Lockout-tagout - Wikipedia, The Free Encyclopedia


Lockout-tagout (LOTO) or Lock and Tag is a safety procedure which is used in industry and research settings to ensure that dangerous machines are properly shut off and not able to be started up again prior to the completion of maintenance or servicing work. It requires that hazardous energy sources be "isolated and rendered inoperative" before work is started on the equipment in question. The isolated power sources are then locked and a tag is placed on the lock identifying the worker who has placed it. The worker then holds the key for the lock ensuring that only he or she can start the machine. This prevents accidental startup of a machine while it is in a hazardous state or while a worker is in direct contact with it.

Lockout-tagout is used across industries as a safe method of working on hazardous equipment and is mandated by law in some countries.

Group lockout

When two or more workers are working on different parts of a larger overall system, the locked-out device is first secured with a folding scissors clamp that has many padlock holes capable of keeping it closed. Each worker applies their own padlock to the clamp. The locked-out device cannot be activated until all workers have signed off on their portion of the project and removed their padlock from the clamp.

In the United States a lock selected by color, shape or size (e.g. red padlock) is used to designate a standard safety device, locking and securing hazardous energy. No two keys or locks should ever be the same. A person's lock and tag must only be removed by the individual who installed the lock and tag unless removal is accomplished under the direction of the employer. Employer procedures and training for such removal must have been developed, documented and incorporated into the employer energy control program.

Lockout-tagout in the US, has 5 required components to be fully compliant with OSHA law. The 5 components are: 1. Lockout-Tagout Procedures 2. Lockout-Tagout Training (for authorized employees and affected employees) 3. Lockout-Tagout Policy (often referred to as a program) 4. Lockout-Tagout Devices and Locks 5. Lockout-Tagout Auditing - Every 12 months, every procedure must be reviewed as well as a review of authorized employees 

Hazardous energy and its isolation

Modern machinery can contain many hazards to workers, examples of the most common risks are:

  1. Electricity

  2. Hydraulic pressure (line)

  3. Hydraulic accumulation (pump)

  4. Pneumatic compressed air

  5. Gas

  6. Steam

  7. Thermal

  8. Gravity

  9. Kinetic spring tension

  10. Many types of fluids (chemical, water, etc.)

For example, an average industrial device may contain things such as hot fluids, moving presses, blades, propellers, electrical heaters, conveyor belts with pinch points, moving chains, ultraviolet light, etc.

Disconnecting or making safe the equipment involves the removal of all energy sources and is known asisolation. The steps necessary to isolate equipment are often documented in an isolation procedure or a lockout tagout procedure. The isolation procedure generally includes the following tasks:

  1. announce shut off

  2. Identify the energy source(s)

  3. Isolate the energy source(s)

  4. Lock and Tag the energy source(s)

  5. Prove that the equipment isolation is effective

The locking and tagging of the isolation point lets others know not to de-isolate the device. To emphasize the last step above in addition to the others, the entire process can be referred to aslock, tag, and try (that is, try to turn on the isolated equipment).

The National Electric Code states that a safety/service disconnect must be installed within sight of serviceable equipment. The safety disconnect ensures the equipment can be isolated and there is less chance of someone turning the power back on if they can see the work going on. These safety disconnects usually have multiple places for locks so more than one person can work on equipment safely.

In industrial processes it can be difficult to establish where the appropriate danger sources might be. For example, a food processing plant may have input and output tanks and high temperature cleaning systems connected, but not in the same room or area of the factory. It would not be unusual to have to visit several areas of the factory in order to effectively isolate a device for service (e.g., device itself for power, upstream material feeders, downstream feeders and control room).

Modern safety manufacturers provide a range of isolation devices specifically designed to fit various switches, valves and effectors. For example, most modern circuit-breakers have a provision to have a small padlock attached to prevent their activation. For other devices such as ball or gate valves, plastic pieces which either fit against the pipe and prevent movement, or clam-shell style objects, which completely surround the valve and prevent its manipulation are used.

A common feature of these devices is their bright color, usually red to increase visibility and allow workers to readily see if a device is isolated. Also, the devices are usually of such a design and construction to prevent it being removed with any moderate force. (That is to say that an isolation device does not have to stand up to a chainsaw, but if an operator forcibly removes it, it will be immediately visible that it has been tampered with).

To protect one or more circuit breakers in an electrical panel a lockout tagout device called the Panel Lockout can be used. It keeps the panel door locked and prevents the panel cover from being removed. The circuit breakers remain in the off position while electrical work is done.