PSFC Office of Environment, Safety and Health

Plasma Science and Fusion Center

Office of Environment, Safety, and Health

190 Albany Street, NW21 2nd floor
Fax 617-252-1808

Be Safe or Die

Reviewed and Approved By:

PSFC Supervisor--James H.Irby

PSFC Supervisor--William G. Byford

PSFC Safety Officer--Catherine L. Fiore

Plasma Science and Fusion Center

Lockout and Tagout Procedures


This document establishes procedures for lockout and tagout of energy sources that could cause injury to personnel or damage to equipment.


All types of energy sources, including electrical, mechanical, hydraulic, pneumatic,chemical, or thermal, are subject to these procedures. Electrical energy sources of less than 24 Volts AC or DC and less than 10 Amps maximum rated current do not require lockout. Equipment that can be disconnected from energy sources by standard plugs, fittings, or other connections do not require lockout if the disconnected plug is visible to workers at all times, or if the plug is removed and tagged out as specified below.

All employees, students, visitors, and contractors at the PFC must comply with these procedures. Any employee or student that is involved in the use, installation, repair, removal, or maintenance of potentially hazardous equipment must read and understand this document before beginning work. Any person issued a safety lock must be issued a copy of this document and satisfy either Bill Byford (Asst. Safety Officer) or Jim Irby (Alcator Operations Leader) that they fully understand these procedures. All visitors and contractors working with equipment connected to energy sources must either read and understand this document or rely on a designated supervisor to comply with these procedures.

Violations of These Procedures

Any person who violates these procedures is placing themselves and their coworkers in danger of injury or death. It is the responsibility of supervisors to ensure that all persons under their supervision are properly instructed in these procedures. It is the responsibility of all employees to understand and abide by these rules, and to report violations. Any person who knowingly violates these procedures shall be subject to immediate disciplinary action. At the least this action shall include a verbal and written reprimand, a copy of which shall be filed in the person's personnel file. Repeated violations of these procedures constitute grounds for dismissal.

Changes to These Procedures

No person may amend, alter, or otherwise change these procedures, in whole or in part, without the written approval of the PFC Safety Committee. Verbal changes are explicitly forbidden at all times. Temporary changes or dispensations are not allowed for any reason. Changes in these procedures require that all employees be instructed in the new procedures with particular emphasis placed on the difference between old and new procedures.


Energy Source - Any device or process that can provide energy of any form, including electrical, mechanical, chemical, hydraulic, pneumatic, and thermal energy. Examples of energy sources include utility electrical, water, or gas services, compressed gases, springs, rotating masses, steam, capacitors, hydraulic and pneumatic reservoirs (including reservoirs such as air trapped in a pipeline), furnaces, steam lines, and cryogenic fluids.

High Energy Electrical Source - Any device or process that can provide electrical energy at a voltage in excess of 600 Volts.

Energy Isolating Device - A physical (as opposed to procedural or programmable) device that prevents the transmission or release of energy. An energy isolating device must include provisions for locking the device in the state that prevents the transmission or release of energy, and prominent visual indication of the state of the device. A fused disconnect switch, a chained line valve, a locking slide gate, and similar devices are valid energy isolating devices. Molded case circuit breakers without locking provisions, micro switches, computer operated controls of any kind, interlocks, push buttons, and selector switches are not valid energy isolating devices.

Safety Lock - A sturdy mechanical lock issued with a single, numbered key to a specific individual for the sole purpose of locking energy isolating devices in the open (safe) position. Combination locks are not acceptable safety locks.

Lockout Procedure

Purpose - The purpose of the lockout procedure is to ensure an individual's personal safety while working on equipment connected to energy sources of any kind.

Placement of locks - Before placement of the lock, the person placing the lock must be certain as to which switch(s), valve(s), or other energy isolating device(s) are to be locked. Special attention to be given to the possibility of multiple energy sources connected to one piece of equipment. Multiple sources might include multiple services (e.g. electric at two voltages, or electric and hydraulic), or redundant services (e.g. primary and backup electrical service via a transfer switch). After verification of the number and placement of locks, the following steps must be followed in sequence:

  1. Notify all affected persons that a lockout is required. Verbal notification is satisfactory but written notification is preferable, especially if the lockout is expected to be in effect for a prolonged period. Notification should include the reason for the lockout, the name(s) of the person(s) performing the work, and the expected duration.
  2. If the equipment is operating, shut it down in the normal fashion.
  3. Operate the energy isolating device(s), so that all energy sources are disconnected from the equipment. Stored energy, such as that in capacitors, springs, elevated machine members, hydraulic systems, etc., must be dissipated or restrained by discharge, blocking, bleeding down, or other appropriate measures.
  4. Place the safety lock(s) on the energy isolating device(s), lock the lock(s), and pocket the key(s).
  5. Fill out and affix a tag to each lock placed in step 4. See Tagout Procedure.
  6. After double-checking that no personnel are exposed, attempt to operate the equipment with the normal control functions. Verify that the equipment does not operate and that all energy sources are isolated. Important: Return each operating control to the "OFF" position after test.
  7. Inspect and test the equipment with appropriate instruments to verify that all energy sources are disconnected. Verify proper functioning of instruments before and after test. For multiple energy sources and/or multi-phase sources, check each source and each phase. After successful completion of this inspection, the equipment is locked out.

Removal of locks

After service or testing of the locked-out equipment is complete, the following steps must be followed in sequence in order to remove the lock(s):

  1. Notify all affected persons that the lockout is ended. Verbal notification is satisfactory, but written notification is required if the original notification of lockout was written.
  2. Inspect the equipment and all connected parts between the equipment and the energy isolating device(s). Make sure all covers, guards, and other devices are in place, and that the equipment is safe to energize. Double check that any grounds, blocks, or other such devices are removed. Check that no tools have been left in, on, or near the equipment.
  3. Remove each lock and tag placed for the lockout. See Tagout Procedure. If appropriate, close the energy isolating device.

Lockout by more than one person

Each person working on equipment shall place their own lock(s) and tag(s). If necessary, lockout tongs may be used to allow multiple locks to be placed on the same energy isolating device. If a large group is to work on equipment that must be locked out, the supervisor or designated alternate may lock out equipment for the entire crew. In such cases, it is the responsibility of the person placing the lock to inform all members of the crew that the equipment is locked out. It is that person's further responsibility to inform and account for each member of the crew before removing the lock.

Lockout of High Energy Electrical Sources

High energy electrical sources (those with a voltage greater than 600 volts) require special caution and attention to detail. Whenever equipment connected to high energy electrical sources is to be worked on, the following steps must be taken in addition to those required for a normal lockout.

  1. At least 2 persons must work together at all times whenever high energy electrical sources are to be locked out.
  2. The high energy source must be isolated from the equipment by at least 2 energy isolating devices. These devices must be electrically in series. Both devices must be locked open and tagged out before work can commence. Each of the minimum 2 person team may elect to place one lock or two.
  3. Voltmeters are not to be used to determine that the high energy source has been disconnected. "Tic Tracers" with both audible and visual indications are the preferred instrument.
  4. After both locks are placed (following the lockout procedure outlined above) the LINE side of the second energy isolating device must be grounded. The grounds must be in place for the entire duration of the work.
  5. Extra care shall be used in ensuring that all stored energy, particularly energy stored in stray capacitance (in cables, lightning arrestors, power factor correction capacitors, etc.) is safely discharged in all parts of the circuit to be locked out. Grounds should be in place on all conductors in the work area whenever work is in progress. If grounds are removed for any reason, they should be replaced before continuing work.
  6. When removing locks from a high energy source, at least 2 people must independently perform complete inspections of the work area, the equipment worked on, and the entire circuit from the first lock to the equipment. All grounds must be removed, all tools and parts stored, all areas clean, and all covers and other safety devices installed and secured.

Equipment without energy isolating device - All equipment installed in the PFC should be connected via appropriate energy isolating devices. If any equipment is discovered that does not meet the requirements of these procedures, it should be brought to the attention of Bill Byford or Jim Irby immediately.

Tagout Procedure

Purpose - The purpose of the tagout procedure is twofold. Tagout provides a prominent visual indication of a lockout or of any potential problem or hazard associated with equipment. Tagout of locked energy isolating devices is required as part of the lockout procedure. Tagout also provides a written, permanent record of lockouts and other circumstances where lockout is not required. Any piece of equipment, including controls, energy isolating devices, or components, may be tagged out.

Examples of tag use - Tagout is required whenever the lockout procedure is used. Tags may be affixed to equipment when there is no immediate danger to personal safety. Examples of appropriate tag use that does not require lockout include:

  1. An operator of a machine tool discovers that the tool has an electrical malfunction that could damage work in progress or the tool itself. The operator affixes a tag to the tool and/or to its energy isolating devices and notifies appropriate parties to arrange for repairs.
  2. A high voltage power supply is not to be used for an extended period of time. To ensure that the supply will not accidentally be turned on, an operator opens a molded-case circuit breaker that feeds the supply and tags it out.
  3. A piece of equipment is disconnected from water service and removed. The water lines are left in place. The valves to the water lines are tagged out to prevent floods.

Issue of Tags - Bill Byford or Jim Irby are the only persons authorized to issue tags. Each tag issued will have a unique serial number on it in 2 places. A log will be maintained, organized by tag serial number, showing to whom each tag was issued. Bill Byford or Jim Irby may elect to issue many tags to individuals who use them often.

Placement of tags - The Plasma Fusion Center Station Red Hold Tag with serial numbers is the only approved tag for the tagout procedure. To place a tag, all of the following information must be filled out legibly in ink on the tag;

The apparatus protected, listing the name and/or location of the apparatus being tagged out. The signature of the person placing the tag, together with the current time and date. The cause for tagout. The designation of the switch or control being tagged.

The bottom portion of the tag should be removed immediately after filling out the required information and affixing the tag. If the tag is to be left for an extended period of time (such as in example 3 above) the bottom portion of the tag should be turned over immediately to the person who issued the tag. If the tag will be removed soon, the person placing the tag may keep the bottom portion as a reminder of the location of each tag placed.

Removal of tags - Tags should normally be removed only by the person who placed them. Under no circumstances should a tag be removed without a reasonable attempt to contact the person placing the tag. The person who placed the tag may remove it whenever they are satisfied that the condition causing the tagout has been righted. Removal includes signing the tag, dating it, and turning both upper and lower parts of the tag over to Bill Byford or Jim Irby.

Bill Byford will maintain a record of all tags issued, placed, and removed. Tags that are placed for extended periods will have the reason for placement documented on the lower portion of the tag that was delivered to Bill Byford or Jim Irby by the person who placed the tag. Tags that are placed for short periods and removed by the person who placed them will have both potions of the tag turned in upon removal of the tag.

If the person who placed the tag is not available or cannot determine that the tag should be removed, the person responsible for the tagged equipment must seek the approval of Bill Byford or Jim Irby to remove the tag. Removing another's tag is a very serious responsibility. The person removing the tag assumes full and complete responsibility for the safety of the equipment and those who work with it. Tags should never be removed in haste or confusion. Before removing another's tag, the steps listed in Removal of Locks by Supervisor should be completed. Bill Byford and Jim Irby will require proof that the equipment is safe to operate, that the conditions leading to tagout have been rectified, and that the person who placed the tag is not available. The person removing the tag must sign and date it and give the removed tag to Bill Byford or Jim Irby.

Issue of Safety Locks

Only Bill Byford or Jim Irby are allowed to issue safety locks. They will verify that each person receiving a lock understands these procedures, and will supply each person issued a lock with a copy of the procedures.

A list of all person(s) issued safety locks, with date issued and key number, shall be maintained by Bill Byford.

A duplicate key for each safety lock issued shall be kept by Bill Byford or Jim Irby. The duplicate keys shall be kept secured under lock and key at all times. The duplicate key shall be used only if the original key is lost or damaged, or if the supervisor of the employee who placed the lock and tag elects to remove the lock and tag. (See below.) If the duplicate key is required because of loss or damage to the original key, the lock and key must be destroyed after the lock is removed

Removal of Locks by Supervisor

There are some instances where a lock may have to be removed by someone other than the person who instituted the lockout. Contractors may complete their work and leave the premises without removing locks that they were issued. An employee may be absent due to illness or other reasons. Under such circumstances, the supervisor may elect to remove the lock. Removing someone else's lock is a very serious responsibility. Supervisors removing other's locks assume full and complete responsibility for the safety of the equipment and those who work with it. Locks should never be removed in haste or confusion. Before removing another's lock, the supervisor must perform all of the following steps, in the order listed.

  1. Exhaust all reasonable means of contacting the person who placed the lock. This includes a through search of the premises, the person's normal workplace (if different), and telephone calls to both home and office numbers.
  2. Determine and understand the reason for the lockout.
  3. Determine and understand the need for removal of the lock by someone other than the person placing it.
  4. Thoroughly examine all parts of the locked out system and assess it's readiness for use. This requires at the least a visual inspection of all wiring, conduit, piping, etc., between the energy isolating device and the equipment, as well as a complete inspection and understanding of the equipment. If the supervisor is not completely familiar with the equipment, they must enlist the aid of those who are. Supervisors contemplating this procedure are cautioned that the parties asking to have the lock removed may not be the best consultants on this issue.
  5. If the supervisor is satisfied that the person who placed the lock cannot be contacted or cannot be present, and that there is an immediate need to operate the equipment, and that the equipment and all connected apparatus is safe for operation, the duplicate key should be obtained from Bill Byford or Jim Irby and the lock removed. They may require evidence of the need for the key. They may refuse to release the duplicate key if he is not fully satisfied that the above procedure has been strictly adhered to.
  6. It is essential that the person who originally placed the lock be notified as soon as possible that the lock has been removed.

This is an html version of the PSFC Lockout/Tagout Procedures, last released in May, 1995. The original version was authored by Steve Fairfax.

This page maintained by Catherine L. Fiore FIORE@PSFC.MIT.EDU