Lockout and tagout are related but not interchangeable. Lockout physically prevents an energy-isolating device from being operated. Tagout places a warning tag that forbids operation but does not itself restrain the device. Knowing when each applies keeps your program honest — and keeps people out of running equipment.
Lockout — Physical Restraint
Lockout means attaching a lock (typically with a hasp or lockout device) to an energy-isolating device — a disconnect switch, valve, blank flange, or block — so the device cannot be moved to the unsafe position without removing the lock. The authorized employee’s key stays under that employee’s control.
Lockout is the default expectation whenever the energy-isolating device is capable of being locked. Modern disconnects, many valves, and dedicated lockout points are designed for this. If it can be locked, your program should lock it.
Tagout — Warning Only
Tagout means fastening a prominent warning tag to an energy-isolating device. The tag states that the device must not be operated until the tag is removed by the authorized employee (or under documented transfer procedures). A tag does not provide the same physical protection as a lock.
Tagout is used when lockout is not feasible — for example, older equipment whose isolating devices cannot accept a lock, and where your written program documents the tagout procedure and any additional safety measures required by OSHA 1910.147. Tagout is not a convenience substitute for buying the right lockout hardware.
If someone can flip the disconnect with a tag still hanging, you never had lockout. Do not treat a panel sticker or a note on the HMI as tagout.
When Each Applies
| Situation | Prefer | Why |
|---|---|---|
| Disconnect or valve can accept a lock | Lockout (+ tag for identification) | Physical prevention is the standard of care |
| Isolation device cannot be locked; program documents tagout | Tagout + extra measures per program | Feasibility exception — not preference |
| Multiple workers exposed | Group lockout (hasp/lockbox) | Each authorized employee keeps personal control |
| Cord-and-plug equipment under exclusive control | Follow program exception rules | May not require full LOTO if exclusive control criteria are met |
| “We are in a hurry” | Still lockout if capable | Speed is not a feasibility finding |
Full Protection Still Needs the Six Steps
Whether you lock, tag, or both, the rest of the sequence still matters: notify, shut down, isolate every energy type, relieve stored energy, and verify zero energy. A perfect lock on the main breaker with skipped pneumatic dumps is still an incomplete LOTO. Use the interactive LOTO checklist to force the energy-source sub-checks, and read the LOTO guide for when authorization and machine-specific procedures apply.
Practical Shop Example
A hydraulic press brake has a lockable electrical disconnect and lockable hydraulic isolation valves. Correct: lock the disconnect and the hydraulic valves, tag each point with name/date/reason, bleed residual pressure, block the ram if required, then tryout. Incorrect: hang a “Do Not Operate” tag on the operator screen and leave the disconnect unlocked because “everyone knows we are working on it.”
If a 1970s air valve truly cannot accept a lock and your written program authorizes tagout for that device, hang the tag at the valve, apply any required additional measures (removal of the valve handle, blanking, blocking), and still verify zero energy before exposure.
Checklist both methods Mark lock points and tag-only points explicitly, then download completed or blank PDFs.
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