Safety devices under article 1.2. of the directive, concerning the issue of assessment and EC type examination ( according to Annex III )

A safety device in itself is in most cases placed in a safe area without being an ignition source itself, but controlling a possible ignition source inside a hazardous area. I.e. Exe motor overload relay.

The assessment procedures described in article 8 is concerned / aimed against the risk of an equipment not becoming a source of ignition and therefore reflects this risk by requiring electric ignition sources or combustion machinery to undergo the Annex III EC-type examination procedure to ensure that a well qualified N.B. carrying out tests to prove this (for category 1 and 2 equipment that is, except for non - electrical and non - combustion equipment )

In spite of some effort during the guide revision process, and CLC 31 WG 9 making a proposed standard for the construction, evaluation, and testing of safety devices under the directive, we experience some lack of clarity around this issue especially from our national NB's.

The real technical / risk - question around this issue is : shall we treat ”reliability of a function” on the same level as ”a potential source of ignition” ( in particular when it comes to equipment experience a first fault leading to a dangerous situation like a stalling rotor ) with respect to conformity assessment procedures under 94 / 9 / EC.

If one look at the guide clause 8 concerning conformity assessment procedures, it states that generally it shall be assessed according / together with the equipment under control ( EUC ) . Do we mean simply together with, or by the same ”lines” as the equipment itself.

As it is stated now it may differ whether it is a category 2 non - electrical EUC ,or it is an category 2 electrical EUC, whether a N.B. ( Annex III ) or not, is to be involved in the assessment.

In the case of a separate piece of a safety device is being put into the market, the issue becomes even more relevant as a manufacturer would not find 100 % answer in the directive itself or in the guide ( * although it is indicated in the example with the Exe motor that the overload relay shall undergo the same assessment procedure as the motor itself .) in other words, whether he has to bring this equipment trough an Annex III procedure, or not

( * That being a bit of a conservative ”short circuit” in risk thinking around the directive,… and I have to take some of the blame for that being the one who brought the sentence along, sorry )

I know in some countries around Europe the Exe overload relay was tested by a N.B. for accuracy around it's capabilities concerning disconnection within the stalling time ( t E ) before ATEX came along. Though, no standard exists apart from what is in the 79 - series of today around this , and what is stated in the Annex II clause 1.5. and 1.6. ( which in fact could be used as a ”safety frame” for testing of ”simple” safety devices, as CLC 31 WG 9 has expressed it )

We should conclude on this matter by a discussion around the risk by, on the one hand : the equipment manufacturer himself making and assessing the safety device along with the Annex VIII procedure, or on the other hand : if the potential risk by possible lack of reliability, accuracy or other shortcomings should be in some way eliminated by a NB testing this safety device. ( if the NB has relevant standards apart from the IEC 61508, which is really a ”overkill” in the matter of Exe overload relays and other temperature limiting devices )

PS . The industry in general dealing with safety devices is generally going along the lines of the not having a mandatory requirement for a 3.party verification / testing of the reliability / accuracy stated for the safety device. ( Although the are not all agreed on this and the discussion is ongoing )

It is as such more up to the final user to test and prove his circuit, but with some confidence that the components in the circuit is what the vendor guaranteed concerning reliability / safety integrity level / probability of failure on demand, or similar.

Geir Ottersen

DSB

Norway

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ATEX/05/2/4.7

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