Page 59 - Hub-4 Magazine Issue 72

Bulk Handling
Engineering safer conveyors: Art meets science
All new conveyor systems will inevitably succumb to the punishing bulk handling environment and begin the slow process of degradation. The system will eventually require more time and labor for maintenance, shorter spans between outages, longer periods of downtime and an ever-increasing cost of operation. This period is also accompanied by an increased chance of injury or fatality as workers are progressively exposed to the equipment to perform cleaning, maintenance and to fabricate short-term fixes to long-term problems. A total system replacement is cost prohibitive, but to remain compliant and/or meet ever-increasing production demands, upgrades and repairs are unavoidable.
When examining the safety of a system, improving efficiency, and reducing risk can be achieved by utilizing a hierarchy of control methods for alleviating hazards. The consensus among safety professionals is that the most effective way to mitigate risks is to design the hazard out of the component or system. This usually requires a greater initial capital investment than short-term fixes but yields more cost- effective and durable results.
The Science: Hierarchy of control methods
Examining the US Occupational Safety and Health Administration (OSHA) accident database reveals the dangers of working around conveyors.[1] Studies have revealed that the highest prevalence of accidents are near locations where cleaning and maintenance activities most frequently take place: take-up pulley, tail pulley and head pulley.
Designs should be forward-thinking, exceeding compliance standards and enhancing operators’ ability to incorporate future upgrades cost-effectively and easily by taking a modular approach. Designing hazards out of the system means alleviating causes with the intent to bolster safety on a conveyor system, but the methods of protecting workers can vary greatly. In many cases, it will be necessary to use more than one control method, by incorporating lower ranked controls. However, these lower-ranking approaches are best considered as support measures, rather than solutions in and of themselves.
PPE includes respirators, safety goggles, blast shields, hard hats, hearing protectors, gloves, face shields and footwear, providing a barrier between the wearer and the hazard. Downsides are that they can be worn improperly, may be uncomfortable to use through an entire shift, can be difficult to monitor and offer a false sense of security. But the bottom line is that they do not address the source of the problem.
Administrative Controls (changes to the way people work) create policy that articulates a commitment to safety, but written guidelines can be easily shelved and forgotten. These controls can be taken a step further by establishing “active” procedures to minimize the risks. For example, supervisors can schedule shifts that limit exposure and require more training for personnel, but these positive steps still do not remove the exposure and causes of hazards.
Warning Signage is required by law, so this is less of a method than a compliance issue. It should be posted in plain sight, clearly understood, and washed when dirty or replaced when faded. Like lower-tier methods, signs do not remove the hazard and are easily ignored.
Installing systems such as Engineering Controls that allow remote monitoring and control of equipment -- or Guards such as gates and inspection doors that obstruct access -- reduce exposure, but again, do not remove the hazard.
Using the Substitute method replaces something that produces a hazard with a piece of equipment or change in material that eliminates the hazard. For example, manual clearing of a clogged hopper could be replaced by installing remotely triggered air cannons.
Examples of Eliminate by Design are longer, taller, and tightly sealed loading chutes to control dust and spillage or heavy- duty primary and secondary cleaners to minimize carryback. By using hazard identification and risk-assessment methods early in the design process, engineers can create the safest, most efficient system for the space, budget, and application.
Safety improves as the type of hazard control moves higher up the hierarchy of methods.[2]
Incorporating effective hazard control techniques is easier and less costly in the early stages of a project.[2]
www.hub-4.com Jan-Feb 22 - Issue 72
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