State four factors that determine the severity of an electrical shock.
- The severity of an electrical shock depends on the amount of electric current in milliamps (mA) that flows through the body, the length of time the body is exposed to the current flow, the path the current takes through the body, and the physical size and condition of the body through which the current passes.
Explain the three approach boundaries as identified by NFPA 70E®.
- NFPA 70E® identifies three approach boundaries to protect against electrical shock. These boundaries are the limited approach boundary, restricted approach boundary, and prohibited approach boundary. Each boundary is viewed as a sphere, extending 360° around an exposed energized conductor or circuit part. The size of each boundary is based on the phase-to-phase nominal voltage of the energized conductor or circuit part.
- The limited approach boundary is the distance from an exposed energized conductor or circuit part at which a person can get an electric shock and is the closest distance an unqualified person can approach.
- The restricted approach boundary is the distance from an exposed energized conductor or circuit part where an increased risk of electric shock exists due to the close proximity of the person to the energized conductor or circuit part.
- The prohibited approach boundary is the distance from an exposed energized conductor or circuit part inside which any work performed is considered the same as making contact with the energized conductor or circuit part.
State three ways to help prevent an unwanted electrostatic discharge (ESD) from damaging equipment.
- Electrostatic discharge (ESD) is the movement of electrons from a source to an object across a gap.
- When removing or replacing an ESD device or assembly in equipment, the device or assembly should be held with an electrostatic-free wrap, if possible. Otherwise, the device or assembly should be picked up by its body only. Component leads, connector pins, paths, PC boards, and any other electrical connections should not be touched, even though they are covered by a coating.
Identify the meanings of the different colors used with safety labels.
- A safety label is a label that indicates areas or tasks that can pose a hazard to personnel and/or equipment.
- A danger signal word is a word used to indicate an imminently hazardous situation which, if not avoided, results in death or serious injury. The danger symbol is an exclamation mark enclosed in a triangle followed by the word “danger” written boldly in a red box.
- A warning signal word is a word used to indicate a potentially hazardous situation which, if not avoided, could result in death or serious injury. The warning symbol is an exclamation mark enclosed in a triangle followed by the word “warning” written boldly in an orange box.
- A caution signal word is a word used to indicate a potentially hazardous situation which, if not avoided, may result in minor or moderate injury. The caution symbol is an exclamation mark enclosed in a triangle followed by the word “caution” written boldly in a yellow box.
- Electrical warning signal word is a word used to indicate a high-voltage location and conditions that could result in death or serious personal injury from an electrical shock if proper precautions are not taken. The electrical warning symbol is a lightning bolt enclosed in a triangle.
- Explosion warning signal word is a word used to indicate locations and conditions where exploding parts may cause death or serious personal injury if proper precautions and procedures are not followed. The explosion warning symbol is an explosion enclosed in a triangle.
List the basic electric motor safety rules.
- Two areas requiring attention when working with electric motors are the electrical circuit and rotating shaft. Basic electric motor safety rules include the following:
- Connect a motor to the correct grounding system.
- Ensure that guards or housings cover the rotating parts of a motor or anything connected to the motor.
- Use the correct motor type for the location.
- Connect a motor to the correct voltage and power source.
– Provide the motor with the correct overload and overcurrent protection to protect the motor when starting or shorted (overcurrent protection) and when running (overload protection).
State where and when a lockout/tagout device should be used.
- Lockout is the process of removing the source of electrical power and installing a lock that prevents the power from being turned on.
- Tagout is the process of placing a danger tag on the source of electrical power, which indicates that the equipment may not be operated until the danger tag is removed.
- Lockout/tagout is used when to perform a task, power is not required to be ON for a piece of equipment.
- Lockout/tagout is used when machine guards or other safety devices are removed or bypassed.
- Lockout/tagout is used when the possibility exists of being injured or caught in moving machinery.
- Lockout/tagout is used when jammed equipment is being cleared.
- Lockout/tagout is used when danger exists of being injured if equipment power is turned on.
Describe the different types of lockout devices.
- Lockout devices are lightweight enclosures that allow the lockout of standard control devices. Lockout devices resist chemicals, cracking, abrasion, and temperature changes.
- Danger tags provide additional lockout and warning information. Danger tags may include warnings such as “Do Not Start” or “Do Not Operate,” or they may provide space to enter worker name, date, and reason for lockout.
- A lockout/tagout kit contains items required to comply with OSHA lockout/tagout standards. Lockout/tagout kits contain reusable danger tags, multiple lockouts, locks, magnetic signs, and information on lockout/tagout procedures.
State the purpose of applying NFPA 70E® standards.
- The National Fire Protection Association (NFPA) standard NFPA 70E®, Standard for Electrical Safety in the Workplace, addresses “work practices that are necessary to provide a practical safe workplace relative to the hazards associated with electrical energy.”
- NFPA 70E® was written at the request of OSHA and has become the standard for electrical safety in the electrical industry. Its methods for protection are more detailed than OSHA requirements.
- For technicians, NFPA 70E® addresses requirements such as personal protective equipment (PPE) and safe approach distance requirements that could be encountered in jobs such as installing temporary power.
- To prevent an accident, electrical shock, or damage to equipment, all electrical work must be performed by qualified persons. NFPA 70E® Section 110.2(D)(1), Qualified Person, provides additional information regarding the definition of a qualified person.
Personal Protective Equipment
Describe the types of personal protective equipment (PPE).
- Personal protective equipment (PPE) is clothing and/or equipment worn by a technician to reduce the possibility of injury in the work area. PPE includes protective clothing, head protection, eye protection, ear protection, hand protection, foot protection, back protection, knee protection, and rubber insulated matting.
- Protective clothing is clothing that provides protection from contact with sharp objects, hot equipment, and harmful materials.
- Approved arc-rated clothing must be worn for protection from electrical arcs when performing certain operations on or near energized equipment or circuits.
Define arc flash and arc blast and how to minimize their effects.
- An arc flash is an extremely high-temperature discharge produced by an electrical fault in the air.
- An arc blast is an explosion that occurs when the air surrounding electrical equipment becomes ionized and conductive.
- To prevent an arc blast or arc flash, an electrical system needs to be de-energized, locked out, and tagged out prior to performing work.
- The arc flash boundary is the distance from exposed energized conductors or circuit parts where bare skin would receive the onset of a second-degree burn. The arc flash boundary is dependent on the available short-circuit current, maximum total clearing time of the OCPD, the voltage of the circuit, and a standard factor that varies if the actual short-circuit current is known or not known.
List the different types of head, eye, and ear protection.
- A protective helmet is a hard hat that is used in the workplace to prevent injury from the impact of falling and flying objects and from electrical shock. Protective helmets are identified by class of protection against specific hazardous conditions.
- Safety glasses are an eye protection device with special impact-resistant glass or plastic lenses, reinforced frames, and side shields.
- Aface shield is an eye and face protection device that covers the entire face with a plastic shield and is used for protection from flying objects.
- Goggles are an eye protection device with a flexible frame that is secured on the face with an elastic headband.
- An arc-rated hood is an eye and face protection device that covers the entire head and is used for protection from arc blast and arc flash.
- An earplug is an ear protection device made of moldable rubber, foam, or plastic and inserted into the ear canal. An earmuff is an ear protection device worn over the ears.
State the different parts of hand protection used to prevent an electrical shock and the purpose of each part.
- Rubber insulating gloves are gloves made of latex rubber and are used to provide maximum insulation from electrical shock.
- Rubber insulating gloves offer a high resistance to current flow to help prevent an electrical shock.
- The entire surface of rubber insulating gloves must be field tested (visual inspection and air test) before each use. In addition, rubber insulating gloves should also be laboratory tested by an approved laboratory every six months.
- Leather protectors are gloves worn over rubber insulating gloves to prevent penetration of the rubber insulating gloves and provide added protection against electrical shock.
- Leather protectors should be inspected when inspecting rubber insulating gloves. Metal particles or any substance that could physically damage rubber insulating gloves must be removed from a leather protector before it is used.
- Proper care of leather protectors is essential for user safety. Leather protectors are checked for cuts, tears, holes, abrasions, defective or worn stitching, oil contamination, and any other condition that might prevent them from adequately protecting rubber insulating gloves.
List the different types of foot, back, and knee protection.
- Foot protection is shoes worn to prevent foot injuries that are typically caused by objects falling less than 4″ and having an average weight of less than 65 lb. Safety shoes with reinforced steel toes protect against injuries caused by compression and impact. Insulated rubber-soled shoes are commonly worn during electrical work to prevent electrical shock.
- Back injuries are prevented through proper planning and work procedures.
- Assistance should be sought when moving heavy objects.
- When lifting objects from the ground, ensure the path is clear of obstacles and free of hazards.
- When lifting objects, the knees are bent and the object is grasped firmly. The object is lifted by straightening the legs and keeping the back as straight as possible. Keep the load close to the body and keep the load steady.
- A knee pad is a rubber, leather, or plastic pad strapped onto the knees for protection.
State the purpose of the National Electrical Code® (NEC®) and the Article that covers the requirements for motors.
- The National Electrical Code® (NEC®) is one of the most widely used and recognized consensus standards in the world. The purpose of the NEC® is to protect people and property from hazards that arise from the use of electricity.
- Many city, county, state, and federal agencies use the NEC® to set requirements for electrical installations.
State the purpose of grounding.
- Grounding is the connection of all exposed non-current-carrying metal parts to the earth.
- Electrical circuits are grounded to safeguard equipment and personnel against the hazards of electrical shock. Proper grounding of electrical tools, motors, equipment, enclosures, and other control circuitry helps prevent hazardous conditions.
- Grounding is accomplished by connecting the circuit to a metal underground water pipe, the metal frame of a building, a concrete-encased electrode, or a ground ring in accordance with the NEC®.
Explain how a ground fault circuit interrupter (GFCI) protects individuals.
- A ground fault circuit interrupter (GFCI) is a device that protects against electrical shock by detecting an imbalance of current in the normal conductor pathways and opening the circuit.
- When current in the two conductors of an electrical circuit varies by more than 5 mA, a GFCI opens the circuit. A GFCI is rated to trip quickly enough (1/40 of a second) to prevent electrocution.
- A GFCI compares the amount of current in the ungrounded (hot) conductor with the amount of current in the neutral conductor. If the current in the neutral conductor becomes less than the current in the hot conductor, a ground fault condition exists.
- A GFCI protects against the most common form of electrical shock hazard, the ground fault. A GFCI does not protect against line-to-line contact hazards, such as a technician holding two hot wires or a hot and a neutral wire in each hand.
State the different classes of fires, specifically the electrical fire classification.
- The five classes of fires are Class A, Class B, Class C, Class D, and Class K.
- Class A fires include burning wood, paper, textiles, and other ordinary combustible materials containing carbon.
- Class B fires include burning oil, gas, grease, paint, and other liquids that convert to a gas when heated.
- Class C fires include burning electrical devices, motors, and transformers.
- Class D is a specialized class of fires that includes burning metals such as zirconium, titanium, magnesium, sodium, and potassium.
- Class K fires include grease in commercial cooking equipment.
State possible materials that create a hazardous location and how hazardous locations are identified.
- The use of electrical equipment in areas where explosion hazards are present can lead to an explosion and fire. This danger exists in the form of escaped flammable gases such as naphtha, benzene, propane, and others. Coal, grain, and other dust suspended in the air can also cause an explosion.
- Any hazardous location requires the maximum in safety and adherence to local, state, and federal guidelines and laws, as well as in-plant safety rules.
- Hazardous locations are indicated by Class, Division, and Group.
Define confined space and state several ways to help prevent an accident in a confined space.
- A confined space is a space large enough and so configured that an employee can physically enter and perform assigned work, which has limited or restricted means for entry and exit, and is not designed for continuous employee occupancy.
- Confined spaces include, but are not limited to, storage tanks, process vessels, bins, boilers, ventilation or exhaust ducts, sewers, underground utility vaults, tunnels, pipelines, and open top spaces such as pits, tubes, ditches, and vaults more than 4′ in depth.
- Confined spaces cause entrapment hazards and life-threatening atmospheres through oxygen deficiency, combustible gases, and/or toxic gases.
- OSHA 29 CFR 1910.146 – Permit-Required Confined Spaces contains the requirements for practices and procedures to protect workers from the hazards of entry into permit-required confined spaces.
- Permit-required confined spaces are grouped into the categories of containing or having a potential to contain a hazardous atmosphere, containing a material that has the potential for engulfing an entrant, having an internal configuration such that an entrant could be trapped or asphyxiated by inwardly converging walls or a floor that slopes downward and tapers into a smaller cross-section, or containing any other recognized safety or health hazard.
- A non-permit confined space is a confined space that does not contain or, with respect to atmospheric hazards, have the potential to contain any hazards capable of causing death or serious physical harm.
- An entry permit must be posted at confined space entrances or otherwise made available to entrants before entering a permit-required confined space. The permit is signed by the entry supervisor and verifies that pre-entry preparations have been completed and that the space is safe to enter. A permit-required confined space must be isolated before entry. Plant procedures for lockout/tagout of permit-required confined spaces must be followed.
Overhead Power Line Safety
Explain the importance of safety when working on overhead power lines.
- Overhead power lines are electrical conductors designed to deliver electrical power and that are located in an aboveground aerial position.
- People are killed every day from accidental contact with overhead power lines.
- Electrical power lines should be located far enough overhead or out of reach as to not pose an electrical hazard. Electrical equipment such as transformers and power panels are also isolated by fences, locked in buildings, or buried underground.
- Per NFPA 70E®, if the line voltage exceeds 50 kV, the minimum overhead line clearance for all nonqualified individuals is 10′ plus 4″ for every 10 kV over 50 kV.