Important Aspects when Choosing Explosion-proof Luminaires
In recent years, LED lighting has become more popular in Russia. The main advantages of LED-technology are cost efficiency, environmental friendliness and longer lifespan compared with standard light sources. In addition, LED luminaires are best suited to illuminate premises with dangerous conditions. Explosion-proof LED luminaires forma sector on their own and have unique performance characteristics. When choosing such lighting equipment one must take into account a number of features.
Before making your choice on a particular product, you need to understand what Ex marking means. It contains five elements (for example, 1 Ex d IIB T5). Each element has some information about the characteristics of the luminaire.
Level of explosion protection
In the first place there is a figure indicating the level of explosion protection (in our example it is 1), "1" stands for explosion-proof electrical equipment, i.e. explosion protection of the luminaire is ensured at the standard, and the emergency mode of operation. Figure "2" corresponds to the increased reliability against explosion, but only in the standard operation mode without ensuring explosion protection in emergency operation. Finally, "0" indicates especially explosion-proof equipment, in which special measures and means of protection against explosion are used.
Explosion protection mark
This item is a mark of compliance with the standard of explosion protection - Ex.
Type of explosion protection
The third item is the character that determines the type of explosion protection in the luminaires (in our example it is d). “d” means flameproof enclosure - this is one of the best ways to ensure explosion protection.
Other types of explosion protection:
- “e” - protection using additional measures against the possibility of exceeding the permissible temperature and the occurrence of arc-type discharges;
- “I” — intrinsically safe circuit;
- “m” — encapsulation (also possible options are “ma”, “mb”, “mc” specifying the type of compound).
To specify more detailed information about the explosion protection of their luminaires manufacturers use several characters. For example, “m d” indicates sealing with compound while simultaneously using a flameproof enclosure, which greatly enhances the explosion protection of the device.
Group of explosion-protected equipment
In fourth place there is a character giving an idea of the lighting equipment group. There are the following groups:
- I — mine explosion-proof electrical equipment intended for use in underground mines, pits and their surface facilities hazardous with firedamp and/or combustible dust;
- II — explosion-proof electrical equipment for indoor and outdoor installation designed for a potentially explosive environment, except for mines, pits and their surface facilities, hazardous with firedamp and/or combustible dust.
In most cases, the equipment of second group is used. In our example a reference to a group of equipment is accompanied by the letter B (IIBC). This is an indication to one of three subgroups - A, B and C, which differ by the categories of hazardous environment, where the luminaires can be used. "B" is the most common category, indicating that the luminaires may be used in the atmosphere, which contains compounds of nitrogen, oxygen, mixtures (coke-oven gas), sulphur, and halogens.
In fifth place there is a character specifying the temperature class. It determines the highest temperature of the luminaire enclosure, where T1 assumes +450°C, and T6 - +80°C. The larger the class the less is the possible maximum temperature of the luminaire surface and the lower is the explosion probability, and the wider is the area of application of the luminaire .
It should be emphasized that this information about marking applies only to one of the two components of explosion protection – explosion protection of devices operating in environments that are dangerous in relation to gas. But the air in addition to explosive gas mixtures may contain combustible dust. Therefore, the complete marking of luminaire explosion protection is divided into two components - by gas and by dust.
As an example of detailed marking let’s consider the marking of AtomSvet explosion-proof luminaires (Fig. 1) designed for difficult and extra difficult operating conditions :
- 1Ex mb d IIB T5 Gb;
- Ex tb IIIC Db.
The first line is gas explosion protection marking. It informs us that the device is explosion-proof and has the first level of protection. Its type of protection – “mb d” - means that the unit is sealed with compound, as well as protected with a flameproof enclosure. IIB and T5 character decryption is given above, and the Gb character is an additional designation of protection level, which indicates that the device intended for use in a potentially explosive environment is not a source of ignition in normal operation or in case of assumed malfunctions, and the probability of its ignition from the moment an explosive atmosphere is present until the electrical power is turned off is low.
The second line is dust explosion protection marking. It tells us that this is an explosion-proof luminaire (Ex), in which the protection is ensured by enclosure (tb). IIIC means it can be used in environments containing conductive dust (it is the most stringent requirements for dusty environments). Finally, Db informs us about the level of dust protection, in this case that it is high, and the equipment itself is not a source of ignition in normal operation or in case of assumed malfunctions.
So marking of explosion protection can be seen as a kind of "story" about what measures are necessary to resort in order to ensure operation of the device in the most dangerous conditions.
Degree of protection from environmental impact - IP.
Another factor, which deserves attention, is the degree of protection of the flameproof luminaire against dust and moisture (IP). This characteristic is not directly related to protection parameters, but still it is the most important characteristic.
When choosing a luminaire, remember that if the level of protection is below IP65, it will attract extra costs during operation - cleaning from dust, moisture and so on. Cleaning will need to carried out at least three times a year, which is about 650 rubles per luminaire, or about 20,000 rubles of extra cost for ten years, is the lifetime of a quality luminaire with IP65 degree and higher.
AtomSvet explosion-proof luminaires have IP67 degree of protection. "6" is a complete protection against ingress of dust, "7" means the device is not only protected from even the heaviest rain, but also can withstand short-term immersion to a depth of 1 m, which is an additional guarantee of its high degree of moisture protection and it has a long lifespan, typical of LED luminaires.
More information about AtomSvet products will be available at Interlight-2014 exhibition (Forum hall, F.D 100 booth).
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