What Is LOTO? Lockout Tagout Procedures

Lockout Tagout (LOTO) is a safety procedure that ensures hazardous energy sources are properly isolated and de-energized before maintenance, repair, or inspection work begins on equipment and piping. LOTO prevents unexpected startup, release of stored energy, or exposure to hazardous substances that could injure workers.

OSHA 29 CFR 1910.147 (The Control of Hazardous Energy) mandates LOTO procedures in the United States. Equivalent regulations exist worldwide (e.g., EU Machinery Directive 2006/42/EC, UK Provision and Use of Work Equipment Regulations).

Types of Hazardous Energy

Energy Type	Source Examples	Isolation Method
Electrical	Motors, switchgear, transformers, power cables	Circuit breakers, disconnect switches locked open
Mechanical	Rotating shafts, gears, springs, flywheels	Mechanical blocks, shaft locks, spring restraints
Hydraulic	Hydraulic cylinders, accumulators, pumps	Valves locked closed, accumulators bled, lines depressurized
Pneumatic	Compressed air, instrument air, nitrogen systems	Valves locked closed, lines vented to atmosphere
Chemical	Process fluids, flammable gases, toxic substances	Valves locked closed, lines drained/purged, blinds installed
Thermal	Steam, hot oil, heated equipment	Steam valves locked closed, systems cooled, thermal hazard warnings
Gravitational	Suspended loads, elevated components, counterweights	Mechanical blocks, safety pins, supports
Stored (residual)	Pressurized vessels, capacitors, springs	Depressurize, discharge, block

LOTO 6-Step Procedure

Step	Action	Details
1. Preparation	Identify all energy sources	Review P&IDs, electrical drawings, and equipment manuals to identify every energy source
2. Notification	Inform all affected personnel	Notify operators, nearby crews, and control room of the planned isolation
3. Shutdown	Stop the equipment normally	Follow standard shutdown procedures; do not emergency-stop unless required
4. Isolation	Apply energy-isolating devices	Close valves, open disconnects, insert blinds (spectacle blinds), de-energize circuits
5. Lockout/Tagout	Apply personal locks and tags	Each worker applies their own padlock and tag to each isolation point; multi-lock hasps for group LOTO
6. Verification	Verify zero energy state	Attempt to start equipment; check pressure gauges read zero; test for voltage with a meter; verify gas-free with a detector

Common Mistake

Relying on tagout alone without lockout. OSHA 1910.147 requires that energy-isolating devices capable of being locked must be locked. Tags are warning devices only—they do not physically prevent re-energization. A tag without a lock is insufficient protection.

Key OSHA Requirements (29 CFR 1910.147)

Requirement	Detail
Written procedure	A documented, equipment-specific LOTO procedure for each machine or system
Authorized employees	Only trained and authorized workers may apply or remove LOTO devices
Personal locks	Each authorized employee applies their own lock; no one else may remove it
Periodic inspection	Annual review of each LOTO procedure; documented with inspector name and date
Training	Initial and refresher training for authorized, affected, and other employees
Shift transfer	Orderly transfer of LOTO responsibility when shifts change
Group LOTO	Multi-lock hasps or group lockbox when multiple workers are involved

LOTO in Piping Systems

For piping maintenance, LOTO often involves:

• Closing and locking gate valves or ball valves at isolation boundaries
• Installing spectacle blinds or spade blinds for positive isolation
• Draining and depressurizing the isolated section
• Verifying zero pressure at drain points or vent valves
• Gas testing for LEL, O2, and H2S before entry into the isolation zone

Pro Tip

Double block and bleed (DBB) isolation—closing two valves in series with a vent between them—is the minimum standard for positive isolation in most oil and gas facilities. Single valve isolation is generally insufficient for maintenance LOTO in hydrocarbon service.

LOTO is typically managed under the site Permit to Work (PTW) system, with the isolation certificate attached to the work permit.

Read the full guide to LEL/UEL and flammable gas safety