Worldwide, explosion protection is based on the international IEC 60079 series of standards, European and American norms, standards, and directives. In the USA, the National Electrical Code (NEC) establishes basic regulations. In Canada, these regulations are established by the Canadian Electrical Code (CEC).
For the CENELEC countries of the European Community and beyond, Directive 2014/34/EU is of central importance for manufacturers of equipment and protective systems. Worldwide requirements are confirmed by certification according to IECEx. The application is approved under the protection class “Increased Safety” Ex e in Zone 1 and 2.
According to EN IEC 60079-0, Ex terminal blocks are known as Ex components. By definition, these are components required for the safe operation of devices and protection systems, but do not fulfill an autonomous function.
They are approved for the increased safety “e” protection class and are not marked with the CE mark according to the European ATEX directives 2014/34/ EU.
Notified bodies issue EU type examination certificates in accordance with EN IEC 60079-0; EN IEC 60079-7 and the ATEX Directive. By issuing the Production Quality Assurance Notification, a notified body confirms that the requirements of the ATEX Directive are fulfilled according to Annexes IV and VII.
Suitable accessories are listed in the Ex certificates. To adhere to the creepage and clearance distances for Ex e, use terminations and partition plates. Terminal blocks for intrinsically-safe circuits “i” are passive components.
Therefore, you do not need a type examination certificate for use in intrinsically-safe circuits. We recommend blue terminals for clear identification and easy recognition. These, as well as the accessories, have to comply with the type according to EN 60079-11.
No separate approval is required for terminal blocks for applications with intrinsic safety Ex i protection class requirements. In addition to the Ex e approved terminal blocks, other standard terminal blocks can also be used, although the following more stringent spacing requirements apply in the Ex i area:
• Between conductor entries and adjacent terminals
• Between conductor entries and grounded metal parts
• Increased requirements for clearances due to solid insulation
When test disconnect terminal blocks or fuse terminal blocks are used, they must have approval for the increased safety Ex ec protection class. In this case, increased requirements apply to the terminal blocks and their functional units. For example, all disconnectable elements must have a release force greater than 15 N or 100 times their own weight to prevent unintentional opening.
Other national and international approvals and directives are based on the IECEx approval. For example, ATEX for the European market, CCC Ex for the Chinese market, KC for the South Korean market or EAC Ex for the Eurasian Economic Union, which includes Russia, Belarus, Kazakhstan, Kyrgyzstan and Armenia.
Explosion-protected equipment must be marked in such a way that it is used correctly according to its safety-related properties. There is a marking obligation for terminal blocks with an increased safety “e” protection class. This equipment marking requirement is described in IEC/EN 60079 Part 0 and Part 7. The following illustrations show an example marking of a terminal block.
1. Rated cross-section
2. Rated voltage
3. ATEX label
4. Type of protection label
5. ATEX certificate number
6. IECEx certificate
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