E-Mobility Engineering | September/October 2023 45 Dieseko Woltman pile-driller/driver | Digest system is divided into two, Legtenberg explains. The main, 1000 kWh pack in its container must be detached to allow the vehicle to fit on a low loader for transport. This is accomplished using a separate crane, as the pack weighs about 15 t. Fortunately, the battery pack has next to no effect on the rig’s balance, as the diesel 90DR normally carries 15 t of ballast, which the battery replaces in the electrified version. “We got that one for free,” Legtenberg says. With the main pack removed, the rig must still be capable of driving on and off the truck under its own power, so there is a smaller, 200 kWh pack that remains on the machine deck to power the tracks and raise the leader. Energy and power The total battery capacity is therefore 1200 kWh and the maximum power output is 613 kW, which is enough for a typical working day and is more than the diesel rig on which the new machine is based. The maximum torque the hydraulic drilling motor applies to the leader is 500 kNm, and the maximum pull-up force that can be generated by the winches is 80-100 t. To determine how much battery capacity the 90DRe would need, Dieseko’s engineers analysed the performance and energy use of several comparable diesel machines during a typical working day with an energy reserve, which got them to the figure of 1200 kWh. Plotting that on a graph shows multiple power spikes through the day, each peaking at around 400 kW and representing the installation of one pile. This rig’s 613 kW provides it with a confidence-boosting margin. The main engineering challenges Dieseko faced in developing the electrified rig were centred on knowing the domains of electric powertrains, electronic controls, time, space and systems integration. “We are a mechanical company with a lot of hydraulic knowledge but limited electrical knowledge,” Legtenberg says. “So we had to find expert partners – that was very important.” Dieseko therefore chose Webasto to provide the complete battery system, including its thermal management and power distribution subsystems, and Danfoss to supply the electric motors and power electronics. IFM supplied the overall control system for the rig, while for electronic management of the valves in the hydraulic system as well as the operator’s controls in the cabin and system integration, it turned to VSE Industrial Automation, a specialist in electrical control systems for heavy machines. Materials issues The machine is made largely from steel, with the most widely used grade being S355, a structural steel with a minimum yield strength of 355 MPa. For the most highly stressed components, such as the leader, S690 high-tensile steel is used, which combines high strength with relatively low weight. Legtenberg explains that the stresses on the leader are so high because it has be tall in order to install long piles, and while it usually works vertically, it also has to be able to tilt to install the angled piles used to anchor bridges, for example, multiplying the stresses. “When it’s working at an angle, the forces on the leader are immense,” he says. “And of course the rotational bearing becomes heavily loaded.” The next major piece of structure is the machine deck, which houses the hydraulics and electronics along with the operator’s cabin. The deck rotates by means of a bearing on the chassis, called the undercarriage, to which caterpillar tracks are attached. Among the hydraulically operated machines on the deck is a set of three winches, one that pulls downwards to assist installation, and two others that pull upwards – one to raise the tooling, the other to extract piles or casings. The machine deck is also home to two pumps that feed pressurised oil to the hydraulic loads, the oil tank that serves as the hydraulic reservoir, and a dedicated hydraulic oil cooler. All the pile installation and extraction tooling, as well as the automotive components on the 90DRe, remain hydraulic, as most customers have large investments in hydraulic tooling. However, the hydraulic pumps are driven by two permanent magnet (PM) electric motors from Danfoss. Supplied by Webasto, the battery High-torque hydraulic pile drill depicted at an angle off the vertical, a position that can be used for inserting piles to anchor bridges, for example. Electric tools are under development
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