How Special is Special Protection?
06 April 2009
For many years, standard IEC 60079-0 has stated in its scope that the letter ‘s’ is reserved for use to identify equipment which does not comply with the requirements of any of the established types of protection. Nonetheless, Ron Sinclair considers this classification suitable for application in hazardous atmospheres.
How Special is Special Protection?
There is an implication that individual national committees can write a standard, or otherwise determine rules, for Ex s, if they so choose. A few countries (e.g. Australia) did issue national standards, but in the UK two separate standards were issued – neither through the national standards body, BSI.
The first was Baseefa Standard SFA 3009, first issued in the early 1970s. This set out basic rules for judging some forms of “special” protection, including techniques such as hermetic sealing and encapsulation. However the “catch-all” clause was a statement that equipment was certified as Ex s if, in the opinion of the Director of Baseefa, the equipment was considered to have equivalent safety to a product which did comply with one of the recognised forms of protection. At that time, well over half the equipment marked Ex s was, in fact, encapsulated.
With the introduction of the standards specifically for encapsulated equipment (EN 50028 and IEC 60079-18), the relevant material was removed from SFA 3009 and its use was significantly diminished. An early draft for flameproof breathing and draining devices was also appended to SFA 3009 for a short period, before the material was formally published in the flameproof standard. In this way, Ex s was used as a means to certify equipment which was covered by standards still under development.
You will note the deliberate reference to certification. We always used to say that Ex s equipment was special in two ways: the method of protection was special; and the extra care devoted to justifying the actual method of protection for the individual equipment gave an even higher (or more special) guarantee of safety than mere compliance with an established protection concept.
What was strange over later years is that other certification bodies started using and quoting SFA 3009. How they managed to get an opinion from the Director of Baseefa, as required by the standard, without even letting him know of the project or product, remains one of life’s mysteries!
As SFA 3009 was written specifically in a Group II context, Baseefa later became involved with the UK Mining Inspectorate in writing a similar document specifically for use with Group I equipment, which also took account of the mining environment. This was numbered HSE(M)01.
But time moves on and we are now in the ATEX era. As you are probably aware, an EC-Type Examination Certificate issued in accordance with the rules of 94/9/EC does not necessarily confirm conformity with particular standards. The certificate is written directly against the Essential Health and Safety Requirements (EHSRs) of the directive. The use of standards to support claims of compliance is voluntary (though absolutely normal and expected).
If standards are not used, the manufacturer has to show in detail why he believes his product does conform to the EHSRs, including recording any necessary original research into his protection technique. Compliance with a standard is therefore the easy option, and also is considered to represent the “state of the art” which has to be adopted by the manufacturer in order to claim compliance with the EHSRs.
However, the option of directly using EHSRs rather than standards has, in many ways, overtaken the use of Ex s in the ATEX field. The only problem is that it is now not always clear what has been done and how the equipment is protected. There is a strong suspicion that there are a number of items of equipment in the field with declarations directly to the EHSRs, simply because the manufacturer thought it too costly, or too inconvenient, to comply with the relevant standard.
It is not possible to play fast and loose with the standards in the same way within the IECEx Scheme, as an IECEx Certificate is directly to the standard, without the possibility of “convenient” deviations. But there does remain a desire to find some way of getting, with a high degree of confidence, international recognition for products which are innovative and breaking new ground, before the standardisation process can catch up with them. Note that it is typically between three and eight years before a “new idea” can be adopted within a standard. This is a long time to wait before introducing a novel product which might have significant safety advantages despite not quite fitting the established protection concepts.
This is the motivation behind the drive to create a new Ex s standard within IEC TC31, in conjunction with the IECEx Certification Scheme.
By the time you read this, we will have had the final Project Team meeting in Windsor to prepare the first draft of what is to become IEC 60079-33: “Special Protection”. At this stage it will be what is known as a Committee Draft (CD) and will be circulated to all National Committees for comment. It will not be made available as a Draft for Public Comment (DPC) by BSI at this stage of development, but will be circulated within the BSI GEL/31 committee to get the response of committee members and their suggestions for improvement or amendment. GEL/31 will discuss the comments at its next meeting in September, in order to make formal comment ready for further discussion at the next round of standards meetings in Tel Aviv in October.
Depending on the outcome at Tel Aviv, we will either have a further CD or move to a Committee Draft for Voting (CDV) which will be issued by BSI as a DPC. If it is a CDV, a parallel vote will also be instituted in Cenelec TC31 for the standard to be adopted as EN 60079-33 and subsequent harmonisation under the ATEX Directive. Eventually, the standard will be published in the UK as BS EN 60079-33 or, if not adopted by Cenelec, as BS IEC 60079-33. Best guess for this is 2011 or 2012.