Michael Wilson is a professional engineer, Canadian Registered Safety Professional and a Certified Machine Safety Expert. He supports machine safety solutions as a Technical Specialist for Workplace Safety and Prevention Services.
In their various forms conveyors make material handling easier. Unfortunately, equipment that contributes to productivity typically also introduces hazards into the workplace.
Given the significant use of conveyors with DC processes and the close proximity of workers to the equipment, the risk of injury is often underestimated. Crushing injuries, amputations and sometimes fatalities are the result of contact with conveyor-related hazards.
Proper safeguarding practices should be in place to protect workers from the in-running nip hazards and shear points that are found at many conveyors. In many cases, injuries result during cleaning, unjamming or other maintenance activities. It is important to identify risks associated with the conveyor during its entire lifecycle.
A thorough risk assessment should focus on the tasks and hazards and determine what level of risk could result at and around a conveyor system. Safeguarding can help control these risks. Thankfully, there are many safeguarding options available and it is essential for an employer to select a solution that best fits their operation.
A common area of concern is the conveyor’s main drive system. These components are often safeguarded with fixed barriers, as frequent access to this part of the system is not necessary. Fixed distance guarding – which doesn’t completely enclose the hazard but reduces access based on distance from it – is another common measure.
More advanced solutions could make use of safeguarding devices such as interlocked doors, light curtains, area scanners, etc. The application of safeguarding devices requires careful consideration, including ensuring that these devices are placed at the appropriate safe distance from the hazard(s), and that they are integrated to meet an appropriate performance level as determined by a risk assessment.
When door interlocks and light curtains are applied, the hazards must cease or be controlled immediately in order for these devices to be considered effective safeguarding measures. Where the conveyor hazards do not stop instantly, guard locking should be contemplated. In this case, a movable barrier (eg. hinged access door) would be locked in a closed (safe) position until the hazard(s) are controlled or stopped. Only then would a worker be allowed to access the area.
Each part of the safeguarding system should be effective – consider using CSA Z432 (Safeguarding of Machinery) or ASME B20.1 (Safety Standard for Conveyors and Related Equipment) to support your safeguarding solutions.
Emergency stop functions are frequently applied around conveyor systems. In some cases, an emergency stop button would be placed at a workstation and, in others, an emergency stop pull-cord may run the length of a given conveyor. Where e-stops exist and, for that matter, any safeguarding device that signals a stop to the system, workers should understand what action occurs when the e-stop or safety interlocks are activated. The CSA Z432 refers to this as “span of control”. Many conveyor systems can be a considerable size so it is important that workers understand what part of the system would be affected by activating a specific safety device or e-stop.
As with any machine, maintenance will be required at some point, either planned or unplanned. When it comes to conveyor repairs, locking out the equipment is the preferred approach. Workers should have knowledge, training and experience related to the machinery. The employer should establish a lockout program, train and evaluate each worker’s understanding of the lockout requirements.
On occasion, safety measures may be removed or defeated for the sake of maintenance. This practice should be prohibited. In the rare case where lockout prohibits a specific task, other hazardous energy control methods must be in place. CSA Z460 (Control of Hazardous Energy: Lockout and Other methods), CSA Z462 (Workplace Electrical Safety) as well as applicable legislation should be consulted for guidance.
Conveyor design and associated safety methodologies can become complex. The standards mentioned above can contribute to safety around conveyors. As a starting point, look at “A User’s Guide to Conveyor Belt Safety” found on the WSPS website. This resource outlines common hazards, provides an overview of the risk assessment process and summarizes several safeguarding solutions. With this information you can take steps to reduce the risk associated with conveyor systems.