This is coolbert:
From Strategy Page an update and further clarification regarding the recent problems as encountered by the American Virginia class submarine. My emphasis in all cases:
"Submarines: Yet Another Construction Failure"
"August 20, 2015: The U.S. Navy continues having problems with quality control (QC), or, rather, the lack of it. The latest incident was revealed on August 5th when the navy ordered its three most recently built Virginia class subs to restrict their operations until ten suspect (of being substandard) sections of pipe can be inspected and, if necessary, replaced. There are another 40 of these components in subs under construction but taking care of those won’t delay submarine operations."
"The QC problem has been getting worse since the 1980s and one 2009 incident became widely known. In this instance a welder at the Quonset Point (Rhode Island) shipyard performed substandard welds that were not caught immediately by the quality control system. These welds were not in critical areas but at least one sub already in service was involved."
"Earlier in 2009 a weld inspector at the Newport News shipyard was found to be falsifying the inspection of welding jobs on four Virginia class submarines and a Nimitz class carrier. Some 10,000 welds had to be re-inspected, as these are how many the now dismissed inspector handled in four years on the job. Each Virginia class sub has about 300,000 welds that have to be inspected. Normally, only a few will fail inspection and have to be redone. A few defective welds can cause the loss of a submarine, or serious damage aboard a carrier."
NOT SO MUCH WITH SURFACE VESSELS BUT WITH SUBMERSIBLES THE DANGER AS POSED BY THESE IMPROPER WELDS MOST ACUTE. VITAL!
That USS Thresher from decades ago lost and it is thought gone to the bottom because of a pipe-joint incorrectly silver-soldered. That pipe-joint having passed through it sea water under pressure. A failing joint spraying sea water on vital electronic and electrical components, the submarine unable to recover from damage fast enough. SINCE THAT TIME OF THE THRESHER SUCH PIPE JOINTS NOW WELDED. [for whatever good that does if the joints defectively welded!!!]
Keep in mind the modern nuclear powered submarine the MOST COMPLICATED THING MADE BY MAN!! Piping of whatever sort and joints I might assume also hidden from view in the aftermath of completion and launching. Inspection not easy to perform after the fact. A whole lot of the sub must be taken apart to get at each of those joints? Of this I am not sure but have a sneaking suspicion it is so!!