Sonntag Baugesellschaft is the first Liebherr customer to use the A 920 Litronic wheeled excavator with a personnel cage. This special solution enables people to be transported up and down construction trenches in a cage as long as safety precautions are in place. Sonntag Baugesellschaft primarily uses the equipment in sewer and tunnel construction, for example for pipe jacking work in Frankfurt am Main.

Sonntag Baugesellschaft is a medium-sized business currently managed by the 4th generation with sites in Dörth and Bingen-Kempten (Rhineland-Palatinate). Around 500 employees tackle a large number of projects in Germany and Europe. The range of services includes civil engineering, classic sewer construction, deep foundation and pipe jacking work.

Liebherr mobile and crawler excavators have been used by the company for decades - including several A 920 Litronic excavators fitted with personnel cages. This equipment was specially developed by Liebherr at the request of Sonntag Baugesellschaft. People can be transported safely up and down construction trenches using this purpose built equipment. Personnel cage operation is therefore ideal for sewer and tunnel construction, particularly for pipe jacking work particularly well sinking and backfilling initial and target shafts.

"Pipe jacking work usually takes place in inner-city areas, where space is often very limited. Instead of having to provide an extra machine for transporting people, our mobile excavator can now perform this task" explains Robert Himmel, Managing Director of Sonntag Baugesellschaft, at a construction site in Frankfurt am Main. The personnel cage, which the company itself supplied, has a locking access door, holding facilities and a belt system in its interior.

In case of an emergency a rescue cage can be attached to the load eye of the excavator stick with an eight tonne capacity. In addition to the stair towers and ladders that are still obligatory on construction sites, the A 920 Litronic can also be used to rescue casualties in an emergency.

Safety is the primary concern when transporting people using construction machines. Specific requirements must be observed with regard to the machine’s equipment, personnel cage and action on the construction site. For example, Liebherr has developed the "preparation for personnel basket operation" equipment to ensure that the A 920 Litronic can be used for these purposes.

A special key switch, which reduces the working speed to 0.5 m/s when lifting, lowering and turning the boom, stick and slewing gear, is a vital part of the safety element of the cage. In addition, the equipment includes an overload warning device and pipe rupture safety valves on all hydraulic cylinders of the working attachments as well as the machine outriggers. There is also a camera on the stick of the A 920 Litronic and the driver's cab is equipped with a second display to provide a perfect view of the personnel cage. Working headlights provide perfect illumination.

Stable, level ground

No attachments may be mounted whilst the cage is operating and another trained person with a view of the basket plus the machine operator must be present during the work. In order to ensure the stability of the wheeled excavator, it must be placed on stable, level ground and supported with a blade or outriggers during operation.