The Australian registered tanker Australian Achiever, of 127,575 tonnes summer deadweight, cleared the New Zealand port of Whangarei for the port of Brisbane at 2030 on 7 November 1992. The ship had part discharged and retained on board about 35,000 tonnes of crude oil.
At 2230, the exhaust gas uptake high temperature alarm sounded and the temperature reading was seen to be 10 degrees Celsius above the alarm setting. The engine was slowed to reduce the temperature and the waste heat unit was inspected for hot spots. None were found and the engine speed was increased at 2345.
At 0115 on 8 November, when about 11 miles from the nearest land, the exhaust gas alarm sounded again and the main engine revolutions were reduced. A further inspection of the waste-heat unit revealed a small area glowing red at the forward, inboard corner. The main engine was stopped and the crew were alerted.
The fire within the waste-heat unit could not be fought directly and the main fire fighting effort concentrated on boundary cooling. After fire burnt a hole through the casing, several portable C02. extinguishers were discharged into the unit through the hole, without effect.
The ship's engineers initiated the proper established procedures and stopped the engine. Although the weather was favourable and the current tended to take the ship offshore, given the proximity of the land and the nature of the cargo, the Master requested that a tug be made available to tow the vessel back to Whangarei.
The fire in the waste-heat unit had reached such an intensity that areas of the generating section's steel tube banks, and a small section of the steel casing reached fusion temperature with resulting meltdown of the materials.
At daybreak, the crew prepared for the tow by hanging off the starboard anchor and ranging the anchor cable. A tug arrived at 0955 and the tow was connected at 1132. By 2100, the ship had been brought safely to harbour and it subsequently anchored in Bream Bay.
The fire was contained throughout 8 November and into 9 November by boundary cooling. It was extinguished by 1515 on 9 November, but it was considered prudent not to open up the unit until the area had cooled further. in all the fire burnt for some 39 hours.
Officers of New Zealand's Ministry of Transport, Maritime Transport Division, were appointed by the Inspector to undertake an initial investigation on behalf of the Australian Department of Transport and Communications.
1 The fire occurred as a result of a combination of factors:
(a) The washing process failed to remove all soot deposits
(b) The dampers isolating the tube banks from the main stream of exhaust gas did not dose properly, allowing hot low velocity gas to ignite the soot deposit
(c) The lack of water circulating in the generating section may have contributed to the loss of the tubes, as there was no water to carry away the surface heat generated by the soot fire on the external surfaces of the tubes.
2 The original decision to isolate the waste-heat unit tube banks and run with the economiser dry was reasonable and not open to criticism.
3 Design problems related to cleaning of waste-heat units have been known for some years, nevertheless, the unit had operated without a fire since about 1984. The importance of regular washing was well understood by the ship's staff and there was accepted criteria, based on inlet and exit exhaust gas temperatures. governing the necessity of washing the unit. But temperature differential would not indicate the presence of isolated areas of soot compaction.
4 There is no evidence that the failure to wash the unit at Ras Tanura resulted in excessive soot deposits. The only evidence is that sufficient soot remained or had compacted in one area after washing at Whagarei to cause a soot fire. However, the strong possibility that more soot than normal had accumulated can not be discounted.
5 Neither the maker's nor the owner's/operator's instructions reflected the reality of cleaning the waste-heat unit under operational conditions, but this deficiency is not considered to have contributed to the cause of the fire.
6 The actions taken by the Master to alert the New Zealand authorities and to place tug assistance on stand-by was timely and correct.
7 The actions taken by the Chief Engineer and the engine room staff in stopping the engine and blocking associated apertures was correct and in accordance with the makers instructions.
8 The fire fighting operation was efficient and effective, reflecting credit on the organisation of all the ship staff involved.
9 The Master's decision to pump the ship's bilges direct to the sea was a proper decision given the circumstances and priorities relating to Australian Achiever at that time.