Whorouly is a town in Victoria’s northeast, 275km from Melbourne and 35km southeast of Wangaratta. It is nestled between Snow Road (which runs from an interchange on the Hume Freeway) and The Great Alpine Road.
The town is located in the valley of the Ovens River and was first surveyed and proclaimed in 1868. It is surrounded primarily by agricultural land (originally released in 130 hectare lots) that has been used for sheep, beef and dairy cattle farming, as well as grain farming, orchards and market gardens, timber manufacturingand more recently wine grape growing.
Despite being nearly 150 years old, Whorouly, as of the 2011 census, had a modest population of 519. Of this number, 274 were in active employment (the Census’ records will not accommodate the total employment numbers in the Whorouly region, as there are likely to be employees who commute from other parts of the Rural City of Wangaratta). Their occupations included labourers, technicians, trade workers and machinery operators.
There are numerous quarries in the Wangaratta local government area, so the industry’s presence is not insignificant.
Mawsons Concrete & Quarries, which has catered for regional communities throughout northern Victoria for over a century, purchased the sand and gravel quarry at Whorouly in early 2014. The company’s intention, according to Trevor Gilbert, who is the regional manager for Mawsons’ quarry division, was to extract aggregates and sand at the Whorouly quarry for the decorative aggregate market and for supplementary use as a coarse sand at Mawsons’ concrete plants. The quarry produces a full range of aggregates, including 7mm, 10mm, 14mm and 20mm fines, the aforementioned coarse sand and decorative and garden pebbles, ncluding 20-60mm, 60-150mm and 300mm pebbles.
{{image2-a:l-w:640}}The geology of Mawsons’ Whorouly Quarry, however, is unique, compared to even most sand quarries. The quarry is located on a completely flat parcel of former agricultural land. The sand deposit is located close to the water table and Gilbert said that as the valley gets muddy and “very clayey”, the sand recovery rates for the operation become more problematic.
“It’s basically a river deposit and it is quite deep,” Gilbert explained. “We usually wait until November before we start operating because the river level goes down and that means the ground water across the region drops.”
Mawsons has employed earthmoving equipment, including a 45-tonne Komatsu excavator with a 2.2m3 bucket, a Caterpillar 950G sales loader and articulated dump trucks, to dig out and transport the sand deposits. It is a condition of Mawsons’ licence that it is not permitted to install and operate fixed plant on the Whorouly site. As a result, Mawsons relies very heavily on mobile plant and equipment at Whorouly and until recently it was employing a Terex Finlay 683 Supertrak rinsing screen and a dewatering screw to wash and process
the sand.
{{image3-a:l-w:640}}“We were running the sand/slurry out of the bottom of the 683 into the dewatering screw,” Gilbert said. “A dewatering screw is good for dewatering but it’s not good for fines recovery. It did a good job and it did what it was designed to do but because the silt and clays in this product are so low, the more water you put in, the more fine sand you wash out. There was nothing we could do to recover it and we were sacrificing tonnage to basically recover what sand we could get. We decided we needed to look for an alternative.”
Combined wash plant
In 2014, Mineral Washing Systems (MWS), a subsidiary of Brisbane-based supplier Finlay Screening and Crushing Systems, began importing Terex Washing Systems’ (TWS) extensive range of sand washing plant and equipment into Australia, including the modular AggreSand 165. The first of these plants was installed in Dubbo, New South Wales, and at MWS’s invitation, Gilbert and other Mawsons personnel visited Dubbo Sands to see the plant in operation. They were impressed by the plant and after consultation with MWS representative James Murphy, they negotiated a six-week hire with the option to buy two pieces of TWS plant: the mobile M1700 rinsing screen and the modular Finesmaster (FM) 120C compact cyclone plant.
{{image4-a:l-w:640}}At the time Quarry visited Mawsons Whorouly, the business had been operating the M1700 and the FM120C for six weeks. The combined wash plant had spent its first four weeks at Mawsons’ Mansfield Quarry operation before being relocated to Whorouly for the next fortnight. This enabled Mawsons to test two different materials on the plant at separate quarries, as well as trial further materials brought to Whorouly from its Seymour and Mildura sites. It also illustrated to Mawsons the ease of relocating the plant across multiple quarry sites. According to MWS sales engineer James Murphy, who worked closely with Mawsons on the installation of the M1700 and the FM120C, the plant was moved from Mansfield to Whorouly within three days, including washdown, demobilisation, freight, set-up and commissioning.
Murphy said that the M1700 and FM120C can be operated independently but when the two machines are run together, they offer the “exact same wash plant in principle” as the TWS AggreSand 165, albeit on a mobile platform.
{{image5-a:l-w:640}}“Some operators will only require rinsing of, say, crushed aggregates and if what is being rinsed away with the water is not of value to them, they will discharge any fine material with the dirty water,” Murphy explained. “But when a client then wants to recover the sand being rinsed from the aggregates, as is the case with Mawsons, we recommend a modular Finesmaster sand recovery system sized appropriately for the tonnage/ throughput required. It’s the combination of these machines working together that becomes a wash plant, as opposed to a rinsing screen working independently.”
Rinsing screen
The M1700 is a fully mobile washing plant that can be used in sand and gravel, crushed stone and recycling applications, is capable of producing up to five end products and features on-board hydraulically folding side conveyors. Murphy said that compared to other screens in the market, it has “been designed from the outset with washing as its principle use. It has a 16’ x 5’ three-deck screen with over 140 spray nozzles that give full spray coverage and produce three clean aggregates. The bottom deck of the screen can be split to produce up to two grades of sand when required and the twin grade catch box with incorporated adjustable division plates makes for easy blending between the sand grades.
{{image6-a:l-w:640}}“From a maintenance point of view, the M1700 has a quick release wedge tensioning system on the top and middle decks, and the hydraulically adjusted screen and catch box make the changing of mesh a lot easier. That’s quite a favourable option to have from the operator’s point of view,” Murphy commented. “There’s also an
option for the machine to come with a fines conveyor to enable its use in a dry screening application, thus making it a versatile machine in any mobile fleet.”
Murphy said that once its customers are happy with the size of the mesh and the gradation is correct, MWS recommends a poly-coated wire woven mesh which offers up to 10 times life expectancy in comparison to a standard or hardened steel wire woven mesh.
“That’s particularly important in a washing environment where the presence of water increases the wear rate on your mesh panel,” Murphy added.
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Compact cyclone
The FM120C is a modular sand recovery unit on a single chassis. It is available in either a dual or single grade configuration washing up to two grades of sand (Mawsons at Whorouly was using the FM120C single grade to produce only one grade of sand) and can be employed for numerous applications, including concrete, mortar and asphalt sands, quarry dust and crushed fines, lake and beach sand, silica sand for the glass industry, golf course sands, filter bed sands and recycled materials. It is equipped with a 150mm size centrifugal pump with a pump capacity of 250m3, a single rubber-lined G4 660 hydrocyclone that classifies at 75 microns (200 mesh), a self- regulating cyclone tank with incorporated float system and anti-turbulence sections, and a 12’ x 5’ dewatering screen.
“The slurry – or the combination of the water and the sand that rinses through the bottom deck of the M1700 – passes via a 10-inch pipe to the Finesmaster unit,” Murphy explained. “All sand is pumped with water from the bottom of the sump tank to the cyclone, thus separating any organic matter which will be floated off via the weir. Any silts and clay content in the sand will be discharged through the top of the cyclone and is returned to the sump tank. The sump tank is quite innovative in the sense that it’s a self-regulated system; when the water level in the sump tank is too high and weiring over excessively, the dirty water from the cyclone will discharge directly to the tailing ponds; if the water level is at the desired level, it will discharge back into the sump tank to help regulate the water level again.
{{image8-a:l-w:640}}“The FM120C is capable of processing up to 100 to 120 tonnes per hour, this obviously depends on the gradation of the material.”
The advantage of the self-regulating cyclone tank, together with the built-in float system and anti-turbulence sections, Murphy said, is that there is a major reduction in the volume of saleable material discharging to the tailings ponds and in turn reducing pond maintenance and saving money in the long run.
“The washed material that is discharged on to the dewatering screen will have seen a reduction in the silt and clay content present,” Murphy explained. “That washed sand is discharged onto a stockpiling conveyor at a level of between ten to 15 per cent residual moisture content. The aggressive vibration, typically 5G acceleration, generated by the 12’ x 5’ dewatering screen allows for the removal of capilliary moisture which other dewatering systems will not achieve. The result is that the sand can be loaded directly onto trucks without the need for an extended period of drying. As an added bonus, this can help reduce the area being taken up by stockpiles in a sales yard.”
It is also possible for the FM120C, like other Finesmaster units, to be incorporated into existing mobile or static wash plants. “The modular design of the Finesmaster range means that they can be easily retrofitted or added into an existing mobile or even static wash plant, for example, replacing a cyclone tower,” Murphy added.
The FM120C is just one of several variations of the Finesmaster plant designed by TWS to suit different applications. “The Finesmaster Compact that Mawsons is using here is most suited to river gravel applications, where organic material is an issue. There’s also a Finesmaster bucket wheel that is used in quarry dust and manufactured sand applications, where the material is more abrasive,” Murphy said. “The bucket wheel relieves some of the burden from the pumps and cyclones, reducing wear to these high value components.
“There’s also the Finesmaster Direct Feed, a machine which is suitable for pre-screened material with minimal oversize, for example dredging operations. The Finesmaster Super Fines enables classification at approximately 40 microns for fine sand applications. Each of these varieties of the Finesmaster range offer throughputs ranging from 20 to 200 tph. We can match a machine with a customer’s specific requirements, thus keeping capital expenditure and running costs down.”
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Cautious optimism
The feedback from Mawsons about the performance of the combined mobile wash plant at Whorouly was cautiously positive, given the M1700 and the FM120C had only been in operation for a short time. “I must
say I’m impressed on the results we’ve had so far,” Gilbert conceded. “It’s just been so trouble-free, we’ve just put the plant to work and we haven’t done anything too differently. We’ve just kept our eyes on the water flows but otherwise, it’s taken care of itself, we have not had an ounce of problems.
“The biggest benefit,” he continued, “is that we won’t have to clean up our clay deposits s often now because we won’t be putting as much out there. Maybe we can get the cleanouts out to six months and reduce them further from there. That has certainly been one major improvement.”
Murphy said the feedback from Mawsons had also been encouraging for MWS. “The feedback from Mawsons has been very positive and they were particularly impressed with the ease and speed of relocation between sites, and the re-commissioning of the wash plant. The results from testing of samples that were processed have indicated a higher retention of fine sands than previously achieved which backs up the theory of the cyclone system. With the addition of a fines conveyor for the M1700, they are happy with the versatility this machine brings to their mobile fleet.
“From the outset, Mawsons have wanted a system that will produce consistently clean sand and aggregates whilst retaining as much bottom end fines as possible. The second requirement was that it would be flexible enough to be re-located between sites with minimal set-up time.”
“Basically, at the end of the day, we wanted tonnage and to recover what sand is capable of being recovered for our concrete plants,” Gilbert summed up. If you have to import fine sand, then that costs us money. If we can reduce those costs by even five per cent, then we’ve made significant savings.”