Dynamic Duo

24 May 2022

Tandem lift for Vernazza Autogru’s Demag lattice boom crawlers.

Italian crane service provider Vernazza Autogru used its CC 3800 1 and CC 6800 Demag lattice boom crawler cranes, plus a Tadano TC 2800 and AC 250-1 for secondary duties, to disassemble an old gantry crane at the shipyard facilities of Italian yacht builder The Italian Sea Group.

The shipyard is located on the Apuan coast in the Italian province of Massa-Carrara and the gantry crane has been a landmark there for decades.

The gantry crane had a height of 46 metres and dismantling it involved lifting a load of over 1000 tonnes and a length over 105 metres and travelling with it whilst manoeuvring through the shipyard.

To get to the shipyard the CC 6800 was transported there from the new Vernazza logistics centre in Vado Ligure, while the CC 3800 1 came from central Italy, where it had been installing a railroad bridge. It took around two weeks to get the cranes there, with the smaller components being transported by road and some of the bigger ones by ship. “This enabled us not only to minimise the time it took to get the cranes to the site, but also to adhere to the customer’s timeframe,” job manager Giulio Zunino reports.

Once at the shipyard, the CC 3800 1 was set up with an SSL_1 configuration, a 78-metre lattice boom, 50 tonnes of central ballast, 165 tonnes of superstructure counterweight, and 285 tonnes of Superlift counterweight. The CC 6800 was set up with an SSL configuration, a 66-metre lattice boom, 80 tonnes of central ballast, 250 tonnes of superstructure counterweight, and 400 tonnes of Superlift counterweight. Setting up the cranes took ten days and ten assembly technicians.

Access to the site and the setup area was restricted as shipyard operations were still ongoing plus work also had to be coordinated with other construction activities renovating the shipyard.

Before the cranes could carry out their work a level area had to be prepared so that the cranes could operate safely. An area of approximately 34 by 16 metres was prepared for the CC 6800 and an area of 105 by 18 metres prepared for the CC 3800 1. This area for the CC 3800 1 was actually in a dry dock, which meant that the CC 3800 1 ended up nine metres below the gantry crane’s rails when working.

Readying an area this big on which the crane could travel was necessary, as the 105-metre-long main girder had to be set down on the dry dock for the last bit of disassembly work, so the CC 3800 1 had to be able to travel there with the load on its hook. The CC 3800 1 in the dry dock was equipped with a longer main boom than the CC 6800 to compensate for its lower working position.

In order to reduce the ground pressure underneath the cranes, two wooden crane mat strips made of ekki were set down for the CC 6800, while the two crane mat strips for the CC3800-1 were made of steel plate.

Vernazza used two different sets of slinging gear for the tandem lift. Both of them were custom-made for the job and positioned across the underside of the gantry crane’s main girder. For the CC 3800 1, this meant a single spreader bar that was rigged to the crane with two shackles featuring a load limit of 300 tonnes each and a pair of endless wire rope slings, each with a length of 32 metres and a rated capacity of 218 tonnes, arranged in each shackle.

For the CC 6800, the assembly comprised a double spreader bar that was rigged with four shackles featuring a load limit of 300 tonnes each and a total of eight endless wire rope slings with a length of 8 metres and a rated capacity of 262 tonnes each. The slings were rigged in pairs to shackles with a load limit of 250 tonnes. “This meant that our CC cranes were perfectly prepared to lift the gantry crane, which enabled the technicians to disassemble it piece by piece from the bottom up with the help of demolition-type cutting torches,” Zunino explained. “Once a chunk was removed from the gantry crane on both the left and right sides, the two cranes could then set the remaining gantry crane down on the ground.”

During the lift, the maximum load handled by the CC 6800 was 730 tonnes at a radius of 16 metres, while the CC 3800 1 handled a maximum of 320 tonnes at a radius of 18 metres.

Thanks to the project’s detailed planning, it was finished as planned and on schedule by Vernazza’s 12-person team. The team comprised one crane operator and signalperson per main crane, a job manager, a technical manager, and six operators for the assist cranes. In total, the job lasted around six weeks – two for setting up the cranes, two for carrying out the work, and another two for tearing down the cranes.

The CC 3800 1 was located in a dry dock below the height of the CC 6800