Productivity gains in off-road haulers

By Chris Sleight09 November 2010

Caterpillar uses the concept of ‘target payloads’ for its haulers. The 777F for example is at its mo

Caterpillar uses the concept of ‘target payloads’ for its haulers. The 777F for example is at its most efficient when it is hauling a 91 tonne load.

Many of the haulers used in the construction and quarrying industries will be affected by the Interim Tier 4 (US) and Stage IIIB (Europe) engine emission laws next year. The first powerband subject to the stringent new laws is 130 to 560 kW engines, which translates to haulers from about 20 tonnes to 65 tonnes capacity.

That covers all the major classes of articulated dump trucks (ADTs) as well as many of the sizes of rigid haulers used in quarries. Bigger trucks with engines over 560 kW are outside the scope of the law.

So with manufacturers poised to renew their hauler ranges in just a few months in response to this new law, there has been little activity in the last few months in terms of new machines. But one exception has been Terex.

New models

Over the last two years it has introduced new versions of all four of its ADTs. This started last year with the 38 tonne capacity TA400 and has moved down the weight categories to the 25 tonne TA 250, which came out in June.

Part of the impact of the upgrades - and this is true for other manufacturers - is that the nomenclature conventions are changing. It used to be the case that the numeric part of any manufacturer's ADT model number referred to its payload capacity in short tonnes. So anything ending in a 25 or a 250 meant it had a 25 ton (22.7 tonne) capacity.

However, upgrades over the year shave seen capacities edge up while the product names have stayed the same, to the extent that Terex's new TA250 has a 25 (metric) tonne capacity thanks to its 15.5 m3 body.

Besides this, some of the most noticeable changes on Terex's new trucks are in the cab, with new trim and seating, relocated controls to make operation easier and better air conditioning. The machines are also quieter than their predecessors - both inside and outside the cab.

Technical advances include the use of enclosed oil cooled brakes throughout the range and a fully suspended front axle as standard. Terex says only a few other manufacturers offer a suspended front axle, and that it is an option rather than standard equipment. This makes for a more comfortable ride.

Another important feature is the two-stage automatic or manual engine brake. This retards the hauler when it is going downhill without applying the service brake, which makes for safe driving without unnecessary wear.

New player

This year was also notable for a new entrant into this niche area in the shape of Liebherr. The company has made large mining trucks for many years, but April's Bauma exhibition in Munich saw it enter the ADT market for the first time in its history with the 30 tonne capacity TA 230. The range is eventually expected to cover the 30 to 50 tonne capacity sizes.

The development of the ADT is reported to have taken Liebherr a decade or more. When it launched the R&D project, it initially looked to develop a hauler with a hydrostatic drive, which would have been unique in the market. However, although performance was better, the company felt this was not justified by the much higher cost, so it started again with a traditional mechanical drive.

Liebherr says a key feature of the TA 230 is its compact dimensions, with a transport width of less than 3 m, although it is still able to offer a 19.2 m3 body. Top speed is 57 km/h, and features include oil cooled breaks, a 6 x 6 driveline and four reversing speeds up to a maximum of 16 km/h.

The first big order for these trucks came from Liebherr's in-house rental arm, Liebherr Mietpartner, which will add up to 55 new trucks this year to refresh its fleet in Germany and France.

Bell Equipment meanwhile, has been stressing its credentials as an ADT specialist, with a focus on special adaptations for niche applications and special customer needs.

Bell Equipment UK managing director Neville Paynter said, "We go to great lengths to listen to our customers' specific needs, which can often lead to a bespoke machine for a specific operation. The market for specially designed machines is clearly limited in volume, so machines are more costly, but at Bell we do believe it's important to show our customers we are listening and that we can provide solutions."

As a specialist manufacturer, Bell also puts a lot of emphasis on the strength of its core machines, the latest incarnation of which is the Mark-VI series.

"The Mark-VI release incorporated a lot of state-of-the-art electronic upgrades and a redesigned cab and operational features for greater operator comfort, as well as an intelligent real-time machine information centre with advanced diagnostic capability. We could easily have mothballed these changes until times became easier, but I think it is of great credit to Bell as a global manufacturer that we've stuck to our guns," said Mr Paynter.

As a result of a strategic investment in Bell in 1999, John Deere owns 32% of the company. The deal gave John Deere access to Bell's ADTs for its product portfolio along with exclusive distribution rights in North and South America.

This means that the Deere and Bell ranges are near-enough identical, although their nomenclature is a little different. Bell's Mark VI ADTs are the same as the Deere D-Series II machines, for example.

Perhaps the most important state-of-the art feature on these trucks referred to by Mr Paynter is the on-board weighting system, which can be accessed remotely to monitor truck utilisation.

John Deere's ADT product manager, John Chesterman said, "The onboard weighing system helps the operator manage his productivity and uptime. You can monitor material moved data right from your desktop via the information transmitted through JDLink. This helps in calculating machine utilisation and managing a project."

"Because John Deere ADTs already have a significant weight advantage and the lowest ground pressure among the top five ADT manufacturers, Deere trucks burn less fuel, particularly in high time-on-grade applications and poor underfoot conditions," he added.

Fuel efficiency

With haulers being such big machines, with thirsty engines, fuel economy can of course be a major issue. It is something that is likely to come into even sharper focus next year, as new machines with (hopefully!) more efficient engines and more sophisticated drivetrains and controls.

However, saving fuel is not all about the machines. There is a lot that can be done in terms of planning a site to minimise fuel consumption, and they way operators actually drive machines can also have a big bearing.

"It starts with putting the right equipment together," said Angel Luis Gonzalez Suarez, Caterpillar's system application specialist for core products. "For example, if we know we have good haul roads and a lot of material, it' makes sense to think about rigid trucks. But if we are on high rolling resistance in a pioneering type site, then ADTs might be better.

"We always tell people to haul the material once. One of the things we see often is double movement - moving the material from A to B than from B to C. When you can move it from A to C there is a big improvement in efficiency, in both time involved and fuel burnt."

Another factor is making sure machines are loaded correctly with the right amount of material.

"We design our machines and rate our engines to work on a target payload. A 777F (rigid hauler) for example has a target payload of 91 metric tonnes. As soon as the truck gets overloaded the engine runs at a higher load and you're burning more fuel. If you under-load the truck and carry less than 91 tonnes the engine is at a lower rpm, but you have to do more cycles, so you are burning more fuel for the same amount of work," said Mr Suarez.

Driver behaviour is also an important factor, and according to Mr Suarez operators who are gentle with machines burn less fuel.

"Pretty much the most important element of fuel efficiency is operator behaviour. It is very similar to how you drive your car. If you drive in the highest gear possible, drive smoothly and so on, you're going to burn the least fuel. When operators that are very, very aggressive - accelerating hard and trying to get the machine to the maximum revs, that burns a lot of fuel."

In a bid to address this, Caterpillar has launched a scheme run through its dealers called Eco Drive, which aims to tech operators the best techniques for using machines

"It consists of a bit of theory in the class room and practice in a quarry or a mine. That illustrates these theoretical practices and we actually measure the performance with aggressive techniques as opposed to the best practices," said Mr Suarez.

A similar scheme is available through Volvo and its dealers called Eco Operator. One company to take part in this was Sweden-based contractor Skanska, and according to quality manager for the company's asphalt and concrete business in west Sweden Krister Persson, the results have been stark.

"We use over 10 million litres of diesel every year, so even slight reductions in diesel fuel consumption can make a big difference on the environment and our economy. We've lowered consumption by about -5%. That translates into a cash savings of about € 0.25 million (US$ 0.33 million) and an emissions reduction of about 500 tonnes of carbon dioxide".

He added that operators said they were less fatigued at the end of a shift as a result of the improved driving techniques.

Another participant in the scheme, the Terås Bergstäkt gravel pit and quarry in Ljungskile, Sweden also saw significant results. Production manager Jerker Carlström said that after taking part in the scheme, some of the quarry's operators reduced their fuel consumption by -20% to -25%, with no reduction in productivity.

Changing habits

This is a powerful point. The next generation of haulers may be more efficient due to their new engines and increasingly sophisticated transmission systems, but it is unlikely that all this modern technology will deliver a fuel saving as striking as -20% or -25%.

The argument in favour of training is even more powerful when you consider how small the cost is compared to a few months of fuel bills for a hauler, let alone the price of the machine itself.

Latest News
Bidders shortlisted for US$2.5 billion bridge
Preferred bidder for major project in Nigeria set to be announced this year
Amsterdam to host EDA convention
Mid-June dates for European Demolition Association in 2023
Demolition summit heads to Canada for first time
The World Demolition Summit (WDS) is heading for another new venue next year as it celebrates its 15th edition.