202517 Ferry car deck collapses
As edited from SHK (Sweden) report 2024:13A ferry was in port loading vehicles and passengers. The ferry was equipped with mobile decks that could be raised or lowered to load cars above the main deck. At the time, the automation for operating the mobile car decks was not functional so these decks had to be raised and lowered by manually operating the levers in proper sequence.
The crew member performing the task on this day had not done so for some time and the written instructions were not in the working language of the crew. The crew member pulled in the locking wedges for the platform too early, an ’out of sequence’ manoeuvre. This resulted in the platform falling freely for a short distance, putting high stress on the lifting cables and mechanism. One of the sheaves of the lifting cables was torn loose by the increased stress. The spacer plates that were supposed to hold the two steel plates of the line sheave together broke under the load. Now, there was nothing to hold the cables in place and one side of the mobile deck fell to the main deck. A car with a trailer was crushed and two people suffered minor injuries.
The investigation showed that there are no requirements for independent inspections of platforms for suspended (mobile) decks. However, requirements do apply to ramps that are defined as ’lifting devices’. Mobile decks have a similar technical design to lifting ramps and the risks associated with construction and use are similar. The disparate regulatory requirements for mobile decks versus lifting ramps do appear to be justified from a safety perspective. Similarly, there was no requirement for protection against wire breakage for suspended decks, whereas there is such a requirement for ramps.
The investigation also found that there were no technical measures to prevent the locking wedges from being pulled in before the platform had been raised. Finally, there was nothing to prevent people from being under the mobile decks during operation. This aggravated the consequences of the accident.
Lessons learned
- There is no substitute for good training and complete familiarisation with the equipment being used. In this case the crew member’s training in the operation of the mobile deck was less than adequate.
- Allowing people to remain under the mobile decks when the decks were being operated is a sign that better risk assessments are in order on this vessel and possibly others of similar design.