Containing explosions

The Ex sector can rely on IECEx testing and certification for explosion prevention

By Claire Marchand

More than a century ago, the introduction of electrical apparatus for signalling and lighting in coal mines provoked many electrically-induced explosions of flammable gases and dust. Consequentially, specific types of protection were developed to prevent explosions by eliminating contact between an explosive atmosphere and an ignition source.

Explosion-proof CCTV camera
Explosion-proof CCTV camera (Photo: R. Stahl)

Not just for oil and gas

These protection methods benefitted mining operations but were soon extended to many other industries, oil and gas in the first place. But the risk of explosion exists in a variety of other sectors, such as transportation – including aerospace – furniture manufacturing, automotive manufacturing and repair, pharmaceuticals, food processing, grain handling and storage, sugar refineries.

Today the use of explosion-proof equipment for hazardous areas is mandatory in most countries around the world and is often included in national or regional – European Union - legislation. The number of accidents in explosive atmosphere is low.

Specific types of protection

Standardization has played a major role in the development of explosion-proof equipment for the Ex sector. IEC International Standards prepared by IEC Technical Committee (TC) 31: Equipment for explosive atmospheres, and its Subcommittees, in particular, have helped manufacturers worldwide in designing and producing safe systems, equipment and components.

As part of the IEC 60079 series of International Standards on explosive atmospheres, several publications provide specifications for the different types of protection used in Ex areas. These include:

Flameproof protection “d”

This type of protection is an enclosure in which any parts that may ignite in an explosive atmosphere are placed. The enclosure has the internal strength required to withstand the pressure that will develop if a mixture explodes. A second characteristic of this form of explosion protection technique is that this type of enclosure prevents the flames from the internal explosion from transferring to the explosive atmosphere surrounding it. When incorporated with an appropriate IP rating, such enclosures may also protect their internal components from adverse environmental elements like humidity, dirt, dust or water. This type of enclosure prevents the explosion from transferring to the explosive atmosphere surrounding it.

Encapsulation protection “m”

Encapsulation is a type of protection in which the parts that can ignite an explosive atmosphere are enclosed in a resin. The resin must be sufficiently resistant to environmental influences so that the explosive atmosphere cannot be ignited by either sparking or heating, which may occur within the device. This is used with electronic devices.

Increased Safety - Protection “e”

Explosive mixtures can penetrate the enclosure but cannot be ignited.

Hermetically Sealed

The arcing components of the switch are encased in a glass tube. The connecting wires are fused to the glass sealing the unit to prevent any ingress of flammable gases.

Oil Immersion - protection “o”

The electrical equipment is immersed in a protective liquid to prevent the ignition of the potentially explosive atmosphere above the liquid or outside the enclosure.

Pressurized protection “p”

This type of protection prevents the external atmosphere from entering the enclosure by maintaining a protective gas inside at a pressure higher than the surrounding atmosphere.

Powder filling protection “q”

The enclosure is filled with a finely grained powder (sand, quartz, glass balls) that fixes and surrounds all electrical parts to prevent the ignition of an external explosive atmosphere.

Reliance on IECEx for safe equipment...

To make sure that the equipment purchased meets the very strict requirements specified in the IEC 60079 series of International Standards, as well as those put in place by national or regional regulations and legislation, the Ex industry can rely on IECEx, the IEC System for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres, for testing and certification.

An IECEx certificate provides clear proof of compliance with International Standards, an important assurance for anyone responsible for the safety of those working in such areas.

...and for repair and maintenance

Because Ex equipment has a much higher capital cost than the same equipment used elsewhere, repairing it is often more cost-effective than replacing it. The IECEx Certified Service Facilities Scheme assesses and certifies that organizations and workshops that provide repair and overhaul services to the Ex industry do so according to the strict requirements of IEC 60079-19, Explosive atmospheres – Part 19: Equipment repair, overhaul and reclamation. This ensures that unique Ex safety features are not compromised during the repair or overhaul process. The system includes on-site audits prior to issuing the IECEx Certificate and periodic audit reports.

The IECEx Certified Service Facilities Scheme also covers other Ex related services including, installation and inspection of Ex equipment and installations.

High level of safety for Ex workforce

To cover all safety aspects in Ex environments and to complement the Certified Equipment Scheme, IECEx has developed the IECEx Certification of Personnel Competence Scheme for assessing and certifying individuals working in potentially hazardous areas.

The IECEx CoPC (Certificate of Personnel Competence) provides independent proof that the certificate holder has the required qualifications and experience for working on electrical equipment located in hazardous areas and can implement IEC International Standards covering explosive atmospheres.

For the CoPC, competence is defined as "the ability to apply knowledge" rather than simply assessing knowledge. In this sense, the assessment of persons includes assessing their ability to perform certain Ex-related tasks.

Gallery
Type "d" protection control panel Type "d" protection control panel (Photo: Thomas Sandbetts)
Explosion-proof CCTV camera Explosion-proof CCTV camera (Photo: R. Stahl)
Control unit for type Control unit for type "p" protection equipment (Photo: Gönnheimer Elektronic GmbH)