Emerald Group Publishing Limited
Copyright © 2004, Emerald Group Publishing Limited
New ATEX directive
New ATEX directive
Keywords: Explosives, Hazards, Pneumatic equipment, Actuators
Previous hazardous environment standards focused on the more obvious sources of potential ignition posed by electrical devices. Many machine builders chose to use pneumatic logic and actuation to save the time and costs required to correctly install Intrinsically Safe or Explosion Proof electrical devices. However, ATEX has a far wider scope than the previous standards and encompasses the complete system including mechanical and pneumatic devices.
As a consequence of the new standard, builders of machines to be operated within explosive hazard environments are now obliged to source ATEX certified mechanical components. All pneumatic and mechanical components that require ATEX approval have had to be certified by approved bodies to check that precautionary measures have been taken to protect against hazards arising from mechanical sources of ignition. These can include: hot surfaces resulting from friction and compression, adiabatic compression, electro-static build-up and discharge and mechanically generated sparks caused by impacts. This has necessitated changes in design and materials in some components.
The challenge for the machine designer is to ensure that not only have certified components been used but that the completed assembly also complies. As in the CE EMC legislation the fact that all the components of a system are ATEX approved still means that you have to approve the complete system.
Not only does the ATEX directive apply to new systems but within 3 years, every system installed before July 2003 that uses non-approved components will need to be scrutinised and a risk assessment carried out, to ensure that it is suitable for continued use in a hazardous environment.
Evidently the implications of ATEX are far reaching and affect the end-user as much as component manufacturers. The onus is firmly on the end-user to determine the level of hazard to ensure that they get equipment certified as safe for use in that category (formerly zone) area. As with the former Ex legislation, the component vendor is not permitted to make the decision as to the category or risk, nor is the machine builder. Ultimately, the end-user must define the category for the machine builder, and then the machine builder must specify the correct components for conformity.
Typical pneumatic components that need to be approved under the new ATEX directive include standard rod-type drives, rodless cylinders, pneumatic power valves and shock absorbers. Some products when being assessed are discovered to have no hazard because of the materials they are constructed from and their operation. These products can be used in the hazardous area as long as they are used in accordance with the manufacturers' instructions.
Plastic tubing is one example. Although this does not need a Declaration of Conformity when it is built into a cabinet with ATEX components, thought must be applied to bundles of tubing. Whereas in a non-hazardous cabinet ten tubes may have been bundled together – in an ATEX cabinet this could cause a static hazard so maybe three groups or routings of tubing will be necessary to enable the cabinet to be assessed as safe.
To answer customer queries on the new directive, Festo has produced a booklet entitled “Pneumatic Products and Explosion Protection” that is not just specific to its own products but which explains the legislation, and details how to decipher the new “Ex” markings. It also explains the EU legislation as well as the meaning of the 94/9/EC directive in local-language for each EU country. There is also a useful glossary of terms and wall chart to assist in product selection. The booklet is available to anyone directly from Festo or as a PDF download from the Festo Web site at: www.festo.com.