Machine Guarding: Last Defense Against Injuries
OSHA’s Top Ten Most Cited Violations for 2017 were released a few months ago, and again machine guarding was on the list, in eighth place with 1,933 violations. Remember, those are only the violations OSHA’s 2,100 inspectors found and cited. Many other companies have not put the required guards on their equipment, and the Bureau of Labor Statistics’ data shows approximately 2,000 accidents left employees with pain, crushed fingers, hands, arms, disfiguring amputations, and even death. Manufacturing jobs have incident rates more than twice that of general industry, so this area still needs attention to further protect employees. Many of the injuries occur when employees try to remove a blockage or to clean or maintain equipment. Machine guarding can work in tandem with LockOut/TagOut rules, but it is different. LOTO is often used when a machine is being maintained or serviced. Machine guarding should be in place at all times to protects employees who work with the machinery day-to-day.
Any equipment (manufacturing, ventilation, transport, etc.) may have pulleys, spokes, fan blades, axles, shafts, conveyors, sprockets, rollers, rotating couplings, grinding wheels, belts, chains, gears, calenders, blades, punches, presses and the like, all of which can mangle human body parts that get in the wrong place at the wrong time. In 29 CFR 1910.212, OSHA describes the places where these actions occur as the “point of operation” and guards are to be installed on equipment to protect employees body parts from coming in contact with these hazards, and from flying chips and sparks while equipment is in use. Well-designed machine guards will prevent machine operators from having any body part in the danger zone during the operation of equipment.
OSHA’s guarding regulations apply to small portable powered hand tools as well as large equipment and robots. Larger machines that operate in fixed locations must be securely anchored to the floor to prevent “walking” or movement across the floor (think washing machine). Hand tools may be designed and used to place and remove materials while keeping hands a safe distance from the point of operation. (1910.212(a)(3)(iii).
Common types of guards include:
Location and distance—Though not actually a guard, OSHA allows employers to place hazardous moving parts high overhead, beneath a catwalk, or in another location that is out of reach of employees. A hazard assessment must be completed to ensure no employees will ever be exposed to the moving parts.
Fixed guards—A permanent part of the machine that keeps employees a safe distance from moving parts.
Adjustable guards—These can be adjusted with each job to deflect swarf and sparks or they can be adjusted for each job to receive larger stock.
Self-adjusting guards—These guards adjust as the work is being done. The guard is often pushed out of the way as the stock is fed into the machine. (Think of a rotary saw blade guard which lifts or pushes out of the way as the stock is fed into the saw.)
Gates—Movable barriers positioned before operating a machine, placed to protect the operator or others working in the area.
Interlocking guards—These are often doors that automatically shut off or disengage the moving parts when opened. If the mechanism is tripped, the machine will not cycle.
Two-handed controls—Requires both of the operator’s hands to be on pressure sensitive controls for the duration of the machine operation. If either hand is removed from the controls, the machine will stop.
Restraint devices—These are typically fastened to the operator’s wrists to prevent the operator from ever reaching into the danger zone.
Pullback devices—Similar to restraint devices, but the cables allow the operator’s hands to move into the danger zone and then out before there is an action that could cause harm.
Presence sensing devices—These photoelectric or radio frequency devises sense when a light or radio beam is interrupted (by a body part entering the danger zone). When the beam is broken, the machine will stop.
Electromechanical sensing devices—These devices have probes or contact bars that move to a predetermined position when the operator starts a machine cycle.
OSHA also has requirements that all machine guards must meet. The minimum requirements are:
1. Prevent contact—Guards must be designed to prevent any part of a worker’s body from moving parts and subsequent injury.
2. Be secure—Once in place, employees should not be able to disable or remove guards easily. The guards should be tamper-free and not easily bypassed.
3. Protect from falling objects—Guards should ensure nothing can fall into the moving parts from above.
4. Create no new hazards—The guards should create no new hazards like sharp edges, snags, or injury during application or adjustment.
5. Create no interference—All guarding should be tested by employees so it doesn’t hinder their work or cause additional actions or awkward movements.
6. Lubricate equipment—Must be able to lubricate equipment safely without removal of the guards.
Machine guarding regulations have been around since the 1970s, and most machine manufacturers today build their machinery with guarding in place. If your facility has equipment that precedes the regulations, you’ll be glad to know there are businesses that can help retrofit with guarding that meets today’s standards.
The best way to ensure you’re providing the necessary guarding is to involve employees in a machine and power tool inventory, assessing for each equipment where the dangerous actions occur and determining how to guard against employee contact in the danger zone(s).
For more information on machine guarding, refer to the American National Standards Institute’s (ANSI’s) B11 Subcommittee responsible for developing machine tool safety standards. Information is available at www.ansi.org.
Click here to see this story as it appears in the March 2019 issue of Modern Casting