When is lockout/tagout required for electrical work, and what does OSHA require?

Details / How it works

Under 29 CFR 1910.333(b)(2), lockout and tagging procedures must be followed in a specific sequence when any employee is exposed to contact with parts of fixed electric equipment or circuits that have been deenergized. The employer must maintain a written copy of the procedures (paragraph (b)(2)(i)).

Step-by-step procedure:

1. Deenergizing equipment (§ 1910.333(b)(2)(ii)): Safe procedures must be determined before deenergizing. Circuits and equipment must be disconnected from all electric energy sources (e.g., disconnect switch, circuit breaker). Control circuit devices like push buttons may not be used as the sole means.
2. Release of stored energy: Stored electric energy (e.g., capacitors) must be discharged and short-circuited/grounded if it might endanger personnel. Stored non-electrical energy (springs, pneumatic devices) must be blocked or relieved.
3. Application of locks and tags (§ 1910.333(b)(2)(iii)): A lock and a tag must be placed on each disconnecting means, unless a lock cannot be applied (then a tag with an additional safety measure may be used) or the employer demonstrates equivalent safety.
4. Verification of deenergized condition (§ 1910.333(b)(2)(iv)): A qualified person must operate the equipment controls to verify it cannot be restarted and must use test equipment to confirm the circuit elements are deenergized. For circuits over 600 volts, the test equipment must be checked immediately before and after the test.

Numbers & thresholds

Exceptions & edge cases

Exceptions to deenergization requirement

Under § 1910.333(a)(1), live parts need not be deenergized if the employer demonstrates that:

• Deenergizing introduces additional or increased hazards (e.g., interruption of life support equipment, deactivation of emergency alarm systems, shutdown of hazardous location ventilation, or removal of illumination for safety); or
• Deenergizing is infeasible due to equipment design or operational limitations (e.g., testing circuits that can only be performed energized, or work on circuits that form an integral part of a continuous industrial process).

Distinction between lockout and tagout

• If an energy isolating device is capable of being locked out, lockout must be used unless the employer demonstrates that tagout provides full employee protection (§ 1910.147(c)(2)(ii)).
• If a lock cannot be applied (e.g., equipment design limitations), a tag may be used without a lock, but must be supplemented by at least one additional safety measure (e.g., removal of a fuse, blocking a controlling switch, opening an extra disconnecting device) (§ 1910.333(b)(2)(iii)(C)-(D)).

Treatment of equipment not locked/tagged

Conductors and parts of electric equipment that have been deenergized but have not been locked out or tagged must be treated as energized parts, and the energized work practices of § 1910.333(c) apply (§ 1910.333(b)(1)).

Overhead lines

If work is to be performed near overhead lines, the lines must be deenergized and grounded, or other protective measures provided. Unqualified persons must maintain minimum approach distances (10 ft for ≤50 kV, increasing 4 in per 10 kV above 50 kV) (§ 1910.333(c)(3)).