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The development of non-electrical standards through TC 31 subcommittee SC 31M

Author : Jim Munro, Chairman, IEC Committee TC 31

27 May 2013

In my last article I talked about the ‘art of consensus and compromise’.  This can be lifted to a new level when one is seeking consensus in both IEC and ISO (International Organization for Standardization).  But more about that later. Initially, I would like to talk about the work that is occurring on the development of non-electrical standards within TC 31.  

In 2005, there was a proposal within ISO for a new committee to develop standards for non-electrical equipment.  However, it was recognised within TC 31 that this could introduce a potential conflict with the electrical standards.  TC 31 had already experienced difficulties with keeping its standards separate when the dust series of electrical standards was developed separately.  

As a result of the issues arising, the dust standards they have were later integrated as much as possible into the gas series of standards.   It was thought in TC 31 that developing non-electrical standards in a separate committee and standards organisation would remove the option to take a similar approach with the non-electrical standards.  

A paper was developed by the TC 31 officers to draw attention to the potential pitfalls of a separate ISO committee developing standards for explosive atmospheres.  This was circulated within IEC as an information document and it included the suggestion that TC 31 IEC member bodies discuss the issue with their ISO counterparts.  

As a result of this, a number of ISO member countries voted against the ISO new work proposal and discussions were initiated with the ISO Technical Management Board (TMB) and the IEC Standardization Management Board (SMB) on options for a more integrated standards development structure for explosive atmospheres.  Initially the TMB suggested that a joint ISO/IEC committee be formed to handle all explosive atmospheres standards.  However, there were concerns within TC 31 that this might have an adverse impact on the existing range of standards in TC 31 and their maintenance.  Hence a paper was developed by TC 31 officers suggesting the formation of a joint ISO/IEC subcommittee with TC 31.  This was a model that had never been tried before in ISO and IEC.  

As a result of this, SMB and IEC agreed to set up a joint task force involving SMB and TMB members, ISO and IEC officers, and the officers of TC 31.  The then secretary of TC 31 (George Thompson) and I were the TC 31 officers on the task force.  The outcome from the task force was a recommendation to form a subcommittee within TC 31 with the authority to develop non-electrical standards.  This included a number of recommendations on how the subcommittee should be structured and should operate.

A detailed table was developed by the joint ISO/IEC task force outlining how the various stages of projects would operate from initial work proposal through to voting and publication, including the role of IEC and ISO at each stage.  This table is too large to include here but can be found in Annex E (IEC SC 31M – Working Procedures) in the TC 31 Good Practice document, which can be accessed for free at:
http://www.iec.ch/dyn/www/f?p=103:7:0::::FSP_ORG_ID:1232

Essentially most work is done using IEC procedures but with ISO members able to nominate experts to the various groups, such as project teams and to vote on the documents developed.

Thus in 2007 it was jointly agreed by ISO/TMB and IEC/SMB to establish IEC Subcommittee SC 31M within IEC TC 31 instead of establishing a separate committee in ISO.  It was agreed that IEC SC 31M would produce IEC/ISO double logo standards as either double prefix ISO/IEC, or single prefix ISO and IEC standards.  The secretariat would be held by ISO/DIN/ in Germany. 

It was also agreed that the TC 31 Chairman’s Advisory Group (CAG) would have a formal role in the allocation of work to SC 31M, including consideration of work within TC 31 or other subcommittees that might better be managed in SC 31M.  This was a departure from the normal role of the CAG which for other work in TC 31 is an advisory one.

The title of IEC SC 31M became:  
Non-electrical equipment and protective systems for explosive atmospheres
With the scope of SC 31M:
To prepare and maintain international standards relating to non-electrical equipment and protective systems for use where there is a hazard due to the possible presence of explosive atmospheres of gases, vapours, mists or combustible dusts.

Note: For the purposes of this sub-committee non-electrical equipment is defined as "equipment which can achieve its intended function mechanically". For the purposes of this sub-committee, 'Protective system' is defined as devices other than components of the equipment which are intended to halt incipient explosions immediately and/or to limit the effective range of an explosion.


Thus SC 31M was formed as a unique approach to joint development of standards between IEC and ISO.

The first Chairman of IEC SC 31M, Dr Heino Bothe from PTB, was approved by IEC/SMB and ISO/TMB for an initial term of 6 years.  With that term now completed he has retired from the role as of the end of 2012 and his place has been taken by Michael Beyer, also from PTB.  About the same time the first Secretary of SC 31M, Thomas von Hoegen from DIN, was also replaced, by Anke Sachtleben, also from DIN.  

The following are types of standards that can be developed by IEC SC 31M:
* ISO/IEC double logo with ISO prefix 
* ISO/IEC double logo with ISO/IEC (preferred) or IEC prefix

There are some existing TC 31 standards now undergoing maintenance within SC 31M but I will focus here on the new standards.

The first double logo standard produced by SC 31M was published in April 2011.  It is ISO/IEC 80079-34: Explosive atmospheres – Part 34: Application of quality systems for equipment manufacture.

This standard is being picked up around the world. It has also been adopted by IECEx.

There are more new ISO/IEC double logo standards that are under active development.  Two of these are:
ISO 80079-36 Explosive atmospheres – Part 36: Non-electrical equipment for explosive atmospheres — Basic method and requirements; and
ISO 80079-37 Explosive atmospheres - Part 37: Non-electrical equipment for explosive atmospheres — Non-electrical type of protection constructional safety "hc", control of  ignition source "hb", liquid immersion "hk”

These cover protection technique requirements relevant for non-electrical equipment.  Part 36 complements and refers to IEC 60079-0, the general requirements, and introduces ignition hazard assessment.  Part 37 introduces explosion protection techniques not covered by current standards.  It will also be possible to apply appropriate current techniques (e.g. Ex d) to non-electrical equipment.  The above standards are ISO standards because they contain requirements only relevant for non-electrical equipment.

The third is ISO/IEC 80079-38 Explosive atmospheres - Part 38: Equipment and components in explosive atmospheres in underground mines.  It specifies the explosion protection requirements for equipment that may be an individual item or form an assembly.  It covers electrical and non-electrical equipment.  This is an ISO/IEC standard because it contains both electrical and non-electrical requirements.

All 3 standards were issued as committee drafts for voting (CDVs) in June 2012.

Certification schemes such as IECEx could certify to these standards once they are published.  IECEx has established a working group (ExMCWG15) to consider how this can occur.  I am convenor of the working group and our first meeting is planned for 13 and 14 March 2013.

As the above three documents had reached the voting stage they were subject to voting in both IEC and ISO.  All passed voting in IEC but unfortunately the first two failed voting in ISO.  This is where the consensus process appears to have broken down.  

We only received a small number of votes from ISO members, 12 in one case and 11 in another, with 4 voting negative.  This was a high enough percentage for the vote to be disapproved.   In contrast in IEC, votes were received from over 20 countries with a comparable or smaller number voting negative.  Hence the negative votes in ISO had a much more dramatic effect.  Something we are now beginning to realise is that, while we have been very successful in achieving an integrated approach at the international level for explosive atmospheres, many countries have not managed to achieve effectively mirror operations for this.  I have come across this situation first hand in Australia where we effectively have three different committees dealing with matters covered by SC 31M.   We have found that this has impacted on our ability to provide effective input.  

So it seems in TC 31 and its subcommittee SC 31M we will need to explore ways to help the countries interested in non-electrical standards provide more effective input to our work.  The founding officers of SC 31M did an excellent job in getting the SC 31M work to this stage, but the new officers will have this new challenge in front of them.

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Update on published standards

The following is my regular update on TC 31 standards and associated documents that have been published over the past 12 months; to mid March 2013.  
* IEC 60079-0 Corrigendum 1 2012-11 - IEC 60079-0: Explosive atmospheres – Part 0: Equipment – General requirements
* IEC 60079-33 1.0 2012-09 - IEC 60079-33: Explosive atmospheres - Part 33: Equipment protection by special protection ‘s’
* IEC 60079-20-1 Corrigendum 1 2012-7 - Explosive atmospheres – Part 20-1: Material characteristics for gas and vapour classification – Test methods and data


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