Norway boiler suffering from ?significant material failure?

National Transportation Safety Board (NTSB) investigations into a boiler explosion on the Norwegian Cruise Line vessel Norway, which killed seven crewmembers and injured about twice that number, have found a water wall header suffering from significant material failure.

The pace of the investigation has been slowed by the need to protect investigators from the large quantities of asbestos in the damaged boiler room as well as by the poor access, heat and ventilation.

The force of the explosion ruptured the outer casing of the boiler, allowing the interior of the boiler to be visible on the starboard aft section. The explosion knocked out and opened doors three decks above the boiler. In the areas adjacent to the boiler room on the starboard side, there was significant physical damage to bulkheads, doors and doorframes.

The suspect header is one of three separate drums running the length of the boiler. The header helps the circulation of the boiler steam-water cycle.

NTSB interviews with the ship?s engineering officers indicate that they had not observed anything unusual in the boiler room or in the operating console prior to the explosion. The explosion occurred on May 25 while Norway was moored in the port of Miami, Florida. No maintenance was underway on the boiler at the time.

Four crewmembers remain hospitalised, according to Norwegian Cruise Line, one in a critical condition. The cruise line plans to reintroduce the ship despite the accident and its 42-year age, although not until October 5.

The Chantiers de l’ Atlantique, Penhoet-Loire built boiler is one of four on the ship. It supplies superheated steam for vessel propulsion at a pressure of about 900 psi. The boiler underwent a complete class survey by Bureau Veritas in July 2002.