Modifications by DBB and Liebherr to duty cycle cranes helped increase productivity by 20 per cent.

Dutco Balfour Beatty (DBB) is well ahead of schedule on its piling contract at an Expo Village project in Dubai, UAE, thanks to a modification on the cranes employed.

The modification was engineered by DBB and Liebherr Middle East to the new HS 8100 HD Liebherr duty cycle crawler cranes being used, resulting in a 20 per cent increase in productivity on the piling operations.

Two new 50-tonne Liebherr HS 8050 HD cranes are being used to install steel cages and a 100-tonne HS 8100 HD crane is using its engine power to drive the vibro hammer that installs pile casing. A fourth Liebherr unit, an LR 1130 crawler crane with a maximum load capacity of 137 tonnes, is also being used on the site.

DBB has six months to complete the piling and foundations work for its contract.

“We are well ahead of our schedule, and are set to complete the piling within four-and-a-half months instead of six as per the programme,” says Tamer Shalash, DBB’s piling and ground engineering manager.

“This is substantially due to a modification designed by ourselves and Liebherr, in which rather than installing a separate power pack on the crane to drive the vibro hammer, we are using the power of the crane engine. In this way, instead of using two engines to run the vibro hammer set-up – vibro hammer and crane - we have only one, and this is controlled by the crane operator,” says Ibrahim Hamdy, DBB’s plant and transport manager. 

“We, therefore, do not have the frame and power pack that is normally mounted on the crane, and so we save on weight and manoeuvrability. We don’t need a separate operator for the power pack, so we save on manpower costs, and we save time because we eliminate the lost time required for communication between crane operator and vibro hammer operator,” he adds.

By this application, money is saved on the purchase or rental of the power pack as well as on diesel and other running costs.

“Overall, we have calculated that in time, money and efficiency, we have improved productivity by 20 per cent if compared to the conventional two separate equipment of vibro hammer and crane set-up. 

“This is the first time this modification has been used in the UAE, and we shall be using this on the next project where we deploy the Liebherr duty cycle crawler cranes,” says Hamdy.

Rotary drills supplied by another manufacturer are being used to bore the holes, with the Liebherr units driving the casing and then placing the steel rebar cage, in one length, into the hole.

The contract requires 1,900 piles, ranging in depth between 15 and 26 m, and with diameters of 1,000 mm, 900 mm and 750 mm. The soil is sand for the first 4 m, with mixed rock of varying hardness below that, and a water table nearly 7 m below the surface.

“We are working to a 24-hour cycle, and our highest rate of pile installation has been 43 piles during one cycle,” says Shalash. “Using this configuration, we are saving up to six minutes per pile. We are actually calculating that during one cycle we can save two or three hours. This is a real achievement, and we are very happy to have worked with Liebherr to arrange such a satisfactory performance,” he concludes.