June/July 2011

Pulling out the stops

Siemens and Quadra FNX avoid downtime as they upgrade mill drive

By Alexandra Lopez-Pacheco

A crane sets into place the portable building that accommodates the new electronics. The plant will use the “e-house” while the obsolete technology is phased out | Photo courtesy of Siemens

Some six years ago, Canadian mining company Quadra FNX Mining Ltd. realized it could be facing a serious problem in the not-too-distant future with its semi-autogenous grinding (SAG) mill at its Robinson open pit copper mine near Ruth, Nevada.

“The equipment we had was late 1980s and early 1990s technology,” says Cary Brunson, maintenance manager, Robinson Nevada Mining Company. “And the computerized portion of this had become obsolete. We recognized the short supply of the components we needed to maintain the equipment. If we shut down because we were out of parts, it would cost us up in the $50,000 an hour range. If we had to shut down because we didn’t have the part on site and that part was already obsolete, we could be facing weeks to get it repaired or get a new one. It became apparent that the cost of trying to operate on an obsolete system was going to be prohibitive.”

So two years ago, the management team at Robinson decided that this year, it would upgrade the mill, which employs Siemens’ Simine Mill GD solution for gearless mill drives and twin-pinion mills. But that decision did not come without its own challenge since the upgrade work itself would likely require a significant and costly shutdown. That’s when Siemens Industry, Inc. came into the picture.

“We did an evaluation as to what the recommended upgrade would be,” says Vinny Matthews, business manager, mining projects, Siemens. “And what we were able to figure out is that we could upgrade all the power conversion, electronics and automation without having to replace the motors, which are extremely large, very expensive and are very time-consuming to replace with new ones. Fortunately, Siemens has always built an extremely robust motor. For Robinson, that was a feasible alternative because it greatly reduced the shutdown period that would be required.”

While this solution did indeed dramatically reduce the necessary shutdown period, the challenge of how to do the upgrades, which included a Sinamics SL150 cycloconverter and a new diagnostics system, with the shortest possible interruption to production remained critical.

Small windows of time

“We have two opportunities a year to have this mill down for the amount of time we need to do the upgrade and, logistically, we had to have this set up so we can do the upgrade within those two periods,” says Brunson. “Siemens has worked very well with us on this and been very flexible. Instead of taking all the downtime they need to do to get this up and running, they’ve broken it down. We have a 14-hour shutdown every five weeks, so they’re coming in and doing bits of what needs to be done within those windows.”

While not replacing the motors was part of the solution, it also presented its own challenges. “We were looking at putting the new section in while the old one was still running to limit the shutdown period,” says Matthews. “As well, it would allow us to test the new one as much as possible without connecting the motors prior to converting the entire system. But we looked at this and thought, ‘Where are we going to put all these electronics?’ Typically, you take out the old and replace it with the new.”

The mine operators and the Siemens team decided on what was to become one of the more unique and innovative aspects of this project. “We built a platform outside of the building, which would connect to the existing concentrators so there would be a shared wall, and then put in an e-house, essentially a portable building that houses electronic equipment, on that platform,” Matthews explains.

The e-house was built in Indiana. There, all the equipment was installed in the e-house and tested. “Because the e-house is too big to ship in on one flatbed, you typically split it in half or thirds, or more than that, and then you truck it to the site,” he adds. “You lift it up with cranes onto the platform and put in place.”

“Despite the cost,” says Brunson, “we did our analysis and realized that the cost of even a day’s time of being down would match the price for this upgrade, so it became a very easy decision.”

Greater performance with a smaller profile

Throughout this phase of the project in the summer of 2011, the existing equipment continues to operate, while Siemens focuses on the installation of the e-house and the wiring work, as well as much of the automation testing. Sometime in September, depending on the feasibility for Robinson, the mine is expected to shut down for approximately four days, during which time the new system will be fully connected to the existing motors and thoroughly tested.

“We expect several types of performance improvements for Robinson with the upgrade,” says Matthews. “That includes a smaller electronics footprint, which means the number of components tend to be reduced, and when the number of components are reduced, the reliability tends to increase. Instead of having lots of electronics, which is typical with analog, this is primarily a digital system. That means we’re able to control everything much more precisely and the diagnostics are greatly improved. The power performance has also improved significantly over the years, so they’ll be able to do the same amount of work with less energy. Furthermore, the user interface has become much friendlier. Today, it’s basically point and click. It allows the operators to get a lot more information and higher productivity with the system.”

In addition, the mine operators won’t have to worry about an unexpected shutdown due to a broken, obsolete part. With many mines in North America using equipment that is two or more decades old, Siemens says it is seeing an increased demand for innovative solutions for upgrades such as this one that limit the need for shutdowns. “We specialize in this,” says Matthews. “We were kind of driven this way by the recession. Several years ago, everyone was very concerned about the amount of investment they could make, yet they still needed to make the investment because they had to have the equipment going. So we started to look at how we could modernize the mills for our customers without a massive amount of capital being expended and without them having to shut down their production for a prolonged period. This is what drove this type of innovation, which has in turn become a value proposition.”

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