- Test-before-touch: prove the tester, prove dead, prove the tester again.
- A tag alone is a warning; a lock is the control. Every person working carries their own lock.
- Stored energy — capacitors, springs, pressure, gravity, standby generation — is isolated too.
Lockout/tagout exists because the most dangerous moment on any electrical job is the one where everyone assumes someone else isolated it. The procedure below is written for low-voltage panels and follows the control-of-hazardous-energy sequence used internationally.
Work on electrical installations is governed by the Occupational Health and Safety Act 85 of 1993 and its Electrical Machinery Regulations, which require that machinery is made safe and that only competent persons work on it.[1][2] Installations themselves must comply with SANS 10142-1.[3]
The sequence
Isolate, prove, work, restore
Identify every energy source feeding the equipment, including backfeed from UPS, inverters, standby generation and control supplies from another board. Notify affected persons before switching. The five safety rules of EN 50110-1 order the whole operation: disconnect, secure against re-connection, verify absence of voltage, earth and short-circuit where required, protect against adjacent live parts.[4]
Field checklist
Common questions
What is test-before-touch?
Prove the tester on a known live source, prove the circuit dead, then prove the tester again. A tester that failed silently between the first and second step would otherwise have told you exactly what you hoped to hear.
Is a tag enough to isolate a panel?
No. A tag is a warning; a lock is the control. Every person working on the equipment applies their own lock, so the last person out is the last lock off.
What counts as stored energy?
Capacitors, springs, pressure, gravity and standby generation. Opening the incomer removes the supply, not the energy already held in the system, so each store is isolated and discharged in its own right.
How should equipment be re-energised?
As a controlled sequence: the work is complete and inspected, people and tools are clear, locks are removed by their owners only, and the equipment is re-energised and functionally confirmed before it is handed back.
Sources for every claim above
Each footnote in the article links here. Standards are cited by designation so you can verify the current edition with the issuing body.
- [1]Occupational Health and Safety Act 85 of 1993Republic of South Africa · Department of Employment and Labour · 1993View source
- [2]Electrical Machinery Regulations, 2011 (OHS Act)Department of Employment and Labour · Republic of South Africa · 2011View source
- [3]SANS 10142-1 — The wiring of premises: Low-voltage installationsSABS · South African Bureau of Standards · current editionView source
- [4]EN 50110-1 — Operation of electrical installations: General requirementsCENELEC · European Committee for Electrotechnical Standardization · 2013View source
- [5]ISO 14118:2017 — Safety of machinery: Prevention of unexpected start-upISO · International Organization for Standardization · 2017View source
- [6]29 CFR 1910.147 — The control of hazardous energy (lockout/tagout)OSHA · US Occupational Safety and Health Administration · currentView source
- [7]NFPA 70E — Standard for Electrical Safety in the WorkplaceNFPA · National Fire Protection Association · 2024View source
- [8]IEC 60364-6 — Low-voltage electrical installations: VerificationIEC · International Electrotechnical Commission · 2016View source