After almost 30 years of utilization, a North-American Silver- and Gold-Mine took action together with specialists of Martin Engineering to update its conveyor system with improvements regarding safety, spillage reduction, endurance and efficiency.
Coeur Mining, Inc. is the largest primary silver producer in the nation and a significant gold producer, with three wholly-owned operations in North America and two in Latin America. Incorporated in 1928, the firm currently employs around 2,000 people. The firm’s business strategy is to develop and operate low-cost silver and gold operations that will produce long-term cash flow and generate sustainable returns, nevertheless operating with a deep commitment to its code of corporate responsibility to employees, contractors, communities and the environment.
“Our primary commitment to employees and contractors is to protect their health and safety,” said Coeur President and CEO Mitchell Krebs. “Safety programming and management systems are continuously reviewed and improved to provide the training and tools necessary to prevent accidents, injuries and occupational illnesses.” The result in the facility’s safety record: more than six years and counting without a single lost-time injury (LTI).
The company’s Rochester mine and associated heap leach facilities are located in Pershing County, Nevada and produced 4.6 million ounces of silver in 2015, along with 52 588 ounces of gold, and the firm estimates and expected yield of nearly 4.8 - 5.3 million ounces of silver and more than 48 000 - 55 000 ounces of gold in 2016.
Coeur Rochester produced 4.6 million ounces of silver in 2015, along with 42,588 ounces of gold
As part of that commitment of corporate responsibility and continuous improvement, Coeur Rochester undertook a comprehensive review of its bulk material handling processes. The massive Rochester site is spread over 10 800 acres (43.7 square kilometers), and includes a network of 20 conveyors, originally designed and installed in 1986. Therefore, company officials began considering ways to update the conveyors with leading-edge technology to raise efficiency, reduce dust and spillage, and contribute further to safety.
Coeur managers initiated discussions with Hardrok Equipment, a trusted supplier with a history of more than 40 years of combined experience in maintaining and optimizing crushing, conveying and screening operations. After a thorough review of the entire conveyor network, followed a series of five training sessions to review the issues and the technologies available to resolve them. As Hardrok is a licensed dealer of Martin Engineering conveyor products, much of the discussion revolved around the company’s EVO conveyor architecture, a literal reinventing of the conventional design approach for conveyors.
“We’ve always operated under the belief that high-quality products and services cost less per ton over the life of the product,” observed Hardrok President Ted Zebroski. “With proper design, premium components should improve productivity and safety, and that greater efficiency delivers a lower total cost of ownership.”
He adds: “In the construction phase most conveyor systems have been specified by determining the capacity and meeting the minimum codes and safety requirements, with a focus on the lowest construction cost, whereas Martin’s EVO approach examines every detail to make conveyors safer, more productive and better able to contain fugitive material for new installations as well as retrofitting existing ones.”
Proposals for Improving the Situation
Conveyor B was chosen as the starting point with the most potential for improvement, a 48-inch (122 cm) wide belt running at 386 FPM (1.95 m/s), with a 40-foot (12.2 m) chute wall. With a troughing angle of 35°, conveyor B handles nearly 1500 tph of rock that has been sized to 4-inch (10.2 cm) minus, carrying it from the secondary cone crusher to the surge pile stacker. It’s loaded directly by a vibrating grizzly feeder under the chute and the secondary crusher.