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Silent Screen: Bringing quiet to an aggregates operation
September 16, 2008 By: Darren Constantino, Questex Media Group LLC Pit & QuarryRob McDougall is trying to be a good neighbor. McDougall is site manager at Dufferin Aggregates’ Acton Quarry, which sits northwest of Toronto and supplies the metropolitan area with a variety of aggregate products.
Like many producers in the region, Dufferin faces community opposition to its operation and to the company’s desire to expand. Roadside billboards in the area are a voice for citizens who don’t like the noise, dust or truck traffic associated with quarry operations.
In the meantime, the people at Dufferin Aggregates have gone out of their way to be good neighbors. In 2005, the site won the Environmental Achievement Award from the Ontario Stone, Sand & Gravel Association, recognizing it for site reclamation, front-entrance appearance and community relations. In 2006, the Acton site was the recipient of the National Stone, Sand & Gravel Association’s Environmental Excellence Bronze Award and in 2007 the Excellence in Community Relations Silver Award.
With its community in mind, Dufferin Aggregates decided to reduce noise by replacing all of the screen panels at its Acton site – more than 30 of them.
The new screen panels were chosen with the idea of reducing noise emissions to the surrounding neighbors and eliminating the need to enclose the classification screening plant. “"That option would hamper maintenance efforts and it had real cost implications,” McDougall said.
Screen decision
Dufferin Aggregates chose to use synthetic screen panels from Polydeck Screen Corp., and McDougall explained the decision-making process: “What really sold us was the recommendation from our sister company in Massachusetts. We are part of the Holcim Group, as is Aggregate Industries (AI).
“Last summer we hosted some of the site managers from the Northeast Region of AI to tour our plants and they returned the offer last fall. Many of their sites are close to residential areas and they have elected to go with Polydeck as their screen media supplier,” McDougall said.
“After seeing the screens operate, we were convinced they would work well for us. I think it is one of the great success stories of best-practice sharing I’ve been involved with.”
Dennis Zeiger, marketing manager for Polydeck, said, “Dufferin needed a minimum noise reduction of 5 dB to justify making a change. We told them we were confident we could do significantly better than that, and when they brought in an independent lab to check noise levels on the test screen, our media measured 9 dB quieter than their existing wire cloth.”
McDougall added, “Polydeck provided the best price and the best guarantees both in terms of noise reduction and wear life.”
David Ciszczon, Polydeck’s Northeast Region sales manager, said, “After initial discussions, we gathered existing product gradations and equipment specifications in order to make our initial screen panel selections. Then, working closely with Dufferin, we made some screen panel adjustments to hit the customer’s target specifications. What made this project complex and a little more challenging,” Ciszczon added, “was the fact that there were no new machines involved. All decks to be changed out were on existing machines, so each one was configured a little differently.”
Dufferin Aggregates completed the initial trial of the Polydeck screens in November 2007 on one 8-ft. x 20-ft. triple-deck Simplicity screen deck. “We were satisfied with the noise reduction that was achieved,” McDougall said.
The company completed the last conversion in March 2008. In total, 11 screen boxes (more than 30 panels) were converted – the entire plant.
Changeover process
McDougall said there was no downtime during the changeover to Polydeck screens. “The plant has enough flexibility that the classification screens were done on the fly, shutting one down at a time.” He said the remainder of the plant was completed during the site’s maintenance shutdown in March. Sovereign Fusion Inc., a welding contractor, helped with the conversion.
One of the challenges faced during the changeover was remedied by Polydeck. The main scalper screen had been previously outfitted with a punch plate that was custom cut to allow the most amount of openings. The new snap deck resulted in the loss of open area as cross tubes were directly below some of the openings, effectively making them unusable.
“Polydeck stepped up and solved the problem,” McDougall said. “They supplied a new top deck frame that was custom built to give us back 100 percent of our open area.”
The new screens have met all of the company’s expectations. “So far the wear characteristics are great and the plant is much quieter,” McDougall said. “From a health and safety perspective, it is much easier for the workers to change a 1-ft. x 2-ft. foot panel rather than the old, full-size 4-ft. x 8-ft. screens. This has reduced the risk of cuts and strains.”
The new screens have also greatly reduced downtime, which will positively affect Dufferin Aggregates’ bottom line. McDougall said the old screen media was replaced about once a month. He has yet to find out how long the new media lasts, but indications from the company’s other sites suggest it might be a year-and-a-half between changeouts. This would result in a substantial savings on labor and the costs associated with downtime.
Acton
The site is located on the Niagara Escarpment, which is part of the World Biosphere Reserve. An escarpment is a long cliff-like ridge of land and rock, and the Niagara Escarpment – the most prominent in the Great Lakes – runs westward from New York State, through Ontario, Michigan, Wisconsin and Illinois. The escarpment is most famous as the cliff over which the Niagara River plunges to form Niagara Falls.
“We’re also situated in the middle of a water shed divide,” McDougall said. “This means we need to work closely with the Niagara Escarpment Commission, two conservation authorities, the Region of Halton, the Ministry of Natural Resources and the Ministry of the Environment.”
Originally the Acton site was used as a lime quarry. Two original lime kilns remain on site. It became a commercial quarry in the late 1950s and came under Dufferin ownership in 2001.
The plant was completely redesigned in 2002 with only the primary, secondary and tertiary crushing towers left unchanged. “The primary and secondary crushers are original pieces of equipment from the early 1960s,” McDougall said.
The Acton quarry currently operates on one production shift and is budgeted to produce about 2 million tons in 2008. There are 32 hourly workers and 13 office and dispatch personnel.
Drilling and blasting is contracted out, and performed two or three times a week. “Tri-City Equipment is our drill contractor and Orica is our blasting contractor,” McDougall said.
Mobile equipment includes two 990H Cat loaders and a fleet of six 777 Cat haul trucks. Almost all plant repairs are performed in house, according to McDougall. “The mobile equipment is maintained through a total maintenance and repair contract with Toromont and Nortrax.”
All material is stockpiled with conveyors and stackers, and loaded with front-end loaders onto trucks for shipment.
The Acton site has a blend of internal customers – Dufferin Construction and Dufferin Concrete – as well as external customers. “This site focuses primarily on asphalt products,” McDougall said. “And, as a result, we supply many different asphalt customers.”
The site serves a market area of 100 km (about 60 miles) with some specialty products going as far as 700km (about 435 miles). Most product is used in the Toronto metropolitan area.
McDougall said in the past Dufferin produced 22 products between its Milton and Acton sites. Now each site produces about 11, “which has made for much better efficiency.”
The operation produces stone 11 months a year, but shuts down for maintenance in March when everything turns to mud. According to McDougall, it’s much easier to make stone in January or February when it’s bitterly cold and the ground is hard.
Mining is complete on Phase 1 and Phase 2 of the site, and the company has already begun reclamation in those areas, including sloping of banks. When reclamation is completed, the areas will serve the public with a combination of natural water and terrestrial features, as well as recreation areas. .
Polydeck Screen Corp., www.polydeckscreen.com
Good employer, good neighbor
Dufferin Aggregates is a business unit of St Lawrence Cement Inc., a member of the Holcim Group. Based in Concord, Ontario, the company operates six quarries, 13 sand and gravel pits and three distribution yards in the Toronto area and adjacent municipalities.
Site Manager Rob McDougall said, “We have an orientation procedure for new employees, as well as yearly ‘startup training’ for all existing employees.” Topics covered include everything from lockout/tagout, hot work permits, emergency response, and working from heights and confined spaces. “In addition,” McDougall said, “the Ontario government requires all surface miners to complete three core training modules and any job-specific specialty modules that relate to their position.”
As well as caring for its employees, Dufferin Aggregates cares about the community. In an effort to reduce mud tracking, tire-wash systems were installed, and the site has a Cat IT14 utility machine equipped with a hydraulic broom to sweep the road crossings and entrance.
The company is involved with Habitat for Humanity, The United Way and Boy Scouts of Canada. Local initiatives include the Lime Kiln Society and sponsorship of sports teams and events.
“Every year we hold an open house for the public and we host an annual tree-planting day during Earth Week,” McDougall said. More than 50,000 trees have been planted since 2001.
Bearings solution
Dufferin Aggregates’ Acton Quarry had a bearings issue. Bearings used on a counterweight pulley located on a transfer conveyor for wet fines material were in direct contact with water. Occasional misalignment caused the bearings seal to distort, providing an open door for water and contaminants. This resulted in the need for a bearings change every month.
Emerson Power Transmission (EPT) came up with a solution in the form of its SealMaster RPB. The RPB is a self-aligning bearing with elastomeric rubber seals and external rotating flinger. The seals are mounted between the inner and outer race of the bearing and subsequently move with the cartridge insert as misalignment occurs. The seal does not lose effectiveness up to +/-3 degrees of shaft misalignment, according to EPT.
The manufacturer says the RPB has outlasted the old bearings by threefold in this application.
Emerson Power Transmission, www.emerson-ept.com
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