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1 - Electrical Safety
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Basics of Electricity:
- Electrical current will not flow unless it has a complete path (circuit) that returns to its source (battery, transformer).
- Current flows through you and other conductors, such as metals, earth and concrete.
- Current can harm you when it flows through your body (electric shock).
- Insulators resist the flow of electricity. Insulating materials are used to coat copper conducting wires and are used to make electrical work gloves. Insulators help to protect humans from coming into contact with electricity flowing through conductors.
- Just as there is pressure in a water pipe, even with no water flowing, there is voltage at a receptacle, even if current is not flowing. Another word for voltage is "Potential.";
How Electricity Can Harm You
Current passing through your body can cause electric shock, resulting in 3 types of potential injuries:
- Burns (arcs burn with heat & radiation)
Physical injuries (broken bones, falls, & muscle damage)
At 10 mA, the muscles clamp on to whatever the person is holding.
Nervous system effects (stop breathing at 30 to 75 mA alternating current at 60Hz, fibrillation at 75 to 100 mA at 60Hz)
- Fibrillation = heart is "twitching"; and there is no blood flow to the body.
- The heart can be damaged because it is in the path of the most common routes electricity will take through the body:
- Hand-to-hand
- Hand-to-foot
| Know about static electricity and how it can do harm. |
Control hazards though safe work practices: Minimize your exposure to static shocks. Never clean the glass face of your computer monitor while the computer is on.
During normal operation, the glass surface of a monitor's CRT accumulates an electrostatic charge. When you touch the screen with a finger, the charge is from the portion of the screen you touched and it discharges through your finger with a tiny spark. Electric current does not normally flow through glass, so only the part of the screen that your finger touches is discharged.
However, when you clean a monitor the entire glass is wet and the charge on the entire screen will discharge to your finger or hand, causing a much more painful shock.
You can be injured by the reaction to the shock even though such shocks in themselves are not hazardous.
| Use OSHA Safe Work practices. |
Control hazards though safe work practices:
- Plan your work and plan for safety
- Avoid wet working conditions and other dangers
- Use Ground Fault Circuit Interrupters. GFCI's are electrical devices that are designed to detect ground faults (when current is "leaking" somewhere outside its intended pathway). If your body provides the path to ground for the leaking current, you could receive a shock or be electrocuted. GFCI's should be used in all wet locations and on outside outlets.
- Avoid overhead power lines: Position yourself so that the longest conductive object you are using (saws, poles, tools, brooms, etc.) cannot come closer than at least 10 feet to any unguarded, energized overhead line.
- Use proper wiring and connectors
- Use extension cords properly and temporarily:
- Cords must be UL listed and have 3 prongs
- Power bars must have a fuse or breaker
- Do not use 2-prong, ungrounded cords in a lab
- Do not run cords through walls, doors, under rugs, or across aisles
- Do not repair cords--buy new ones
- Make sure the total number of watts connected to the cord does not exceed the rating of the cord.
- Use and maintain tools properly
- Avoid wearing items such as jewelry, watch bands, bracelets, rings, key chains, necklaces, etc. that might come into contact with exposed, energized parts.
- Wear correct PPE:
- Hard hats rated "Class E"
- ANSI-approved footwear coded "EH"
| Follow the Administrative Controls. |
- Safe work procedures
- Lockout and Tagout
- Proscribed work practices
- Signs warning of electrical hazards
Use Safe Equipment |
- Do not use equipment that has been damaged or improperly modified.
- Always use equipment according to the manufacturer's specifications.
- "Live" parts (greater than 50 volts) must be guarded by one or more of the following:
- An enclosure that requires a tool for access.
- A locked enclosure.
- An interlocked access door.
- A substantial insulating guard to prevent contact.
- Check cords--they should:
- Be completely free of damage and deterioration.
- Should always have an appropriate strain relief device where they enter the enclosure.
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