Fire aboard the U.S. flag seismic research vessel Casey Chouest

Summary

In the early morning of 31 January 1996, Casey Chouest, an offshore research vessel engaged in seismic survey operations, was in the prospect area known as Snark 3D, close to Thevenard Island in Western Australia. At about 0700, the fire alarm panel in the wheelhouse indicated a fire in the seismic compressor room space and smoke could be seen coming from the vents.

The crew and seismic staff mustered and closed down the space, starving the fire of oxygen and applying boundary cooling; eventually extinguishing the fire in the space. However, heat from the fire was conducted through the uninsulated steel bulkhead igniting combustible material stored against the common bulkhead in an adjacent space. The firefighting tug, Total Endeavour, was sent to the scene in response to a request from the Master and, using its fire monitors, applied boundary cooling to the hull while the crew continued boundary cooling on board.

The investigation established a sequence of events initiated by a massive short circuit in the cable from a dedicated generator supplying power to the hydraulics for the reels which deploy the seismic gun cables. An incorrectly sized bracket, securing the armoured cable had caused damage to the armouring and the rubber sheath surrounding the three phase conductors. The evidence indicated that the insulation breakdown had proceeded over a long period until the cable failed to perform under normal load conditions. The evidence also indicated that the fault current started to flow from one phase to the earthed bracket. This earth fault increased over time causing heating of the cable conductors in the section of cable adjacent to the bracket. This, in turn, contributed to the complete failure of the cable due to phase to phase and phase to earth fault current.

As the trip settings on the circuit breaker were set far too high, it did not trip, and the cable fault imposed a fault current level on the generator high enough to momentarily cause a locked rotor condition in the generator. The high inertia from the generator caused mechanical failure of the bottom end bearing in no.4 unit. The connecting rod came through the side of the crankcase and pressurisation of the crankcase blew much of the sump oil, out of the hole in the side, over the D399 Caterpillar engine below and to starboard of it. The oil self-ignited on the turbo-charger casing of the D399 engine and burning oil in the bilge melted the polycarbonate bowl of the forward fuel filter on the D399, allowing fuel under pressure to escape and spray over the engine and into the bilge thus adding to the fire.

The burning fuel in the bilge flowed to the starboard aft corner of the seismic machinery room, against the space in the reel-room where large numbers of oil filter elements were stored in cardboard cartons. These stores were ignited by heat conducted through the uninsulated steel bulkhead.

The fire was extinguished at about 1045, approximately 3 hours after the first alarm.

Conclusions

These conclusions identify the different factors contributing to the fire on board Casey Chouest and should not be read as apportioning liability or blame to any particular organisation or individual.

The fire in the seismic compressor room and the adjacent space resulted from a number of factors that combined to initiate and spread the fire. These include:

1. The breakdown in insulation initiated by securing the electrical cable from the seismic generator with a bracket of the wrong radius.
2. An undetected earth fault at the bracket led to a progressive breakdown in cable insulation and eventually to a short circuit between phases.
3. The lack of electrical planned maintenance on board, in particular with regard to the routine testing of electrical cable insulation on board the ship.
4. A lack of appropriate supervision in fitting the circuit breaker and the incorrect trip settings (thermal and magnetic) rendering it unable to protect the cable or the generator under either full load current condition or under fault conditions.
5. The sudden load thrown on to the D343 Caterpillar diesel engine by the short circuit, on an engine in very poor condition caused the failure of no.4 bottom end bearing and the subsequent damage to the side of the crankcase.
6. The pressurisation of the crank case due to worn piston rings and cylinders, causing the sump oil to spray over the turbo charger of the adjacent Caterpillar D399 diesel engine.
7. The lack of a proper maintenance regime and standard operating instructions covering the operation of the Caterpillar D343 engine.
8. The use of polycarbonate, instead of steel, fuel filter bowls and the absence of a remote fuel shut off allowed fuel under pressure to feed the fire in the bilge.
9. Lack of bulkhead insulation allowed the heat of the fire to be conducted through the adjacent bulkhead, igniting combustible stores stowed against it.
10. The containment of the fire and associated smoke and fumes was made more difficult by the number of openings in the seismic compressor room, including the penetrations in the bulkhead to the reel room and the open conduits which ran through to the accommodation.
11. A poorly defined relationship over time between the owners and the various charterers, resulting in the ad hoc selection and fitting of machinery and cables without an overall safety oversight.
12. The lack of the adoption of a suitable standard or practical safety assessment approach, by either the vessel's owners or charterers, when designing, constructing and equipping the seismic compressor room.
13. The lack of any required standard, safety survey or safety overview by the flag State, to vessels engaged in international commercial activities, particularly in view of the nature of the operation and the number of people at risk.
14. The reliance upon a 'grandfather' clause when applying the national tonnage to avoid having to apply appropriate standards to the detriment of the safety of personnel on board.
15. The absence of an appropriate inspection regime to cover vessels operating under the provisions of a "grandfather" clause.
16. The absence of a safety system to take into account appropriate standards for the fitting and maintenance of machinery or other equipment not considered to be ships' equipment.

The Inspector considers, under the circumstances, the fighting of the fire was performed efficiently, by both the ship's staff and PGS personnel, and the decisions taken in the circumstances were sensible and in the best interests of the vessel. However, it should be noted that the risk to personnel and the ship was increased by the limited number of compressed air bottles available to the firefighting team.