Lockout/Tagout (LOTO)

What is lockout/tagout?

Many serious accidents in maintenance, cleaning, and unclogging occur due to the unexpected start-up of equipment while someone is inside or in contact with it: a coworker resets the machine, an automated system restarts the cycle, a hydraulic accumulator releases pressure, or a suspended load falls. Lockout/tagout addresses this cause with a simple rule: the person performing the operation is the only one who can restore power, because the isolation device is locked and only they have the key.

The tag complements the lock: it identifies the person, the date, and the reason, and warns that the equipment should not be turned on. A system based solely on tags, without a physical lock, is weaker and is only acceptable when the device cannot be locked and equivalent measures are taken.

In the United States, OSHA standard 29 CFR 1910.147 on hazardous energy control defines the procedures, devices, and training, and has given a name and structure to the practice worldwide. In Spain, there is no standard with that name, but the obligation is equivalent: Royal Decree 1215/1997 requires that all work equipment have clearly identifiable devices to isolate it from each of its energy sources, and that maintenance , adjustment, and cleaning operations be carried out with the equipment stopped and de-energized, unless impossible, and with appropriate protective measures. Royal Decree 614/2001 regulates the de-energization and lockout/tagout procedures in electrical installations.

Energies that must be controlled

• Electrical. Main power supply, auxiliary circuits, capacitors, batteries, uninterruptible power supply systems.
• Mechanics. Elements in motion by inertia, flywheels, compressed or tensioned springs.
• Hydraulics and pneumatics. Pressure in circuits, accumulators and cylinders, which can cause movement after the supply is cut off.
• Gravitational. Suspended loads, elevated machine parts, counterweights.
• Thermal. Hot surfaces, steam, fluids at temperature.
• Chemical and process. Fluids in pipes, gases, reactions; require closure, drainage, purging and sometimes blind flange.

The most common mistake is simply cutting off the electricity and forgetting about stored energy or gravity. Each team’s procedure must identify all sources of energy and how to isolate and dissipate each one.

Steps of the procedure

1. Preparation: Identify the equipment, energy sources, isolation devices, and risks of the intervention; inform the affected people.
2. Stop: Stop the equipment using the normal stop procedure.
3. Isolation: activate all energy separation devices (disconnectors, valves, disconnections).
4. Lockout/Tagout: Place personal padlock and tag on each device; with multiple people, use a multi-pin or group lockout box so that each person has their own padlock.
5. Dissipation of residual energy: capacitor discharge, depressurization, lowering or wedging of elevated parts, spring release, cooling, drainage and purging.
6. Verification of absence of energy: attempt to start using the controls, measurement of absence of voltage, check of zero pressure; the equipment must be in a state of zero energy before intervention.
7. Intervention and restoration: upon completion, check that tools and people are out, remove each person’s padlock, notify and restore power using the normal procedure.

Organizational application

• General procedure and equipment sheets. The procedure defines rules, roles, and devices; each team with multiple energy sources needs a sheet with the location of the isolation points and how to dissipate each energy source.
• Devices. Personally identified padlocks, with a single key held by the owner, multiple clamps, group lockout boxes, valve blockers, switches and plugs, standardized labels.
• Authorized and affected personnel. Specific training for those who perform the blockade and for those who work in the area; information for operators to prevent them from attempting to start blocked equipment.
• Shift changes. Clear rule for transferring blocks without leaving the team unprotected.
• Contractors. Coordination so that external personnel apply the same system with their own safeguards; integration with work permits.
• Exceptional removal. Procedure for removing a padlock whose owner is unavailable, with verification that no one is interfering and authorization from a responsible party.
• Periodic audit. Verification that procedures are being followed and that equipment records are up to date.

Limits and common mistakes

1. Cut off only the electrical power supply and forget about hydraulic, pneumatic, stored or gravitational energy.
2. Use the emergency stop or mode selector as isolation; they are not energy separation devices.
3. Sharing padlocks or keys, or using a single padlock for a team of several people.
4. Do not verify the absence of energy before intervening.
5. Remove third-party blocks without an exceptional removal procedure.
6. Apply the lockout in long interventions and omit it in unblocking and short adjustments, where a large part of the accidents occur.

Lockout/tagout does not cover tasks that must be carried out with the equipment running (adjustments, settings, tests); these interventions require safe operating modes provided by the manufacturer, with reduced speed, sensitive control or equivalent devices, in accordance with machine regulations.

Regulatory framework in Spain and international reference

• Royal Decree 1215/1997, Annex I (section 1) and Annex II (section 1) . Clearly identifiable energy separation devices and carrying out maintenance operations with the equipment stopped and without energy.
• Royal Decree 614/2001, Annex II . Work without voltage: voltage suppression, locking of cutting devices, verification of absence of voltage, grounding and signaling.
• Royal Decree 1644/2008 . Marketing and commissioning of machines; insulation and dissipation requirements of energy sources in the design.
• OSHA 29 CFR 1910.147, The control of hazardous energy (lockout/tagout) . US standard of origin of the procedure; international reference not valid in Spain.

Regulation (EU) 2023/1230 on machinery replaces Directive 2006/42/EC, applicable from January 2027, and maintains the requirements for insulation of energy sources in the design. The UNE-EN ISO 14118 standard on prevention of unintentional start-up is the technical design reference.