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Nansen-class frigates fatally flawed?

Grey Havoc

The path not taken.
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https://www.defensenews.com/naval/2018/11/29/early-report-blames-confused-watchstanders-possible-design-flaws-for-norways-sunken-frigate/

The Accident Investigation Board Norway, or AIBN, issued a public addendum to the report and a pair of warnings that the issues that sunk Ingstad could also apply to other Navantia ships, raising questions about a widespread quality issue at the Spanish shipbuilder.

“The AIBN has found safety critical issues relating to the vessel’s watertight compartments,” the report reads. “This must be assumed to also apply to the other four Nansen-class frigates.

“It cannot be excluded that the same applies to vessels of a similar design delivered by Navantia, or that the design concept continues to be used for similar vessel models. The AIBN assumes that its findings are not in conformity with the required damage stability standard for the Nansen-class frigates.”
In the addendum to the report, the board found that the initial assessment by the crew in the wake of the accident was that some crew quarters, the aft generator room and the ship’s stores room were flooded, but that the ship was stable and could survive if the situation remained relatively controlled.

But then it didn’t.

The crew began seeing water quickly flooding into the gear room via the ship’s hollow propeller shaft, with flooding then creeping into the engine rooms through the bulkheads.

Propeller shafts have to pass through multiple engineering spaces through watertight openings in the wall known as stuffing tubes or stuffing boxes that are supposed to tighten down as water tries to get through, preventing progressive flooding.

The board’s initial assessment based on crew interviews is that the stuffing boxes did not work as designed on Ingstad.

“This meant that the flooding became substantially more extensive than indicated by the original damage,” the report reads. “Based on the flooding of the gear room, it was decided to prepare for evacuation.”

As a result of the findings, the AIBN issued two warnings: one to the Norwegian military to assess its ships to address the safety concerns, and one to Navantia to “conduct investigations into the issues identified during this initial investigation and to ascertain whether this is also an issue relating to other vessels.”
 
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