Guest columnist Stuart Hutchings, marketing manager at Bulgin, outlines the design challenges of creating equipment for use in hazardous areas
Designing equipment for use in hazardous areas is a relatively new discipline which can be traced back to the introduction of electrical equipment in the coal mining industry over 100 years ago.
While miners were aware of the risk of fires and explosions before this point, 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 advances 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 alone 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.
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.
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 assessment is not carried out on a simple ‘pass or fail’ basis and components must maintain integrity and performance at a range of temperatures.
This can be especially problematic with cold impact testing as many materials, such as thermoplastics, perform well at high temperatures but can become brittle and splinter or crack at sub-zero temperatures. This can be particularly frustrating for design engineers who find themselves limited in their choice of durable, flexible materials that are compatible with in-house tooling and moulding machines.
However, materials such as tough high grades of Polyester are ideal for use in hazardous area components, as they do not crack at lower temperatures.
While design engineers can choose simple component parts accredited by the ATEX directive in the assurance that they will perform well in hazardous areas, the strict rules of ATEX testing also extend to all parts of the connector system, such as the sealing caps used to maintain integrity when connectors are not mated. Here polycarbonate is often chosen as it has exceptional impact resistance at both cold and hot temperature extremes.
Of course, cost is still a key deciding factor for a design engineer with a limited budget when choosing component parts. There is a wide selection of connectors available for deployment in hazardous areas, from high-end metal of connectors for use in offshore production platforms in the Oil and Gas industries, for example – to lower cost, Zone 2 plastic connectors, which can typically be found in chemical, pharmaceutical and petrochemical industries.
Finally, design engineers should consider the specific needs of an end user. Simple adjustments can have a significant impact on the ease of use for the worker operating machinery and equipment in a hazardous environment.
An easy-to-access interface is essential for a worker who wears restrictive and heavy protective clothing because of the harsh nature of their work environment. Adding a simple design feature such as a ribbed casing on connectors is a straightforward modification but one which is easier for a worker to manoeuvre with a gloved hand. In addition, modifications like this will also extend the life of associated cabling and other attachments, as the easily operable interface will be subject to less abuse. It is considerations such as these which assist a design engineer in judging the merits of a particular component over the alternatives.
Standards continue to improve in design engineering, with the changing and growing market for hazardous area equipment; working with experienced custom design houses will assist companies in finding components and/or creating tailored engineering solutions to meet their evolving needs without compromising on cost or performance for workers in hazardous environments.
www.bulgin.co.uk