Electrical

Question 1

What is injury/death rate for electrical hazards?

Answer 1

*while a fraction of total workplace injuries, likely to result in death
*Electrical hazards cause approximately 4000 injuries per year
*Average of 13 days away from work and nearly one fatality every day
*Over 400 electrocutions in the US a year

Question 2

What are the main causes of electrocution?

Answer 2

*20% wiring
*9% ladders contacting power lines
*9% power tools
*7% landscaping, gardening, and farming equipment

Question 3

How does electricty work? (see notes for picture)

Answer 3

a complete circuit is maintained between the tool and the energy source

• if the tool is damaged, the person may come in contact with electricity and can become a path for the current
  *The person will be shocked

Question 4

What is the first electrical hazard?

Answer 4

electrical shock

• when the human body becomes a conductor, completing the path for the current to flow
• Like water, electricity will take the path of least resistance. Current will most likely flow through a circuit instead of a human body, unless the body presents a path of lower resistance.

Question 5

What are the major causes of eletrical shock?

Answer 5

• exposed electrical parts
• not properly grounded equipment
• Wet or damp surfaces
• Damaged insulation
• Overloaded circuit
• Overhead power lines

Question 6

What are the rules for exposed electrical parts?

Answer 6

• outer insulation on electrical cord must be intact
• Never use an electrical panel that has exposed wires
• All openings must be closed

Question 7

What is improper grounding?

Answer 7

• the ground pin safely returns leakage current to ground
• Never remove the ground pin

Question 8

How do wet conditions effect electrical components?

Answer 8

• water increases the risk of electrical shock
• Always avoid using tools in wet locations

Question 9

How does damaged insulation effect electrical equipment?

Answer 9

• defective, or inadequate insulation is a hazard
• Never use tools or extension cords with damaged insulation
• Insulation prevents conductors from contacting each other or you
• Never hang extension cords from nails or sharp objects

Question 10

What are ground faults?

Answer 10

• occurs when current flowing to the load (drill, saw, etc) does not return by the prescribed route
• Current travels through the black (ungrounded) wired to the load and returns to the source through the white (grounded) wire
• a persons body can act as the path to ground when a fault occurs

Question 11

How do you avoid grounding hazards? (2 steps)

Answer 11

1. Electrical circuit or system grounding
   * ground all power supply systems, electrical, circuits, and electrical equipment
   * do not remove ground pins/prongs from cord
   * use double insulated tools
2. Electrical equipment grounding
   * all metal frames and enclosures of equipment are grounded by a permanent connection or bond
   * The equipment, grounding conductor provides a path for dangerous fault current to return to the system, ground at the supplies or should occur

Question 12

What are ground fault circuit interrupters (GFCI’s)

Answer 12

• to send an imbalance and current flow
• at the current flow differs by over 5MA +/- 1MA, the GFCI will quickly open the circuit
• it is not an overcurrent device like a fuse or circuit breaker

Question 13

What is the second electrical hazard?

Answer 13

Arc flash/arc blast

a phenomenon where a flashover of electric current leaves its intended path and travels through the air from one conductor to another, or to the ground

Question 14

What is arc flash/blast caused by?

Answer 14

dust, dropping tools, accidental touching, condensation, material failure, corrosion, faulty installation

Question 15

What are results of arc flash?

Answer 15

burns, fire, flying objects

Question 16

What is the 3rd electrical hazard?

Answer 16

Burns

result when a person touches electrical wiring or equipment that is energized

Question 17

What are thermal contact burns?

Answer 17

skin comes in contact with overheated, electrical equipment, or when clothing is ignited in an electrical incident

Question 18

What are electrical burns?

Answer 18

• causes tissue damage
• Result of heat generated by the flow of electric through the body. Is one of the most serious body injuries you can receive
• High temperature is near the body, produced by an electrical arc or explosion. cause arc flash burns.

Question 19

What are injuries that can occur from electrical hazards?

Answer 19

Internal
* we small amounts of current and extra current leads to serious damage
* Internal bleeding, tissue destruction, and nerve or muscle damage
* May not be immediately apparent to the victim/observers; however, if left
untreated, they can result in death

Involuntary muscle contraction
* muscle violently contracts when stimulated by excessive electricity

Question 20

What are the 4th and 5th hazards that can occur from explosions and fires?

Answer 20

Explosions
* explosions occur when electricity provide a source of ignition for an
explosive mixture in the atmosphere

Fires
* electricity is one of the most common causes of fires both both in the
home and in the workplace. Defective or misuse electrical equipment is a
major cause.

Question 21

How is low-voltage still hazardous?

Answer 21

• the degree of injury increases with the length of time the body is in the circuit
• Even relatively low voltages can be extremely dangerous
• an exposure of 100 mA for three seconds, can cause the same amount of
  damage as an exposure of 900 mA for .03 seconds

Question 22

How does water and conduction work?

Answer 22

• Water influences the conductive properties of some materials
• use extreme caution when working with electricity, where there is water in the environment or on the skin
• Example: Dry wood is a poor conductor and Wood saturated with water becomes a ready conductor. Dry conditions means human skin is resistant

Question 23

How is two control stage applied to electrical hazards?

Answer 23

• Two stage control (stage one cannot be used)
• Identify the purpose of various engineering controls designed for electrical safety
• The preferred method to control electrical hazards is to engineer controls
  into the design of equipment
• Engineered safeguards can be as simple as a light switch cover or a door on the breaker panel

Question 24

What are adminstrative control examples when it comes to electrical hazards?

Answer 24

• warning signs, labels, tags
• Procedures
• Work planning/control documents
• Work related training, and certifications
• Lockout/tag out

Question 25

When are internal barriers required?

Answer 25

• ground fault circuit interrupters are required under the following conditions
• damp or wet location
  • within 6 feet of exterior door
  • Outdoors
  • Rooftops

Question 26

What is the control of hazardous energy?

Answer 26

• referred to as the lock-out/tag-out
• The purpose of this regulation is to protect people from hazardous energy while performing service/maintenance on machines, tools, and equipment
• Safeguards against unexpected start up of equipment or process

Question 27

What are sources of energy?

Answer 27

-Electrical
-Water
-steam
-Pneumatic
-natural gas
-hydraulic
-mechanical

Question 28

What are the basic steps for a lock-out/tag out?

Answer 28

Step one: detailed procedures for equipment Step two: notify affected employees
Step three: shut down equipment properly
Step four: disconnect all primary energy sources Step five: address all secondary sources
Step six: verify the lockout
Step seven: keep it in force during shift changes
Step eight: bring the equipment back online

Question 29

What are some points to remember about electrical hazards?

Answer 29

• if you see a lock on equipment, do not attempt to operate
• to gain access to a locked and tagged out circuit contact the person named on the tag
• do not remove the tag or restore without an approval
• electrical locking devices may be installed on a cord, switch, breaker or disconnect device: look before you operate the equipment
• qualified person – NFPA 70E