A telescopic crawler crane overturned on a site alongside the M4 motorway, near Slough yesterday.
The crane, a 45 tonne Marchetti Orsa CW45.32 was working on the bridge widening project at Junction seven - Slough West.
Initial reports indicate that the prepared raised platform, had suffered from the recent heavy rains apparently washing out much of the Type 1 material, causing the platform to soften, and eventually give way or sink in places.
The crane had tracked to its position at the top of the ramp with the undercarriage retracted to its 2.98 metre narrow position, the boom over the front and slew lock engaged. It stopped at a position indicated by the banksman, who had been lining the crane up as it climbed the track. However at that point the bank began to give way and the edge of the raised platform crumble, causing the crane to tilt over to the side, the operator decided to release the slew lock and attempt to slew the counterweight over the track opposite to the edge to provide some counterbalance and hopefully stop the bank from collapsing. However by then the crane was at a side angle too great for the slew motor drive to overcome, and the crane continued to gradually sink sideways. At that point the operator jumped clear of his machine. Shortly there after the crane reached an angle at which gravity took control and the counterweight swung towards the bank loading the track on that side even further, thus accelerating the overturn.
Thankfully the operator, an AGD employee, was unhurt and no one else was involved in the incident. It also looks as though the crane was not too badly damaged.
For information the CW45 has a 360 degree chart with tracks in the retracted position and full counterweight installed and although this might look like the fourth telescopic crawler crane to overturn rearwards in the UK this year, the site investigation detailed above clearly indicates that it is a totally different cause in this case, and emphasises the importance of a well constructed platform, and the need for it to be carefully monitored after heavy rains etc...