Wheel chocks for vehicles in mines
Learn the legal requirements and best practices regarding wheel chocks for vehicles in mines.
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This guideline was developed for workplace parties to assist with understanding the requirements in Regulation 854 – Mines and Mining Plants under the Occupational Health and Safety Act (OHSA) for using wheel chocks to prevent undesired movement of motor vehicles at both surface and underground mines.
This resource does not replace the Occupational Health and Safety Act (OHSA) and its regulations and should not be used as or considered legal advice. Health and safety inspectors apply and enforce these laws based on the facts they find in the workplace.
- To provide information regarding the use of wheel chocks to prevent inadvertent vehicle movement in both surface and underground mines.
- To minimize worker injuries due to inadvertent movement of vehicles left unattended on slopes, or during maintenance and repair.
Section 107 of Regulation 854 under the OHSA covers the important requirements.
Regulation 854 defines "motor vehicle" to include a car, caterpillar-tracked vehicle, truck, tractor and motor vehicle running on rails, but not a locomotive.
Although not defined in the regulation, a slope is usually the same as "grade" or "incline," and is considered to include any location where a motor vehicle could roll away if the brakes were not applied. Personnel vehicles are easier to immobilize, with or without wheel chocks. In situations where it is hard to judge whether a vehicle could roll away, wheel chocks or other means should be used.
Two of the three independent braking systems on a vehicle that is driven on ramps cannot operate when an operator is not at the controls. Parking brake systems on unattended vehicles have failed in the past in Ontario. Brakes on mining vehicles work very hard and are high-maintenance items.
A study of 96 runaway underground motor vehicle accidents in the period 1985 to 1993 showed that 21 (36 per cent) of the 58 accidents where a brake failure had occurred involved failures in the parking brake system. A runaway vehicle on a slope can hit other vehicles or persons and cause serious injuries and damage. Inappropriately-designed wheel chocks have failed on large vehicles.
The requirements in section 107 apply to “a mine.” This means section 107 applies to both an underground or a surface mine, but not to a smelter, plant, refinery, etc. A surface mine is a pit or quarry where material is removed for use but does not include a highway or railway rock-cuts.
Suitable wheel chocks
Wheel chocks should be sized and designed to prevent the motor vehicle from rolling over the chock on the steepest slope in its area of operation. Section 107 (1) requires that a motor vehicle in a mine be equipped with wheel chocks that comply with the Society of Automotive Engineers Standard (SAE) J348 JUN90 "Wheel Chocks".
An appropriately sized and designed wheel chock will keep the particular vehicle immobilized on the steepest ramp that the vehicle is required to travel in the mine. The likelihood of a large vehicle failing the parking brake or wheel chock is much greater than a smaller personnel vehicle due to its weight. A 6-yard scoop weighs at least 15 times more than a personnel vehicle. Because of this, suitable wheel chocks should always be used, or other means taken to immobilize the vehicle.
Careful testing and documenting of the suitability of a wheel chock should be completed for each type of vehicle. The conclusions of this testing and documentation should be used to develop written wheel chock procedures. Use of inappropriately designed or sized wheel chocks may result in worker injury and property damage.
When dealing with loaded haul trucks, note that these vehicles may require stabilization using another vehicle as well as a wheel chock in order to ensure adequate immobilization.
For haulage and drilling equipment used at large open pit mines, the presence of extensive ramps should dictate the use and carrying of wheel chocks or other means of immobilizing the vehicle to enable parking unattended on a slope in case of breakdown. In gravel pits and quarries, the distinction between flat and sloped roadways is apparent. The more common types of equipment on surface include loaders (which have a bucket that can immobilize the vehicle on flat terrain) and haulage trucks that travel on highways.
For underground mines, it is common and practical for all motor vehicles to carry suitable wheel chocks, where operation on ramps is usually a normal occurrence. However, other means of immobilizing some vehicles may exist.
Means other than wheel chocks
Alternative means of blocking vehicle movement may be used if they are developed by the employer in consultation with the Joint Health and Safety Committee (JHSC) or health and safety representative.
Other means of immobilizing some vehicles may include turning the wheels toward and touching the bumper of the downward end of the vehicle against a rock wall. This process is only effective on an obvious slope (so as to positively identify which way is down). Using this approach with a vehicle with a bucket (where the vehicle bucket is lowered to the ground and faces down slope so the bucket contacts the wall and the front part of the vehicle is pointed toward the wall) is more difficult and less reliable.
Attempting to immobilize a vehicle on a slope by lowering the bucket is not recommended, as this has been known to result in runaways when the parking brake has failed. It is recommended that vehicle outriggers and stabilizers for underground equipment be made in accordance with CSA Standard B354.2 M82 and designed to prevent the loss of jack extension should brake fluid leaks occur. If these conditions are met, it is possible to immobilize vehicles on slopes by use of at least a pair of “jacks” extended at the down slope end of the vehicle.
Maintenance and repair
Vehicle chocks or an alternative means of blocking vehicle movement, developed in consultation with the JHSC or health and safety representative, must be used during maintenance and repair operations as workers are in very close proximity to the vehicle and are exposed to the risk of injury should the vehicle move inadvertently.
Maintenance and repair includes any activity of inspecting, cleaning, examining, replenishing fluid levels and preventative and/or corrective work to ensure that the vehicle will stay in good operating order. It could include anything from doing a circle check to changing an engine.