Electricity
Electrical safety at the workplace
Nowadays, electricity is used in every office and workplace. Electrical equipment, from computers and power tools to large machine tools, could potentially be dangerous if used or maintained improperly and cause a risk of electric shock or fire. Although no electrical safety training will be necessary for most employees, it is nevertheless essential to follow electrical safety requirements to ensure both one’s own and other people’s safety. Employees, whose activity is in the field of electrical or operational work or in the workplace of whom electrical hazards may be present (e.g. work with portable power tools, work under overhead lines), require specialised electrical safety training depending on the hazards that may be present.
Hazards related to the use of electrical equipment and installations at workplace
The main electrical hazards are:
- electric shock and burns caused by contact with live parts;
- injuries caused by contact with electric arcs due to short-circuiting;
- fire caused by faulty electrical equipment or installations;
- explosion caused by the ignition of highly flammable vapours or dust due to the use of static electricity or electrical equipment not suitable for explosive atmospheres.
Electric shock can also cause other types of injuries, e.g. falling off a ladder.
Reducing and preventing electrical hazards
To reduce and prevent electrical hazards, the electrical hazards in the workplace must be assessed:
- who may be affected by electrical hazards;
- how great the risk may be;
- what the necessary precautions are.
The risk assessment should take into account the condition of the electrical installation, the type of electrical equipment used, and the way and circumstances in which they are used.
It is necessary to ensure that:
- the electrical installation is compliant and safe to use;
- the electrical equipment is suitable for the intended purpose and use and that the equipment is used only for the intended purpose and in the intended manner.
The electrical equipment and installations used must be maintained and inspected regularly.
Users of electrical equipment, including portable equipment, must visually ensure that the housing of equipment and the power cord including the socket are not damaged or have burn marks (indicates overheating).
If damage or burn marks are present, the electrical equipment must immediately be removed from service. Only competent persons may repair electrical equipment.
Electrical equipment likely to be damaged (e.g. portable power tools which are moved regularly, used often or in difficult environments) must be inspected more frequently. Electrical equipment less likely to be damaged (e.g. desktop computers) may be inspected less frequently.
Workplace electrical installations must be maintained and inspected regularly. Such work may only be performed by persons with the necessary knowledge, skills and experience, i.e. competent persons. In the case of larger (main fuse exceeding 100 A) and more dangerous (explosion risk, high risk of accident, medical locations) electrical installations, a supervisor of competent use must be appointed. Depending on the type and age of the electrical installation, an electrical installation audit must be conducted periodically.
Electrical or operational work may be carried out by persons with the necessary technical and safety knowledge and experience. The electrical safety awareness and experience of the person performing electrical or operational work is verified by the person in charge of the electrical work or the supervisor for the use of the electrical installation or a competent authority or person acting on their behalf. The verification of electrical safety awareness should be documented.
The competence of the person in charge of electrical work and the supervisor of use of electrical installation must be proven, i.e. the person should hold a professional certificate or certificate of competency in electrical work.
Simpler electrical work may be carried out by other persons, e.g. changing switches, sockets, lampholders and fuses (but not installing new ones). It is permitted to repair or replace cord switches, lampholders, extension cords and cord plugs. Only competent persons are allowed to construct new electrical installations and install sockets and switches. The same goes for connecting and disconnecting fixed household appliances and switching unearthed sockets for earthed sockets. A list of simpler electrical work permitted to be performed by ordinary persons is available here.
- Employees need to know how to use electrical equipment safely.
- The housing of equipment and power cords should not be damaged. Switches and sockets must be intact and properly secured. Electrical equipment that is damaged may not be used.
- Sockets and extension cords should not be overloaded, as this can cause fire.
- Extension cords should not be placed in such a way that it could cause tripping or falling.
- The electrical equipment used, including hired equipment, must be suitable for use in the foreseen working environment.
- Electrical equipment used outdoors or in wet rooms (e.g. bathrooms, pools) must be intended for use in such conditions. The housings of inappropriate equipment may become energised and thereby pose a threat to the user.
- Electrical equipment may only be used outdoors and in wet rooms by connecting it to a mains supply equipped with a residual current device.
- Switchboards and locations of live parts must bear the electrical hazard sign. Switchboards should be kept closed to prevent accidental contact with live parts.
- Protective and switching apparatus must be marked so that power could quickly be switched off in case of danger.
- All cords, cables, plugs, sockets, and joints must be sufficiently strong and protected for the working environment. Cords and cables in passageways must be protected with additional mechanical protection.
- Before any maintenance or inspection work is started, the electrical equipment must be disconnected from the mains power supply.
- Electrical work may only be performed by competent persons who have the necessary knowledge, skills and experience to carry out such work.
- When repair and construction work is carried out in the building, it should be taken into account that there may be electric cables in the walls, floors and ceilings. Before the start of the work, the locations of cables must be determined.
- When performing work near or under overhead lines, the safety of the work performed must be ensured. Particularly dangerous are situations where equipment and machinery which are capable of reaching or touching overhead lines (e.g. ladders, scaffolding, cranes, dumpers) are used. To perform work in the protection zone of overhead lines, authorisation must be obtained from the owner of the overhead line, i.e. usually the network operator of the area.
- When digging on the street, pavement or near buildings, it must always be taken into account that underground cables may be present. Before the start of the work, the locations of underground cables must be determined. To perform work in the protection zone of underground cables, authorisation must be obtained from the owner of the underground cable, i.e. usually the network operator of the area.
- In explosive atmospheres, only electrical equipment intended for such conditions, including portable equipment, may be used. Explosive atmospheres may occur in various places, e.g. when working with paint sprayers, near fuel tanks, or in places where combustible aerosols, vapours, mists, gases or dusts are present. The electrical equipment and installations used in explosive atmospheres must be maintained and inspected regularly. The maintenance of such equipment may only be carried out by competent persons.
- Turn off the power.
- Call the emergency number 112, and while you wait:
- if the victim is breathing but unconscious, place them in the recovery position;
- if the victim is not breathing but has a pulse, begin rescue breathing immediately;
- if the victim has no pulse, begin CPR immediately.
Electrostatics
The materials can be electrically conductive or insulating. Conductive materials are, for example, metal work surfaces, while insulators (dielectrics) are plastic-coated work surfaces. Insulated work surfaces trap the electric charge and can increase it over time. Should this electric charge start to move, an electric current will be generated and it will no longer be static electricity. Static electricity can also increase in metal work surfaces if they are not grounded.
Humidity in the working environment and surface dirt on materials/work equipment can significantly affect the behaviour of charges. Therefore, there are many more manifestations of static electricity in dry weather than in wetter conditions.
Contact with an electrostatically charged surface can cause an electrical solution (i.e. getting ‘zapped’ by electricity). The electric charge of the human body and how strong the connection of the human body to the earth is also decisive here.
In electrostatics, it is important to understand the natural principle that charged bodies (or surfaces) balance their charges when coming into contact – nature seeks a balance. If there is no large difference of charges between them, there is no ‘zap’ in case of contact.
Electric charge can increase in surfaces as a result of industrial and other processes (such as surface friction). If these surfaces are isolated from the ground, the charge will not go anywhere and it will accumulate. When a sufficient charge is formed, a person will get ‘zapped’ by touching this surface.
Typical electrostatic fields are generated by the following work processes:
- pouring powders out of bags;
- screening/filtering;
- carriage by pipeline of liquids, powders and similar substances;
- spraying of liquids;
- mixing of liquids.
Hydrocarbon-containing liquids (oil, kerosene and various solvents) have a high electrical resistance and can emit explosive/flammable vapours. These properties make the abovementioned fluids particularly sensitive to electrostatic problems. High electrical resistance allows these substances to accumulate a strong electric charge. However, flammable vapours can also be ignited by smaller electrostatic sparks.
The most common risk factors are filters or injections that generate foam or steam during refuelling/filling.
It must be taken into account that the electrostatic charge can accumulate on both the dielectric (e.g. plastic) and the electrical conductors (e.g. metal), if the latter is isolated from the ground.
Health effects
Undesirable effects from the accumulation of static electricity are more easily manifested by the discomfort of getting ‘zapped’ by the charged surface, for example by touching are door handle. In severe cases, death may result if the spark from the electrostatic discharge were to cause an explosion/ignition in explosive/flammable gases or substances.
The physiological effects of electrostatic discharge range from unpleasant stings to vigorous reflexes. Stronger discharges can cause uncontrolled movements, which can result in falls. The severity of the physiological effects depends on the current of the electrical solution.
If an employee happens to be holding a tool or performing an important task during such an unwanted reflex, such uncontrolled movements may result in bodily injury to themselves or others in the work area.
As with other electromagnetic fields, the strength of the electrostatic field is greatest in its immediate vicinity (a few cm from the surface) and decreases exponentially as it moves away from the object.
Prevention
The prevention of electrostatic fields focuses on preventing the accumulation of static electricity on surfaces. Therefore, earthing is built on the work surfaces and, if necessary, the employees and their clothes are also earthed. Through the earth continuity connector, the generated charges are directed to the ground before they can even start to accumulate. Most effective, of course, would be to eliminate the electrostatic fields by not generating them at all.
The last resort is technical solutions to protect sensitive equipment from electrostatic discharges. However, the protection of equipment does not exclude other hazards resulting from electrostatics: ignition/explosion hazard and human exposure.
Work processes should be adapted to minimise exposure to materials that generate static electricity (e.g. glass and Teflon, PVC and nylon).
The electric charge generated due to friction can also be reduced by reducing the velocity of the two materials in contact with each other. For example, the speed of the conveyor line transporting the crushed material or the moving speed of liquids in the pipes is reduced.
Earthing of work surfaces and equipment
The main solution for electrostatic prevention is to equalise the potential difference between two objects (such as an operator and a machine). This is usually achieved through earthing.
There are situations where metal work surfaces/equipment isolated from the ground collect a charge through induction. In this way, a fairly strong charge can accumulate and high energy can be acquired.
Therefore, all metal parts of the device that are accessible to the worker must be earthed. However, this principle can be extended to all metal surfaces to which a worker may be exposed: door handles, frame structures, electronic components, tanks (especially in the chemical industry), vehicle bodies (which include transport hydrocarbon-based materials).
If all electrically conductive parts and surfaces were permanently earthed, they would have the same electrical potential and the risk of electric field and electrical solution would be minimised. However, the achievement of such a situation is hindered by the fact that not all surfaces/materials are conductors and cannot be changed for this purpose. It is also not possible to permanently earth mobile devices (e.g. cars, cordless electronic tools).
Protection of workers
If the worker does not wear special shoes with a conductive sole or is not otherwise earthed, there is a good chance that the body (and clothes) will have an electrostatic charge during the day. The charge can be increased by, for example, a synthetic material (e.g. a carpet) or a certain work process.
To minimise the risk of an electric discharge, the following can be done:
- reduce the unpleasant effect on the body by first touching a grounded surface with another metal object, such as a key;
- reduce the peak current by discharging itself into a material that dissipates electrostatic charge (for example, a special mat or earthing bracelet, the output of which is limited by a resistor).