Nelson & Associates :: Workplace :: Lock-Out / Tag-Out

Lock-Out / Tag-Out

Anyone having to service, adjust, repair, or maintain machinery or equipment may be in grave danger of injury unless it is certain that such machinery and equipment is stopped, de-energized, and cannot be started, re-energized, or otherwise activated during the time such work is being done. It is therefore vital that such machinery and equipment be put into a state in which the possibility of its making any unexpected movement, and thus causing injury to those exposed to such movement, is prevented. The procedure most commonly recognized for this purpose is called "lockout," or "tagout." Basic principles and techniques of lockout have been outlined in the authoritative safety literature and various associated standards for decades.

Proper lockout procedures are not complex, but neither are they intuitive. Workplace management must establish mandatory lockout/tagout policies and procedures, properly train all supervisors and workers regarding the requirement to adhere to such procedures, and strictly enforce their use.

In 1937, the National Safety Council published a Safety Practices Pamphlet (No. 70) for "Maintenance and Repair Men" in which they advocated that (a) no repair work should be started on machinery in motion. Before beginning work, it should be absolutely ascertained that the power cannot be turned on, and stating that (b) many members of the National Safety Council make it a practice to lock the controlling device, preferably by padlock, the key to which is kept by the repairman himself, while (c) other companies have place signs or tags on such machines and prohibit their removal until the supervisor has checked the repairs and OK’d the machine for further use, however, (d) the only safe way is for each repairman to lock, with his own padlock, the switchbox or other connecting device so that no one else can tamper with it.

In 1966, the National Safety Council published, "The ABC’s of Lockouts" (National Safety News, March 1966), in which the following points were made:

  • A lockout device is a mechanism or arrangement that allows the use of key or combination locks (most commonly padlocks) to hold a switch lever or valve handle in the "off" position.

  • A lockout procedure consists of the steps that must be taken by both management and the worker to assure that lockout devices are used, and used properly.

  • Lockout procedures cannot be followed unless lockout devices are provided for the main power controls to all potentially hazardous machinery.

  • In the case of electrically powered machines, the "main power control" is the remote disconnect or breaker, not the push-button controls or switch on the machine itself.

  • Pneumatic, steam, and hydraulic valves should also be provisioned [with a means of lockout]. Caution: When locking out upstream pressure…also locks in downstream pressure – pressure that could result in one unlooked for cycling of the machine…[the solution being the assured bleeding of such pressure before work on such machines is begun].

  • Main electric disconnects and valves must be capable of being simultaneously locked "off" by the padlock of each man who might do hazardous work on the machine or equipment.

  • Locks should be issued to every employee who works on closed-down equipment. No key (or combination) should fit more than one lock.

  • The lock-holder should have only one key. The supervisor or foreman usually keeps duplicate keys for locks under his control, or a master key. But some firms insist on one lock-one key. If emergency requires removal of a lock, bolt cutters are used. Keys and locks should never be loaned.

  • Locks should identify the user by name and badge number.

  • Lockout Procedures:

    • Before any equipment is locked out, there should be agreement as to the specific machine or unit to be taken out of operation.

    • Turn off the point-of-operation controls.

    • Turn the main power controls (switch, breaker, or valve) "off."

    • After the switch has been opened or the valve closed, the person or persons who will be involved in the job snap their locks on the control lever or on a multiple-lock adapter. At this point, it is good practice to tag the locks. Tags can describe the type of work the lock-user is engaged in, how long the job will take, and who his supervisor is.

    • Try the disconnect or valve to make sure it cannot be move to "on."

    • Try the machine controls themselves, as a test that the main controls are really "off."

    • As each employee completes his repair or maintenance work, he remove his own lock and supplemental tag. The man who removes the last lock should notify the foreman that the work is finished and the equipment is ready to go again.

  • Lockout Don’ts:

    • Pulling fuses is not a substitute for locking out.

    • Locking out one source of power to equipment may not be enough. Many machines use a combination of power sources – electric, pneumatic, steam, hydraulic, etc.

    • Employees should not be expected to guess what controls apply to what machines, or to trace piping or wiring to find the correct main controls. All disconnects and valves should be clearly marked.

    • Intermittently operating equipments such as pumps, blowers, fans, and compressors may seem harmless when dormant. Don’t assume that because equipment isn’t functioning, it will stay that way.

    • Perhaps the most difficult mistake to overcome is the assumption by a maintenance man or electrician that the job is too small to merit locking out. Yielding to the temptation to bypass lockout procedures because they seem an unimportant nuisance can cost lives.

While the above remains good practice consistent with current recommendations, see the National Safety Council at and search "lockout" for current programs and publications.

The Department of Labor (OSHA) has also adopted federal requirements (regulations) the require the use of lockout practices in general industry under 29 CFR 1910, Subpart J, 1910.147 titled The Control of Hazardous Energy (Lockout/Tagout) and in construction under 29 CFR 1926, Subpart K, 1926.417 titled "Lockout and Tagging of Circuits" at (click on "Regulations" and then Parts 1910 and 1926).

© Nelson & Associates, 1987, 2000