David Foxwell reflects on the need to remain vigilant about safety during offshore lifting operations
Last week a monopile foundation slipped out of its sling while it was being loaded onto a heavy lift vessel at Port of Rostock. The foundation was being lifted on to the ship, SAL Heavy Lift’s vessel Svenja, when the incident occurred on 31 October, causing damage to the ship and the quayside where the work was being undertaken.
In August, personnel on Swire Blue Ocean’s installation vessel Pacific Osprey were injured in a crane-related incident while berthed alongside in Eemshaven, the Netherlands. Both incidents emphasise the potential dangers involved in working in offshore wind energy, dangers that are all the more obvious when work is being carried out at sea.
Reducing the amount of lifting work carried out offshore has long been a goal in the industry. If more lifting and assembly work can be carried out ashore, and less offshore – these recent incidents aside – the argument goes, so work will be safer, can be undertaken more quickly and costs will fall.
However much work is carried out ashore, offshore lifting is always going to be required, so I was interested to read about work carried out at the Offshore Energy Engineering Centre at Cranfield University, the Department of Engineering Science, University of Oxford, University of Strathclyde and Fraunhofer Institute for Wind Energy Systems investigating the concept of ‘human-free’ offshore lifting solutions.*
As researchers at the institutions pointed out, lifting operations in the offshore wind energy industry involve heavy loads of hundreds of tonnes, as well as working heights of around 100 m, all while the lifting operation is being subjected to the wind and wave conditions at sea. This makes offshore lifting operations and offshore wind turbine installation hazardous.
Guidelines and standards for health and safety in lifting operations in general, as well as specific to the offshore environment, exist, they pointed out. But despite this, having people directly under the load for guiding and securing is still common practice when offshore turbines are being installed. Dropped objects are an ever-present risk and, it is said, a neglected hazard in the industry.
While data from the G+ offshore safety group suggeststhe number of incidents per number of hours worked decreased slightly from 2014 to 2015, it rose again in 2016. Over the same period, normalised incidents due to dropped objects increased year-on-year. Although small, these increases are important, especially as the installed capacity of offshore wind energy and the number of lifting operations carried out each year are expected to grow significantly.
The motivation for the study was to conduct research into methods and technologies that could reduce the need for personnel near lifting operations, and to assess their feasibility. Different concepts for human-free offshore lifting operations in the categories of assembly and logistics, connections and seafastening, as well as guidance and control, were collated and investigated, mainly based on broad literature reviews and industry reports on current practices, but also based on patents for new designs and innovative solutions proposed by the authors.
Space precludes a detailed description of the concepts and technology examined, but the study found that guidance and control systems, automated bolting or hydraulic seafastening, as well as a tool for optimised planning of offshore wind turbine logistics and installation, could help to remove people from beneath loads and thus contribute to increased safety in lifting operations.
In particular a program for installation logistics demonstrated potential advantages and possible sensitivities of different installation procedures, and a novel, although preliminary, concept for seafastening was suggested.
Supplementing existing tools, such as the Boom Lock and taglines, by a holistic solution for visual and mechanical guidance, consisting of three circumferential cameras and one 360° camera, as well as innovative reusable guiding elements, could lead to faster and highly accurate offshore lifting procedures without putting personnel in dangerous areas. This would not only speed up the lifting operation itself but is also expected to entail financial benefits in offshore windfarm installation.
“Regardless of the additional economic benefit, cameras and mechanical guiding elements are easy to implement and would reduce the number of incidents during installation work by removing people from the high-risk areas. Increased safety and protection of life should be of highest priority,” the authors of a paper about the project concluded.
* The Dogger Bank meteorological mast is an interesting example of 'human-free' installation and was the first in the UK to use a ‘human-free’ technique to place the lattice tower of the mast on top of the foundation. Lightweight plastic cones, tag lines and strategically placed slings were fixed to the tower sections prior to any lifting activity, alleviating the need for riggers to physically be in position to manoeuvre the towers into place. This was both safer than conventional methods as it enabled the crew to stay on deck away from the lifting hazards and suspended loads, and also much faster as the cones helped to quickly stabilise the load in the final stage of the lifting.
Priot to this, industry standard practice required riggers to physically be on the platform or lower tower section to manually help with the final positioning of the lattice sections once they had been lifted off the vessel and were ready to be fixed in place. In this process, riggers were exposed to the hazard of suspended loads and the risk of being crushed by the lattice tower sections. This was a particular concern when landing the upper tower section onto the lower section, as the riggers tended to be very constrained in their position at the top of the lower section.