Explosion Protection Products

As defined in the 60079-11 standard, an intrinsically safe circuit is a circuit in which any spark or any thermal effect produced under specific conditions, which include normal operation and specified fault conditions, is not capable of causing ignition of a given explosive atmosphere.
Intrinsically safe electrical equipment is electrical equipment in which all the circuits are intrinsically safe.
In practice, the concept of intrinsic safety is based on ensuring that the energy released from the circuit as a result of defined faults (including short circuits and breaks) in the form of an electric spark does not lead to the ignition of a specified explosive atmosphere.

According to the definition in the 60079-7 standard, increased safety is a type of protection applied to electrical equipment or an Ex Component in which additional measures are applied so as to give increased security against the possibility of excessive temperatures and the occurrence of arcs and sparks. In practice, this means that the cross-sections of conductors and insulation distances (creepages and clearances) are increased, and sparking elements (e.g., pluggable connectors) are eliminated. “Increased” represents a “better” electrical design.

First of all, use of Ex e terminal blocks in the equipment requires the manufacturer of the final device to have provided its own assessment. If the terminals are declared Ex components, meaning they have a component certificate with the letter “U” after the certificate number, this means that the manufacturer has assessed the safety aspects of the component (Ex e terminal blocks). None of the familiar certification systems (ATEX, IECEx) requires additional verification of the aspects included in the component certificate.

However, it should be noted that the Ex component cannot be used alone (it is not equipment), and additional factors need to be assessed. One example is junction boxes with rail-mount terminal blocks. Although terminal blocks can be Ex components (marked with Ex e and “U” in the certificate number), the entire equipment and other factors (not assessed in the certificate of the component) must undergo and additional assessment (tests). It should be noted that the heat that arises in such a junction box depends less on the rail-mount terminal blocks used (although they are also important) and more on the number and length of conductors in the box.

The rail-mount terminal blocks with increased safety (Ex e) WAGO produces are used with success in many explosion-proof devices. These rail-mount terminal blocks, mainly intended for mounting on DIN-rails, are produced in many types for different current ranges. They are subject to certification (third-party assessment) according to the requirements of various certification systems (the conformity assessment per the ATEX Directive, certification per IECEx etc.). Rail-mount terminal blocks are “Ex components” within the meaning of 60079-01 and “components” within the meaning of the ATEX2 Directive.

Rail-mount terminal blocks from WAGO that are marked “Ex e” meet the requirements for intrinsically safe design and can be used in intrinsically safe devices. However, they should be selected on the basis of an analysis (risk assessment) by the manufacturer of the final device.