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Temperature classes

Sunday, 1 January 2012 PDF icon Temperature classes
The temperature class is one of the parameters to consider in order to choose electrical equipment to be installed in places with danger of explosion. Very often this parameter is ignored or underestimated while it’s one of the main features of the safety equipment. An electrical device, addressed to classified areas where there might be danger of explosion due to the presence of gases, vapors, mists or dusts, should be chosen considering that, its maximum surface temperature, must not reach, even in case of failure, the ignition temperature of the hazardous substances present in the atmosphere.

The use of protection methods in zone 0

Thursday, 1 December 2011 PDF icon The use of protection methods in zone 0
Our readers sent us numerous requests regarding the fact that “Ex d”, “Ex e”, “Ex p”, “Ex o”, “Ex q” equipment cannot be used in Zone 0. Therefore, we try to understand what are the normative limits and the reasons for these choices which, as we’ll see, should be reconsidered. There’s a general agreement that the security level of “Ex d”, “Ex e”, “Ex p”, “Ex o”, “Ex q” types of protection is not high enough compared to the probability that an explosive mixture is present in Zone 0. As we know, the areas classification in Europe and, also according to the IEC Standard, is a statistical fact: it compares the average of the number of hours in presence of the explosive mixture in the course of a year and the level of equipment protection.

Ex-proof electrical plant: conduit installation

Tuesday, 1 November 2011 PDF icon Ex-proof electrical plant: conduit installation
Once, all electrical explosion proof plants were made according to the "American" system. This meant that all connections between the various boxes were made through metal pipes containing electrical conductors. Today this system has been replaced thanks to some new Standards: the wiring can be made through armored and un-armored cables while the entry through certified cable glands. This system, of which we discussed in the previous newsletter, is certainly more flexible than the conduit installation, but the second one, however, has some features that make it necessary in certain conditions.

Explosion-proof electrical plant: conduit installation

Saturday, 1 October 2011 PDF icon Explosion-proof electrical plant: conduit installation
The use of cables for electrical equipment connection in potentially explosive atmospheres is now a common practice. Some time ago, explosion-proof materials were connected to each other through steel pipes. Furthermore, the entries into junction boxes presented locking joints which did not allow to a possible explosion to spread through the pipe. The main advantage of this system is that cables are not integrated in rigid tubes, but they go through tunnels like normal cables for industrial plants. Cable entry into explosion proof enclosures is made thanks to the use of special cable glands, which allow both the cable entry directly (British system), either through increased safety enclosures (German system).

EPL: Equipment protection level

Thursday, 1 September 2011 PDF icon EPL: Equipment protection level
As we have seen time after time, hazardous areas for the presence of potentially explosive substances are divided into zones. As reference to gases, vapors or mists, the relevant areas are classified in Zone 0, 1 or 2. The reference standard is the IEC / EN 60079-10-1. As reference to dust, the relevant areas are classified in Zone 20, 21 or 22. The reference standard is the IEC / EN 60079-10-2. As we know, an explosion occurs when an ignition source is in contact with the explosive atmosphere.

The choice of lighting fixtures in classified areas

Friday, 1 July 2011 PDF icon The choice of lighting fixtures in classified areas
Once identified the dangerous areas in a plant, it’s essential to make the correct choice of electrical equipment that can be installed in those areas in order to avoid the danger of an accidental explosion caused by sparks, arcs or overheating. As we’ll see, choice between various types of lighting fixtures is not easy because, besides to the "explosion protection", many other factors come into play.

Ventilation of hazardous areas due to the presence of gas

Wednesday, 1 June 2011 PDF icon Ventilation of hazardous areas due to the presence of gas
In the newsletter of last month, we started talking about the classification of areas with the presence of gases, vapors and mists. In this newsletter we will discuss the effectiveness of ventilation of areas with danger of explosion. We’ll evaluate, also, the provisions of international, European and North America standards.

Classification of hazardous areas due to the presence of gas

Sunday, 1 May 2011 PDF icon Classification of hazardous areas due to the presence of gas
Around the world are followed the recommendations of IEC 60079-10-1 standard, now acknowledge and become the European standard EN 60079-10-1. This standard is relevant to the substances classes of gas, vapors and mists. The EN 60079-10-2 concerns the classification of hazardous areas for the presence of combustible dust. EN 60079-10-1 standard applies to all places in which substances in form of vapor or gas are present and can cause explosive mixtures along with air. Mainly, we’re referring to chemical or petrochemical plants, gas storage, natural gas decompression station, spray booths, fuel store and all those environments, which are the most hazardous environments, where there is the presence of substances that may create an explosive mixture in the form of gas, vapors or mists.

Why an explosion accours

Friday, 1 April 2011 PDF icon Why an explosion accours
In the previous newsletter we discussed about the equipment surface temperature and the possibility of trigger an explosion caused by a hot surface. We have received some requests from readers asking us to investigate why and how an explosion develops. Therefore in this newsletter we will talk about this subject. It’s not so easy to cause an explosion or fire, at least theoretically. Combustion is the rapid transformation of chemical energy into thermal energy. Oxidation, combustion and explosion are chemically exothermic reactions and only differ in reaction speed.

Equipment class temperature

Tuesday, 1 March 2011 PDF icon Equipment class temperature
Recently, we have received some requests from our products users regarding the equipment maximum surface temperature. We realized that there’s no clarity among technicals on what maximum surface temperature means. Let's go step by step. We know that a mixture composed of combustion-comburent requires certain energy to be triggered. This energy is normally provided by a spark or an arc. But, in some cases, the high surface temperature of the equipment in contact with the mixture can trigger it. Therefore, in addition to the minimum ignition energy (MIE), two other chemical and physical properties of the flammable substances must be considered of maximum importance in order to determine their degree of risk and in order to classify them. The two parameters are the Flashpoint and the Ignition Temperature.