2.2 Hazardous Energy Control: Lockout/Tagout and Confined Space Entry

The standard and who it covers

29 CFR 1910.147, The Control of Hazardous Energy, applies whenever servicing or maintenance is performed and unexpected energization, startup, or the release of stored energy could injure someone. It defines three employee roles:

• Authorized employee — locks or tags out equipment in order to service it. Only authorized employees apply personal locks and verify the zero-energy state.
• Affected employee — operates the equipment being serviced, or works in the area where the servicing occurs. They must be notified before lockout begins and after it is removed.
• Other employee — anyone whose work may take them into an area where energy control procedures are used.

Energy isolating device versus control circuit device

This distinction produces assessment items every cycle. An energy isolating device is a mechanical device that physically prevents the transmission or release of energy.

A control circuit device operates through pilot voltage or software. A welded contactor, a shorted conductor, or a logic fault can bypass it, so OSHA does not accept it as the isolation point.

The six steps of 1910.147(d), in order

OSHA's application of control paragraph lists the sequence. Learn it exactly:

1. Preparation for shutdown — identify the type and magnitude of every energy source, the hazards, and the means of control. Gather locks, tags, hasps, blinds, and blocks.
2. Machine or equipment shutdown — shut down using the normal operating procedure, in an orderly way that does not create a new hazard.
3. Machine or equipment isolation — operate every energy isolating device so the equipment is physically separated from its energy sources.
4. Lockout or tagout device application — each authorized employee affixes their own lock and durable tag to each isolating device.
5. Stored energy release or restraint — relieve, disconnect, restrain, or otherwise render safe all residual or stored energy.
6. Verification of isolation — confirm the zero-energy state before work begins.

Notification of affected employees is required by 1910.147(c)(9) before controls are applied and after they are removed, but it is not one of the six numbered application steps. Training materials that insert "notify" as step 2 are describing good practice, not the regulatory sequence.

Stored energy: what has to be bled, blocked, or drained

Verification: the try-step and live-dead-live

Verification is step 6, and it has two forms.

For mechanical verification, clear all personnel from the machine's zone of motion, attempt a normal start using the operating controls, confirm nothing moves, and then return the operating controls to the off or neutral position so the machine will not jump when it is eventually re-energized.

For electrical verification, use the live-dead-live method:

1. Test the meter on a known energized source to prove the meter and leads work.
2. Test the target conductors phase to phase and phase to ground, confirming zero voltage.
3. Re-test the meter on the known energized source to prove it did not fail during the measurement.

Group lockout and shift turnover

When a turnaround involves several crafts and dozens of isolation points, 1910.147(f)(3) allows group lockout. A primary authorized employee applies master locks to every isolating device, places the keys in a group lockbox, and locks the box. Every craft worker on the job then adds a personal lock to the lockbox hasp. The box cannot open — and the equipment cannot be re-energized — while any personal lock remains. At shift change, the outgoing worker removes their lock only as the incoming worker applies theirs, so protection is never interrupted.

Permit-required confined space entry

Maintenance mechanics routinely enter vessels, tanks, sumps, and boiler drums. 29 CFR 1910.146 classifies a confined space as permit-required if it contains or has the potential to contain a hazardous atmosphere, contains material that could engulf the entrant, has walls that converge or a floor that slopes to a smaller cross-section, or contains any other recognized serious safety or health hazard.

Atmospheric testing follows a fixed order: oxygen first, then flammable gases and vapors, then toxic gases and vapors. Oxygen is tested first because combustible gas meters and many toxic sensors give unreliable readings in an oxygen-deficient atmosphere. Acceptable oxygen content is 19.5% to 23.5%. Entry requires an attendant stationed outside the space for the duration of the entry, continuous or periodic monitoring per the permit, and a rescue plan that does not rely on the attendant entering.