igc2 - element 4 electrical (1st ed) v.1.0

7/27/2019 IGC2 - Element 4 Electrical (1st Ed) v.1.0

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Copyright RMS Publishing

IGC First Edition - IGC2 Element 4 - v.1.0 - Slide 1

860409

NEBOSH

InternationalGeneral Certificate


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860409

Licence details

RMS Publishing Limited

Victoria House, Lower High Street, Stourbridge DY8 1TA

ACT Associates Limited.

First Edition September 2007.

All rights reserved. No part of this presentation may be stored in a retrieval system, reproduced, or transmitted in any form or by any means,electronic, mechanical, photocopying, recording or otherwise without either the prior written permission of the Publishers.

This presentation may not be lent, resold, hired out or otherwise disposed of by way of trade in any form other than that in which it is published,without the prior consent of the Publishers.

This presentation may not be reproduced in any form without prior consent of the Publishers other than a single copy thumbnail handout forimmediate use by the tutor.

Whilst every effort is made to ensure the completeness and accuracy of the information contained herein, RMS/ACT can bear no liability for anyomission or error.

Issued to: Strabag

Single LicenceLicence No: 860409


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860409

NEBOSH



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860409

Unit IGC2

Control ofInternational

workplace hazards


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Element 4

Electrical - hazards

and control


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4.1 Identify the hazards and evaluate the

consequential risks from the use of electricity

in the workplace

4.2 Describe the control measures that should be

taken when working with electrical systems

or using electrical equipment

Learning outcomes

Electrical hazards and control


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4.1 Hazards and risks associated with

electricity at work

4.2 Control measures

Contents of element



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electricity at work


Contents of element



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Principles of electricity

If misused can be very dangerous and often fatal

Has a major danger

Sight, hearing and smell will not detect electricity

Contact with exposed conductors 240V can be lethal Number of electrical notifiable accidents is small

10-20 reported fatalities each year so severity is high

Accident often caused by complacency not ignorance

Hazards and risks associated with electricity at work



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Current - flow of electrons through a conductor

Current flows due to differences in electrical pressure

Differences are measured in volts

Direct current (DC) Alternating current (AC)

Resistance, inductance or capacitance

Impedance measured in ohms

Basic circuitry




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Source: RMS Publishin g


A basic electrical circuit




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Relationship between voltage, current and resistance

Electrical pressure = Volts (V)

Current = Amperes or Milliamperes (I)

Resistance = OHMS (R)

V = I x R




El t i l h d d t l


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An electric circuit under fault conditions showingresistances in the path of a fault current

Source: R. Gilmour .



El t i l h d d t l


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Relationship between voltage, current and resistance

By Ohms law;

Current = Voltage

Resistance




El t i l h d d t l


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Hazards of electricity

Shock

Electrical burns

Electrical fires

Explosions Secondary injuries



El t i l h d d t l


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Electric shock and its effects on the body

CURRENT (mA) LENGTH OF TIME LIKELY EFECTS0-1 Not critical Threshold of feeling. Undetected by person.1-15 Not critical Threshold of cramp. Independent loosening of the

hands no longer possible.15-30 Minutes Cramp-like pulling together of the arms, breathing

difficult. Limit of tolerance.30-50 Seconds to minutes Strong cramp like effects, loss of consciousness due

to restricted breathing. Longer time may lead to

fibrillation.50-500 Less than one heart period

(750 mS)No fibrillation. Strong shock effects.

Greater than one heart

period Fibrillation. Loss of consciousness. Burn marks.Over 500 Less than one heart period Fibrillation. Loss of consciousness. Burn marks.

Source: RMS Publishin g

Effects of current flowing in the human body



El t i l h d d t l


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Electric shock and its effect on the body

Factors influencing severity

Voltage

Frequency

Duration Resistance

Current path



El t i l h d d t l


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First aid treatment for electric shockIn case of electrical shock:

Do

Switch off or remove the plug

No remaining connection to the supply

Assess the situation

Call for qualified support

If safe, check the casualtys response



El t i l h d d t l


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Check

A - Airway - Is it open?

B - Breathing - Is the casualty breathing normally?

C - Circulation - Does the casualty have a normal

pulse?



Electrical ha ards and control


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Action

CPR

Recovery position

Keep the casualty under observation





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Do not

Do not go near the casualty until the electricity supply is

proven to be off

Do not delay

Do not wait





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Electrical burns

Direct

Electricity passing through the body

Burns to the skin and tissue

Indirect Short circuit contacts

Hot parts

Molten materials

Fire





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Electrical fires

Common causes

Wiring with defects such as insulation failure

Overheating of cables

Incorrect fuse rating Poor connections





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Portable electric equipment

Conditions and practices likely to lead to accidents Unsuitable equipment

Inadequate maintenance

Use of defective apparatus





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Injury results from the flow of electricity through the bodys

nerves, muscles and organs and causes abnormal function

to occur

Muscular spasm may be severe

Injuries may result from dislocation, impact with surrounding

objects or fall from a height

A tool may be dropped causing such injuries as burns or

impact injury to the user or others near by

Secondary hazards





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electricity at work


Contents of element




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Selection and suitability of equipment

It is critical to ensure that all electrical equipment is

suitable

Many tools are designed and provided for use in a

domestic situation and they may not be suitable for use in

the more arduous conditions of a construction site

Part of the selection process is to determine situations

where low voltage, such as 110 volt systems, can be used

in preference to 240 volts

Control measures




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Advantages and limitations of protective systems

Fuse

Wire melts = current breaks

Protects equipment not user

Fuse ratings may be wrongFuse rating calculation

Current (Amperes) = Power (watts)

Voltage (volts)

Control measures




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Earthing

Conductor connected to earth

Earth is lowest point of potential

Connected to equipment casing

Control measures




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Isolation

Excellent way of achieving safety for those that need to

work on or near the system

Can mean switching off and unplugging a portableappliance at times it is not in use

Check that the isolation has been adequate and effective

before work starts - tests on the system

Ensure the isolation is secure - lock off and tag outsystems

Control measures




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Reduced low voltage systems

Step down transformer (110v)

Centre tap to earth (55v shock)

Reduces effect of electric shock Portable

Control measures




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Residual Current Device (RCD)

Detects system current leaks

Response = 30mA and 30mS

Reduces effect of electric shock Protects the user

Fixed or portable

Built in test facility

Control measures




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Source: HSG107

Double insulation

2nd protective insulated layer

Not normally used with earth

Control measures




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Inspection and maintenance strategies

User checks

Formal inspection and tests

Frequency of inspection and testing

Records of inspection and testing Advantages and limitations of Portable Appliance Testing

(PAT)

Control measures




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User checks Damaged cable sheaths

Damaged plugs; cracked casing or bent pins

Taped or other inadequate cable joints

Outer cable insulation not secured into plugs or equipment

Faulty of ineffective switches

Burn marks or discolouration

Damaged casing Loose parts or screws

Wet or contaminated equipment

Loose or damaged sockets or switches

Control measures




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Formal inspection and testsPortable equipment check:

Use of correctly rated fuse

Effective cord grip

Secure and correct cable terminations

Control measures




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Formal inspection and testsFixed installations check:

Damaged or loose conduit, trunking or cabling

Missing, broken or inadequately secured covers

Loose or faulty joints

Loose earth connections

Moisture, corrosion or contamination

Burn marks or discolourisation Open or inadequately secured panel doors

Ease of access to switches and isolators

Presence of temporary writing

Control measures




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Frequency of inspection and testingDeciding the frequency

Factors:

Type of equipment

Whether its hand held

Manufacturers recommendations

Its initial integrity and soundness

Age Working environment

Likelihood of mechanical damage

Control measures




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Frequency of inspection and testingDeciding the frequency (continued)

Factors:

Frequency of use

Duration of use

Foreseeable use

Who uses it

Modifications or repairs Past experience

Control measures




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Records of inspection and testing Use a checklist recording that the appropriate checks

inspections and tests have been done

Common practice to add a label to the system or part of the

system to indicate that an inspection has taken place Personal electrical devices should be treated and tested as if

it were company property

Control measures




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Advantages and limitations of Portable Appliance Testing(PAT)

The first level of inspection would be carried out by the

operator before the appliance is used

Second check would be supplemented by a more formalvisual inspection by an appointed person

Third strategy would include the periodic combined inspection

and testing of the appliance by a competent person

Control measures




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electricity at work


Contents of element

ect ca a a ds a d co t o


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Element 4

Electrical - hazards

and control


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Unit IGC2

Control ofInternational

workplace hazards


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NEBOSH


igc2 - element 4 electrical (1st ed) v.1.0

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