New plant tailored to application

A new screening and washing plant proves to be
Andy Bateman
November 04, 2008
By
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A Caterpillar D8R dozer with a single shank ripper broke up conglomerate at the pit face.
A new screening and washing plant proves to be an excellent fit with its application.

Located just 12 km northwest of downtown Calgary, the Springbank operations of BURNCO Rock Products Ltd. are an important part of the city’s construction materials supply with aggregates, ready mix concrete and hot mix asphalt all produced there by company plants. To meet continuing strong demand, both internal and external, a new portable aggregate screening and washing plant went into service at Springbank earlier this year. The new plant has doubled the output of key washed products and combines a twin shaft blade mill with a rinsing screen and twin shaft fine material washer. 


Manager of production operations Lorne Swain explains that the 20 m deep sand and gravel deposit at Springbank has been an
excellent source of aggregates for many years but, like all natural materials, does present its challenges. The pit has the coarse gradation typical of Calgary area deposits with about 75 per cent of pit run material larger than 4.75 mm and occasional boulders up to 750 mm. At the fine end of the size range, pit run contains more 50 mesh and less 30 mesh material than ideal and blend sand is imported to optimise finished product balance. Finer still, the deposit contains occasional clay lenses which are an important consideration in any wash plant design and operation. Compared to sand and gravel deposits elsewhere, the naturally bound material is also relatively hard to excavate, particularly in the bottom 6 m or so where any cemented conglomerate present has to be broken up or cast out prior to loading. 

The job of the KPI-JCI 1830 PHB portable screening and washing plant is to produce a full range of coarse and fine washed aggregates using feedstock from the operation’s nearby dry crushing and screening spread. Overall, Swain is pleased with the performance of the new wash plant, with the company considering the addition of a second unit. It certainly seems to be well suited to its application, with natural washed round product travelling as far as
Edmonton 300 km to the north for an exposed aggregate application. The plant, reportedly the first in Canada in this configuration and one of only three built, is currently running on a continuous basis and delivering quality
product at a rate of 250 tonnes/h compared to the 130 tonnes/h of the previous setup.

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The KPI-JCI 1830 PHB portable screening and washing plant is delivering quality product at 250 tonnes/h compared to the 130 tonnes/h of the previous setup.
Aggregate production at Springbank also demonstrates the importance of a good overall fit between process, available raw material and operating environment. At the face, pit run was excavated by a John Deere 450C LC excavator, supported when necessary by a Caterpillar D8R dozer equipped with a single shank ripper to break up the conglomerate layer and push it towards the excavator. Excavated material was loaded by the 450C LC onto a contractor’s primary haul fleet of nine tandem trucks. With a typical payload of 18 tonnes, the tandems had a generally level haul of some 1.6 km to the processing area.

Between the hours of 7 am and 6 pm, trucks arriving at the dry crushing and screening plant dumped material either into the hopper of a 1066 mm x 6.1 m vibrating grizzly feeder or onto stockpiles. After 6 pm, material from the stockpiles was baled directly into the hopper by wheel loader to eliminate evening truck haul noise to nearby residences. The feeder maintained a steady feed of material to a 25x42 Clemro primary jaw crusher from which minus 3-inch crushed material was directed to a 5x16 pre-screen deck. Here, material larger than 25 mm was conveyed to a Metso 1560 Omnicone crusher while material already smaller than 25 mm is conveyed and mixes with 25 mm material from a 6x20 Clemro triple deck horizontal screen that received crushed material from the Omnicone. Finished product sizes separated by the screen were stockpiled, with the plant producing 28 mm minus material in two nine-hour shifts on the day visited. 

Some 150 m away, 16 mm minus screenings were being fed to the new wash plant by a John Deere 844J wheel loader via a 20-tonne capacity bin feeder. Feed material arriving at the plant first discharged into a 914 mm diameter twin shaft blade mill to break up any remaining clay lumps that may have made it this far from the pit face. Material from the blade mill discharged onto a 6x20  triple deck horizontal rinsing screen fitted with spray bars and 14 mm, 7 mm and 5 mm screen cloths  Coarse sizes were stockpiled while minus 5 mm sand slurry passing the screen’s bottom deck was washed and dewatered by a twin 1117 mm diameter Kolberg fine material washer underneath the screen. With the current set up and feed material, Swain estimated the plant’s product split at about 50 per cent washed sand, 10 to 15 per cent 7 mm by 5 mm washed round rock, 30 per cent 14 mm by 7 mm washed round rock and a residual percentage of plus 16 mm oversize.

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Feed material arriving at the plant first discharged into a 914 mm diameter twin shaft blade mill to break up any remaining clay lumps.
The new plant is designed with ease of operation and maintenance in mind. To facilitate screen cloth changes, the swing away design of the upper two screen discharge chutes allow direct access from the front of the screen, while all three chutes incorporate blending gates to fine tune product gradation without screen cloth changes. In addition, the operating angle of the blade mill can be adjusted, thereby changing the material retention time in the mill for differing feed materials.

When it came to selecting the power supply for the plant, fuel economy was, not surprisingly, also a consideration in plant selection. Swain reports that the generator set for the plant was originally specified with a 19-litre engine. That plan was changed when it was confirmed that a smaller Cummins 15-litre engine teamed with an Onan 500 kW generator would deliver virtually the same power while consuming only 70 per cent of the diesel fuel.  Downstream of the genset, the plant has a Cutler Hammer Motor Control Centre (MCC) as well as an Allen Bradley PLC automated control system, which provides single button start up and shut down as well as plant protection. Once running, plant operation is protected by motion detectors and interlocks between key components, while any one of four remote radio controls provide emergency shutdown if required.

For Swain, the increased capacity of the new plant has benefits in addition to meeting customer demand: “The doubling of plant capacity means that we are able to make our target product tonnages in significantly fewer running hours. For our neighbours, that means fewer hours with potential noise issues from the operation of the plant or its support equipment. It’s also good news from an operational perspective as we have increased flexibility in shift scheduling.”       

Portability is a word that crops up frequently in any discussion with Swain about processing equipment and the new plant is no exception. The wash plant can be transported in Alberta legally during the spring break period from April to June with the addition of a double axle booster. In preparation for travel, the blade mill is pivoted over the top of the fine material washer to meet height limits while the wings of the fine material washer tank are folded inwards to meet width limits. Ready for travel, the unit has seven axles including the double axle booster and a steering axle. 

Extensive environmental protection measures in place at Springbank include crushing plant enclosure to reduce noise and dust, full time haul road watering and water conservation measures. Perhaps most distinctive of these is the full enclosure of the dry crushing spread by vinyl panels. Manufactured by Norseman Inc., these panels consist of two layers of industrial grade vinyl with integral sound absorbing material. This approach was originally developed over ten years ago in BURNCO’s Indus pit south of Calgary to reduce sound levels measured at neighbours near that operation. It was found that these measures not only delivered the required noise reduction but also significantly reduced fugitive dust emissions from dry processes. Building on this successful experiment, the company’s other portable spreads have been enclosed, including the one at Springbank. (See Aggregates & Roadbuilding November 2002). 

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An Extec C15 crusher processing RAP at BURNCO’s Springbank operation.
Mobile equipment and trucks are also a major potential source of fugitive dust from aggregate operations and, recognising this, a water truck works full time at Springbank on haul roads and in the process area to minimise dust generated by the primary truck fleet, materials handling loaders and customer trucks.

Water is itself a precious commodity at Springbank as supply, including wash water for the new plant is metered. Water conservation measures include a holding area to recover any runoff from stockpiles and return it to the first of four settling ponds near the new plant. Swain adds that flocculent has been used at all the company’s operations for many years, with the cost of dry powder flocculent more than paying for itself in reduced pond clean out costs and the production of stable rehabilitation fill that quickly supports vegetation growth.

The KPI-JCI 1830 PHB portable screening and washing plant was supplied by Edmonton-based Chieftain Recycling Equipment.
Calgary, AB. based BURNCO Rock Products Limited will celebrate its centenary in 2012 as a fourth generation family business and major supplier of high quality concrete, concrete products, asphalt, aggregate and packaged products in Western Canada. Operations in the company’s Aggregate Division include owned or leased sand and gravel pits extending from Fort McMurray to Lethbridge and four retail centres for home owners and contractors.

The company’s Asphalt Division operates three stationary batch plants and two portable drum plants, located in Calgary, Edmonton and Canmore and producing a full range of hot and cold mixes.

The Ready Mix Concrete Division has more than a dozen stationary concrete plants, a company-owned fleet of over 150 mixer trucks, and five truck-mounted boom pumps.  The Calgary Central Dispatch and Truck Tracking System connects six ready mix plants, enabling dispatchers to be continuously informed of jobsite progress, truck availability, and plant capacities. For the Edmonton area, three ready mix plants have similar central dispatching capabilities.

BURNCO Concrete Products Ltd. is a CSA certified precast plant that produces a wide variety of architectural and structural precast products.

Company assets also include a cement terminal and aggregate truck fleet. 

For more information please visit the company’s website at  www.burnco.com.

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