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ATEX

What is ATEX?

What can cause an explosive atmosphere?
The three things that could cause an explosive atmosphere:
1) The atmospheric oxygen.
2) An inflammable substance (Dust, gas, mist, vapours or fibres).
3) A source of ignition: Electrical apparatus, installation or any source of heat. 

 A source of ignition could vary from: A spark or flame, as well as an increase of the surface temperature of an electrical apparatus that has the potential to generate an explosion if it exceeds the ignition temperature of the present gas/ substance.

 Some explosive atmospheres can be gaseous. A gaseous explosive atmosphere is caused when there is a mixture of air and inflammable products such as gases, vapours or fibres. This mixture of air and inflammable products would allow the combustion caused by an ignition to propagate through the entire mixture.

 To summarise, an explosive atmosphere can be cause by:
The atmospheric oxygen (always present) + An inflammable substance + A source of ignition = An explosive atmosphere.

 The dangerous substances and explosive atmospheres regulations 2002 (DSEAR) places duties on employers to eliminate or control the risks from explosive atmospheres in the workplace. 
According to these regulations an explosive atmosphere is defined as: 
"A mixture of dangerous substances with air, under atmospheric conditions, in the form of gases, vapours, mists or dusts in which, after ignition has occurred, combustion spreads to the entire unburned mixture."
More information on DSEAR can be found here:
The ATEX directive
ATEX brings together two European directives for controlling explosive atmospheres.

The ATEX directive requires equipment and protective systems intended for explosive atmospheres to be designed and manufactured to minimize the occurrence and limit the severity of accidental explosions. 
It applies to: 
  • New equipment that is intended for use in explosive atmospheres such as electrical components and apparatus and machinery. 
  • separately supplied protective systems for controlling unavoidable explosions in explosive atmospheres such as explosion vents, suppression systems. e.t.c    
'Equipment' is capable of igniting an explosive atmosphere under normal or faulty conditions. Equipment is divided into two categories: Electrical and non-electrical.
The procedures that a manufacturer would have to apply to a product are defined by the articles and other annexes of the ATEX directive. The procedures get stricter and more notified body involvement is required when there is a greater risk of an explosive atmosphere. There are also requirements given for the government to implement and enforce the directive.

Equipment and protective systems that comply with the ATEX directive can display a Ce and Ex marking: although components dont bear the Ce marking. To provide greater detail as to what the equipment is suitable for, more markings will be used in order to form a code which will define the category and suitability of this piece of equipment for different types of explosive atmospheres. A declaration of conformity would be required to show that the equipment is qualified and suitable.
The ATEX directive scope for equipment, both electrical and non-electrical:
  • Separately supplied protective systems for fitting to equipment to control unavoidable explosions such as explosion vents, suppression systems etc.
  • Safety device, controlling device and regulating devices contributing to the safe functioning of equipment and protective systems the de-energise equipment.
  • Components (items essential to the safe functioning of equipment and protective systems but with no autonomous function) Such as electrical components.
  • Products designed and manufactured for 'own' use are not excluded from the requirements of the ATEX directive.
  • Equipment first used outside of the European union and imported after the 1st July 2003: The directive applies to equipment at the moment that it is placed on the European market; Products maunfactured outside the European union and successively imported (whether as new or as used equipment) must comply with the directive. This duty is place on the first importer into the Union market.
Exclusions:
Some products are formally excluded from the scope of the ATEX directive; because other directive and rules apply:
  • Medical devices
  • Personal protective equipment - PPE
  • Domestic gas appliances
  • Equipment used for transport by sea, air, rail or road
  • Equipment using explosive products
  • seagoing vessels and mobile offshore units together with equipment onboard such vessels or units
Some more common exlcusions, that are not specifically listed:
  • Atmospheres without air 
  • Internal parts of equipment outside the ambient pressure and temperature range (0.8 BAR to 1.1 BAR and -20°C to 80°C)
  • Unstable chemicals and explosives
  • International waters are not part of the EU but the North sea and the continental shelf are European waters covered by CE marking
  • Equipment without its own potential source of ignition where no protective measures are required such as: 
  1. Mechanisms with a friction speed <1m/s
  2. Mechanisms with low energy impacts between low spark materials 
  3. Static discharge not generated by the equipment itself 
  4. Hot surfaces where overheating is impossible.
  • Equipment where an explosive atmosphere is reliably avoided such as: 
  1. Combustion equipment with frame monitoring that shuts off the gas supply
  2.  Adequately, reliably ventilated areas such as fume cupboards and solvent dryers covered by EN 1539 
  3. Vessels and enclosures purged with gas to avoid an explosive atmosphere. although enclosures pressurised according to Ex 'p' concept are covered by the directive. 
The new ATEX directive 2014/34/EU came into force on 20th April 2016.
The effects of the new directive:
  • More explicit requirements for trace-ability of products and supply chains as well as the roles of 'economic operators' i.e. Manufacturers, authorized representatives, importers and distributors. This is to help the market surveillance authorities.
  • The titles of some of the documents have changed - EC Declaration of conformity and EC type examination certificate becomes EU Declaration of conformity and EU type examination certificate respectively.
  • A new list of formal administrative requirements relating to CE mark, declarations and markings to improve trace-ability.
  • More commonality of jargon across the CE marking directives.
Changes that do not affect manufacturers are:
  • Greater market surveillance. 
  • New rules for the accreditation of notified bodies.
To read the full ATEX directive, follow the link here:
http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32014L0034
We will be following this blog up with more information on ATEX and other safety measures that have been implemented and how products need to conform to the standards.

You can view the V-Flow Solutions line of ATEX solenoid valves here:
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We will be covering different types of valves in future blog posts.
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