT Thread
NPT is a tapered thread commonly used in many industrial and process applications. It seals by thread interference, usually with sealing tape or suitable sealant. Because it is tapered, it should not be treated the same as a parallel thread.
A common example is 1/2 NPT. It may look similar to G1/2 at first glance, but it is not the same.
BSP and G Thread
BSP is a broader thread family. In pressure transmitter applications, buyers often see G thread, which is a parallel pipe thread. G thread usually seals by a gasket, O-ring, or sealing face, not by thread taper.
This means a G thread connection needs the correct sealing method. If a buyer uses it like a tapered thread, leakage may occur.
Metric Thread
Metric thread is also used in some pressure transmitters and equipment connections. M20 × 1.5 is a common example. It is especially common in some instruments, machinery, or regional standards.
Metric thread should be confirmed by diameter and pitch. A wrong pitch can damage the thread during installation.
What Buyers Should Confirm
Before ordering, buyers should confirm both the transmitter side and the process side. A thread description should include:
- Thread standard
- Thread size
- Male or female connection
- Parallel or tapered type
- Sealing method
- Material and pressure requirement
If the old thread is uncertain, a clear photo and measurement can help, but final confirmation may still need site checking.
Replacement Warning
For replacement projects, do not assume the new transmitter can use the same adapter unless the thread type is confirmed. Wrong thread matching may appear to fit for a few turns, but it may not seal correctly and can become unsafe under pressure.
Conclusion
NPT, BSP, G thread, and metric thread are common pressure transmitter thread types, but they seal differently and should not be mixed by appearance. Correct thread identification helps avoid leakage and installation failure.
SIY Electric can help match thread types, adapters, and process connections for pressure transmitter replacement and installation.
