Facility Safety Management

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Locking Out
Prevent Release of Hazardous Energy

Hazardous energy is any type of energy that in sufficient quantity can cause injury to a worker. Common sources of hazardous energy include electricity, mechanical motion, pressurized air, and hot
and cold temperatures.

Investigations conducted as part of the NIOSH Fatality Assessment and Control Evaluation (FACE) Program suggest that developing and following hazardous energy control procedures could prevent worker injuries and fatalities.

Workers may be exposed to hazardous energy in several forms and combinations during installation, maintenance, service or repair work. The National Institute for Occupational Safety and Health says, a comprehensive hazardous energy control program should address all forms of hazardous energy, which include the following:

• Kinetic (mechanical) energy in the moving parts of mechanical systems;
• Potential energy stored in pressure vessels, gas tanks, hydraulic or pneumatic systems, and springs (potential energy can be released as hazardous kinetic energy);
• Electrical energy from generated electrical power, static sources, or electrical storage devices (such as batteries or capacitors); and
• Thermal energy (high or low temperature) resulting from mechanical work, radiation, chemical reaction or electrical resistance.

To keep workers from contacting uncontrolled hazardous energy during installation, maintenance, service or repair work, NIOSH recommends that every employer, manager, supervisor, and worker who installs, maintains, services, or repairs machines, equipment, processes, or systems be familiar with the following concept:

Only the worker who installs a lock and tag should remove them after work is complete and inspected.
Though there is no detailed national data available on the number of workers killed each year by contact with uncontrolled hazardous energy, from 1982 to 1997, NIOSH investigated 1,281 fatal incidents as part of their FACE Program. Of these, 152 involved installation, maintenance, service,
or repair tasks on or near machines, equipment, processes, or systems. Because the FACE program was active in only 20 states during this time, these fatalities represent only a portion of the U.S. workers who were killed by contact with uncontrolled hazardous energy.

Contributing Factors
Review of these 152 incidents suggests that three related factors contributed to these fatalities:
• Failure to completely de-energize, isolate, block, and/or dissipate the energy source (82 percent of the incidents, or 124 of 152);
• Failure to lockout and tagout energy control devices and isolation points after deenergization (11percent of the incidents, or 17 of 152);
• Failure to verify that the energy source was de-energized before beginning work (7 percent of the incidents, or 11 of 152).

In a study conducted by the United Auto Workers (UAW), 20 percent of the fatalities (83of 414) that occurred among their members between 1973 and 1995 were attributed to inadequate hazardous energy control procedures specifically, lockout/tagout procedures. The energy sources involved in these fatalities included kinetic, potential, electrical, and thermal energy [UAW 1997].

Current Occupational Safety and Health Administration (OSHA) standards for general industry are established to prevent injuries and fatalities from contact with hazardous energy [29 CFR* 1910.147].

This standard requires employers to “establish a program consisting of energy control procedures,
employee training and periodic inspections to ensure that before any employee performs any servicing or maintenance on a machine or equipment where the unexpected energizing, start up or release of stored energy could occur and cause injury, the machine or equipment shall be isolated from the energy source, and rendered inoperative.”

Take the following steps to protect your workers who install or service equipment and systems:

• Follow OSHA regulations.

• Identify and label all sources of hazardous energy.

• Before beginning work, do the following:

• De-energize all sources of hazardous energy;

• Disconnect or shut down engines or motors;

• De-energize electrical circuits;

• Block fluid (gas or liquid) flow in hydraulic or pneumatic systems;

• Block machine parts against motion;

• Block or dissipate stored energy;

• Discharge capacitors; and

• Release or block springs that are under compression or tension.

Vent fluids from pressure vessels, tanks, or accumulators, but never vent toxic, flammable, or explosive substances directly into the atmosphere.

Implement a Hazardous Energy Control Program
Employers should develop and implement a written hazardous energy control program that, at a minimum:
• describes safe work procedures;
• establishes formal lockout/tagout procedures;
• trains all employees in the program; and
• enforces the use of the procedures (including disciplinary action for failure to follow them).
Hazardous energy control programs should outline the following safe work practices:
• Identify tasks that may expose workers to hazardous energy.
• Identify and de-energize all hazardous energy sources, including those in adjacent equipment.
• Lockout and tagout all energy-isolating devices to prevent inadvertent or unauthorized reactivation or startup.
• Isolate, block, and/or dissipate all hazardous sources of stored or residual energy, including those in adjacent equipment.
• Before beginning to work, verify energy isolation and de-energization, including that in adjacent equipment or energy sources.
• After work is complete, verify that all personnel are clear of danger points before reenergizing
the system.

Hazardous energy control among work groups must be coordinated when multiple employers are involved in large projects and when shift changes occur during such activities. Outside contractors should work with the facility owner to make sure that an adequate hazardous energy control
program is implemented specifically for contract workers.

Identify and Label All Hazardous Energy Sources
Employers should use jobsite surveys to ensure that all hazardous energy sources (including
those in adjacent equipment) are identified before beginning any installation, maintenance, service, or repair tasks. Energy-isolating devices such as breaker panels and control valves should be clearly labeled [NIOSH 1983].

De-energize, isolate, block, and/or dissipate all forms of hazardous energy. All forms of hazardous energy should be de-energized, isolated, blocked, and/or dislated, sipated before workers begin any installation, maintenance, service, or repair work.

The method of energy control depends on the form of energy involved and the available means to control it. Energy is considered to be isolated or blocked when its flow or use cannot occur [NIOSH 1983].

To isolate or block energy, take the following steps:
• Disconnect or shut down engines or motors that power mechanical systems.
• De-energize electrical circuits by disconnecting the power source from the circuit.
• Block fluid (gas, liquid, or vapor) flow in hydraulic, pneumatic, or steam systems by using control valves or by capping or blanking§ the lines.
• Block machine parts against motion that might result from gravity (falling). Some forms of energy must also be dissipated after a system has been de-energized.

System components such as electrical capacitors, hydraulic accumulators, or air reservoirs may retain sufficient energy to cause serious injury or death even though the component has been de-energized, isodislated, or blocked from the system and locked out.

Energy can be dissipated by taking the following steps:
• Vent fluids from pressure vessels, tanks, or accumulators until internal pressure is at atmospheric levels. However, do not vent vessels or tanks containing toxic, flammable, or explosive substances directly to the atmosphere.

• Discharge capacitors by grounding.
• Release or block springs that are under tension or compression.
• Dissipate inertial forces by allowing the system to come to a complete stop after the machine or equipment has been shut down and isolated from its energy sources.

Establish lockout/tagout programs requiring individually assigned locks and keys to secure energy control devices. Lockout/tagout programs should be based on the principle of only one key for
each lock the worker controls.This means the following:
—Workers are assigned individual locks operable by only one key for use in securing energy
control devices (breaker panels, control valves, manual override switches, etc.).
—Each worker maintains custody of the key for each of his or her assigned locks.
—Each lock is labeled with a durable tag or other means that identifies its owner.
—When work is performed by more than one worker, each worker applies his or her own lock to the energy-securing device.
Scissors- type hasps made of hardened steel are available to facilitate the use of more than one lock to secure an energy control device.
—All de-energized circuits and systems are clearly labeled with durable tags.
—The worker who installs a lock is the one who removes it after all work has been completed [NIOSH 1988].
—If work is not complete when the shift changes, workers arriving on shift apply their locks before departing workers remove their locks.

Because tags can be easily removed, they are not a substitute for locks. Workers are safest with a program that uses both locks and warning tags to prevent systems from being inadvertently re-energized.

Use of master keys should be reserved for unusual circumstances when the worker is absent from the workplace. However, if master keys are necessary, keep them under supervisory control. List the proper procedures for using them in the written program for controlling hazardous energy.

Verify Energy Sources
are De-energized
Employers should establish and enforce company policies requiring workers to verify that all energy sources are de-energized before work begins. This verification should ensure that all energy sources (including stored energy) are controlled (that is, de-energized, isolated, blocked, and/or dissipated) before work begins. Appropriate testing equipment should be required as needed.

To ensure that equipment will operate as expected when it is re-energized, employers should require qualified persons to inspect completed installation, maintenance, service, or repair work. The inspection should verify that installation, repairs, and modifications were performed correctly and
that the correct replacement parts were used.

When equivalent or updated parts must be substituted for original parts, the system may need to be modified. Re-energized equipment should be closely monitored for several operating cycles to ensure that it is functioning correctly and safely.

Make sure that all persons are clear of danger points before re-energizing the system. Employers should develop procedures to verify that all persons are clear of danger points before re-energizing the system.

Locks and tags should be removed only by the workers who installed them—and only after workers have been cleared from the danger points.

This may require visual inspections and searches of areas around machinery or electrical circuits to assure that workers will not be exposed to the release of hazardous energy when equipment is re-energized.

Workers should be informed about impending equipment start-up with warning devices they can see and hear. Such devices will help assure that workers are clear before equipment is re-energized. FSM