February 1, 2011
Operating and maintenance techniques can extend undercarriage life.
By Tom Nenne
Steel tracks are designed to perform in tough underfoot conditions, but long hours in wet, muddy, slippery, rocky, or abrasive materials can translate into rapid wear and high repair costs. The undercarriage on a large dozer can account for 50 percent of the repair and maintenance costs for the machine — even when the operator and maintenance personnel use best practices.
Abrasive wear is the primary type of wear experienced by undercarriages, which is impossible to avoid in aggregates operations. But the operator can take a number of steps to maximize service life and drive down operating costs, and service personnel can ensure that undercarriages don’t experience excessive wear due to maladjustment. Frequent and proper inspections also can avert premature failures, which result from little problems growing into big ones.
Long before your dozer or excavator goes to work, you will make decisions that influence undercarriage wear and subsequent maintenance costs. A number of different track designs are available now. Though the most wear resistant have higher initial cost, selecting such an undercarriage often results in lower life-cycle costs. Generally speaking, the more you work in high-horsepower, high-torque applications, the faster your undercarriage will wear. Work with your equipment dealer to select the undercarriage design that is best suited to your site conditions and application.
One rule of thumb applies to all undercarriage designs, however. Always use the narrowest track shoe possible that meets your flotation requirements. Wide shoes operating on hard surfaces put tremendous strain on the shoes, pins, and bushings. The result is accelerated wear.
Also, if you work in very sticky materials, consider using center-punched track shoes to reduce material packing in the undercarriage area when specifying undercarriages. To further limit material packing and debris buildup, use roller guards only when necessary. They’re designed for high-impact underfoot conditions.
Tips to extend undercarriage life
1. Start every shift with a clean undercarriage. When mud and debris build up on the lower part of your machine, components wear at a faster rate, so don’t begin work until the undercarriage area is clean. If a cleanup didn’t happen at the end of the previous shift, take a few minutes to get the job done before you go to work. And if you’re operating in very cohesive or abrasive materials such as mud or clay, you may need to clean the undercarriage more than once during a shift.
2. Inspect the undercarriage before you start working. In addition to ensuring that the undercarriage is clean, spend a couple of minutes on a visual inspection. Check for loose bolts, leaky seals, and abnormal wear patterns. When you spot potential problems early, you can often prevent them from turning into bigger issues that significantly reduce component life or cause unscheduled downtime.
3. Don’t spin the tracks. Track spinning delivers several hits to the bottom line. It reduces production, so your revenue potential declines. It increases fuel consumption, without a corresponding increase in productivity. And, it accelerates undercarriage wear, so your costs escalate. Grouser bars are especially prone to wear problems associated with track slippage.
Tight track is the number one track killer.
4. Watch your speed. There are times when a task requires higher speed operation, but wear accelerates as speed increases. Links, rollers, and idlers are particularly vulnerable. Keep them working longer by controlling your speed. The mantra for dozer operators to achieve maximum productivity in production dozing is: Big load, slow.
5. Avoid unnecessary reverse operation. Operating in reverse, even at slow speeds, compounds bushing and sprocket wear. So don’t run in reverse unless you have to. To avoid spending more time in reverse than necessary, aim for pushing large loads in first gear.
6. Alternate turning directions. If you’re always turning in the same direction, the undercarriage components on one side of the machine will wear at a different rate than those on the other side. More specifically, turning left all the time accelerates wear on the right side and vice versa. To ensure even wear, pay attention to the way you’re turning and change directions when possible.
7. Work up or down a slope whenever possible. Working across a slope can shorten undercarriage component life, so try to structure the job with minimal cross-slope activity. Also, dozing downhill achieves greater production with less fuel burn by using gravity to your advantage.
8. Avoid galling. Galling is caused by loss of lubricant between pins and bushings in the track caused by excessive pressure pushing oil past the seals. A combination of excessive load and speed, running track tighter than specified, packing conditions, and the practice of “mud flinging” all can cause galling. Mud flinging involves raising the dozer up with the ripper and blade and rotating the tracks.
9. Always dig over the front idlers to reduce the potential for structural problems. Specific to excavator operators, never dig over the final drive, and never dig over the side of the machine.
Maintenance means inspection, tensioning, cleaning
Maintenance discipline plays a big role in undercarriage component life. Conduct a visual inspection daily or when underfoot conditions change significantly. Check track adjustment; check for oil leaks on links, rollers, and idlers; and look for broken or loose undercarriage components and excessive gaps between track shoes.
One of the most critical maintenance practices is track adjustment. Tight track is the number one track killer, but whether your track is too loose or too tight, improper adjustment accelerates wear. Follow the manufacturer’s recommendations for track adjustment, and always perform the adjustment in the machine’s working environment.
As noted earlier, cleaning the undercarriage maximizes wear life. The task may be the operator’s duty or it may be the duty of maintenance personnel. Regardless, remove mud and debris at the end of every shift, or more frequently if necessary.
Many aggregates operations rely on their equipment dealer to periodically inspect and measure undercarriages. For example, the Cat Custom Track Service provides reports with maintenance and repair alternatives that the aggregates operation can select to achieve lowest cost of operation.
Getting the most from your dozer and excavator undercarriages is a matter of good operating techniques and diligent maintenance attention. Doing that right means longer lives for your undercarriages and lower costs for your mine. AM
Tom Nenne is senior product support consultant, Caterpillar Inc.