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Lockout is defined in the Canadian standard CSA Z460-13 "Control of Hazardous Energy - Lockout and Other Methods" as the "placement of a lockout device on an energy-isolating device in accordance with an established procedure." A lockout device is "a mechanical means of locking that uses an individually keyed lock to secure an energy-isolating device in a position that prevents energization of a machine, equipment, or a process."
Lockout is one way to control hazardous energy. See the OSH Answers Hazardous Energy Control Programs for a description of the types of hazardous energy, and steps required in a control program.
In practice, lockout is the isolation of energy from the system (a machine, equipment, or process) which physically locks the system in a safe mode. The energy-isolating device can be a manually operated disconnect switch, a circuit breaker, a line valve, or a block (Note: push buttons, selection switches and other circuit control switches are not considered energy-isolating devices). In most cases, these devices will have loops or tabs which can be locked to a stationary item in a safe position (de-energized position). The locking device (or lockout device) can be any device that has the ability to secure the energy-isolating device in a safe position. See the example of the lock and hasp combination in Figure 1 below.
Tag out is a labelling process that is always used when lockout is required. The process of tagging out a system involves attaching or using an information tag or indicator (usually a standardized label) that includes the following information:
Note: ONLY the authorized individual who placed the lock and tag onto the system is the one who is permitted to remove them. This procedure helps make sure the system cannot be started up without the authorized individual's knowledge.
Safety devices such as barrier guards or guarding devices are installed on systems to maintain worker safety while these systems are being operated. When non-routine activities such as maintenance, repair, or set-up; or the removal of jams, clogs or misaligned feeds are performed, these safety devices may be removed provided there are alternative methods in place to protect workers from the increased risk of injury of exposure to the unintended or inadvertent release of energy.
The main method used and recommended to protect workers from risk of harm in these cases is the use of a lockout/tag out program.
A lockout/tag out program will help prevent:
De-energization is a process that is used to disconnect and isolate a system from a source of energy in order to prevent the release of that energy. By de-energizing the system, you are eliminating the chance that the system could inadvertently, accidentally or unintentionally cause harm to a person through movement, or the release of heat, light, or sound.
An organization will have one lockout program document, and as many sets of work instructions as required, depending on the number of systems that require lockout.
The written lockout procedures will identify types of hazardous energy covered by the procedures, types of energy-isolating or de-energizing devices, what needs to be done, when it needs to be done, what tools are needed to do it, who is supposed to do it, how the shutdown/de-energization/energization/start-up will occur, who required education and training, and who needs to be notified. As with all programs or procedures, a continuous improvement or auditing step should also occur.
The document should specify:
Work instructions will identify how the lockout process is to be carried out in a step-by-step manner including how stored energy is controlled and de-energized, how isolation can be verified, and how and where lockout devices are installed. Work instructions are machine, equipment or process specific and may include pictures or images of what is being described.
Lockout and tag out processes involve more than putting a lock on a switch. They are comprehensive step-by-step processes that involve communication, coordination, and training.
Please note the following definitions from CSA Z460-13:
Affected person - persons who are not directly involved in the work requiring the hazardous energy control, but who are (or may be) located in the work area.
Authorized person - a person who is qualified to engage in hazardous energy control because of knowledge, training, and experience and has been assigned to engage in such control.
Steps of a lockout/tag out program include:
1. Prepare for shutdown
The authorized person will identify which sources of energy are present and must be controlled; and more importantly, identify what method of control will be used. This step involves completing sets of specific work instructions that outline what controls and practices are needed to lock and tag out a system before performing any activity.
2. Notify all affected employees
The authorized person will communicate the following information to notify affected persons:
3. Equipment Shutdown
If the system is operating it should be shutdown in its normal manner. Use manufacturer instructions or in-house work instructions. Equipment shutdown involves ensuring controls are in the off position, and verifying that all moving parts such as flywheels, gears, and spindles have come to a complete stop.
4. Isolation of system from hazardous energy
The exact written instructions will be specific to that system in the workplace. In general, the following procedures are used:
5. Dissipation (removal) of residual or stored energy
In general, examples include:
6. Lockout/Tag out
When the system's energy sources are locked out, there are specific guidelines that must be followed to make sure that the lock cannot be removed, and the system cannot be inadvertently operated. These guidelines include:
7. Verify Isolation
Verify that the system is properly locked out before beginning any work. Verification can take place in several ways:
Choose the method that will best make sure that the energy to the system has been isolated without creating other hazards during the verification.
8. Perform Maintenance or Service Activity
Complete the activity that required the lockout process to be started.
9. Remove Lockout/Tag out devices
To remove locks and tags from a system that is now ready to be put back into service, the following general procedure can be used:
*Note - it is good practice to make sure any individual who placed a lock on the system should also be present when the system is re-started. This practice helps make sure those employees working on the system are not in a hazardous area when the machine is restarted.
Each party in the workplace has a responsibility in the lockout program. In general:
Management is responsible for:
Supervisors are responsible for:
Authorized individuals are responsible for:
Note: The Canadian standard CSA Z460-13 "Control of Hazardous Energy - Lockout and Other Methods" contains more information and many informative annexes about various risk assessment, lockout situations, and other control methods.