John Allen
Representing EASA on IECEx Committees
Sheppard Engineering Ltd.
Solihull, United Kingdom
Part One of This Report Appeared in the June 2020 Issue of Currents.
October: TC 31 Meetings in Nanyang, China
Working Group (WG) 27 held a two-day meeting and reviewed comments from committee members on IEC 60079-7 (Ex “e”). The latest draft of IEC 60079-0 and its Annexes were reviewed. Since IEC 60079-14, selection, design and erection of fixed electrical installation was ongoing, the committee proposed the inclusion of an Annex relating to EMC and safety related aspects of converter installations.
When the requirements for IEC 60079-15 (Ex “n”) (no arcs and sparks for use in Zone 2, specifically Ex “nA” electric machines) were transferred into IEC 60079-7 in 2017 as Level of Protection “ec” machines, the requirement for pre-start purging ventilation ports created a mismatch with the previous requirements from IEC 600790-15. Pre-installation, incendive sparking during starting and site risk assessment following the requirements of IEC 60079-14, which in earlier editions had been in IEC 60079-7 and IEC 60079-15, may require Ex “ec” electric machines to be purged before starting. However, mandatory requirements for purging ports for Ex “ec” machines had been omitted. The committee agreed that the ports were required and need to be included as a mandatory requirement.
The maintenance team for IEC 60079-7 held a three-day meeting. My concern was a requirement that I had previously proposed relating to minimum air gap had not been clearly addressed in the latest draft of IEC 60079-7. IEC 60079-7 and IEC 60079-15 have the same requirements for minimum air gap required to prevent rotor to stator impact.
There are three options:
A. Measurement of the gap (not possible intotally enclosed machines)
B. Calculation of the minimum gap
C. An empirical formula based on dimensions and speed
Service facilities can only use method C. However, the manufacturer may have used methods A or B with an effective airgap smaller than the empirically calculated air gap.
EASA members in the United Kingdom raised concerns that they may have been condemning machines (scrapping), which in reality are safe to use, because the air gaps they were determining, from measurement of the Ex Equipment, produced gaps smaller than the minimum air gap from method C) empirical calculation.
WG 27 previously recommended that when the air gap used by the manufacturer is smaller than the method C) empirical calculation, this became an “X” Special Condition of Use requirement, and the airgap should be provided in the manufacturer’s instructions.
During this meeting, the committee agreed the reduced air gap information should be either on the certificate or the nameplate, and a decision would be made on which at the next maintenance team meeting in Northbrook in March 2020 (This meeting did not take place due to COVID-19).
The TC 31 and I discussed convenor 2 errors in the published issue 4 of IEC 60079-19, which had been offered for sale a week before the meeting. Since no copies had been sold at that time, we reached an agreement with the IEC editors to make the final two amendments to IEC 60079-19, and the amended document was approved for publication. This document has a new requirement that service facilities working to IEC 60079-19 must take into consideration the requirements of IEC 60034-23 rotating electric machines – repair, overhaul and reclamation for industrial machines.
December 2018 + April 2019: TC 31 Project Meetings
The TC 31 project team met in Tonsberg, Norway in December 2018 and Amsterdam, Netherlands, in April 2019 to develop requirements for competence of persons working in or associated with hazardous areas and prepare a committee draft of a technical specification IEC TS 60079-44.
After circulation in October as a committee draft to all TC 31 National Committees, this draft TS has been returned to the project team for further work before recirculation as a new committee draft. This document includes requirements for competency of personnel in service facilities repairing or overhauling Ex Equipment to IEC 60079-19.
This report from John summarizes the highlights of his IECEx activities for the second half of 2019. The first part of his report appeared in last month’s issue.
John Allen represents EASA on the IECEx subcommittee related to IEC 60079-19, the repair standard for hazardous location motors and generators. Tom Bishop, P.E. represents EASA on the maintenance team (subcommittee) for IEC 60079-1, which deals with manufacturing. This report was submitted by Tom Bishop, P.E., on behalf of John Allen.
Print