Lockout/Tagout & Hazardous Energy

Learn lockout/tagout fundamentals for controlling electrical, mechanical, hydraulic, pneumatic, chemical, thermal, and other hazardous energy during servicing and maintenance.

Water and wastewater equipment can contain several forms of hazardous energy at the same time. A pump may have electrical power, pressurized water, rotating parts, gravity forces, and stored pressure. A valve actuator may contain electrical, pneumatic, hydraulic, or spring energy. Simply pressing a stop button does not necessarily make equipment safe to service.

Lockout/tagout, commonly called LOTO, is a system for controlling hazardous energy during servicing and maintenance. Its purpose is to prevent unexpected startup, energization, movement, or release of stored energy while employees are exposed to danger.

What Is Hazardous Energy?

Hazardous energy is energy capable of causing injury if it is released unexpectedly or if equipment starts while someone is working on it.

Energy sources encountered in water and wastewater facilities may include:

electrical energy from motors, panels, heaters, controls, and other powered equipment;
mechanical energy from rotating shafts, impellers, belts, gears, mixers, screens, and other moving components;
hydraulic energy from pressurized water, wastewater, oil, or hydraulic systems;
pneumatic energy from compressed air or gas;
chemical energy from pressurized or reactive chemicals;
thermal energy from hot equipment, steam, or heated liquids;
gravity energy from elevated gates, covers, suspended equipment, or components that can fall;
stored energy in springs, capacitors, compressed systems, rotating components, or trapped pressure.

A complete energy-control procedure must address every hazardous energy source associated with the work.

When Lockout/Tagout Is Used

LOTO is generally associated with servicing and maintenance when unexpected energization, startup, or release of stored energy could injure employees.

Examples in water and wastewater operations can include:

working inside or near a pump or mixer;
removing guards to service rotating equipment;
clearing a jammed screen or conveyor;
repairing a valve or actuator;
working on equipment connected to pressurized piping;
performing maintenance where equipment could start automatically;
working beneath equipment or components that could move or fall.

Normal production operation and minor servicing can involve additional regulatory considerations, so operators should follow the facility's established energy-control program rather than deciding independently that LOTO is unnecessary.

Authorized and Affected Employees

OSHA distinguishes between authorized and affected employees.

An authorized employee is a person who applies lockout or tagout controls as part of servicing, maintenance, or energy-control responsibilities.

An affected employee is a person who normally operates or uses the equipment being serviced, or who works in an area where the servicing is taking place.

An affected employee may become an authorized employee when that employee's duties include work covered by the hazardous-energy-control procedure.

Authorized employees require more detailed training because they must recognize energy sources, understand the type and magnitude of energy present, and know how that energy is isolated and controlled.

Stopping Equipment Is Not Energy Isolation

A control switch, push button, selector switch, touchscreen command, or software command may stop equipment, but it generally does not physically isolate the hazardous energy source.

An energy-isolating device is a device that physically prevents the transmission or release of energy. Examples may include:

electrical disconnect switches;
circuit breakers used as energy-isolating devices;
line valves;
blocks or blanks;
other mechanical devices that physically isolate energy.

A normal start-stop button is a control device, not a substitute for required energy isolation.

Basic Lockout/Tagout Sequence

An energy-control procedure should be equipment-specific where required and should address all identified energy sources. A typical sequence includes:

Prepare for shutdown.
Notify affected employees.
Shut down the machine or equipment normally.
Operate the energy-isolating devices.
Apply lockout or tagout devices.
Relieve, restrain, disconnect, or otherwise control stored energy.
Verify that isolation and deenergization are effective.
Perform the servicing or maintenance.
Inspect the work area before restoring energy.
Remove locks or tags according to the procedure.
Notify affected employees and restore equipment to service safely.

The exact sequence and controls depend on the equipment and facility procedure.

Preparation for Shutdown

Before shutting equipment down, the authorized employee must understand the energy involved.

Important questions include:

What energy sources power or affect the equipment?
What is the type and magnitude of the energy?
Where are the energy-isolating devices?
Could energy remain stored after isolation?
Could pressure, liquid, or chemical flow enter from another source?
Could automatic controls restart equipment?
Could gravity or mechanical movement occur after power is removed?

A pump, for example, may require more than opening an electrical disconnect. Isolation may also require controlling suction or discharge pressure, preventing valve movement, and addressing other equipment connected to the system.

Notify Affected Employees

Affected employees should be informed before lockout or tagout controls are applied and after they are removed.

Notification helps prevent another operator from attempting to start equipment, reposition valves, change control modes, or otherwise interfere with the work.

Good communication is especially important in plants with remote controls, automatic equipment, multiple shifts, or several operating areas.

Shutdown and Energy Isolation

Equipment should normally be shut down using the established operating procedure before energy-isolating devices are operated.

After shutdown, every required energy source must be isolated.

Examples may include:

opening an electrical disconnect;
closing and securing process valves;
isolating compressed-air supplies;
disconnecting hydraulic pressure;
blocking equipment against movement;
isolating chemical lines.

Operators should not assume that one isolation point controls every energy source.

Apply Locks and Tags

Lockout physically restrains an energy-isolating device in a safe or off position.

Tagout uses a warning tag to identify that the equipment must not be operated.

OSHA emphasizes that a tag is primarily a warning device. It does not provide the same physical restraint as a lock.

Locks and tags should be identifiable, durable, suitable for the environment, and used only for their intended energy-control purpose.

Control Stored Energy

Isolating the primary energy source does not necessarily eliminate stored or residual energy.

Stored energy may remain in:

pressurized piping;
hydraulic accumulators;
pneumatic lines;
springs;
elevated components;
rotating equipment;
electrical capacitors;
trapped liquid or gas;
equipment subject to gravity.

Potentially hazardous stored or residual energy must be relieved, disconnected, restrained, blocked, or otherwise made safe.

If stored energy can reaccumulate to a dangerous level, its control must continue to be verified during the work.

Verification Before Work Begins

Applying locks is not the final step before maintenance. The authorized employee must verify that the equipment has actually been isolated and deenergized.

Verification may involve actions appropriate to the equipment and energy source, such as:

checking the positions of isolation devices;
attempting a normal start where appropriate;
checking pressure indicators;
testing electrical conditions by qualified personnel when required;
confirming that mechanical movement has stopped;
confirming that valves and other isolation points are secure.

The verification method must match the hazards and the equipment-specific procedure.

After a start attempt used as part of verification, controls should be returned to the appropriate off or neutral position before work begins.

Why Verification Matters

A lock installed on the wrong disconnect does not protect the worker. A closed valve that leaks badly may not provide the required isolation. A second electrical supply may remain energized. A remote automatic control may operate another component.

Verification is therefore an independent confirmation that the energy-control steps actually produced the safe condition intended by the procedure.

Multiple Energy Sources

Complex equipment may have several energy sources.

Consider a wastewater pump with:

an electrical motor;
pressurized discharge piping;
an open suction path from a wet well;
an automatically operated valve;
rotating components that may continue moving after shutdown.

Turning off only the motor does not necessarily address all hazards.

The authorized employee must identify and control every source capable of causing injury during the work.

Automatic and Remote Equipment

Water and wastewater plants frequently use SCADA systems, programmable controllers, level controls, timers, remote switches, and automatic pump sequencing.

Changing equipment from automatic to manual mode or selecting OFF on a control screen is not necessarily energy isolation.

Control logic can fail, another operator can send a command, or stored energy can remain available. Physical energy isolation must be performed when required by the hazardous-energy-control procedure.

Group Lockout/Tagout

Maintenance projects may involve several authorized employees, contractors, or work groups.

Group LOTO procedures must provide each authorized employee with protection equivalent to individual lockout or tagout.

OSHA group procedures assign overall responsibility for coordinating the work and require each authorized employee to apply a personal lockout or tagout device to the group lockout device, lockbox, or comparable mechanism when beginning work and remove it when that employee stops working.

Group lockout requires clear coordination because several crews may depend on the same isolation.

Shift and Personnel Changes

LOTO protection must continue without interruption when work extends across a shift change or when personnel change.

The facility procedure should provide an orderly transfer of protection from outgoing employees to incoming employees.

A worker should never assume that another employee's lock automatically provides personal protection unless the established group or transfer procedure specifically provides that protection.

Removing Another Employee's Lock

As a general rule, the employee who applied a personal lockout or tagout device removes it.

If that employee is unavailable, OSHA permits employer-directed removal only under a specific documented procedure that provides equivalent safety.

The procedure includes confirming that the employee is not at the facility, making reasonable efforts to contact the employee, and ensuring the employee knows the device was removed before returning to work.

An operator should never casually cut or remove another employee's lock because the equipment is needed back in service.

Testing or Positioning Equipment During Maintenance

Sometimes equipment must temporarily be energized for testing or positioning during servicing.

This does not mean the normal LOTO process can simply be ignored.

OSHA requires an orderly sequence that includes clearing tools and materials, removing employees from danger, removing LOTO devices according to the procedure, energizing only for the necessary test or positioning, deenergizing again, and reapplying energy controls before servicing continues.

Valves and Pressurized Systems

Water and wastewater operators frequently work around valves and piping where stored hydraulic or pneumatic pressure can remain after pumps are stopped.

Potential hazards include:

pressurized water;
wastewater;
compressed air;
chemical solution;
sludge;
gas.

Isolation should consider whether valves provide the level of protection required for the task and whether trapped pressure must be safely relieved.

Never loosen a flange, fitting, valve component, or instrument connection simply because the pump is off. Confirm the energy-control condition first.

Gravity and Mechanical Energy

Equipment does not need electricity to move dangerously.

Examples include:

a raised gate that can drop;
a suspended pump or component;
a spring-loaded actuator;
a rotating component that continues to coast;
a heavy cover or mechanism capable of moving under gravity.

Blocking, restraint, mechanical support, or another approved control may be needed in addition to conventional electrical lockout.

Restoring Equipment to Service

Before energy is restored, the work area should be inspected.

Operators should verify that:

maintenance work is complete;
tools and unnecessary materials have been removed;
guards and components are properly installed;
employees are safely positioned;
the equipment is operationally ready;
locks and tags are removed according to the procedure.

Affected employees should then be notified as required before or after restoration according to the energy-control procedure and applicable requirements.

Do Not Bypass Someone Else's Protection

A lock or tag communicates that hazardous-energy control is in effect.

Employees should never:

attempt to restart locked-out equipment;
operate an isolation device protected by another worker;
remove someone else's lock without following the approved exception procedure;
bypass an energy-control device;
assume the equipment is available because no maintenance worker is visible.

Periodic Inspection and Training

An effective energy-control program includes more than locks and written procedures.

OSHA requires periodic inspection of energy-control procedures at least annually to confirm that the procedure and standard requirements are being followed and to correct deficiencies.

Authorized employees must receive training appropriate to the hazardous energy they control. Affected employees must understand the purpose and use of the energy-control procedure, and other employees working in areas where LOTO is used must understand that locked or tagged equipment must not be restarted or disturbed.

Common Lockout/Tagout Mistakes

Using a stop button instead of an energy-isolating device.
Locking out only the electrical source while ignoring pressure, gravity, or another hazardous energy source.
Beginning work immediately after applying a lock without verifying isolation.
Failing to release trapped pressure or other stored energy.
Assuming an automatic-control OFF command provides physical isolation.
Using another employee's personal lock as the only protection for your own work outside an approved group procedure.
Removing another employee's lock without following the established exception procedure.
Failing to maintain LOTO protection during a shift change.
Reenergizing equipment while workers, tools, or removed guards remain in danger.
Failing to notify affected employees.
Relying on memory instead of the applicable equipment-specific procedure.

A Practical LOTO Mindset

Identify every hazardous energy source.
Understand the type and magnitude of each source.
Notify affected personnel.
Shut equipment down normally.
Physically isolate the required energy sources.
Apply the required lockout or tagout devices.
Release, block, restrain, or otherwise control stored energy.
Verify effective isolation and deenergization.
Perform the work without defeating the energy controls.
Maintain protection through group work and shift changes.
Inspect the equipment and work area before restoration.
Remove personal devices according to the approved procedure.
Notify affected employees and restore service safely.

What to Remember for the Exam

LOTO protects employees from unexpected energization, startup, movement, or release of stored energy.
Hazardous energy can be electrical, mechanical, hydraulic, pneumatic, chemical, thermal, gravitational, or stored energy.
A stop button or control switch is not automatically an energy-isolating device.
Authorized employees perform energy-control functions and require appropriate hazardous-energy training.
Affected employees operate the equipment or work in the affected area and must understand the purpose of the procedure.
Identify every hazardous energy source before servicing begins.
Apply locks or tags to the appropriate energy-isolating devices.
Relieve, restrain, disconnect, or otherwise control hazardous stored energy.
Verify isolation and deenergization before beginning servicing or maintenance.
If stored energy can reaccumulate, continue verifying its control as necessary.
Automatic controls and SCADA commands do not replace physical energy isolation when LOTO is required.
Group LOTO must provide protection to each authorized employee.
LOTO protection must remain continuous during shift or personnel changes.
Normally, the employee who applies a personal lock removes it.
Temporary energization for testing must follow a controlled sequence.
Before restoring energy, inspect the work area and make sure employees are safely positioned.
Never restart, bypass, or disturb equipment protected by another employee's lockout or tagout device.