ELECTRICAL SAFE WORK PRACTICES
Electrical safety in the workplace is not just a catchy slogan or a good public relations sound bite. It is a systematic approach to working safely around energized equipment. An electrical safety program includes training of technicians and their supervisors to ensure that the electrical worker responsible for servicing, maintaining, installing, repairing, and adjusting electrical equipment is qualified to perform those functions. It also includes developing self-discipline and a safety mind-set while working around or near energized electrical equipment. Without it, all the training in the world will not keep you safe for very long.
The Occupational Safety and Health Administration (OSHA) defines a qualified individual as one who possesses the following:
1. Technicians who are trained in and familiar with the safety-related work practices, safety procedures, and other safety requirements that pertain to their respective job assignments.
2. They will be trained in and familiar with any other safety practices, including applicable emergency procedures that are related to their work and necessary for their safety.
3. They will have the skills necessary to distinguish exposed energized electrical conductors and circuit parts from other parts of electric equipment.
4. They will have the skills necessary to determine the nominal voltage of exposed energized electrical conductors and circuit parts.
5. They will know the minimum approach distances corresponding to the voltages to which they will be exposed.
6. They will know the proper use of the special precautionary techniques, Personal Protective Equipment (PPE), insulating and shielding materials, and insulated tools for working on or near exposed energized parts of electrical equipment.
Note: A qualified electrical worker may be qualified to work on one piece of equipment, but not qualified to work on another piece of equipment. The title of electrician does not automatically qualify an individual to work on everything electrical.
There are many documents that describe the safety requirements in a facility. Corporate policy, safety manuals, and procedures are all written to establish a safe work environment. These documents are based on most of the following information. Some is a matter of law, and others are used as consensus documents that, although not mandated, are recommended.
The Code of Federal Regulations (Figure 1) is the law by which employers and workers must provide a coordinated and safe work environment. Of particular interest for the subject of electrical safety are:
Figure 1: 29CFR 1910 OSHA for General Industry
Violation of the regulations in the OSHA standard can result in severe fines and/or imprisonment, as occurred in the following example:
Where the 29CFR 1910 OSHA for General Industry tells workers what it required, it does not tell workers how to get there; it leaves that to the employer. NFPA 70E (Figure 2) is considered the way to get to where OSHA wants us to be as far as electrical safety is concerned. By following the steps in 70E, the worker will comply with the requirements of OSHA. This document is updated every three years, and it should be reviewed to ensure the safety policy is still accurate.
Figure 2: NFPA 70E
The National Electric Code (Figure 3) is a legal requirement if it has been adopted by the authority having jurisdiction. This means that if a state, county, municipality, or local government adopts the code, it then becomes law. The latest revision is the 2011 version. The stated purpose of the code is "the practical safeguarding of persons and property from hazards arising from the use of electricity."
Figure 3: National Electric Code (NFPA 70)
The purpose of this book is to reduce hazards to life and property that can result from failure or malfunction of industrial-type electrical systems and equipment. The book gives recommended tests and maintenance schedules for various classes and types of electrical equipment and systems.
A qualified electrical worker will be trained and knowledgeable of the construction and operation of equipment or a specific work method and be trained to recognize and avoid the electrical hazards that might be present with respect to that equipment or work method.
a. Such qualified electrical workers will also be familiar with the proper use of the special precautionary techniques and PPE, including arc flash, insulating and shielding materials, and insulated tools and test equipment. A qualified electrical worker is considered qualified with respect to certain equipment and methods but still unqualified for others.
b. An electrical worker who is undergoing on-the-job training and who, in the course of such training, has demonstrated an ability to perform duties safely at his or her level of training and who is under the direct supervision of a qualified electrical worker will be considered to be a qualified electrical worker for the performance of those duties.
c. Such qualified electrical workers permitted to work within the flash hazard boundary of exposed energized electrical conductors and circuit parts operating at 50 volts or more will, at a minimum, be additionally trained in all of the following:
i. The skills and techniques necessary to distinguish exposed energized electrical conductors and circuit parts from other parts of electrical equipment.
ii. The skills and techniques necessary to determine the nominal voltage of exposed energized electrical conductors and circuit parts.
iii. The approach distances specified by the company-approved arc flash label and the corresponding voltages to which the qualified electrical worker will be exposed.
iv. The decision-making process necessary to determine the degree and extent of the hazard, the PPE, and job planning necessary to perform the task safely.
The following is provided as an example of what an electrical safety program contains.
A dangerous condition such that contact or equipment failure can result in electric shock, arc flash burn, thermal burn, or blast
Recognizing hazards associated with the use of electrical energy and taking precautions so that hazards do not cause injury or death
Identify a hazard/risk evaluation procedure to be used before work is started on or near energized electrical conductors, circuit parts operating at 50 volts or more, or where an electrical hazard exists.
According to the the NFPA70E, "working on (energized electrical conductors or circuit parts)" is the coming into contact with energized electrical conductors or circuit parts with the hands, feet, or other body parts or with tools, probes, or with test equipment, regardless of the personal protective equipment a person is wearing.
There are two categories of "working on". The first category is diagnostic testing, which is the taking of readings or measurements of electrical equipment that does not require making any physical change to the equipment. Repair is the second category, which is the physical alternation of electrical equipment, such as the making or tightening connections, removing or replacing components, etc.
The major difference between the two categories is that performing diagnostics does not require written permission, while the performance of a repair on equipment that is not in an electrically safe work condition will typically require a written job plan and permission from management before performing the task.
Visual inspections of operating equipment are allowed; however, setting an electrically safe work area and full compliance with PPE requirements must be accomplished before conducting the visual inspection.
Exposed electrical conductors or circuit parts that are, or can become, energized will be placed in an electrically safe state before a technician works on or near them. The act of placing the exposed electrical conductors or circuit parts in an electrically safe state is a hazardous process, and electrically safe practices consistent with the level of hazard will be used. This requires the employer to conduct an electrical hazard analysis. This consists of conducting a shock hazard analysis and a flash hazard analysis.
The shock protection boundaries identified as limited, restricted, and prohibited approach boundaries are applicable to the situation in which approaching electrical workers are exposed to energized electrical conductors and circuit parts. See Table 1 for the distances associated with various system voltages. Table 1 is not inclusive of all voltage ranges covered by the NFPA70E
When work is to be performed within the flash hazard boundary, the flash hazard analysis will determine, and the employer will document, the incident energy exposure of the worker, or calories per square centimeter. The flash hazard boundary is the distance from the arc flash event where the incident energy has dissipated to 1.2 cal/cm2, which is still enough heat energy to cause 2nd degree burns, or a burn with blisters on unprotected skin. The incident energy exposure level will be based on the working distance of the technicians face and chest areas from a prospective arc source for the specific task to be performed. Flame-resistant (FR) clothing and PPE (Figure 4) will be used by the technician based on the incident energy exposure associated with the specific equipment. This information will be obtained from the arc flash label.
Figure 4: Arc Flash PPE
This has been accomplished through the arc flash assessment. The arc flash label (Figure 5) is the instrument of communication of the boundary information determined by those two analyses. The process used to calculate the flash hazard boundary is beyond the scope of this course and will not be covered.
Figure 5: Arc Flash Label
There will be times when the calculated arc flash boundary exceeds the distance of the limited approach boundary set by Table 1. To maintain full protection of unqualified workers and qualified workers not involved in the task, it is recommended that a boundary to the work area be established at the limited approach boundary or the flash hazard boundary, whichever is larger; while electrical equipment is open, no one is allowed into the boundary unless the required PPE is used until an electrically safe work area has been established.
An electrically safe work condition (Figure 6) is a state in which the conductor or circuit part to be worked on, or near the part to be worked on, is disconnected from energized parts, locked/tagged in accordance with established standards, tested to ensure the absence of voltage, and grounded if determined necessary.
Figure 6: Examples of an Electrically Safe Work Condition
Figure 7: Various States of Electrical Equipment
An electrically safe work condition will be achieved when performed in accordance with the following procedure and verified by the following process.
Temporary grounds will be placed at such locations and arranged in such a manner as to prevent each technician from being exposed to hazardous differences in electrical potential.
Temporary protective grounds will be capable of conducting the maximum fault current that could flow at the point of grounding for the time necessary to clear the fault.
Temporary protective grounding equipment will meet the requirements of ASTM F 855, Standard Specification for Temporary Protective Grounds to be Used on De-energized Electric Power Lines and Equipment, 1997.
Temporary protective grounds will have an impedance low enough to cause immediate operation of protective devices in case of accidental energizing of the electric conductors or circuits parts.
The technician performing the maintenance action will be responsible for the establishment of the safe work area. The area must be set up prior to work commencing and must remain in place until the work is finished, unless a zero-energy state is established and lockout/tagout procedures followed.
Steps the technician should use include:
2. Review of posted arc flash label; information contained on this label will provide distance requirements for installation of required barriers
Examples of the arc flash labels are shown in Figure 8 and Figure 9.
Figure 8: Caution Label
Figure 9: Danger Label
The barrier should be set at the limited approach boundary or the flash hazard boundary distance indicated on the label, whichever is larger. No electrical enclosures should be opened until the safe work area has been established and all electrical workers inside the boundary are wearing the required PPE. This will put unqualified and qualified electrical workers not involved in the maintenance action adequate distance away from the possible incident energy release. The boundary will be spherical in nature on all open sides. The barrier tape does not need to extend through structural walls or solid floors. Steel-grated flooring must be treated as open space. The barrier tape must be installed high enough to impede the progress of the average individual. If the area includes high forklift traffic, posting an individual to warn away forklifts should be considered.
An electrically safe condition is a condition where the technician has proven, using approved test instruments, that no electrical energy remains in the equipment. This is referred to as a zero-energy state. The status of electrical equipment and components to which a qualified technician may be exposed to will be considered energized until tested and determined to be de-energized and lockout/tagout procedures followed.
The following steps should accomplish this as a minimum before work commences.
It is the responsibility of the employer to provide:
Workers must maintain alertness at all times when working near energized electrical conductors and circuit parts operating at 50 volts or more and in-work situations where unexpected electrical hazards might exist.
A technician will not knowingly be permitted to work in areas containing energized electrical conductors and circuit parts operating at 50 volts or more or other electrical hazards while their alertness is recognizably impaired due to illness, fatigue, or other reasons.
Technicians will be instructed not to reach blindly into areas that might contain exposed energized electrical conductors and circuit parts where an electrical hazard exists.
Technicians will not enter spaces containing energized electrical conductors or circuit parts unless sufficient illumination is provided to enable the technicians to perform the work safely.
Obstructed View of Work Area
Where lack of illumination or an obstruction precludes observation of the work to be performed, technicians will not perform any task near live parts operating at 50 volts or more or where an electrical hazard exists.
Conductive Articles Being Worn
Conductive articles of jewelry and clothing, such as watchbands, bracelets, rings, key chains, necklaces, radios, and ID badges, will not be worn where they present an electrical contact hazard with exposed energized electrical conductors and circuit parts. If a conductive article of jewelry cannot be removed, it must be insulated before donning any required PPE. The use of goggles is also permitted, provided the goggles meet ANSI Z87.1 2003 requirements.
Conductive materials, tools, and equipment that are in contact with any part of a technicians body will be handled in a manner that prevents accidental contact with energized electrical conductors and circuit parts. Such materials and equipment include, but are not limited to, long conductive objects, such as ducts, pipes, and tubes, conductive hoes and rope, metal-lined rules and scales, steel tapes, pulling lines, metal scaffold parts, structural members, bull floats, and chains.
Approach to Energized Electrical Conductors and Circuit Parts
Means will be employed to ensure that conductive materials approach exposed energized electrical conductors and circuit parts no closer than that permitted by Table 1.
Confined or Enclosed Work Spaces
When a technician works in a confined or enclosed space, such as a manhole or vault, that contains exposed energized electrical conductors or circuit parts operating at 50 volts or more, or an electrical hazard exists, the employer will provide, and the technician will use, protective shields, protective barriers, or insulating materials as necessary to avoid inadvertent contact with these parts. Doors and hinged panels will be secured to prevent them from swinging into a technician and causing the technician to contact exposed energized electrical conductors and circuit parts operating at 50 volts or more.
Where energized electrical conductors and circuit parts present an electrical contact hazard, technicians will not perform housekeeping duties inside the flash hazard boundary. Electrically conductive cleaning materials, including conductive solids such as steel wool, initialized cloth, and silicone carbide, as well as conductive liquid solutions, will not be used inside the flash hazard boundary unless procedures to prevent electrical contact are followed.
Occasional Use of Flammable Materials
Where flammable materials are present only occasionally, electric equipment capable of igniting them may not be used, unless measures are taken to prevent hazardous conditions from developing. Such materials include, but are not limited to, flammable gases, vapors, or liquids, combustible dust, and ignitable fibers or flyings.
When there is evidence that electric equipment could fail and injure technicians, the electric equipment will be de-energized. Until the equipment is de-energized or repaired, technicians will be protected from hazards associated with the impending failure of the equipment.
Routine Opening and Closing of Circuits
Load-rated switches, circuit breakers, or other devices specifically designed as disconnecting means will be used for the opening, reversing, or closing of circuits under load conditions. Cable connectors not of the load-break type, fuses, terminal lugs, and cable splice connections will not be permitted to be used for such purposes, except in an emergency.
Reclosing Circuits after Protective Device Operation
After a circuit is de-energized by a circuit protective device, the circuit will not be manually re-energized until it has been determined that the equipment and the circuit can be safely energized. The repetitive manual reclosing of circuit breakers or re-energizing circuits through replaced fuses will be prohibited. When it is determined from the design of the circuit and the overcurrent devices involved that the automatic operation of a device was caused by an overload rather than a fault condition, examination of the circuit or connected equipment will not be required before the circuit is re-energized.
Unqualified persons will not be permitted to enter spaces that are required to be accessible only to qualified electrical workers unless the electrical conductors and equipment involved are in an electrically safe work condition. This would include switchboard rooms when any of the covers on the equipment are removed.
Only qualified electrical workers will be permitted to defeat or bypass an electrical safety interlock under the following conditions.
Safety Signs and Tags
Safety signs, safety symbols, or accident prevention tags will be used where necessary to warn technicians about electrical hazards that might endanger them. Such signs and tags will meet the requirements of ANSI Standard Z535, Series of Standards for Safety Signs and Tags, given in Table 2. Safety signs, tags, and barricades used to indentify energized look-alike equipment can be employed as an additional preventive measure.
Barricades will be used in conjunction with safety signs where it is necessary to prevent or limit technician access to work areas containing energized electrical conductors or circuit parts. Conductive barricades will not be used where it might cause an electrical hazard. Barricades will be placed no closer than 4 feet or the flash hazard boundary, whichever is greater.
If signs and barricades do not provide sufficient warning and protection from electrical hazards, an attendant will be stationed to warn and protect technicians. The primary responsibility of an attendant providing manual signaling and alerting will be to keep unqualified electrical workers outside a work area where the unqualified electrical worker might be exposed to electrical hazards. An attendant will remain in the area as long as there is a potential for technicians to be exposed to the electrical hazards.
Where work performed on equipment that is de-energized and placed in an electrically safe condition exists in a work area with other energized equipment that is similar in size, shape, and construction, one of the these alerting methods - safety signs and tags, barricades, or attendants - will be employed to prevent the technician from entering look-alike equipment.
Technicians working in areas where electrical hazards are present will be provided with, and will use, protective equipment that is designed and constructed for the specific part of the body to be protected and for the work to be performed. The employer will ensure that the individuals required to use PPE are trained to inspect, don, care for, and know the life expectancy of the PPE. Individuals using the PPE should know the location of the required markings on the equipment to ensure they are using the right PPE for the hazard level of the exposure.
Care of Equipment
Protective equipment will be maintained in a safe, reliable condition. The protective equipment will be visually inspected before each use. Protective equipment will be stored in a manner to prevent damage from physically damaging conditions and from moisture, dust, or other deteriorating agents.
When a technician is working within the flash hazard boundary, he or she will wear protective clothing and other PPE in accordance with the posted arc flash label. All parts of the body inside the arc flash boundary will be protected.
Standards for Personal Protective Equipment
PPE will conform to the standards given in Table 2.
When FR clothing is worn to protect a technician, it will cover all ignitable clothing and allow for movement and visibility. Technicians will wear FR clothing wherever there is a possible exposure to an electric arc flash above the threshold incident energy level for a second-degree burn, 5 J/cm2 (1.2 cal/cm2).
Note: Such clothing can be provided as an arc flash suit jacket and arc flash pants, as shirts and pants, as coveralls, as a combination of jacket and pants or, for increased protection, as coveralls with jacket and pants. Various weight fabrics are available. Generally, the higher degree of protection is provided by heavier weight fabrics and/or layering combinations of one or more layers of FR clothing worn over flammable, non-melting clothing.
Table 3 lists examples of protective clothing systems and typical characteristics, including the degree of protection for various clothing. The protective clothing selected for the corresponding hazard/risk category number will have an arc rating of at least the value listed in the last column of the table.
Examples of some Category 1 to 4 PPE requirements are shown below in Figures 10-13. Please note these are for arc flash protection only, and the shock protection requirements are not included.
Figure 10: Category 1 PPE
Figure 11: Category 2 PPE
Figure 12: Category 3 PPE
Figure 13: Category 4 PPE
Clothing and equipment that provide worker protection from shock and arc flash hazards will be used. Clothing and equipment required for the degree of exposure will be permitted to be worn alone or integrated with flammable, non-melting apparel. If FR clothing is required, it will cover associated parts of the body, as well as all flammable apparel, while allowing movement and visibility. All PPE will be maintained in a sanitary and functionally effective condition. PPE equipment items will normally be used in conjunction with one another as a system to provide the appropriate level of protection. The preferred materials for electrical workers are 100% cotton, 100% wool, or cotton/wool blends.
Exception: An incidental amount of elastic used on non-melting fabric underwear or socks will be permitted.
Clothing will cover potentially exposed areas as completely as possible. Shirt sleeves will be fastened at the wrists, and shirts and jackets will be closed at the neck.
FR clothing will meet the requirements described below.
Note: FR materials, such as flame-retardant treated cotton, meta-aramid, para-aramid, and polybenzimidazole (PBI) fibers, provide thermal protection. These materials can ignite but will not continue to burn after the ignition source is removed. FR fabrics can reduce burn injuries during an arc flash exposure by providing a thermal barrier between the arc flash and the wearer.
There are several material options available that meet the caloric requirements for protection at the required hazard level. Clothing made for materials with the trade names of Indura, Indura Ultra Soft, and clothing that incorporates the use of Nomex, are acceptable provided the caloric rating of the material is displayed on the label or on a label on the outside of the clothing item and the rating on the label meets or exceeds the required level for the equipment being worked on. This training does not intend to recommend or disapprove of certain materials. The material selections, as with most items being created to fill a market, will continue to grow and expand. The final selection of the PPE, uniforms or coveralls, type of material, etc. will be left to the company.
Exception: Fiber blends that contain materials that melt, such as acetate, acrylic, nylon, polyester, polyethylene, polypropylene, and spandex, will be permitted if such blends in fabrics meet the requirements of ASTM F 1506, Standard Performance Specifications for Textile Material for Wearing Apparel for Use by Electrical Workers Exposed to Momentary Electric Arc and Related Thermal Hazards, and if such blends in fabrics do not exhibit evidence of a melting and sticking hazard during arc testing according to ASTM F 1959, Standard Test Method for Determining the Arc Thermal Performance Value of Materials for Clothing.
Exception: Non-melting, flammable (non-FR) materials will be permitted to be used as underlayers to FR clothing and will also be permitted to be used in Hazard/Risk Category 0.
Technicians will wear approved protective equipment for the eyes whenever there is danger of injury from electric arc, flashes, or flying objects resulting from electrical explosion.
All eye and face protection equipment will conform to ANSI Z87.1 - 2003 Practice for Occupational and Educational Eye and Face Protection. All protective eye wear will be non-conductive.
The use of an athletic safety strap is required for those individuals who wear safety glasses over prescription metal framed glasses. The use of goggles is also permitted provided the goggles meet ANSI Z87.1 2003 requirements. Face shields must also meet the ANSI requirements and be properly rated for arc exposure.
If the eye or face protective device exhibits broken parts, heat distortion, or excessive scratches on the lens, it will not be used. Defective items need to be properly disposed.
When exposed to electrical hazards of 50 volts or greater, a minimum of Class 0 (1,000 volt rated) rubber insulating gloves should be used. If the nominal system voltage is below 480VAC, Class 00 gloves, which are rated for 500 volts, could be used. It is recommended that only Class 0 gloves be used to avoid any confusion when donning the required PPE. At no time will the maximum use voltage rating of the glove class be exceeded. In 480 VAC electrical systems, the chance of the voltage spiking over 500 volts is always possible, thus exceeding the voltage level Class 00 gloves can be used at. Hand and arm protection will be worn where there is possible exposure to arc flash burn.
Gloves will conform to:
Maximum use voltage will conform to those listed in Table 4.
Rubber gloves will be air-tested before each use. To test gloves for pinholes and other damage, fill the glove with air, roll up the cuff of the glove to make a seal, and squeeze the glove. Then, hold the inflated glove close to the face and ear to feel and listen for air escaping from holes. A glove inflator may be used to inflate the glove, if available. If any glove fails the air test, it must be destroyed immediately and the failure reported in accordance with local procedures.
The gloves will be checked for a stamped test date. This date should not be more than six months old. If the time frame has been exceeded, the appropriate corrective action in accordance with local procedures must be taken. If the gloves are brand new and have never been issued, the stamped test date may be up to one year; however, if this time period has been exceeded, the gloves should not be issued before being retested.
Rubber gloves in service will be kept in canvas glove bags with gauntlet down. Gloves will not be folded, creased, or rolled while in storage. Gloves will be protected from heat, ozone, or prolonged exposure to the direct rays of the sun, and from contact with sharp articles or materials likely to damage gloves or cause deterioration of the rubber.
Rubber gloves should be cleaned on a regular basis. Clean only with mild, non-caustic, non-petroleum based soap and lukewarm water. Do not use solvents, oils, or grease on rubber gloves. Use detergents recommended by the manufacturers of the electrical protective equipment. Allow the outside of the glove to air dry, then turn the glove inside out and allow to dry completely before use.
The use of cotton liners worn under the insulated gloves is recommended to provide absorption of perspiration. In lieu of the cotton liner, certified petroleum-free talcum powder or corn starch may be used. Under no circumstances should baby powder be used.
Rubber gloves will be worn with leather protective gloves in all cases.
Technicians will wear non-conductive head protection whenever there is a danger of head injury from electric shock or burns due to contact with energized electrical conductors and circuit parts or from flying objects resulting from electrical explosion. Technicians will wear non-conductive protective equipment for the face, neck, and chin whenever there is a danger of injury from exposure to electric arcs or flashes or from flying objects resulting from electrical explosion.
Where insulated footwear is used as protection against step and touch potential, dielectric overshoes will be required. Insulated soles will not be used as primary electrical protection.
Hearing protection is now a required item. Ear canal inserts are the chosen form of hearing protection, and the muff-type of hearing protection is not to be used. There are no additional standards or requirements with specific levels of noise reduction or heat resistance currently available. The type shown in Figure 14 currently lists arc flash as a hazard it provides protection against.
Figure 14: Recommended Hearing Protection
When the yellow end is inserted into the ear, it provides a hear-through filter that will allow for normal conversation, but will quickly close in the event of an arc flash and reduce the sound to a safer level. They are reusable. The red end provides a constant noise reduction of 23dB.
This section covers the requirements for test equipment, portable equipment, insulated tools, and other items that may be used in the performance of electrical work.