Crane safety alert on the effects of wind
By Alex Dahm20 July 2010
A safety alert on the influence of wind forces during crane operations has been issued jointly by FEM and ESTA.
It is aimed at owners and end users in the crane industry, especially those in the wind turbine business. It was prompted by some serious crane accidents during the erection of wind turbines, where wind load appears to have been a major contributing factor.
Instrumental in producing the alert were the FEM (European Federation of Materials Handling) product group Cranes and Lifting Equipment, Mobile Cranes and the European Association of Heavy Haulage Transport and Mobile Cranes (ESTA) crane group.
Wind turbines have increased in power output and height to the point where now a 100 metre tower is common and larger cranes are needed. When lifting loads with a relatively small mass but large sail area, for example, rotor blades, the wind load can have a considerable impact on the lifting capability of a crane.
The recent accidents demonstrate the importance for crane owners to request information and to take into account wind forces, wind gusts and the sail area of the load.
An abridged version of the safety alert is reproduced below.
Mobile Cranes - Influence of Wind Forces during Crane Operation.
Influences of wind forces during crane operation, as described in detail in the load charts and operation manuals of the manufacturers of mobile cranes, must be observed to prevent accidents.
The wind load has a considerable impact on the load carrying performance of the crane. The effective sail area of the load which needs to be taken into account is the result of the projected area multiplied with the cw factor (shape coefficient for the load). The sail area and cw factor must be known to all parties planning the lifting operation.
In addition, it is mandatory to request information regarding the expected wind forces, including any gusts for the relevant environment from the responsible meteorological office prior to performing a lift and to take this information into account.
The performance of a lift without knowledge of the expected wind forces and the actual sail area of the load can lead to a failure of components and/or turning over of the crane.
In cases of negligence there is a risk to life.