The processing of the agri-food industry often involves the need for treatments in sterile environments and the movement of materials stored in the silos with consequent emission of dust into the environment that lead to classify these areas as potentially explosive and therefore related to ATEX regulations.
In particular, explosive dusts may form during the transport and storage of cereals; if these dusts are sucked and separated by filters, an explosive atmosphere (ATEX) can form in the filter.
The drying, grinding and refining of agri-food material also produces an explosion risk.
These areas require safe and robust Ex components that can withstand a wide variety of cleaning agents.
Cereal storage silos are deposits where food industry products (such as wheat, grain, rice or similar) are stored. All those products are made of coal, hydrogen, nitrogen, sulfur, oxygen etc., therefore they are combustible and may cause fire and explosions. Dusts generated by the grinding of those cereals, due to their low specific weight, may remain hanging in the air for long periods originating explosive atmospheres.
In intrinsically safe systems, associated equipment plays a key role in the safety of the system. Their positioning can be foreseen outside the hazardous area or, alternatively, in explosion-proof enclosures that can provide them with adequate protection for installation in Zone 1.
In an intrinsically safe electrical system, the electrical devices that can be installed in the hazardous area can be simple constructions or constructions certified as intrinsically safe. The first can be passive components, components with well-defined stored energy or with limited energy generation. The latter are more complex ...
In installations with areas classified as being at risk of explosive atmospheres, the 'Ex i' is the protection mode with the most certificates active on the IECEx website. The intrinsically safe method of protection is based on the principle of eliminating the ignition by limiting the energy in the danger zone.
Combined protection methods represent a fundamental approach to guarantee the safety of electrical equipment in areas classified for the presence of potentially explosive atmospheres. Their application makes it possible to satisfy different construction and operational needs, combining the advantages of the various protection methods available.
Metallic materials are not subject to the typical problems of plastic materials such as aging and resistance to UV rays, but rather can become ignition sources themselves. This is why the legislation pays particular attention to the parts that act as housing.
The main materials of non-metallic origin in electrical equipment are plastic and elastomeric materials. Their enemies are aging, ultraviolet rays and electrostatic charges
Street lighting in areas at risk of explosion must minimize glare phenomena and have a luminous footprint on the ground characterized by homogeneous illumination without large peaks and shadow areas. To obtain a better result, the light emitted must have a greater luminous intensity on the sides rather than on the symmetry plane of the device. With the advent of LED technology this need is met by the use of so-called "secondary optics".
In this article, we will delve into the connection of 'Ex db' and 'Ex eb' electric motors with 'Ex eb' junction boxes to the power line using electrical connection accessories, i.e. adapters, sealing fittings, cable glands and flexible tubes. Being able to use an Ex-eb cable gland is not at all negligible from an economic point of view. The time saving during installation compared to installing a sealing fitting or an Ex-db cable gland is considerable.
Increased safety electric motors or flameproof electric motors with increased safety connection box have been on the market for many years. Let's see the connection of Ex- db electric motors with Ex- db connection box to the power line by using some examples of system applications
In the design and use of electrical devices we must manage conductive parts with different electrical potential, with even very high voltage differences. The risk of formation of electric arcs in the air and creeping currents on the surface of the insulation material must be considered. To limit these phenomena, during the design phase we intervene on the distances between exposed conductive parts.
There are a series of physical phenomena which concern all electrical devices in general, but which assume great importance in equipment for areas classified as hazardous for potentially explosive atmospheres. One of these phenomena is called "breathing".
In a world where the installation speed, the overall site security and the installation and maintenance costs are increasingly important, the use of specific connectors as FlowEx series can find wide application.
The components used in contexts at risk of forming an explosive atmosphere are made with particular materials. This is particularly true in the case of plastic materials. In contexts designed to form insulation between conductors, the materials used are selected from among those that express better tracking resistance.
Among the equipment suitable for use in explosive atmospheres with an EPL Gb, those with increased safety are undoubtedly the most similar to an industrial standard product. Over the years this method of protection has spread in junction boxes and in particular in lighting. In general, the lighter and more portable constructions of the increased safety products have been appreciated by plant engineers.
In Europe, the process of harmonization of regulations has opened a new phase in technological development and, to all intents and purposes, can be considered a success of the process of integration of the European Union. The birth of the EEC, the establishment of the CENELEC and CEN technical committees, the first ATEX 94/9/EC regulation and then the new ATEX 2014/34/EU regulation... let's retrace together the last steps that led to the present day have a harmonized regulatory framework at Eu
Often the meaning of the supplementary letter is little known, misunderstood and misinterpreted. Not understanding the difference between component and equipment or thinking that a certificate with the final "X" is a sort of B-series certificate with strong limitations on the use of the equipment is completely anachronistic today.
In the United States, the path that led to the development of equipment suitable for use in areas at risk of explosion has followed an almost parallel path to Europe, addressing the issue first in the mining industry and then extending it to electrical devices in the NEC. The use of still current techniques demonstrates how much the more traditional methods of protection can boast a history of reliability and safety spanning more than a century.
The systems are mainly divided into systems with metal protective conduits and cable systems. The various devices require cable entries suitable for the type of protection used. The type of cable entry may appear to be a mere theoretical argument, but it has a decisive impact on the safety level of the system.
The most used entry systems are: entry with sealing fitting, cable entry with Ex barrier cable gland, cable entry with Ex cable gland with sealing ring. When we talk about electrical systems with electrical cable installation, entries are made using a cable gland, which can be of two types: barrier or with sealing ring.
In sites where there is a risk of the formation of an explosive atmosphere, we often find the electrical conduit in a metal protective tube (also called conduit conduit). Although it has recently been joined by more versatile armored and non-armored cable systems, with cable gland entry, its use is recommended in plants where production or use and maintenance activities can present dangerous situations for the integrity of the cables.
Today we define the methods of protection as techniques that are made available to us by harmonized standards, to satisfy the Essential Health and Safety Requirements. It appears clear how the first decades of the twentieth century proved to be fundamental for the development of the techniques underlying the current methods of protection.
Sealing fittings are often considered only as secondary or minor components, but the safety of an installation with metal electrical conduits and related explosion-proof enclosures depends on them. The main function of a conduit sealing fitting is to prevent the propagation of an explosion from the inside of the ‘Ex d’ flameproof enclosure to the outside.
Nowadays, the classification in an area at risk of explosion concerns many sectors of the industry and includes the use of the most diverse equipment. This great variety of devices and applications must not make us forget that the origin of explosion risk containment techniques lies down there, in those dark mines where it all began.
Explosion-proof joints are one of the basic aspects of the protection offered by an equipment or an explosion-proof enclosure. For this reason, understanding their function is a prerequisite for the correct use and the proper maintenance of all electrical devices that adopt this type of protection.
The 'Ex d' type of protection, now referred to as 'Ex db', is based on a simple theoretical concept: containment by means of a sturdy casing and flame retardancy. Its success is due to this simplicity, it is in fact one of the first methods of protection developed in the mining industry and still today it is one of the most widespread in areas classified for potentially explosive atmospheres.
A fundamental principle of the ATEX Directive 2014/34 / EU, shared with the other Union directives, is the limitation of legislative harmonization to essential health and safety requirements of public interest. Within this legislative harmonization, a role of primary importance is played by the harmonized technical legislation and the concept of the state of the art. The ATEX Directive refers to this concept as a requirement requested of manufacturers.
ATEX device's manufacturers use different types of protection to achieve a certain EPL. These methods of protection are constantly evolving both technical and regulatory. In any case, the most used are those that have established themselves historically.
Each equipment that must be installed in an ATEX classified area must have a certain level of protection, indicated in the legislation with the acronym EPL (Equipment protection Level). The level of protection is obtained by applying technical regulations that define the protection methods. There are many ways of protection, some have a historical origin, others are more recent...
1. Introduction In the food industry world, there are many problems related to the hygienic safety of production stations along the...
1. Preface Dust explosions can occur in any activity in which solid materials are treated and finely divided (metals, organic substances,...
