Do the maintenance practices for tires operated in an underground environment versus a surface operation change? The answer is NO.
In fact, more focus needs to be spent on maintaining the haul roads, loading and dumping areas to minimize early tire failure. Generally, in an underground mine operation water is difficult to avoid, which makes cutting of the tires much easier. This is why training both the operators and mine supervisors is more critical; everyone is either part of the problem or part of the solution to improving the overall tire performance.
In this article, I will be focusing on only the high-ceiling, hard rock underground mine operations. These operations generally use pneumatic tires, unlike low-seam coalmines in which the tires are usually filled.
The production equipment generally used in underground operations includes scoops (loaders) and haulage trucks (mostly articulated dumps but sometimes rigid frame). There also are drills and roof bolters in use, and the same principles that we will discuss for the tires on the scoops and haulers will apply to that equipment, as well.
For the most part, once the equipment enters the mine, it will not come back to the surface until the end of its life. That means all the maintenance is done in the underground shop.
Safety is the first priority. Prior to going onto any mine site in the U.S., you must be MSHA certified. Other countries have similar certifications, as well. When going underground, there is a special MSHA training course that you must attend, plus whatever the mine site itself may require. It is important to listen and learn what to do in case there is an emergency.
Although you won’t see as many underground mines in development or in operation as you do open pit, they are out there. And, yes, some of the highest maintenance cost will be tires. This is why application, proper fitment and maintenance are very important.
The main reason for removals is just like surface mines – cuts and impacts. But there are far fewer wear outs, depending on the site’s maintenance.
Underground mine tires generally do not last as long – depending on the operation and its maintenance practices.
What does seem to happen often are “out of sight, out of mind” problems, meaning many of the principles of good tire management change and become more relaxed because the tires become virtually invisible below the surface. For underground mining tires, it is more important to focus on maintenance – getting another month out of a tire can save the mine a lot of money annually.
One of the big problems with tire maintenance underground is “getting it done and done correctly,” according to Jerry Newton, who handles product application and field service for Maxam Tire International.
“When the equipment gets inspected, you will normally see a couple mechanics cleaning or changing the air filters, dropping the oil, greasing, and topping off fluids,” Newton says. “One thing you will hardly ever see the mechanic do is check the air pressure or the condition of the tires. Unless the tire actually looks low, it’s generally ignored by a mechanic.”
One important suggestion is that a run-low tire (less 20 psi from the recommended cold inflation) should never be aired up without first having a trained tire technician inspect and possibly remove the tire to ensure that it has not been run flat. Once inspected and the reason for the tire losing has been air found and addressed, then the tire can be aired and put back into service.
The Right Way
Having a good tire maintenance program in place can save the end-user thousands of dollars each year. As I have discussed in previous articles, you cannot check the air pressure too much.
Get the mine site into the habit of having the equipment operators do routine walk arounds and check tire air pressure while they are checking the oil and performing other pre-shift inspections. After all, air in the tires is like oil in the engine: neither one can operate very long without the proper amount. Also, equipment operators should note any concerns with the tires, like serious cuts in the sidewall and tread, damaged wheel and rim components, and any loose or bent equipment body parts that might damage a tire.
“The routine of checking all four wheel positions will add maybe 10 minutes to the rest of the walk around, unless the operator finds a low tire. At this point, the operator saved the company a lot of money. This is preventive tire maintenance,” Newton says.
To ensure the operator is doing the routine walk-around, he or she should carry a check-off sheet that the supervisor eventually sees. Having the tires added to the pre-shift check-off sheet – and regularly checked – will allow the supervisor to schedule the equipment in for the necessary work.
Tight Spots
Although checking air pressure is a crucial part of maintaining all tires, underground equipment is more susceptible to wheel and rim damage, allowing for air loss. This is due to the harsh, tight conditions in which the equipment operates while mining. The drifts are just wide enough for the machine, and the corners are tight. This means the rim and wheel components will get damaged easily, causing the air to escape from the tire.
You’ll find on underground equipment that the side rings (flange rings) are damaged more often than in any other mining operation. The side ring supports the bead of a tire, which, in return, supports the rest of the tire. When you take this support away, you are damaging a tire, and more than likely it will be removed prematurely and marked as junk.
A lot of times, these removals can be avoided by keeping spare parts on the shelf and making sure any damaged components are replaced and disposed of when removed.
Because underground mining operations run non-stop and most of the maintenance is done in a limited-light environment, little things get missed or left out, like not replacing the valve cap. We all know that the valve cap is the primary air seal. Installing the metal cap on every valve stem hopefully will stop the operator from complaining about having to put air in a low tire every four to five days.
While we are on the subject of sealing the deal, we cannot overlook the O-ring. Remember, “out of sight, out of mind” does not mean you can reuse some of the parts that you would normally toss out. When a tire is changed, be sure to cut and throw away the old O-ring. Taking shortcuts to save money will cost a lot more to the customer in the future. Every time a lock ring is removed and reinstalled, a new O-ring should be installed.
In my mind, walking the area in which the equipment will be operating is more important with an underground mine than with a surface mine. As stated earlier, in underground conditions, water is just as natural as rocks and must be addressed to reduce tire cutting.
Grading is important, but many times overlooked. Filling in the ruts and reducing the water and loose rocks will make a major difference in the life of a tire, whether on the scoop or haulage vehicle. Besides saving the tire, the operator will be more productive and much more comfortable.
The last area to examine is the tire service bay. Make sure it is clean and well-lighted. This will ensure the tire and wheel/rim components can be properly inspected.
As a side note, it is very important for the tire technician to dual inflate the tires. With the beads being so wide and strong, they’re more difficult to properly seat on the rim. This often is overlooked and can affect the performance of the tires.
Just like surface mining, you should do a mine site inspection report for underground mine customers. The information you share with the mine customer will be very beneficial, with major returns coming much faster.
There is more to tire and site maintenance than what we have discussed here. The way I like to look at it is: you can never say too much or too little about maintenance.
The good thing about maintenance is it pays off. Get tire technicians, equipment operators and site supervisors involved and make them responsible. If everyone is doing their part, then downtime and tire costs can be cut drastically.
