Reviewed and Approved By:
Catherine L. Fiore, PFC Safety Officer
Standard Operating Procedures at the PFC
Title: MINIMUM PERSONNEL AND ADMINISTRATIVE REQUIREMENTS FOR WORK ON ELECTRICAL EQUIPMENT
Author: Dan Yates, Catherine Fiore, Updates by C. Fiore
Date: August 8, 1991, Modified August 17, 2006
Persons Responsible: All PFC Supervisors and Personnel Who work On
This document presents the Plasma Fusion Center safety policy for work on electrical equipment and describes minimum personnel and administrative requirements.
The safety policy and requirements apply to all electrical aspects of Plasma Fusion Center projects.
The ability of the human body to withstand the internal passage of electrical current is so small that most electrical systems can be hazardous to health and life. Special hazards exist in research and development activities involving the use of unique electrical and electronic systems, specialized equipment, and unusual use of conventional equipment.
The Plasma Fusion Center Office of Environment, Safety, and Health (ES&H) is responsible for establishing electrical safety requirements. Catherine Fiore is the head of this office.
Technical supervisors are responsible for implementing and enforcing this requirement. Work assignments should be planned to include the minimum personnel complement required by this document.
Electrical Safety Criteria for Research and Development Activities,
Department of Energy, August, 1979 Alcator Project Lockout/Tagout
Procedures, NFPA 70-E
Minimizing the risk of accidents is the fundamental criterion to be
when working on electrical equipment. Work should be conducted with the
equipment in its positively de-energized state to the maximum extent
practicable. Work on energized equipment, with interlocks defeated or
protective barriers removed, will be permitted only as a last resort
reasonable attempts have been made to work with the equipment
Work on energized breaker boxes is prohibited except when a power
outage will disable a required safety system, such as the diborane
ventillation or monitoring or the fire alarm systems.
Routine work should be planned carefully and scheduled well in advance. Work assignments should be planned to include the minimum personnel complement required by this document.
When emergency work is required, electrical safety shall not be compromised in favor of maintaining the project schedule. Equipment outages shall be scheduled in lieu of working on energized equipment.
SAFETY CRITERIA FOR WORK ON ELECTRICAL EQUIPMENT
1. Perform all work, when feasible, with the equipment in a positively de-energized state. Employ lockout/tagout procedures.
2. Assign an adequate number of knowledgeable persons for work on hazardous equipment.
3. Assign a safety watch whenever the complexities of the work or the associated hazards dictate.
4. When complex or extremely hazardous equipment is involved, use written procedures to insure that the equipment is positively de-energized.
ELECTRICAL HAZARD CLASSES
The Department of Energy has divided electrical hazards into two classes, Class A and Class B. Class A presents the lower risk. The electrical hazards in Class A are such that they can usually be safely controlled with a minimum of personnel and administrative requirements. Class B electrical hazards are those where any of the Class A limits are exceeded.
Class A Hazard:
A "Class A" electrical hazard exists when all of the following four conditions are satisfied:
1. The equipment source voltage does not exceed 130 VAC rms.
2. The available AC load current is limited to 30 A by circuit breakers or fuses.
3. Stored energy in capacitor or inductor does not exceed 10 joules.
4. Internal AC or DC voltages either do not exceed 30 V or have power limits of 150 VA.
While Class A voltages, currents, and energies may be considered small, a Class A electrical hazard must be regarded as potentially lethal. This class can be particularly dangerous because of its everyday familiarity.
Class B Hazard:
A "Class B" electrical hazard exists when one or more of the following four conditions is present:
1. The equipment source voltage exceeds 130 VAC rms.
2. The available AC load current exceeds 30 A.
3. Stored energy in capacitor or inductor exceeds 10 joules.
4. Internal AC or DC voltages exceed 30 V and have power limits greater than 150 VA.
The Department of Energy has established three "working modes" for procedures involving electrical equipment. These modes are used in conjunction with the hazard classes to specify the minimum personnel and administrative requirements.
Mode 1 (Minimum Hazard):
All operations are performed with the equipment in a positively de-energized state. All external sources of electrical energy are disconnected by some positive action (e.g., locked and tagged switch; or plug removed and guarded), and all internal sources are made safe (discharged and grounded).
Mode 2 (Moderate Hazard):
Hands-on operations are performed with the equipment positively de-energized. Equipment functions are then remotely observed with the equipment energized and protective barriers removed.
Mode 3 (Severe Hazard):
Hands-on operations are performed with the equipment energized and protective barriers removed.
Minimum Personnel and Administrative Requirements Table 1 (below) can be used to determine personnel and administrative requirements for each electrical work assignment. Requirements are based on the electrical hazard class and working mode appropriate to a specific task.
(Each of the following conditions must be satisfied.)
(Any of the following contitions are present.)
|MODE 1: MINIMUM HAZARD
All operations performed with equpment positively deenergized
Once equipment is positively deenergized, personnel may work alone with minimum supervision.
The equipment must be positively deenergized following PSFC Lockout/Tagout procedures.
Then, personnel may work alone with general supervision.
|MODE 2: MODERATE HAZARD
Hands-on operations performed with equpment positively deenergized
Equipment functions remotely observed with equipment energized and protective barriers removed.
Personnel may work alone on assigned tasks with general supervision
Two knowledgeable persons and verbal approval from supervisor required.
Follow Lockout/Tagout procedures for hands-on operation.
|MODE 3: SEVERE HAZARD
Hands-on operations performed with equpment energized and protective barriers removed.
Personnel may work alone with general supervision, but a companion is required.
Two knowledgeable persons plus a safety watch required.
Written approval from supervisor and Safety Officer or designee required.
*Mode 3, Class B conditions require written approval from the supervisor and the safety officer or his/her designee. The safety officer may require a written procedure documenting safety precautions to be used.
Routine work done by a licensed electrician and helper on AC input voltages of less than 600 V does not require a safety watch and written permission.
Positively De-energized - all external sources of electrical energy are disconnected by some positive action (e.g., locked and tagged switch; or plug removed and guarded) and all internal energy sources (e.g., capacitor energy storage) are made safe by discharging and grounding.
Companion - co-worker who is cognizant of the danger and occasionally checks on the other worker.
General Supervision - supervisory personnel, either the person's direct supervisor or the supervisor for the laboratory space where the work is being done should be aware that class A mode 3 electrical work is taking place, and should accept responsibility for the safety of the person performing the work. The general supervisor should assure that the person is qualified for the work and understands any procedures which should be followed.
Knowledgeable Person - one who is recognized by his/her supervisor and by the PFC Safety Officer or Asst. Safety Officer as having sufficient understanding of an experimental device or facility to be able to positively identify and control the hazards it may present.
Safety Watch - a person whose specific duties are to observe the worker(s) and operations being performed, prevent careless acts, quickly de-energize the equipment in emergencies and alert emergency rescue personnel. This person shall have basic CPR training and be thoroughly instructed on the locations of emergency shut-off switches and power disconnects and on the specific working procedures to be followed.