SJE Electrical Installations.
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 lightbulbs
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 HSE.
*Please note: we only carry out work within the Sheffield and Hope Valley areas
