Drives & Controls November/December 2023

38 n SAFETY November/December 2023 Atex compliance keeps combustible dust explosions at bay The dangers posed by combustible dust are so potentially serious that implementing the minimum safety measures of a mitigation plan and risk assessment are either legally required or highly recommended at most production facilities around the world – even those where the likelihood of an explosion is incredibly small. This makes being familiar the the standards and codes vital. In the EU, two main directives are legally required, with Atex 153 outlining minimum requirements for the health and safety of employees, and Atex 114 ensuring that equipment suppliers offer the most effective technologies to make potentially explosive atmospheres safer. Previously known as Atex 137 – or the “social” or “workplace” directive – Atex 153 1999/92/EC obliges employers to evaluate the potential risk at their premises, whether or not explosive dust is likely. Assuming they have sufficient knowledge, this risk assessment can be performed by the employer’s own Health & Safety personnel, using the checklist in Article 8 of the Directive. Integrating risk-mitigation planning may reduce costs while keeping explosion riskassessment on track. And, while the most advanced mitigation technologies may have higher initial price tags, compared with the total cost of a combustion event – including the potential loss of life resulting from secondary explosions – premium options that cut downtime, clean-up and damage will invariably seem much less costly in the long-term. From a legislative point of view, it is vital to maintain all explosion-prevention documentation, highlighting the steps and mitigations that were (or were not) taken, should an incident occur. Zones An assessment involves classifying the factory into zones, differentiating between gas or dust explosion risks and their potential likelihood. Harmonised standards from the EN60079 series outline this classification, ranging from No Risk where there is no potential gas or dust atmosphere in the factory, through to Zone 22 (or Zone 2 for gas) where the risk may be present for up to 10 hours per year, Zone 21 (Zone 1 for gas) where there is danger for up to 1,000 hours per year, and finally to Zone 20 (Zone 0 for gas) where there is frequent or continuous risk (see table). Bear in mind that any major changes or new processes – perhaps as a result of increased production rates or advances in technology – will require a new explosion protection document, so identifying any future plans for remodelling or expansion will be well worthwhile. Should process changes lead to the need for different Atex certification, equipment can be modified but will need to be recertified by a notified body or expert to ensure CE conformity. A prime example of Zone 20 is the constant dust cloud found inside a dust Melina Diaz, product engineering manager at the explosion-mitigation specialist Donaldson, outlines the steps required to comply with legislation designed to ensure that workplaces minimise the possibility of combustible dust creating an explosion risk. A dust collector handles a combustible dust explosion during a field test.