1               About the Ex-I Calculation Wizard

Frequently there are areas in production plants, in which highly inflammable or explosive materials or mixtures of materials are present. On the other hand process data has to be measured and the media flows have to be moved and controlled in these areas. The sensors and actuators used in this area are often electrically driven. In the process, the supply of energy is required to operate these components.

The supplied amount of energy must not exceed a certain value so that no ignition or explosion of the mixtures of the material can take place. The circuits must be intrinsically safe so that neither in the normal operation nor in case of an error an ignitable spark can be produced during opening or closing the circuit or in case of short circuits to ground.

Apart from spark ignition, the heat ignition caused by hot surfaces must also be avoided. For this purpose, it is necessary to ensure for the normal operation and in case of errors, that for the maximum currents, voltages and power of the intrinsic-safe circuit no impermissibly high surface temperatures occur at equipment, components and cables which are located in the potentially explosive area.

To comply with these criteria, not only the individual equipment included in the intrinsic safe circuit but the complete interconnection and the interaction of the entire equipment involved including the connection cables have to be considered. The standards DIN EN 60079-14 require a verification of intrinsic safety for intrinsic safe circuits; it makes sense that this verification is created already in the planning and projecting phase and that it includes the selection of appropriate equipment and the check of the selected interconnections.

The measuring and control circuits for the hazardous areas are included in the Engineering Base projects. Using the Ex-i Calculation Wizard the intrinsic safety of functions in the hazardous areas can be calculated and the required documentations can be created automatically.