I just had an intereting conversation with a welding inspector about mirror
welding. The first thing he told me is that with proper planning, mirror
welding is avoided wherever possible. Welds that are going to be hard to do
in place should be done before the job is assembled. Regarding repair welds
on submarines. Present practice is to use flanges in the original
cnstruction, so that pipes can be repaired without a mirror. In any case
where a weld is inaccessible, and is to be rewelded with a mirror, the
welder is required to do the weld on a similar piece, which is then is cut
apart for inspection before the welder is permitted to do the actual repair.
The alternative is to cut out the defective pipe and replace it with a new
piece with flanges.
I won't say that we don't have intelligent people making the decisions
on what to replace and where to cut, but sometimes I have to wonder....
Ask him about sockets and butts. Yes, we do a lot of "pre-fab" (built
in shop or an off-hull work area) work, but there is often a lot of pipe
welding done on the boats.
Present practice? We're repairing / upgrading boats built 30 years ago.
We don't do new construction, and aside from the Seawolf and Virginia
classes, there aren't very many "new" boats pulling into our drydocks.
I don't know which shipyard your inspector is from, but at the one I
work at typically only P1 (high pressure/temperature) or nuc systems
require mock-up training.
Replacing the defective pipe with a flanged pipe means you still have to
weld flanges onto the cut ends of existing pipe.
There are always those "last minute" repairs, too. Test failures,
installation issues, someone working another item dings/gouges a pipe
beyond minimum wall thickness... the list goes on.
Perhaps your inspector is working at a yard (east coast?) that is not
comfortable with allowing the weldors to properly develop and utilize
Mirror welding is not a royal pain in the butt. It is a skill that is
developed by practicing just like any other. There are lots of very
proficient mirror weldors out there, and I have seen several complete
joints that I wouldn't ever want to touch. I enjoy the challenge of
mirror welding, and look forward to opportunities to use the skill,
since it means I don't have to break my back trying to bend around
obstactles to see the entirety of the joint. People who avoid it and
refuse to practice can only expect bad results, and often don't like it
when a proficient mirror weldor completes difficult joints. It makes
those who refuse to try look bad. It's one thing to know your current
limitations, it's another to refuse to attempt to learn a new skill.
"Elephant: A mouse built to government specifications."-Lazarus Long
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