Last year was the worst ever for accidents in the wind turbine erection and maintenance business, prompting a major safety conference last month. Alex Dahm reports
The ESTA Expert Summit Safety Issues in Wind Turbine Installation and Transportation in Hamburg, Germany, saw a strong attendance of around 200 stakeholders, including senior people from crane and transport companies and wind turbine manufacturers. Most were from Europe but, such was the interest in and concern over safety, there were attendees from as far afield as Brazil and New Zealand.
New wind energy capacity is being added at the rate of 40 GW a year, said Per Krogsgaard at BTM Consult, in his forecast for the industry presentation. Turbine towers are increasingly up around 150 metres tall, requiring larger cranes with much stronger booms. Power generation capacity is increasing towards 9 or 10 MW per turbine, with a corresponding increase in size and weight of components. Accidents occur in transferring, transporting, installing and repairing wind turbines.
Commercial pressure in the form of time and cost constraints was widely discussed at the conference as a primary factor contributing to accidents in the erection and maintenance of wind turbines. On the subject of time, a significant point was that where wind farms are designed to have an operating life of decades, is it so much to ask that, during erection, the crane operator waits a day until the wind speed is low enough to safely make the lift.
Another major issue highlighted for turbine installation was the extra wind loading due to the sail area of the turbine components, especially the blades, to be calculated and factored in to a lift plan. Crane manufacturers have assumed 1 square metre per tonne for calculating their load charts but the reality can be five to eight times that, said Søren Jansen, ESTA general secretary. Instead of an average wind speed at 10 metres elevation, the measurement should consider 3 second gusts at the boom head, which is often 100 metres or more up in the air.
A common mistake often assumed by operators is that when a crane is lifting at less than full capacity, if there is higher wind then it will be okay, but this is not true, said Hans-Dieter Willim, Liebherr design engineer. A lack of knowledge about the forces caused by wind on loads with a large sail area (surface area presented to the wind) leads to many of the accidents.
It was suggested that it might be prudent to ban the one-piece lifting of complete, fully assembled, turbine rotors with all three blades attached. Single blade installation reduces the impact of wind load but on some turbines it is not possible to rotate them with one or more blades missing.
Moving on site
For installation and maintenance, relocation of equipment is where many of the problems occur. To save time there is pressure to move cranes with insufficient de-rigging. Ground conditions and poor quality narrow site roads with weak shoulders were cited in several accidents. Access roads used to be 5 m wide but now are often only 4 m, Jansen says. Discussions at the summit included provision of shallower gradient and wider access roads, larger pads for crane set up and the supply of temporary roadways and matting.
Turbine manufacturer Siemens Wind Power has a Zero Harm initiative in a bid for no accidents, no injuries and no lost time incidents. Crucial to this is for everyone involved in the wind turbine project to take responsibility, explained Paul Eijro Okpurughre, head of EHS in global project management organisation at Siemens. Okpurughre said that the accident frequency rate at Siemens was reduced by 60% from 2009 to 2011.
Aside from the human cost, accidents on wind turbine projects cost a lot of money, often running to millions of dollars for the turbine component damage plus the crane repair. Finn Thyrring, a mechanical engineer at Codan Insurance, illustrated this with examples of accidents. A typical one shown involved a large wheeled mobile telescopic crane that turned over on site, which cost Euro 880,000 to repair and three or four months in downtime.
Looking ahead, another challenge that will come up more and more is the need to dismantle wind turbines at the end of their lives, said Sander Splinter, Mammoet Europe managing director. Special techniques and methods will need to be developed. One issue is the sudden loading of the winch at height when the hook has gone up with no load on it. As the weight of the load of a component for dismantling is transferred to the hook there is a tendency for the rope, on the outer layer, to pull down through the layers and lock up the drum.
As a forum for lifting and transport equipment end users and manufacturers, turbine manufacturers and other stakeholders in the wind energy industry to get together, the ESTA Experts Summit event was a great starting point for future discussion and closer co-operation to help improve safety and reduce the number of accidents in the busy and growing sector worldwide. More dialogue and greater co-operation is vital to help reduce accidents.
Momentum needs to be maintained and gained to be able to take things forward. A worthwhile aim would be to develop a best practice guide for all operations involving lifting, handling and transporting wind turbine components, which can be adopted and followed worldwide. It will require input from all stakeholders.