Snowtime at Windsor
31 May 2013
Little did the organisers imagine that choosing late March for two weeks of standards meetings in Windsor would land the participants in the middle of the UK’s freakiest-ever spring weather. Nonetheless, thanks to the hospitality of BSI at Chiswick and FM at Windsor, we had a very good series of meetings, often with five meetings running in parallel.
We finished with the Chairman’s Advisory Group (CAG) on the final two days, when the TC 31 convenors and team leaders met to review the status of all the on-going work.
Probably what will astonish most people who use our standards but who are not involved in writing them, is the statistics about the number of separate Maintenance Teams (MTs) that look after documents that are already published. These include Project Teams (PTs) which are busy on the drafting of new documents, and the various types of Working Groups (WGs) which either focus on a narrow activity or have a broader remit looking at common issues across more than one standard.
At the CAG, reports were received from 22 MTs, four PTs and 14 WGs, indicating just how busy the members of IEC TC31 are. I will not report on the work of the MTs at this time, but concentrate on selected PTs and WGs.
In the field of Intrinsic Safety, PT 60079-39 is working on a new standard under the working title of Power “i”. The intention is to extend the principles of Intrinsic Safety to the situation where an electronic circuit has enough inbuilt intelligence to be able to give a quick disconnect on any occasion where a dangerous level of current is taken by the circuit.
The “let-through” energy during the switching period has to be controlled to less than the minimum ignition energy for the gas concerned, so it does require some very fast acting components that would not have been available a few years ago. This is an example of how, as a standards community, we are trying to satisfy the needs of industry (in this case for more power in a circuit) as soon as the technology becomes available.
PT 80079-36, -37 and -38 are responsible for drafting the standards for non-electrical equipment that will provide the international versions of the European EN 13463 series. They had been hoping to report a successful vote on the drafts, but unfortunately, although the vote in IEC was positive, this was negated by the vote in ISO. These will be dual logo standards, so both international standards bodies have to take separate votes. With this extra delay, it is now likely to be the second half of 2014 before these important standards are published.
WG27 is a “horizontal WG” looking at aspects relating to rotating electrical machines across all of the standards. Much of the recent work has been taken up in providing advice on motors to MT 60079-7 that is rewriting the Ex “e” standard, but some important urgent work involved writing text for the repair standard 60079-19 to add flexibility in respect of copy-winding of Ex “e” motors, without having to adjust the tE time. It is another example of certification standards responding to the needs of industry.
Until you read the standards, many of which apply to both explosive gas and explosive dust atmospheres, you may not appreciate that none of the standards are wholly valid for where both gas and dust are present at the same time. These “hybrid mixtures” are the subject for work in WG 31, which is trying to assess safety factors that might be needed to ensure compatibility with such atmospheres.
The standard service conditions for Ex Equipment are -20C to +60C, 0.8 to 1.1 bar and about 21% oxygen in the atmosphere. WG 39 is looking at the effects of going radically outside these conditions and any necessary additional constructional and test requirements. This is becoming more important as oil and gas exploration moves to ever-colder parts of the world, but the group is also looking at the effects of continued high humidity for equipment intended to be installed nearer the equator.
And finally, in ad-hoc WG (AHG) 41, we are starting to get our heads around how to protect the high voltage feeds from shore to rig, bringing voltage levels well above 15kV into the frame for our standards. We are only concerned about the incoming cable and the supply side of the on-board transformer, but there are no established criteria for these voltages if they are present in a hazardous area. The odd discharge down a lengthy porcelain insulator is not a problem in conventional supply distribution, but it would be a recipe for a disaster on a rig if it were not protected in some way.