For the last couple of decades I have worked in an industry that prohibits the use of backing strips in Pressure Vessels. Why?
OK, I know what backing strips are for, and when they are appropriate, but I do not understand why there is such a 'downer' on them in Oil/Gas.
A few years ago I visited a first class German shipbuilder (not Oil & Gas, of course) who welded, bombed, sliced and macroed a small diameter weld with permanent backing strip for me - perfect fusion and no inconsistencies in the RT. I had a similar experience at a very reputable Italian pressure vessel manufacturer, also with a weld which was inaccessible for back-gouging for the 2nd side.
So why do people have such a problem with backing strips? I could NOT fault the RT versus the macro from that shipbuilder. The radiograph was PERFECT (IMO). The backing strip was fully attached to the pipe, both by fusion with the weld itself, and by the continuous fillet that attached it to one part of the pipe. Absolutely perfect welding. Do people assume that GTAW roots are necessarily essential when the second side is not accessible for back-chipping?
Mech Engr, not welding engineer asking ......