What are NPT, BSPP, BSPT, and G threads?
NPT, BSPP, BSPT, and G threads are among the most common thread types in fluid connection systems, belonging to the two major standard systems of the United States and the United Kingdom (Europe).
Image Description
Core Difference
|
Characteristics |
NPT |
BSPT (R) |
BSPP (G) |
G Thread |
|
Standard System |
American Standard |
British Standard/European Standard/National Standard |
British Standard/European Standard/ISO |
ISO |
|
Tooth angle |
60° |
55° |
55° |
55° |
|
Thread profile |
conical |
conical |
Straight |
Straight |
|
Sealing Principle |
Thread + Sealant |
Thread + Sealant |
Flat washer |
Thread not sealed |
|
Common Applications |
North American General Piping |
Universal Piping |
Hydraulic System |
Electrical conduit |
Summary: How to distinguish?
a.By Country or Region:
| North America | Primarily uses NPT. |
| Europe, China, and Other Asian Regions | Primarily uses BSPP (G) and BSPT (R). |
b.By Application Field:
| Hydraulic Systems | Prefer BSPP (G) fittings due to their reliable end-face sealing and reusability. |
| General Pressure Piping (e.g., water pipes, gas lines) | Select NPT or BSPT based on regional standards. |
c.Field Identification (Most Reliable Method):
| Measure with thread gauges | This is the most accurate method. Test with both 55° and 60° gauges; the one that fits perfectly indicates the correct thread angle. |
| Visual inspection | Check for noticeable taper on the threads. Tapered threads indicate NPT or BSPT; cylindrical threads without taper indicate BSPP (G). |
d.Most important point:
NPT and BSPT are absolutely not interchangeable due to differing thread profiles and pitches. When uncertain, always use thread gauges for measurement confirmation.
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