Certification intrinsically safe apparatus

Simple intrinsically safe apparatus are not subject to certification (see Section 6.9.5). 

So, the question arises which apparatus shall be certified. The following survey indicates that simple intrinsically safe apparatus do not need a certificate ... 

Not all of the apparatus inserted in an intrinsically safe circuit need to have a certificate. This is based on the fact that, e.g., a terminal, a plug-and-socket connector or even a contact sparking in normal operation will not cause a risk if the electrical circuit is intrinsically safe. 

Certificates are issued not only for individual apparatus. In the same way, an intrinsically safe system e.g. composed of a sensor, cable, power supply and meter amplifier, can be certified. This practice is customary in the Anglo-Saxon countries (United Kingdom, USA). Here, only those apparatus shall be planned and fitted which are listed or specified in the system certificate. So, a high level of safety results for the planner and user since the intrinsically safe system in its entirety (including all components) has been examined. When, however, another component has to be fitted, e.g. due to the nonavailability of a specified device, the system shall be certified again (see Section 6.9.6). 

In certification practice, the so-called intrinsically safe systems are known as well. Deviating from a (single) apparatus which is certified individually, an interconnection of several apparatus is under consideration for an intrinsically safe system, including the connecting cables for the most part. Several intrinsically safe circuits and different categories of these circuits as a part of an intrinsically safe system are permissible. 

This certificate is issued for the electrical apparatus Intrinsically Safe Field Bus System RS 485... 

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. 

As a rule, they are installed in the safe area as associated apparatus. They are used to limit the electrical values for sensors, actuators etc. located in the hazardous area to levels permissible for intrinsic safety. A certificate is required each time. 

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