Luminaires for hazardous areas: a guide to selection
Luminaires for hazardous areas: a selection guide!
Vision is one of the major negative health effects associated with working in inappropriate lighting conditions. The most common causes are glare caused by excessive light in the environment and the physical and mental effort used to work in low light conditions.
Consequently, inappropriate lighting often leads to inappropriate behaviour: this means that choosing the right lighting is very important, this is even more so in hazardous areas (blast zones) where the need to have adequate lighting to work according to safety standards must be combined with the ability of the instrument to contain a possible explosion.
The characteristics of a lighting fixture are essentially three:
• Protection: lighting equipment is a protected case that contains and protects lamps, lampholders, power switches, terminals.
• Electrical safety: lighting equipment must comply with EN standards with a sufficient degree of protection.
• Lighting functions: refers to the luminous flux emitted by the lamps. It is important to make a lighting calculation specifically for the area to be illuminated.
To create a lighting design, the following concepts need to be considered:
– reflection (when a wave hits a smooth object that is larger than the wave itself, depending on the medium, the wave may be reflected in a different direction); – scattering (occurs when the wavelength of a signal is larger than the pieces of the medium, the signal is reflected from or passes through it due to collisions with other particles). Scattering occurs randomly, and for this reason it differs from reflection and refraction, which change in a regular and deterministic way;
• refraction (deflection of a wave as it passes from one medium to another, the speed of its propagation changes).
When designing a lighting system, it should also be recognised that the efficiency of lighting fixtures decreases over time due to ageing and dust deposits on reflectors and diffusers.
The type of lamp must then be specified in the lighting calculation. For explosion-protected luminaires this means:
– type of lighting (LED or not); – protection mode (Ex d, Ex e, Ex n); – Ex d – flameproof: the main feature is the robust and sturdy construction, which guarantees high reliability for a long time. Ex d luminaires, usually made of aluminium alloy and borosilicate glass, are used in places where, in addition to explosion protection, good mechanical protection of the equipment is required; – Ex e – increased safety: the main feature is that equipment with this method of protection is designed to prevent sparks even in abnormal operating conditions. Ex e luminaires are usually made of plastic resins such as polyesters and polycarbonates, which make them lightweight and easy to install and maintain, as well as allowing easy lamp replacement. In addition, plastic resin is preferred for use in corrosion situations in the presence of salt spray and in environments with corrosive atmospheres due to the presence of strong inorganic acids. On the other hand, however, the polycarbonate used can lose its transparency characteristics over time, tending towards a yellow colour. In comparison, aluminium and glass have better anti-ageing characteristics, as glass guarantees maximum transparency for many years; • Ex n – simplified: the main feature of this type of protection is the significantly lower cost compared to other protection modes, this is due to the fact that Ex n luminaires are only suitable for zone 2/22.
Equipment is categorised into “intrinsically safe” and “sparking” equipment that can produce sparks, arcs and cause high surface temperatures during normal operation. Therefore, based on this classification, it will be possible to use the Ex nA method for intrinsically safe equipment, the Ex nC method for intrinsically safe equipment and the Ex nR method for restricted breathing.
Luminaires for hazardous areas: a selection guide!
Vision is one of the major negative health effects associated with working in inappropriate lighting conditions. The most common causes are glare caused by excessive light in the environment and the physical and mental effort used to work in low light conditions.
Consequently, inappropriate lighting often leads to inappropriate behaviour: this means that choosing the right lighting is very important, this is even more so in hazardous areas (blast zones) where the need to have adequate lighting to work according to safety standards must be combined with the ability of the instrument to contain a possible explosion.
The characteristics of a lighting fixture are essentially three:
• Protection: lighting equipment is a protected case that contains and protects lamps, lampholders, power switches, terminals.
• Electrical safety: lighting equipment must comply with EN standards with a sufficient degree of protection.
• Lighting functions: refers to the luminous flux emitted by the lamps. It is important to make a lighting calculation specifically for the area to be illuminated.
To create a lighting design, the following concepts need to be considered:
– reflection (when a wave hits a smooth object that is larger than the wave itself, depending on the medium, the wave may be reflected in a different direction); – scattering (occurs when the wavelength of a signal is larger than the pieces of the medium, the signal is reflected from or passes through it due to collisions with other particles). Scattering occurs randomly, and for this reason it differs from reflection and refraction, which change in a regular and deterministic way;
• refraction (deflection of a wave as it passes from one medium to another, the speed of its propagation changes).
When designing a lighting system, it should also be recognised that the efficiency of lighting fixtures decreases over time due to ageing and dust deposits on reflectors and diffusers.
The type of lamp must then be specified in the lighting calculation. For explosion-protected luminaires this means:
– type of lighting (LED or not); – protection mode (Ex d, Ex e, Ex n); – Ex d – flameproof: the main feature is the robust and sturdy construction, which guarantees high reliability for a long time. Ex d luminaires, usually made of aluminium alloy and borosilicate glass, are used in places where, in addition to explosion protection, good mechanical protection of the equipment is required; – Ex e – increased safety: the main feature is that equipment with this method of protection is designed to prevent sparks even in abnormal operating conditions. Ex e luminaires are usually made of plastic resins such as polyesters and polycarbonates, which make them lightweight and easy to install and maintain, as well as allowing easy lamp replacement. In addition, plastic resin is preferred for use in corrosion situations in the presence of salt spray and in environments with corrosive atmospheres due to the presence of strong inorganic acids. On the other hand, however, the polycarbonate used can lose its transparency characteristics over time, tending towards a yellow colour. In comparison, aluminium and glass have better anti-ageing characteristics, as glass guarantees maximum transparency for many years; • Ex n – simplified: the main feature of this type of protection is the significantly lower cost compared to other protection modes, this is due to the fact that Ex n luminaires are only suitable for zone 2/22.
Equipment is categorised into “intrinsically safe” and “sparking” equipment that can produce sparks, arcs and cause high surface temperatures during normal operation. Therefore, based on this classification, it will be possible to use the Ex nA method for intrinsically safe equipment, the Ex nC method for intrinsically safe equipment and the Ex nR method for restricted breathing.
