HIGH PROFILE
The maintenance free IP 68-rated plug anddrive power modules ensure reliable operation in all-weather situations
meaning the truck over time can be operated more efficiently and with more freedom. Look at a mechanical truck. Normally the efficiency sweet spot based on a particular GVW is in second gear on a 10 % ramp with 2 % rolling resistance, so this is how you look to design the mine roads. Once you start to alter the GVW, ramp angle, and rolling resistance you start to move out of that sweet spot. So mines with 100 t truck fleets that have restricted themselves to 10 % ramps will now have more flexibility. Haul roads can be better adapted to the geology and topography, such as looking at a 12 % ramp where they have dry conditions. The T 236 can handle this, whereas a mechanical drive truck would have to shift back into first gear, meaning lower efficiency and speed in comparison. Our truck gives the mining guys the opportunity to design the pit more to its optimum layout not just to accommodate the truck. Even if a 5 % or 3 % ramp is preferred for whatever reason, on a mechanical drive truck, you are moving up into 4th and 5th gear where the transmission has several clutches and gear engaged. Our truck doesn’ t care and has even an increasing powertrain efficiency at those higher speeds. A big benefit of course will be in a mine that has a high fuel burn. At a 75 litre per hour 100 t mining truck operation, with 2 % higher efficiency it means a big difference. In larger quarries, while the fuel saving may not be as marked, where you are having to feed your crusher with granite around the clock and the weather deteriorates, the road gets softer and they may not have a grader. Here the advantage is that we do not generate any more shift bumps in the haul road as we are not shifting any gears. This also reduces the material spillage while driving.
Q: What about other 100 t electric trucks compared to yours? Are there other differences between the T 236 and larger electric drive models from a design standpoint?
BR: The other electric trucks in the 100 t class are a downscaled version of the bigger trucks including the gridbox, which dissipates energy during retarding. Gridboxes don’ t handle wet air well, and may suffer in wet conditions from short circuits. There is a perception in some markets that electric trucks are the first to go out of production and the last to come back in poor weather; and in some cases the gridbox is to blame for this reputation, as well as the issue already discussed where the truck relies on the rear axle retarding that can cause slipping problems in wet weather. This is why we took away the gridbox and applied the 4 corner wet braking. Independent drive control per side such as on the T 236 is already used on larger electric trucks. So, from a drive point of view, when you propel they are operating in the same way. But the larger diesel-electrical trucks do not push the engine during retarding, to lower fuel consumption during downhill operation. Our truck has Active Front End technology, making efficient use of electrical energy during retarding events, so that the drive system is able to deliver controlled engine speed with almost no fuel consumption. It means the alternator is used as a motor to propel the engine. The active front end function allows the engine friction to be used for retarding and provides power to the auxiliary drives, reducing fuel consumption and ensuring the engine never over speeds.
Q: And can you explain the safety upside of the power modules?
BR: Safety is also an advantage with the smaller electric drive truck. Larger trucks run on a higher voltage level, so we said from the outset, we want to stay at below the 1,000 Volt level, in our case 690 VAC and 900 VDC, so we come under the lower voltage regulations without the high isolation requirements during service. In the electrical compartment, integrated Liebherr Litronic Plus Isolation system allows conventionally trained electricians, not specialists, to work on the truck, another big plus for smaller mine operators and mines in remote regions. Secondly, if you look at the hybrid car industry, a conventional mechanic needs extra training and certification to work on them. We developed a short circuiting and isolation device on our three electric power modules, which each have a lever, which allows you to short circuit the DC link so there is no current, then the whole thing is grounded / earthed to the chassis. So by design there cannot be any more residual voltage giving a safety risk, ie positive isolation. Only then can the mechanic access the ports of the power cables to remove them from the boxes. With our isolation system we are preparing the ground so that in the future trained multi-discipline technicians will have the opportunity to change the electrical cabinets on the machine in a“ Plug & Drive” principle.
And all auxiliary systems are hydraulically driven. An additional benefit on the machine is the positive drive isolation, which allows work to be done on the machine while the engine is running. There are other safety features in the truck’ s cab, such as dual-side access and incorporation of ROPS comparable to a 150 t class truck, which were engineered during the initial design process; while a recessed, full-size passenger seat allows for increased visibility for the operator to the off driver side of the machine.
Q Why build it in Colmar with the rest of the trucks being built in Newport News?
JL: It is for several reasons. We have capacity in Colmar to do it; as in Newport News they are very busy with the 363 t T 284 and 221 t T 264 production. And we are also working on a new capacity truck there to fill the gap between these two size classes. As a company we also realise we don’ t just want to have mining excavator expertise on one side of the Atlantic and mining truck expertise on the other. We are a global mining equipment supplier so want to be multifunctional at our mining equipment facilities globally as we grow our product ranges. For now it means adding the T 236 to the production at Colmar. It is good for us to have both skill sets at both sites.
Q Finally where do you see the market entry for the T 236? It isn’ t going to be the lowest initial cost option with its level of technology?
JL: Liebherr do not sell our products on price, we sell on competitive advantage. That argument has
22 International Mining | JANUARY 2018