Lockout/tagout: How to identify a machine's energy sources, and when to use the ‘Left-Hand Rule’

A critical step in the lockout/tagout process is shutting off the energy isolating devices – switches, valves, and electrical disconnects on machines – to stop the transmission of energy, and securing them in the off position using personally controlled locks. This prevents the machine from activating and harming workers during cleaning, repair, set up, or unjamming.

Machines can be powered by a variety of energy sources. “People authorized to do lockout/tagout need to identify all energy sources associated with equipment, understand the hazards they present, know how to isolate and secure them in their de-energized state, and verify that they have been effectively controlled,” says Rob Vomiero, WSPS Specialized Consultant (Machine and Robotics Safety). “Workplace injuries have occurred, and continue to occur, because people failed to properly control hazardous energy, and bring the equipment to a zero-energy state,” says Rob.

Arc flashes and the ‘Left-Hand Rule’

“In rare cases, switching off an electrical disconnect device prior to applying a lock and tag can result in an arc flash incident,” explains Rob. An arc flash is a sudden and intense explosion of energy within an electrical panel. “Sometimes, the panel will not contain the arc flash and the panel door will explode outward. Someone standing in front could be subjected to intense flames, heat, and even shrapnel, resulting in severe injuries.”

When isolating an electrical energy source, it’s important to use a technique known as the ‘Left-Hand Rule.’

The ‘Left-Hand Rule’ is a best practice that provides and additional measure of safety if an arc flash incident occurs. It helps to protect the person from injury or reduces the severity of injury if it does occur. Rob explains how the rule works. “The person doing the lockout usually stands to the right of the panel and uses their left hand to switch off the disconnect switch (which is generally on the right-hand side of the panel). That way if there is an arc flash and the door explodes outward, the person’s body would not be in the direct path of the arc flash explosion.

“The person should also turn their face away from the panel, usually to the right, and hold their breath as they switch off the disconnect. This reduces the chance of their face being struck directly by arc flash flames and debris, and of inhaling hot fumes and gases. This Left Hand Rule, in addition to appropriate personal protective equipment (PPE), provides an additional layer of risk reduction from an arc flash event.”

Types of hazardous energies that power equipment

As part of your lockout/tagout program, you also need to identify and develop procedures for isolating other forms of hazardous energy that power machines. These include:

Hydraulic energy – energy stored within a pressurized liquid and used to move heavy objects, machinery, or equipment. Examples include: automotive car lifts, injection moulding machines, power presses, and braking systems in cars.
Pneumatic energy – energy stored within pressurized air. Pneumatic systems are generally powered by compressed air to power equipment. Examples include: robotic part grippers, spraying devices, power washers, rock drills, and riveters.
Chemical energy – the energy released when a substance undergoes a chemical reaction. The energy is normally released as heat but could be released in other forms, such as pressure.
Thermal energy – energy from an explosion, flame, objects with high or low temperatures, or radiation from heat sources, such as radiators or portable electric heaters.
Radiation energy – energy related to ionizing, non-ionizing, low-frequency electromagnetic, optical, or radio-frequency electromagnetic radiation. Examples of radiation sources in the workplace are X-rays, microwaves, sunlight, arc welding and mercury vapour lamps.
Potential energy – the energy contained in an elevated object due to the force of gravity, or an item under tension. For instance, a spring that is compressed or coiled will have stored energy which will be released in the form of movement when the spring expands.
Kinetic energy – this is the energy of an object in motion. An example is a flywheel or other mechanical element that requires time to decelerate before coming to a full stop upon receiving a stop signal.

Perform a risk assessment to identify hazardous energies

The risk assessment process, as outlined in CSA Z460:20 Control of Hazardous Energy – Lockout and Other Methods, is the first step in the development of your equipment-specific lockout/tagout procedure, says Rob.

“The risk assessment enables you to identify the hazardous forms of energy associated with the equipment and determine if the equipment has the appropriate isolation devices to switch-off, isolate, and dissipate each form of hazardous energy feeding the equipment.”

Use these tips during the risk assessment to help identify the type of energy a machine uses, and to determine if the appropriate means to control each form of energy exists on the machine.

Observe the machine as it operates, taking note of what goes in, what comes out, and the tasks it performs, to determine its energy requirements.
Examine the machine’s components, such as motors, gears, and mechanisms, for clues about the type of energy being used.
Ensure the machine has an energy isolation device for each form of energy you have identified.
Look for energy storage. Some machines store energy in various forms, such as batteries (chemical energy), capacitors or uninterruptible power sources (UPSs) (electrical energy) or springs, compressed air, elevated loads (potential energy), etc.
Determine the magnitude of the energy sources. Look for labels, nameplates, analogue or digital gauges, etc., that show the magnitude of the various energy sources that feed the equipment. It is important to indicate these on the lockout/tagout procedure.
Review the manufacturer’s specifications, and other machine-related documentation to determine the type of energy used.

“Ultimately, the risk assessment process will enable workplaces to develop safe work procedures for locking out each piece of equipment, with instructions for switching-off, locking/tagging out, and controlling or dissipating all hazardous forms of energy for a machine or process.”

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The information in this article is accurate as of its publication date.

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