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The TC31 CAG Meetings

Author : SGS Baseefa Technical Manager Ron Sinclair

01 May 2019

In between the more formal plenary meetings of IEC TC31, the Chairman’s Advisory Group (CAG) meets as an assembly of all the convenors of standard Maintenance Teams (MTs), Project Teams (PTs) and Working Groups (WGs), in order to keep everyone informed about what is happening in the other teams, as well as to make recommendations to the chairman for the future development of the work.  

Because this is informal, the group cannot take any decisions, but makes recommendations for consideration by the individual MTs, etc., and by the plenary meeting that will be held later in the year.

Prior to the two-day CAG meeting, a number of the MTs. PTs and WGs met, taking the opportunity for synergy in meeting at the same time and at the same location.  On this occasion, the whole series of meetings lasted two weeks and involved over 100 people.  R. Stahl hosted the event at their Waldenburg facility, with attendees staying at a number of hotels in nearby Schwäbisch Hall, one of the more picturesque small towns in southern Germany.

The following is a short selection of items from the reports that might be of interest to readers of Hazardex:

WG27 (horizontal WG for electric machines across all protection concepts) highlighted the information in the current 60079-7 for the routing of conductors for temperature sensors in the machine winding.  This was done deliberately to avoid induction or capacitive coupling from the main motor winding and should be applied to all motors (Ex d, Ex t, Ex p, as well as Ex e), irrespective of whether or not the detector circuit is intended to be intrinsically safe, to minimise the chance of faults in the machine being transmitted down the temperature detector wiring.

WG40 (horizontal WG for luminaires across all protection concepts) is seriously concerned that in plants around the world, LED light sources are being retrofitted, without proper appreciation of the risks.  There have been incidents where such a retrofit lamp was fitted to a fluorescent luminaire and caught fire.  It is interesting that the IEC committee for industrial luminaires is also worried about safety risks with some types of LED products.

AG59 (the ad-hoc WG looking at potential alterations to requirements for portable and personal equipment, such as mobile ‘phones) suggested that the pseudo-lifetime tests, such as the high temperature/high humidity exposure could be reduced, as such equipment is more likely to see an actual life span of 5 years, rather than 20/30 years more typical of other equipment.  CAG expressed sympathy with the view, but wanted to see a more fully worked out proposal before saying it can go forward as an amendment to IEC 60079-0.

AG53 had been looking at solving the problems being caused by installers wanting to use threaded entry devices (glands, thread adaptors, etc.) with threads other than Metric or NPT.  The decision to restrict the type of entry thread had been taken a few years ago, but, particularly in East Asia and India, the available conduit is not normally suitable to be threaded with either of these threads, and the “G” thread is preferred.  CAG agreed with the recommendation of the AG that the entry threads in enclosures should remain restricted to Metric and NPT, but that there was potential for the use of a thread adaptor.  This could allow a “G” thread entry device to be correctly mated with an adaptor and then into the enclosure.  There is, however, one additional problem related specifically to flameproof enclosures.  A “G” thread, even if correctly mated with a “G” entry thread would seem to need to have seven threads engaged, compared with the five threads needed for Metric or NPT, in order to maintain the flameproof properties of the enclosure.  Never make assumptions about the possibility of making straight swaps in this type of circumstance.

MT 60079-19 expressed concern that IEC 60079-19 was being used within the IECEx Service Facility Certification Scheme to certify workshops carrying out repair work to non-electrical equipment.  As chair of the relevant IECEx scheme, I have a personal interest in this and was able to reassure MT 60079-19 that such certification only covered the non-electrical aspects that are key to the repair of electric machines, such as metal spraying of a shaft.  There is no current intention that such certification should cover techniques that are not outlined in the standard.  CAG recommended that MT 60079-19 and the relevant WG dealing with the non-electrical constructions standard (ISO 80079-36) prepare either an addendum to IEC 60079-19, or a separate standard, which would extend the capabilities that could be certified within the IECEx system.

About the author

SGS Baseefa Technical Manager Ron Sinclair MBE is chairman of BSI Committee EXL/31, responsible for the UK input to both European and International standards for Electrical Equipment for use in potentially explosive atmospheres. He is also chairman of Cenelec TC31, represents electrical standardisation interests on the European Commission’s ATEX Standing Committee and chairs the IECEx Service Facility Certification Committee.


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