November 17, 2017
Dozers are workhorses on an aggregate site, so optimizing production while minimizing downtime is a huge priority. Last year, U.S. domestic production and use of construction aggregates amounted to 2.5 billion short tons of crushed stone, sand, and gravel. That values the industry at $25.1 billion, according to the National Stone, Sand & Gravel Association (NSSGA). Yet, despite its size, by and large, aggregates is a high-volume, low-margin business, so owners need to get the most out of their machines and equipment.
The number one maintenance issue for dozers is damage to the undercarriage, because of the large quantity of relatively expensive parts involved and high utilization every time the dozer is travelling. Abrasive sandy soils — the bread and butter of the aggregates industry — accelerate undercarriage wear.
Although a crawler undercarriage typically accounts for 20 percent of a dozer’s purchase price, it commonly racks up 50 percent (or more) of its lifetime repair tab. The undercarriage of a dozer suffers more force, sliding, and abrasion than any other piece of equipment. And that’s a lot of money tied to one component.
With such large potential repair expenses at stake, keeping the undercarriage in good working condition can significantly minimize repair expenses and lower per-hour operating costs. But, when you figure in 10-hour days, high duty-cycles, and unforgiving terrain, maintaining uptime gets trickier.
Undercarriage management has been described as part science and part intuition — all refined by experience. It encompasses everything to do with machine operation, routine maintenance, periodic evaluation, and, sometimes, even decisions about how best to handle wearing components.
But, ignore undercarriage management at your peril, because the costs quickly escalate.
Good design helps mitigate maintenance
One way to reduce undercarriage wear is to invest in a premium undercarriage, which is designed to reduce wear, specifically external wear on the bushing. A rotating bushing undercarriage can extend life by a factor of two or more in abrasive soils by eliminating sliding and scuffing between the dry bushing outer surface and sprocket tooth. The rotating bushing stays fixed in place on the sprocket tooth, and all sliding takes place on an oil-filled surface between the bushing inner surface and the track pin. Because a pin and bushing turn is not required, this eliminates a large maintenance expense and costly machine downtime.
Oval shaped undercarriages are designed with fewer components than a high drive, which can lower replacement cost. With more track wrap at sprocket, the load on each bushing is reduced, because twice the number of bushings transfers the load from the sprocket to the track. Track links and rollers are sized so the entire undercarriage system wears equally. Also, self-adjusting front idlers reduce maintenance cost, since shimming is not required.
Some dozers offer other design features to help minimize maintenance. Castings at high stress areas of the dozer assembly are stronger and distribute stresses better than fabricated brackets, therefore weld repairs are infrequent. Well-routed and supported hydraulic hoses and wire harnesses help minimize maintenance by reducing movement and rubbing that can lead to leakage and breakage. Finally, ground-level, ease-of-access for routine maintenance, without the need to remove adjacent components, is important.
Other design features that can reduce maintenance include air pre-cleaners mounted upstream from the engine and cab filters that extend filter life in dusty environments.
Additionally, there are features on dozers to limit operations that accelerate undercarriage wear. For example, the machine monitor can be programmed to limit reverse travel speed, which is important because undercarriage wear is worse when the machine reverses, and excessive speed accelerates that wear.
It cannot be said enough: Be proactive with all maintenance issues. It’s simply the best way to prevent a small problem from turning into an expensive major maintenance headache. Use an oil sampling and wear analysis program regularly to monitor machine component health.
Proactive undercarriage management begins with good operating and maintenance practices. That includes avoiding — as much as is practically possible — high ground speeds, excessive reverse operation, counter-rotation, track spinning, and same-direction turning on large jobs. Good maintenance ranges from shoveling out the tracks daily and frequently checking track tension to periodically measuring wear and making informed decisions based on the results.
The small stuff counts
All too often, it’s the small stuff that can trip up an operator. Daily maintenance and upkeep is critical to overall machine health. The undercarriage of a dozer is built on a system of moving components: rollers, idlers, tracks, and other parts.
An ounce of prevention is worth a pound of cure
A complete undercarriage inspection should be done daily based on the OEM’s recommendations and guidelines. Inspect the undercarriage for excessive or uneven wear, as well as damaged or missing components. Any issues should be immediately addressed to minimize further wear or damage.
No excuses: Clean everything
On many dozers, a shovel for cleaning the tracks is mounted right to the machine. Make use of it, because a clean undercarriage is a healthy undercarriage! At the end of the day, mud and debris should be cleaned out and removed from the undercarriage. Built-up dirt accelerates component wear. Cleaning at the end of the day removes any material that could freeze, harden, or dry up overnight.
Secondary maintenance concerns include air filters, fuel filters, diesel exhaust fluid (DEF) cleanliness, and ground engaging tools. Dusty air can plug air filters, and contaminated DEF fluid can plug the injector. Operators should empty air filter pre-cleaners and keep cab doors closed when dozing. Each time fuel filters are replaced, install them dry and use the fuel priming pump to assure all fuel flowing to the engine is filtered. Drain any water that has accumulated in the fuel water separator.
Track the tension
It’s imperative that operators monitor track tension under actual working conditions. Tracks that are too tight accelerate bushing wear. And tracks that are too loose can create instability or even cause the tracks to derail. Refer to the operator’s manual for specific track inspection and tensioning procedures.
Operate machine correctly
The way a dozer is operated also plays a critical role in the health of the undercarriage. To that end, there are some important operating tips that can minimize wear and maximize productivity.
Proper turning contributes significantly to minimizing wear. Operators should be trained to make wide and gradual or Y-turns when possible, because counter-rotation and pivot turns accelerate wear. Alternating turning direction is also important because making continuous turns in the same direction can cause asymmetrical and accelerated wear. Operators should focus on balancing the direction of turns throughout the day. If that’s not possible, then check for wear — and expect it — more often.
It’s also important to limit high-speed and reverse travel. Higher speeds cause more wear, and the same is true for unnecessary travel in reverse. Unproductive high speeds should be minimized, and excessive travel in reverse should be avoided at all costs.
Telematics are everyone’s friend
Telematics systems can be very helpful with maintenance. Good systems report working time versus idle time, and periodic undercarriage measurement can be scheduled based on actual working hours (not hour-meter readings). Additionally, if the system also reports forward-travel time and reverse-travel time, it makes it far easier to keep an eye on the excessive wear reverse travel can wreak. For example, if the reverse operation reading seems excessive, then the operation might need to be revamped to ease stress on the undercarriage, or it could mean that the operators require more training.
Good telematics systems keep everyone informed — from owners to fleet managers to operators and distributors (and their technicians) — about the health of the machine and when scheduled maintenance is due. Telematics can be particularly impactful when it comes to preventive maintenance, operator training, and fleet management.
Complimentary maintenance programs
Finally, take advantage of OEM complimentary maintenance programs. Most programs are for a specific amount of time (say, three years) or a number of work hours, whichever comes first. Specifics will vary based on the OEM, but could include complimentary scheduled engine maintenance and complimentary Diesel Particulate Filter exchanges in the first five years.
The primary benefit of a complimentary maintenance program is that it lowers ownership costs, raises resale value, and improves equipment uptime and availability. And that leads to better productivity on an agg site.