A guard that is secured to the machine, where possible, and prevents entry of an operator’s hands or fingers into the point of operation.
A guard that completely encloses and prevents access to dangerous areas. Enclosure guards are typically seen on power transmission components like sprockets, chains, flywheels, pulleys, gears, shafts and wheels.
A guard that is not fixed and may be opened or removed as the operation requires—resulting in the machine shutting off automatically if the interlocked guard is opened or removed. Example: A lid to a revolving drum or barrel (like a blender) which is interlocked with the drive mechanism. When the lid is opened, the drum or barrel automatically shuts and doesn’t revolve.
Presence Sensing Guard
A guard that is designed tostop the machine if an operator’s hand or any part of the body is placed in a danger area.
Other Types of Guards
Two-handed trip or two-handed control that requires use of both hands at the same time on control buttons to activate the machine. Example: The two-hand control to operate the hide puller.
Gates that provide a barrier that is synchronized with the operating cycle of the machine.
A constant pressure switch can be used on certain devices like splitter saws. The power is automatically shut off whenever the operator releases control.
Other engineering controls related to guards include:
- Special hand tools like hooks or long push sticks which help the worker place materials into or remove materials from the point of operation without putting his or her hands into the danger area. Example: In a meatpacking plant, push sticks may be used with pieces of meat which have to be pushed into a saw or blade for cutting.
- Isolating or relocating the machine to reduce or eliminate exposure to the hazard.
In order to be effective, machine guards must meet the following requirements:
- Prevent any part of a worker’s body from making contact with dangerous moving parts.
- Be secure so that the guard cannot easily be tampered with or removed.
- Does not create any new hazards.
- Does not interfere with a worker’s ability to perform the job efficiently.
A worker can be seriously injured or killed while servicing, cleaning, fixing or maintaining equipment that unexpectedly starts up or becomes energized because it has not been locked out or tagged out. Lockout and tagout of a machine means that all of the energy sources for the equipment or machine are turned off or disconnected anda lock is used to “lockout” the switch, valve or other energy disconnect mechanism. A tag can only be used in place of a lock when locks cannot be used.
A member of a clean-up crew in a poultry plant in South Carolina was cleaning the inside of a chiller. A co-worker was attempting to repower an adjacent chiller and inadvertently turned on the wrong chiller, crushing his co-worker to death. During their investigation, OSHA found that the control panels had recently been moved and the necessary parts for attaching locks were on order and therefore missing. As a result, workers were turning the chillers off during cleaning instead of locking out the chillers as required.
OSHA’s lockout/tagout standard, 1910.147, requires employers to have a lockout/tagout program to prevent death and injury from the unexpected start-up of equipment and machinery or the release of stored energy.
What Types of Lockout/Tagout Procedures to Look For
As outlined in the lockout/tagout standard, machinery and equipment must be turned off and disconnected from the power or energy source and a lock or other energy-isolating device applied to the circuit breaker, disconnect switch or line valve before maintenance, repair, unjamming, cleaning, lubricating, adjusting or making tool changes occur.
Workers are also in danger of coming into contact with hazardous energy during installation, maintenance, service, cleaning or repair work. Hazardous energy can be of the following types:
- Mechanical energy in the moving parts of mechanical systems.
- Potential energy, which is force stored in an object not moving, such as a spring under tension. Potential energy can be stored in pressure vessels, gas tanks, hydraulic or pneumatic systems.
- Electrical energy from generated electrical power, static sources, or electrical storage devices (such as batteries or capacitors).
- Thermal energy (high or low temperature) resulting from mechanical work, radiation, chemical reaction, or electrical resistance.
- Steam and condensate systems under pressure or compressed air.
OSHA requires the employer to develop lockout and tagout programs and policies that address machinery and equipment, as well as all forms of hazardous energy.
Documented procedures clearly and specifically outline the scope, purpose, authorization, rules and techniques to be utilized for the control of hazardous energy, including:
- Specific steps for shutting down, isolating, blocking and securing machines or equipment to control hazardous energy;
- Specific steps for the placement, removal, transfer and responsibility for lockout or tagout devices;
- Procedures that are clearly written for each machine in a language that all workers can understand; and
- Specific requirements for testing a machine or equipment to determine and verify its effectiveness.
Basic Lockout Procedures
Basic, generalized lockout/tagout procedures include the steps outlined below . The actual lockout/tagout procedures used in each plant and on each particular machine in the plant must be written specifically for the particular machine. The basic, general lockout/tagout steps are:
- Preparing for shut down;
- Shutting down the machine or equipment;
- Applying the lockout or tagout device;
- Rendering safe all stored or residual energy; and
- Verifying the isolation and deenergization of the machine or equipment.
Lockout/Tagout Procedures and Training
As important as a lockout/tagout program is, it can only be effective if employees are aware of the program and trained properly. Three types of employees are covered by the standard: authorized, affected, and other. The amount and type of training that employees receive depends on their job in relation to the machine that is being locked out or tagged out.
Authorized Employees are officially approved to do the lockout/tagout, including those who install, service, repair, clean or maintain machinery and equipment and perform the servicing or maintenance. These employees should receive training on:
- The types of hazardous energy sources that they may encounter in the workplace;
- The procedures and safe work practices necessary to isolate and control hazardous energy sources; and
- Electrical energy sources and hazards.
Affected/Other Employees perform jobs in areas where lockout is used during servicing or maintenance operations. Usually machine operators or users must receive training about all circumstances when lockout procedures are to be used on any equipment that they operate. They also need to understand the purpose of the procedure and the importance of not using or starting up any equipment or machines that are locked out or tagged out.
Employees should be retrained whenever there is:
- A change in their job assignment;
- Equipment or processes present a new hazard; and
- A change in the energy control procedures.