Lifting operations are evolving. Cranes are getting larger and increasing use is being made of fibre rope, but there is still room for technology to make lifts safer, more efficient and less energy intensive
In the last few years it has been tempting to see the development of cranes and load handling systems for offshore vessels purely in terms of the development of larger and larger units capable of lifting heavier and heavier loads.
However, offshore lifting isn’t just a question of the capacity of a crane. A lot also depends on when and if a vessel and crane can undertake a lift, and how the process might be optimised and, above all, carried out as safely as possible.
That is certainly the message that Richard Myhre, managing director at AXTech in Norway has for the industry. To undertake a lift, first and foremost, he said, you need a stable platform from which to undertake it.
AXTech recently acquired a start-up company, MRPC, which has developed patented technology that forms the basis of an accurate, fast-acting anti-heeling system which is particularly relevant for heavy-lifting at sea.
“This kind of technology is relevant to AXTech as a designer and manufacturer of lifting systems and to the industry as a whole,” said Mr Myhre. “It optimises the operation of a vessel and the crane installed on it. The system can actively reduce vessel motions by 50-70%. This means that the requirements made on a crane’s heave-compensation system can be reduced, as can the amount of power needed by the heave-compensation system.
“We have made detailed studies of the technology MRPC has developed and believe that it has a number of potential applications in the offshore oil and gas and offshore wind industries,” he told OSJ, noting that the same technology is also suitable for use elsewhere in the marine industry – its first application was on a large trawler for Aker Biomarine.
Mr Myhre also believes that much greater use could be made of big data in the offshore lifting segment. “For a long time, we have installed advanced monitoring systems on module handling systems on subsea construction vessels,” he explained. “This makes it possible to use data logging and analytical tools to provide operational support and support maintenance strategies for lifting equipment.
“The next logical step would be to harvest far more vessel data and provide vessel owners with a much more comprehensive understanding of operational performance than they currently have,” he explained.
“By combining an analysis of the data from lifting equipment and the vessel on which it is installed and transmitting it ashore, a land-based support centre can become a hub for decision-making at sea.”
Mr Myhre explained that, for some time, AXTech has been working on the implementation of ‘help-desks’ for offshore operations in which remote support can be used to provide support for operations. “Data would be measured offshore but analysed onshore to help optimise operations,” he explained.
“Data we have collected shows us quite clearly that often vessels are undertaking lifts when their stability is less than optimum, or that they are choosing to delay lifts when they might very well be undertaken if only they had access to sufficient data,” Mr Myhre told OSJ.
“If you are constantly gathering data about a vessel’s stability, the sea state and so on, and analysing it, you can provide the ship with a very accurate decision-making system about when, or when not, to undertake a lift, or how that lift can be optimised.”
Apart from getting larger and undertaking heavier lifts, the other major change in offshore cranes in the last few years has been the widespread adoption of fibre rope in place of steel wire.
As OSJ has highlighted on several occasions, most major crane manufacturers now offer fibre rope crane or hybrid cranes that combine the use of steel wire and fibre rope, but fibre rope is not without its challenges. One challenge is that fibre rope can overheat when used on a heave-compensated crane. Active heave-compensation can introduce a lot of heat into fibre rope, which can degrade its performance.
Huisman’s solution to this was to develop a hybrid fibre rope system which combines the advantages of fibre rope with heave-compensation on steel wire rope.
As Huisman’s product manager for cranes, Cees van Veluw, explained, the company strongly believes in the future of fibre rope cranes but felt that without what he described as “some serious active cooling of the rope” when in active heave-compensation (AHC) mode there was a question mark about how widespread their use might be. “The thermal behaviour of fibre ropes in AHC mode has proved to be unreliable, hard to measure and hard to predict,” he explained. Huisman’s solution sees spooling of the fibre rope undertaken on a traction winch, with active heave compensation on a winch handling steel wire.
Another trend Mr van Veluw highlighted is how much power a crane uses, and the growing use of electric cranes. Electrically-driven cranes are environmentally friendly because they don’t require the use of potentially polluting hydraulics, but their advantages are more numerous than that.
“With an electric crane, when it’s in standby mode, you’re not using lots of power the way you are with a hydraulically-operated crane,” said Mr van Veluw. “You don’t need to provide power to all the motors and pumps that you have in a hydraulic system. With an electric crane you also get enhanced heave-compensation and you can make use of super-capacitors to store energy.
“With an electrically-driven crane you can also make use of peak-shaving during heave compensation and you can reduce the demands that are made on the vessels’ power grid. That can help to reduce emissions too.
“How often have you seen a vessel start producing black smoke when a lift is underway? That’s because of the power demand that the lift is putting on the ship’s grid and on the engines on board. You don’t get that with electric.”
World's largest leg-encircling crane installed
In February 2018 a 1,600-tonne leg-encircling crane designed and built by Huisman in the Netherlands was installed on Van Oord’s turbine installation vessel Aeolus. The new crane, said to be the largest of its type ever built, will enable Van Oord to install larger and heavier foundations and turbines for offshore windfarms. Such is the size of the new crane that it was installed by a heavy-lift vessel, Heerema’s Thialf.
The leg-encircling crane was specifically designed to be used on a jack-up vessel and is built around one leg of the jack-up. If required, the boom for the crane can be stored around another leg, saving valuable deck space. The crane also has a small tail swing, freeing -up deck space.
Cargotec strengthens MacGregor with TTS deal
MacGregor, part of Cargotec, has entered into an agreement to acquire several businesses from TTS Group, the well-known provider of cargo handling equipment and services for deepsea and offshore ships. The company said the combination of two “highly complementary businesses” would provide greater scale and diversification and will strengthen MacGregor’s portfolio and market position in key markets, not least its marine and offshore activity.
The acquisition is subject to regulatory approvals from the competition authorities, which are expected in the third quarter of 2018.