Hieroglyphics didn’t come to an end after Ancient Egypt

The marking requirements for electrical equipment for use in hazardous atmospheres has become ludicrous and is about to become even more so. The primary function of marking should be to assist in ensuring that equipment is correctly installed in its intended location. There is a need for the equipment to be readily identified and traceable back to its manufacturer, so that necessary maintenance and replacement can be safely carried out. Traceability is desirable if any questions arise about the adequacy of the safety of the equipment. In practice when a significant disaster occurs, equipment labels frequently become illegible.

The current state is that the marking requirements have been steadily increased every time a standard is revised or a new regulation is introduced. The result is a meaningless set of hieroglyphics, which can only be interpreted by a few sad characters who spend far too much time at standards meetings. [Unfortunately that includes me]. I sometimes suspect that when archaeologists in 3006 dig up a discarded instrument they will mistakenly categorise it as early Egyptian.

A typical example is a field mounted temperature transmitter intended to be mounted in a Zone 1 with its sensor mounted in Zone 0 and certified under the IEC Ex scheme. It would probably be marked


This is not very meaningful to the technician installing the equipment but is possibly the required marking. If the apparatus is also useable in dust locations Zone 20 and 21, which it probably would be, then the following additional marking required would be:


NOTE: Higher values for Co and Lo could be added but that would be even more confusing

This marking would probably be added just below the red marking for gases. The black marking is common to both gases and dust. Probably colours could not be used, but it is desirable to distinguish between the two possible causes of the hazard

Additionally the apparatus could be marked to clarify its use in both gas and dust ‘ic’ systems but hopefully most manufacturers would resist this temptation.

An additional straw [if you wish to sell in Europe] is to comply with the ATEX Directive. In addition this requires the manufacturer’s address, the year of construction, the epsilon Ex ?, the equipment group and category , for Group II equipment the letters ‘G’ and/or ‘D’ and the CE mark ?. The CE mark is followed by the registration number of the organisation responsible for the surveillance of the quality control system of the manufacturer. This completely useless piece of information is what every technician needs.

The marking then becomes


It is possible to go on to illustrate the additional requirements for the US market, but it is increasingly obvious that the marking requirements are out of control and meaningless. In fact the probability of this illustration being correct is very low.The solution is to provide the technician with enough information to ensure that he is installing the intended piece of equipment in the intended location and that he has access to any further information he may need. A manufacturer’s name, an equipment type and serial number, a web-site address and a certificate number is all that is required. The IEC Ex scheme is a move in the right direction, but the IEC standards continue to increase the marking requirements and IEC Ex is considering introducing its own mark The ideal situation where IEC Ex certificates are accepted world wide and parochial marking requirements derived from such as ATEX and OSHA are removed is unlikely in the foreseeable future. However recognition that most of it is unintelligible, possibly misleading and only there to satisfy the idiosyncrasies and egos of the writers of standards and legislation is possibly the first step. The second step is to recognise that the required information for designing and installing a safe system is available from the apparatus certificate and the manufacturer’s instructions. These are or should be readily available, ideally on the web so they are up to date. Guessing that equipment is adequately safe from the marking on the apparatus is not an acceptable practice.

A possible happy consequence of simplifying the marking would be that the content of all the competency training courses would be halved and all the numerous posters devised by manufacturers and certifying bodies would be redundant. It would make the setting of test questions almost impossible.


Explore posts in the same categories: ATEX Directive, IEC, Intrinsic Safety

2 Comments on “Hieroglyphics didn’t come to an end after Ancient Egypt”

  1. Robin Garside Says:

    I enjoyed reading this.
    Marking has, as you say gone crazy.
    Using encapsulation as a technique for dusts we can already get ‘maD’ and we are soon going to be very close to Da* maD.
    What I really wonder, though, is how we ‘sad characters’ (who have, after all been at the forefront of this technology for some time) have managed to allow this to happen.
    Anyhow, keep up the good work.

  2. tqmcintl Says:

    Nice blog
    i got u added to my favourites

    i also have u linked here http://tqmcintlexd.blogspot.com/

    Keep on blogging

    The Ex world needs u

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