The Complexities of Dust DSEAR Assessments

Area classification and DSEAR risk assessments?for combustible dust environments varies drastically from that of gases/ vapour environments.?Most of this awareness comes with carrying out many of these assessments in different industries.??Some of the key differences we have noticed when carrying out these assessments which makes them particularly complex and challenging:

There are (pretty much) no calculations you can do for dust cloud zoning assessments.

Most zone extents come from guidance in the standards (BSEN60079-10-2) or from site observations.?This means using an experienced assessor is critical, as they will be able to compare to other situations and understand the potential failure?modes more readily.

A basis of safety of "explosion venting"

Because of the difficulty in excluding all ignition sources when dealing with dust handling systems, right down the bottom of the hierarchy of control there is the option to vent an explosion safely, away from people.?This options isn't generally acceptable on gas/ vapour systems and provides a final route to a basis of safety if none of the other options are viable (and deals with the tricky issue of foreign bodies in dust handling systems that no amount of magnets can get rid of).

An improvement in housekeeping can have a major impact

We risk assessed one facility who had got their dust layers checked for flammability.?With the dust covering large areas of multiple levels of a large facility, it would have almost bankrupt the company to upgrade all their equipment to being suitable for dust zones.?Instead, a pragmatic solution was to implement more thorough and audited housekeeping regimes, to keep on top of dust levels and therefore declassify the whole of the area, except where small secondary zones existed.?This can be a very good reason to do your DSEAR RA first, before attempting to do area classification zoning, as you would otherwise have to revisit the zoning once improvements identified in the risk assessment are implemented.

The secondary explosion risks can be huge

When a large area is covered in even a small surface layer of combustible dust, the potential impact of this dust and the resultant explosion can be catastrophic if dislodged in the presence of a source of ignition.?There are no shortage of industry examples of secondary explosion events.?From a P&ID and desktop risk assessment often you simply cannot grasp the potential magnitude, which means that for dust facilities a site visit is always a must for DSEAR Risk Assessments (no matter what the Covid travel restrictions might be!).?The closest analogy for gas/ vapour systems would be pool fire events, leading to fire relief of other equipment and potential overpressure events, but again these are fairly predictable for gases and vapour risks compared to dusts.

We are fortunate to have had experience carrying out DSEAR risk assessments in a variety of industries handling dusts such as food, distilleries, waste management, general manufacturing, pharmaceuticals and speciality chemical sectors.?This means we?can provide a very broad range of potential solutions and improvements to most DSEAR studies we undertake to help clients protect their people and assets.

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