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Isolation of fuel tanks

IMCA has been advised of a near-miss accident that occurred during a fuel transfer operation. Whilst the vessel was in dry dock, fuel was accidentally transferred into a tank in which hot work was planned. As a result, around 7m⁳ of marine diesel oil was spilled onto the dock via an opening in the tank and the hull of the vessel. No people were working on the dock at the time, nor were there personnel inside or in the vicinity of the tank.

The situation occurred with a lock-out/tag-out procedure and a permit to work both in place. Such systems should have functioned as barriers against the unintended flow of fuel in an open tank.

After investigation of the incident, the company decided to change the isolation requirements for entry into a fuel tank. It made the following recommendations:

  • When access to a fuel tank is required for maintenance or cleaning activities, all fuel inlets should be blind flanged;
  • Isolation by means of blind flanges should be reflected on the permit to work;
  • Isolation tags should be logged, using the drawings of the fuel system as guidance;
  • Information on the status of open tanks should be known in the engine control room and on the bridge;
  • All isolation points for each tank should be identified and known.

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