June 1, 2011
Careful attention to haul truck tire inspection and maintenance can prevent catastrophic tire failures.
As part of an overall commitment to safety, quarries need to take a proactive approach to haul truck tire inspection and care. Truck tires are subject to tremendous stresses due to heat, sidewall flexing, torque loads, and, of course, the heavy loads carried by the trucks from the face to the crusher. Rocks on the haul road can easily cause sidewall or face cuts that can lead to catastrophic tire failures — which can endanger ground personnel, cause problems with controlling the truck, and may result in hours of unplanned downtime and lost production.
To help ensure the safety of everyone in the quarry and maintain productivity, a proactive program of tire inspection and care is a must. Prior to operating a haul truck, operators should inspect each tire and check the tread for missing chunks of rubber or embedded objects. They should also check tire sidewalls for any cuts or gouges.
In 2010, the root cause of 4 fatalities in stone surface and milling operations was attributed to powered haulage.
In particular, front tires should be inspected to ensure they are in excellent condition, because they are used to control the truck. The rear of the truck has dual tires on each side; if one of them fails, the operator can still drive the truck back to the shop for maintenance. If one of the front tires fails, however, there is no backup. For this reason, quarries and mines usually rotate tires to the rear of the truck after they are worn 30 to 50 percent, and a new set of tires is placed on the front of the truck.
The haul truck operator must take responsibility to ensure that the tires of his or her haul truck are always properly inflated. Tires can only deliver optimum performance when they are properly inflated; low pressure will cause them to be more susceptible to damage. A bulge at the base of the tire usually indicates low tire pressure.
Proper tire care leads to increased safety and profits
Considering the high cost of haul truck tires today, launching a training program to extend their life is like money in the bank — it goes straight to the bottom line as cost savings. Following are some of the most common threats to haul truck tires and some practical operator strategies that may extend their life.
Haul truck driver responsibilities
The operator of a haul truck is the person most responsible for tire care and safety. Here are some of the most common tire hazards that haul truck operators may encounter and how to avoid them:
Berms: Avoid contact with berms and steep bank faces, which can place excessive stresses on tire sidewalls and may hide other threats, such as embedded rocks or pieces of steel.
Tire flexing: Keep a careful watch for washboard sections of the haul road, which can cause a significant amount of tire flexing. On a fully-loaded haul truck, this flexing can seriously damage tires. Most often, this type of damage is not immediately noticeable. Rather, it is cumulative and may result in sudden tire failure. Slow down on rough sections of haul road to reduce tire wear and stress.
Rocks and spillage: Material in the road must not be ignored, but rather be dealt with immediately. Shot rock can often have sharp edges that can slice through the tread or sidewall of the tire. Go around the hazard, and call the dispatcher or the operator of a nearby piece of support equipment to have it removed at once.
Dump pocket hazards: Haul truck operators must do everything they can to avoid making direct contact with concrete bumper blocks at the back of dump pockets. These back stops can severely shorten tire life. When backing up to a crusher, make sure there is no spillage in the pocket that the truck will either back over or sit directly upon while dumping its load.
Windrows: Straddling windrows can be unavoidable. Make efforts to stay on one side or the other, when conditions allow. If you must cross over a windrow, look for a spot that appears to have the least risk of hazardous material. If you are meeting a loaded haul truck that is straddling a windrow, do what you can to assist the operator in avoiding hazardous conditions. Be prepared to yield or stop until they are in the clear.
Wheel loader operator responsibilities
Wheel loader operators have a significant contribution to the way in which haul trucks and their tires perform. The truck has to deal with and haul the load as loaded by the wheel loader operator. In addition, the loader operator must maintain a clean loading area. He or she needs to balance the requirements of safety, productivity, and tire hazard control when loading trucks.
If there is water on the floor of the pit where trucks are being loaded, it could hide tire hazards such as submerged rocks. Tires cut up to 50 percent more easily when they are wet. When possible, de-water loading pits to ensure that trucks and other rubber-tired machinery can operate safely.
Three major issues for wheel loader operators loading haul trucks include the following:
Tire damage hazards while trucks are backing in and loading. The loader operator is responsible for maintaining a safe and productive loading area. The loading zone must be clear and free of material that could cause tire damage. Loader operators should operate smoothly and consistently throughout their work cycle to minimize spillage of aggregate over the sides and back of the bucket.
The position of the truck while being loaded. Position trucks to maintain loading productivity and avoid any spilled material. Truck tires should never come to a stop on the toe of the rock wall or on top of any shot rock. The truck operator should pull forward until the truck is level.
The size, shape, position, and total weight of the load. The wheel loader’s biggest contribution to tire life is the consistent production of optimum loads. Haul trucks are designed, built, and optimized to haul a load of specified weight. Loads should be evenly distributed in the truck’s dump bed. Trucks should never be loaded beyond their rated capacity, as this places extra stress on the tires and other truck components. Avoid overloading at all costs.
The bottom line
A proactive tire inspection and care program can not only help to ensure the safety of your haul truck operators and ground personnel, it can also help you get more life out of these expensive assets. Identifying and mitigating truck tire hazards in the quarry can also help you keep your truck fleet productive and significantly reduce or eliminate one significant source of unplanned downtime. AM
Article courtesy of VISTA Training Inc.
Best Practices for Haulage Equipment Operators
If you can answer “yes” to the following questions, chances are you will leave work today without having an accident.
Approach the machine safely?
Maintain three points of contact (two hands and one foot or two feet and one hand) while mounting or dismounting?
Use a drop rope to raise and lower personal items or supplies?
Perform a pre-operational check of the machine?
Report unsafe conditions?
Faithfully wear your seat belt?
Sound horn or other warning device before starting or moving the machine?
Visually check the machine for people or equipment prior to moving?
Follow traffic control signs?
Use personal protective safety equipment?
Properly park the machine a safe distance from other machines?
Clean the cab and windows?
Have a portable light after dark?
Operate the machine at a safe speed?
Fill out an equipment operator shift report?
Source: U.S. Department of Labor, Mine Safety and Health Administration
Becoming More Aware of Tire and Rim Problems
Proper operation, maintenance, and tier selection can increase the life of a tire and rim.
General problems that may affect tire and rim safety:
Improper operator practice;
Excessive haul speed;
Improper tire and rim maintenance;
Over-inflation of tires;
Under-inflation of tires;
Improper tire repair;
Cutting of tread by sharp/hard objects; and
Improper tire selection.
Haul road problems that may affect tire and rim safety:
Tire ply separation could occur if reduced speed limits are not in effect on curved or rugged terrain.
Internal friction could occur at high speeds on rough terrain causing heat wear on tires.
Poorly drained roads can cause depressions in roads — cutting, bruising, or bursting tires and denting or cracking rims.
Poorly maintained roads, especially in wet weather, can cause slippage or spinning, which, in turn, cuts and rapidly wears a tire.
On excessively rocky roads, tires and rims can become damaged unless tire protection chains are used.
Vehicle operator problems that may affect tire and rim safety:
Driving at excessive speeds on poor road conditions;
Spins and slippage;
Fast stops, fast starts, fast turns, and excessive loads;
Tires allowed to rub against the banks of haul roads or guard rails; and
Excessive breaking, which could cause deterioration of the tire beads and inner liner.
Repair and maintenance problems that may affect the tire and rim safety:
Tires allowed to rub against part of the vehicle;
Under-inflation of the tires;
Over-inflation of the tires (beyond recommended inflation chart);
Stones allowed to remain caught or wedged between dual tires;
New tires being mounted beside worn tires;
Mismatching of tires;
Promoting wear of tires by parking in gasoline or oil puddles; and
Uneven brakes, poorly aligned wheels, wheels that are wobbly or bent, or bent axles.
Source: U.S. Department of Labor, Mine Safety and Health Administration
The Small Mine Office developed a series of weekly ToolBox talks that can be used by small mine operators and others to hold safety and health discussions for their employees at their mining operations. These ToolBox talks were developed in consultation with members of the mining community. To get the free app, enter http://gettag.mobi into your browser.