Until your 13mm wrench rounds the corners of the really tight hex nut because close enough wasn’t.
failed at the certification stage, unfortunately.
Out of curiosity, what fitting did you utilize, and what aspect about it failed?
I assume you determined the necessary thread type beforehand: BSP vs NPT?
A direct fitting as could be found upthread - essentially a threaded coupler, 20mm M to 15mm F. No common or standardized name identified.
I assuredly know the difference between BSP and NPT. NPT is my only interest - I referred to BSP in the OP because i wanted to broaden the question to the entire range of common thread types. In case it was a common thing in BSP but not in NPT, etc etc.
The standard I am working within only allows an *upright *sprinkler to have a 15mm size connection. A pendant sprinkler - which is my interest in this application - of the size I need to use (K11.2/ K160) requires a 20mm thread minimum. I cannot determine why this is, but must accept it as a basic fact unfortunately.
Your initial post stated: “Thread types are all BSP or NPT, can’t recall at the moment.” So it is not unreasonable to question your knowledge of such.:mad: They are obvious in their difference.
It is difficult to imagine, irrespective of thread type, that any fire pipe retrofit cannot be amended by the proper application of a pipe threader and a few common "T"s, "El"s, and adapters. What’s the big deal?
Not just colloquially. It’s the ASME B36.10 standard ‘Diametre Nominal’. It is, I think, the metric standard (metric pipe standardization was very strange).
The 1/2" is the nominal /inside/ diameter, and 1/2" pipe is of course, “Pipe that has the same outside dimension as nominal 1/2” pipe had when they standardized pipe sizes".
Since pipe wall thickness is thinner now than it was when 1/2" nominal pipe was invented, pipes that have the same /outside/ diameter as nominal 1/2" pipe now have /more/ than 1/2" inside diameter. 15mm.
Except that 15mm pipes come in a selection of inside diameters, so most (??) 15mm pipe will not have a 15mm inside diameter either.
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