Standards aim to stop sparks flying and dust exploding

Many companies in the food sector are at risk of catastrophic explosions because of three things: air, combustible dust and a source of ignition such as an electrical spark or hot surface, warns an expert in the field.

A staggering 2,000 dust explosions occur in Europe every year, warns Graham Doran, sales and marketing director at Cooper Crouse-Hinds (UK). And flour, custard powder, sugar, coffee and tea, all provide potential sources of combustible dust, he adds.

Problems can arise when these combustible dusts gather on hot surfaces in a workplace, such as on an overheated electric motor or fan, he says. This can cause smouldering fires, or an explosion when the dust is kicked up, for example, by a person opening a window.

Dust explosions can have catastrophic consequences because the initial shockwave kicks up more dust, which triggers a chain reaction, he adds, often resulting in mass destruction of equipment and buildings, and causing possible death or injury to employees.

Therefore, as potential sources of ignition, all electrical equipment installed in these areas - including mixers, filling hoppers, conveyor systems, mills, silos, dust extraction plant, kilns and drying systems - needs to be adequately protected and designed to operate under these conditions, says Doran.

Owners of new equipment are governed by the compulsory European directive 1999/92/EC, implemented in the UK as the 'Dangerous Substances and Explosive Atmospheres Regulations 2002' (DSEAR). From 2006 this directive includes old and new equipment.

For electrical equipment in areas at risk, a new series of standards, (EN 61241) was introduced. This stricter one came into effect from October 2008 and supersedes the existing EN 50281. One of the main protection types for production equipment at risk under this standard is where the electrical production equipment has an enclosure to prevent dust penetration and where measures have been taken to limit the surface temperature.