MODULE 12: FOCUS FOUR - Electrical Safety

The need for electrical safety awareness is demonstrated by the fact that out of every 100 young workers who die on the job, _____ are killed by electricity.

12 More than five workers are electrocuted every week, and electricity causes 12 percent of young worker deaths in the workplace.

Workers who use compressed air for cleaning should limit pressure to _____ PSI.

30 For safe cleaning or dusting of clothing with compressed air the p.s.i. setting must not exceed 30 p.s.i.

Safety nets must be installed no further than___feet under the walking/working surface on which employees are working.

30 Safety nets must be provided for workplaces that are more than 30 feet above the ground or water surface.

Never allow workers to enter an unprotected trench that is _____ feet or deeper unless an adequate protective system is in place.

5 Never allow workers to enter an unprotected trench that is 5 feet or deeper unless an adequate protective system is in place. Always follow your employer's safety policies.

OSHA estimates that ______ percent of struck-by fatalities involve heavy equipment like trucks or cranes.

75 OSHA estimates that 75 percent of struck-by fatalities involve heavy equipment like trucks or cranes. Always pay attention to your surroundings. Do not assume you have been seen by an operator.

If ground fault is detected, a GFCI shuts off electricity in _____ of a second.

1/40th If a ground fault is detected, a GFCI shuts off electricity in 1/40th of a second.

Of the burns caused by electricity, which type is the result of an explosion near the body that can generate heat up to four times hotter than the sun?

Arc Arc or flash burns result from high temperatures caused by an electric arc or explosion near the body which creates intense heat and may even cause an explosion. The heat generated can be up to six times the amount of heat produced from other thermal sources, such as flash fires. This type of injury requires attention immediately.

A worker on a jobsite is told by a supervisor to back a loaded truck into position for unloading, but the rear view is obstructed by the load. What is the worker's safest course of action?

Ask coworkers to be flaggers Improper operation of heavy vehicles poses a life-threatening danger to construction workers. Always station flaggers behind vehicles that have obstructed rear views.

When vehicles are to be parked on an incline and left unattended, the operator must ensure all these safety controls are in place EXCEPT:

Back-up alarm is activated. When vehicles are to be parked on an incline and left unattended, the operator must ensure the ignition is turned off, all equipment, including accessories, is blocked, parking brakes are set and wheels are chocked.

According to statistics, what is the most common electricity-related direct injury?

Burns The most common electricity-related injury is a burn. They occur when a person touches electrical wiring or equipment that is improperly used or maintained.

Special insulated tools

Steve will be working on fuses with energized terminals. Use special insulated tools when working on fuses with energized terminals with an electrical work permit.

A crane load blown by wind There are several common types of struck-by hazard

Swinging

Being hit by the boom of a crane There are several common types of struck-by hazard

Swinging

Which of the following statements about electrical shocks is CORRECT?

The severity of the shock depends on the path of the current through the body. The severity of the shock depends on the path of current through the body, the amount of current (amps) flowing through the body, and the duration of the current's travel through the body.

For trench collapse prevention, OSHA has approved all these systems EXCEPT:

Railing Systems that are used to keep trenches from collapsing include sloping, shoring, benching, and trench shield systems.

A collapsing stack of water pipes There are several common types of struck-by hazard

Rolling

Being hit by a truck while unloading freight There are several common types of struck-by hazard

Rolling

Being run over by a tractor trailer There are several common types of struck-by hazard

Rolling

Disconnect the drill when you are changing bits.

Safe

Use an electric stone cutter in a dry, well-lit place.

Safe

You automatically assume that all overhead wires are energized at lethal voltages.

Safe Assume that all overhead wires are energized at lethal voltages.

You never operate electrical equipment while you are standing in water.

Safe Never operate electrical equipment while you are standing in water.

You don't repair electrical cords or equipment because you are not qualified and authorized yet.

Safe Never repair electrical cords or equipment unless qualified and authorized. Before you energize electrical equipment that has gotten wet, have a qualified electrician inspect it.

When the height of workplaces exceeds 30 feet above ground, what safety device must be provided for workers?

Safety nets Safety nets must be provided to workers exposed to fall hazards of 30 feet or more.

Which one of the following methods MOST effectively protects machines, tools, and operators against damage from electrical current?

Service and equipment grounding Proper service and equipment grounding is necessary for protecting operators and equipment from electrical currents.

The immense weight of a masonry wall or slab can cause a fatal accident if proper safeguards are not in place

Set up a limited access zone around the operations to keep non-essential workers away, Adequately shore or brace structures until they are permanently supported, Use automatic holding devices for backup support when using lifts. The proper safeguards for working around masonry related construction include: Set up a limited access zone around the operations to keep nonessentional workers away. Adequately shore or brace structures until they are permanently supported. Use automatic holding devices for backup support when using lifts.

Working with electricity can be hazardous if you are not properly trained and protected. A person is exposed to which of the following as a result of an electrical hazard?

Shock, Burn, Electrocution, and Fire Employees working near electricity may be exposed to electric shock, electrocution, burns, fires, and explosions.

Protective systems must be in place if workers will be entering trenches and excavations that are a minimum of _____ feet deep.

Five Never allow workers to enter an unprotected trench (or excavation) that is five feet or deeper unless an adequate protective system is in place; in some cases, trenches less than five feet deep may also require such a system.

What is an acceptable alternative to installing an audible back-up alarm?

Flaggers The presence of flaggers is the only acceptable alternative to installing an audible back-up alarm.

Electrical current

Flow of electrons from a voltage source and back to the source Electrical current is the flow of electrons from a voltage source and back to the source. It requires a source of voltage, a circuit path through a conductor, and a load that uses the current flow as work.

A nail ejected from a nail gun There are several common types of struck-by hazard

Flying

Sawdust blown by compressed air There are several common types of struck-by hazard

Flying

Circuit-opening fusible part is heated and severed by the passage of overcurrent through that part.

Fuses Fuses are overcurrent protective devices with a circuit-opening fusible part that is heated and severed by the passage of overcurrent through that part.

Which one of the following circuit interrupts is most effective at preventing major shocks?

GFCI GFCI is the right answer because others cannot shut down electricity immediately.

Detects differences in current as small as 4 mA between the black and white wires.

GFCIs A ground fault circuit interrupter (GFCI) can detect differences in current as small as 5 mA between the black and white wires. It will shut off electricity in 1/40th of a second if a ground fault is detected.

De-energizes a circuit in 1/40th of a second when a current to ground exceeds a predetermined value.

GFCIs A ground fault circuit interrupter (GFCI) shuts off electricity in 1/40th of a second if a ground fault is detected.

What essential construction protective device presents the greatest risk for causing a caught in between hazard?

Guardrails Guardrail requirements can actually create a hazard at the leading edge of installed floor or roof sections by creating the potential for employees to be caught in between guardrails and suspended loads.

Under certain circumstances, which one of these engineering controls can create a caught-between hazard?

Guardrails Guardrails in certain situations have been known to cause caught-between hazards.

Electrical burns typically occur on the _____.

Hands Hands are usually the part of the human body most often in contact with tools or equipment and therefore suffer a greater risk for electrical burns.

Test the power line to check if it is energized In order to minimize the risk of accidents around power lines, you should know which of the following steps are correct or incorrect.

No Never touch an overhead power line. Call the electric utility company to report fallen electrical lines.

Opens and closes a circuit without damage to the device when properly applied within its rating.

CBs A circuit breaker opens and closes a circuit without damage to itself when properly applied within its rating. Circuit breakers are capable of making, carrying, and breaking currents under normal circuit conditions and of breaking currents under specified abnormal circuit conditions.

Currents can be reset under certain abnormal circuit conditions, such as those of a short circuit.

CBs Circuit breakers are designed to open and close a circuit by nonautomatic means. They are capable of carrying and breaking currents under normal circuit conditions and of breaking currents under specified abnormal circuit conditions.

Working with electricity can be hazardous if you are not properly trained and protected. Which of the following PPE should be used when conducting electrical work?

Class E hard hat, Non-conductive gloves, ASTM rated boots When conducting electrical work, remember to use the proper PPE, such as Class B hard hats, non-conductive gloves, and ASTM rated boots.

Shoring

Collapsing trench edge

Arc flash incident

Concentrated radiant energy explodes outward from electrical equipment, creating pressure waves Think of arc flash as a short circuit through the air. In an arc flash incident, a large amount of concentrated radiant energy explodes outward from electrical equipment, creating pressure waves.

Remove by pulling on the plug

Cords and Wires Cords should be removed by pulling on the plugs, not on the cords.

Strain relief

Cords and Wires Extension cords may have damaged insulation. Sometimes, the insulation inside of an electrical tool or appliance is damaged. Only cords, connection devices, and fittings equipped with strain relief should be used.

Marked for hard or extra-hard usage

Cords and Wires Only cords marked for hard or extra-hard usage (as designated by "S" at the beginning of the cord type; SJ indicates junior hard usage) should be used.

Tag deactivated controls and power sources.

Correct These steps must be performed when locking out and tagging out circuits: apply locks and tags to the power source after de-energizing, and verify that the circuit is de-energized by testing with known, functioning meters.

Use tags to identify the equipment or circuits being worked on.

Correct When locking out and tagging out circuits, tags must identify equipment or circuits being worked on.

Verify that the circuit is de-energized by testing with known, functioning meters.

Correct When locking out and tagging out circuits, verify that the circuit is de-energized by testing with known, functioning meters.

Incident energy

Current travels through free air, and the effects of the energy are not contained Because the current is not contained within a conductor but travels through free air, the effects of the energy are not contained. Such uncontained energy is referred to as incident energy.

Flaggers

Driving a dump truck It's a good idea to put flaggers behind vehicles that have obstructed rear views.

Back-up Alarms

Driving a dump truck Vehicle back-up alarms warn people to get out of the way. Vehicles may have blind spots. A driver looking in one direction may not see someone moving along the opposite side. Alarms can help ensure that everyone in the area is alerted as to the vehicle's movement.

Chock Wheels

Driving a dump truck When you're using heavy vehicles you'll need to set the parking brakes and if parked on an incline, use chock wheels to help ensure that the vehicle's wheels do not move.

What type of burns are the result of current flowing through and exiting the body?

Electrical Electrical burns are the result of an electrical current entering and exiting the body.

Electrical shock

Electrical current passes through the body to complete an electrical circuit An electric shock is received when electrical current passes through the body. You will get an electrical shock if parts of your body complete an electrical circuit.

How does electricity work?

Electrons flow from a voltage source through a conductor and back to the source. Electrical current is the flow of electrons from a voltage source and back to the source.

Energized Electrical Work Permit

Energized work must be done because de-energizing would be riskier. To justify energized work, an employer must demonstrate that de-energizing introduces additional or increased hazards or is not possible due to equipment design or operational limitations.

In order to limit or eliminate struck-by accidents the following safe practices should be followed to save lives

Enforce the use of proper PPE, Use vehicle backup alarms, Install debris nets beneath overhead work, Keep workers away from temporary overhead activities. The safe work practices that should be followed to eliminate struck-by accidents include: Enforce the use of proper PPE Use vehicle backup alarms Install debris nets beneath overhead work Keep workers away from temporary overhead activities

When struck-by and caught-between hazards are high, in order to decrease the risk of worker injury, only _____ personnel should be allowed in the hazardous area.

Essential To decrease the risk of worker injury when struck-by and caught-between hazards are high, only essential personnel should be allowed in the hazardous area.

Which one of these hazards is NOT among OSHA's top four causes of construction site fatalities?

Explosions OSHA's Web site states that the top four causes of construction fatalities are a result of falls, struck by, caught in between, and electrocution.

Put eight feet or more above the floor

Exposed Parts Live parts of electrical equipment operating at 50 volts or more may be guarded against accidental contact by putting them at an elevation of eight feet or more above the floor or other working surface and installed so as to exclude unqualified persons.

Restricted room or platform

Exposed Parts Live parts of electrical equipment operating at 50 volts or more must be guarded against accidental contact by cabinets or other forms of enclosures or by location in a room, vault, or similar enclosure that is accessible only to qualified persons.

Screens that prevent contact

Exposed Parts Live parts of electrical equipment operating at 50 volts or more must be guarded against accidental contact by partitions or screens so arranged that only qualified persons will have access to the space within reach of the live parts.

A hammer dropped from a scaffold There are several common types of struck-by hazard

Falling

Bricks tumbling from a masonry wall There are several common types of struck-by hazard

Falling

Debris blown off a roof There are several common types of struck-by hazard

Falling

More people on construction job sites are killed by _____ hazards than any other cause.

Falls Falls are the leading fatality-causing hazard in the construction industry.

A worker comes in contact with live electrical parts and is shocked but receives no major injuries. What would be the MOST LIKELY reason he suffered no electricity-related injuries?

He was wearing nonconductive safety shoes. The worker did not suffer any major injuries because he was wearing nonconductive safety shoes.

According to OSHA statistics, in 75% of struck-by fatalities, the victims were hit by:

Heavy equipment OSHA estimates that 75 percent of struck-by fatalities involve heavy equipment like trucks or cranes.

Effective training of employees includes all of this information EXCEPT:

How to operate power tools in wet conditions Employers should train all employees to de-energize or drain electrical equipment before inspection or repair, keep all electrical equipment in good repair, follow lockout/tagout procedures, and never operate power tools in wet conditions.

What factor should be used to determine the amount of space to provide around stacked materials?

If the stack tips in any direction, enough space should be provided to allow workers to move quickly out of the way of falling materials.

Make sure that de-energized equipment or circuits are working.

Incorrect Equipment or circuits that are de-energized must be rendered inoperative and must have locks and tags attached at all points where the equipment or circuits could be energized.

Tag de-energized equipment and circuits only at the main point where they can be energized.

Incorrect Lock and tag de-energized equipment and circuits at all points where they can be energized.

Apply locks to the power source before de-energizing.

Incorrect When locking out and tagging out circuits, apply locks to the power source after de-energizing.

Hazards related to the construction of masonry walls can be reduced by taking all these OSHA-recommended measures EXCEPT:

Installing wire-mesh barriers at the tops of structures to catch falling debris Only essential workers should be allowed near masonry wall construction. To enforce this, set up a limited access zone around operations. Additionally, be sure to have concrete structures checked by qualified persons before placing loads and adequately shore or brace structures until they are permanently supported.

Flame-resistant clothing and Class E hardhat

Joe may encounter falling objects and high voltages when he's within the Flash Protection Boundary. Flame-resistant (FR) clothing and PPE must be used by anyone crossing any part of her or his body into the Flash Protection Boundary.

Lockout/tagout

Jose will be inspecting and repairing electrical equipment. Before any inspections or repairs are made, the switch or controls of the machine or other equipment being locked out of service must be tagged securely to show which equipment or circuits are being worked on.

Rubber insulating gloves and hoods

Lisa will have to work near wires with a potential live electrical charge. When it is necessary to handle or come close to wires with a potential live electrical charge, it is essential to use proper, insulating PPE. Use proper foot protection (not tennis shoes) and electrically rated rubber insulating gloves, hoods, sleeves, matting, and blankets.

Use metal ladders In order to minimize the risk of accidents around power lines, you should know which of the following steps are correct or incorrect.

No When working near power lines, remember to use wood or fiberglass ladders, not metal ladders.

You're driving and a power line falls on your truck. You slam on the brakes, get out, and run far away.

Not Safe If an overhead wire falls across your vehicle while you are driving, stay inside the vehicle. If the engine stalls, do not leave your vehicle. Call or ask someone to call the local electric utility company and emergency services.

You automatically assume that if a power line is down or seems to be insulated, then it's probably safe.

Not Safe Never assume that a wire is safe to touch even if it is down or appears to be insulated.

During cleanup activities, you always stay five feet away from overhead wires to avoid electrocution.

Not Safe Stay at least 10 feet (3 meters) away from overhead wires during cleanup and other activities. If working at heights or handling long objects, survey the area for the presence of overhead wires before starting work.

How do you get an electrical shock?

Parts of your body completing an electrical circuit An electrical shock occurs when electrical current passes through the body. You will get an electrical shock if parts of your body complete an electrical circuit.

Stacking Materials

Placement of overhead items

Fall Protection System

Placement/use of Guardrail

Never touch if downed

Power Lines Never touch a fallen overhead power line. Voltages of overhead lines range from 120 to 750,000 volts. Always assume they are live, and call the local electric utility company to report a downed line.

Stay at least ten feet away

Power Lines Power line hazards can be avoided if precautions are taken, such as staying at least ten feet away from the power lines. Overhead power lines usually are not insulated, or are covered only to protect against weather; some examples of equipment that can contact power lines are cranes, ladders, and scaffolds.

Use wood or fiberglass ladders instead of metal ladders

Power Lines Power line hazards can be avoided if precautions are taken, such as using only wood or fiberglass ladders, not metal ladders.

In which of the following situations can a flexible or extension cord be used?

To cross an open area Flexible wiring should not be used where inspection would be difficult or where damage would be likely. Flexible cords must not be run through holes in walls, ceilings, or floors, run through doorways, windows, or similar openings (unless physically protected), or hidden in walls, ceilings, floors, conduit, or other raceways.

What do tripped circuit breakers and blown fuses indicate?

Too much current in a circuit Tripped circuit breakers and blown fuses are clear indications of too much current in a circuit.

Among all of the safety measures that can and should be used to prevent electrical shock, which one is the most effective?

Training Training is the most effective safety measure in the prevention of electrical shock.

When overhead loads are being lowered into trenches, trench workers can be protected by _______.

Trench box Trench workers inside a trench box can be protected from overhead loads that are being lowered into trenches.

OSHA has approved sloping, shoring, and benching to be used as safety systems in which one of these jobs?

Trenching When working in trenches OSHA has approved sloping, shoring, and benching to be used as part of an effective safety system.

Carry a sander by the cord.

Unsafe

Put a finger on the power switch as you carry a plugged-in saw.

Unsafe

Yank the cord to unplug a nail gun from the electrical outlet.

Unsafe

Factors causing electrical accidents

Unsafe equipment, unsafe workplace, and unsafe work practices Electrical accidents are caused by a combination of these three factors: unsafe equipment and/or installation, workplaces made unsafe by the environment, and unsafe work practices.

When it completes a circuit through the body

Use metal ladders The use of metal ladders are not part of the guidelines to minimize the risk of power line accidents.

All of the following are essential points for the safe use of cords and wiring EXCEPT:

Use only two-wire type cords Two-wire type cords do not effectively protect in the event of a short circuit. Always use three wire cords equipped with a path to ground to prevent a severe electrical shock.

An arc flash can occur where differences of potential _____ exists.

Voltage Arc flash and the resulting release of energy can only occur if an arc between two differences of potential (voltage reading) exists between any two phase conductors, or any phase conductor and a grounded part (for grounded systems only).

Which of the following method you should not use for putting out an electrical fire?

Water Water should never be used to put out an electrical fire since this can cause an electrical shock.

When does electricity become hazardous to humans?

When it completes a circuit through the body When it completes a circuit through the body

When is wire size an electrical hazard?

When its gauge is too small for the current it will carry Electrical hazards can occur when a wire with a small gauge is used for larger currents, as this can cause over heating and fires.

Sloping

Working in a trench Sloping protects workers by cutting back the trench wall at an angle inclined away from the excavation. Trenches five feet or deeper must be protected using OSHA-approved systems. Trench collapses cause dozens of fatalities each year.

Shoring

Working in a trench Trenches five feet or deeper must be protected using OSHA-approved systems. Shoring protects workers by installing aluminum hydraulic or other types of supports to prevent soil movement. Trench collapses cause hundreds of injuries each year.

Assume that power lines are energized In order to minimize the risk of accidents around power lines, you should know which of the following steps are correct or incorrect.

Yes Assume that all overhead wires are energized at lethal voltages. Never assume that a wire is safe to touch even if it is down or appears to be insulated.

Stay at least 10 feet away from power lines In order to minimize the risk of accidents around power lines, you should know which of the following steps are correct or incorrect.

Yes Avoid power lines hazards by staying at least 10 feet away from the lines.

Use wood or fiberglass ladders. In order to minimize the risk of accidents around power lines, you should know which of the following steps are correct or incorrect.

Yes When working near power lines, remember to use wood or fiberglass ladders, not metal ladders.

Grounding is an important part of electrical safety. Which statements are correct?

You should inspect electrical systems to ensure that the path to ground is continuous, You should ground exposed metal parts of equipment, Don't remove ground prongs from tools or extension cords, Tools plugged into improperly grounded circuits may become energized. Grounding creates a low-resistance path from a tool to the earth to disperse unwanted current. Properly ground power-supply systems, electrical circuits, and electrical equipment.

Rita's employer uses an AEGCP at each construction site. It is April 26, and as Rita gathers her power tool flexible cords to begin the day, she notices the inspector's tape is white. By the tape's color, Rita knows the cord was inspected at the beginning of _____.

[July, January, October ?] When an assured equipment grounding conductor program is used to protect employees on construction sites, daily visual inspection for damage of equipment connected by cords and plugs before use must be conducted by a competent person. The color code divides the inspection system into subsequent quarters designated by white, green, red, and orange.