Moving machine parts have the potential to cause severe workplace injuries. Crushed fingers or hands, amputations, burns, or blindness can be prevented through machine safeguards. Simply put, any machine part, function, or process that may cause injury must be safeguarded.
Where Mechanical Hazards Occur
Dangerous moving parts in these three basic areas need safeguarding:
- Point of Operation: is the area where work is being done on a material, such as cutting, shaping, boring, or forming of material.
- Power Transmission Apparatus: is the area of the mechanical system that transmits energy to the parts of the machine performing the work. These components include flywheels, pulleys, belts, connecting rods, couplings, cams, spindles, chains, cranks, and gears.
- Other Moving Parts: include all parts of a machine that move while the machine is operating. These parts can be rotating, reciprocating, or transversing. Feed mechanisms and auxiliary parts of the machine are considered other moving parts as well.
Hazardous Mechanical Motions and Actions
Many mechanical motions and actions present hazards to the worker.
The following types of motions and actions are common to nearly all machines and recognizing them and their danger is essential to worker protection.
- Rotating: Rotating parts are dangerous because they can grip clothing or skin, forcing an arm or hand into a dangerous area.
- Reciprocating: Reciprocating motions are dangerous because a worker may be struck or pinned during the back and forth or up and down motion.
- Transverse: Transverse motion is movement in a straight continuous line. The danger in transverse motion lies in the possibility of a worker getting caught in a pinch point or dragged by the part itself.
- Cutting: The cutting action may involve all three motions and is dangerous at the point of operation. While the cutting action can be dangerous to fingers, limbs, torso and head, flying chips or debris pose a serious danger to the eyes and face.
- Punching: The punching action results when pressure is applied to the ram for the purpose of stamping metal or other materials. The danger occurs at the point of operation when the material is inserted, held and withdrawn by hand.
- Shearing: Shearing action involves applying power to a slide or knife to trim or shear metal or other materials. Like the punching actions, the hazard occurs at the point of operation.
- Bending: The bending action occurs when power is applied to a slide to draw or stamp metal or other material. The hazard occurs at the point of operation, similar to punching and shearing.
In order to protect the machine operator, safeguards must meet minimum general requirements.
- Prevent contact: The safeguard must prevent hands, arms, and any other part of an operator's body from making contact with dangerous moving parts. A good safeguarding system eliminates the possibility of the operator or another worker placing parts of their bodies near hazardous moving parts.
- Secure: Operators should not be able to easily remove or tamper with the safeguard because a safeguard that can easily be made ineffective is no safeguard at all. Guards and safety devices should be made of durable material that will withstand the conditions of normal use. They must be firmly secured to the machine.
- Protect from falling objects: The safeguard should ensure that no objects can fall into moving parts. A small tool dropped into a cycling machine could easily become a projectile that could strike and injure someone.
- Create no new hazards: A safeguard defeats its own purpose if it creates a hazard such as a shear point, a jagged edge, or an unfinished surface that could cause a laceration. The edges of guards, for instance, should be rolled or bolted in such a way to eliminate sharp edges.
- Create no interference: Any safeguard that impedes an operator from performing the job quickly and comfortably might soon be overridden or disregarded. Proper safeguarding may actually enhance efficiency since it relieves the operator's apprehensions about injury.
- Allow safe lubrication: If possible, workers should be able to lubricate the machine without removing the safeguards. Locating oil reservoirs outside the guard, with a line leading to the lubrication point, will reduce the need for the operator or maintenance operator to enter the hazardous area.
- Concepts and Techniques of Machine Guarding , US Department of Labor
- OSHA Machine Guarding: eTool
- OSHA Machine Guarding: Safety and Health Topic Page
- OSHA Guarding of Portable Powered Tools (29 CFR 1910.243