System solutions for application-optimised explosion protection

27 February 2017

Mastering the increasingly complex explosion protection technologies requires expert knowledge, which is leading to increasing reliance on single source solutions, according to Thomas Kasten.

The safe prevention of an explosion, or minimising its potentially dangerous consequences, is a complex task which requires in-depth knowledge and experience. 

Today experts and engineers at Pepperl+Fuchs are active in many standardisation organisations and technical committees – for example helping to shape IEC 60079 which internationally defines the basic requirements for explosion protection. Prior to its adaption for the European Union in April 2016, it was directive 94/9/EU (ATEX 95) which has since been succeeded by directive 2014/34/EU. 

A variety of national and international standards define the types of protection, zone classifications of hazardous areas as well as requirements relating to installation, maintenance and repair. Most types of protection within hazardous areas require the use of specially designed equipment and associated apparatus. Among those are increased safety Ex e (IEC 60079-7) and intrinsic safety Ex i (IEC 60079-11). 

Equipment not specifically designed for use in hazardous areas can be protected by placing it inside a pressurised enclosure, Ex p (IEC 60079-2), or flameproof enclosure, Ex d (IEC 60079-1) while protection against dust ignitions can be achieved by protection by enclosure, Ex t (IEC 60079-31).

All these details on international, regional as well as company-internal safety regulations also need to be aligned with the requirements of specific applications. Pepperl+Fuchs offers components in all types of explosion protection and has the expertise to combine these with further functionality to meet specific application requirements. 

Solution Engineering Centres
Pepperl+Fuchs’ Solution Engineering Centers (SEC) provide the expertise to develop specific solutions in cooperation with customers. An SEC is able to manage all stages of a project – through parts procurement, manufacturing to commissioning. 

Intrinsic safety, Ex i, allows field devices and signal transmission components to be maintained or exchanged without process shutdown. By limiting the power in each electrical circuit a possible arc or spark is kept below the ignition energy of the surrounding gas atmosphere. However, this results in limited energy to feed loop-powered devices.

However, components or devices not designed according in accordance with any levels of protection to prevent the occurrence of sparks, need to be protected when used in hazardous areas. There are two options. Pressurisation, Ex p, contains the potential ignition sources inside an appropriate enclosure and keeps any explosive gas mixture on the outside by means of overpressure. A continuous flow of inert gas must be guaranteed by reliable control and monitoring methods. Flameproof, Ex d, in contrast, contains a possible explosion inside a sturdy enclosure without the need for active control elements and pumps. Suitably designed flame paths prevent the egression of the flame. The outer surface of the enclosure must never reach the ignition temperature of the surrounding gas atmosphere.

Lighting or power distribution networks and control of machinery which requires more energy than possible with Ex i can be achieved by increased safety, Ex e. Pepperl+Fuchs offers several modular product series of terminal boxes and control. The modular concept of Ex e certified components – from terminals, pushbuttons and LED indicators through control switches with various switching positions and contact configurations to potentiometers and measuring devices – in conjunction with several enclosure variants, offers a multitude of configuration options. 

With solutions incorporating non-certified components, adherence to the relevant equipment standards can be guaranteed by the SECs. Once the solution is in operation the user needs to consider the regulations regarding testing, commissioning and maintenance of electrical installations in hazardous areas. These are defined in IEC 60079-14 and -17. Especially with Ex d special care is mandatory when working on the enclosure or closing the enclosure cover. Therefore a combination, with a connection chamber in Ex e, is convenient. Both enclosures are mechanically connected by a particular flange, specific line bushings are utilised for cable entry into the Ex d compartment.

Thomas Kasten is product marketing manager for Systems+Solutions at Pepperl + Fuchs GmbH.

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