2OSHA – General Industry Electrical29 CFR 1910 Subpart S
3ElectricalAn average of one worker is electrocuted on the job every dayThere are four main types of electrical injuries:ElectrocutionElectrical shockBurnsFalls
4Electrical Terminology Current – the movement of electrical chargeResistance – opposition to current flowVoltage – a measure of electrical forceConductors – substances, such as metals, that have little resistance to electricityInsulators – substances; such as wood, rubber, and glass, that have high resistance to electricityGrounding – a conductive connection to the earth which acts as a protective measure
5ElectricityWhen operating an electric switch, the source of the electricity is the power generating station; current travels through wires (electric conductors); and voltage, provided by a generator, provides the force to make it flow
6ResistanceDry skin has a fairly high resistance, but when moist, resistance drops radically, making it a ready conductorPure water is a poor conductor, but small amounts of impurities, such as salt and acid (both of which are contained in perspiration), make it a ready conductor
7Electrical Shock Received when current passes through the body Severity of the shock depends on:Path of current through the bodyAmount of current flowing through the bodyLength of time the body is in the circuitLOW VOLTAGE DOES NOT MEAN LOW HAZARD (can still be extremely dangerous depending on amount of time body is in contact with the circuit)
8Dangers of Electrical Shock Currents greater than 75 mA* can cause ventricular fibrillation (rapid, ineffective heartbeat)Will cause death in a few minutes unless a defibrillator is used75 mA is not much current – a small power drill uses 30 times as much*mA = milliampere = 1/1,000 of an ampere
9How is an Electrical Shock Received? When two wires have different potential differences (voltages), current will flow if they are connected togetherIn most household wiring, the black wires are at 110 volts relative to groundThe white wires are at zero volts because they are connected to groundIf you come into contact with an energized (live) black wire, and you are also in contact with the white grounded wire, current will pass through your body and you will receive a shock
10How is an Electrical Shock Received? Electricity travels in closed circuits, and its normal route is through a conductorElectric shock occurs when the body becomes a part of the circuitElectric shock normally occurs in one of three ways when an individual is in contact with the ground and contacts:Both wires of an electric circuit, orOne wire of an energized circuit and the ground, orA metallic part that has become energized by contact with an energized conductor
11How is an Electrical Shock Received? If you are in contact with an energized wire or any energized electrical component, and also with any grounded object, you will receive a shockYou can even receive a shock when you are not in contact with a groundIf you contact both wires of a 240-volt cable, you will receive a shock and possibly be electrocuted
12Electrical Burns Most common shock-related nonfatal injury Occurs when you touch electrical wiring or equipment that is improperly used or maintainedTypically occurs on the handsVery serious injury that needs immediate attention
13Falls Electric shock can also cause indirect or secondary injuries Workers in elevated locations who experience a shock can fall, resulting in serious injury or death
14Inadequate Wiring Hazards A hazard exists when a conductor is too small to safely carry the currentExample: using a portable tool with an extension cord that has a wire too small for the toolThe tool will draw more current than the cord can handle, causing overheating and a possible fire without tripping the circuit breakerThe circuit breaker could be the right size for the circuit, but not for the smaller-wire extension cord (Wire-gauge size is inversely related to the diameter of the wire. For example, a No. 12 flexible cord has a larger diameter wire than a No. 14 flexible cord.)
15Overload HazardsIf too many devices are plugged into a circuit, the current will heat the wires to a very high temperature, which may cause a fireIf the wire insulation melts, arcing may occur and cause a fire in the area where the overload exists, even inside a wall
16Circuit BreakersIf the circuit breakers or fuses are too big (high current rating) for the wires they are supposed to protect, an overload in the circuit will not be detected and the current will not be shut off. A circuit with improper overcurrent protection devices – or one with no overcurrent protection devices at all – is a hazard.
17Electrical Protective Devices These devices shut off electricity flow in the event of an overload or ground-fault in the circuitInclude fuses, circuit breakers, and ground-fault circuit-interrupters (GFCI’s)Fuses and circuit breakers are overcurrent devicesWhen there is too much currentFuses meltCircuit breakers trip open
18Electrical Protective Devices The basic idea of an overcurrent device is to make a weak link in the circuit. In the case of a fuse, the fuse is destroyed before another part of the system is destroyed. In the case of a circuit breaker, a set of contacts opens the circuit. Unlike a fuse, a circuit breaker can be re-used by re-closing the contacts. Fuses and circuit breakers are designed to protect equipment and facilities, and in so doing, they also provide considerable protection against shock in most situations. However, the only electrical protective device whose sole purpose is to protect people is the ground-fault circuit-interrupter.
19Ground-Fault Circuit-Interrupter This device protects you from dangerous shockThe GFCI detects a difference in current between the black and white circuit wires (This could happen when electrical equipment is not working correctly, causing current “leakage” – known as a ground fault.)If a ground fault is detected, the GFCI can shut off electricity flow in as little as 1/40 of a second, protecting you from a dangerous shock
20Grounding Hazards Some of the most frequently violated OSHA standards Metal parts of an electrical wiring system that we touch (switch plates, ceiling light fixtures, conduit, etc.) should be at zero volts relative to groundHousings of motors, appliances or tools that are plugged into improperly grounded circuits may become energizedIf you come into contact with an improperly grounded electrical device, you will be shocked
21GroundingCurrent flows through a conductor if there is a difference in voltage (electrical force). If metal parts of an electrical wiring system are at zero volts relative to ground, no current will flow if our body completes the circuit between these parts and ground.
22Grounding Code Talk Shop Talk Wire Color Ungrounded Hot Black Grounded Neutral White or GrayGrounding Ground Green/Bare Copper
23Grounding (Cont’d) Two kinds of grounds are required by the standard: Service or system ground. In this instance, one wire – called the neutral conductor or ground conductor – is grounded. In an ordinary low-voltage circuit, the white (or gray) wire is grounded at the generator or transformer and again at the service entrance of the building. This type of ground is primarily designed to protect machines, tools, and insulation against damage.For enhanced worker protection, an additional ground, called the equipment ground, must be furnished by providing another path from the tool or machine through which the current can flow to the ground.
24Overhead Power-Line Hazards Most people don’t realize that overhead power lines are usually not insulatedPower-line workers need special training and personal protective equipment (PPE) to work safelyDo not use metal ladders – instead, use fiberglass laddersBeware of power lines when you work with ladders and scaffolding
25Electrical AccidentsAppear to be caused by a combination of three factors:Unsafe equipment and/or installation,Workplaces made unsafe by the environment, andUnsafe work practicesVarious ways of protecting people include: insulation, guarding, grounding, electrical protective devices, and safe work practices.
28Examples of Electrical Requirements 29 CFR29 CFR29 CFR
29Examples of Electrical Requirements Electrical equipment shall be free from recognized hazards that are likely to cause death or serious physical harm to employees
30Examples of Electrical Requirements Installation and useSplicesArcing partsMarkingIdentification of disconnecting meansWorking spaceGuarding of live parts
31Examples of Electrical Requirements Anything wrong with this?
32Examples of Electrical Requirements Anything wrong here?
33Examples of Electrical Requirements Anything need changed here?
34Examples of Electrical Requirements Other examples of electrical requirements include:
35Light Guards/CoversLights have to have covers or guards (The 7’ rule no longer applies)Violation shown here is light without a cover or guard
36Grounding PathThe path to ground from circuits, equipment, and enclosures must be permanent and continuousViolation shown here is an extension cord with a missing grounding prong
37Hand-Held Electric Tools Hand-held electric tools pose a potential danger because they make continuous good contact with the handTo protect you from shock, burns, and electrocution, tools must:Have a three-wire cord with ground and be plugged into a grounded receptacle, orBe double insulated (and distinctly marked as such), orBe powered by a low-voltage isolation transformer
38Hand-Held Electric Tools (Cont’d) Hazards of portable electric tools:Currents as small as 10 mA can paralyze, or “freeze” musclesPerson cannot release toolTool is held even more tightly, resulting in longer exposure to shocking currentPower drills use 30 times as much current as what will kill
39Hand-Held Electric Tools (Cont’d) GFCI outlets should be used for all handheld toolsDouble-insulated plastic tools can also result in electrocution
40Guarding of Live PartsMust guard live parts of electric equipment operating at 50 volts or more against accidental contact by:Approved cabinets/enclosures, orLocation or permanent partitions making them accessible only to qualified persons, orElevation of 8 ft. or more above the floor or working surfaceMark entrances to guarded locations with conspicuous warning signs
41Requirements if Over 600 Volts Must be contained in a room or screened or fenced area that is controlled by lock and key or other approved means accessible to qualified persons only. Areas containing exposed live parts over 600 volts shall be kept locked or shall be under the observation of a qualified person at all times and shall have posted warning signs.
42Qualified and Unqualified Persons Qualified person: one who has training in avoiding the electrical hazards of working on or near exposed energized partsUnqualified person: one with little or no such training
43Guarding of Live PartsMust enclose or guard electric equipment in locations where it would be exposed to physical damageViolation shown here is physical damage to conduit
44Cabinets, Boxes, and Fittings Junction boxes, pull boxes and fittings must have approved coversUnused openings in cabinets, boxes and fittings must be closed (no missing knockouts)Photos show violations of these two requirements
45Use of Flexible Cords More vulnerable than fixed wiring Do not use if one of the recognized wiring methods can be used insteadFlexible cords can be damaged by:AgingDoor or window edgesAbrasion from adjacent materialsActivities in the areaImproper use of flexible cords can cause shocks, burns or fire
46Permissible Uses of Flexible Cords Pendant, or Portable lamps, Stationary equipmentfixture wiring tools, or appliances to facilitate interchange
47Prohibited Uses of Flexible Cords Substitute for fixed wiringConcealed behind orattached to buildingsurfacesRun through walls,ceilings, floors, doors,or windows
48Flexible CordsExtension cords are for temporary and immediate use. If not going to be used within 30 minutes, the cord should be rolled up.
49Clues that Electrical Hazards Exist Tripped circuit breakers or blown fusesWarm tools, wires, cords, connections, or junction boxesGFCI that shuts off a circuitWorn or frayed insulation around wire or connection
50TrainingEmployees working with electric equipment shall be trained in safe work practices, including:De-energizing electric equipment before inspecting or making repairsUsing electric tools that are in good repairUsing good judgment when working near energized linesUsing appropriate protective equipment
51Work PracticesWork practices are for anyone who works on or near electricCovers both qualified and unqualified persons
52Electrical Gloves If using electrical gloves, Gloves are to be tested every 6 months at a specific labA visual and air check should be done before every shift
53Summary Hazards include: Inadequate wiring Wires with bad insulation Ungrounded electrical systems and toolsOverloaded circuitsDamaged power tools and equipmentUsing the wrong PPE and toolsOverhead power linesAll hazards are made worse in wet conditions
54Summary (Cont’d) Protective measures include: Proper grounding Using GFCI’sUsing fuses and circuit breakersGuarding live partsProper use of flexible cordsTraining
55QuizWhat are four types of injuries that may result from contact with electricity?Electrocution (death)Electrical shockBurnsFalls
56QuizWhat are the three main electrical hazards that may be encountered at a worksite?Inadequate wiringImproper groundingOverloads
57Quiz What are three methods of protection from electrical hazards? Use proper sized fuses, circuit breakers, and GFCI’sNever disconnect the ground wire from a plugInspect all flexible cords before useGuard live electrical partsUse proper groundingTrain workersShut off electricity at the source before doing electrical work - use lockout/tagout procedures
58Quiz What is the function of a GFCI? Detect current leakage and then switch off currentMatches amount of current going to device against amount returning, and if different, it switches circuit off
59QuizWhat are three warning signs or clues that an electrical hazard exists?GFCI that shuts off a circuitTripped circuit breakers or blown fusesWarm tools, wires, cords, or connection boxesWorn or frayed insulation around a wire or connection
61De-Energizing Electrical Equipment The accidental or unexpected sudden starting of electrical equipment can cause severe injury or death. Before ANY inspections or repairs are made the current must be turned off at the switch box and the switch padlocked in the OFF position. At the same time, the switch or controls of the machine or other equipment being locked out of service must be securely tagged to show which equipment or circuits are being worked on.
62What is Lockout/Tagout? A system to prevent release of energy or operation of machinery/equipment and provide warning to other employees that equipment is being worked on
63LockoutLockout:The placement of a device that blocks the flow of energy from a power source to the equipment
64TagoutTagout:The placement of a tag near the lockout device to warn others not to restore energy to the equipment
65Why Use Lockout/Tagout? Six percent of workplace fatalities result from the unexpected activation of a machine or piece of equipment during servicing and maintenance (according to Department of Labor)More than 25,000 workdays are lost each year due to failure to isolate equipment from energy sources
66Types of Lockout Devices LocksBlocksChainsMultilock haspsWheel valve coversBall valve coversSwitch and outlet coversPneumatic/Plug covers
75When Must Lockout/Tagout Be Used? When servicing or maintaining equipment where:Hazardous energy existsUnexpected start-up could occurEither of these could harm an employee
76When Shall Lockout/Tagout Be Used? Lockout/Tagout shall be used when:Employees are required to remove or bypass a safety device or guardEmployees are required to place any part of their body in harm’s wayEmployees are exposed to hazardous energy
77Lockout/Tagout Exceptions Work where hazardous energy does not existActivities performed during routine production processesWork on cord- and plug-controlled devices when the plug is under the exclusive control of the employee operating or maintaining the equipmentHot tap operations where shutdown is not feasible
78Affected and Authorized Employees Affected employees:OperateWork aroundOccasionally adjust equipment that is subject to lockout/tagoutAuthorized employee:Maintains equipmentServices equipmentIs trained to use lockout/tagout
79Affected Employee Responsibilities Notify maintenance, etc., when equipment needs repair or adjustmentLeave all lockout/tagout devices in placeVerify equipment is safe to operate following lockout/tagoutFollow all safety rules while operating the equipment
80Authorized Employee Responsibilities Repair or service equipment as neededEnsure that all energy sources are locked outTest equipment to verify residual energy is dissipatedPlace a “Danger—Do Not Operate” tag on equipmentObtain assistance when necessaryRemove locks and/or tags following lockout/tagoutCoordinate multi-shift repair
81Employer Responsibilities Maintain written programEnsure de-energization of equipmentEnsure employee awarenessProvide appropriate levels of trainingReview program effectivenessMaintain and revise programAdminister appropriate disciplinary actions
82Training Requirements Authorized employees—initially and at least annuallyAffected employees—at least initiallyAuthorized and affected—whenever changes are made to jobs or proceduresAuthorized and affected—when program deficiencies are notedMaintain written records of training
83SummaryLockout/Tagout is a system to prevent release of energy or operation of equipment and provide warning to other employees that the equipment is being worked onThe written Lockout/Tagout program should be reviewed at least annuallyTraining on the Lockout/Tagout program must be done
84Quiz What is lockout/tagout? A system to prevent release of energy or operation of machinery/equipment and provide warning to other employees that equipment is being worked on
85Quiz When must lockout/tagout be used? When servicing or maintaining equipment where hazardous energy exists, unexpected start-up could occur, and either of these could harm an employee
86Quiz Who may remove a lockout/tagout device? Only the authorized employee who placed the device