Springing forward in Stockholm
05 July 2011
During the two weeks in Sweden for the IEC meetings in April, we saw winter turn into spring. Ice flows in the harbour and snow piled at the roadside disappeared and were replaced by spring bulbs, and the outside terrace seating of the hotels and cafes came back into use. In the UK we are not used to such a sudden transition, and at last I understood some of the references in the Wallander novels.
As usual, we tried to fit in as many meetings as possible to maximise the benefits of people travelling from all over the world, so it was a full programme, but it was good to have the middle weekend free to see the sights and the magnificent museums. My particular interest started with the work of the “Motor” working group. This group advises across all the standards in the 60079 series, providing an expert input to the various maintenance teams (MTs). Discussions on the effect of supplying motors from variable frequency drives is one such “horizontal” issue, and contributions were made specifically to the installation and maintenance standards, to reflect input made on a previous occasion to the construction standards. Coupling a motor to an unsuitable inverter is a sure way to invalidate its certification, as the effect on such aspects as potential high voltage discharges and hot rotor shafts are not always easy to predict.This year, the main task was in reviewing the motor requirements in the existing Ex n (60079-15) and Ex e (60079-7) documents, to prepare a single set of requirements to go in the revision of 60079-7 when it brings in Ex ec to replace Ex nA. This is a significant task, as for historical reasons, the way the two standards were written had varied considerably. But as we found out later in the fortnight, the task with motors was easy compared with combing the requirements for luminaires into a single document.
Batteries were also to prove a problem, but the MT for 60079-7 beavered away and we should soon have a first draft document for comment. There can be differing views on whether the decision to split most of the Ex n standard among the other standards, taken in principle a number of years ago, was correct.But we have gone too far down the route to change our minds. It was the creation of the concept Equipment Protection Level (EPL) which enabled the extension of the Ex ia and Ex ib levels that we have known for many years to fit the other concepts. We already have Ex ic to replace Ex nL and Ex mc to replace the encapsulation requirements of 60079-15.
In addition to most of Ex nA appearing in future as Ex ec, work is on-going with Ex dc to replace the enclosed-break contents of 60079-15. This will leave the sealed and restricted breathing requirements for Ex nR either to find a new home, or to remain in a very much truncated 60079-15. A decision on this will not be taken for a few years.
The standard for Oil Protected Equipment is starting down the route of a quite radical transformation. The first edition of Ex o was never accepted in the UK for installation in Zone 1 and was restricted to Zone 2. The next edition banned normally sparking equipment under the oil and became acceptable in Zone 1. We are now splitting the requirements between Ex ob, for Zone 1, which will not allow most forms of sparking contact, plus Ex oc for Zone 2, which will allow sparking contacts. The first comment draft is now with national committees and provoking interesting discussion.
The intention is to run the update exercise for 60079-6 (Ex o) in parallel with that for 60079-5 (Ex q) so that they have a common revision cycle, but very few changes are expected for Ex q. Both standards have limited application but are very valuable to a few selected manufacturers.
The MT for 60079-31 are struggling with some of the comments received on the proposals for a new edition of the dust standard. There has been an agreement on reducing some of the difficult thermal testing in the current edition, but a fair amount of work is still needed to resolve all the comments relating to level of protection Ex ta.
The Chairman’s Advisory Group (CAG) at the end of the second week was an opportunity for all the various convenors, chairmen and secretaries to get together and share common problems, as well as to pass information among the IEC TC31 family. Since it is not a formal body within the IEC standards system, it can only make recommendations which subsequently have to be endorsed by the full committee, but nevertheless, it is a valuable opportunity to prepare for subsequent meetings.
The next round of international meetings will be held in Melbourne in October, when we will pick up the comments on the Ex s document (60079-33) which is currently out for comment. This continues to cause disquiet in some parts of Europe, where there is a fear that having such a standard will constrain some of the “free-for-all” aspects of the ATEX Directive. This is especially true where manufacturers have chosen to declare compliance directly against the Essential Health and Safety Requirements in Annex II of the directive, rather than following the conventional path of using existing standards as a method of showing compliance.
Baseefa’s managing director RON SINCLAIR is chairman of BSI Committee GEL/31, responsible for the UK input to both European and International standards for Electrical Equipment for use in potentially explosive atmospheres. He is chairman of Cenelec TC31 and also responsible for representing electrical standardisation interests at the European Commission’s ATEX Standing Committee. Since January 2009, he has chaired ExTAG, the Test and Assessment Group of the IECEx International Certification Scheme. Ron was awarded an MBE in the 2011 New Year Honours List for services to Certification and Standardisation.
In this regular column for HazardEx, he keeps readers up to date in developments in standards and also aspects of the IECEx Schemes.