By Geoff Fein

Following the discovery last fall of welding issues on the pre-commissioned unit (PCU) USS New Hampshire (SSN-778), the Navy and Northrop Grumman [NOC] Newport News (NGNN) continue to work closely on the long-term investigation of Virginia-class submarines, Los Angeles-class submarines, aircraft carriers and in service ships maintained at the company’s Virginia shipyard, according to a Naval Sea Systems Command (NAVSEA) spokeswoman.

“The investigation, which involves a technical assessment of non-nuclear piping systems, should be complete in late spring 2008,” the spokeswoman told Defense Daily yesterday. “The Navy has tested all of the critical Northrop Grumman Newport News-fabricated non-nuclear socket welded joints on current Virginia-class ships.”

The USS Virginia (SSN-774) resumed operations with minimal impact on schedule while repairs on the USS Texas (SSN-775) occurred during Post Shakedown Availability and did not affect its schedule, the spokeswoman added.

“Weld failures were discovered on PCU New Hampshire systems during routine testing. New Hampshire is still under construction and is on track to deliver in late summer/early fall 2008. No new welding issues have been found since November 2007,” she said.

A recent valve replacement aboard the USS North Carolina (SSN-777) was not connected with the welding issue, the spokeswoman added. “The replaced valve was not made to specifications and, for the long-term operability of the system, the Navy decided to have it replaced.”

While the weld issue was discovered during testing on the New Hampshire at General Dynamics [GD] Electric Boat, the weld issue stems from a procedural flaw at NGNN and does not affect General Dynamics Electric Boat, the spokeswoman said.

The exact cost of the repairs to the submarines won’t be know until the investigation is complete, she added.

“However, the cost is currently believed to be not significant when compared to the overall cost of building the platforms (less than $5 million),” the spokeswoman said.

The Navy has tested all of the critical NGNN-fabricated non-nuclear socket welded joints on current Virginia-class ships capable of going to sea, the spokeswoman said.

“Extensive laboratory testing and engineering analysis demonstrates that the worst-case scenario as a result of this problem is that the piping joints may leak at some point in the ship’s service life,” she added. “NGNN assessments of potential short-term impact to submarines have been completed and their assessment of the potential long-term impact will be provided by late spring 2008.”

NGNN is also evaluating the potential impact of this weld material problem onboard aircraft carriers and other surface ships they have worked on, the spokeswoman added.

“NGNN’s evaluation of potential short-term impact to aircraft carriers has been provided to the Navy and their assessment of the potential long-term impact will be provided by late spring 2008,” she said.

The Navy, NGNN and General Dynamics Electric Boat began inspecting welds on Virginia-class submarines around Dec. 10, 2007.

In August during testing of the New Hampshire at Electric Boat, pieces of the submarine built by NGNN were found to have a weld problem. Two months later, a second weld problem led to a joint coming apart. During that event, Electric Boat was conducting an air test of the New Hampshire‘s hull. During the test, the hull is pressurized to see if air is leaking out. It was during the air test that a joint came apart (Defense Daily, Dec. 11).

At the time, the Navy said the problem was due to poisoning of the weld material. It was a stainless steel weld and it was poisoned with copper. That was what weakened the joint to the point where it couldn’t even hold the low air pressure, let alone the high pressure hydrostatic test that would have been done before the system was certified to be ready (Defense Daily, Dec. 11).”

One of the things the Navy found out in its investigation is that copper contamination causes cracking and weakens the weld. That raised the question of how the copper got into the weld.

The root cause was that NGNN welders were allowed to carry two types of weld wire on them. One could be from corrosion resistant steel (CRES) and the other could be nickel copper, which would have copper in it.

Between 2000 and Dec. ’07, the Navy discovered 15 instances in which there had been some contamination of one type or another in a weld where it weakened a weld. The Navy knew about those issues and the welds were fixed.

Out of that subset of valves, inspectors found just a few with contamination: one on the Virginia and one on the Texas. None were found on the USS Hawaii (SSN-776) or the North Carolina (Defense Daily, Dec. 11).