ADTs overtake rigid trucks at Linhay

The versatility of articulated trucks, along with availability of larger machines, means they are gaining ground on rigid alternatives. Claire Symes reports

Glendinning's Linhay Hill Quarry used to operate a fleet of rigid dump trucks (RDTs), but over the last year the fleet has gradually been replaced by smaller articulated machines. The UK-based quarry operator initially trialled one 40 tonne articulated dump truck (ADT) but has now ordered a second for the site near Ashburton, Devon.

"We wanted to see if 40tonne ADTs could replace our fleet of 50tonne rigids," explained Linhay Hill Quarry supervisor Reg Perrow. "Having operated 473 Volvo A35's for a while primarily on overburden removal and moving material around the stock piles, we were reasonably confident about Volvo's larger truck for hauling from the face and are pleased to say it passes the test here at Linhay." The two Volvo A40 machines will replace the quarry's Euclid R50 and R60 trucks and become the prime haulers in producing 500000tonnes of limestone per year from the site.

But Linhay is not an isolated case, more and more quarries are opting for ADTs to replace RDTs because they offer greater versatility.

"RDTs are still the best for long hauls with good conditions, particularly if the material is very hard or in large blocks. The choice also depends on the material - for sand and gravel deposits which are generally lighter than blasted rock, then an ADT is better suited to the hauling task," said 395 Caterpillar ADT marketing product specialist Robert Macintyre. "But looking at each quarry there are always site specific features that dictate the design of the site and there are a lot of quarries that operate with poor traction or steep haul roads where ADTs are better than RDTs."

Upsizing

According to 3652 Terex global products manager articulated trucks George McNeil, the trend towards ADTs has emerged in the last five years. "There has been a general move towards increasing the size of the machines they use and opting for 35 to 40tonne ADTs, in general," he said.

"There has been some development of 50tonne class machines - 2983 Bell was the first to launch in 2001 and others have followed - but these are still only popular in certain regions. These machines have helped with the trend towards replacing RDTs though." Nonetheless, Bell European managing director Marc Schürmann revealed that the company is working on an even bigger machine to add to the 40tonne B40 machine launched earlier this year. "We are working on a larger ADT which we hope to have on the market in the next 12 months to two years," he said. "It is still in the development stage but it is very much an ADT concept aimed at the rigid truck market. The kind of sites we expect to benefit from this new development are either high production quarries or mining applications." Macintyre believes that one of the factors driving the trend towards ADTs is cost. "More customers are questioning their levels of cost and productivity and that is a good thing," he said. "The lower initial cost is a factor in the choice but the whole life is more important and needs to be considered in terms of cost per tonne to really understand the impact of productivity." McNeil agreed and added, "RDTs generally have a longer life expectancy but have a higher initial cost. One of the major challenges facing ADTs is the arduous conditions within the quarry - the lifespan of a machine in a quarry tends to be shorter than in other applications and shorter than that of an RDT in the same environment.

"Nonetheless it is generally accepted that RDTs are 30% less expensive in terms of repair and maintenance. I know one operator who has replaced all of his RDTs with ADTs and is very pleased with the lower fuel costs per tonne and the higher productivity, which may be true over five to seven years but it may not be the case over a longer period." However, it is the versatility that adds to the benefits of ADTs. "They can be used at every point during the extraction process from removal of the topsoil to hauling of the aggregates and final restoration of the site," said McNeil.

Recent developments in the market have also helped to add to the versatility and one of the latest machines from Bell is a case in point. At 432 Intermat the company unveiled its 25tonne B25N ADT which uses a narrower bin and ROPS/FOPS cab to combine on-road use in some countries with use of loading facilities normally only suitable for on-highway trucks.

Technology

While ADTs are getting larger and more specialised, recent development has also helped to improve the suspension and drivelines on articulated haulers to make them more comfortable, improve efficiency and reduce wear and tear. "One of the next phases of ADT development will be the addition of new engines to meet the next stage of the emissions regulations in 2011 but there are also more developments to come in terms of making the machines more operator friendly and comfortable," said Macintyre.

"But I think it will be more a case of evolution rather than revolution for ADTs over the next few years." Some quarries have started to favour conveyors over ADTs due to the lower operational costs and need for fewer skilled operators, but Macintyre believes that the versatility of ADTs still gives them a competitive advantage. "Conveyors may provide and alternative for some quarries but ADTs offer flexibility," he said. "Conveyors have significant time and costs linked to setting them up but if there is a breakdown then it can severely impact on the whole site, whereas it is easier to cope if one ADT out of a fleet is out of action.

"The cost and time involved in moving a conveyor as extraction progresses also has a big impact on production."