Hazardous zone classification

DOT HAZARD CLASSIFICATION 6.1 Packing Group I Hazard Zone A DOT LABEL Poison... 

Right-to-know training for any organization that uses potentially hazardous chemicals. Effects of chemical exposure, avoiding exposure, chemical classification, routes of entry, exposure signs and symptoms, and incident response. Part of eight-volume series, Working in the Hazard Zone. ... 

Areas outside the tank in which the conditions listed above do not exist are designated as non-hazardous. Table 7.6 provides an example of a typical hazardous area classification for storage tanks containing a highly flammable solvent (flash point less than 32°C). The procedure for identification of sources of release, determination of the type of hazardous zone and the process for assessment of the extent of the zone are detailed in British Standard 5345 Part 1 and Part 2 [17]. 

Human error Control system reliability Task/HRA or procedural study Power supply, common mode failure Fir explosion Electrical zone classification/ hazardous study/ equipment compliance... 

Carbon monoxide, refrigerated liquid DOT Classification 2.3, Hazard Zone D (Gas poisonous by inhalation)... 

In industry, with the exception of mining, areas that are hazardous, so far as flammable gases and vapours are concerned, are classified according to the probability of occurrence of explosive concentrations of gas or vapour. These classifications, called zones, are as follows ... 

FPN) The Zone 2 classification usually includes locations where volatile flammable liquids or flammable gases or vapors are used, but which would become hazardous only in case of an accident or of some unusual operating condition. 

Classification of hazard areas according to the probability of a flammable concentration of vapour occurring (to BS 5345 Part 1) Zone 0 Area in which an explosive gas-air mixture is continuously present, or present for long periods Zone 1 Area in which an explosive gas-air mixture is likely to occur in normai operation Zone 2 Area in which an explosive gas-air mixture is not likely to occur in normal operation, and if it occurs will exist only for a short time Safe area By implication, an area that is not classified Zone 0, 1 or 2 is deemed to be a non-hazardous or safe area with respect to BS 5345 ... 

Hazardous places are classified in terms of zones (divisions) on the basis of the frequency and duration of the occurrence of an explosive atmosphere (IEC 60079-10 200X, Classification of Hazardous Areas European Standard EN 50281-3 200X, Classification of Areas Where Combustible Dusts Are or May Be Present ). 

Two of the larger LNAPL hydrocarbon occurrences, site No. 1 and 4 (see Ligure 12.23), formerly reinjected coproduced groundwater into generally the same hydros-tratigraphic zone from which it is withdrawn site No. 1 reinjected without treatment into the Gage aquifer, whereas site No. 4 reinjected into the Old Dune Sand aquifer. Because of the presence of dissolved hydrocarbons, notably benzene, in the coproduced water that is typically returned to the aquifer during LNAPL recovery operations, immediate application of the EPA toxicity characteristic rule may result in classification of the reinjected water as disposal of a hazardous waste. This, in turn, would terminate use of UIC Class V wells (which many of these operations currently... 

There are a large number of different methods used for bench-scale assessment of combustion toxicity, and the applicability of test data to lire hazard assessment is not always clear. Obviously, toxic potency data should not be used in isolation but should either be a part of a classification scheme or as part of the input to lire risk and lire safety engineering assessments. It is important that uncertainty or confidence limits should be used with toxic potency data, because they are often relatively large. Fire effluent toxic potency does not have a unique value but is a function of the material and the fire conditions, particularly temperature and oxygen availability in the fire zone, and also the fire environment (enclosure, geometry, and ventilation). To assess the fire hazard, toxic potency data must be relevant to the end use fire situation, and the fire condition, which can be defined using the ISO classification of fire stages. 

Following the historical development of electrical engineering and explosion protection, zone classification was the objective of national standards and installation rules. Most of the leading industrial countries established an installation practice for chemical plants and the oil and gas industry with two or three zones for areas hazardous due to gas- or vapour-air mixtures and two zones for areas with hazardous dust-air mixtures. Apart from this philosophy, the coal mining industry in most countries tends to avoid an area classification and defines only one category of explosion protection ( firedamp-proof ). More recent standards or directives present a three-zone concept for areas endangered by combustible gas- (vapour-, mist-) air mixtures and dust-air mixtures in industrial plants (other than coal mines). 

I Classification system with three zones for areas hazardous due to ... 

II Classification system with three zones for areas hazardous due to combustible gas, vapour or mist (Ha) or due to combustible dust (lib). 

Note The content of Table 2.2(a) describes the traditional classification (IEC standardization not incorporated). Until 1998 the USA and Canada adopted the three-zone concept for areas hazardous due to combustible gases, vapours and mist according to IEC 60079-10, in parallel with the content of Table 2.2(a). 

Part II of Table 2.1 shows a present-day classification system with three zones each for areas hazardous due to combustible gas-air and dust-air mixtures. IEC 61241-3 describes a three-zone concept for areas exposed to hazardous dust-air mixtures, accompanied by IEC 61241-1-1 and IEC 61241-1-2, dealing with specifications for apparatus and selection, installation and maintenance of such apparatus. IEC 60079-10 and EN 60079-10 give some guidelines to calculate the... 

An example of a two-zone concept for areas hazardous due to combustible substances is given in Table 2.2. It shows the traditional classification (in the USA and Canada) into classes and divisions according to the probability of forming an explosive atmosphere. 

Figure 2.1 Classification of an area hazardous due to combustible gases/liquids into zones 0, 1 and 2 [50], The value R is tabulated in Table 2.4 as a function of the filling rate into the tank (liquid with a Hash point <35°C). Dimensions given in metres.

Figure. 2.2 Classification of an area hazardous due to combustible gases/liquids into zones 0, 1 and 2 [50],...

At the present time, IEC 61241-3 combined with IEC 61241-1-1 and with IEC 61241-1-2 as international standards describe construction and testing of electrical apparatus for areas hazardous due to combustible dusts on the basis of a three-zone classification (zones 20,21 and 22). 

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