A good reason to take your time building steam

Norway report blames NCL and BV
Craig Eason, 11 December 2007 Lloyds List

THE official report into the cruiseship Norway explosion in Miami in 2003 that killed eight crew members has said that the owner, Norwegian Cruise Line, and class society Bureau Veritas were partly to blame.

The US National Transportation Safety Board report into the boiler room explosion claims that the probable cause was “the deficient boiler operation, maintenance, and inspection practices of Norwegian Cruise Line, which allowed material deterioration and fatigue cracking to weaken the boiler. Inadequate boiler surveys by Bureau Veritas contributed to the cause of the accident.”

Replying to the report, NCL president and chief executive Colin Veitch said: “As evidenced by the highly technical nature of the discussion and the fact it took four and a half years to complete, this was clearly a unique and unusual accident.

“NCL immediately accepted responsibility and compensated all of the victims. NCL does not concur with all of the conclusions in the report, but we are hopeful that its publication will help close this tragic event.”

The incident on the 43-year-old Norway happened when the starboard aft boiler ruptured shortly after the vessel came alongside in Miami after a seven-day Mediterranean cruise. The boiler contained about 20 tonnes of water, at 275 degrees centigrade under high pressure. When the fracture occurred, the water was released into the normal atmosphere of the engine room, turning to steam as it expanded 1,260 times.

This steam, mixed with smoke, soot and debris, swept through the engineering spaces, killing four crew and a further four in lower accommodation areas. As the steam rose rapidly through the boiler room, it entered other crew accommodation and work areas, injuring 17 more.

Built as the France in 1960, the vessel was originally fitted with eight boilers. Four were removed when the vessel was purchased by NCL in 1979.

During normal steaming in the Caribbean two or three were used during voyages, depending on requirements, while the fourth remained shut down. This process of cycling is what investigators believe contributed to the catastrophe.

The investigation found that engineers did not follow the boiler manufacturer’s instructions for shutting or cooling them down, often opening vents and starting forced air fans to speed the process.

Experts believe excessive cooling down and reheating of boilers too quickly can lead to increased stresses and subsequent fatigue.

The report also identified inadequate levels of hydrazine, a chemical used to reduce oxygen levels in the water. Oxygen causes corrosive pitting which was discovered during the last inspection by Harris Pye, a boiler repair specialist, mere months before the accident.

Investigators also discovered evidence of copper being used in the boiler drums where the fatal fracture occurred. Copper is not used as a weld or repair material, and the investigators concluded that the metal could only have been used to mask cracks or signs of fatigue.

Additionally, the boiler access hatches for inspection and maintenance were found to be too small for access by some crew or surveyors.

According to class society rules, if a boiler has not been surveyed internally hydraulic tests are required. This involves filling the boiler with water, sealing it and applying a specified test pressure using a feedwater or hydrostatic pump. Typical test pressure is around 80 bar.

“According to documents the boiler was subjected to a 70 bar hydraulic test with the previous inspection in 2001 not involving a hydraulic test,” The report says. “Thus BV did not appear to follow its own rules regarding hydraulic testing”.

BV director of communications Philippe Boisson defended the society’s position, saying BV applied its existing rules concerning boiler inspection and testing. “In particular, the vessel’s last hydraulic test in July 2002, was conducted well above working pressure and safety valve setting,” he said. “Since the accident BV has taken steps, as have other classification societies, to improve rules and procedures applicable to older boilers.”

Norway was one of the last steam-powered cruiseships in the region at the time and after the accident it was removed from service and eventually scrapped.

However, the report may also pose questions about the maintenance of the 230-strong steam powered liquefied natural gas fleet, which includes some vessels more than 30 years’ old.

Read more about the history of the SS Norway from Maritime Matters. You can also download a video tour of the engine room from our Martin’s Marine Engineering Page Video Vault. You can download the full NTSB report here.

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