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SJE Electrical Installations
Electrical safety
INTRODUCTION : Provided by the HSE
Electricity can kill. Each year about 1000 accidents at work involving electric
shock or burns are reported to the Health and Safety Executive (HSE). Around 30
of these are fatal. Most of these fatalities arise from contact with overhead or
underground power cables.
Even non-fatal shocks can cause severe and permanent injury. Shocks from faulty
equipment may lead to falls from ladders, scaffolds or other work platforms.
Those using electricity may not be the only ones at risk: poor electrical
installations and faulty electrical appliances can lead to fires which may also
cause death or injury to others. Most of these accidents can be avoided by
careful planning and straightforward precautions.
WHAT ARE THE HAZARDS?
The main hazards are:
contact with live parts causing shock and burns (normal mains voltage, 230 volts
AC, can kill);
faults which could cause fires; fire or explosion where electricity could be the
source of ignition in a potentially flammable or explosive atmosphere, eg in a
spray paint booth.
ASSESSING THE RISK
Hazard means anything which can cause harm. Risk is the chance, great or small,
that someone will actually be harmed by the hazard.
The first stage in controlling risk is to carry out a risk assessment in order
to identify what needs to be done. (This is a legal requirement for all risks at
work.) When carrying out a risk assessment: identify the hazards; decide who
might be harmed, and how; evaluate the risks arising from the hazards and decide
whether existing precautions are adequate or more should be taken; if you have
five or more employees, record any significant findings; review your assessment
from time to time and revise it if necessary.
The risk of injury from electricity is strongly linked to where and how it is
used.
The risks are greatest in harsh conditions, for example: in wet surroundings -
unsuitable equipment can easily become live and can make its surroundings live;
out of doors - equipment may not only become wet but may be at greater risk of
damage; in cramped spaces with a lot of earthed metalwork, such as inside a tank
or bin - if an electrical fault developed it could be very difficult to avoid
shock.
Some items of equipment can also involve greater risk than others. Extension
leads are particularly liable to damage - to their plugs and sockets, to their
electrical connections, and to the cable itself. Other flexible leads,
particularly those connected to equipment which is moved a great deal, can
suffer from similar problems.
Ensure that the electrical installation is safe
install new electrical systems to a suitable standard, eg BS 7671 Requirements
for electrical installations, and then maintain them in a safe condition;
existing installations should also be properly maintained; provide enough
socket-outlets - overloading socket-outlets by using adaptors can cause fires.
Provide safe and suitable equipment
choose equipment that is suitable for its working environment; electrical risks
can sometimes be eliminated by using air, hydraulic or handpowered tools. These
are especially useful in harsh conditions; ensure that equipment is safe when
supplied and then maintain it in a safe condition; provide an accessible and
clearly identified switch near each fixed machine to cut off power in an
emergency; for portable equipment, use socket-outlets which are close by so that
equipment can be easily disconnected in an emergency; the ends of flexible
cables should always have the outer sheath of the cable firmly clamped to stop
the wires (particularly the earth) pulling out of the terminals; replace damaged
sections of cable completely; use proper connectors or cable couplers to join
lengths of cable.
Do not use strip connector blocks covered in insulating tape; some types of
equipment are double insulated. These are often marked with a double-square
symbol . The supply leads have only two wires live (brown) and neutral (blue).
Make sure they are properly connected if the plug is not a moulded-on type;
protect light bulbs and other equipment which could easily be damaged in use.
There is a risk of electric shock if they are broken; electrical equipment used
in flammable/explosive atmospheres should be designed to stop it from causing
ignition. You may need specialist advice.
Reduce the voltage
One of the best ways of reducing the risk of injury when using electrical
equipment is to limit the supply voltage to the lowest needed to get the job
done, such as: temporary lighting can be run at lower voltages, eg 12, 25, 50 or
110 volts; where electrically powered tools are used, battery operated are
safest; portable tools are readily available which are designed to be run from a
110 volts centre-tapped-to-earth supply.
Provide a safety device
If equipment operating at 230 volts or higher is used, an RCD (residual current
device) can provide additional safety. An RCD is a device which detects some,
but not all, faults in the electrical system and rapidly switches off the
supply. The best place for an RCD is built into the main switchboard or the
socket-outlet, as this means that the supply cables are permanently protected.
If this is not possible a plug incorporating an RCD, or a plug-in RCD adaptor,
can also provide additional safety. RCDs for protecting people have a rated
tripping current (sensitivity) of not more than 30 milliamps (mA). Remember: an
RCD is a valuable safety device, never bypass it; if the RCD trips, it is a sign
there is a fault. Check the system before using it again; if the RCD trips
frequently and no fault can be found in the system, consult the manufacturer of
the RCD; the RCD has a test button to check that its mechanism is free and
functioning. Use this regularly.
Carry out preventative maintenance
All electrical equipment and installations should be maintained to prevent
danger. It is strongly recommended that this includes an appropriate system of
visual inspection and, where necessary, testing. By concentrating on a simple,
inexpensive system of looking for visible signs of damage or faults, most of the
electrical risks can be controlled. This will need to be backed up by testing as
necessary. It is recommended that fixed installations are inspected and tested
periodically by a competent person. The frequency of inspections and any
necessary testing will depend on the type of equipment, how often it is used,
and the environment in which it is used. Records of the results of inspection
and testing can be useful in assessing the effectiveness of the system. More
detailed guidance is available in the booklets listed on pages 6 - 8. Equipment
users can help by reporting any damage or defects they find.
Work safely
Make sure that people who are working with electricity are competent to do the
job. Even simple tasks such as wiring a plug can lead to danger - ensure that
people know what they are doing before they start.
Check that:
suspect or faulty equipment is taken out of use, labelled DO NOT USE and kept
secure until examined by a competent person; where possible, tools and power
socket-outlets are switched off before plugging in or unplugging; equipment is
switched off and/or unplugged before cleaning or making adjustments. More
complicated tasks, such as equipment repairs or alterations to an electrical
installation, should only be tackled by people with a knowledge of the risks and
the precautions needed. You must not allow work on or near exposed live parts of
equipment unless it is absolutely unavoidable and suitable precautions have been
taken to prevent injury, both to the workers and to anyone else who may be in
the area.
Underground power cables
Always assume cables will be present when digging in the street, pavement or
near buildings. Use up-to-date service plans, cable avoidance tools and safe
digging practice to avoid danger. Service plans should be available from
regional electricity companies, local authorities, highways authorities, etc.
Overhead power lines
When working near overhead lines, it may be possible to have them switched off
if the owners are given enough notice. If this cannot be done, consult the
owners about the safe working distance from the cables. Remember that
electricity can flash over from overhead lines even though plant and equipment
do not touch them. Over half of the fatal electrical accidents each year are
caused by contact with overhead lines. More detailed guidance on avoidance of
danger from overhead electric lines is available from
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