Author Jeffery H. Warren
Two of the top causes of workplace accidents, according to the United States Department of Labor’s Occupation Safety and Health Administration, are a lack of machine guarding and improper control of hazardous energy. At first blush, these types of incidents can mistakenly be attributed to an employee’s actions without considering how a machine’s design or the improper control of an environment or situation may have contributed.
The safety hierarchy is a design rule of thumb that’s also effective in the evaluation of such workplace accidents. By its standards, the design of a machine or piece of equipment should eliminate any hazards present. If such hazards can’t be eliminated; then design should include safeguards for prevention. Warning labels should inform equipment operators of all hazards and risks related to use. The onus of safety should never rest solely with the employer or employee.
When we investigate industrial accidents we see time and again that workers and their actions are not the sole cause of an accident or injury. Here are two cases where safety lapses within design led to preventable human tragedies.
A Lack of Proper Machine Guarding
Many industrial machines are designed with safety mechanisms to protect those around them. Some, unfortunately, are not. When I investigated a workplace fatality involving a plant contractor killed while performing sanitation duties on a chicken-halving machine, I could see the machine — a slotted, overhead wheel — was not safeguarded by a shield, fence, or safety enclosure of any kind. Such an enclosure or barrier guard would have included an interlocking switch forcing the machine to stop if the guard was opened.
Industrial process lines often have critical safeguards in place to protect workers.
While it’s sometimes claimed that wet environments make use of an electrical interlock switch difficult, there are machine manufacturers who successfully accomplish this. The machine involved in this incident did not heed the safety hierarchy and put any worker around it at risk. Quite simply, the manufacturer failed to include critical safeguards that were both economically and technologically feasible.
Hazardous Energy Warnings
Another common and very dangerous industrial workplace hazard is a pressurized vessel. I investigated a fatal accident involving a wood treatment facility employee and his supervisor, who both failed to realize a treating cylinder was still pressurized and opened it. Although the pressure vessel was equipped with a locking mechanism, there were no visible or audible alerts to inform personnel of the dangerous state. The employee was struck with so much force he died instantly.
The results can be catastrophic if a pressurized vessel opens.
The safety hierarchy is critical to machine design because it saves lives. When its recommendations are adhered to, accidents can be prevented. The putting workplace safety in the hands of employees who may not know or fully understand the forces at hand when it is not only inherently wrong; it’s dangerous.
Jeffery H. Warren, PhD, PE, CSP, is the chief engineer and CEO at Warren specializing in mechanical, machine design and safety. His deep expertise in machine design and safety analysis makes him a frequent presenter, trainer and expert witness. In addition to investigating more than 2000 claims involving property damage and injuries related to machinery and equipment since 1987, Jeff has an undergraduate degree in Mechanical Engineering from the University of North Carolina as well as a Master of Science and a Doctorate in Mechanical Engineering from Virginia Polytechnic Institute and State University — both with machine design emphasis.
