Comments about technological history, system fractures, and human resilience from James R. Chiles, the author of Inviting Disaster: Lessons from the Edge of Technology (HarperBusiness 2001; paperback 2002) and The God Machine: From Boomerangs to Black Hawks, the Story of the Helicopter (Random House, 2007, paperback 2008)

Friday, September 13, 2013

Costa Concordia: Ready for the big pull

Readers of Disaster-Wise may know that I'm a fan of heavy rigging and the related work of collapse rescue, because such projects demand ingenuity, practical knowledge, and nerve. Through the years my writing research has taken me to rigging sites including collapse scenes, tunnels, towers, and derailments.

Photo: Parbuckling Project
In the heavy-rigging news this week: almost 20 months after Costa Concordia blundered onto the rocks off the island of Giglio, Italy, drowning at least 32 people, Italy's Civil Protection Department has given the Titan-Micoperi joint venture permission to pull the Costa Concordia upright, which (if the ship holds together) will allow a row of steel flotation boxes called sponsons, welded to the sides and bow like water wings, to ease it off the seabed so that tugs can haul it to a breaker's yard.

Weather permitting, the job of setting Concordia upright could start on Monday morning, September 16, local time. It will take the better part of a day to execute. Rest assured that hundreds of media reps will be watching from land, sea and air, so you won't miss anything.

The salvors will use computer-controlled strand jacks, wire rope, and sponsons to roll the ship very slowly from its capsized position. Right now it's laying on the starboard side, 65 degrees off vertical. If the parbuckling works as intended, the ship will come to rest in one piece, grounded but now upright on a temporarily leveled seafloor. (The leveling work was done with big bags of cement grout and giant steel frames, all of which will be pulled out later. Only anchor holes will be left in the reef, we are told.)

The groundwork should help keep the ship from breaking in half, as it would surely do without the leveling job, since the hull came to rest on two underwater promontories.

Here's my summary of the parbuckling plan. It will need three moving forces:  a row of flotation tanks welded to the port side of the ship that will serve as a downward force when flooded, and two sets of tension rigging on opposite sides of the ship. (By "rigging” I mean the full set of blocks, wire ropes, chains, anchors, and computer-controlled strand jacks.)

Here's a strand jack:

Now for the moving machines.

1) Parbuckle rigging: These are visible as a set of cables on the portside, the side facing the open sea. They will haul the ship upright most of the way, until weight from the flotation tanks (aka sponsons) take over. Specifically, strand jacks mounted on the sponsons will slowly take up cables whose other ends are anchored to underwater steel frames that make up the temporary seabed foundation.

2) Holdback rigging. This will keep tension on the bottom of the hull. Strand jacks will be visible on anchor towers on the starboard side. (Starboard is the side facing the seashore.) The main job of the holdback rigging is to keep tension on the hull nice and even, and to keep the ship from sliding across the temporary seabed, destroying the underwater platforms, and then rolling down the slope in reaction to the pull from the parbuckling cables.

3) Flotation tanks on the starboard side. These will flood to provide seawater ballast at the time of the parbuckling. (Later, for the tow to salvage, they will be pumped out and provide buoyancy for the flooded hull.) Apparently this ballast is necessary to bring the hull down to the seabed, because the ship's compartments will still have some buoyancy as the parbuckling begins.

There are several risks associated with this work, and I'll go into that in another post.

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