18 Jul 2011

Designing Connectors for ATEX

Dave Ferry, Design Engineer with Bulgin, discusses the issues faced by engineers when designing and manufacturing equipment suitable for use in hazardous areas.

Designing equipment for use in hazardous areas can be traced back to the introduction of electrical equipment in the coal mining industry over 100 years ago. Miners were clearly already aware of the risk of fires and explosions before this point, but the introduction of electrical signalling and lighting systems presented new challenges where sparks from electrical equipment would ignite the highly dangerous and volatile methane gas emitted during the mining process and potentially cause a fatal incident.

Despite advancements in engineering and a greater understanding of the nature of flammable and explosive materials today, the basic principle of hazardous area remains the same. Whereas a domestic electrical appliance may emit a harmless, visible spark when turned on or off without concern, in a setting where flammable or explosive dusts, gases, vapours or liquids are found a spark becomes a far more serious concern. The list of typical scenarios where electrical equipment is operated in hazardous areas includes petrochemical industries, paint and ink manufacturers, mills and grain stores, timber mills, chemical treatment facilities as well as public spaces such as airports.

One only has to consider the implications of a serious safety breach in hazardous areas to realise how important it is for design engineers to develop safe, efficient equipment built with high performance component parts. In the past year we have seen the world's media broadcast headlines discussing disasters in the petrochemical industry which have caused severe damage to the environment, a huge drop in revenues for the companies concerned and, most tragically, loss of human life. More recently in the news was the accident that occurred at Apple’s main manufacturing contractor Foxconn’s factory in Chengdu-China. At least 2 people were killed and 16 injured by an explosion which was reportedly caused by ultra-light dust.*

In order to try and prevent these sorts of accidents in the future it is essential therefore that design engineers work with reputable suppliers to develop safe and efficient equipment using the highest standard component parts.

ATEX legislation

In 2006 the EU introduced the ATEX directive which outlines stringent criteria to offer adequate protection to workers operating equipment in hazardous areas. All equipment and component parts deployed for use within hazardous environments in the EU must meet exhaustive testing standards to assure high performance in work environments where there is a risk of explosions, fire or extreme temperatures. Equipment introduced before this time can undergo retrospective testing to show it is suitable for its purpose and gain accreditation.

ATEX cutaway

Rigorous testing is required for all component parts before the EU will issue a certificate of approval to permit manufacturers to display the ratings seal on their products. Often, the most arduous step in the testing process is assessing materials to ensure they maintain integrity under extreme temperatures. This testing stage is not carried out on a simple pass or fail basis and components must maintain integrity and performance at a range of temperatures - from sub-zero to extreme heat.

Temperature sensitivity

More often than not, cold impact testing is the more challenging test as materials such as thermoplastics tend to perform well and maintain integrity at high temperatures but can often become brittle at sub-zero levels. The challenge faced by many design engineers is choosing from a limited selection of durable and flexible materials that are also compatible with their exisiting in-house tooling and moulding machines. Bulgin has found that tough, high grades of UL94V-0 rated Polyester are well suited for designing component parts for use in hazardous area equipment as this material tends not to crack at lower temperatures and also maintains performance and integrity at extremely high temperatures. This becomes particulaly relevent when the heat rise from the connector passing the rated current is taken into account – typically a 25˚C headroom is needed above the maximum rated ambient temperature.

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About the author

Dave Ferry is a product design engineer at Bulgin. He has been with company for 14 years and has extensive knowledge of ATEX legislation and experience in designing products for hazardous are equipment. Dave was involved in the development of Bulgin’s EXPlora series of ATEX approved connectors. During his 24 year career Dave also spent 9 years at Colvern designing sensors for the automotive industry, including Range Rover height sensors and Getrag gearbox sensors.

Elektron Technology, owners of the Arcolectric, Bulgin and Sifam brands, designs and manufactures products for connectivity, environmental sealing, switching, illumination and indication and supplies globally into a wide range of applications and industries. With expertise, experience, flexibility and an innovative approach, Elektron Technology can provide custom functional modules to achieve substantial savings in development time and production costs for its customers.

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