outcome1 s5 electric shock

8/4/2019 Outcome1 S5 Electric Shock

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Unit 1Working Effectively and Safely in an

Electrotechnical Environment

Outcome 1Identify the legal responsibilities of both employer

and employee and the importance of Health andSafety in the working environment

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Review of Health & Safety legislation

To briefly run through what we have learnt so far;

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HASWA was introduced to provide a framework within which allother Health & Safety legislation would operate.

All employers have the legal responsibility, to ensure that thework place is safe for employees. Employees are responsible forthe safety of themselves and others.

Personal protective clothing is concerned with the whole body. Itis essential and should always be worn when appropriate.

For a fire to occur there needs to be three things, heat, fueland oxygen. There are 4 classes of fire and each needs adifferent type of extinguisher. All extinguishers are coloured

red. There are five types of warning signs which have colours instead

of words to distinguish their importance, and are now commonacross Europe.


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Outcomes from this session

At the end of this session you should beable to

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State the basic action to be taken in the event

of an electric shock.State the need for isolation before any work iscarried out on an electrical installation orsystem.


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Electric Shock

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There is no point at which electricity is safe andtherefore should always be treated with respect

A definition of an electric shock is an unpleasant sensationproduced by the nerves response to a passage of electric

current through a part of the body.

To receive an electric shock you must become part of thecircuit.

The severity of a shock depends on many things, age, sex,state of health, moisture content of the surroundings. The

shock usually causes irregular beating of the heart and burnsto the body.


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Table Showing Levels at Which Electric Current Can Be

Perceived and the Possible Damage Caused

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Current inmA

Effect

0.5-2 Threshold of perception

2-10 Painful sensation, increasing with current

10-25 Cramp and inability to let go. Increase in bloodpressure. Breathing difficulties caused by muscularcontractions of the lungs

25-80 Severe muscular contractions sometimes with bonefractures. Increased blood pressure. Loss ofconsciousness from heart and breathing failure

80+ Burns at point of contact. Death from heart failure

From this you can see just how dangerous electricity can be


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Threshold of Perception

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Current is between 0.5mA to 2mA.

This is not very much at all.


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Let go Level

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Current ranges up to approximately 10mA. This level ofcurrent is likely to hurt. The pain increases with level ofcurrent.


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Hold on Level

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The point at which you are likely to find it difficult to let

go of the object ranges from 10mA to 25mA

Your blood pressure will rise and you may experience difficultybreathing.


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Throwing Level

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At current in excess of 25mA you are at risk from being thrownby the electric shock that you are receiving.

Bones maybe broken, blood pressure rises and there maybe loss ofconsciousness


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What to Do in the Case of an

Electric Shock ?

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Do not touch the person.

Shout for help.

Switch off the supply if possible.

If switching off the supply is not possible. Use some insulating

material such as a scarf, piece of wood, newspaper etc to pull theperson away from the contact.

If the heart has stopped breathing send for help before startingresuscitation or heart massage.

Treat burns.

Check for other injuries, treat if possible.

Do not try to give any treatment that you have not been trained to give.You could cause more harm than good.

Get help from experts as soon as possible


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Causes of Electric Shock

There are two ways of receiving an electric shock

BS7671:2008 17th Edition, covers this by giving us two terms that breakthese down, they are;

Basic Protectionand Fault Protection

(these were formerly know as Direct contact & Indirect contact

In the previous 16th edition of the BS7671)

I mention this as you may hear these terms or have been usedTo using them


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Basic Protection

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Is coming in contact with something that you would normally expectto be live

This could be youif you do not check

for hidden live cables

The person makes up the circuit from the source, through the person toearth.

No circuit - No shock


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Fault Protection

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Fault Protection is coming into contact with parts of anelectrical system that only become live under fault conditions

Main bondingconductors

Gas WaterEarth terminal in

Consumer unit

Cold Hot

This type of source is rarely 230V; that is not to say thatit is any less dangerous


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Isolation

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You will have realised that with this amount of danger it

is essential that a good means of isolation is used .

It is equally important that in the process of finding out

whether a circuit is live or not, no mistakes are made.

Safe procedures need to be observed not only when

working with equipment but also when testing.


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Test Equipment

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For testing a potentially live source two pieces of equipmentare required

Approved voltage tester (not a neon screwdriver) Voltage proving unit


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Approved Voltage TesterShould have the following;

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Adequate insulation Have finger barriers to stop hands slipping

Insulated tips so that more than 4mm (preferably 2mm) ofbare metal is showing

Fused leads Flexible and robust enough for use

Sheathed to prevent mechanical damage

Long enough for the purpose

No parts accessible to fingers even if the lead becomesloose

Coloured leads where necessary


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Diagram of an Approved Voltage

Tester

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Metal end tip not to protrudemore than 2mm when in use

Rubber insulatedflexible cable

Finger barrier

Spring loadedinsulated sleeves

Voltageindicator 50 400200100

56075 150 240

VOLTAGE INDICATOR

DC RANGE

AC RANGE


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Proving Unit

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A tester is no good if we are not sure of its

effectiveness, to guarantee effectiveness we need to use a

proving unit.

A proving unit is a d.c. voltage source that checks its own

status and is then a known reference voltage against which

the voltage tester can test itself.


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Safe Isolation Procedure

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You will need to have a lot more knowledge and training before you

start testing, there are a series of processes that you need to gothrough to complete the testing procedure. These have beensimplified into a block diagram

This may seem a long and

complicated process but to cut

corners might mean yours or

someone else's death.

Plan the jobUnplug anyequipment

Securely isolate it

Prove the testinstrument

Prove that theequipment is dead

Post caution andwarning notices

Attach temporaryearth leads if

necessary

Consider the need foradditional precautions

Re-prove thetest instrument

Ensure youunderstand the jobbefore you start it

outcome1 s5 electric shock

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