That one of a kind, hand-crafted bed that you’ve admired was not made without risks. The folks at The Joinery (a Portland, Oregon 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.
And that’s where machine guarding comes in. 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.”
Rotating motion machines can be particularly dangerous. Even slow-moving smooth rotating shafts can grab clothing or skin and entangle a worker in a machine leading to death or serious injury. Rotating shafts such as power take off units have caused many injuries, many of which could be avoided with a proper guard.
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.
“All saws, jointers and milling machines need machine guards,” explained Gary Michael, The Joinery. “We post shop safety policies on the machine guards, using brightly colored signs and labels.”
Fortunately for the employees at The Joinery, Mr. Michael recognizes the need to not circumvent equipment guarding that is usually installed by the equipment manufacturer. Mr. Michael’s use of visible signs and labels help remind his employees of the importance of machine guarding.
Appropriate signage and labeling by an employer or manufacturer can help reduce the likelihood of guards being removed or circumvented. Providing such visible reminders for employees can be a life-saving addition to any safety program.
There are some important principles that apply when making labels to be used on guards. For example, there is a tendency to just make a label that says, "WARNING: Do Not Remove Guard." There are some people who may ignore this warning. They could very well think, "I can get away with it just this one time and not get hurt." That is why one of the principles of written warnings is to inform the reader of the consequences of not complying with the warning. An example of a warning statement that communicates consequences is:
WARNING - Do Not Remove Machine Guard. Loss Of Fingers May Result.
Another principle of written warnings is that the warning communicates the actions needed to avoid a hazard such as:
WARNING - Lock Out Breaker 45 Before Removing Machine Guard
A comprehensive discussion of proper warning design is beyond the scope of this article. Employers and equipment manufacturers would do well to familiarize themselves with good warning practices and to work with a label manufacturer that is familiar with good practices and applicable warnings standards.
Responsible machine guarding manufacturers are taking the responsibility for safe machine guarding practices and techniques seriously. “We just installed a guard on the end of 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,” explained Jet LaBarge, Vice President, Machine Guard & Cover.
An understanding of basic machine guarding principles can help equipment manufacturers and employers reduce the likelihood of injury with machinery.
What constitutes an acceptable guard design? This is one question that needs to be asked when trying to guard a machine that contains hazards. An acceptable guard follows these minimum general requirements similar to the minimum requirements laid out by OSHA 3067:
1) 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.
2) It should not be easy to remove or defeat a safeguard. If the safeguard is easily defeated it is really 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 motion from occurring while the guard or gate is open.
3) Protection from falling objects. An object that falls into a running machine could be struck by moving parts and become a dangerous projectile.
4) The guard must not create its own hazard. Installing a guard should not create additional pinch points or cutting hazards.
5) 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.
6) 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 such things as lubrication can be performed safely without removing the guard.
Hazards generally occur in one of three locations:
1) Point of operation -- the location where the machine actually works on material, such as cutting, bending, pressing.
2) Power transmission devices that mechanically transmit power from one location to another such as shafts, belts and pulleys, chains and sprockets.
3) 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.
Poor machine guarding practices are a major hazard confronted by people every day. About 8 out of 10 workplace fatalities and 1 in 4 workplace injuries involve mechanical equipment. Many workplace machinery injuries are preventable, according to SafeWork SA, Government of South Australia.
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 explained. “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.
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.