Permit-to-Work and Lockout/Tagout (LOTO)
How permits control high-risk work, and how isolation with locks and tags prevents unexpected release of hazardous energy.
Why it matters
Many serious injuries happen when equipment starts up or energy is released during maintenance. PTW and LOTO are the systems designed to stop that.
Who it's for: Maintenance staff, supervisors, permit issuers and contractors.
Learning objectives — by the end you can:
- Describe the roles in a permit system: issuer, receiver, authoriser.
- List the main LOTO steps from preparation to restoration.
- Explain why 'try' / verification of zero energy is essential.
Key terms
- Permit-to-work (PTW)
- A formal written system authorising specific high-risk work under defined controls.
- Hazardous energy
- Electrical, mechanical, hydraulic, pneumatic, chemical, thermal or stored energy.
- Isolation
- Separating equipment from all energy sources.
- Personal lock
- A lock applied by each worker; only they hold the key.
Lesson notes
LOTO sequence (general)
- 1Prepare: identify all energy sources from drawings and site knowledge.
- 2Notify affected people.
- 3Shut down using normal stop.
- 4Isolate every energy source.
- 5Apply personal locks and tags.
- 6Release or restrain stored energy (bleed, block, discharge).
- 7Verify zero energy — try to start, test for voltage with a proven tester.
- 8Do the work.
- 9Restore: clear tools and people, remove locks in the agreed order, notify.
PTW essentials
A permit names the work, location, hazards, isolations, precautions, gas tests if needed, the people involved and the time period. It is handed over at shift change and closed formally. A permit is only as good as the site walk-down behind it.
Limitation
This page is awareness-level. Isolation of electrical or process systems must only be performed by authorised, competent people under your site's procedures.
Video lesson
Video to be added
A verified video from an official or reputable channel has not yet been selected for this topic. The text lesson above covers the full content.
Search YouTube for related videosPractical story: The conveyor that started itself
Fictional teaching example
Situation. A technician cleared a jam on a conveyor after pressing the stop button.
Known facts
- No lock was applied.
- An upstream sensor restarted the conveyor automatically.
- The technician's glove was caught; minor injury.
Decisions
- Site introduced personal locks and a 'try' step.
- Automatic restart circuits added to isolation lists.
Outcome. Near-miss reports on the line rose (good reporting) while injuries fell.
Lessons
- A stop button is not isolation.
- Automated systems can restart.
- Always verify zero energy.
Worked example
Worked example: isolation list for a pump
| Energy | Isolation point | Method | Verified by |
|---|---|---|---|
| Electrical | MCC panel breaker P-12 | Breaker off, personal lock | Voltage test at motor terminal |
| Process fluid | Suction & discharge valves | Closed, chained and locked | Drain valve opened, no flow |
| Stored pressure | Casing | Bleed valve opened | Gauge reads zero |
Practice exercise
List every energy source you would expect on an office paper shredder and how you would isolate it before clearing a jam.
Quiz
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References
- Official guidanceOSHA — Control of Hazardous Energy (Lockout/Tagout)
- Official guidanceHSE (UK) — Permit to work systems
Verify current editions and applicability. Standards are copyrighted; consult licensed copies for exact requirements.
Report an issue with this contentRelated topics
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HIRA: Hazard Identification and Risk Assessment
Break work into activities, identify hazards, rate risk, apply the hierarchy of controls and verify that controls are actually in place.
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JSA / JHA: Job Safety Analysis
Break a job into steps, identify hazards at each step and agree controls before work starts.