The ID bevel is on both surfaces and we have a cross section. You can see a 0.5mm hole right at the corner where the pipe meets the fitting. Inside this hole what you have is the void / gap between the pipe and fitting.
We are currently in fabricating a project that consists of about 5000 socket welds. Recently the client have X-rayed abot 60 welds to check the gap. The results for the gap were 100% clear. However they found a "lack of penetration" right in the corner of the weld on about 30 welds.
On further...