Mobile crushing & screening plants demonstrate their versatility

The large and diverse crushing and screening sector is seldom quiet, but it seems that the last 12 months has been busier than usual in terms of changes in the industry and demanding applications.

One of the most interesting developments has been Atlas Copco's entry into the sector. The acquisition of Austria's Hartl Anlagenbau was an obvious add-on for a company that already makes drilling rigs and the associated consumables, and hydraulic breakers, as well as owning the road building specialist Dynapac.

The acquisition has added a full line-up of medium to large mobile equipment to its range, with a portfolio that comprises jaw, impact and cone crushers from 200 to 500 tonnes per hour, and screens from 200 to 400 tonnes/hour. All machines were previously sold under the Powercrusher brand.

Andreas Malmberg, president of Atlas Copco's surface drilling equipment division said, "The acquisition strengthens Atlas Copco's position as market leader within surface rock excavation and handling, as well as within recycling and road construction. The Powercrusher product-line complements our current product-offering and makes us an even more complete partner. Our customers will benefit from having the same supplier for drill rigs, breakers, road construction equipment as well as mobile crushers and screeners."

The existing Powercrusher dealer network is focussed on the US, western Europe and Russia, so joining the Atlas Copco family should open up the possibility of sales to other parts of the world and give customers more choice when it comes to buying a crusher.

"By implementing Atlas Copco Powercrusher products into the already existing world-wide network for sales and support within Atlas Copco, we increase the possibility to serve the market with our products," said Dominik Hartl, sales director for the newly-formed Atlas Copco Powercrusher.

Emissions alert

Another big change that the industry is having to contend with is the move to the more stringent Tier 4 Interim and Stage IIIB engine emission laws in the US and EU at the start of this year. Emissions of gaseous pollutants like nitrous oxide (NOx) have to be reduced, along with a big cut in particulate matter - the black soot that is often associated with diesel engines.

The first stage of the new laws covers 130 kW to 560 kW engines, which impacts on any diesel-powered crusher over about 120 tonnes per hour. The good news for customers is that the new engines are a little more fuel efficient than their predecessors, the bad news is that the additional systems to control emissions inevitably mean a higher purchase cost. Servicing may also be more complex, but engine manufacturers are adamant that there won't be any reliability issues with these new, more complicated units.

But perhaps the most important point as far as the global construction industry is concerned is that these machines require ultra low sulphur diesel (ULSD) - 15 parts per million or less - to run correctly. According to Cummins if a there is the occasional refill with higher sulphur fuel, there probably won't be an issue. "A one-time inadvertent tank of diesel fuel with greater than 15-ppm sulphur content will not damage the engine and after-treatment system. The system will clean itself out when ULSD is re-introduced," said the company.

However, it continued, "Continued improper fuel use of sulphur levels greater than 15-ppm with Cummins Tier 4 Interim engines can permanently damage the engine and after-treatment systems within a short period of time. This damage could possibly cause the engine to be inoperable and cause unplanned downtime and expenses."

This means that anyone buying a used diesel-powered crusher or screen in a country where ULSD is not available in the off-highway market, should take particular care that they are not buying a Tier 4 Interim/ Stage IIIB compliant machine. At the very least they should contact the manufacturer to see if it is possible to 'de-Tier' the machine and remove or replace the various engine components that would be damaged by high sulphur levels.

Another impact of this is that some mobile crusher and screen manufacturers are changing engine suppliers - either just for their Stage IIIB and Interim Tier 4 machines, or across their entire ranges. Terex's Powerscreen subsidiary for example is going to Scania engines for the machines it sells into the EU and US.

In action

Powerscreen scored a hit with Richmond, California, US-based quarry operator and recycling contractor Dutra Group when it sold the company a new diesel-powered track mounted crushing and screening system at the end of last year. The company had previously been using a wheel-mounted, electric powered crushing, screening and conveying system that it would transport four times per year between its basalt quarry and various concrete recycling facilities up to 35 miles (56 km) away.

Although the distances were not huge, with all the facilities located in the San Francisco Bay Area, each move required four people, 11 truckloads and took 11 days. The new Powerscreen system needs just two staff, four trucks and two days to move.

"The old system was too complicated, cumbersome, and was costing us too much in lost production time, maintenance time and expense, and moving costs," said Quarry Manager Jon Guglielmini "Each move cost about US$ 25000 one way, or US$ 100000 for four annual moves. In addition, we lost a total of 44 production days for four moves. With the new Powerscreen system, each move costs about US$ 10000, or US$ 40000 total for four moves, and we lose only eight production days total."

He added, "Sometimes we want to move the crushing and screening system from place to place within the quarry, to follow the face or put the equipment down in the pit. Moving the old wheeled system took two days. Moving the new tracked system takes two men about three hours."

The system supplied by Powerscreen comprises an 1180 Premiertrak jaw crusher, two 1300 Maxtrak Automax cone crushers, a Chieftain 2100X double-deck dry screen, a Chieftain 2100X triple-deck dry screen, and a tracked conveyor.

The Premiertrak is designed for high output in quarrying and recycling applications, while the cone crushers are used as secondary and tertiary units to produce well-shaped sub-base and aggregates, with excellent cubicity, throughput and reduction ratios. The Chieftain screens meanwhile are designed for large volumes and the three-deck version has a patented hydraulically folding re-circulating conveyor.

"We have none of that with the new system. Tracks don't get mired in mud. We just drive the equipment into place and start the engines. The most we might have to do in addition is to build a ramp a foot high to the jaw plant sometimes. When we move the system, the tear-down and cleanup are quick and simple; we drive the equipment onto lowboy trucks, and off we go," said Mr Guglielmini .

He concluded by saying, "I will go so far as to say that I believe tracked crushing and screening equipment, with its versatility and mobility, is the only way to go in California's aggregates and recycling industry. Nothing else makes as much sense to me."

3000 tons per hour

On the opposite coast of the US meanwhile, Palm Beach Aggregates of Florida has more than doubled its quarry production and cut costs thanks to a 3000 tonnes (2727 tonnes) per hour tracked impact crusher from Grasan.

In an unusual quarry layout, the impactor feeds a 2000 ft (610 m) floating conveyor that can be moved with outboard motors. This in turn can be connected to four land-based belts that transport material to a fixed crushing plant for final reduction.

The new system replaces two 500 tonnes per hour impactors - one stationary and one portable - which had to have feed material transported to them by wheeled loaders.

"That system was much too slow, burdensome and expensive," said the quarry's operations manager, John W. Bates. "We were using about 6000 gallons of diesel fuel per day to operate the crusher, seven haul trucks, two loaders, a bull dozer, a grader and two water trucks. We needed operators for all that equipment. We had high maintenance costs and shut-downs that occurred far too often."

Explaining the decision to invest in the new plant, Mr Bates said, "To increase our production efficiency and capacity, I saw basically two choices. I would need two large crushing plants or one gigantic crushing plant. I figured one plant would take half the maintenance time, half the parts to stock, less crew personnel time, and a lot fewer headaches overall. But it would have to be like no crushing plant I had ever seen before.

"I wanted 3000 tons (2727 tonnes) per hour crushing capability, and I wanted the crushing plant track-mounted to propel at various angles up to 90 degrees. I wanted a scalping screen and an apron feeder that would accommodate a very high volume of incoming material. And the plant had to have a 4160 V electrical system - everything in the pit is 4160 V"

Grasan was one of the few companies interested in, and capable of supplying such an unusual plant. The various components of the machine include a Williams horizontal-shaft, four-blow-bar impact crusher with a Williams 6 ft x 50 ft (1.8 m x 15.2 m) apron feeder and Simplicity 7 ft x 20 ft (2.1 m x 6.1 m) vibrating grizzly bar scalping screen. This is fitted with a hydraulic breaker to reduce over-sized feed material.

The 120 ton (109 tonne) hopper is 24 ft (7.3 m) wide, 29 ft (8.8 m) long, and 9-½ ft (2.9 m) high. The plant as a whole is 47 ft (14.3 m) high, 39 ft (11.9 m) wide, 122 ft (37.1 m) long - 183 ft (55.8 m) with discharge conveyor - and weighs in at 1.2 million lbs (545 tonnes).

The chassis mounting consists of two pairs of custom-designed tracks with 40 in (1.02 m) wide smooth pads and self-levelling stabiliser legs. They are powered by two 300 hp (224 kW) electric motors, providing a travel speed of up to 0.5 miles per hour (0.8 km/h) and up to 90° of rotation.

The discharge conveyor is 60 in (1.52 m) wide and 75 ft (22.9 m long), and this feeds a wheeled rolling hopper mounted on the 2000 ft (610 m) floating conveyor. This ultimately leads to the stationary secondary and tertiary crushing plant, which can produce up to 14 different products for concrete, asphalt and road bases, among other applications.

Bypass workhorses

In Oman meanwhile, a QI430 tracked impact crusher and QA450 mobile screen are being used on the construction of the OMR 19.5 million (US$ 51 million) 32 km, four-lane bypass around the south-western coastal city of Salalah. Building the road is part of a wider project to develop the area with an expanded port, free trade zone and industrial park.

The main contractor is The Oman Building and Contracting Company , which worked with

Sandvik dealer Al Fairuz Trading & Contracting Co. to source the correct equipment for the work. This included the QI430 track-mounted impact crusher, which is powered by a 330 kW Caterpillar C-13 engine and features Sandvik's own CI322 impact crusher at its heart. Fed via a two deck pre-screen, the crusher is a four hammer open style rotor with a diameter of 1.15 m, and a width of 1.33 m that discharges onto a secondary pan feeder.

Sandvik has also supplied a QA450 mobile screen to the project, which features a triple deck screen box and extra side conveyor, enabling it to produce up four products plus one oversize from the tipping grid.

The material being processed is known as "wadi- gravel", which consists of a mixture of limestone and basalt. The feed material can be as large as 500 mm, and the two Sandvik units are being used to produce 0 - 5 mm, 5 - 12 mm and 12 - 22mm gradings. Throughput has averaged out at around 250 tonnes per hour over the last 12 months of the project.

There is also a Sandvik QA340 on site to produce a 0 - 50 mm product. This machine consists of a heavy duty impact crusher with a recirculation system.

To date the Sandvik machinery has proved equal to the task in processing the material, working twenty hour days and helping to keep the project on time.

Fuel savings

In the UK meanwhile, Kent-based quarry operator and waste manager Pinden has taken delivery of a Mobicat MC 110Z mobile crusher from Kleemann, a subsidiary of Wirtgen. Company director Steve Bishop said he opted for the machine, despite its higher cost compared to some competitors, because of Kleemann's reputation for superior build quality and its potential to deliver significant lifecycle fuel and other savings.

"We had the machine on demonstration, first. We were convinced we can make considerable savings in fuel consumption over the lifetime of the machine. We also found output to be higher, and the quality of product was better, than previous machines. Normally we would replace our crushers after three years; we expect to get five years from the Kleemann, with lower component replacement costs over that time. Wear parts are of a much better quality," he said.

One of the key features of the machine is a pre-screen which reduces fines before crushing, reducing wear on the manganese steel jaws. Kleemann southern area sales manager, Aidan Gillic, said the Mobicat should be good for annual fuel savings of up to UK£ 15000 (US$ 23600) compared to competing machines, adding that the fixed jaw life could exceed 2000 hours before replacement.

The Mobicat track-mounted single toggle jaw crusher is designed for pre-crushing natural stone and mineral construction waste for re-use. The crusher inlet measures 1.10 x 0.70 m and the transport weight is 45 to 50 tonnes. Features include a vibrating double deck pre-screen, while power comes from a 226 kW diesel engine. Electronic controls, including an LCD screen, are standard features, and there are connections for cable remote control as well as 230 V and 400 V electrical outlets. Options include an electric or permanent magnetic separator.

Record plant

Pilot Crushtec has installed its largest modular plant to date at a limestone crushing site in Ndola near Lusaka, Zambia. Owned by local company Zamm Imports Ltd, the facility includes 18 Pilot Crushtec machines and was commissioned in July 2010.

Included in the deal were a Trio MJ3042 jaw crusher, three MC 1000 11m conveyors, an MC1050 20m conveyor, a DD4815 double deck screen, an MC800 16m conveyor, an MC800 20m conveyor, a Trio MC130 standard cone crusher, an MC130 short head cone crusher, an MC1200 25m conveyor and a Trio TD6118 triple deck screen, all from the company's Pilot Modular range.

Zamm Imports owner Jignesh Soni said that the plant will initially be used to produce 2000 tonnes of 0-5mm, 5-10mm, 10-19mm and 19-25mm aggregates per day.

"The Ndola area has the largest reserve of the finest quality limestone in Zambia and we will be using the plant to supply the booming construction sector and the mining sector, where the limestone is used to neutralize acid," said Mr Jignesh.

He continued, "After many enquiries to various South African and Chinese companies, I was shown the full range of Pilot Modular/Trio crushers at Pilot Crushtec which particularly impressed me as this approach eliminates the need for any civil works, which can take up to a year to set up and commission," he explained.

These applications all go to show how the crushing and screening fraternity is rising to the challenge of providing flexible, economic equipment to an ever more diverse and demanding market.