AEMT - Association of Electrical and Mechanical Trades

29 April 2022
ATEX Fans: An Explosive Issue
Air movement specialist, Axair Fans, explains the steps needed when specifying and sourcing fans for use in potentially explosive environments.

Outside of major users such as chemical, petrochemical and process industries, enquiries for flameproof fans tend to come from specifiers, resellers and end-users, many of whom may not be aware of the ATEX Directives.

ATEX is an acronym derived from the French expression ATmosphères EXplosibles and exists in the form of two European directives for controlling explosive atmospheres. The first ‘equipment directive’ 94/9/ EC (ATEX 100) covers manufacturing standards. The second ‘workplace directive’ ATEX 99/92/EC (ATEX 137) seeks to ensure that people are protected against the risk of blast injuries or asphyxiation by dangerous substances. The 2016 updated legislation is Directive 2014/34/ EU and assists with establishing a uniformity to the approach taken when supplying and distributing equipment such as industrial fans for explosive atmospheres.

Everyone involved in the specification, manufacture, installation, and use of equipment in flameproof zones has some responsibility in ensuring that the law concerning flameproof equipment is upheld.  

Unfortunately, a lack of practice with the subject tends to give rise to enquiries that begin with statements like “there is a slight risk of explosion, but we don’t think we need a flameproof fan”, which places manufacturers and suppliers in an awkward position because they are not ATEX consultants and are not qualified to know what the client can lawfully install.

What can the fan supplier do with casual enquiries that must at some point turn into tightly specified orders?

The first option is a blunt “come back when you know exactly what is required” and the second is to issue a questionnaire, usually with tick boxes and a bit of guidance appended, which may then be returned with conflicting selections

What is needed in every case however is an ATEX code that provides a well-defined minimum standard for the product that is required. For example, the code Ex II 2G IIC T4 essentially means European flameproof, surface industry (not mining), Category 2 (Zone 1), gas group II, type C (hydrogen or acetylene gas), maximum surface temperature 135ºC. It is strictly the responsibility of the end-user to perform a DESEAR (Dangerous Substances and Explosive Atmospheres Regulations 2002) risk assessment to ensure that flameproof zones are properly defined in terms recognised by ATEX 99/92/EC. It is recommended in 99/92/EC that an Explosion Protection Document be produced, which will help to define the ATEX code for any equipment to be installed in the flameproof zone. 

There are many other coding permutations, including slightly different formats for dusty atmospheres (Zones 21 & 22). If codes cannot be provided there is lingering uncertainty over what is required.

Once an ATEX code has been established by the end-user, the process of selecting a fan model and its essential features demands a degree of application knowledge. For example, the type of electrical supply is important. Often the response to “what electrical supply do you have”, is “can be single- or three-phase”. Single-phase is an expensive option and not widely available from ATEX motor manufacturers. It may be cheaper to run a 3~ line than to buy a ~ fan on a long manufacturing lead-time.

Any fan motor that is to be speed controlled with a VSD must also have thermistors fitted to protect against motor shell temperature at low speeds causing spontaneous gas combustion. By not mentioning the VSD aspect at the enquiry or order stage the purchaser is likely to ultimately face time and product replacement costs.

Other matters include motors that vary from the most secure specification EEx d (explosion proof) through EEx e (increased safety), down to EEx nA (non-sparking) which has many similarities to a standard non-flameproof motor. ATEX must be understood as being an ever-evolving subject requiring competence and training. Anyone requiring a better understanding of flameproof requirements would be advised to source training which is available from a wide range of industry bodies and organisations.

www.axair-fans.co.uk

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