electrical safety training

2.  29 CFR 1926.400; Subpart K
National Electric Code (NEC)

3.  Electricity is the second leading
cause of death in construction.
 Electrocutions make up 12% of
construction fatalities annually.
Over 30,000 non-fatal shocks occur
each year.
Over 600 deaths occur annually due
to electrocution.
Source: Bureau of Labor Statistics

4. Leading Causes of Electrical Accidents:
 Drilling and cutting through cables
 Using defective tools, cables and equipment
 Failure to maintain clearance distance of 10 feet
 Failure to de-energize circuits and follow
Lockout/Tagout procedures
 Failure to guard live parts from accidental
worker contact

5. Leading Causes of Electrical Accidents:
 Unqualified employees working with electricity
 Improper installation/use of temporary electrical
systems and equipment
 By-passing electrical protective devices
 Not using GFCI (ground fault circuit interrupters)
devices
 Missing ground prongs on extension cords

6.  Shock – Most common and can cause electrocution or
muscle contraction leading to secondary injury which
includes falls
 Fires – Enough heat or sparks can ignite combustible
materials
 Explosions – Electrical spark can ignite vapors in the air
 Arc Flash - can cause burns ranging from 14,000 degrees f. to
35,000 degrees f
 Arc Blast – In a short circuit event copper can expand 67,000
times. The expansion causes a pressure wave. Air also
expands adding to the pressure wave

7. Resistance = Diameter of Hose
Example – Larger hose (less resistance),
more water flows
Current = Flow Rate
Example – 15 gallons per minute
Voltage = Water Pressure
Example – 45 PSI

8.  Electrical current is the flow of electrons
through a conductor.
 A conductor is a material that allows
electrons to flow through it.
 An insulator resists the flow of electrons.
 Resistance opposes electron flow.

9.  Circuits are AC
(alternating current) or DC
(direct current).
 Current is usually AC.
 AC current has five parts:
(1) Electrical source
(2) HOT wire to the tool.
(3) The tool itself
(4) NEUTRAL wire
returns electricity
from the tool
(5) GROUND

10. Current travels in closed circuits through
conductors (water, metal, the human body).
 Shock occurs when the body becomes a part
of the circuit.
Current enters at one point & leaves at
another.

11.  Contact with both
conductors
 Contact with one
conductor and ground
 With a tool: contact
with “hot” metal part
and ground (1), (2) &
(3)

12.  Severity of the Shock depends on:
 Amount of current
 Determined by voltage and resistance to flow
 Path through the body
 Duration of flow through the body
 Other factors such as general health and
individual differences.

13. Luling, La. - A man was electrocuted when his sweat
dripped into the electric drill he was using to build a
swing set in his backyard, the coroner said.
Richard Miller was pronounced dead Sunday at
St. Charles Hospital, said David Vial, St. Charles Parish
coroner. Miller, 54, had been using an electric drill in
90 degree heat, Vial said Monday.
“Apparently the man was sweating profusely,” Vial
said. “He probably was pushing against the drill with
his chest and his perspiration went into the drill itself
and made a contact.”
The Associated Press

14. AC current
(mA)
Effect on human body
1 Slight tingling sensation
2-9 Small shock
10-24 Muscles contract causing you to freeze
25-74 Respiratory muscles can become
paralysed; pain; exit burns often visible
75-300 Usually fatal; ventricular fibrillation;
entry & exit wounds visible
>300 Death almost certain; if survive will have
badly burnt organs and probably require
amputations

15. Using a 120 volt circuit and resistance for
wet & dry skin:
E=IR: Voltage=Current x Resistance
(Volts) (Amps) (Ohms)
So: I=E/R
Dry Skin =120/100,000=.0012 amps
=1.2ma flowing through
body to ground
Wet skin =120/1000=.120 amps
=120ma flowing through
body to ground
Remember: 1 Amp = 1000 milliamps

16. Effects of Current Flow

17. If you come across a person receiving an electric shock:
 if possible, disconnect the electrical supply (switch?)
 assess the situation – never put yourself at risk
 take precautions to protect yourself and anyone else in the vicinity
 apply the first aid principles (e.g. DRSABCD)
 assess the injuries and move the casualty to a safe area if required
 administer first aid if trained
 seek urgent medical attention

18. You could be the victim if you:
 don’t follow proper procedures around electricity
 use electrical equipment improperly
 use faulty electrical equipment

19.  Electricity is invisible – this in itself makes it dangerous
 It has great potential to seriously injure or kill
 Everyone is exposed to electrical hazards, not just electricians

20.  Employers must follow the OSHA Electrical
Standards (Subpart K)
 Electrical installation
 Subpart K includes four proactive methods:
 Electrical Isolation
 Equipment Grounding
 Circuit Interruption
 Safe Work Practices

21. We can be safe by keeping electricity away
from us. We can:
 Insulate the conductors.
 Example: The insulation on extension cords.
 Elevate the conductors.
 Example: Overhead powerlines.
 Guard the conductors by enclosing them.
 Example: Receptacle covers, boxes, & conduit.

22.  The first way to safeguard workers from electrically
energized wires is through insulation.
 Rubber and plastic is put on wires to prevent
shock, fires, short circuits and for strain relief.
 It is always necessary to check the insulation on
equipment and cords before plugging them in.
 Remember, even the smallest defect will allow
leakage!

23. Defective Extension Cords

24.  Worker attempted to climb
scaffold with electric drill.
 Drill’s cord was damaged
with bare wires showing.
 The bare wire contacted
the scaffolding.
 The worker died!

25.  Remember, never allow yourself, your tools,
or the materials you are working with to be
within 10 feet of energized lines!

26.  Clearance of worker and any equipment, tools,
materials, or scaffold near uninsulated lines is 10
feet!

27. A worker was
attempting to move
mobile scaffold.
 Scaffold made contact
with 7200 volt line.
 The worker died.

28.  The third way to safeguard workers from
electrically energized wires is by
guarding them.
 Covers, boxes, and enclosures are often
put around conductors to prevent
worker contact.
 It is always necessary to check that
electrical boxes and panels are covered
and free from missing “knock-outs”.
 Remember, electric equipment operating
at 50 volts or more must be guarded!

29. Guarding the Conductors

30. Guarding the Conductors

31.  We can be safe by providing a
separate, low resistance pathway for
electricity when it does not follow
normal flow (ground prong).
 Grounding gives the stray current
somewhere to go and keeps you from
becoming part of the circuit.

32.  Grounding will not work if the electricity
can flow through you more easily than the
ground. This can happen when:
 Your tool doesn’t have a ground pin.
 You’re working in wet locations.
 You’re touching a metal object.

33.  All circuits and extension
cords.
 All noncurrent carrying
metal parts.
 Portable & semi-portable
tools and equipment
unless double insulated.

34. Do Not Eliminate the Ground!
You become the next-best path for current!

35. Do Not Reverse Polarity
The prongs are different
sized so you can’t turn
the plug around. If you
do, the electrical fields
within the motor are always
energized. If there is
moisture present, the case
is likely to be “hot”. Even
with double-insulated tools,
you still could get a shock.

36.  We can be safer by automatically shutting
off the flow of electricity in the event of
leakage, overload, or short circuit.
 Ground Fault Circuit Interrupters (GFCI)
are circuit protection (or “overcurrent”)
devices that protect you, the worker.
 Circuit breakers & fuses protect equipment,
not you, because they take too much
current & too much time to trip.

37.  Circuit Breakers and Fuses
 Only protect the building,
equipment, and tools from heat
build-up!
 Never depend on circuit breakers
or fuses to prevent shocks!
 Ground Fault Circuit Interrupter
(GFCI)
 Is the only device which will
protect the worker from shock and
electrocution!

38. The GFCI detects
‘leakage’ of 4-6
milliamps & opens
the circuit in 1/40th
of a second.
It will work without
the ground plug
but not fast
enough if you are
the ground .

40. Permanent Equipment in Temporary Use
What is wrong with using this as a ‘splitter’?

41.  Must be in good shape without splices.
 Cannot be secured with staples, nails or
bare wire.
 Must be protected from damage.
 Must have a ground pin.
 Should be inspected regularly and pulled
from service if defective.
 Cannot be repaired with electrical or duct
tape. Must repair with heat-shrink sleeve
or bonding/vulcanizing tape to retain
original insulation properties.

42. Extension Cords-What’s the Difference?

43. Clever Or Foolish?

44. No metal ladders for or near
electrical work.
No wet hands when plugging or
unplugging cords/equipment.
No raising or lowering tools by
the cord.
Unless equipment is designed for
it, cannot be used in damp and
wet locations.
Photo depicts hazardous condition

45.  Inadequate wiring
 Exposed electrical parts
 Wires with bad insulation
Overloaded circuits
Damaged power tools and equipment
Using the wrong PPE and tools
Overhead power lines
Damaged extension cords