Dusty business

IECEx-certified equipment key in mitigating explosion risks

By Claire Marchand

Some industry sectors are automatically associated with explosive (Ex) atmospheres – oil and gas, petrochemical plants, mining and in particular coal mining. Many others won’t necessarily come to mind although the risk of fire and explosion exists and needs to be heeded. Food processing, sugar refineries, grain handling and storage, printing, paper and textile industries, sawmills, woodworking areas or waste treatment operations are all potential hazardous areas. Not to mention gas stations or aircraft refuelling and hangars.

coal mine Dust explosions are a frequent occurrence in underground coal mines

Focus on dust

What is the common denominator between all these sectors? They all utilize flammable or combustible substances in quantities capable of resulting in concentrations that are potentially explosive, whether on a constant basis, as a by-product of normal operation or due to the occurrence of an abnormal situation. 

One of the substances found in huge quantities in many Ex industry sectors is dust. 

Dust is often the by-product of a production process and treated as waste, but it can also be an important element in the manufacturing of products such as food products, pharmaceuticals or pigments. Coal, wood, grain, sugar starch, certain metals, dyes and plastics all generate dust. 

Potential risks

The large majority of industrial dusts are combustible, and dust explosions can occur in any enclosed area. Dust explosions are a frequent occurrence in underground coal mines, but they can nevertheless happen in any location where powdered combustible material is present. 

A publication by German-based company Stahl explains the mechanisms of a dust explosion: “If a draft of air swirls up a layer of dust in a small area, the dust, along with oxygen, forms a combustible dust/air mix. If this mix is ignited by an ignition source, an explosion is triggered. The force of the resulting explosion swirls up more dust, which is in turn ignited. This process continues, and under some conditions, chain reactions such as these sweep through entire buildings or facilities, destroying them.” 

Even an extremely thin dust layer in a closed room is sufficient to trigger an explosion when the dust is swirled up and ignited. 

Ignition sources for dusts include sparks from electrical or mechanical processes, arcs, open flames, electrostatic discharge (ESD), and electromagnetic waves among others. 

Safe manufacturing processes

Because of the hazards associated with the presence of dusts, all electrical and non-electrical equipment – electric, hydraulic and pneumatic motors, cables, enclosures, isolators and vents, lamps and switches, control systems, pumps, gearboxes, brakes, and many, many more – used in manufacturing processes should have the relevant level of dust explosion protection. Failure to do so can result in major industrial accidents and have fatal consequences. 

Through its standardization and conformity assessment work, the IEC has a solution for all sectors of industry that are operating in those hazardous environments. The Commission has been at the forefront of Ex standardization for many years, preparing International Standards and establishing a Conformity Assessment (CA) System that provides testing and certification for all types of Ex equipment and related services as well as personnel competence. 

Specific requirements for Ex equipment

IEC Technical Committee (TC) 31: Equipment for explosive atmospheres, has a complete series of International Standards, IEC 60079, that cover all specific requirements for electrical Ex equipment and systems, from general requirements to protection levels for apparatus used by all sectors that operate in hazardous environments, such as pharmaceuticals, food processing, sugar refineries, flour mills, grain silos as well as the paper and textile sectors. 

Several International Standards focus on dust:

  • IEC 60079-10-2:2015, Explosive atmospheres – Part 10-2: Classification of areas – Explosive dust atmospheres
  • IEC 60079-31:2013, Explosive atmospheres - Part 31: Equipment dust ignition protection by enclosure "t"
  • ISO/IEC 80079-20-2:2016, Explosive atmospheres - Part 20-2: Material characteristics - Combustible dusts test methods 

One of IEC TC 31 Subcommittees, SC 31M, recently published two International Standards – ISO 80079-36:2016, Explosive atmospheres - Part 36: Non-electrical equipment for explosive atmospheres - Basic method and requirements, and ISO 80079-37:2016, Explosive atmospheres - Part 37: Non-electrical equipment for explosive atmospheres - Non electrical type of protection constructional safety "c", control of ignition source "b", liquid immersion "k", dealing with non-electrical equipment and protective systems for explosive atmospheres. 

Testing and certifying to IEC Standard

Manufacturing Ex equipment in compliance with IEC International Standards is one thing. To make sure that the equipment they purchase 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. 

It is worth noting that in 2016, IECEx issued the first three certificates for non-electrical equipment that met the requirements stipulated in ISO 80079-36 and ISO 80079-37. 

Repair and maintenance of Ex equipment

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 the 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 Certificate of Personnel Competence (CoPC) 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. 

More information on IECEx: www.iecex.com

Gallery
coal mine Dust explosions are a frequent occurrence in underground coal mines...
sawdust ...they can also happen in locations where powdered combustible material is present, such as sawmills...
...or food processing plants