Significant and controversial changes to explosive atmospheres installation and inspection standards.
01 October 2014
Recent updates to the two main IEC standards associated with electrical installations are the biggest changes in over a decade and will affect all new installations. All new installations should comply with the latest IEC or BS EN standards, and everyone associated with the design, selection, installation, inspection and maintenance of electrical equipment for use in explosive atmospheres needs to be fully up-to-speed.
As and when updates to the standards are introduced, it doesn’t make much of a ripple; the only people who are aware of the changes are the people who need to use the standards. The introduction of the IEC 60079-14 and IEC 60079-17 standards has caused and will continue to cause more of an impact, not so much a ripple but a large wave.
In some aspects the situation regarding the interpretation of the various clauses of the standards has been made clearer, however in others, the changes have made it less clear or, at worst, confusing. This is especially so with the UK introducing Annex NA which has introduced variability.
The aim has always been one global standard, but the UK is now out of step not only with Europe but also with the rest of the World. Annex NA is tucked away at the back of the standard (after the bibliography - which is normally the last item in the standard) and Annex NA is informative only.
The Installation and Inspection Standards, IEC 60079-14 and IEC 60079-17
The introduction of Edition 5 of IEC 60079-14 (Installation) and Edition 5 of IEC 60079-17 (Inspection and maintenance) introduced a number of changes. Both standards were published in November 2013. IEC standards are introduced into Europe as European Norms (Standards) or EN’s. In Europe we are mandated to use EN versions of the standards, which are issued by CENELEC (European Committee for Electrotechnical Standardization) to each member state of the European Union. Each individual member state will make a reference to the standard body associated with that particular country. In Germany, standards are prefixed DIN (Deutsches Institut für Normung), Ireland is prefixed IS (Irish Standard – not to be confused with Intrinsically Safe) whilst in the UK it is prefixed BS (British Standard) and so on.
In Europe the EN version of the standard 60079-14:2014 has to be implemented by 2nd October 2014 and the standard 60079-17:2014 has to be implemented by 24th September 2014.
United Kingdom Objections
BS EN 60079-14
In the UK, the updated standard was introduced as a BS EN version in June 2014, some 3 months after the EN version which came out in March 2014.
One of the most controversial changes from Edition 4 to Edition 5 of IEC 60079-14 was the removal of the flow chart relating to the selection of cable glands into Ex ’d’ (flameproof) enclosures. The familiar flow chart had been in the IEC 60079-14 standard since 1996 (Edition 2), this chart itself was previously in BS 5345-3:1989. In Edition 5 of IEC 60079-14, the chart was replaced with different selection criteria.
The selection chart was based on research carried out by ERA (now part of the EDIF group of companies) in the UK in 1975. The concern raised was that repeated ignitions inside a flameproof enclosure could damage the conductor insulation and inner cable bedding, within or immediately external to the cable gland, so as to cause a fault which could be a source of ignition to the flammable atmosphere. Tests were carried out by ERA on 3 and 4 core power cables (ranging from 2.5 mm2 copper to 185 mm2 copper) and multi-core signal cables. Cable lengths of 50mm and three metres were used, with the cable ends capped or uncapped.
Severe thermal damage was detected in many situations, particularly where multi-core cables were at an elevated temperature into enclosures greater than 2 litres. Thermal damage was more prevalent with Group IIA and Group IIB gases (higher calorific value) with subsequent flame transmission more likely if the atmosphere is Group IIC. The report, issued in April 1976, made six proposals which related to plastic and elastomeric insulated cables, the outcome was the familiar flow chart and the use of barrier glands and/or other sealing arrangements in certain specific conditions.
The UK committee have expressed serious concerns about the proposed changes to the requirements and voted against the revision of IEC 60079-14 to create Edition 5 at a number of stages during the formal process of change.
The UK Committee’s concerns are:
1. They are not aware of any safety issues relating to the use of the selection chart and the gland selection, since its adoption in the UK in 1989 and subsequent international adoption in 1996.
2. They have not seen documented evidence of any tests carried out to justify the removal of the selection chart and its replacement by the new selection procedure.
3. Verbal descriptions of recent tests seem to suggest that the tests only relate to ignitions through the cable.
4. The selection chart only applied to flameproof enclosures which contained a source of ignition in normal operation, but the new procedure now applies to all flameproof enclosures, previously junction boxes and indirect entry terminal boxes did not require barrier glands; however, unless the cable is at least three metres in length, a barrier gland will be required.
The new edition seeks to clarify the requirement for the cable to be at least three metres in length by referencing Annex E of the standard. Annex E is titled ‘Restrictive breathing test for cables’ and prescribes pressure drop tests with the cable connected to an enclosure. However, as this annex is informative, it is not clear whether cables will require testing to avoid the need for a barrier gland. The UK committee is of the opinion that such testing is not reasonably practicable.
UK users of BS EN 60079-14
Given the serious concerns expressed by the UK committee in relation to IEC 60079-14:2013 (Edition 5, Clause 10.6.2 b) throughout the whole revision process, they intend to submit a proposal to the IEC to amend Edition 5. Until such time as the situation is resolved, the UK committee recommend that users (in the UK) continue to consult the selection chart, which is reproduced as Figure 1 in Annex NA.
BS EN 60079-14:2014: The changes
BS EN 60079-14: 2014 has increased from 94 pages to 140 pages, an increase of 46 pages to an already complex Standard. The increase in the number of pages is due to the increase in the number of sections from 18 to 23 and the number of annexes increased from 9 to 13. They also now break down the documentation requirements into three distinct areas: site, equipment and installation.
Marking requirements have been updated, for example Annex ZB has been removed - this referenced ATEX categories . In the IEC/EN standard reference is only made to equipment protection levels (EPLs). There are also references to new equipment marking requirements with EPLs, e.g. ‘px’ has become ‘pxb’ and so on; so there will be a lot of new marking to become familiar with!
Initial inspections have been included in the installation standard specifically. It had been a requirement to carry out initial inspections, but it has always just been a reference to BS EN 60079-17. No more excuses - initial inspections have to be completed.
The requirements for light material for construction materials for dust are now in the main standard. Additional requirements for the control of static electricity are introduced, as well as better specifications for easy tear cables. Additional advice is given on cable entry systems (e.g. glands, adapters and blanking elements) and the recommendation is that glands even for intrinsically safe circuits have to be certified.
Clarification of enclosures for dust atmospheres cover thread entry. All rotating electrical machines are now in one section (section 11). Electric heating systems (trace heating) have been added to clarify that they are a ‘system’. Clarification has also been made that the conductor length in Ex ‘e’ enclosures is half the diagonal length of the enclosure; it was unclear in the previous version and people assumed it was the full enclosure diagonal length. The insulation test on cables has been amended from “500V insulation test” to “500V a.c. rms or 700V d.c.”
Type C cable has been specified for the intrinsic safety section, replacing what was identified as “other” type of cable. Use of increased safety enclosures on intrinsic safety system is recommended, which will ensure compliance with the creepage and clearance requirements for intrinsic safety. The use of blue terminals in enclosures has also been added, and ‘nL’ removed from the type ‘n’ section.
Annex C has been added regarding Initial inspections, identifying that an initial inspection must be completed after installation and prior to powering up the system. Requirements for installations in extremely low ambient temperatures (Arctic conditions) have been added, as well as requirements for installations of ‘op’ Optical Radiation. Permit to work guidance has been removed and finally for the UK only, National Annex NA has been introduced: this is the information that was in section 10.4.2 of BS EN 60079-14:2008 and is now informative only.
BS EN 60079-17:2014
IEC 60079-17 was introduced as a BS EN standard in March 2014, the same time as it became an EN standard. The changes from BS EN 60079-17: 2008 to BS EN 60079-17: 2014 version are:
* The number of pages remains the same at 37, however the changes that have been made reduce the number of check sheets. That said, the content of the individual check sheets has been extended.
* Clarification added regarding functionality of a system does not infer it is safe, and reference to Unmarked or illegible equipment marking labels are now covered, and fit-for-purpose documentation has been introduced for older non-certified equipment, while theenvironmental section has been expanded to list key elements to be aware of. Additional requirements for warning labels for non-intrinsically safe circuits have been introduced, and the trip time and percentage overload values have been removed, now referencing the IEC 60079:14:2013 standard. The Ex ‘t’ inspection table 4 has been incorporated into table 1 (e.g. Ex ‘d’, Ex ‘e’, Ex ‘n’ and Ex ‘t’. Finally, a specific sample checklist for motors has been introduced.
The Future of Ex Installations and Inspections
From the perspective of end-users (e.g., designers, installers and inspectors), the two standards of major importance are IEC 60079-14 Installation of electrical equipment and IEC 60079-17 Inspection and maintenance of electrical equipment. But we should also not forget IEC 60079-19 Ed 3 Repair and overhaul of equipment standard.
Will professionals in the sector take note of Annex NA, or will they feel that the IEC/EN standards should be followed as they are? And what will people do in other European countries and around the world? Some UK companies are foreign-owned and the decision on which standard to follow may be made elsewhere.
Ultimately the main question to ask is…… Is my installation safe and can I prove it! By the correct use of IEC (BS EN) 60079-14 and IEC (BS EN) 60079-17 the answer will be …….. YES!
About the Author:
Peter Roberts is the Site Services Manager for ExVeritas Ltd, and provides site safety services such as Area Classification, Ex Inspection and Risk Assessment.
Contact Details and Archive...