Marking intrinsically safe apparatus

If an intrinsically safe apparatus is intended for operating on its own (installed in zone 1, not including non-intrinsically safe circuits), the marking... 

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. 

Moreover, the marking of intrinsically safe apparatus contains further information as follows ... 

For each interconnection of an intrinsically safe circuit with an associated apparatus a proof of intrinsic safety - i shall be performed on the basis of the safety-related maximum values. As far as the simple standard design given in this example (Fig. 6.218) is concerned, it is assumed that the associated apparatus only - the Ex i-isolator - can feed electrical power into the intrinsically safe circuit. Therefore the safety-related parameters are marked as out-parameters with the subscript o. On the other side, the intrinsically safe apparatus may consume electrical power only. Its values are marked as in-parameters, subscript i. ... 

If the apparatus with intrinsically safe circuits is installed outside a hazardous area, e.g. in a control room in a chemical plant, the marking inserts Ex or EEx and the type of protection in brackets ... 

In this case the apparatus is not subjected to the temperature classification T1...T6 because of its safe environment. For Group II intrinsically safe circuits, the MESG or MIC grouping IIA/IIB/IIC shall be marked according to the relevant standards (IEC 60079-11, EN 50020). 

Table 6.45 Marking and application of intrinsically safe and associated apparatus...

A system specified to such a degree is intrinsically safe with a maximum of 32 field devices and two terminations. The proof of intrinsic safety is thereby reduced to a list of the apparatus installed and their certificate. The marking includes FISCO and the type of apparatus, e.g. power supply, field device, termination. 

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