Stonemasonry Department 2012

Electrical SafetyAn Introduction for Stonemasons

Electrical Supply

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

Electrical Cables

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

Electrical Transmission

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.

THREE-WAY

SPLITTER

JUNCTION BOX

Residual Current Devices

RCD PLUG

A residual current device (RCD) is an electrical wiring device that disconnects a circuit (cuts the power) when it detects a problem with the electric current.

These devices have the potential to save a person from serious injury or lethal shock.

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.

Electrical SignageIn 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.

Equipment Inspection

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 instruction book.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 get damaged.

Equipment Inspection

Equipment User Checks Formal Visual Inspection

Combined Inspection and

Test

Hand held

power tools

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:

Electrical InjuriesElectric ShockVoltages 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 muscle spasms.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 BurnsElectrical 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 surgery.

Electrical InjuriesLoss of Muscle ControlAs 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 shock. Thermal BurnsThermal 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.

Working SafelyThe 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 DepartmentCity of Glasgow College

2013