Leading tower crane manufacturers are preparing technical guidance to issue to their customers in France who may be concerned about the long term structural stability of their cranes after the gales and storms of late December.

Winds of 200km/h hammered much of France for two days, knocking out power supplies to 3m homes and closing roads, railways and ports. Around 100 people lost their lives in the storms.

Among the damage was the collapse of up to 20 tower cranes. All are believed to be Potain cranes; only about 10% of the 2,500 tower cranes in France are not Potain cranes, it is reckoned.

Most of the cranes that fell were in the Paris region, in the southwest or in the east, where the storms were strongest. Most were also older cranes.

Concerned French authorities called a meeting in Paris last month which was attended by representatives of standards and safety organisations, major contractors, and tower crane manufacturers Potain, Liebherr and Terex Peiner.

The primary concern of the authorities was whether the cranes left standing had suffered latent damage, not readily detectable. They also questioned the appropriateness of the current European standard setting a 150km/h wind speed threshold for free-slewing when out of service, and suggested it should be raised. This was oppo-sed by the manufacturers, on the grounds that a limit has to be set somewhere and 150km/h was reasonable. Any higher, and cranes would have to become heavier.