Dec 192010

Damage to number three DG

Let’s start with the good news in the Australian Transport Safety Board, ATSB, report on the catastrophic crankcase fail, explosion and fire aboard  Maersk Duffield in Moreton Bay, Queensland, Australia on 10 December 2009:

“The decision to use the ship’s fixed CO2 fire extinguishing system was prudent and the prompt use of the ship’s fire dampers, remote valves and emergency stops almost certainly reduced the severity of the damage to the generator room… Engine room re-entry and ventilation did not occur until after it had been determined that the fire was extinguished and that it was safe to do so. This occurred almost 3 hours after the fire had started”.

In this case the fire had initially been attacked with hoses and extinguishers until the Chief engineer decided that the fire was too big and that the CO2 system should be used.

Fire spreads with astonishing speed and time is everything. In this case the chief engineer decided, at the right moment, to use the CO2 system and acted promptly.

While CO2 is a very effective smothering agent flammable material may still be above the temperature at which it will self-ignite for a long time afterwards. Letting air reach that material can set the fire off again.

CO2 should left alone to do its job and left long enough, sometimes hours, to ensure that flammables are below their re-ignition temperature.

Here is how it went down:

At about 1312, the trainee engineer, who was cleaning in the generator room, noticed an  unusual smell and heard a knocking noise. He went to investigate and found that oil was leaking from the number five cylinder crankcase relief door on number four diesel generator. He immediately went to find the oiler who was working outside the generator room.

The oiler came to inspect the leak and both men then went to the control room to report what they had seen to the chief engineer. The chief engineer inspected the leak and decided to immediately shut down the generator. He went back to the control room and started the number two diesel generator and synchronised it with the main switchboard. Once number two diesel generator was connected to the main switchboard, he transferred the load from number four diesel generator. When number four diesel generator had been unloaded and disconnected from the main switchboard, he switched it to manual and pressed the stop button.

However, before number four diesel generator had stopped, an explosion occurred and the number five cylinder forward counterweight, piston and connecting rod were ejected from the engine, shattering the crankcase relief door.

The oil vapour escaping from the engine immediately ignited, resulting in a small fireball and at 1320, the ship’s fire alarms sounded.

The heavy debris that had been ejected from number four diesel generator struck number four diesel generator , which was still running, and broke a crankcase door. The fractured door allowed more oil and vapour to be released, adding fuel to the fire.

Following the explosion, the chief engineer left the control room to investigate. From outside the control room door, he could see flames in the generator room. He returned immediately to the control room and telephoned the master and told him that there was a fire in the generator room.

The second engineer and the third engineer tried unsuccessfully to enter the generator room and extinguish the fire using portable extinguishers. They then left the engine room with the trainee and the oilers.

Following the chief engineer’s telephone call, the master informed the pilot of the fire, sounded the ship’s general alarm and made an announcement to the crew using the public address system.

To add to the excitement, at this time, Maersk Duffield was outside the Moreton Bay shipping channels and approaching an anchored gas tanker.

Evidence suggests that that the piston and connecting rod were complete when they were ejected from the engine.

The connecting rod had separated from the bottom end bearing after all four of the palm studs had failed. Both of the forward counterweight’s retaining studs had also failed.

Two scenarios for the failure were considered possible; the initial failure of one or more of the connecting rod palm studs or the initial failure of one of the counterweight studs. From the evidence that was examined by the ATSB, it could not be determined which of the two failure scenarios had occurred.

An overhaul had recently been completed on 4DG. According to the ship’s planned maintenance system (PMS), all of the pistons had been removed, serviced and reinserted into the engine at 18,638 running hours, 48 running hours before the engine failure. All the connecting rod palm nuts were also re-tensioned at this time.
While it could not be confirmed, it is possible that one or more of the connecting rod palm nuts had not been sufficiently tightened during this recent overhaul.

Read the ATSB Report here



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