The history of copper mining in this country over the past 25 years has been well documented. During the 1960s the industry in the U.S. was inefficient, starved for capital investment and in need of new technology. Copper companies were getting their major revenues from foreign high-grade ore bodies. Then the nationalization of mines in Africa and Latin America forced the companies to re-examine the efficiency and economic viability of their low-grade mines in the U.S. when competing against foreign producers. By 1980, depressed prices and a plethora of costly environmental regulations combined with aging technology were putting an unprecedented strain on the industry.
With this as the backdrop, the San Manuel operations, located in Arizona, had to improve profitability and systematically reduce costs or suffer the consequences. That was 10 years ago. Today, the company has undergone a transformation and a revitalization that would be the envy of any major business. In the period from 1988 to today, the mine has realized an increase in productivity and a cultural revolution.
One of the ways that mine personnel looked to improve profitability was to increase machine productivity by eliminating unscheduled downtime. To do this, maintenance and production personnel needed to work together more closely, and take a proactive approach toward machinery maintenance and repairs.
”This wasn't an overnight transformation,” said Floyd LeGrand, Group Leader for Hoist Systems. “In the past we ran our machinery to failure, which is an expensive way to do business – especially when you have a catastrophic failure.”
LeGrand went on to describe different aspects of the mine's current maintenance program. “We rely heavily on training,” he said. And that, according to LeGrand, is one of the key services that Matt Yeknik (the SKF mining specialist) has been able to provide as part of the SKF Trouble-Free Operation™ program.
”Over the past couple of years we've had a number of seminars on bearing maintenance and care,” said LeGrand. “We've also had seminars on vibration analysis and oil analysis.” He added that those seminars have been a key factor in the mine's maintenance program.
”We've only had one real scare at the mine in recent memory,” said LeGrand. “And that's when there was a problem with number 3D hoist (also called 3-Dog) that supports the 34-40 level (34-40 indicates that the mine is at 3,440 foot level). According to LeGrand, 3-Dog was the only hoist that serviced that level at that time. Today, hoists 3A and 3C also service the 34-40 level.
More importantly, however, the 34-40 level is the site of the “Lower Kalamazoo” project. The Lower Kalamazoo mineral zone is the displaced half of the San Manuel underground ore body that has been mined since 1954. The Lower Kalamazoo is an ore reserve that contains more than 2 billion pounds of copper. It is about the same grade ore as the San Manuel mine, but is deeper and less accessible. To get to the reserve, miners bored a 15-foot diameter tunnel more than six miles. When developed, the Lower Kalamazoo ore body will extend the current underground mining operations at San Manuel an additional nine years.
”There's a lot riding on the success of that project,” said LeGrand. “So when we heard a clicking noise coming from one of the bearings that supports the double drum hoist shaft on 3-Dog, we were very concerned. We shut down immediately, knowing that 3-Dog would have to stay down until we could identify the source.” He continued, “We couldn't afford to stop production and we couldn't afford a catastrophic failure. We needed answers.”
”The maintenance crew had just changed oil in the bearing housing,” said Jerry Dougan, Supervisor of Crusher Maintenance and resident bearing expert. “And the oil was black. We knew there was a problem – we just hadn't determined the cause.”
That's when Dougan headed for a phone to call Matt Yeknik, SKF Mining Specialist. “Matt was working on site with one of our other departments, so when I saw him walking down the hall, I was able to get him right in there to work on the problem,” said Dougan.
A quick inspection revealed that the inner ring had cracked on a 630mm tapered bore spherical. The task at that point was to get the old bearing out and a new bearing in place as quickly as possible. “Within 24 hours the new bearing was in place,” said Dougan. “Fortunately, our guys had been through training and knew that there was a problem. Otherwise, we could have had the type of failure that could have closed the Kalamazoo project.”
”This type of thing isn't new to SKF specialists,” said Mike Loose, Director of Industrial Services. “We have documented cases all over the country where training has been key to diverting bearing failures. In this case, the price of training was relatively small compared to the effects that a catastrophic failure could have caused.” He added, “We're just happy that in some small way we were able to help.”