Quarrying: The big payback

Terex has supplied ten 100 ton (91 tonne) capacity TR100 rigid dump trucks to work at the Ras Al Khaimah quarry, in the UAE, believed to be the largest limestone quarry in the Middle East.
Operated by a state-owned enterprise since it was opened in 1975, the quarry has a fleet of more than 250 machines, including 38 TR100s, plus 20 of the previous 3311 and 33100 models.

“We’ve got a big fleet of Terex trucks and that was a major factor in the decision to buy the new TR100s,” said technical and operations manager Simon Turner. “The equipment was partly fleet expansion, along with an element of fleet renewal. We work 24/7, 365 days a year here and working hours on a machine can easily reach 7,000 hours per year.”

The quarry reaches 800 m into the mountains behind Ras Al Khaimah, with more than 20 active benches and up to 30 km of quarry face. The lowest working area is 40 m above sea level and the highest is some 450 m above that. Using computer-aided design, geophysical drilling and laser profiling, the quarry team carries out blasting six days a week, with more than 120,000 tonnes of material being excavated each day.

Mr Turner took over running of the site last summer and has overhauled the working operation, with impressive results. The company has seen a +15% rise in efficiency and an even more impressive +30% rise in productivity, with hardly any additional machinery or personnel. Health and safety at the quarry has improved significantly.

“It is a continuous course of improvement. We’ve seen some big wins in terms of productivity, now the smaller things need to be assessed. This site is primarily about logistics, it’s a load and haul site. We have put the plan in place, now we need to prove it.

“We’ve done a lot of time cycle analysis to see where improvements can be made. We’re also looking at excessive truck idling and correct positioning for better efficiency. We look at everything from an efficiency point of view now,” said Mr Turner.

Meanwhile Vancouver-based Vertex Excavating, a subcontractor to Lafarge on a 90 ha quarry in the heart of Canada’s Pacific Northwest rain forest, has different challenges to contend with. With annual rainfall of 1.3 m or more, and even more water to deal with from melting snow on the area’s mountains, the terrain is hard to negotiate especially given that track gradients can be 20° or more.

“We are dealing with a lot of steep hills,” said Mike Pratchett, president of Vertex. “We also have to deal with almost two-mile (3.2 km) haul cycles and rain for 10 months of the year, resulting in muddy slippery slopes. You could say we have tough working conditions to contend with almost all year round.”

Vertex excavates clay and till at the quarry as well as clearing logs and over-burden, taking a role in waste management and working with the provincial and local authorities on water management and environmental issues.

The company has an all-Volvo fleet to tackle its work in these difficult conditions, with a pair of Volvo EC360B excavators, five Volvo A25D articulated dump trucks (ADTs) and a Tier 4-compliant Volvo EC380D crawler excavator on site.

The EC380D was one of the first delivered in North America. “When the machine arrived, we added a few additional accessories to it, such as the larger 60 in (1,524 mm) wide digging bucket, a hydraulic thumb and, because our contract calls for log clearing, we added the falling object protective structure (FOPS) to guard the cab from falling debris,” said Mr Patchett. “It’s a tremendous machine, plenty of power, great stability, superior lighting and a cab full of creature comforts. Even in this till and clay that has been compacted for centuries, the excavator has allowed us to improve our cycle times.”

He is also a fan of the Volvo ADTs, something that clearly runs in the family. “My dad started his business using Volvo machines, and I’ve been around them all my working life. When it came time to buy my own trucks, I wouldn’t consider any other brand. Because of the efficiency of the transmission retarders and exhaust brakes, we haven’t had to replace a single brake pad,” said Mr Patchett.

Further up the weight classes, January saw Polish aggregates producer DSS Group acquire a new 70 tonne class Hitachi ZX670LC-5 for its quarry at Pilawa Górna in Lower Silesia from local dealer Tona. The DSS Group – owned by Dolnośląskie Surowce Skalne – is believed to be Poland’s largest producer of aggregates. The facility can produce 5 million tonnes per year in grades suitable for both road and rail projects. Bulk deliveries are made by rail in a 60 km radius of the site, and the quarry’s location near the E67 highway also allows for efficient road transport of materials.“This is the first Hitachi that I’ve worked with,” said quarry manager Janusz Rydz, “but from what I’ve heard in the market, Zaxis excavators are very reliable and durable.”

He continued, “We hope that the ZX670LC-5 will enhance the level of productivity on this site. Our aim is to reduce the cost of every tonne of stone extracted. To do this, we are renewing our fleet of construction machinery and in this case we believe that we have found the best solution.”

Machine operator Boleslaw Gazda estimates the ZX670LC-5 excavates and loads some 600 to 700 tonnes of materials per hour, depending on the size of the rocks.“The Hitachi provides a very stable platform – even working in the challenging conditions of this quarry – and the loading cycle is good,” he said. “It’s also fast and precise thanks to the simplicity and efficiency of the hydraulic system.”

Meanwhile in the UK, quarry operator and civil engineering contractor GD Harries & Sons is expanding its business with the addition of four new Case machines, supplied by local dealer Riverlea. Based near Narberth in West Wales, UK, the last 18 months has seen Harries acquire four granite and two limestone quarries. It also runs three concrete production plants and three asphalt facilities, and has expanded its interests into road surfacing and other civil engineering contracting operations alongside its quarries.

The two new two CX350C crawler excavators, 1021F wheeled loader and 821F loader replace existing machines as part of fleet renewal plan. The 35 tonne CX350C excavators are now the largest machines in the Harries fleet and, along with the two wheeled loaders, will contribute to an increase in production levels within the quarry operations.

“We did price other equipment but Riverlea was able to put together the best deal for us in terms of price and quality,“ said Harries business manager Janet Phillips.

“We do have our own maintenance staff to keep the machines running, but Riverlea has always been there to look after us when we need them,” she added

Supplied in standard specification, the equipment is already delivering a boost in productivity for the company. With a continued growth in demand for aggregate throughout the region, Ms Phillips says the company will be looking for additional machinery before long.

It is often the case that new machines come with new features that can help productivity and safety. Doosan for example has launched several new features on its DA30 and DA40 ADTs aimed at doing just this.

A levelling meter uses rotation sensors installed on the front and body of the truck to tell the driver via clear graphical readouts whether or not it is safe to drive forward and to stop if there is a danger of turning the machine over.

On the productivity side, a new payload and cycle count meter uses load sensors to provide an immediate readout on the cab’s control monitor of the payload with an accuracy of +/- 5%. The load is registered and counted in the vehicle control unit. Double counting is avoided because the system will not log another load until the truck has travelled more than 50 m or after a timeout of 3 minutes.

The data can be downloaded to a USB memory stick or sent as an attachment. It is in Wordpad format and can be identified and tracked by assigning it with a serial number.

Meanwhile the new Economy mode on the trucks is designed to cut fuel costs by controlling engine speed. Doosan says the system comes into its own on long haul roads where a new powertrain and electronic control allows the engine to run at the best point in terms of power and torque.

Quiet drilling

And there can be improvements in other important areas such as noise and environmental performance. For example, Atlas Copco has

supplied limestone quarries in the Parque Natural das Serras de Aire e Candeeiros national park in Portugal with BBC 34 DSI pneumatic rock drills, which are delivering a 5 db(a) noise reduction compared to the older Atlas Copco BBD 94 DSI units. This has been a key factor in the park, which is a major tourist attraction, as well as an urban environment.

“Field tests showed that the BBC 34 DSI provides the same high penetration rate as the BBD 94 DSI, but with a noise reduction of 5 dB(A), and this is experienced by the human ear as a 50% lower noise level,” explained Torres Marques, business line manager at Atlas Copco Portugal.

The BBC 34 DSI pneumatic rock drill has a piston diameter of 80 mm and 70 mm stroke. It delivers high impact energy per blow and is suited to medium to hard rock. The large piston diameter enables it to maintain high efficiency even at low air pressure, and maintenance intervals are longer than for the BBD 94 DSI.

“Our customers no longer have concerns regarding noise levels disturbing the local residents,” said Mr Marques.

Tough crushing

The processing side of the quarrying industry also has potential to provide cost savings with correctly specified new machines. Finnish crushing contractor AB R&S Sundvik was one of the first in the world to buy the Metso’s C120 jaw crusher when it was launched in 2011. The unit has since clocked-up over 4,000 working hours and crushed some 500,000 tonnes of material.

“The long and well-designed cavity combined with a large feed opening seems to guarantee steady and high productivity. Within our operations, we have never aimed for short, high peaks but a steady, continuous production that really makes for visible results,” said Stefan Sundvik, responsible for the contractor’s crushing operations.

“The C120 cavity is also very well suited to crushing fragmented feed materials. Even difficult feed doesn’t block the cavity. Therefore, we hardly need to use our hammer,” he added.

Sundvik’s three-stage portable crushing plant is kept running for two 8-hour shifts per day. The C120 jaw is usually operated with a 100 to 150 mm closed side setting, resulting in a capacity of 250 to 300 tonnes per hour.

The Boda quarry near the small town of Vrigstad, Sweden, meanwhile features particularly hard granite, with a compressive strength of over 300 MPa in places. Crushing specialist TJ Gräv chose a Kleemann Mobicat MC 120 Z mobile jaw crusher as the primary unit with a Mobicone MCO 11 S mobile cone crusher for downstream work.

The primary stage reduces the feed material, which can be up to 1 m long, down to a 0 to 200 mm stream. The cone crusher, followed by a three-way screening system then produces 0 to 8 mm, 8 to 14 mm and 14 to 22 mm products. The plant is producing 1,000 tonnes of material per day.

Tomas Johansson, owner of TJ Gräv AB, said the Kleemann machines were was well-suited to the application. “Both plant units have a diesel-electric drive system, which has a very favourable effect on fuel consumption. Not only that, they are built very sturdily,” he said.

It is also significant that TJ Gräv chose mobile crushing and screening equipment, which is a clear trend around the world due to the flexibility such machines can offer.

Mobile equipment

Hamilton Aggregate was founded in 2006 at Bonds quarry, located in Clinton, Arkansas, US. From the outset the company opted for mobile crushing and screening equipment that could be moved to the face to crush material without the need for hauling it, and which can be transferred between quarries.

Today the set-up consists of a Sandvik mobile QJ341 jaw crusher, a QE440 scalper, a QA450 triple deck screener and an Extec X44 cone crusher. Extec is now part of Sandvik.

As company owner, Edward Hamilton said, “These mobiles are quality machines. They provide us with lower operating costs and high production for their size.”

A further quarry, Greers Ferry, operated by the company in Higden, Arkansas, was acquired to supply aggregates to a nearby bridge project.

The constant steady supply required from the Greer Ferry quarry emphasises the need for a reliable aftermarket support.

“The equipment has proved to be highly reliable, but after discussing our needs with [Sandvik distributor] Crushing Tigers we run the machines for nine hours each day, and then run a preventative maintenance schedule to ensure reliability and maximum productivity,” said Mr Hamilton .

A third facility in Quitman, Arkansas supplies material on demand to the local market. The flexibility of mobile crushers and screens comes into its own here as the units can be moved between the different quarries and quickly set up again as required.

This flexible approach has seen the company grow from a single 0.5 acre (0.2 ha) quarry to a three facility operation that has produced some 2 million tonnes of material in its short seven-year history.