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Jim’s springtime swansong

Author : Ron Sinclair

02 May 2014

For two weeks at the end of March and the beginning of April, PTB in the German city of Braunschweig hosted a series of IEC TC31 standards meetings.  As the weather turned warmer – we had rain on only two days – we saw spring arrive as the leaves on the trees unfurled.  

The Braunschweig delegates. Jim Munro is in the centre of the front row.
The Braunschweig delegates. Jim Munro is in the centre of the front row.

Every year at this time, the TC31 community takes the opportunity to hold a number of different Maintenance Team meetings (each related to one of the standards in the IEC 60079 series) followed on the last two days by the Chairman’s Advisory Group (CAG) meeting. 

As participants come from all over the world, including a number from Australia and North America as well as from across Europe, the holding of multiple meetings in the same location reduces total traveling time and costs.  Nearly two hundred delegates attended 34 separate meeting days in seven separate meeting rooms over eight days  before the final two days, where 28 representatives from the various activities met as the CAG.

The main purpose of the CAG is to ensure that the whole TC 31 community knows what is happening across the field of disparate standards, thus ensuring cross-fertilisation and the best use of resources.  This event was both a great success and, at the same time, a slightly sad occasion, as it was the last formal meeting of TC 31 where Jim Munro presided as chairman.  After 15 years in the post, Jim is standing down in response to changes in IEC rules which prevent him seeking an extension to his period in office.  All those who know him regret this change in the rules, as Jim has made, and continues to make, such a vital input to the development of TC 31 standards.  He will not disappear from TC31, but he is leaving rather large shoes to fill in the role of chairman.

Those of us in the motor working group held our particular meeting in the PTB laboratory, which performs research into motor related issues. We witnessed comparable tests on a sample motor, demonstrating the effects of using filters with variable speed converter drives, and also the change in temperature rise that could occur by increasing the voltage supply to the converter without changing the nominal output from the converter to the motor.  This is related to the hysteresis loss in the iron as it saturates and the higher input voltage to the converter will increase the saturation levels at the peak of each converter pulse. 

This is all part of the ongoing work to establish a basis for deciding on the comparability of converters so that we can remove the requirement that each motor/converter combination needs to be tested.

We also agreed that there was no need to invoke the upcoming non-electrical standards (to be ISO 80079-36 and -37, based on the European EN 13463 series) to cover fans and bearings on the motor, as the electrical standards, in conjunction with the manufacturer’s instructions for maintenance, cover all aspects.

The group looking at issues related to the application of batteries across all explosion protection concepts has expressed concern about the stability of certain lithium/ion cells and batteries, particularly those involving the nickel, cobalt, aluminium chemistry, and are considering if their use should be banned in hazardous areas.

New work that has just started includes a study of what might be required to allow higher voltages to be used safely in hazardous areas.  There is an increasing need to consider voltages above the 15kV limit that currently applies, particularly in order to provide shore-based power to off-shore installations. There is nothing fundamentally against higher voltages in the Ex o concept, but there is the small matter of how you make the connection in the HV circuit, since the option of large porcelain bushings is not available.

In one of the reports on non-electrical equipment, we learned that proposals are being formulated for standardisation at international level of internal combustion engines for use in hazardous areas. The new work is intended to include spark-ignition engines as well as the diesel engines currently covered in the out-of-date European standards.

Although there will be a few intermediate meetings of individual maintenance teams, the next major series will be in Chicago at the UL laboratories towards the end of October. By that time, we will have elected our new chairman.


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