Stonemasonry Department 2012
An Introduction for Stonemasons
There are various ways we supply power to electrical power tools on a
construction site. Battery operated tools are the easiest to set-up but are
not always suitable for heavy masonry work. Generally we work using 110
volts supplied from the mains (230 volts) through a step down
transformer. When there is not ready access to a mains supply we can
use a petrol driven generator to supply the power.
BATTERY TRANSFORMER GENERATOR
Power is transferred from the supply to the equipment or machinery using
colour coded cables. It is important that you are able to identify what
each cable is used for as using the incorrect cable on a construction site can
have disastrous consequences. The plugs at the end of the cables denote
the correct voltage they are designed for although you should always check
the manufacturers guidelines before use.
110 VOLT 230 VOLT 415 VOLT
As well as transmitting electrical power through the appropriate cables, it is
often necessary to split the electrical feed to a number of different sources.
Splitters and junction boxes are used to achieve this. Before using any
equipment to divert electrical power you should ensure it is safe to do so.
Residual Current Devices
A residual current device (RCD) is an
electrical wiring device that
disconnects a circuit (cuts the power)
when it detects a problem with the
These devices have the potential to
save a person from serious injury or
The image on the right shows an
RCD plug that is plugged into a 230V
supply. The electrical device is then
plugged into the RCD plug.
Remember to test an RCD before use
by pressing the test buttons.
In order to improve electrical safety on site, a number of signs are used to
highlight hazards, risks, precautions and dangerous areas. It is essential that
you are aware of the meaning of these signs to reduce the chance of
injuring yourself or others.
Switch off and unplug the equipment
before you start any checks.
Check that the plug is correctly wired
(but only if you are competent to do so).
Ensure the fuse is correctly rated by
checking the equipment rating plate or
Check that the plug is not damaged and
that the cable is properly secured with
no internal wires visible.
Check the electrical cable is not damaged and has not been repaired with
insulating tape or an unsuitable connector. Damaged cable should be replaced
with a new cable by a competent person.
Check that the outer cover of the equipment is not damaged in a way that will give
rise to electrical or mechanical hazards.
Check for burn marks or staining that suggests the equipment is overheating.
Position any trailing wires so that they are not a trip hazard and are less likely to
Equipment User Checks
110v – Weekly
230v - Daily
110v – Monthly
230v - Weekly
110v – 3 monthly
230v - Monthly
Cables Before use Annually Biannually
Although these checks are not necessary every time you use a power tool it
is good practice to check over a tool before use, making sure it appears in
good condition, is suitable for the job and is being used with the correct
voltage. HSE recommend the following inspection timetable for electrical
equipment in the construction industry:
Voltages as low as 50 volts can cause
electrical signals between the brain and
muscles to become distorted. This can cause
the heart to stop beating properly, prevent a
person from breathing and may also cause
The severity of electric shock will depend on
the size of the voltage, which parts of the
body are involved, how damp a person is and
the length of time the current flows.
Electrical burns are caused by an electrical
current heating tissue as it passes through
the body. Burns will not always be visible
except on point of entry but they will often
be permanently disabling and need major
Loss of Muscle Control
As a side product of an electric shock, loss of
muscle control can lead to more debilitating
injuries. People are often unable to let go or
move away from the source of electricity due to
loss of muscle control which increases their
exposure. Those working at height or in
confined spaces may also be injured as a result
of being thrown by the force of the electric
Thermal burns are caused by operatives
coming into contact with faulty electrical
equipment which heats or ignites its
surroundings. Hand held portable power tools
are susceptible to having handles heat up to
dangerous levels and those working with or
near flammable materials have to be vigilant
against ignition of such materials.
The following list offers tips on how to work safely when using electricity. The list is
not exhaustive and you should always make sure you are completely aware of how
to carry out any activity safely before starting work.
Ensure you have read and understood the method statement and relevant risk
assessments before carrying out any activity.
Always use the correct equipment for the activity and use equipment as intended
by the manufacturer.
Always use the correct electrical supply (normally 110V on a construction site).
Never use electrical equipment when standing in or near water.
Always carry out appropriate inspections on any electrical equipment before use.
Never work alone when using electrical equipment.
Always wear appropriate Personal Protective Equipment (e.g. rubber soled
footwear) when using electrical equipment.
Developed by The Stonemasonry Department
City of Glasgow College