I think you're right LarryC, It seems to me that the NEC is 'trumped' by the design engineers here at the plant. Is this a good thing?? That question is debateable...
The conduit does have plenty of enamel covering the weld joint though. No rust is visible. I would snap a few pictures for the forum, BUT..I might get into some trouble if I start taking pictures of 'vital' plant equipment.
Wondering about the statement "specificaly designed by it's manufacturer for weld mounting", the hole looks to have been made with a cutting torch, not to pretty. I'll be looking into this further, any more comments would be appreciated, thanks guys & gals.