©2008 1-1 Introduction to Electrical Safety Module 1.

transcript

Introduction to Electrical Safety

Module 1

Recognize key statistics relating to electrical injuries.

Module Objectives

Recognize OSHA regulations and other standards relating to electrical safety.Understand basic electrical terminology.

Understand key facts relating to electric shock.

Module Objectives

Identify the four types of injury relating to electrical incidents.

Understand the basic facts of electricity.

Module Objectives

Understand Ohm’s Law and describe how the terms current, voltage and resistance relate to Ohm’s Law.

Recognize the effects of electricity on the human body.

From 1992-2002, there were 3,378 deaths from on-the-job electrical injuries.

That’s 4.7% of all occupational deaths.

That’s almost one death per day!

Electricity is the 4th leading cause of injury-related occupational death

Electrifying Statistics

Contact with overhead power lines was the leading cause of electrocutions, causing 42% of the deaths.

The second leading cause of electrocutions was failure to properly de-energize equipment.

The third most common cause was contact with electrical components mistakenly thought to be de-energized.

Contact with buried, underground power lines caused 1% of the fatalities.

Non-fatal injuries were also high, with 46,598 from 1992 through 2002 .

36% were caused by contact with the electric current of a machine or tool.34% were caused by contact with wiring or transformers.2% were caused by contact with buried, underground power lines.

OSHA 29 CFR 1910, Subpart I

OSHA 29 CFR 1910.147

OSHA 29 CFR 1910, Subpart P

OSHA 29 CFR 1910, Subpart S

OSHA 29 CFR 1910.333

Safety related work practicesSafety related maintenance requirementsSafety requirements for special equipmentInstallation safety requirements

NFPA 70E

A supplement to the NFPA 70E standardGives step-by-step instructions for how to implement the standardProvides the thought process and rationale for the standard

NFPA 70E Handbook

OSHA is the SHALL

What they all Do

NFPA 70E standard is the HOW

NFPA 70E handbook is the STEP-BY-STEP

One who has received training in and has demonstrated skills and knowledge in the construction and operation of electric equipment and installations and the hazards involved.

Qualified Person

This program does not meet the requirements for a qualified person. It is intended to raise your awareness of electrical safety.

Important Note

Arc Flash

Electric Shock

Types of Electrical Injury

BurnsFalls

Electrocution

Electric current won’t flow until there is a complete loop.

Electric current always tries to return to its source.

When current flows, work can be accomplished.

Rules of Electrical Action

The body comes into contact with wires in an energized circuit.

The body comes into contact with one wire of an energized circuit and a path to the ground.

The body comes into contact with a “hot” metallic part that is touching an energized conductor.

How Shock Occurs

The path of the current through the body.

The amount of current flowing through the body.

The length of time the body is in the circuit.

Severity of Shock

Three factors

ELECTRICITY

ELECTRONS IN MOTION

Basic Facts of Electricity

Flow of Electricity Flow of Water

CURRENT

Flow of electrons

Measured in amps

I = amps

Flow of liquid

Measured in gallons per minute (gpm)

Measured in voltage

V or E = volts

Measured in pounds per square inch (psi)

RESISTANCE

Electrical resistance to flow is measured in ohms

R = resistance

Water resistance to flow is measured as friction or baffles

Ohm’s Law

A mathematical formula that enables the measurement of electric current moving through a conductive body

George Simon Ohm1789-1854

German Physicist

Volts (V) = Amps (I) X Resistance (R)V = IR

1 volt = 1 amp X 1 ohm of resistance

A Visual Way to Remember

Solution

1. Since we know voltage (V) and resistance (R), which version of the formula should we use?

I = V/R

Solution

2. Now which numbers do we plug in?

I = 120/1,000

3. How many amps?

I = .12 amps

4. How many milliamps (mA)?

I = 120 milliamps

The Human Body Resistance Model

Body Part Resistance

Dry, intact skin

Wet skin

Within the body

Ear to ear

100,000-600,000 ohms

1,000 ohms

400 ohms

100 ohms

Strength of current.Duration of contact.Body mass.Gender of person.Moisture on the body.Path of the current.

Effects of Electricity Depend On:

Photo courtesy of Schneider Electric

What the Project Manager Felt

1. The drill had 120 volts.

2. The project manager’s dry skin had a resistance of 100,000 ohms.

3. The flow into the project manager’s hand was 120 volts/100,000 ohms, 0.0012 amps, or 1.2 milliamps.

What the Apprentice Felt

1. The drill had 120 volts.

2. The apprentice’s wet skin had a resistance of 1,000 ohms.

3. The flow into the apprentice’s hand was 120 volts/1,000 ohms, 0.12 amps, or 120 milliamps.

Facts About Lower Amperage

A small circuit in your home carries 12-16 amps of current.That equals 12,000 to 16,000 milliamps.As we’ve learned, as little as 120 milliamps can cause death.Low amperage/voltage circuits are dangerous!

NIOSH Low Voltage Study

110-120 v

220-240 v

270-277 v

440-480 v

That’s over 1 in 3 deaths at 120 v or less!

Action Potential Barriers Overcoming the Barriers

Action Plan

©2008 1-1 Introduction to Electrical Safety Module 1.

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