Possibly the most interesting thing about the six Italian Heila cranes going onto the UK''s new polar research ship is that two of them are not just LR Offshore certified like the others, but will be explosion proof as well - despite heading into the Antarctic.
These two 3t and 5t capacity 'science cranes' will be capable of off-board lifting and putting the vessel’s fleet of small observation ROVs into the water in a sea state of 5.0. The hidden issue is that the deck area they will be inhabiting is just over the laboratories – if the labs create any kind of potentially volatile gas mixture, this will be pulled up the extraction flue and out as quickly as possible and the exit is right underneath these cranes. “It’s a long shot, but if it happens anything that could create a spark could be a danger,” explained Stuart Gilligan of distributor Offshore Marine. Therefore, this pair of dedicated cranes have been ATEX certified to Zone 2.
Along with the five auxiliary cranes, the research ship is also going to have a triple-fall main cargo crane with a capacity of 50 tonnes at 19.8m reach, and 20 tonnes at 35 m extension. There has been a special care taken over the redundancy as the vessel will be facing long Antarctic operations, Vincent Schouten of Heila told MJ. Because it’s a DP2 vessel there will be a link from each switchboard so “a failure in the power feeds won’t affect the crane’s load capacity or operating speed” he explained. There are further layers of redundancy as the power pack for the main crane is built out of a pair of electric 270kW motors, each with a cross-connected pump set. This gives a total 540kW, but most importantly “if one electric motor and-or-pump set fails, the crane can still be operated from the other” as the system will still generate 270kW; sufficient to carry a full load at half speed.
Further, the cranes have been built to last a quarter of a decade with long maintenance schedules: “Although the vessel is to be based in the Falklands, there are some issues with local supply,” added Stuart Gilligan.
Obviously the extreme cold presents a large challenge, so the cranes have been subject to a winterization process enabling them to be used in ambient temperatures of -35°C. High grade steels have been necessary to avoid brittle fractures, and heated oil baths and heaters have been used to keep a trickle of warmth circulating around the drives, preventing water condensation getting into the motors.
The design also had to concern itself with operability issues, explained Mr Schouten: “We have had to make sure there are no tight levers that can’t be manipulated if you are wearing gloves, likewise nothing that can trap the ice.”
The two ATEX certified cranes weren’t the only potential ‘explosion’ that had to be averted. As most people know, despite the online public vote the ship is being named RRS Sir David Attenborough. However, it’s been decided to call one of the research vessel’s subsea ROVs by the catchy alternative: therefore, the Heila cranes will still be rubbing shoulders with ‘Boaty McBoatface’.
By Stevie Knight
