LOTO Procedures: What They Are, How to Apply Them, and What Regulations Require
In industrial maintenance, the most serious accidents don't happen when machinery fails. They happen when someone intervenes on a machine that should be stopped and isn't. A valve that didn't close completely. A capacitor that remains charged. A pneumatic actuator with residual pressure. Energy that no one saw coming.
The LOTO procedure — Lockout-Tagout — exists precisely to eliminate that uncertainty. It is not a documented formality or a Health and Safety checklist. It is a control system for hazardous energies that, when properly implemented, turns a maintenance intervention into a predictable, traceable, and safe process.
In this article, we explain what LOTO procedures are, how they are applied step-by-step, what devices they require, what Spanish regulations say, and what implementation errors continue to cause accidents in plants across Spain.
What is the LOTO procedure: technical definition and real-world scope
The LOTO (Lockout-Tagout) procedure is a structured system for controlling hazardous energy, the objective of which is to ensure that any equipment or machine to be worked on is in a zero-energy state before anyone accesses its dangerous areas.
The concept of zero energy is not the same as turning off a machine. A switched-off machine can still store electrical energy in capacitors, pressure in hydraulic or pneumatic circuits, heat in surfaces or fluids, mechanical tension in compressed springs, or gravitational energy in suspended parts. The LOTO procedure acts on all of these sources, not just the main switch.
The system covers six types of energy:
- ElectricVoltage in circuits, capacitors or transformers
- HydraulicsResidual pressure in fluid circuits
- Pneumaticscompressed air stored in tanks and pipes
- Thermaltemperature on surfaces, fluids or processes
- Chemistry: products present in pipes or reactors
- Gravitational / Mechanical: suspended parts, preloaded springs or elements with inertia.
A correctly designed LOTO procedure identifies each of these energy isolation points on each machine, defines the exact sequence of locking and tagging, and establishes who, when, and how verifies that a zero-energy state has been achieved.
Es obligatorio aplicar el sistema LOTO cuando se realiza mantenimiento, reparación, limpieza o cualquier otra actividad que implique el acceso a maquinaria o equipos peligrosos.
The mandatory nature of the LOTO system in Spain is not discretionary. It applies in any situation where a worker needs to access a dangerous area of a machine to carry out maintenance, repair, adjustment, cleaning, lubrication, inspection, or unblocking of jams.
To put it bluntly: if the machine can move, be energised, or release stored energy while someone is working on it or nearby, the LOTO procedure is mandatory.
The highest-risk situations requiring its implementation include:
- Interventions on electrical panels or drive systems
- Press, injection moulding machine, industrial robot or production line maintenance
- Work on hydraulic or pneumatic systems under pressure
- Access to areas protected by guards that must be removed
- Cleaning of equipment in the food, chemical or pharmaceutical industry
- Interventions in installations with multiple simultaneous energy sources
Companies that do not have a documented and trained LOTO programme assume a double risk: the actual risk of an accident and the legal risk arising from non-compliance with regulations.
Here is the step-by-step procedure for LOTO:1. **Preparation:** * Identify all energy sources and their isolation points. * Inform all affected employees about the LOTO procedure that is about to take place. * Determine the type of energy (electrical, mechanical, hydraulic, pneumatic, thermal, chemical, etc.).2. **Notification:** * Notify all affected employees that the machine or equipment will be shut down and that the Lockout/Tagout procedure will be applied.3. **Shutdown:** * Bring the machine or equipment to a complete stop using the normal shutdown procedures.4. **Isolation:** * Locate and operate the isolating devices (e.g., circuit breakers, disconnect switches, valves) to isolate the machine or equipment from its energy source(s).5. **Lockout/Tagout Application:** * Apply lockout devices (locks) and tagout devices (tags) to each energy isolating device. * The lock should be applied by the authorized employee and should be unique to them. * The tag should clearly identify the employee and the reason for the lockout.6. **Verification of Isolation:** * Attempt to operate the machine or equipment to ensure that it cannot be started. This can include attempting to energise the circuits and then de-energizing them, or by checking for residual energy.7. **Restoring Energy (if necessary for testing):** * If testing is required, ensure that all stored energy has been dissipated. * Only release the lockout/tagout devices temporarily to restore energy for testing and reapply them immediately after testing.8. **Release from LOTO:** * Ensure that all tools and materials have been removed from the work area. * Ensure that all employees have been removed from the hazardous area. * Remove the lockout/tagout devices. * Notify affected employees that the LOTO procedure is complete and that the machine or equipment is ready to be restarted. * Restart the machine or equipment using the normal operating procedures.
The sequence for applying lockout and tagging follows a strict order. Altering it – even by a single step – compromises the safety of the procedure.
1. Machine identification and its power sources
The sequence for applying lockout and tagging follows a strict order. Altering it – even by a single step – compromises the safety of the procedure.
2. Notification to affected staff
Operators and supervisors are hereby informed that the machine will be locked out. This is a critical coordination step in environments with multiple shifts or when the machine is shared by different teams.
3. Controlled shutdown of the machine
The machine is stopped following the established safe shutdown procedure. It's not just a matter of pressing the stop button: the steps that avoid dangerous intermediate states must be followed.
4. Isolation of all energy sources
All identified isolation points are acted upon: electrical isolators, hydraulic or pneumatic shut-off valves, thermal or chemical valves, mechanical locking devices. Each isolation point is physically locked out.
5. Lockout and Tagout Device Placement
A safety padlock of the worker performing the intervention is placed on each locked isolation point, along with the corresponding danger tag. If several workers are involved, each one places their own padlock. No one can remove another person's padlock.
6. Dissipation of residual energies
Stored energy is removed or neutralised: residual electrical energy is discharged, pressure is bled from pneumatic and hydraulic circuits, suspended parts are stabilised, and cooling is allowed if there is thermal energy. This step is one of the most frequently omitted and one of the most critical.
7. Zero Energy State Verification
Before intervening, the worker actively verifies that the machine is in a zero-energy state: they attempt to start it, check for the absence of voltage, pressure, or temperature with instrumentation, and confirm that no actuator can move.
8. Execution of the work
With the verification completed, the safe maintenance intervention is carried out under controlled conditions.
9. Restoring power
Once the work is complete, tools and personnel are removed from the hazardous areas. Lockout and tagout devices are removed in the reverse order of their application. Power is restored in a controlled manner.
Here is the step-by-step procedure for LOTO:1. **Preparation:** * Identify all energy sources and their isolation points. * Inform all affected employees about the LOTO procedure that is about to take place. * Determine the type of energy (electrical, mechanical, hydraulic, pneumatic, thermal, chemical, etc.).2. **Notification:** * Notify all affected employees that the machine or equipment will be shut down and that the Lockout/Tagout procedure will be applied.3. **Shutdown:** * Bring the machine or equipment to a complete stop using the normal shutdown procedures.4. **Isolation:** * Locate and operate the isolating devices (e.g., circuit breakers, disconnect switches, valves) to isolate the machine or equipment from its energy source(s).5. **Lockout/Tagout Application:** * Apply lockout devices (locks) and tagout devices (tags) to each energy isolating device. * The lock should be applied by the authorized employee and should be unique to them. * The tag should clearly identify the employee and the reason for the lockout.6. **Verification of Isolation:** * Attempt to operate the machine or equipment to ensure that it cannot be started. This can include attempting to energise the circuits and then de-energizing them, or by checking for residual energy.7. **Restoring Energy (if necessary for testing):** * If testing is required, ensure that all stored energy has been dissipated. * Only release the lockout/tagout devices temporarily to restore energy for testing and reapply them immediately after testing.8. **Release from LOTO:** * Ensure that all tools and materials have been removed from the work area. * Ensure that all employees have been removed from the hazardous area. * Remove the lockout/tagout devices. * Notify affected employees that the LOTO procedure is complete and that the machine or equipment is ready to be restarted. * Restart the machine or equipment using the normal operating procedures.
A LOTO program without the correct devices is a waste of paper. Material equipment is the tangible part of the system and must be sized according to the reality of each installation.
Industrial safety padlocks: For LOTO use only, not to be reused for other purposes. Each worker has their own with a unique key. They are available in various formats and sizes depending on the type of isolation device.
Hasps and specific locking devices They allow electrical disconnect switches, ball valves, gate valves, circuit breakers, and other items that do not directly accept a padlock to be locked out. They must be specific to each type of isolation point.
Group lock boxes In interventions with multiple workers, they allow each operator to place their personal lock on a master key that controls access to the equipment. They ensure that power re-establishment only occurs when all workers have removed their lock.
Standardised hazard labels Indicate who placed the block, for what reason and when. They must not be removed or ignored under any circumstances. Their format must follow the requirements of the applicable regulation.
Lockout devices for pneumatics and hydraulics: Pipe-locking clamps, valve lockouts with hasps, pressure retention devices. Fluid circuits have peculiarities that distinguish them from electrical lockout and require specific devices.
LOTO Station In installations with a mature LOTO programme, devices are organised into lockout stations by machine or by area, with the specific procedure visible and accessible to any authorised worker.
How does Grupo TICE work on the implementation of the LOTO system in Spain
Implementing a LOTO program from scratch – or remediating one that exists but isn't working – requires fieldwork. It cannot be done from an office or with standard templates that do not reflect the reality of the facility.
At Grupo TICE, the implementation process follows a structured methodology:
Technical visit and machinery inventory
The first step is to understand the actual installation. We identify all the machines and equipment requiring LOTO procedures, their technical characteristics, and their power sources. We do not work from manufacturer documentation that may not reflect the current state of the equipment.
Analysis of energy isolation points
For each machine, we identify and document all isolation points: disconnectors, valves, switches, vents, mechanical locking devices. Each point is georeferenced on the equipment's plan and uniquely numbered.
Writing specific LOTO procedures
We develop the specific procedure for each machine: lockout sequence, necessary devices, zero-energy verification, responsible parties, and records. The procedures are delivered in a visual format, with photographs of the actual action points, so they can be used directly on the plant floor.
Selection and supply of devices
We define the right kit of devices for each installation: types of locks, specific hasps, standardised tags, group lockout boxes, and LOTO stations.
Worker training
We provide practical on-site training, using the actual procedures and real equipment from the installation. The training includes assessment and is individually documented to meet regulatory requirements.
Audit and monitoring
Once the programme is implemented, we carry out periodic audits to verify compliance and update procedures when the installation changes.
If you need to assess the LOTO status at your facility, you can consult our service. ISM365 Machinery Safety Inspection or to access more information on our page Industrial safety
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FAQs about the LOTO Procedure
In industrial safety, lockout and tagout are two distinct but complementary procedures used to ensure that dangerous machinery is properly shut off and cannot be started up again before maintenance or servicing work is completed.**Lockout** refers to physically preventing a piece of equipment from being operated. This is typically done by attaching a lock to the energy-isolating device (like a circuit breaker or a valve) that controls the power or other energy source to the machine. The key to this lock is held only by the authorized person performing the work.**Tagout**, on the other hand, involves placing a tag on the energy-isolating device that warns employees that the equipment is being repaired and should not be operated. This tag indicates who applied it and why. While tagout provides a warning, it doesn't physically prevent operation in the same way a lock does. A tag can be removed by someone other than the person who applied it, potentially leading to an unsafe situation if the work is not yet complete.**The Key Difference:*** **Lockout is about physically preventing activation.** It uses a lock to ensure the energy source remains off.
* **Tagout is about warning and identification.** It uses a tag to inform others about the status of the equipment.In practice, **lockout/tagout (LOTO)** is usually used together. The lockout device physically secures the equipment, and a tag is attached to the lockout device to provide further information and reinforce the warning. This combined approach is the most effective way to manage hazardous energy during maintenance and servicing.
The Lockout (lockout) consists of the installation of a physical device — normally a padlock — which prevents the activation of the power source. The Tagout (Lockout Tagout) is the placement of a warning tag indicating that equipment is out of service and should not be activated.
The key difference is in the level of actual protection. Lockout is physically superior: a padlock prevents activation even if someone tries to. A tag only warns, but does not prevent. Regulations, including EN 17975, state that lockout must always be applied when the isolation point allows for it. Tagout is only permitted when the equipment design makes it impossible to install a physical locking device.
How many locks should a worker have in a LOTO procedure?
Each worker involved with the machine must place their own personal lockout device on each isolation point, or in the group lockout box if that system is used. There is no shared lockout in a proper LOTO procedure.
This rule ensures that no worker can be exposed to re-energised energy without their express consent. Removal of the lock is the act by which the worker certifies that they have finished their work and that the area is clear of personnel.
How often do LOTO procedures need to be updated?
Procedures must be reviewed and updated whenever a modification is made to the machine or installation that affects its energy sources or isolation points. As a general rule, an annual review of all procedures is recommended to verify that they remain valid.
Workers' training must be renewed periodically and whenever a new worker who must apply LOTO is incorporated, or when it is detected that a procedure is not being correctly applied on the factory floor.
Is the LOTO procedure mandatory in all industrial sectors?
The LOTO procedure applies in any sector where work equipment that can release hazardous energy is used during maintenance operations. This includes, among others, manufacturing, automotive, food and beverage, chemical, logistics, energy, and construction industries.
There is no sectoral exemption. The obligation is determined by the presence of hazardous energies, not the sector of activity.
What happens if a worker cannot find the LOTO procedure for a machine?
If there is no specific LOTO procedure for that machine, the intervention should not begin until one has been prepared and validated. Working without a documented procedure transfers responsibility to the worker who improvises and to the company that has failed in its obligation to provide one.
The correct procedure is to stop planning the intervention, notify the HSE or maintenance manager, and draw up the procedure before proceeding.
Can LOTO be applied to equipment with multiple simultaneous energy sources?
Yes, and in fact, it's one of the most common scenarios on the shop floor. For equipment with multiple energy sources – for instance, an industrial robot with electric drive, pneumatic system, and hydraulic components – the LOTO procedure must identify and lock out each source separately, in the established order.
For these teams, group lockout boxes are particularly useful: they allow for managing the complexity of multiple isolations with centralised access control, ensuring all points are locked out before anyone enters the hazardous area.
