ANSI/ASME B1.20.1 thread with API 5B

[A_Alrumaidh]

Hi,
I reviewed a material certificate for a pipe nipple with threading to ANSI/ASME B1.20.1 NPT. However, our requirement was threading to API 5B Table 3.

Can I accept this deviation?

I checked the dimensional requirements of both specifications and found a minor difference in the height of the thread. Otherwise, as far I could notice, they are the same. Is there a major difference that I didn't notice?

 

[jmec87]

There is not a major difference and they are often used interchangeably, especially for smaller sizes. Note that API 5B has line pipe threads and does not refer to them as NPT (although they are nearly identical to NPT), so an NPT thread per API 5B is not technically possible.

The below notes are from API 6A 21st Edition Section 14.3.2.1:
NOTE 1 Pipe threads, general-purpose (inch), may be used for line pipe thread sizes 38mm (1 1/2in.) and smaller.
NOTE 2 Although line pipe threads in accordance with API 5B and NPT threads are basically interchangeable, the slight variation in thread form can increase wear and tendency for galling after several make-ups.