In its report on dealing with cargo fires, the Swedish Club has focused on cargo fires and explosion that can be caused by cargo hold lights presenting a case study of a bulker that caught fire after its cargo floodlights were not connected according to the approved ‘as built’ circuit diagrams.
Overall, many are the bulk carrier/general cargo holds that have fixed cargo lights; These lights can easily ignite combustible cargoes such as grain, animal feed, wood chips, pulp and paper if they are too close to the light. Self-decomposition of fertilizer has been initiated in this manner.
Therefore, prior to loading cargo, cargo lights in holds should be properly isolated. This can be done by:
- Removing fuses or other physical links in the electrical circuits so that the lights cannot be switched on by mistake.
Also in container ships:
- need to be properly placed so that they do not overheat cargo or other combustibles and thus cause damage or fire.
Lights in car carriers and ferries:
- the lights are usually fluorescent, which are unlikely to cause ignition.
Nonetheless it makes sense to leave lights switched off when they are not needed, particularly in cargo areas where combustibles are present.
Following, the Swedish Club presents a case study explaining how a cargo hold light can lead to a fire.
A bulker loaded sugar beet pellets in its three cargo holds during a 27-hour operation. When the workers completed the loading operation, the ventilation hatches and all other access points to the cargo holds were secured. In cargo hold 1 there were two metres of space between the cargo and the cargo hatch. In cargo holds 2 and 3 the cargo was almost up to the bottom of the hatch coaming.
Yet, the second day of the voyage, the crew noticed smoke from cargo hold 2. The crew discovered hot spots in hold 2 on the transverse hatch coaming, both forward and aft on the portside, and an additional hot spot was also discovered on hold 3 on the transverse hatch coaming, on the portside aft.
All hot spots were located adjacent to recesses in the coamings for the cargo holds’ floodlights.
Therefore, the crew isolated the electrical power to the floodlights. Because of increased temperature, the master released CO2 in the hold. The CO2 did not take out the fire but reduced its severity for a while. When the vessel arrived at the discharge port the cargo hatches were opened and flames broke out from hold 2.
The hold 2 had been affected by the fire as its top layer was burned; Yet, the cargo, located four metres below the cargo surface, was in good condition. Yet, hold 3 was damaged by condensation and tainted by smoke.
The crew saw clear burn marks around the floodlights and distinct burn marks by the coaming at the same locations where the hot spots had been discovered. The floodlights were situated 1m below the cargo surface in holds 2 and 3 and there was black, burned cargo covering the floodlights.
All the floodlights were installed in recesses in the hatch coaming and were protected by round bars preventing crane hooks, grabs etc from hitting them, but these bars do not prevent cargo like sugar beet pellets from covering the lights.
Moreover, the floodlights were controlled from the bridge. Yet, the investigation showed that it was unclear which lights each keyswitch controlled.
The subsequent investigation concluded that the cargo floodlights were not connected according to the approved ‘as built’ circuit diagrams delivered with the vessel.
It was not clear on board which lights were controlled by which keyswitch. The fire was caused because a number of cargo lights were operating while cargo covered them, so the lights ignited the cargo. There was a lack of information on board about how the light circuits were connected and how the light system should be operated. There was also a lack of records concerning use of the lights.
