Moving machine parts create workplace hazards and potential machine-related injuries, which makes machine guards a necessity. All machines consist of three fundamental components – the point of operation, the power transmission device, and the operating controls. Machine safeguarding helps protect workers from preventable injuries in all these areas.
The Occupational Safety and Health Administration’s (OSHA’s) requirements for machine guarding are found in 29 Code of Federal Regulations (CFR) 1910 Subpart O, Machinery and Machine Guarding as detailed below;
· 1910.211 — Definitions
· 1910.212 — General requirements for all machines
· 1910.213 — Woodworking machinery
· 1910.214 — Cooperage machinery [Reserved]
· 1910.215 — Abrasive wheel machinery
· 1910.216 — Mills and calendars in the rubber/plastics industries
· 1910.217 — Mechanical power presses
· 1910.218 — Forging machines
· 1910.219 — Mechanical power-transmission apparatus
29 CFR1910.212(a)(1) states that one or more methods of machine guarding must be used to protect operators and other employees from hazards, including those created by point of operation, in-running nip points, rotating parts, flying chips and sparks.
Mechanical Motions & Actions that Create Hazards
The first step towards protecting workers and promoting safety in the workplace if to identify hazards. The basic types of hazardous mechanical motions and actions are as follows:
- In-running nip points
Hazardous Mechanical Motions
ROTATION – A rotating motion can be dangerous no matter the size or speed of the equipment. Even a smooth, slowly rotating shaft can grab clothing or through skin contact can force an arm or hand into a dangerous position.
Collars, couplings, cams, clutches, flywheels, shaft ends, spindles and horizontal or vertical shafting are examples of common hazardous rotating mechanisms. The risk rating can go up depending on surroundings, such as bolts, nicks, abrasions, and projecting keys or set screws are exposed on rotating parts.
NIP POINTS – Through rotating parts, in-running nip points are created. On many machines parts rotate closely together in opposite directions, while their axes are parallel to each other, when they run closely, the stock fed between two rolls produce a nip point. This danger is common on machines with intermeshing gears, rolling mills, conveyors, and calenders. Other nip points can be created between a power transmission belt and its pulley, a chain and its sprocket, or a rack and pinion.
RECIPROCATING – The reciprocating motion is aback-and-forth or up-and-down action that can strike a worker or catch a worker between a moving and stationary part.
TRANSVERSE – Movement in a straight line, mobbing parts can catch or strike a worker in a pinch point or shear point.
Hazardous Mechanical Actions
CUTTING – Cutting action hazards can be caused by rotating, reciprocating, or transverse motion, where finger head, and arm injuries can occur. Flying chips and scrap materials can also be an outcome and can strike a worker’s eyes or face. Cutting actions are dangers with bandsaws, circular saws, and boring, or drilling machines.
PUNCHING – Think power presses, punching action results when pressure is applied to a slide (ram) for the purpose of blanking, drawing, or stamping metal or other materials.
SHEARING – Shearing action involves applying power to a shear or knife to trim or shear a range of materials, often metals. The danger is where stock is inserted, held, and withdrawn, as with hydraulically or pneumatically powered shears.
BENDING – Bending action results when power is applied to a slide to draw or stamp metal or other material. This is a threat where stock is inserted, held, and withdrawn, as with equipment such as power presses.
Here is a list of minimum general requirements when it comes to machine guarding.
1. PREVENT CONTACT: A guard must prevent hands, arms, or any other part of a worker's body from contacting dangerous moving parts.
2. BE SECURE: Guards must be firmly secured to the machine where possible or secured elsewhere if attachment to the machine is not possible. Workers should not be able to easily remove or tamper with the guard.
3. PROTECT FROM FALLING OBJECTS: The safeguard must ensure no objects can fall into moving parts.
4. CREATE NO NEW HAZARDS: A safeguard would defeat its purpose if it were to create a hazard such as a shear point, a jagged edge, or an unfinished surface. Edges of guards should be rolled or bolted so that they eliminate sharp edges.
5. CREATE NO INTERFERENCE: Any guard that impedes a worker from performing a job quickly and comfortably might be bypassed or disregarded. Proper safeguarding can enhance efficiency because it relieves a worker's injury apprehensions.
6. ALLOW SAFE LUBRICATION: When possible, the machine should be able to be lubricated without removing the safeguard. Locating oil reservoirs outside the guard, with a line leading to the lubrication point, will reduce the need for the operator or maintenance worker to enter the hazardous area.
Types of Guards
1. FIXED GUARDS - Permanent parts of a machine. These guards are preferable as they are simple and permanent.
2. INTERLOCKED GUARDS - Automatically shut off or disengage power through a tripping mechanism when it is opened or removed. The machine cannot cycle or start until the guard is replaced.
3. ADJUSTABLE GUARDS - Useful because they accommodate various sizes of stock, but not always the best fit.
4. SELF-ADJUSTING GUARDS - Allow the opening of these barriers to be determined by the movement of the stock. As the operator moves the stock into the danger area, the guard is pushed away providing an opening that only is large enough for the stock.
Guards that are constructed by the machine fabricator, or a company that specialises in custom guards, are desirable because they conform to the design and function of the machine being guarded. They can also be designed to strengthen the machine or to serve some additional functional purpose.
When it comes to older machines, custom guards are typically the best route to take, whether these are built in house, or you outsource to a custom machine guarding expert like Belt Conveyor Guarding.
Any material that is substantial enough to withstand impact and prolonged use, such as metal, plastic, and wood, are all used as construction materials for machine guards. In many, if not most, circumstances, metal is the best material for guards. It might also be feasible to use plastic where higher machine visibility is required. Guards made of wood are not recommended because of flammability and lack of durability and strength.
29 CFR 1910.219 Mechanical power-transmission apparatus, states that wood guards can be options in woodworking and chemicals industries, and in industries where vapors or gases or other conditions could deteriorate metal guards. Wood guards also may be used in construction work and in outdoor locations where extreme cold make metal guards undesirable. In all other industries, wood guards are not allowed, per 29 CFR 1910.219 (o)(2).