Reprinted from the ACJ - January, 1999
The first punch caught him square in the jaw. The room spun and he heard bells. End of the round? No, couldn't be. He heard the crowd yelling, "Duck!" just as the heavy arm swung down atop his head. He dropped to his knees. His vision blurred and then blinked out, like a TV you just turned off.
He came to, not to the count of the referee, but to his foreman asking, "Are you all right? Who moved that safety cage on the radiator lift? That guard is there for just this reason! Wow! That's going to leave a hell of a bump."
Machinery is a part of our lives. We use hoists, lifts, saws, grinders, motors, pumps and presses at work. Dozens of mechanical monsters are waiting to ambush us. How do we protect ourselves? Machine guarding.
The hazards associated with equipment can be divided into two main categories: machine motion hazards and machine action hazards. Motion hazards are presented by the moving parts of the machine itself. Consider a saw. It spins, it cuts, you bleed. The action type of hazard is the result of the machine doing its job. A rifle, for example, doesn't hurt you. It fires and then sits there. It's that darn bullet that causes all the problems.
Let's take a closer look. We can break down the machine motion danger into specific types of motion that threaten our well-being.
Rotation hazard exists in grinders, saws and wire wheels. How do we protect ourselves? Physical guarding of the rotating parts is the most effective. Plastic shields, tool work rests, blade guards and kickback guards are all designed to keep our fingers out of the danger zone.
Another type of machine motion hazard is termed a "pinch point." Hoists and lift arms that hinge at some point are just waiting to catch and crunch a body part. As are choppers, where one blade slides next to another creating a pinch point. Think of a scissors type action.
Watch out for loose clothing, necklaces, long hair, etc. They can get snagged on moving machinery and pull you in. Use lockout/tagout methods when performing maintenance on machinery. Physically locking the on/off switch or circuit breaker can give peace of mind when your head is in the business end of machinery.
Less obvious is the area below a car hoist, or the swing area of a lift arm like our Golden Gloves champion from the first paragraph. These can also be considered a pinch point hazard. Physical guards can keep us out of a chopper blade, but the area under a hoist or the swing area of a lift is a little bit more tricky.
Usually, perimeter guarding is used in these situations. We simply keep a safe distance from the danger zone. We paint the floor yellow below the hoist and stay out of there while we are lowering it. Or we put up guardrails or cages to keep people away from the machine motion area. Warning signs are another way to warn of these "hard to guard" areas.
Transmission type hazards round out this category. This is the danger presented by drive belts and chains, gears, driveshafts and pulleys. Enclosing them behind guards and cages is the best solution.
The other machine hazard category is an action hazard. The best example is flying debris. Grinders, saws and golf clubs all send objects into orbit. Shields in the discharge area of grinders and saws help protect us. Standing out of the projectile area also helps, especially for golf clubs, so sometimes "perimeter guarding" is employed.
Presses fall into this category. Apparently, the experts feel it is not the motion of the press but the action 25 tons of force_ that is a concern. That is kind of like saying it's not the fall from a high place that hurts, it's the sudden stop at the end. Guards, perimeter cages, guardrails or electronic "light curtains" which shut off the machine if the light beam is broken are utilized here.
Other ideas to keep in mind include using personal protective equipment (PPE) for protection from flying debris. PPE includes glasses, goggles, aprons and face shields. Chain mail, or Kevlar, gloves can protect against knife edge pinch points. Steel-toed boots and metatarsal guards can save your feet from being crushed.
One last point to consider: Removal of machine guarding is not recommended, but sometimes necessary to perform a task. Use extreme caution. Be aware of the increased danger. Perform only what is necessary and immediately return the guard when finished. Your co-workers, especially the one with the big lump on his forehead, will thank you.
Now, let's get ready to rumble!
The above article was written by David M. Brown, Chief Engineer of Johnson Manufacturing Company, Inc. and is published by JOHNSON with the expressed approval of the National Automotive Radiator Service Association and the Automotive Cooling Journal. Other reproduction or distribution of this information is forbidden without the written consent of JOHNSON and NARSA/ACJ. All rights reserved.
JOHNSON MANUFACTURING COMPANY
114 Lost Grove Road / PO Box 96 / Princeton, Iowa 52768-0096
Phone 563-289-5123 or Fax 563-289-3825