Topic of the Month: Electrical Safety

Electrical Safety

  (Photo: BC GmbH/Rüther)

Working with electricity can be dangerous. Engineers, electricians, and other professionals work with electricity directly, including working on overhead lines, cable harnesses, and circuit assemblies. Others, such as office workers and salespeople, work with electricity indirectly and may also be exposed to electrical hazards.
E
lectrical current exposes workers to a serious, widespread occupational hazard; practically all members of the workforce are exposed to electrical energy during the performance of their daily duties, and electrocutions occur to workers in various job categories. Many workers are unaware of the potential electrical hazards present in their work environment, which makes them more vulnerable to the danger of electrocution.

Electrical injuries consist of four main types: electrocution (fatal), electric shock, burns, and falls caused as a result of contact with electrical energy.

Many deaths and injuries arise from:

• use of poorly maintained electrical equipment;
  
• work near overhead power lines;
  
• contact with underground power cables during excavation work;
  
• mains electricity supplies (230 volt);
  
• use of unsuitable electrical equipment in explosive areas such as car paint spraying booths;

Fires started by poor electrical installations and faulty electrical appliances cause many additional deaths and injuries.

Electrical injuries
Electrical injuries can be caused by a wide range of voltages but the risk of injury is generally greater with higher voltages and is dependent upon individual circumstances.

Alternating current (AC) and Direct Current (DC) electrical supplies can cause a range of injuries including:

• Electric shock
  
• Electrical burns
  
• Loss of muscle control
  
• Thermal burns

Electric shock
A voltage as low as 50 volts applied between two parts of the human body causes a current to flow that can block the electrical signals between the brain and the muscles. This may have a number of effects including:

• Stopping the heart beating properly
  
• Preventing the person from breathing
  
• Causing muscle spasms

The exact effect is dependent upon a large number of things including the size of the voltage, which parts of the body are involved, how damp the person is, and the length of time the current flows.

Electric shocks from static electricity such as those experienced when getting out of a car or walking across a man-made carpet can be at more than 10,000 volts, but the current flows for such a short time that there is no dangerous effect on a person. However, static electricity can cause a fire or explosion where there is an explosive atmosphere (such as in a paint spray booth).

Electrical burns
When an electrical current passes through the human body it heats the tissue along the length of the current flow. This can result in deep burns that often require major surgery and are permanently disabling. Burns are more common with higher voltages but may occur from domestic electricity supplies if the current flows for more than a few fractions of a second.

Loss of muscle control
People who receive an electric shock often get painful muscle spasms that can be strong enough to break bones or dislocate joints. This loss of muscle control often means the person cannot 'let go' or escape the electric shock. The person may fall if they are working at height or be thrown into nearby machinery and structures.

Thermal burns
Overloaded, faulty, incorrectly maintained, or shorted electrical equipment can get very hot, and some electrical equipment gets hot in normal operation. Even low voltage batteries (such as those in motor vehicles) can get hot and may explode if they are shorted out.
People can receive thermal burns if they get too near hot surfaces or if they are near an electrical explosion. Other injuries may result if the person pulls quickly away from hot surfaces whilst working at height or if they then accidentally touch nearby machinery.
A single low voltage torch battery can generate a spark powerful enough to cause a fire or explosion in an explosive atmosphere such as in a paint spray booth, near fuel tanks, in sumps, or many places where aerosols, vapours, mists, gases, or dusts exist.

Simple precautions
There are some simple precautions that can be taken that will significantly reduce the risk of electrical injury to you and others around you:
Work near electricity

• Undertake a risk assessment for the work you are planning, and make sure this covers electrical hazards.
  
• Learn how to recognise electrical wires. These may be overhead power lines, electrical wiring in a workplace, or cables buried under the ground.
  
• Get an up-to-date map of the services in the area and use it.
  
• look for electrical wires, cables or equipment near where you are going to work and check for signs warning of dangers from electricity, or any other hazard. Remember to look up, down, and around you.
  
• If you will be digging or disturbing the earth, use a cable locator to find buried services and permanently mark the position of services you do find.
  
• Work away from electrical wiring wherever possible. If you have to work near electrical wiring or equipment, ask for the electrical supply to be turned off. Make sure the power is off, and cannot be turned on again without you agreeing.
  
• If the electrical supply cannot be turned off, consult a competent person who should be able to advise you on the best way to proceed.
  
• Identify where it is safe to work. Put up danger notices where there are still live electrical circuits, and warn your co-workers where it is safe to work and where it is not safe. Remember to remove notices at the end of the work.

Work using electrically powered equipment

• Perform a risk assessment to identify the hazards, the risks arising from those hazards, and the control measures you should use.
  
• Check that the electrical equipment is suitable for the work and way in which it is going to be used.
  
• Check that the electrical equipment is in good condition. The priced HSE booklet 'Maintaining portable and transportable electrical equipment' will help you do this.
  
• Check that the equipment is suitable for the electrical supply with which it is going to be used, and the electrical supply is safe.
  
• It is often beneficial to use a Residual Current Device (RCD) between the electrical supply and the equipment.
  
• Make sure that the user of the equipment is trained to use it safely and can keep others safe.
  
• Make sure the user knows which personal protective equipment to wear, how to use it, and make sure they do.

Work on electrical equipment, machinery or installations
Work on electrical equipment, machinery or installations should be:

• thoroughly planned;
  
• done by people who can demonstrate competence;
  
• applying suitable equipment and work standards.

Planning
It is essential that equipment, machinery or installations are prepared for the work to be carried out. This includes the isolation and release of all sources of energy (electrical, mechanical, hydraulic, pneumatic, etc), and may also involve additional work such as decontamination or the construction of a safe working platform. Isolation of energy sources should be secure, meaning that energy cannot be inadvertently re-introduced into the equipment, machinery or installation.

All work should be thoroughly planned so that it can be done safely and so that the completed installation or equipment is safe. The priced HSE booklet Electricity at work, safe working practices provides information on how to plan electrical work in a wide range of industries. The priced HSE guidance Electrical safety on construction sites provides information on how to plan electrical installations on construction sites.

Particular care should be taken when repairing equipment that is safety related such as equipment in a potentially explosive atmosphere, or which guards against contact with moving machinery. You should make sure that the repair will not prevent the correct operation of the equipment or adversely affect its safety in any way.

Competence

• People working on electrical equipment, machinery or installations must be competent to do so. The level of competence required to do a task is dependent upon the complexity of that task and the amount of knowledge required. Assessing the)
  
• Regular re-assessment.

People who cannot demonstrate competence should not be allowed to work unless they are supervised by someone who is.
The Memorandum of guidance on the Electricity at Work Regulations 1989 provides information on competence.

Equipment and work standards
Equipment that is installed should be suitable for the task it will perform and the environment within which it will be expected to work. A wide range of electrical equipment and work is covered by recognised standards that offer guidance on good engineering practice.

Further information

Electrical Safety - Basic Information
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Electrical safety and you
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Electrical Safety: Low Voltage Directive (LVD)
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Advice for sme
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Working Safely with Electricity. OSHA Fact Sheet
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Portable Generator Safety. OSHA Quick Card
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Electrical safety in overhead power lines
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Electrical safety in potentially explosive atmospheres
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Ergonomic Survival Guide for Electricians
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Controlling Electrical Hazards
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Electrical Safety: Safety and Health for Electrical Trades--Student Manual
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