LOTO guide: lockout/tagout of hazardous energies

LOTO stands for Lockout/Tagout. It is the procedure by which, before working on a machine or installation (maintenance, cleaning, clearing a jam, adjustment, changeover), all its energy sources are isolated, the isolating devices are physically locked with a personal padlock and marked with a tag identifying who applied the lockout.

It applies whenever a worker has to expose any part of the body to a hazardous zone of the machine or has to defeat a guard in order to work. It does not replace the machine's safety interlocks: it complements them when these are not sufficient (long interventions, several people, residual energy, remote isolation points).

Electrical energy is the most obvious, but it is rarely the only one. Before locking out, all the sources of each piece of equipment should be inventoried:

• Electrical: disconnect switches, circuit breakers, sockets and plugs, variable speed drives, batteries and capacitors.
• Pneumatic: air supply points, quick-release fittings, ball and isolation valves; air accumulated in pipes and cylinders must be bled off.
• Hydraulic: shut-off valves, pressure accumulators.
• Mechanical: flywheel inertia, compressed springs, suspended loads, gravity.
• Thermal and chemical: steam, hot or corrosive fluids, gases; isolated with valves and blind flanges.

Each source requires an isolation point and a lockout device compatible with that point: this is why the catalogue is organised by type of device (valve, circuit breaker, plug, cable, etc.) and not by sector.

1. Preparation: identify the energy sources, the isolation points and the devices required (ideally in a written procedure for each machine).
2. Notification: inform the workers and managers affected.
3. Shutdown: stop the machine using the normal procedure.
4. Isolation: operate disconnect switches, valves and circuit breakers.
5. Lockout and tagout: fit the device at each isolation point, secure it with the personal padlock and attach the tag.
6. Dissipation of residual energy: bleed off pressure, discharge capacitors, support loads, allow to cool.
7. Verification: attempt to start and check with instruments that no energy is present.
8. Removal: on completion, each worker removes their own padlock after checking that the area is clear; the last one re-energises the machine.

The padlock is the personal element of the system. The usual criteria:

• Body: reinforced nylon (lightweight, insulating, resistant to chemicals and to temperatures from −20 °C to +120 °C) is the standard; aluminium, brass, laminated and long-body versions for writing the name are also available.
• Shackle: chrome-plated steel (general use), stainless steel (damp or corrosive environments), non-conductive nylon (electrical work: prevents current passing from the shackle to the key) or cable (lockout points with narrow or distant holes). Usual lengths: 25, 38 and 76 mm; diameters from 4 to 6.5 mm.
• Keying system: keyed different (KD) for personal padlocks; keyed alike (KA) for one worker with several points; master key (MK) for the person in charge; grand master key (GMK) for plants with several areas. It is advisable to record the combinations so that replacements can be supplied.
• Key retention: the key can only be removed with the shackle closed, so an open padlock is never left without its key.
• Colour and marking: one colour per department or type of energy and the worker's name or number laser-engraved make identification easier.

See the full range in safety padlocks.

When several people are involved, each of them must be able to apply their own padlock. The lockout hasp closes over the isolation point and provides six holes; the point is not released until the last padlock is removed. For installations with many isolation points, the group lock box is used: the person in charge locks out all the points with padlocks from the box, places the keys inside, and each worker locks the box with their personal padlock.

Lockout stations (wall-mounted, portable or in a case) centralise padlocks, hasps, tags and devices by machine or by area, so that the equipment is always to hand and complete. Kits group together a selection of devices for a given type of work (electrical, valve, general).

The tag always accompanies the padlock. It must be legible, resistant to the environment (PVC or similar) and state the worker's name, department, date and reason for the lockout. Write-on tags are used with an erasable marker; custom identification tags carry the worker's photo or details. A tag without a padlock (tagout only) is acceptable only when the isolation point does not allow physical lockout, and with compensatory measures.

• PUWER 1998 (Provision and Use of Work Equipment Regulations, UK) and EU Directive 2009/104/EC on the use of work equipment: maintenance operations must be carried out with the equipment shut down and isolated.
• EN ISO 12100 (general principles for the design of machinery) and EN ISO 14118 (prevention of unexpected start-up), which describe the means of isolating and dissipating energy and locking them.
• Electricity at Work Regulations 1989 (UK): work on or near electrical systems requires them to be made dead, isolated and secured against re-energisation, with suitable signage.
• International references: OSHA 29 CFR 1910.147 (USA) and ANSI/ASSP Z244.1, widely used by multinationals for their internal procedures.

This guide is for guidance only: the risk assessment and the isolation procedure for each installation must be drawn up with the company's health and safety service.