At a depth of 1,250 metres: BPW 30-tonne axles move heavy rock underground

In Gällivare, on the northern Arctic Circle, more than 1,100 kilometres north of Stockholm, lies the Vitåfors mine. The mine, owned by the Swedish state-owned company LKAB, produces around 10 million tonnes of finished iron ore products annually, making it the second largest iron ore mine in the world. The Swedish manufacturer SLP has developed the Vincent 90 tipper semi-trailer, featuring an extremely robust running gear on BPW 30-tonne MZM axes, specifically for transporting large quantities of rock underground. 

Hans Ohlsson, Marketing Manager at SLP, has gotten to know the Vitåfors mine through numerous visits: "Its a world unto itself: a whole factory 1,250 metres below ground with workshops and restaurants, and around 800 kilometres of paved roads. You drive in by bus, which takes around half an hour. Work is carried out in two shifts, 16 hours a day. Demolition takes place after midnight, when there are no vehicles in operation for safety reasons. At other times, there is a lot of traffic here."

The SLP Vincent 90 trailers, in combination with Volvo 8x4 semi-trailer tractor units equipped for underground operation, are responsible for transporting ore and rock to one of the two crushers on the main level, which are continuously fed. The tours are short: only five to ten minutes pass between loading and unloading. According to Ohlsson, the high handling speed poses special challenges: "The SLP Vincent 90 is a side-dump truck that only needs 40 seconds to unload. It simply drives parallel to the crusher and tips directly into it. A rear tipper would take around three minutes because it would have to manoeuvre backwards first."

Extreme loads occur during loading: 100 tonnes of rock rains down into the tipping body from a height of around five metres in just 20 seconds. To reduce the energy released during this process, the floor of the tipping body is made of 10 millimetre thick Hardox 450 steel with a 100 millimetre thick rubber layer. The exact weight cannot be checked in a single go with this type of loading, as the raw ore varies in density. This is why the SLP Vincent 90 is designed for up to 140 tonnes.

The loads on the running gear and axles are accordingly high. SLP manufactures a special chassis with 30-tonne MZM axles from BPW for this purpose. Heat-treated, solid 180 millimetre square axle beams with widened track and SN 5020 drum brakes and a 24-bolt wheel connection with a reference diameter of 425 millimetres are used. The axles are designed for a static axle load of up to 60,000 kilograms at a speed of 3 km/h. SLP Manager Ohlsson: "The Vincent 90 trailer is unsprung – suspensions for these extreme weights don't exist. To compensate for uneven ground, we use BPW tandem axle units in the form of reinforced pendulum arm bogies. The twin tyres, with a diameter of 1,665 millimetres, are two-thirds filled with water, primarily to compensate for the extreme temperatures that develop when driving with heavy loads.” 

A central lubrication system on the Vincent 90 and a daily check before the start of each shift ensure that the units have a long life expectancy. All maintenance and repairs are carried out underground. SLP has delivered a total of 13 Vincent 90 trailers to LKAB to date, with the last one delivered in January 2025. The robust special tippers can be used for eight to twelve years and only leave the underground mine at the end of their working life.