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PostHeaderIcon ... The case of a lifeboat davit

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This is a case of a lifeboat davit mismanagement, a case of erroneous engineering, a case of a lacking foresight, a case for a need to improve on type-approval process . This was NOT an isolated incident, not with this company, not with davit manufacturer, not with similar arrangements from other manufacturers. It gets worse, there has been no significant developments (to my knowledge) that effectively fixed the cause. In my view, it is a failure on the part of industry's governing bodies, that allow such design to reach the end user - the seafarer.

 

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What happened?

During a lifeboat drill port boat was lowered to the embarkation deck. At this point there was no indication of any problems. Then the lifeboat was hoisted into its stowed position. As soon as limit switches deactivated the hoisting motor, lifeboat started to decent without warning. No personnel involved in this particular drill, had ever experienced such a behavior before and for safety reasons, stepped away and let things fall.The vessel was a new VLCC in a loaded condition, under way, cruising at about 14 knots off the Eastern coast of Africa.

The result?

Lifeboat hit the water, got caught in the ship's wake, turned sideways and continued to pull the wire falls off the drums. Once all wire was off, the impact force bent the davit arms (as shown) and eventually one wire unhooked itself from the boat's hook, the other broke somewhere along its length. The boat ended up floating upside down and after several ill-advised attempts was left at sea.

The cause?

This is about an enclosed lifeboat that can be lowered from the inside by pulling on a control wire that lifts the brake off the winch. The wire on the inside of the boat was normally snaked through 3 studs on a triangular handle. Although the instructions were not clear, it was quite apparent that the arrangement called for a loose fit around the studs, so if the relative length of the wire inside the boat changed, it could slip through the studs. It also allowed for the wire to slip out of the boat once launched. The problem was that a third mate in charge of life saving equipment had a different idea and wrapped the wire around the handle, which made it rigidly attached with no possibility of slipping out. I need to state here though, that boat instructions where not focused on this set up at all, so it was not obvious what such a change would do to winch's behavior.

As it turned out, the control wire was coming off a spool piece that was attached to the wire fall drum and was turning along with it. There was no wire guide of any kind which meant, that the wire was NEVER stowed on the spool in the same or repeatable way. In other words as the wire was coming off the spool to follow the boat, it would NEVER pay out at a predictable pace. In turn, with the ever changing effective length of the control wire, its length inside the boat would change, and the triangular handle would "float" up & down during the lowering process. Often it would go as high as boat's overhead.

Now, had that wire been simply snaked through the studs to allow for slip out, once the handle is against the overhead, it would slip off the handle. Since in this case it was not, once the handle jammed against the overhead, it held the brake open. You would think that stepping on the brake lever would stop the boat. This was attempted in this case and some cases prior. Unfortunately, once the handle is hard against the overhead, it does NOT give at all. The boat continues its uncontrolled decent and there is ONLY ONE solution. You MUST grab the running wire above the spool and throw off a layer or two. This gives wire enough slack to drop the brake back onto the drum and stop the fall.

Solution?

  • read manufacturers instructions and follow it to the letter, however, if something in the instructions does not make sense or appears incomplete, ask for clarification, this could come from the ship's staff, the shore office, or the manufacturer, but NEVER assume, that if something is not explained in the manual, it must not be important
  • use common sense, and as in this case, think of the consequences if you change an arrangement, here we had a mate who looked at a proper set up (not knowing it was such) and decided to change it, without consulting any one on the vessel

The casualties involved in this accident could have been a lot more significant. In the end we had lost a lifeboat, temporarily replaced it with two life rafts, and eventually put the vessel out service to make the necessary repairs and install a new lifeboat.

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Last Updated (Monday, 04 April 2011 02:12)

 
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