By Jack Rubinger and John Hamilton
That one of a kind, hand-crafted bed that you’ve admired was not made without risks. The folks at The Joinery (a Portland, Ore., woodworking shop) make beautifully detailed furniture – beds, dressers, armoires, even old-fashioned kids' toys. They are as passionate about their work as they are about woodworking safety. But here’s the catch: A machine designed to reform solid wood has no problem reforming parts of the human body.
Rotating motion machines can be particularly dangerous. Even slowly moving smooth rotating shafts can grab clothing or skin and entangle a worker in a machine leading to death or serious injury. Included in rotating motion are in-running nip points that can grab a small piece of a worker or the worker’s clothing and pull the worker into the machine until a part of the machine breaks or the motors stall out.
Rotating shafts such as power take-off units have caused many injuries, many of which could be avoided with a proper machine guard, as required by OSHA. When a machine or any piece of equipment has a hazard that cannot be eliminated, the appropriate course of action is to install appropriate guarding or other safety devices. The Code of Federal Regulations (CFR) § 1910.211, defines machine guarding as “a barrier that prevents entry of the operator’s hands or fingers into the point of operation.”
Poor machine guarding practices are a major hazard confronted by people every day. About eight out of ten workplace fatalities and one in four workplace injuries involve mechanical equipment. Many workplace machinery injuries are preventable, according to SafeWork SA, Government of South Australia.
“All saws, jointers and milling machines need machine guards,” explains Gary Michael of The Joinery. “We post shop safety policies on the machine guards, using brightly colored signs and labels.”
Unfortunately, at some workplaces, machine guards are circumvented for a variety of reasons: laziness, carelessness or forgetfulness. In addition, there’s some debate between manufacturers about what constitutes a safe machine guarding product.
An understanding of basic machine guarding principles can help equipment manufacturers and employers reduce the likelihood of injury with machinery.
Responsible machine guarding manufacturers take safe machine guarding practices and techniques seriously. “We just installed a guard on the end of a conveyor. The conveyor travels away from you, so there is no danger of you getting caught as the belt travels into the guard. The bottom of the conveyor is totally guarded,” explains Jet LaBarge, vice president of Machine Guard & Cover.
The Right Design in the Right Place
What constitutes an acceptable guard design? OSHA lays out these minimum requirements:
- Prevent contact. A sufficient guard should prevent a person from coming into contact with a hazard. This includes arms, legs and fingers. Openings within the guards or space between the guard and the machine should be small enough that a person cannot come into contact with any hazard within the machine.
- It should not be easy to remove or defeat a safeguard. If the safeguard is easily defeated it really is no safeguard at all. For this reason, any fixed guard attached to the machine should require the use of tools to be removed. If a guard or a gate can be opened by hand, that guard or gate needs to be interlocked to the machine to prevent hazardous motions from occurring while the guard or gate is open.
- Protection from falling objects. An object that falls into a running machine could be struck by moving parts and become a dangerous projectile.
- The guard must not create its own hazard. Installing a guard should not create additional pinch points or cutting hazards.
- Create no interference. A guard that a worker considers a severe hindrance to his job has a higher likelihood of being overridden by the operator.
- Allow safe maintenance and adjustment. If a guard has to be removed regularly for frequent maintenance or adjustment then it has an increased likelihood of being removed and not replaced. Try to design guards so that lubrication can be performed safely without removing the guard.
Hazards generally occur in one of three locations:
- Point of operation, or the location where the machine actually works on material, such as cutting, bending, pressing.
- Power transmission devices that mechanically transmit power from one location to another such as shafts, belts and pulleys, chains and sprockets.
- Other moving parts, such as feed mechanisms, part removal systems and auxiliary parts of the machine or system.
Each of the three locations will have a bearing on what type of guard can be utilized. For example, a power transmission device may require a fixed guard that is bolted in place and rarely has need of removal except for infrequent repair work. A point of operation guard may need to be opened each time a part is made and would be better served by an interlocked guard that stops mechanical motion rather than a fixed guard that needs to be removed with tools.
“Over the years I have seen many in-house guards manufactured, some of excellent quality with hours of thought going into their manufacture and yet on the other side I have seen many more that could only be described as dangerous,” says guarding specialist Leon Myers, who has been designing machinery guarding for 23 years in Australia and overseas.
“During these years I have asked many people who operate machines without guards why they take the risk. The common answer is ‘I’ve been working this machine for years and nothing has happened yet.’ This may be true, but the time will come when an accident does occur,” he says.
A Case in Point
To put a human face on machine guarding, consider Kina Repp.
As a young woman, ready for some adventure, she was literally lured to Alaska where she talked her way into a cleanup crew job at a fishing cannery. There, her boss ordered her to clean underneath a conveyor belt roller.
“My arm was immediately caught when the machine was turned on,” she recalls. “My arm was pulled one way while my head and neck were twisted the opposite way. My arm broke just below my shoulder. The machine kept pulling. The conveyor pulled until my arm was torn from my body.”
Not one to let adversity stop her, Repp has since earned a second degree black belt and has run in 13 marathons. Yet, had a proper machine guarding policy been in place that accident might never have happened.
When you’re unsure about a work situation, think twice before putting yourself in danger. It’s better to be cautious. A machine or a process can always be changed to ensure safety, but a human life is irreplaceable.
About the Authors
Jack Rubinger is an industrial copywriter for Graphic Products, Inc. in Portland, Ore. For more information about Graphic Products and DuraLabel thermal transfer printers and safety labeling supplies, visit www.DuraLabel.com, call Jack Rubinger at 800-788-5572 or email firstname.lastname@example.org.
John H. Hamilton, MSME PE, is a registered professional engineer with a graduate degree in mechanical engineering. He is a full-time faculty member of the University of Arkansas Mechanical Engineering department. Hamilton also provides consulting services to industries, individuals and attorneys who need assistance in industrial safety and machine design issues. For more information, email email@example.com or visit www.jhengineer.com.