HSE-LS-13_Electrical_Safety.pdf

8/9/2019 HSE-LS-13_Electrical_Safety.pdf

1/30

2/23/20

The Petroleum Institute

30-hr Lab Safety Training

HSE/LS-13: Electrical Safety

Attendees will be able to:

1. Define common electrical terminologies

2. Discuss the dangers of electricity

3. Explain the concepts of arcing, ampacity, bonding and grounding

4. List the types & functions of protective devices

5. Recognize safety features/requirements of commonly used

electrical equipment

6. Use/apply basic safety practices when working with electricity

7. Outline the different wiring methods

8. Identify hazardous location classification for installation/use of

electrical equipment

Learning Objective

Major Components29 CFR 1910.300 -

Become familiar with OSHA Subpart S (www.osha.gov) &applies to installations designed or installed after March 1972

Examination of Equipment

Working Clearances

Overcurrent Protection

Grounding

Wiring Methods

Electrical Boxes

Flex Cord & Cable

Hazardous Locations

Safe Work Practices
http://www.osha.gov/http://www.osha.gov/http://www.pi.ac.ae/index.php


2/30

2/23/20

Most Frequently Cited

Conductors entering cabinets, boxes, fittings protectedfrom abrasion

Live parts

Grounding path

Electrical box covers

Flexible cords & cablesStrain relief

Electrical Issues

An average of one worker is electrocuted onthe job every day

There are four main types of electrical injuries:

Electrocution (death - electrical shock)

Electrical shock

Burns

Falls

Electrical Terminology

Current(C)the movement of electrical charge(amps)

Resistance (R)opposition to current flow (ohms)

Voltage(V)a measure of electrical force (volts)

V = IR


3/30

2/23/20


Conductorssubstances, such as metals,

that have littleresistance to electricity

Insulatorssubstances, such as wood,rubber, and glass, that have highresistance to

electricity


Grounding -A highly conductive path to ground intended toprevent electrical shock

Bondingis the joining of metallic parts to form an electricallyconductive path

Arcing - Current flows through air between conductors that arenot in contact. Arcing is a function of distance, voltage andconductivity medium

Ampacityamount of current a conductor can safely conduct

10 gauge

30 amps; 12 gauge

20 amps; 14 gauge

15 amps

Electrical Shock

Electric shock occurs when the body

becomes a part of the circuit

Electric shock occurs when an individual

is in contact with the ground and

contacts:

1. Both wires of an electric circuit, or

2. One wire of an energized circuit and

the ground, or

3. A metallic part that has become

energized by contact with an

energized conductor


4/30

2/23/20

Electrical Shock (cont)

Current will flow between two wires of if there is a potentialdifference (voltage)

The hot or live wires are at 220-240 volts relative toground (red, brown, orange etc.)

The neutral wires are at zero volts to ground

(black, blue, white, etc.)

Ground (earth) wire is usually yellow and green, or it justcould be green.

If you are in contact with an energized live wire ANDwith the neutral or ground wire, you will incur ashock

If your body is grounded, (bare, wet, or not properlyisolated) feet for example, and you touch the livewire, you can get a bad electric shock.

With more voltage, skin conductivity increases.

Electrical Shock (cont)

Source: Accident Prevention manual for business and industry, 2001 Hagan, Montgomery & OReilly

Human Resistance to Electric Current


5/30

2/23/20

Effects of Electrical Contact


Electric Shock Severity

Severity of the shock depends on:

Path of current through the body

Amount of current flowing through the body

Length of time the body is in the circuit

LOW VOLTAGE DOES NOT MEAN LOWHAZARD

Dangers of Electricity

Currents > 75 mA* can causeventricular fibrillation

Death in a few minutes unless adefibrillator is used

75 mA is not much currenta smallpower drill uses 30 times as much

Low voltages can be extremelydangerous because, all other factorsbeing equal, the degree of injuryincreases the longer the body is incontact with the circuit.

* mA = milliampere = 1/1,000 of an ampere


6/30

2/23/20


Possibility of Success Vs Elapsed Time

Electrical Dangers (cont)

Dry skin has a fairly high resistance, but when moist,

resistance drops radically, making it a ready conductor.

Pure water is a poor conductor, but small amounts of

impurities, such as salt and acid (both are contained in

perspiration), make it a ready conductor.

A small current that passes through the trunk of the body(heart and lungs) is capable of causing severe injury or

electrocution.

Electrical Injuries

Burns

Common type of electrical

injury Typically occurs on the hands

Serious injury that needsimmediate attention

Indirect or secondary injuries

Falls due to shock fromelevated locations can result ininjury or death


7/30

2/23/20

Unsafe Action

Metal Ladder

Ladder not meant for 2 workers

Identification of Conductors

The grounded conductoris an energized circuit that isconnected to earth through the system ground. It is

commonly referred to as the earth.

The grounding conductoris not energized under normalconditions. It is energized only if there is a leak or fault

in the normal current path and directs current back to

the source.

The live (hot) wire should have a hot color (R,B,Y)

The neutral wire should have a cold color (B)

The equipment grounding conductor be G, or Gwith Ystripes

Identification of Conductors


8/30

2/23/20

Grounding Requirements

Service or system groundis the grounding of the neutralconductor or grounded conductor. In an ordinary low-voltage circuit, the white (or gray) wire is grounded at thegenerator or transformer and again at the service entranceof the building. This type of ground is primarily designed toprotect machines, tools, and insulation against damage.

Equipment groundmust be furnished by providing anotherpath from the tool or machine through which the current

can flow to the ground. This additional ground safeguardsthe electric equipment operator if a malfunction causes themetal frame of the tool to become energized.


9/30

2/23/20

Sample Electrical Citations

The path to ground from circuits,equipment, and enclosures must

be permanent and continuousEX: Ground prong missing

Hand-held electric tools must:

Have a three-wire cord withground and be plugged into agrounded receptacle, OR

Be double insulated


10/30

2/23/20

Grounding Hazards

Most frequently violated standards

Metal parts of an electrical wiring system (switch

plates, ceiling light fixtures, conduit, etc.) should be atzero volts relative to ground

Housings of motors, appliances or tools that areplugged into improperly grounded circuits maybecome energized

Shocks will result if contact is made

Double Insulated Tools

Tools and appliances protected that are doubleinsulated, need not be grounded

They must be distinctively marked

Work with Ground Fault Circuit Interrupters (GFCI)

Casing must be labeled

Tool must be inspected

Extension cord must be three-prong


11/30

2/23/20

Hazards of Portable Electric Tools

Currents as small as 10 mA can paralyze, or freeze

muscles

Person cannot release tool Tool is held even more tightly, resulting in longer

exposure to shocking current

Power drills use 30 times as much current as what

will kill.

Polarity of Connections

No grounded conductor may be attached to anyterminal or lead so as to reverse designated polarity

Reversed polarity is a condition when a neutralconductor is incorrectly connected to the hot

terminal of a plug, receptacle or other connector.

Protective Devices

These devices shut off electricity flow in the event ofan overload or ground-fault in the circuit

Fuses and Circuit breakers are over-current devices. If

there is excessive current:

Fuses melt

Circuit breakers trip open

Ground-fault circuit-interrupters (GFCIs) are leak

detectors


12/30

2/23/20

Overcurrent Protection

600 volts or less

Conductors and equipment must be protected fromovercurrent

Overcurrent devices must be readily accessible

Must not be located where they will be exposed tophysical damage or in the vicinity of easily ignitablematerial

Fuses and Circuit Breakers

If the circuit breakers or fuses are too big (high currentrating) an overload in the circuit will not be detected andthe current will not be shut off. This is a hazard.

A fuse gets destroyed before another part of the system

In a circuit breaker, a set of contacts opens the circuit

A circuit breaker can be re-used by re-closing the contacts

Fuses and circuit breakers protect equipment and facilities

Earth Leakage Circuit Breaker

The ELCB detects a difference in currentleakage (ground fault), between the hot

and neutral circuit wires

If a leak is detected (as little as 5 ma), theELCB can shut off electricity flow in as littleas 1/40 of a second, protecting you from adangerous shock

ELCBs are different from circuit breakersand fuses because they detect leakagecurrents rather than overloads

Note: Only an ELCBs(also called a Ground-fault circuit-interrupter ) protects individuals


13/30

2/23/20

Residual Current Circuit Breaker (RCCB)

The RCCB detects a difference in currentbetween the hot (live wire) and the neutralwire.

Its safer than ELCB because it can detectelectricity leakages through earth, otherequipment, etc.

RCCB can replace Earth Leakage CircuitBreaker (ELCB), and Molded case circuitbreakers (MCCB)

Equipment for General Use

A receptacle installed in a wet or damp location must

be suitable for the location.


14/30

2/23/20

Safety Violations

Electrical Hazards

A hazard exists when a conductor is too small tosafely carry the current

Example: Using a tool with an extension cord thathas a wire too small for the tool

The tool draws more current than the cord can handle,causing overheating and a possible fire without tripping thecircuit breaker

The circuit breaker could be the right size for the circuit butnot for the smaller-wire extension cord


15/30

2/23/20

Electrical Hazards (cont..)

Too many devices plugged into a circuit, willheat the wires to a very high temperature,

which can cause a fire

If the wire insulation melts, arcing may occur

and cause a fire

Unsafe Conditions


16/30

2/23/20

Regulatory (OSHA) Compliance

Guarding of live parts of electric equipment at 50volts or more:

Approved cabinets/enclosures1910.303(g)(2)(i),

OR

Permanent partitions making them accessibleonly to qualified persons,1910.303(g)(2)(i)(C)

OR

Elevation of 8 ft. or more above the floor orworking surface 1910.303(g)(2)(i)(D)

Mark entrances to guarded locations withconspicuous warning signs1910.303(g)(2)(iii)

Examination of Equipment

Safety of equipment must be determined using the

following considerations:

Suitability for installation and use

Mechanical strength and durability

Electrical insulation

Heating effects

Arcing effects Classification


Leakage Test


17/30

2/23/20


Continuity Test

Marking

Electrical equipment must be marked with themanufacturers name, trademark or otheridentification

Other markings must be provided giving voltage,current, wattage, or other ratings as necessary

Markings must be durable enough to withstandthe environment

Signage on high voltage equipment


18/30

2/23/20

Signage to high voltage electrical room

Identification

Each disconnecting means must

be legibly marked to indicate its

purpose, unless located and

arranged so that its purpose is

evident

Markings must be durable enough

to withstand the environment

Improperly labeled panel


19/30

2/23/20

Proper Example!

Panel Labeling

Panel Labeling


20/30

2/23/20

600 volts, nominal, or less -Working clearances

This section refers to a person qualified to work onelectrical equipment, usually an electrician

Working space in front of live parts (operating at 600volts or less) must be at least 3 feet

The workspace in front of electrical equipment mustnot be less than 30 inches wide

Working spaces may not be used for storage

Safety Violations


21/30

2/23/20

Proper Clearances!

600 Volts or less

Guarding of live parts

Any person who is in the vicinity of electrical equipment

must be protected against accidental contact

Location must be accessible only to qualified persons

Permanent, substantial partitions or screens

600 Volts or less

Guard against accidental contact by:

Location on a suitable elevated balcony or platform

Elevation of 8 feet or more above the floor or other

working surface


22/30

2/23/20

Unguarded Live Parts

Unguarded live parts above the working space must

be maintained at elevations not less than specified in

Table S-3 (1910.303)

http://www.osha.gov/SLTC/electrical/index.html

The minimum is 8 feet

Conductors entering boxes, cabinets, or fittings.

Conductors entering boxes, cabinets, or fittings must

be protected from abrasion.

Unused openings in cabinets, boxes, and fittings must

be effectively closed.

Electrical Box Covers

All pull boxes, junction boxes, and fittings must beprovided with approved covers

Metal covers must be grounded

Outlet boxes must have a cover or a faceplate

Outlet box covers with holes for flexible cords musthave bushings or smooth, well- rounded surfaces
http://www.osha.gov/SLTC/electrical/index.htmlhttp://www.osha.gov/SLTC/electrical/index.html


23/30

2/23/20

Wiring Methods

No wiring system of any type may be in ducts usedto transport dust, flammable vapors, or ventilation

of commercial-type cooking equipment.


24/30

2/23/20

Temporary Wiring

Temporary electrical power and lighting wiring may be

of a class less than would be required for a permanent

installation.

Temporary Wiring

Uses permitted, 600 volts or less

During and for remodeling, maintenance repair, demolitionor similar activities

For experimental or developmental work

For a period not to exceed 90 days for decorative lighting,carnivals, and similar purposes

Only during tests, experiments and emergencies

Luminary Protection

Lamps for general illumination must be protected from

accidental contact or breakage.

Protection can be provided by an elevation of 7 feet or

by a suitable fixture with a guard.


25/30

2/23/20

Flexible Cords and Cables 1910.305(g)

More vulnerable than fixed wiring

Do not use if one of the recognized wiring methods can be usedinstead

Flexible cords can be damaged by:

Aging

Door or window edges

Staples or fastenings

Abrasion from adjacent materials

Activities in the area

Improper use of flexible cords can cause shocks, burns or fire

Flexible Cords

Flexible cords and cables must be protected from

accidental damage. Sharp corners or projections must

be avoided.

Protection must be provided when passing through

doorways or other pinch points.

Permissible Uses of Flexible Cords - Examples

1910.305(g)(1)(i)

Pendant, or

Fixture Wiring

Pendant, or

Fixture Wiring

Portable lamps,

tools or appliances

Stationary equipment to

facilitate interchange


26/30

2/23/20

As a substitute for the fixed wiring of a structure

Where run through holes in walls, ceilings or floors

Prohibited Uses of Flexible Cords

Prohibited Uses of Flexible Cords Examples

1910.305(g)(1)(iii)

Substitute forfixed wiring

Run through walls,ceilings, floors, doors, or

windows

Concealed behind or

attached to building

surfaces

Flexible cords must be used only in continuous

lengths without splice (< No 12) or tap

Damaged cords must be properly repaired or

removed from service

Flexible Cords


27/30

2/23/20

Flexible cords must be connected to devices so that

strain relief is provided to prevent pull off frombeing directly transmitted to joints or terminal

screws

Flexible Cords Strain Relief

Flexible Cords Strain Relief

Hard service flex cords, No. 12 or larger, may be

repaired if spliced so that the splice retains the

insulation, outer sheath properties, and usage

characteristics of the original cord

Flexible Cords Splicing


28/30

2/23/20

Splices

Conductors must be spliced with:

Splicing devices suitable for the use

Brazing, welding or soldering (with a mechanically

and electrically secure joint before soldering & then

soldered)

Splices

All splices and joints must be covered with an

insulation equivalent to that of the conductors

Hazardous Locations

Electrical installations

Equipment, wiring, and installations of equipment

in hazardous (classified) locations must be

intrinsically safe, approved for the location, or safe

for the location.


29/30


30/30

2/23/20

Training

OSHAs electrical safety-related work practice requirements arecontained in 29 CFR 1910.331-.335

De-energizing electric equipment before inspecting or making repairs

LOTO (1910.147)

Using electric tools that are in good repair

Using good judgment when working near energized lines

Using appropriate protective equipment

Thank You!

Documents

HSE-LS-13_Electrical_Safety.pdf