Passing safely through the bottleneck

K+S KALI GmbH uses two Jungheinrich diesel forklifts for above-ground transport operations at Shaft 2, the plant’s “bottleneck”. The swivel seats on these DFG 670 forklifts are what make them so safe to operate. Seated at a 90-degree angle to the direction of travel, drivers have everything in full view — an advantage no one driving in or out of the shaft’s steel cage can afford to dispense with.

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Benjamin Gross, whose responsibilities as plant mining machinery engineer at K+S KALI GmbH’s Zielitz potash plant include procuring the vehicles for the mine, steps over to a wall map. He points to the drawing of the extensive mine and then to a shaft symbol. “We use Shaft 2, which penetrates 750 metres down into the mine, for moving everything we need down there, from materials to workers. And vice versa. That is why the cage is in operation around the clock.” The material is partly transported in closed containers and pallets on two wheels so that one of the Jungheinrich diesel forklifts can tow them on to the cage floor.

The perfect twist

The two DFG 670s are outfitted with Jungheinrich’s optional swivel seat, allowing swing movements of up to 180 degrees to the left. A function that is critical in terms of work safety, especially when a load blocks the view to the front and the driver has no choice but to drive backwards. Moreover, 180-degree swivel seats provide many clear ergonomic benefits that translate into more effective and faster payload handling. However, at this site the driver uses only a 90-degree angle to the direction of travel, because from this position he has the best overview while driving into the cage in Shaft 2. Benjamin Gross asks the driver of the forklift in charge of transport operations at the shaft to demonstrate the swivel function. The driver presses a button and his seat swivels 90 degrees. “In the right-angle position the driver operating in the cage has a clear view and can avoid bumping into anything, either with the truck, the container or the pallet. This is very important, as a crash could seriously hamper operations in Shaft 2.”

That would be a catastrophe, as Shaft 2 is the central artery for the entire mine. The mine extends about six kilometres to the north and south and some 21 kilometres from east to west. The mined potash reserves lie at a depth between 400 and 1,100 metres. The continuous supply line to and from the mine is never to be interrupted, even if the truck inside the cage develops a problem. That is why the potash mine operator had the DFG 670s from Jungheinrich fitted with an easy recovery function, which allows for the quick release of the handbrake from outside the truck and the immediate removal of the truck from the cage.

Benjamin Gross walks to the back of the shaft building, where the diesel truck, which has towed a container into the cage, is being driven out. “On this side the truck also tows the carriers returning from the mine below from the cage.” Although fitted with splash proof electronic drive and hydraulic controllers (in accordance with IP 64) connected via a CAN bus, the truck itself always stays above ground to protect it against contact with the salt dust below. “If these trucks were to move in and out of the mine, the constant alteration would lead to major corrosion of critical truck components. The containers and pallets on the other hand are always in circulation, i.e. they are always being moved in and out of the mine proper.”

Seven tonne trucks pull ten tonne containers

“The jobs our trucks perform at the Zielitz potash plant demonstrate that Jungheinrich forklifts can handle special tasks,” explains Daniel Rösch, product manager for the VFG series trucks at Jungheinrich. “Before the trucks were given the operational go-ahead, our specialty construction and development experts checked the suitability of the trucks for the mission. This measure guarantees the long-term service life of the DFG 670s at the plant.”

The trucks move the containers and pallets using application-specific attachments. The truck operator shows how they are used in practice by finessing the forks into the matching slots on the attachment and then locking them in place. “Although the containers and pallets have a rated maximum weight of ten tonnes, the 7,000 kilogramme payload capacity of the DFG 670 is sufficient to move them,” comments Benjamin Gross, “because the weight is distributed over the truck and the container or pallet axle and wheels.” The plant also uses platform trailers for transporting large components that are not suitable for oblique loading.

Apart from the material needed in the mine, which the incoming goods section loads onto the containers, the mine uses industrial waste for construction or backfill work below ground. A specially built bagging machine fills the waste materials into big bags before being transported and stored.

The gate to the box in the automatic bagging machine rolls upwards and opens up a view of one of the containers loaded with big bags. The DFG 670 that operates here drives up to the box, locks on to the container filled with the bagged waste and tows it to the forecourt of the shaft. “This kind of transport is never directly from the bagging machine to the shaft, because the driver never knows exactly which material needs to be supplied to the mine, when,” explains Gross. “Which is why in this case the seat stays in the normal position. Nevertheless, we had both trucks fitted with swivel seats, so that each truck can replace the other one if the need arises.” The DFG 670 assigned to the bagging machine is also used for parking empty containers in the forecourt of the shaft, and transporting them from here to the bagging machine.

Selectable hydrostatic drive mode

Because the potash plant uses the Jungheinrich diesel forklift with hydrodynamic drive primarily for short routes, Benjamin Gross went for the optional drive comfort package. This allows for an automatic increase in rpm for the hydraulic drive and simulates hydrostatic drive characteristics, showing its strength above all when it comes to reversing. “The drive comfort package is a software solution which can also actively decelerate the truck as soon as the driver takes his foot off the accelerator. Moreover, it prevents creep when idling. Also the driver no longer has to brake when changing the direction of travel.” On the other hand, the plant exploits the soft and smooth approach capacity that comes with the hydrodynamic drive for positioning, in particular for handling special assemblies.

The four-cylinder, electronic injection, turbo-diesel engine in the DFG 670 delivers strong torque even at low rpm. This lowers fuel consumption and keeps noise levels down to just 73 dB(A) in the cabin. As the tough engine was especially designed for forklifts, it provides high reliability and long service life, even under the toughest conditions. To reduce particle emissions, Jungheinrich also offers particulate filter systems. The potash plant uses the optional exchangeable filter cartridges in conjunction with an external burn-out unit, so that full filters can be burnt out when replacing the filter cartridge.

Unobstructed view for greater safety

The truck’s excellent all-round view, thanks to the special roof and console wall design of the cabin, is another way in which Jungheinrich contributes to safe and smooth handling in the cage and the vicinity of the shaft. The unobstructed view, thanks to fitting the fork carriage to FEM/ISO-2328-4A and the extra wide screen, made possible by employing slim line masts and lifting cylinders hidden behind the masts, add to the operational safety. The DFG 670’s easily operated hydrostatic steering works with pinpoint precision, and a handbrake which is automatically set when the driver leaves the truck further contributes to its safe operation.

As a result the “seven tonners” can be driven without stress or a loss of concentration. The ergonomic advantages become apparent when getting on and off the truck. The low access height and the step clearly visible from above contribute to the ergonomic design. This is complemented by the comfortable and spacious foot room sporting a combined brake and inching pedal, the height and rake adjustable steering column, the SOLO PILOT operating lever that moves together with the driver’s seat, and the direction of travel switch fitted to the steering column. Moreover, the floating cab is fully sealed from the engine compartment while buffer elements ensure vibration and sound damping. On top of this, the comprehensively equipped standard cabin ensures comfort, no matter how inclement the weather. Benjamin Gross leafs through his documents. “Apart from all the above, we paid a visit to one of Jungheinrich’s reference clients and made sure the DFG 670 series met our requirements profile.”

Jan Kaulfuhs-Berger
jan.kaulfuhs-berger@jungheinrich.de