When new directives hit the fan
22 February 2017
EN 14986:2017 entitled “Design of fans working in potentially explosive atmospheres” was issued in January. Although not greatly different in principle from the 2007 edition, there are enough changes to mean that most fans will have to be reassessed against the new standard before the 2007 edition loses harmonisation status.
At the time of writing we don’t yet have an update in the Official Journal, but it is likely that the de-harmonisation date for the first edition will be January 2020.
For the first time, the new standard recognises that the heat loss from an electric motor that is in the fluid stream might be relevant in allocating the Temperature Class.
To match permitted reductions in rotational clearances, there are enhanced requirements on the rigidity of the fan casing, and a greater emphasis on the ability to measure rotational clearances during routine maintenance. But the possible causes of casing distortion are treated with more care, including requiring that the installation and commissioning instructions should have a section detailing the maximum permitted loads to be imposed on the casing by any connected ductwork. Although many manufacturers may currently provide this information, there remains the possibility that this will also mean more work for fan installers.
In view of the greater emphasis on maintaining mechanical clearances, a relaxation has been permitted on materials of construction in that, for Category 3 fans up to a certain size and speed, it is no longer obligatory to meet the requirements for “spark resistant” material pairings.
Alternatively, for the same sizes of fan, if the accepted material pairs are used, it is not necessary to make provision for clearance measurement during routine maintenance. Neither relaxation applies to Category 1 or Category 2 fans.
The tables on permitted material pairings have been totally reconstructed. Most of the data remains unchanged, but it is difficult to compare the old and new tables as the previous notes following the table are now incorporated directly in the table, and the order changed. For example, the original Table 2 with separate notes comprised two pages. The new table, without separate notes, now takes six and a half pages, but requires less “back and forth” reading.
The five sub-clauses relating to: shaft seals; bearings; power transmissions; clutches and couplings, and braking systems, now no longer restrict the protection concept to “constructional safety”, but overtly recognise “liquid immersion” and “control of ignition sources” as valid methods of protection. The use of “control of ignition sources” – such as by incorporating thermal or vibration monitoring – is generally becoming more popular for many types of non-electrical equipment, so incorporation in the fan standard is welcome.
To match the enhanced requirements on rigidity, there are now enhanced requirements relating to the securing of the fan impellor to the shaft. The previous quarter page is extended to four pages, with drawings, making the requirements clearer.
To assist readers of the standard, a new Annex B has been added, tabulating which clauses in the standard apply to each separate category of fan. If you are familiar with either IEC 60079-15 or IEC 60079-11, you will have seen similar tables at the start of those documents.
But, of course, we have had the publication of EN ISO 80079-36 and -37 within the past year. This new fan standard now makes reference to the EN versions of these international standards rather than the previous EN 13463 series. Among the requisite changes are the requirements for a new way of marking the fans.
Since the ISO 80079 series of documents are also available for use by IECEx, this poses the interesting question: can EN 14986 form the basis of true international certification, even though it is a European Standard?
My judgement on this is to say: “Yes”.
My basis for so saying is that it is fully recognised that published material from any source can be used to back up the “Ignition Hazard Assessment” required by ISO 80079-36. In this context, EN 14986 is a perfectly-valid document to use to aid the Ignition Hazard Assessment.
The IECEx certificate will, of course, be against ISO 80089-36 and -37, but the assessment process and reports can clearly be used to support both the IECEx certificate and the ATEX documentation. Indeed, with the availability of the new standards, we foresee that more and more manufacturers will use IECEx documentation as the basis for their ATEX Technical File and EU Declaration of Conformity.
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 chairman of Cenelec TC31, represents electrical standardisation interests on the European Commission’s ATEX Standing Committee and chairs the IECEx Service Facility Certification Committee.