What does ‘intrinsically safe’ mean and why does it matter in relation to explosive atmospheres? 

Explosive atmospheres can be caused by flammable gases, mists and vapours as well as dust. And many workplaces contain or have activities with the potential to generate explosive atmospheres, including vehicle spray paint chambers and mines.

For instance, you wouldn’t think it, but grain can cause lethal explosions. Dust clouds consisting of minute combustible particles surrounded by oxygen can cause an explosion if they ignite.

Safeguarding workers and facilities

To safeguard workers and property, businesses must, by law, take precautions to eliminate or controls the risks. 

In the UK this is under the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR). Precautions entail protective systems and equipment. For example, employers must provide workers in zoned areas with anti-static clothing.

In addition, electrical equipment used in and in proximity to potentially explosive atmospheres must be constructed in such a way that it doesn’t cause ignition. 

To that end, the BS EN IEC 60079 series of international standards covers a wide range of considerations when it comes to potentially explosive atmospheres: from general equipment requirements and gas detectors to different ways of protecting equipment and how to classify areas and materials.

Among the ways to protect is to deploy “intrinsically safe” electrical equipment. “Intrinsically safe” means electrical equipment in which the electrical circuits themselves are incapable of causing the ignition of a surrounding explosive atmosphere. How to construct and test such electrical equipment is covered in the newly revised BS EN IEC 60079-11:2024 Explosive atmospheres - Equipment protection by intrinsic safety "i".

What does BS EN IEC 60079-11 cover?

The standard covers how to construct and test intrinsically safe apparatus and associated apparatus intended for connection to intrinsically safe circuits that enter explosive atmospheres. It includes electrical equipment which contains circuits that are intrinsically safe only under certain conditions, for example under battery supply with mains supply removed.

What revisions have been made in BS EN IEC 60079-11?

The 2024 revisions to BS EN IEC 60079-11:2024 are extensive. They attempt to resolve differences in how the standard is applied and to clarify it in comparison with the preceding sixth edition published in 2012. There are a significant number of editorial changes, including a restructuring of sections.

Revisions include many clarifications so the standard requires less interpretation and is easier to use. Additions include a new requirement for routine verification of encapsulation; a new requirement for transformers for Level of Protection ‘ic’; new requirements and tests for thermal devices; and a new requirement to consider the spark ignition risk of single lithium cells of less than 4,5 V with high short circuit current.

Changes include that countable fault separation between the coil and contacts of a relay is no longer permitted and it’s now a requirement that circuits remain intrinsically safe after the disconnection of a connector.

What are the benefits of BS EN IEC 60079-11:2024?

BS EN IEC 60079-11:2024 is a standard that will develop users’ expertise and can increase the confidence of workers in explosive atmospheres. It’s also due to be listed in the ATEX OJ and UKCA designated standards list so can be used to show that products comply with essential requirements in legislation. 

Meanwhile all the revisions are about making the standard clearer and safer in pursuit of safer explosive atmospheres.

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