CONTENTS

• Their Star Keeps Rising
   

• Purpose-built for RBM
   

• The Scale of the operation
   

For more than 20 years, Unitrans has hauled Heavy Mineral Concentrate (HMC) for Richards Bay Minerals (RBM). The challenge is delivering 3,6 million tons of HMC annually to RBM's Mineral Separation Plant (MSP). DaimlerChrysler has been Unitrans' consistent partner and supplier of truck tractors for side- tipping, trailer road- trains since 1984 when 23 truck tractors each operated with a single tipping semi-trailer. FleetWatch technical correspondent Dave Scott visited the site to observe the change from Actros to Western Star.

"The task," explains Fil Morkel, managing director of Unitrans Freight, "is a balancing act where road transport must be consistent at all times of the day and night in delivering HMC at a rate of 400 tons per hour to receiving hoppers at the plant. While transport costs are a small proportion of total mining costs, reliable transport is absolutely critical to RBM's production output." 

Unitrans has now fleeted up with nine Western Star purpose-built specification truck tractors to haul their road-trains. Western Star is a DaimlerChrysler Group product and a brand within the Freightliner Fuso stable. Canadian- based Western Star focuses on specialised vehicles with capacity welt beyond the normal off-the-shelf products they have replaced. 

Fil Morkel, managing director of Unitrans Freight (left) together with Jo Grove, chief executive of JSE listed Unitrans Ltd, were present at Richards Bay Minerals in bright safety kit. After more than 20 years, Unitrans is still keeping RBM's mineral separation plant operating 24 hours a day, 7 days a week, 365 days a year.

To their credit, standard Mercedes-Benz Actros truck tractors handled a tough task since 2001 to be replaced with purpose-built Western Stars. Nine combinations with 27 trailers that Actros pulled on a 24/7 basis remain in service with the new normal control vehicles - the visible improvements are in improved cycle times and less stress on the vehicles as the 'Westerns' handle the grades in much higher gears. 

And this Western Star deal did not come easy. Exhaustive demonstrations and reams of spread-sheet calculations went into the decision-making process. It was a massive investment in time and effort by Johan Cloete of DaimlerChrysler and Duncan Prince who manages the Western Star operation in Southern Africa. Western Star distributors Liebherr Africa (Pty) Ltd, Eaton, and Cummins made up the supporting cast for the deal.

Operating at 150 tons gross combination mass (GCM) and a total length between 40 and 45m depending on the type of trailers, the road-trains are employed on mine roads that the public use. The road-trains operate with four drivers per rig, 24-hours around the clock, in three eight-hour shifts. These impressive vehicles haul three trailers each carrying 35-ton per trailer with a total payload of around 105 tons. The Specific Gravity (SG) of the HMC is around 2,8 to determine load volume. Combined with an un-laden combination tare mass of 42 tons, 150 tons GCM is easily attained. 

No more than 2.6m wide or 4.3m high in terms of the Regulations, the whole rig runs at a permissible 9 tons per axle. Lights, glass, braking-systems and reflective
markings all comply with SABS specifications and despite their North American pedigree, the 'Westerns' are scratch-design right hand drive units. The Western Stars are equipped with daytime running lights that automatically illuminate as soon as the park brake is released to comply with mining safety regulations where vehicles must travel with headlights illuminated at all times. 

Special technical features of the new Western Star haulers include :- 

• A 565 horsepower Cummins ISX engine developing 2 500Nm is employed. Engine torque is electronically stepped, so that the engine develops 2 OOONm in the 1st six gears, then 2 300Nm in the next six followed by 2 500Nm in the top six, to prevent wheel-spin when pulling away with empty trailers. The stepped torque also takes stress off the power train when moving off in lower gears. 

• An Eaton Fuller, 18-speed Autoshift transmission with 3 050Nm capacity is fitted to make the prime mover easier to drive and also prevent possible driver abuse through inappropriate gear selection. No driver can ever move a stick shift Eaton-Fuller transmission through downshifts as quickly as the electronically managed Autoshift that changes gear very quickly - when the combination is travelling very slowly gears can change without stopping. Autoshift also allows very quick, aggressive downshifts to use the engine brake to its greatest effect. The Cummins engine brake provides the same kW in retardation as for maximum forward power. 

• 32 brake boosters are actuated when a driver applies the brake pedal. A big 1000 litres/min naturally aspirated compressor is fitted to cope with the very large air demand that three trailers and 16 axles create.

• Automatic lubrication systems are fitted to protect chassis components in a dirty working environment. A Cummins Centinel system automatically replaces old engine oil with new lubricant as the vehicle moves because fuel consumption is in excess of 1 litre per km - more than lOO litre/lOOkm - and oil change intervals would otherwise be very short.

• Visible shiny items on the truck are made from either polished stainless steel or aluminium rather than chromed steel for long-term corrosion resistance.

Spreadsheet forecasts have been converted into reality. Now comes the task of tracking the real world against expectations. The 'Westerns' certainly have enough 'grunt' to do the work and excess design capacity to provide durability. Are there any maverick issues that have been overlooked? It now falls on the shoulders of the supporting cast in this show of wheels - Western Star distributors Liebherr Africa (Pty) Ltd, Eaton, and Cummins - to ensure minimum downtime. Some task for sure! 

The Richards Bay Minerals Plant forms a dramatic backdrop for the supply of a quarter of the world's demand for pigment, welding rods, iron for ductile iron castings and zircon.

Each trailer in the mad-train has a tarpaulin that can be raised for loading and then lowered to prevent Heavy Mineral Concentrate from blowing onto the road en route to the Mineral Separation Plant.