You are here

Electronic grounding system in hazardous areas

Sunday, 1 April 2012 PDF icon Electronic grounding system in hazardous areas

Spring has begun and rains come too. With them the first storms appear. Who can say that have never been fascinated by the power of lightning? Since ancient times, thunder and lightning evoked fear and respect in men who believed that these phenomena were directly dependent on gods. Whereas, lightning is a visible phenomenon of the potential difference which is formed between a cloud and earth. It represents the moment of discharge to the ground of the enormous energy that has been formed. Since the invention of the lightning rod by Benjamin Franklin, all the high buildings, such as towers and steeples, have it, just to create a privileged path for the electrical discharge which goes into the ground preventing damage to buildings, people and animals. Then, if lightning is an important and dangerous phenomenon, why during the design and construction of a plant built in areas with potentially explosive atmosphere, the grounding system is not often considered such important for safety and security?

Electrical installations in hazardous areas

Thursday, 1 March 2012 PDF icon Electrical installations in hazardous areas: places for batteries recharge
Industrial activities which use rechargeable batteries are more and more. Batteries usually used are with nickel-cadmium or lead and are divided into two groups: Traction batteries, mainly used in forklifts, machinery for the cleaning of large rooms etc... Stationary Batteries which are used for auxiliary services of power plants, telephone exchange or places where it’s necessary to keep in operation machineries also in case of power blackout.

Obstruction lighting fixtures

Wednesday, 1 February 2012 PDF icon Obstruction lighting fixtures
Any construction, such as skyscrapers, towers, equipment plant tours, pylons etc. that could represent an obstacle to air navigation, even if located outside the airport fence, must be provided with adequate warning lights. Air traffic safety is regulated by ICAO (International Civil Aviation Organization). ICAO classifies airports into ten categories and, for each category of airport, defines an area, including in so-called "area of obstacles delimitation" that extends to a predetermined distance from the airport itself. Any object, which rises above the surfaces of obstacles delimitation and cannot be removed, becomes an obstacle to air navigation and must be properly signaled.

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.