Explosion protection range

Depending upon the design criteria of the installed suppression system, an unsuppressed explosion overpressure of around 7 to 10 bar is reduced to a suppressed reduced explosion overpressure which lies in the range of Fred,max = 0-2 to 1 bar. Thus, vessels need to be explosion resistant for an overpressure of maximum 1 bar (ISO Standard 6184/4, Explosion Protection Systems Paii 4 Determination of Efficacy of Explosion Suppression Systems, Geneva, 1985). 

Table 3.11 lists the notified bodies according to Directive 94/9/EC. It is noteworthy that competence and responsibility of a notified body may be restricted to certain types of explosion protected equipment (e.g. non-electrical apparatus only), to one group only (e.g. Group II) or to a selection of modules, e.g. to quality assurance related modules. The notified bodies are not obligated to cover the complete field of explosion protection. Nevertheless, some notified bodies cover the total range and can provide a single-stop-procedure to their clients. 

To start with the latter Figs 6.1-6.8 give an impression of environmental conditions at the place of duty for modem explosion protected equipment, and at the same time, they may anticipate its efficiency and power as well as its broad range of application. 

Apparatus grouping and temperature classification are described in Chapter 4, especially in Table 4.1 Part A and Table 4.2 Part A for EN and IEC specifications. As a general rule, the ambient temperature (in service) for explosion protected electrical apparatus is limited to the range from 20°C to +40°C. Deviating ambient temperature ranges shall be indicated, e.g. -30°C = Tamb =s +60°C, or the apparatus shall be marked with the symbol X, which indicates special conditions in general. 

The main field of application of oil immersion - o is the explosion protection of Group II transformers in the high power range (up to some 1000 kVA). The terminal compartments often comply with increased safety -e or plug and socket connectors (in e ) are used in the high voltage range (see Section 6.7). 

Above all, HART has succeeded in the field of process engineering, with feasibilities, e.g., to remotely change the meter range of an instrument or to interrogate diagnostic data. So, numerous products are available in an explosion protected design. A number of them are certified as intrinsically safe apparatus. 

The effective intrinsically safe voltage is in the range of approx. 8-10 V. So, for many applications that require an increased voltage level a DC/DC convertor has to be inserted. Of course, this DC/DC convertor in an intrinsically safe circuit shall be explosion protected itself accordingly. This increases the technical expenditure required. 

The definition is Atmospheric conditions exist if the absolute pressure-range is between 0.8 and 1.1 bar and the temperature is in the range from -20 to -1-60 °C. The directives to the explosion protection do not cover... 

The Regulations provide a range of means for assessing conformity. However, as far as electrical equipment is concerned, conformity assessment through a notified body will be the norm, following much the same EC type examination processes and procedures that have been used in the past. There are, however, additional requirements for product quality control and third party audits. In the UK, the Electrical Equipment Certification Service (EECS) and SIRA Test and Certification Ltd already provide conformity assessment services, basing their assessments on the harmonised standards that already exist for explosion-protected electrical equipment the main standards are identified in Chapter 15. 

Having carried out an area classification exercise, the electrical equipment to be installed in the area must then be selected for its explosion protection properties. There is a range of options to choose from, with a variety of protection techniques employed. Each of the techniques, bar one, is described in detail in a European harmonised standard and is allocated a designation letter, mainly for ease of labelling. The following text summarises each of the techniques, and identifies its letter designation and appropriate construction standard. 

The autoignition temperature is the minimum temperature required for self-sustained combustion in the absence of an external ignition source. The value depends on specified test conditions. Tht flammable (explosive) limits specify the range of concentration of the vapor in air (in percent by volume) for which a flame can propagate. Below the lower flammable limit, the gas mixture is too lean to burn above the flammable limit, the mixture is too rich. Additional compounds can be found in National Fire Protection Association, National Fire Protection Handbook, 14th ed., 1991. 

Department of Defense Explosives Safety Board has approved five groups of suppressive shields for protection of munitions production operations in US Army Ammunition Plants. Safety approved shields encompass seven different designs which range in size from a two foot diameter steel shell (Shield Group 6) to a ten foot diameter steel cylinder (Shield Group 3). 

Today, almost everyone works or lives with chemicals and chemical prodncts. Over the centuries man has lived in a chemical age, but especially so during the past several decades. Many of the chemical substances can have deleterious effects on animals, humans, and the environment. These substances are capable of causing physical hazards (e.g., lire or explosion) or health hazards (such as systemic toxicity and chemical bums). Improper use of chemical substances causes a wide range of health hazards. It is the responsibility of the user to evaluate each chemical substance and know its potential to cause adverse health effects and pose physical hazards, such as flammability in the workplace. The manufacturers, importers, and distributors of different chemical substances must be sure that containers of hazardous chemicals leaving the workplace are properly labeled with the identity of the chemical and appropriate hazard warnings. In the workplace, each container must be marked with the identity of hazardous chemicals contained in it and must show hazard warnings appropriate for employee protection. 

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