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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.

Ex p way of protection

Tuesday, 1 February 2011 PDF icon Ex p way of protection
As consequence of last month's newsletter, we received some requests regarding the Ex p type of protection and we are happy to satisfy our readers expectations. The internal overpressure protection mode is based on the concept of segregation. Basically, it prevents the penetration of the explosive atmosphere in enclosures containing sparkling equipment through the injection of clean air, which creates an excess an overpressure, preventing gas from coming into contact with the trigger factor.

Main protection methods

Saturday, 1 January 2011 PDF icon Main protection methods
We begin this new year analyzing some of the main ways of protection used in systems installed in areas with potentially explosive atmosphere for the presence of gas. Relating with the three main protection techniques (containment, prevention and segregation), exist many others ways to apply the basic principle of the method. Each method is specific to certain applications and impossible to apply to others. Over the time, unspecific techniques have been attempts to adopt to certain applications, leading to disastrous consequences and, often, major damage. In recent years, standards have been heavily modified, and, even if existing, have been amended to be harmonized with international standards IECEx.

International Standard Ex n

Wednesday, 1 December 2010 PDF icon International Standard Ex n
In Zone 2 the probability of presence of explosive atmosphere is between 30″ and one hour during a year, and the risk level is very low. Between 70% and 80% of the hazardous areas inside a plant can be classified as Zone 2, and it is essential that the designer duly knows the protection type of the electrical equipment installable in such areas. The use of oversized equipment, in fact, could involve a huge waste of money and no advantages in terms of safety. This method of protection has been developed in the United Kingdom many years ago to be used in safety condition in Zone 2 reducing the costs of traditional equipment in Ex “d” or Ex “e” protection. Ex “n” protection method is applied to the equipment having the features described on the International standard IEC 60079-15:2010.

Installations in hazardous areas for the presence of combustible dust

Monday, 1 November 2010 PDF icon Installations in hazardous areas for the presence of combustible dust
In the last two newsletters, we analyzed the risks arising from the presence of combustible dust and, subsequently, we considered the method of classification of hazardous areas. In this newsletter, we will describe what types of protection can be used and how the installations are performed. In order to design an electrical system respecting the principles of safety against explosion in hazardous areas for the presence of combustible dust, the new EN 60079-14-2 standard is the reference. This standard is part of the whole new standard group resulting directly from IEC requirements which replaced the EN 50281 series standards.

Classification of areas with presence of dusts

Friday, 1 October 2010 PDF icon Classification of areas with presence of dusts
In the last newsletter, we have analyzed the danger of explosion due to the presence of combustible dust. In this newsletter, we will take a look to the classification of hazardous areas due to the presence of combustible dust, according to the provisions of the new rules which, as we shall see, come directly from the IEC international standards acquired by CENELEC and by the national regulation. The danger of explosion, as we saw in previous newsletters, can occur not only in places where gas, vapors or mists are present and where are normally used electrical installations that follow European regulations in force for over thirty years. It can occur also in plants where dust are machined during the normal operation and that might create a dangerous atmosphere, which could cause an explosion.

September, vintage time

Wednesday, 1 September 2010 PDF icon September, vintage time
September has come It's vintage time, the crops have been harvested in recent months and the barns and silos are now full of wheat and flour. Man has always lived with food powders, but only in the recent few years has understood what is the danger of an incorrect treatment in the handling and storage of these products. The devastating explosions, which periodically occur in rooms where large quantities of combustible dusts are stocked, have attracted attention and both the causes and the means to avoid them were subject of important studies. It’s not a modern phenomenon; in more than 200 years can be reported "explosions of dust”. The first recognized and recorded explosion of dust occurred in a flour warehouse in Turin in 1785. At that time, the windmills used since the mid-14th century for grinding cereals were gradually replaced by steam turbines, more efficient but also more dangerous. Another great explosion, occurred in Germany in 1887 in the New Mills of Weser Hameln, caused the death of thirty people and injured a large number.