Electrical Equipment Risk Assessment
The risk assessment covers the use of mains voltage bench-mounted and portable equipment and work on the fixed installation, including testing and maintenance. The equipment is not intended for use in flammable atmospheres and for medical applications.
Hazard and Risk
The hazards arising from the use of electrical equipment are:
- shock by direct or indirect contact with a live or charged conductor
- burns from contact with or proximity to a live or charged conductor, by exposure to a high-energy discharge or arc
- fires and explosions caused by the ignition of flammable substances and materials by electricity
- explosions caused by the rupture of equipment subjected to excess or large fault currents
- interruption to essential safety equipment by loss of electrical power.
If control measures (other than those necessary solely for the operation of the equipment) for safety are not in place and maintained then the likely risks are as follows.
- Electric shock: intolerable risk (likely, extremely harmful).
- Electric burn: moderate risk (unlikely, harmful).
- Fires and explosions: intolerable risk (likely, extremely harmful).
- Iterruption to essential services: moderate (unlikely, harmful).
People at Risk
Any person using or working near to electrical equipment may be at risk if the protective control measures are inadequate or are not maintained. Those in the vicinity of the equipment or the laboratory are at risk in the event of fire or explosions. Persons may be at special risk with high-voltage equipment, with equipment in hazardous flammable areas and in wet or other conducting environments, unless additional protective measures are applied.
A permanent installation designed, installed and tested to BS 7671 (IEE Wiring Regulations) will incorporate the following control measures.
- Insulation preventing contact with live conductors — protecting against shock and burns.
- Barriers or enclosures including shrouded terminal connections — preventing direct contact with live or charged conductors and protecting against shock and burns.
- Earthing, combined with current-interruption devices, such as fuses and circuit breakers — protecting against shock from line to earth currents.
- Automatic disconnection by fuses and circuit breakers — preventing overheating by excess current.
- Residual current devices — preventing shocks through earth leakage currents where earthing alone is not adequate protection.
- Sufficient socket outlets, avoiding the use of multiple adaptors or long cables.
- Protection against ingress or splashing by liquids or dusts by location or enclosure — preventing shock or high leakage currents.
- Explosion-protected equipment in flammable or explosive atmospheres — preventing fires and explosions.
- Non-interruptible or back-up supply for essential safety equipment.
In addition to the functional and protective measures in the electrical installation, other control measures for the fixed and portable electrical equipment include the following.
- Design and construction — preventing direct access to live conductors protecting against shock and burns.
- Earthing of exposed conducting parts by connection to the protective conductor of the fixed installation, in conjunction with a suitable fuse or circuit breaker — protecting against shock and burns (Class I equipment).
- Double or supplementary insulation, without the need for connection to the protective conductor of the fixed installation – providing electrical isolation from live conductors and protecting against shock and burns (Class II equipment).
- Reduced (110V ac) or extra low voltage (below 50V ac or 120V dc) equipment with power supplied from a centre-tapped-to-earth (CTE) transformer (touch voltage is therefore reduced to 50V) — protecting against shock and burns (Class III).
- Interlocking of removable covers on high-voltage or high-current equipment automatically isolating the power source if the panel is removed or if earth leakage is detected (electrophoresis and electrochemical analytical apparatus) — protecting against electric shock.
- Separation from hazardous atmospheres or the use of suitable explosion-protected equipment to protect against fire and explosion. Such equipment will be specially rated as EExd or EExe.
Modifications and other work on the installation should be in accordance with BS 7671 (IEE Wiring Regulations). A permit to work confirming the disconnection, isolation and locking-off procedures, and for testing and proving the system dead, together with all other necessary safety precautions, should be initiated by the person responsible for the installation and issued to those undertaking the work. On completion of the work, the installation should be checked before it is returned to normal operation.
Circuit diagrams and drawings must be updated following modifications to the installation.
Work on live equipment must be justified. A permit to work, detailing the protective insulated tools, equipment and other precautions to prevent injury, may be necessary. Non-essential persons must be prevented from approaching exposed live or charged conductors by suitable barriers or the presence of a second person.
Equipment should be used only for the purpose for which it is designed, and within its design rating or capacity in an environment for which it is suitable. Operation and maintenance should be in accordance with the supplier’s instructions and operating or maintenance manual.
Equipment should be checked by the user and damaged items, including flexible cords, should be removed from use.
Reduced voltage equipment (110V CTE) or equipment supplied from a safety extra low voltage (SELV) transformer (Class III) should be used where practicable. The transformer should comply with the requirements of BS EN 61558-2-23:2001 Safety of Power Transformers, Power Supply Units and Similar. Particular Requirements for Transformers for Construction Sites, from BSI Sales, ISBN 0580 373061. Double-insulated equipment should be used in preference to earthed equipment.
Heating appliances should have an excess temperature cut-out device or sensor that isolates the electrical power at a predetermined temperature. Such appliances should normally have enclosed heating elements, reducing the likelihood of ignition of flammable substances.
Domestic-type refrigerators should not be used for the storage of highly flammable liquids other than in vapour-tight sealed containers, unless all electric spark sources are removed from the interior compartment.
Equipment left running unattended should be clearly marked or labelled, detailing the emergency action and telephone numbers for contacting staff. Critical conditions of unattended experimental equipment (temperature, pressure, liquid level, voltage, etc) should be monitored and the electrical supply automatically disconnected if these conditions are not maintained within safe limits.
All fixed and portable electrical equipment should be marked for unique identification and arrangements made for each item to be checked routinely for safety by visual inspection and testing as appropriate.
Inspection and Testing for Safety
The electrical installation must be inspected and tested in accordance with BS 7671 (IEE Wiring Regulations) requirements before acceptance, after significant modifications have been made and, in any event, at intervals not exceeding five years.
Fixed and portable equipment, together with their flexible cords, cables and plugs, should be maintained for safety by visual inspections and testing. The details of the test programme, including the type of tests, the pass/fail criteria and the frequency of inspections, will depend on the type of equipment and the level of risk from its use and location.
Procedures for electrical emergencies should be established for:
- electric shock
- electrical fires
- loss of electrical power.
Although not mandatory, all laboratory workers should be given basic instruction and training in procedures to deal with electric shock and the management of electric shock casualties. Training should include procedures for isolating casualties from the supply, and resuscitation techniques.
All laboratory workers should be instructed and trained so that they know what action to take if fire occurs in electrical equipment, including the need for emergency disconnection where necessary and the selection of appropriate fire-extinguishing agents.
Loss of electrical power in the laboratory may require the provision of maintained fittings (escape lighting to allow workers to leave in safety, not to continue working) and an emergency standby power supply from a generator to power essential safety or other equipment.
Last reviewed 29 July 2020