Shortly after berthing at West Swanson dock, Melbourne, on 24 September 1993 the 13280 grt container and general cargo vessel "Iron Flinders", on charter to BHP Ltd, suffered a fire in the waste-heat unit (economiser) which is situated in the main engine exhaust trunking at the base of the funnel.
The fire gained sufficient hold for an hydrogen-iron fire to become established, and the internal tube banks of the unit were completely destroyed before the fire was extinguished some eight hours later by the Melbourne Metropolitan Fire Brigade, assisted by the ship's staff and the use of over 8 tonnes of liquid carbon dioxide.
The investigation revealed a combination of several factors which played an important role in causing the fire. The main ones were:
Poor maintenance and operating procedures, due in part to the inadequate provision of on-board instructions and information and, in part, to a lack of instrumentation on the waste-heat unit.
The initial response to the fire revealed considerable uncertainty about, and a lack of specific training for, this kind of fire on the part of the ship's staff. It also revealed some inadequacies in the type of fire-fighting equipment fitted in the vessel.
1. The fire occurred as the result of a combination of factors:
in order for the fire to have occurred, there must have been a build-up of soot within the unit. The production of soot in the exhaust gas was probably exacerbated by three factors, namely:
The first two of these may have caused fouling of the waste-heat unit over a prolonged period.
The measure employed to assist in the prevention of fouling was the use of Drew Ameroid "LT' soot release powder injected into the bottom of the unit every third day. The effectiveness of this treatment would be reduced if there had been significant oil vapour carry over.
With the inadequate arrangements for thorough inspection of the unit and no provision for water-washing, the quantity of deposits within the more inaccessible areas of the tube nest could have been considerable.
The only method employed for cleaning the unit was that of soot blowing, carried out twice daily. The check-off sheets, however, which were filled in by the Duty Integrated Rating for the two days at sea prior to arriving in Melbourne, that is the 22nd and 23rd September, indicate that the unit was soot blown only once on each of those days, instead of twice as was the routine.
Ignition of the accumulated soot could have been caused by either high exhaust gas temperature or by sparks carried over from combustion into the exhaust gas stream. The engine manufacturers, MAN-B&W, have stated in one of their service letters that "oil-wetted soot" may ignite at temperatures as low as 150° Celsius. If the fire, as is most likely, had been smouldering for some considerable period before "Finished with Engines", then the action of shutting down the feedwater circulation would have assisted the fire to gain a hold by stopping the only means by which the heat of combustion was being removed from the tube banks.
2. The lack of information provided by the manufacturers on keeping the tubes clean if part of the unit was to be run in the "dry" condition, is considered to be a contributory factor to the incident. Similarly, the absence of any instructions from the owners, following similar incidents in recent years, emphasising the importance of maintaining waste-heat units in clean condition to minimise the risk of soot fires, is also considered to have been a contributory factor.
No regular monitoring of the degree of fouling of the unit was carried out. The temperatures of gas flow into and out of the unit were not recorded and no instrumentation was fitted for measuring the pressure differential of the gas flow through the unit . Had the remote alarm for "Uptake Temperature High" been connected, an earlier warning of the fire would have been received.
No information was available on board, either in the equipment manuals, owners orders, or operating instructions concerning the means by which to fight this type of fire. This is considered to have contributed to delays in tackling the fire by the best means in the early stages.
No reports of similar incidents had been passed to their fleet by the vessel's owners, neither was this type of fire covered in the fire training courses undertaken by the ship's staff.
The ship's fire hoses carried in the engine-room, although complying with the requirements of the regulations, were not the most suitable size for use in this situation. Similarly, the nozzles, of East German design, gave a water flow rate and cone angle not well suited to the cooling of surfaces in confined spaces.