Explosion protection markings

After the conclusion of the conformity assessment procedure and of the tests perhaps required, the manufacturer issues an EC-declaration of conformity for his product. He affixes the explosion protection marking (Ex marking) to the product and if the product fulfills the requirements of other applicable European directives he affixes a CE marking to the product as well. 

This marking system correlates the adequate zone on the explosion protected apparatus with traditional data, e.g. group, type of protection and temperature class (see Chapter 5). 

Table 3.1 Types of explosion protection and marking according to VDE 0170/0171/1969-01...

Figure 3.1 (a) Ex mark for explosion protected electrical apparatus complying with... 

Explosion protected electrical equipment for zone 1 (Group II, category 2 G) and the classical firedamp-proof apparatus for coal mines (Group I, category M2) are covered by the B module (EC-type examination) and by the C module (conformity to type) or the E module (product quality assurance). Alternatively, with respect to the B module, the notified body issues an EC-type examination certificate (in German EG-Baumusterpriifbescheinigung), whose marking mainly includes ... 

It shall be emphasized that all markings described in this chapter are related to explosion protection only and shall be considered as an additional marking to that given in the standards for non-explosion protected apparatus, e.g. the manufacturer s name or his trademark, type code and rated power/ voltage/current/speed/torque, serial number etc. 

IEC and EN Standards ask for marking the type of protection as an abbreviation completed by the classification scheme (temperature class, explosion group) as described in the previous chapter. Table 5.1 gives a survey of the types of explosion protection and their abbreviations. Table 5.2 summarizes the IEC and EN marking code. 

Table 5.2 Marking of explosion protected apparatus according to IEC and EN Standards...

In the following, some examples for marking of explosion protected apparatus are given (the manufacturing companies are fictitious). It is assumed that these apparatuses have been manufactured, type tested and certified under the old article 100 directives (Table 3.6), applicable until 2003-06-30. 

For explosion protected electrical equipment manufactured, type tested, certified and commissioned under the ATEX 100a Directive, the marking described in Table 5.2 shall be added by the marking code given in Table 5.3. The Ex in a hexagon has been taken from the old article 100 directives, whereas the B, C, D or E marks for the generation of Harmonized Norms have been deleted. 

Table 5.3 Marking of explosion protected apparatus according to ATEX 100a Directive (94/9/EC) (this is additional to the EN marking as in Table 5.2)...

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 marking of such s -apparatus has been (Sch)s for mining equipment and (Ex)s G... for explosion protected apparatus (suitable for zone 1 applications). In many cases, protection techniques, which are covered by their own standards today, e.g. encapsulation - m - or static pressurization (as a part of pressurization - p - ), have entered the field of explosion protection as s -apparatus [17]. 

The Ex marking for protective systems and equipment of the category 1 is normally determined by the Notified Body according to the result of an EC-type examination. The Ex marking for non-electrical equipment of the categories 2 or 3, for example explosion-protected vacuum pumps, is determined by the manufacturer or by the supplier of this equipment. 

Lighting fixtures installed in Division 1 areas must be explosion-proof and marked to indicate the maximum wattage of allowable lamps. Alsn, they must be protected against physical damage by a suitable guard im liy location. 

The stocks should always be used in the sequence of the date of manufacture which is marked on the cases. This eliminates any accumulation of old stocks and helps to make sure that the materials are in best condition. The contents should be used as early as possible once a case is opened. If all explosive is not used on the same day, the original packing should be folded over and the case closed so as to give maximum possible protection to the contents. 

It has been shown above that there is a marked effect of the charge of the thiol and its efficiency to protect against OH attack but also to repair DNA damage (for thiol binding to DNA see Smoluk et al. 1986). An extension to GSH-deficient cells in combination with the oxygen explosion technique allowed to determine the rate constants of various thiols with radiation-induced DNA damage (Table 12.21 Prise et al. 1995). 

Classification and marking of intrinsically safe apparatus concerning explosion groups (I, IIA, IIB, IIC) and temperature classes (T1-T6) are organized in the same way as for, e.g., flameproof enclosure - d (see Tables 4.1 and 4.2, Chapter 4, and Chapter 5 for marking). Some special features, however, which are of importance for type of protection intrinsic safety - i only, will be explained in the following. 

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. 

Shestakov 1 ) introduced an original method of protecting ammonium nitrate which consists in mixing ammonium nitrate with Fe2(S04)j (0.5%) and fatty acids (stearic, palmitic acid) (0.25%). A tliin layer of ferric stearate or pal-mitate is fonned on the surface of crystals of ammonium nitrate. It is now customary to use 0.3—0.4% fatty acids and 0.07% iron salts. Part of the fatty acids can be replaced by paraffins. Explosives containing fatty acids and iron salts are marked with symbol Zh V. 

In the UK, the type testing and certification work has been carried out by the Electrical Equipment Certification Services (EECS), which is part of HSE, and by SIRA Test and Certification Ltd. The Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres Regulations 1996 will change this, because they introduce a legal requirement for compliance with the Essential Health and Safety Requirements (EHSRs) and the application of the CE mark using the applicable conformity assessment procedures, which may involve the participation of a notified body. This is a complicated area but, in summary ... 

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