The worst-case scenario for any manufacturer is an injury in the workplace. Protecting workers from machine-related injuries is always a priority. According to OSHA, workers who operate and maintain machinery experience as many as 18,000 injuries every year, including everything from bruising and scrapes to amputations, lacerations, blindness, and even death.
There are several techniques for protecting against the hazards created by mechanical motion. These include proper training, personal protective equipment (PPE), and the use of guards. Guards can be one of the most effective ways to prevent injuries, but only when properly designed, installed, and used.
OSHA regulations state that at least one method of machine guarding must be supplied to protect workers in the machine area from hazards at the point of operation. Guards must also be supplied to protect from rotating parts, in-running nip points, and flying debris. Before we get into the types of guards needed to prevent accidents, let’s first examine the different types of hazards that machinery can present and how those potential hazards can cause injury to workers.
Where the Danger Lies
All machines have three fundamental areas that can be hazardous: the point of operation, the power transmission device, and the operating controls. The point of operation refers to where the work is being performed on materials, including cutting, shaping, and boring. The power transmission apparatus includes all system components that transmit energy. These include flywheels, belts, connecting rods, chains, cranks, and more.
There may also be other moving parts while the machine is operational. For example, there may be parts that are rotating, transverse-moving, or reciprocating. Feed mechanisms and auxiliary components can also be dangerous. Machine safeguarding helps protect workers from preventable injuries in all of these areas.
Primary Hazardous Motions & Actions
There are several different categories of movements and actions that machines perform that can lead to potentially dangerous situations. To design guards properly, these mechanisms must first be understood.
- Rotating. Even a slow rotation can be dangerous as clothing or loose items can be caught, or hands and arms can be forced into dangerous positions. Common rotating mechanisms include collars, cams, flywheels, shaft ends, spindles, and meshing gears. Projecting items such as screws, bolts, nicks, abrasions, and keys can increase the danger of a rotating mechanism.
- In-Running Nip Points. These occur wherever parts move toward each other or when one part moves past a stationary object. Opposite rotations from components such as intermeshing gears, calendars, and rolling mills can create a shearing or crushing hazard.
Rotating parts and tangentially moving parts such as a belt and pulley create pinching, crushing, or shearing hazards. Lastly, rotating and fixed parts such as spoked handwheels or the periphery of an abrasive wheel can create a shearing, crushing, or abrading hazard.
- Reciprocating. In this motion, a worker can be caught or pinned between a working and a stationary part during the back/forth or up/down movement. For example, a part that moves back and forth pinning a worker against a wall.
- Transverse motion: This movement happens in a straight, continuous line, and moving parts can strike or catch a worker at a pinch or shear point.
- Cutting. This action can involve rotating, transverse, or reciprocating motion. The danger exists at the point of operation where a bodily injury can occur, often to fingers, hands, or arms.
Flying material can also pose a hazard, especially to the eyes, face, or head. Examples include bandsaws, circular saws, boring or drilling machines, turning machines (lathes), or milling machines.
- Punching. This action results when power is applied to blank, draw, or stamp metal or other materials. The danger exists at the point where stock is inserted, held, or withdrawn by hand. Power presses and iron workers are typical machines with punching actions.
- Shearing. Shearing occurs when power is applied to a slide or knife to trim or shear materials. The danger exists at the point of operation where the stock material is inserted, held, or removed. Shearing machinery typically includes hydraulic or pneumatic power shears.
- Bending. Bending occurs when power is applied to a slide to draw or stamp metal or other materials. The hazard exists at the point of operation where stock is inserted, held, and removed. Power presses, brake presses, and tubing benders are common examples.
Types of Guarding
Safeguards are typically grouped together as either guards or devices. Guards are physical barriers that prevent access to dangerous areas. The four main types of guards include fixed, interlocked, adjustable, and self-adjusting. A fixed guard is a permanent part of the machine and is preferred for its simplicity.
An interlocked guard will automatically disengage power to the machine when it is opened or removed. An adjustable guard is useful to accommodate various types of stock, and self-adjusting guards allow the movement of the stock to determine the opening of the barrier.
Devices will perform one of many functions to protect workers. A device may stop a machine if an unexpected object (such as part of the body) is placed in the area of danger. A device may restrain or withdraw an operator’s hands from the dangerous area or require both hands to remain on the controls to keep them clear of danger. It may also provide a synchronized barrier with the machine’s operating cycle to prevent entry into the dangerous area during operation.
The best method for constructing safeguarding depends on several factors. These include the type of machine and operation, the size or shape of stock, how the materials are handled, the layout of the work area, the type of material, and any requirements or limitations of the production.
The most effective guards are often the ones designed and attached to the machine by the manufacturer as they tend to conform to the design and function of the machine. They can also be designed to strengthen the machine or to serve some additional functional purpose.
User-built guards are sometimes necessary for older machines or other unique or changing situations where a manufacturer-built guard is unavailable. The main drawback is that a user-built guard might not conform well to the configuration and function of the machine and, therefore, may be poorly designed or built. For that reason, a machine safety consultant can design and implement a custom safeguarding solution.
Materials are also an important consideration as the guard must withstand both impact and prolonged use. Metal, plastic, and wood are common choices, with metal generally considered the best option in many cases. Plastic is also a good choice where higher machine visibility is required, whereas the flammability and lack of strength of wood lands it last on the list.
OSHA standards allow for wood to be used in woodworking and chemical industries, and those where vapors, gasses, or other conditions could cause metal guards to deteriorate. Wood is also allowed in construction work and outdoor sites where extreme cold can make metal guards problematic. In all other cases, wood guards are not allowed.
What Makes a Proper Guard?
A properly designed and installed guard will protect workers from mechanical hazards without impeding their ability to complete their tasks. To be considered safe and effective, these minimum requirements must be met for all guards:
- Prevent Contact. The guard must physically prevent hands, arms, or any other part of a worker’s body from contacting moving parts. A good safeguard will eliminate any possibility of the worker from placing any part of their body near hazardous moving parts.
- Secure. Safeguards should not be easy to remove or be tampered with. Guards must be durable enough to withstand the conditions of normal use and firmly secured to the machine.
- Protect from Falling Objects. No objects should be able to fall into moving machine parts, including small tools, debris, etc.
- No New Hazards. If a safeguard creates a different hazard, it has defeated its purpose. An example is a newly created shear point or an unfinished edge of a guard that could cause a laceration. Guard edges should be rolled or bolted in such a way that sharp edges are eliminated.
- No Interference. Safeguards must not impede workers from performing their tasks quickly and comfortably, or workers may override or disregard them. Proper safeguarding can often enhance efficiency as they reduce apprehension regarding injuries.
- Allow Safe Lubrication. The machine should be easily lubricated without removing safeguards whenever possible to reduce the need for operators or maintenance workers entering the hazardous area.
Training and PPE
Even with proper safeguards in place, training is still necessary to help workers understand the need for a guard as well as how to use it. Operator training should begin with a description and identification of the hazards associated with the machine. The safeguards should be demonstrated, including how and why they are necessary. If there are circumstances when the guard can be removed (i.e., for maintenance), these should be listed as well.
Operators and other employees should be instructed to inspect all tools and guards before use and follow all proper lockout/tagout procedures when necessary. They must follow the correct procedures for setting up and adjusting the machine, and when performing maintenance tasks such as lubricating parts. Finally, workers should know what to do when a guard is damaged, missing, or not providing proper protection. For example, damaged guards and machinery should be labeled and reported immediately.
Proper safeguards do not always negate the need for PPE, including things like hard hats or helmets, gloves, hearing protection, and safety goggles. All PPE must always be appropriate for conditions, properly maintained, stored correctly when not in use, and kept clean, fully functional, and sanitary. Even when all the conditions are right, suitable safeguards are in place, and proper PPE is used, workers must be cautioned against loose clothing, jewelry, long hair, or other personal items that could pose a hazard.
Safety is Everyone’s Priority
So, in a nutshell, why is machine safeguarding important? A safe workplace is one where everyone takes responsibility for their own safety and the safety of others. Workers must be properly trained to understand the hazards of their workplace and empowered to speak up when something is not right. When proper guards, PPE, and employee training are combined, you can be sure you’re doing everything you can to keep your crew safe from preventable injuries.