01 Health & Safety

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A competent TECHNICIAN must be aware ofHEALTH AND SAFETY issues when dealing with computers, suchas lifting heavy objects such as COMPUTERS and MONITORS. They should be able to advise a user on how toavoid health hazards when using COMPUTERS and should also be able to identify basic electrical hazards.

A technician should know about the precautions that should be taken before undertaking any servicing, upgradingor fault finding on COMPUTERS and how to handle or storeCOMPUTERcomponents.

Finally they must understand the green issueswhen disposing ofCOMPUTERequipment.

LIFTING OBJECTS

From time to time you will be required to lift either a MONITORor aCOMPUTERfrom the floor or a desk so it is important to develop agood lifting technique to avoid injury.

Plan the lift by taking a moment to think about how and where youwill lift the object to.

Use handling aids such as handles and straps where possible. Do you need help with the object? Remove anyobstructions on the route. Consider resting mid-lift, perhaps on a table or bench in order for you to change grip orrelax for a moment.

There are two basic lifting posses called the SINGLE KNEE METHOD and the SQUAT METHOD. Which of theseyou use depends on the size and weight of the object.

SINGLE KNEE METHOD

Start with one knee on the floor, Place the leading leg slightly forward if this is more comfortable.

Use the strength of your arms to raise the object up onto your mid-thigh, then use the power of your legs to standup

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SQUAT METHOD

An alternate way to lift is to position the object in between your knees. Keeping your back straight and armsextended, begin to stand up using the power of your leg muscles, rather than your back, to generate the liftingforce.

Always adopt a good posture. Bend your knees so that your hands, when grasping the load, are as level with yourwaist as possible. Do not kneel or over-flex the knees. Keep your back straight by tucking in your chin. Leanforward over the load slightly as this helps maintain your balance and posture and to keep a good grip keepshoulders level and facing in the same direction as the hips.

Maintain a firm, secure grip. A hook grip is less strenuous than keeping the fingers straight. If you can, vary thegrip as you move to prevent strain.

Try not to jerk. Carry the object smoothly keeping control of the load. Move the feet and try not to twist the torsowhen turning to the side instead, face the way you want to go.

Twisting of your spine to reach for objects can cause muscle or ligament strain. Always turn around completely andmove your whole body towards the required object.

Put the load down, and then adjust the positioning if necessary. Take small steps when moving the object furtherand dont try to move it all in one go.

WORKING WITH COMPUTERS

Those working with keyboards and computer display screens for prolonged periods can

be exposed to a number of health hazards. The principal hazard relates to the arms.

The problems which can develop are referred to as WRULD (work related upper limbdisorder) or RSI (repetitive strain injury).

Applying ergonomic principles to the design, selection and installation of computerequipment, the design of the workplace, and the organization of the task can readilycontrol the risks.

The risk is only significant for those who use computer workstations intensively for a large part of each workingday.


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Guidance for the user(s)

Correct posture

Sit up straight in front of the keyboard and screen.Do not sit with your feet or legs crossed. Your feet should be flat on the ground and there

should be enough space under the desk/table to move your legs freely.

Lower arms and thighs should be parallel to the ground. If possible make adjustments tothe chair.

Using the keyboard

Make sure that the keyboard is tiltedThe wrists and fingers should line up directly with lower arms and not

be bent as you type

Do not hammer at the keyboard when typing and do not overstretchthe fingers

Using the mouse

Keep the mouse within easy reach. Wrists should not be leaning onanything nor leaning to the side.

Flex the hands and fingers to prevent cramps and achesTake frequent short pauses and take the hand off the mouse and let

the mouse arm hang straight down from the shoulder

Use alternative keyboard actions so that you are not continuallyusing the mouse

Change the mouse from right to left-handed use (or vice versa) fromtime to time

Avoiding eye and neck strain

Avoid long spells of work which can lead to tired eyes and discomfortAdjust the screen angle to avoid reflections and use the

blinds/curtains at the windows

If an eyesight problem is discovered after viewing the screen, then the eyes should bechecked. It maybe that the user requires a pair of glasses for working on a computer.

Adjust the screen angle to prevent straining the neck. Continually straining the neck willdevelop discomfort in the shoulders and back.

Take a breakIt is recommend that no work session should be longer

then 90 minutes without a break or change of activity

of at least 15 minutes

If aches and pains are experienced then these shouldbe investigated, and the length of the work session

should be reduced to 30 minutes followed by a 5

minute break

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Make sure the computer is at the right height for keying in and viewing the screen

GENERAL ELECTRICAL SAFETY

Always ensure equipment is fitted with the correctly rated FUSE

AFUSE is short for 'FUSIBLE LINK' and is the most basic type of overcurrent protection device.

The FUSE has two purposes. It protects the wiring if something goes wrong, and it can also protect us.

The FUSE consists of two METAL END CAPS fig 01, sometimes a GLASSENCLOSURE and LOW METAL POINT WIRE that connects the two ENDMETAL CAPS together.

This LOW MELTING POINT WIRE melts when the rating of the FUSE isexceeded and so protects the circuit

Lets just take the following example fig 02

Here we have the MAINS SUPPLYconnected to a FUSE thatis normally found in the MAINS PLUG. When the switch isthrown CURRENT is supplied to the computer as shown inour example

Now lets say a fault is developed in the computer, then theCURRENT will increase to a point where the LOW MELTINGPOINT WIRE RATING will be exceeded and it will melt fig03

If it has blown due to a fault, then the fault should be tracedand rectified before the FUSE is replaced.

FUSES in plugs are made in standard ratings. The mostcommon are 3A, 5A and 13A. The FUSE should be rated at aslightly larger current than needed for the device.

So if the APPLIANCE uses less than 3 AMPS like mostlightning circuits or lamps then we should use a 3 AMP FUSE

If the APPLIANCE uses less than 5 AMP such as MONITORS which include CRTS andTFTS, or COMPUTERS then you would replace the FUSE with a 5 AMP

But if the APPLIANCE uses a much higher rating but less than 13 AMP such as ELECTRICHEATERS then you would use a 13 AMP FUSE.

So why is it important to ensure the correct ratingFUSE is used? To answer this lets ask the question,can we use a 13 AMP FUSE in an APPLIANCE suchas a LAMP that only uses less than 2 AMPS

The answer is yes you can, lets see would happen ifyou did

Fig 01

Fig 02

Fig 03

Fig 04


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Here in our next example fig 04 we have connected the MAINS SUPPLYto a switch that is connected to a METERthat will measure the consumption ofAMPS

At one AMP everything appears to working fine, we should point out that most lamps would work on a CURRENTconsumption of less than this

Now lets assume that the lamp develops a fault and starts to draw more current, as in our example 2 AMPS

This continues and at 3 AMPS the FUSE would normally blow, but we have fitted a 13 AMP FUSE so all that willhappen is more current will flow

At 4 AMPS the lamp has now entered a dangerous pointand at 5 AMPS may catch fire fig 05

The next question is, can you use a 3 AMP FUSE in anAPPLIANCE that uses 13 AMPS,

Lets replace the FUSE in our example with a 3 AMP one

and the APPLIANCE with an ELECTRIC HEATERthatwill consume much more than 3 AMPS

Once we switch on the APPLIANCE starts to consume1 AMP, but theAPPLIANCE needs much more currentand it will attempt to draw moreAMPS fig 06

This will continue until the rating of the FUSE isreached, in our example 3 AMPS

The APPLIANCE will continue to try and draw moreand more current to a point where it will exceed 3

AMPS and the FUSE will blow and the circuit will fail.

In all cases, replace the FUSE with the correct rating.

An engineer should also be able to complete simpletasks such as wiring a MAINS PLUG and identify

any problems that may occur with it. If at any time you are doubtful always have your work checked by anotherengineer.

Here we can see a common 13 AMP PLUG fig 07. You will find three WIRES and the industrial colours are,

BLUE for NEUTRAL and when wired into the MAINS PLUG will be on the left-handside as shown

The GREEN WIRE with aYELLOW TRACERis the EARTH WIRE and as shown isconnected to the CENTRE PIN

The BROWN WIRE is known as the LIVE WIRE and is connected to the right-handpin.

NEVERconfuse these WIRES as it can be extremely dangerous

Two other items we should be aware of, is the OUTER INSULATION and theCABLE GRIP

Fig 05

Fig 06

Fig 07


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Some MAINS LEADS or more commonly known as KETTLE LEADS have a moulded plug at one end fig. Theseare not serviceable and cannot be opened. However the FUSE can be replaced by opening the FUSE HOLDERfound on the underneath of the PLUG fig 09

Any electrical mains socket or cable that looks defective fig 10, mustnever be used and should be reported to the user or the appropriate

body.

WIRING A13 AMP MAINS PLUG

Just so we can be clear we shall wire a 13 AMP MAINS PLUG onto a cable.

We call this fig 11, a 13 AMP MAINS PLUG because the maximum currentconsumption is 13 AMPS. So this is suitable for any APPLIANCE that is 13 AMPSor less

To complete this TASKwe shall need a hobby knife fig 12 or wire cutters and a basictoolkit

The two SCREW DRIVE BITS we shall be using is aPOZIDRIVand a FLAT BIT fig 13

To open the MAINS PLUG, which is normally heldtogether with one fixing screw, we shall be using theFLAT BIT

Next we need to loosen the CABLE GRIP, bycompletely removing one of the SCREWS and

slacking off the other using the POZIDRIV BIT we move the CABLE GRIP to oneside as shown fig 14

The OUTER INSULATION will need removing so wecan get some idea on how much by measuring thelongest WIRE fig 15, which is the EARTH WIRE, this willbecome clearer

Use the HOBBY KNIFE to lightly cut around the OUTERINSULATION fig 16

Now bend the OUTER CABLE and this should break. Continue to do this all around untilyou can pull away the OUTER INSULATION, this should have exposed the three internalWIRES

Next we need to trim these down

Fig 08

Fig 09Fig 10

Fig 11

Fig 12

Fig 13

Fig 14Fig 15


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Move each one over the respective TERMINAL then add about 5 m/m, cut to sizeusing SIDE CUTTERS fig 17

If we place this in position now we should find that eachWIRE reaches the respective TERMINAL plus 5 m/m

Each of these WIRES will need stripping back to exposeabout 10 m/m of bare WIRE

Once again use the WIRE CUTTERS rotate the WIRE while nipping the INSULATION of the WIRE. Careful notto put to much pressure on as this will cut straight through the WIRE, do the same to the other two WIRES thentwist the end of each WIRE

Now folded each one overso each one will now be about 5 m/m in length

Each of these can now be inserted into their respective TERMINAL. In most cases it is best

to pull the TERMINALS OUT as shown here fig 18

Temporally screw them into the TERMINALS

Once in then nip them up to ensure a good connection

Replace the TERMINALS back into the PLUG

Route the WIRES in the PLUG fig 19

Then replace the CABLE GRIP SCREW and tighten them both

Make final checks that the WIRES are routed in the correct way

Some MAINS PLUGS have an extra piece of plastic that the CABLE is widget intoas should here instead of the conventional CABLE GRIP

Finally replace the top of the PLUG

Before leaving the subject of wiring a MAINS PLUG we should be aware of some pitfalls that can occur whenpreparing the CABLE

The most common is when we remove the OUTER INSULATION and the knife is pressed too deep

This not only cuts through the OUTER INSULATION but also one or more of the INTERNALWIRES.

This may not be apparent at first but after a long use these cuts can become exposed and potentially cause aproblem by shorting against each other or more serious, BE exposed to the USER

The next area is when the WIRES are not trimmed to the correct size, that causes the WIRES to become trappedbetween the plug.

Finally the ends of the WIRES if not trimmed correctly can expose each wire. Another problem is the CABLE GRIPon the INTERNAL WIRES and not the OUTER CONDUCTORas it was designed for.

Fig 16

Fig 17

Fig 18

Fig 19


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Date Students Signature

Notes:

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publisher, author and retailer who have approved the contents shall not be liable to any person or entity with respectto loss or damage caused or alleged to be caused directly or indirectly by what is contained or left out of them.

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01 Health & Safety