Transcript Electrical Powerpoint

Electrical Safety
1
Electrical Hazards & OSHA
•29 CFR 1910.303(b)(1) requires:
•“Electrical equipment shall be free from
recognized hazards that are likely to cause
death or serious physical harm to employees”
•Michigan has adapted the appropriate OSHA
regulations
2
Electrocution
•Each year, ~9% of fatalities in American
workforce is by electrocution while working
around electricity.
•Workplace electrocution hazards:
•Broken light bulb
•Frayed cords
•Exposed wires
•Water around electrical equipment
•Crowded outlets
3
Voltage
 Voltage: amount of electrical force (electromotive
force) to move electricity between 2 points
 This is difference of electron and proton potential.
 Measurement between 2 points can be between
“hot” and neutral, or between other charged items
 Voltage measured in volts
4
VOLTS
RMS
Hot
Neutral VOLTS
One Cycle
5
Resistance
 Resistance: measure of opposition of flow of
current (opposite of conduction)
 Measured in Ohms (Voltage/Current)
 Similar to friction
 Caused by nature of material or work done
 Example: A toaster wires get hot due to
resistance.
6
Safe Electrical Work Practices
•Checked for frayed cords
•Wear correct PPE
•Use correct tools
•Turn off unused machines
•Use non-conducting ladders
•No water around electrical equipment
•Grounding
7
Current
 Current: amount of electricity that flows in a
circuit
 Measured in amperes (Amps)
 Milliamp = 1/1000 of amp
8
Current
•There are 2 different types of current:
AC- Alternating current (outlets)
DC- Direct current (batteries)
9
Ventricular Fibrillation
Current between 70-200 milliamperes, if passed
through heart, can cause ventricular fibrillation.
V fib means heart loses meaningful
pumping action, thus causing death in a
short period of time.
This happens when a small current
passes either (a) from head to foot, or
(b) from hand to foot and thru the heart.
~100 milliamperes can cause VF
10
Grounding
 Ground: Process of achieving earth neutral
 Common (wired) return path for electrical
circuit to ground
11
GFCI
•Ground Fault Circuit Interrupter
Prevents electrocution by detecting a ground fault
and opening circuit (so our body doesn’t become
part of circuit)
A type of undercurrent
Use: kitchen, bathroom, basement, garage,
outside, laundry room
Activates at 5-61 mA and 1/25 of second
12
GCFI-Receptacle
13
Grounded Equipment
•Never use a plug with a missing ground
prong.
•Always check before plugging into a
receptacle.
14
Overcurrent
•Overcurrent - extra amount of current that
passes through a circuit
•Overcurrent protection device opens the
circuit (electricity won’t flow)
•These devices are circuit breakers or fuses.
15
Short Circuit
•A short circuit is when there is a direct
contact between “hot” and “neutral”.
16
Static Electricity
•Static electricity - buildup of difference of
potential (electric charge) between materials
•E- move from one object to another when
surfaces come into contact (friction)

•Can ignite vapors
Positive
Negative
17
Extension Cords
• Extension cords cannot be used:
 As a substitute for fixed wiring
 Running through holes
 Running through doorways, windows, etc.
 Behind walls, ceiling, or floors
Should contain warning labels & rating info (&
only be used temporarily)
18
Polarized Plugs
•One prong slightly wider so can only be
inserted one way
•Allows live and neutral connection
safety
19