Features of the use of technical security equipment in explosive areas.

Features of the use of technical security equipment in explosive areas.

Given the ever-growing terrorist threat, the task of protecting explosive premises is becoming increasingly important. At the same time, the number of facilities that have explosive premises (gas boiler houses, warehouses for fuels and lubricants, paints and varnishes, etc.) includes not only oil and gas enterprises, chemical, mining and metalworking industries, but also gas stations, pharmaceutical, woodworking, confectionery, flour mills and even hospitals equipped with oxygen stations. However, when choosing technical means for protecting explosive premises, designers are faced with the fact that the range of such equipment is currently extremely small.

This is due to the fact that special requirements are imposed on security equipment intended for installation in explosive premises. In addition to its functional purpose, such equipment should in no case itself become a source of explosion, i.e., it must be explosion-proof. Requirements for explosion-proof equipment are established by GOST R 51330 «Explosion-proof electrical equipment» and Chapter 7.3 of the Electrical Installation Rules (PUE). In general, GOST and PUE comply with the requirements of the International Electrotechnical Commission (IEC) and do not contradict current European standards.

According to these guidelines, equipment permitted for use in explosive areas must have special marking. The type of explosion protection marking may be, for example, the following: 1 Ex ib IIC T6. The first digit of the marking indicates the explosion protection level, for example, 1 corresponds to the level of «explosion-proof electrical equipment», i.e. equipment in which explosion protection is ensured both in normal operation and in the event of recognized probable damage. «Ex» is the accepted designation of explosion protection. The letter following it indicates the type of explosion protection. Of the nine possible types of explosion protection in fire alarm systems, as a rule, only two are used: d — «explosion-proof enclosure» and i — «intrinsically safe electrical circuit». Roman numerals indicate the category of explosive mixture permitted for a given equipment: digit II corresponds to all industrial mixtures, except for mine gases. In addition, equipment of group II, having explosion protection types «explosion-proof enclosure» or «intrinsically safe electrical circuit», is divided into three subgroups designated by the letters A, B and C. And, finally, the letter T, accompanied by numbers from 1 to 6, means the temperature class of permitted groups of explosive mixtures. An explosion-proof enclosure ensures that a possible explosion or heated gases do not spread beyond the enclosure into the external environment. Reinforced metal cases are usually used as enclosures, which significantly increase the dimensions and weight of the equipment. Equipment in the «explosion-proof enclosure» design can be connected to conventional control panels (CIP), but the signaling and power loops must be laid in metal cable ducts, which greatly complicates installation.

An intrinsically safe electrical circuit limits the energy entering the explosion-hazardous area to a safe level, at which a spark will not occur even in the event of a short circuit or break, accompanied by the appearance of open-circuit voltage on the broken contacts. In addition, intrinsically safe circuits prevent the accumulation of energy inside the equipment and thus eliminate the possibility of heating its internal components to a dangerous temperature. The formation of an intrinsically safe circuit in an OPS is implemented using safety barriers. These barriers can be made either as separate devices for installation between conventional control panels and intrinsically safe loops, or can simply be part of the control panel, which in this case must be marked as explosion-proof equipment. Intrinsically safe and intrinsically hazardous circuits inside such a device must be reliably separated. The main advantage of an intrinsically safe electrical circuit is that equipment with this type of explosion protection will not generate a spark or heat up to an explosive temperature even in the event of any malfunctions. Due to this, equipment maintenance is simplified and the consequences of technical personnel errors are minimized. The cost of installing such an alarm system is practically no different from the cost of installing a conventional fire alarm system.

The advantage of control panels that include safety barriers is that the consumer in this case gets rid of the problem of correctly connecting external units or spark protection devices, but the problem of selecting detectors according to spark-proof parameters still remains. In addition, when using detectors that require a separate power supply, the question arises about the need for an additional spark-proof power source, also coordinated according to spark-proof parameters.

When constructing an OPS in explosion-hazardous areas, it is not enough to limit yourself to the selection of explosion-proof control and monitoring devices, detectors and barriers. It is also necessary to take into account the total capacity and inductance of the loop as a whole, which are determined not only by the detectors' own Li and Ci, but also by the parameters of the cable route, i.e. the linear values ​​of L and C of a specific cable type and its length. These values ​​​​must not exceed the maximum values ​​​​L0 and C0 specified on the body and in the passport of the control panel or spark protection barrier. It is also necessary that the values ​​​​of voltages (U0) and currents (I0), which can occur in intrinsically safe circuits of the control panel or spark protection barriers, do not exceed the maximum permissible Ui and Ii for devices in an intrinsically safe loop.

Organization of technical security of explosive objects, undoubtedly, should be the most important area of ​​​​activity of both state and departmental structures. Based on the specialized equipment available today, it is possible to organize full-fledged protection of explosive premises in accordance with all the requirements of current regulatory documents. The use of explosion-proof security devices can significantly reduce the likelihood of serious accidents, environmental and man-made disasters, but most importantly — it can reduce the threat to human life.