Equipment Protection Levels and all that

One of the evil side effects of the ATEX Directive is that the IEC feels compelled to follow its more whimsical requirements. However the IEC must maintain its independence and consequently it follows similar principles but modifies the marking.The most recent manifestation of this phenomenon is the creation of Equipment Protection Levels (EPLs], which are the IEC equivalent of the ATEX categories. The following table summarises a fairly complex situation.

tabl4e.jpg

Fortunately the EPL concept did not follow the displaced numerical marking of the ATEX categories. Using category 2 equipment in a Zone 1 still does not feel right. The EPLs follow the intrinsic safety level of protection indication of a, b and c in line with the level of protection afforded by the apparatus.The intention of the concept is to divide apparatus into categories of equal levels of risk and mark the apparatus so that a technician could decide whether the level of risk is appropriate to the location of the equipment. The fact that the technician would require an infinite knowledge of the plant operation to make such a judgement is completely ignored. [In practice no one person ever has all the information necessary to make a reasonable risk analysis]. The same technician is considered incapable of remembering which type of protection can be usually used in which Zone, hence the requirement to introduce EPLs. The most that marking can achieve is to raise doubts in the mind of the knowledgeable technician and cause him to ask questions about the suitability of the apparatus

The illusion that a piece of apparatus in isolation determines its level of safety is only held by standards writers who persist in trying to completely describe apparatus on the label. In the particular case of intrinsic safety it is the system which determines the level of safety which is achieved. For example an ‘ia’ apparatus will be marked with an EPL ‘Ga’ but if connected in an ‘ic’ system it will achieve a ‘Gc’ protection level and the label is misleading. Intrinsic safety is the method of protection which is most prone to creating this deception but all the other methods of protection suffer from the same problem to some extent.

The reality is that if IEC Ex certification is used, EPLs will emerge and will have to be marked. The marking requirements of pressure transmitter certified intrinsically safe for use in both gas and dust are incredible in every sense of the word. If by chance the device is made flameproof and dust tight then a high level of information overload is achieved and an extremely large label is required. At this point an invitation to license my pull-down labelling facility is offered.

Pull Down Label

Perhaps one day there will be support for my campaign to reduce the label to a certificate number and a website address. When this happens then the availability of full and up to date information on certification and use could be ensured. It might even be possible to satisfy the requirement to have information available in the language of the country where the equipment is being used

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

6 Comments on “Equipment Protection Levels and all that”


  1. EPLs? Yet another mark to appear on a label? The labelling of apparatus already causes considerable confusion to the poor technician. Could I plea for the need for greater unity and consistency in the way Notified Bodies produce Apparatus Certificates? Then maybe we can rely on the certificate number and the website idea!

  2. mtlinst Says:

    This appears to have just been published acc the IEC Newsletter

    IEC 60079-26 Ed. 2.0 (2006-08) Preview Price: CHF 97.00
    Explosive atmospheres – Part 26: Equipment with equipment protection level (EPL) Ga

    Steve/MTL

  3. Bruce Durdle Says:

    There is a precedent in that, where equipment (such as prox probes) is too small to allow the full catastrophe to be included, certificate number and entity parameters only are acceptable. Pepperl and Fuchs for instance print these on the cable adjacent to the probe.

  4. mtlinst Says:

    The IEC ‘general requirements’ IEC 60079-0 does allow marking on small items to be reduced. Interestingly the current draft for voting has a clause which states

    ‘In the case of extremely small electrical equipment and extremely small Ex Components where there is no practical space for marking, a marking linked to the equipment or Ex Component is permitted. This marking shall be identical to the marking 29.2 , 29.3 and 29.4, as applicable, shall appear on a label provided with the equipment or Ex Component for field installation adjacent to the equipment or Ex Component’

    It will be interesting to see a practical embodiment of this clause. particularly as related to Ex Components. There are some potential problems if a number of component labels have to be attached to an assembly.

    The ATEX apparatus directive does not include a derogation for small components but the ‘Guidelines’ do. The requirement is for the CE mark. the Ex marking and the manufacturers identification.

    Fortunately just occasionally ‘common sense’ prevails and a smaller amount of marking as quoted in your example provides the necessary information. Whether it complies with the letter of the standard and directive is debatable. However it does not really matter since the equipment is adequately safe. I still feel a reference back to the fuller information on a web-site is the way forward.

    It is possible that the next edition of the IS apparatus standard [five years away ??] will not require marking of the terminal parameters since they are only of use in the system design. The parameters will still be included in the apparatus certificate.


  5. We are involved in ATEX compliance within the waste industry and in particular for landfill sites. The responsible person is usually considered to be the Landfill Site Manager. As you can imagine the system needs to be pretty intuitive to be useful to these guys, who are usually recruited to be good general managers rather than technical people.

    Complex although the compliance rules are, it really is still necessary for non-specialists to at least be able to understand labelling matters in concept at least very readily. Landfill gas is 60% methane, on average, so there is plenty of gas around to cause explosion risk!

    The labelling system on the leachate extraction pumps, and other related equipment which is installed in landfill sites is important, but poorly understood. Some operators don’t use explosion rated equipment pointing out that they have used the same pumps for at least 20 years without incident, while others would be appalled.

    In working for clients across the landfill industry we find surprising variations in implementation of ATEX (DSEAR in the UK). The root of the problem of compliance does lie to an extent in the complexity of the labelling, which in my view is quite simply incomprehensible to many in the waste industry.

    However, in my experience of real life explosion incidents at landfills, it has not been ensuring the correct rating of the equipment which incurs the highest risk at all, it has been shown far more important to simply rigorously enforce of the site “No Smoking” rules, and avoid making sparks.

  6. Estellito Junior Says:

    This is a very important safety measure, as we know that OSHA is a legal requirement for USA, beyond a simply technical one.
    Regarding the OSHA “permitted installations”: 1) intrinsically safe, 2) approved for the hazardous (classified) location, or 3) safe for the hazardous (classified) location, please, note that it is not allowed to consider “the consequences of an explosion” to install equipment with a “lower safety degree” of those required by American standards.
    Comparing with the IEC EPL method, where a “lower EPL than required” is allowed if “the consequences of the explosion” are “small”, we can say that OSHA method is safer.
    The EPL method sounds as a “black hole”, where all installation’s “non-conformities” can “disappear” with a snap, simply saying that “the consequence of an explosion is minimal”.
    How may deaths can be considered as “minimal consequence” of an explosion?
    This “EPL” seems to be against all safe requirements given by IEC Ex standards.


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s


%d bloggers like this: