International Standards Update
Author : Jim Munro - Chair IEC TC 31
08 December 2011
This update will focus on the importance of standards in the conformity assessment process for Ex equipment and the relationship between TC 31 and IECEx.
Jim Munro
But first let me take you to a recent personal experience.
Prior to the IECEx meetings in Split, on the coast of Croatia, I skipped a sailing boat with my whole family for a week of sailing around a few of the thousand plus beautiful and often historic islands in the Adriatic Sea. On the third day on a crossing between Brac Island and Hvar Island the wind rose to a brisk 25 knots and the waves became quite large. I had reduced sail on the mainsail and the genoa (the sail up the front), but the boat still had an impressive lean with the sea occasionally washing over the rail near the water. I was having a great time but my family was somewhat concerned and did not seem to share my exhilaration. In fact they accused me of being a thrill seeker. I tried to explain the laws of physics to them which meant there was an infinite righting moment on a 46 foot Bavarian with a fixed keel and hence there was no chance of a capsize. But they seemed less than impressed. In retrospect, perhaps I should have waxed more lyrical on the national (DIN?) or international standards that I am sure the German marine engineers applied to the design and building of this beautiful sailing boat.
Similarly when someone walks into any a hazardous area such as a petrol refinery, an underground coal mine or a grain silo, they are trusting their lives to the compliance of equipment in that area (in particular electrical equipment) to standards that minimise the chance of the equipment causing an explosion in an environment involving explosive gases, vapours, mists or dusts.
Until not so many years ago, the compliance of this equipment with appropriate standards was likely to have been established with testing by a local certification and testing body, and possibility assessment of the manufacturer by the same certification body. The standard involved may well have been a local standard with major differences to comparable standards elsewhere in the world. As most of you are probably aware, this situation has changed with the extensive acceptance of the IECEx System (formerly called the IECEx Scheme). This has aimed at having one standard, one test and one certificate. What is the basis for this process? It is the standards produced by IEC Committee TC 31 Equipment for Explosive Atmospheres that are now widely accepted throughout the world.
Right from the beginning of this process, IECEx and TC 31 have worked hand-in-glove. As Chairman of TC 31 I have an ex-officio role on the IECEx management committee, ExMC. Together with my fellow chairmen of the TC 31 subcommittees I also have a role on the ExTAG which is the forum for certifying bodies (ExCBs) and testing laboratories (ExTLs).
In this article I would like to explore this process a bit further and to talk about some of the outcomes of the IECEx meetings that took place in Split between 5 and 9 September 2011 relevant to TC 31.
First let me state again that at present the IECEx System is heavily dependent on the TC 31 standards. In the Equipment Certification Scheme, the TC standards are currently the only standards that equipment can be certified to. To date these have only been standards for electrical equipment. However, TC 31 through its subcommittee SC 31M is in the process of producing standards for non-electrical equipment (more about this in a later article). However, there was a significant development at the meeting in Split. It was decided to adopt the recently published standard on assessment of Ex manufacturers, ISO/IEC 80079-34. This is the first standard produced by SC 31M and replaces the current IECEx operational document, OD005-1 dealing with the same subject. It gets better. This OD was based on a draft of European Standard EN 13980 which has been used for assessment of Ex manufacturers in Europe under the ATEX Directive. A decision has also been taken in Europe to replace the current EN 13980 with the new ISO/IEC standard (with an additional annex for non-electrical equipment). This is likely to flow into other countries.
In the IECEx Certified Service Facilities Scheme, IEC standard 60079-19 forms the core of the scheme in terms of the requirement that any service facility must depend. When the second edition of this standard was published it replaced an earlier IECEx OD that addressed this subject. There is now a third edition of this standard.
Having common standards is a great start to achieving consistency in testing and certification on an international basis. But as many of you involved in the testing process will know, despite our best efforts in TC 31, we still produce standards with some requirements that are hard to interpret. This can result in less consistency in the testing and certification process. Is there a solution? There are in fact two possible solutions; one offered by IECEx and one through the IEC standards process.
Some years ago IECEx developed an approach based on practices used in places such as CENELEC and Australia of producing ‘decision sheets’. These allow people to come up with a way of helping to consistently apply standards. However, there can be a problem if these are used for interpretation of technical requirements of standards, or even to add requirements to standards, if the technical requirements incorporated in the decision sheets become contradicted by later editions of a standard. Thus a product certified using a decision sheet might later be deemed to be not compliant with a standard. In a worst case scenario the technical committee responsible for the standard might decide that the approach taken in a decision sheet could lead to equipment being unsafe. One of the reasons for this is that the acceptance process for decision sheets goes through a very different process to the standards process. Decision sheets are dealt with through the ExCBs and ExTLs on ExTAG. Standards are dealt with the national committees that are members of TC 31 and involve a much wider participation since the national committees of those member bodies are also involved in the process.
Fortunately there has been a solution made available through IEC. It is now possible for an interpretation sheet (called an I-SH) to be issued to clarify clauses of standards. Each interpretation sheet relates to only one edition of a standard. So if there is more than one edition of a standard with a similar problem then more than one interpretation sheet will be needed. TC 31 has put in place a process that involves the maintenance teams of the standards to produce the interpretation sheets. However, once drafted, these interpretation sheets go through a voting process to the same national committees so that there is a very high level of confidence that later editions of a standard will be entirely consistent with an interpretation sheet for a current or earlier edition of a standard. In the ExTAG meetings, such as the one in Split, I find myself regularly having to provide advice as to whether a proposed decision sheet is appropriate or whether it would better be dealt with in the relevant TC 31 maintenance team. On occasions we have decided to do both (since the IECEx process is generally quicker) but withdraw the decision sheet once an I-SH is issued.
There is always a balancing act between the standards processes and the conformity assessment processes. An example in the ExTAG meeting in Split was a decision sheet relating to a sealing test of cable glands. it was decided to refer this back to TC 31 to produce an I-SH since the draft decision sheet was rather too like an interpretation of the standard.
At the ExMC meetings, I always present a TC 31 report. This year there were a two areas for which I was seeking support from ExMC. Both related to providing better information on changes that have occurred from one edition of a standard to the next. The first involves the use of ‘redline standards’. This has been offered in the past few years by IEC but there was been some doubt whether it would continue. A pdf version of a standard can be made available with the changes being highlighted using red text and strikeout, in similar fashion to tracked changes in Word. The pdf document also contains a ‘clean version’. There are now three TC 31 standards issued in this way; IEC 60079-0 Edition 6.0, IEC 60079-11 Edition 6.0 and IEC 60079-18 Edition 3.0. ExMC indicated its support for this approach and this will be passed back to IEC. TC 31 has also established a task force to better show the significance of changes which have occurred from one edition to the next. This will be further considered at the TC 31 plenary meeting in October 2011 in Melbourne. Again ExMC gave its support for the direction being taken.
The following is my regular update on TC 31 standards and associated documents that have been published over the past 12 months; this time to the end of September 2011:
IEC 60079-0
Also available in redline version
Ed 6 2011-6 Explosive atmospheres - Part 0: Equipment - General requirements
IEC 60079-11
Also available in redline version
Ed 6 2011-6 Explosive atmospheres - Part 11: Equipment protection by intrinsic safety "i"
ISO/IEC 80079-34
Ed 1 2011-4 Explosive atmospheres - Part 34: Application of quality systems for equipment manufacture
IEC 60079-35-1
Superseding
IEC 62013-1 Ed2 Ed 1 2011-5 Explosive atmospheres - Part 35-1: Caplights for use in mines susceptible to firedamp - General requirements - Construction and testing in relation to the risk of explosion
IEC 60079-0
Corrigendum Ed 5
Corr 1 2010-12 Explosive atmospheres – Part 0: Equipment – General requirements
IEC 60079-19 3 2010-11 Explosive atmospheres - Part 19: Equipment repair, overhaul and reclamation
IEC 60079-13 1 2010-10 Explosive atmospheres - Part 13: Equipment - protected by pressurized rooms "p"
References:
1. ISO/IEC 80079-34 Edition 1.0 Explosive atmospheres - Part 34: Application of quality systems for equipment manufacture
2. IEC 60079-19 Edition 3.0 Explosive atmospheres - Part 19: Equipment repair, overhaul and reclamation
3. IEC 60079-0 Edition 6.0 Explosive atmospheres – Part 0: Equipment – General requirements
4. IEC 60079-11 Edition 6.0 Explosive atmospheres - Part 11: Equipment protection by intrinsic safety "i"
1. IEC 60079-18 Edition Explosive atmospheres – Part 18: Equipment protection by encapsulation “m”
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