ITACS OD 021 Prior to the 2004 IECEx

ITACS OD 021 • Prior to the 2004 IECEx meetings in Slovenia it was reported that their appeared to be a difference in interpretation of the requirements of the Intrinsically Safe Standard IEC 60079 -11 Edition 4 between the different test laboratories. • At the Ex. TAG meetings in Slovenia in 2004 the Ex. TAG committee, identified the need for a guidance document for use by Ex. TLs and Ex. CBs when conducting assessments of apparatus and systems utilising the Intrinsically Safe (IS) technique of explosion protection. • Ex. TAG WG 08 was established to produce a document for submitting to the Ex. TAG meetings in UK in 2005.

ITACS OD 021 • The original WG 08 team consisted of “volunteers” from Australia, Denmark France, Germany, USA and UK. • The proposed document was based on IEC 60079 -11 Edition 4 not the draft version of Edition 5 as at the time the Intrinsically Safe Standard was undergoing some significant changes.

ITACS OD 021 • At the 2005 Ex. TAG Buxton meetings document Ex. TAG/74/R was submitted for review. • This document had a six queries highlighted that WG 08 requested the IS Maintenance Team feedback on. Feedback was received on several points from members of the MT and incorporated in to the document. • The original document was published in January 2006 as OD 021 • The convener would once again like to thank all members of WG 08 for their time and effort in producing the document within the agreed timeframe.

ITACS OD 021 Since publication request for changes to the published OD 021 came from SG 31 G these changes effect the following clauses of OD 021; – Clause 4. 2. Capacitive Evaluation – Clause 5. 2. Inductive Evaluation. – Clause 7. 2. Thermal Evaluation • Following these requests for changes a small group comprising of the Chairman of TC 31, the convener of the IS MT and the convener of WG 08 was held on 29 th May 2006 following this meeting changes where made to OD 021 and circulated to the individuals who requested the changes and to WG 08 members for their review. • The revised document was then published as OD 021 V 2 in July 06. • It is also noted that the UK has presented a paper of comments Ex. TAG-96 -CC on OD 021 V 2 and these comments have not been addressed in this presentation.

ITACS OD 021 Clause 4. 2 Capacitive Evaluation • Concern expressed over equivalent circuit shown in figure 1 • Reference to increased voltages has been replaced by reference to the relevant clause in the standard. • Clarification has been added that V 1 is greater than V 2. • Resistor R 1 now identified in figure 1. • Review of changes to OD 021 V 2

ITACS OD 021 Clause 5. 2 Inductive Evaluation • Concern expressed about the additional voltage due to forward voltage drop across the diode. • This clause has been modified so it only now refers to zener diodes • Review of changes to OD 021 V 2

ITACS OD 021 Clause 7. 2 Thermal Evaluation • The main issue with this clause was the “suitability” of the encapsulation for thermal evaluation. – The bulk of this clause has now been removed. However, it should be noted that even Edition 5 clause 6. 6 is still vague on how damage to encapsulation from high temperatures should be assessed. – OD 021 V 1 had highlighted this as an issue and was waiting for a ruling from the IS MT. • Review of changes to OD 021 V 2

ITACS OD 021 Clause 7. 2 Thermal Evaluation • Concern over temperature evaluation on capacitors. • This has been changed to now only draw attention to conditions when electrolyte and tantalum capacitors. • Concern over temperature evaluation on hot spots of windings etc. • Reference to hot spots deleted Review of changes to OD 021 V 2

ITACS Future Items • The following suggestions have been received for inclusion in the next version of OD 021; – Up date required to take in to account IEC 60079 -11 Edition 5. 0 – Inductors used in dc – dc converters – connection of unspecified equipment to portable IS equipment in a safe area for the purposes of battery charging / downloading data / uploading data. – SIM Cards – IS Systems – Capacitor isolators? ? – Any more? ? – Surface temperature evaluation on surface temperature of components included in OD 21.