Knowledge · Fundamentals
What is LOTO (lockout tagout)?
LOTO is not a single action but a sequence of steps with clearly assigned roles. This page explains what it consists of, how a lock differs from a tag, and who takes part in the procedure.
Switching a machine off doesn’t make it free of energy.
What does LOTO stand for?
Short answerLOTO stands for lockout and tagout. It refers to the procedure for controlling hazardous energy when working on machines and equipment.
Lockout means physically securing an energy-isolating device, such as a disconnector or a valve, in a safe position with a lock. Tagout means attaching a tag that warns the equipment must not be operated and states who secured it.
Many plants also use the term LOTOTO, which explicitly adds Tryout – verifying that the isolation is effective. The principle is the same; the difference lies in what the name emphasises. We cover it in detail in LOTO vs. LOTOTO.
Why does hazardous energy control matter?
Short answerBecause a machine that has been switched off is not necessarily free of energy. It can start unexpectedly, and stored or residual energy can be released even after shutdown.
During normal operation, guards, safety circuits and controls protect the operator. During maintenance, those safeguards are often removed or bypassed and the worker is directly inside the danger zone. At that point the only reliable protection is that the energy sources are disconnected and nobody can reconnect them.
Hazardous energy is not only electrical. It includes pressure in hydraulic and pneumatic systems, the momentum of rotating parts, compressed springs, raised loads, hot media and chemicals in pipework. An overview of energy types and how they are isolated is on the energy isolation page.
Residual (stored) energy deserves particular attention. It stays in the equipment after the source is disconnected: in capacitors, pressure accumulators, springs or material held up in a hopper. That is why LOTO also includes releasing or blocking it.
What are the steps of LOTO?
Short answerTypically preparation, notifying affected people, shutting down the equipment, isolating the energy sources, applying locks and tags, releasing residual energy and verification. The exact procedure is defined by the plant for each piece of equipment.
- PreparationIdentify the equipment, its energy sources and isolation points according to the procedure for that equipment.
- NotificationTell the operators and other affected workers that the equipment is being shut down.
- ShutdownStop the equipment in the normal, controlled way.
- IsolationDisconnect every energy source at its isolation point.
- Lock and tagA lock and a tag on every isolation point, usually a personal lock for each worker.
- Release residual energyBleed off pressure, discharge, block moving parts, secure loads.
- VerificationCheck that the isolation is effective and the equipment cannot start. In LOTOTO this step is named Tryout.
Once the work is finished, the reverse sequence follows: inspect the work area, remove tools, notify affected people, remove locks and tags and return the equipment to service. Here, too, it is essential to know whether anyone is still working on the equipment.
What is the difference between a lock and a tag?
Short answerA lock physically prevents anyone from operating the isolating device. A tag only warns and informs; on its own it does not prevent the equipment being switched on.
That is why the two are used together. The lock ensures the disconnector or valve cannot be moved. The tag says why the equipment is secured, who secured it and whom to contact.
In the OSHA technical reference framework, a tag without a lock is accepted only where the isolating device cannot be locked, and then with additional measures that provide equivalent protection. How to proceed in such cases is set by the plant’s internal rules.
A key principle is the personal lock. Every worker exposed to hazardous energy fits their own lock to the isolation point and is the only one who holds its key. Where several people work on the same equipment, group lock boxes or multi-lock hasps are used.
ReadGroup lockoutWho is involved in LOTO?
Short answerMainly the person carrying out the isolation, the workers doing the job, the person approving the work and the operators who need to be informed. The exact roles are set by the plant’s rules.
- Requester – prepares the job and asks for the equipment to be secured.
- Approver – assesses whether the job is ready and gives consent, for example an operator or shift supervisor.
- Isolating person – disconnects and locks a specific energy source. Different energies may be handled by different people, such as an electrician and a fitter.
- Maintenance workers – carry out the job itself, each protected by their own lock.
- Operators and affected people – must know the equipment is shut down and must not start it.
Dividing responsibilities is not a formality. Approving the work, carrying out the isolation and verifying that it is effective are three distinct actions that may be performed by different people.
Which regulations apply to LOTO?
Short answerThe most frequently cited technical framework is the US regulation OSHA 29 CFR 1910.147. In each country, however, the applicable national legislation and the plant’s internal rules apply.
OSHA 29 CFR 1910.147 (The control of hazardous energy) describes an energy control programme: written procedures for equipment, training, the use of locks and tags, release of residual energy, verification of isolation, group lockout and continuity during shift or personnel changes. Many multinational companies base their corporate standards on it.
We refer to it only as a technical reference framework, not as a substitute for local legislation. The specific obligations of your plant follow from the applicable health and safety regulations, the technical standards relevant to the equipment and your organisation’s internal rules. Assessing them is a task for health and safety professionals.
How can digitalisation help?
Short answerDigitalisation does not replace locks or tags. It helps bring information about equipment, energy sources, people and the status of each step into one place.
In practice, LOTO is often spread across a paper permit, a spreadsheet, a phone call and the experience of individual workers. With several trades and shift changes, keeping an up-to-date overview is difficult. A digital process can record who secured which energy and with which lock, and release the next step only once the previous one is confirmed. The “locked” status in an application is a recorded status based on workers’ confirmations, not a measurement of the equipment’s state.
What can be digitalised and what remains a physical task is explained on the digital LOTOTO page.
Frequently asked questions
Is LOTO the same as switching a machine off?
No. Switching off with a control stops the machine but does not disconnect it from its energy source. LOTO requires disconnection at the isolation point, a lock, a tag and verification.
Can someone other than the person who fitted a lock remove it?
The principle is that a personal lock is removed only by the person who fitted it. The exceptional procedure for when that person is unavailable is defined by the plant’s internal rules.
Does LOTO apply to short jobs as well?
Hazardous energy control applies to any job where unexpected start-up or release of energy could occur. Any exceptions are defined by the plant’s rules, not by how long the job takes.
Next step
How does LOTO work in your plant?
We will go through your existing procedure with you and show which parts of it can be managed digitally. The physical tasks and the rules remain yours.