TRANSFORMERS, SUBSTATIONS + CABLES
Misleading claims on flameproof junction boxes for Zone 0 applications Dr Geof Mood, Technical Director, CCG Cable Terminations
I n the December 2021-January 2022 issue of this publi- cation, in an article titled Flameproof junction boxes , the author made a series of incorrect and misleading state- ments. The author also made a dangerously incorrect claim about the suitability of installing an Ex d flameproof enclo- sure with Ex e terminals in a Zone 0 area. If any installers believed the claims and installed the product accordingly they would at the least be negligent of their obligations for installing electrical equipment in hazardous areas and po- tentially criminally responsible for any resulting explosion and loss of life. The claim was that by installing Ex e terminals inside an Ex d junction box, the installer would achieve the two levels of independent Ex protection required for a Zone 0 installa- tion. This is erroneous. The actual wording of the claim made was: “However, with the inclusion of increased safety terminals inside a flameproof enclosure, the termination’s rating is pushed up to Zone 0 (two independent levels of protection via EPL Gb, per SANS/IEC 60079-14/26) which means it can be installed in an environment where there is a constant hazard.” The important words to take note of are: “two independent levels of protection”. The certification of any Ex e terminal (including the author’s own terminals) always contains the following words in the Schedule of Limitation: “The terminals may only be used inside a previously approved Ex enclosure with a minimum IP rating of IP54.” This means quite clearly that the terminals only become certified Ex e when they are inside a suitable Ex enclosure
(usually Ex e) and putting them inside an Ex d enclosure with an IP rating of IP54 or better would satisfy this requirement. However, this does not make the level of protection provided by the Ex e terminals independent of the Ex d protection provided by the enclosure as they depend directly upon the Ex d enclosure for ingress protection and protection against impact in order for the terminals to achieve Ex e certification. The combination of any Ex d enclosure with any Ex e terminals will therefore only provide one level of protection, not the two independent levels of protection required for use in Zone 0 as claimed by the author. If further proof is needed, the certification number of the author’s own Ex e terminals ends with the letter ‘U’. This means these terminals are certified only as components and therefore must be re-assessed as part of an Ex assembly. To quote IEC 60079-0: “The symbol “U” is used to identify that the equipment is incomplete and is not suitable for installation without further evaluation.” This is not the language used of a product providing an independent level of protection and is in conflict with the author’s advice. The author compounds the earlier incorrect statement by adding the following: “The important point to remember, if you are advising anyone on such an installation, is that this termination is now suitable for Zone 0 applications, with minimal additional consideration.” My response to this is twofold. Firstly, if you are giving advice about Zone 0 installations you should really know the Ex standards and what is required (and so should the person specifying the installation). The specifier should also examine the certification of the products being used in such a safety-critical application.
SANS/IEC 60079-14 clause 4 states: “It is necessary to ensure that any installation complies with the relevant equipment certificate as well as with this standard and any other requirements specific to the plant on which the installation takes place.” Secondly, regarding the words “with minimal additional consideration” , when it comes to installing electrical equipment in Zone 0, or in any zone for that matter, there are many “additional considerations”. SANS /IEC 60079-14 Scope states: “Where the equipment is required to meet other envi- ronmental conditions, for example, protection against ingress of water and resistance to cor- rosion, additional protection requirements may be necessary.” In clause 4 the standard goes on to say: “Consideration should be given to obtaining
The photographs show the environmental effects on a flameproof junction box.
26 Electricity + Control MARCH 2022
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