Understanding Lockout Tagout

lockout tagout

Lockout Tagout Definition - The placement of a lock device on an energy-isolating device to ensure equipment cannot be operated during equipment maintenance or repair, according to OSHA standard Reg. 29 CFR 1910.147 and CSA Z460.

The placement of a tag device on an energy-isolating device to warn of the danger of operating, and TO NOT start,  the equipment until the tag is properly removed.

Affected Employees:
Any worker whose job requires them to operate/use or be in the area of machinery or equipment on which service/maintenance is being performed.

Authorized Employees:
The person who is responsible for the lock machinery or equipment.

Lockout Device:
A device such as a lock (key or combination) that holds/secures an energy-isolating device, thus preventing an energy source from operating.

Tagout Device:
A prominent warning device, such as a tag with a means of attachment, which can be securely fastened to an energy-isolating device.

An energy- isolating device (switch, lever, etc.)  able to be locked out via a hasp or other means,  to which a lock can be affixed. 

When a tagout device is used on an energy-isolating device which is able to be locked out,  it MUST be attached at the SAME location as  the LO device would be, AND demonstrate equivalent level of safety to the energy control program.

Hazardous Energy Defined:
Hazardous Energy Sources includes electrical, mechanical, hydraulic, pneumatic, chemical, thermal, or other sources in machines and equipment can be hazardous to workers. During the servicing and maintenance of machines and equipment, the unexpected startup or release of stored energy can result in serious injury or death to workers.


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Therefore, compliance each year with existing standards in the United States (OSHA Reg. 29 CFR 1910.147) and Canada (CSA Z460) prevents an estimated 120 fatalities and 50,000 electrical injuries for affected employees. Electrical workers injured on the job from exposure to hazardous energy (arc flash) lose on average 24 work days for recuperation. In a study conducted by the United Auto Workers (UAW), 20 per cent of fatalities from electrocution (83 of 414) that occurred among their members between 1973 and 1995 were attributed to inadequate hazardous energy control procedures.

All sources of electricity that have the potential to be unintentionally activated, started or released must be identified and monitored. This is accomplished by installing locks on electrical circuits to keep electricity from being accidentally activated when it shouldn’t be. OSHA occupational safety and heath standards mandate lockout tagout with OSHA Regulation 29 CFR, Part 1910.147 standard: “The Control of Hazardous Energy and “This standard covers the servicing and maintenance of machines and equipment in which the unexpected energization or start up of the machines or equipment, or release of stored energy could cause injury to employees”.

In general, this standard requires that a source of energy for equipment be turned off, isolated (disconnected), and physically locked out using isolation devices. Bleeding, relieving, or blocking other stored and residual energy must also be done to achieve zero energy state using a safety device. The last important function before equipment service can begin is to verify all energy has been deenergized and/or isolated.

OSHA states that all employers must have an Energy Control Program, and that "the employer shall establish a program consisting of energy control procedures, employee training, and periodic inspections to ensure that before any employee performs any servicing or maintenance on a machine or equipment where the unexpected energizing, start up or release of stored energy could occur and cause injury, the machine or equipment shall be isolated from the energy source, and rendered inoperative."

Energy Control Plan
A company's hazardous energy control plan is designed to protect workers and must specifically outline the scope, purpose, authorization, rules, and techniques to be utilized for the control of hazardous energy.

The plan must also include a company's methods to enforce compliance according to osha requirements. At a minimum, the following steps must be taken:

  1. A specific statement of the intended use of your procedures
2. Specific procedures to shut down, isolate, block and secure machines or equipment
3. Specific procedures to place, remove and transfer devices
4. Assigning responsibility for devices
5. Requirements and procedures to test machines and machinery to determine and verify the effective energy isolating device, and other energy control measures.


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