Electrical equipment for hazardous areas - environmental considerations

In production and work places, potentially explosive atmospheres can develop wherever flammable gases, vapours or dusts are mixed with the oxygen contained in the air.

The following conditions need to be present for an explosion to occur:

• Oxygen in the air
• A flammable substance
• An ignition source

The first two factors - the flammable substance and air - must be present in sufficient quantities to form an explosive atmosphere. Typical hazardous areas form in chemical factories, refineries, enamelling plants, paint workshops, cleaning equipment, mills and stores for milled products and other combustible dusts, in tank facilities and loading areas for flammable gases, liquids and solids.

For effective explosion protection, one of the three conditions needs to be excluded. Oxygen and hazardous substances cannot be excluded in a workplace and, hence, explosion protection principles are generally focussed on excluding systems, devices and components as ignition sources.

Prior to selecting equipment in an installation, a full understanding of the plant conditions is required.

In terms of the hazardous environment the following must be understood:

• What hazardous materials are present and their specific characteristics;
• How an explosion may occur;
• The probability of an explosion occurring/degree of risk
• Environmental factors

The last item, environmental factors, is unfortunately often overlooked. It is often the case that systems are designed to meet performance goals where strength, weight, thermal and electrical requirements and explosion protection techniques are primary technology considerations while other important attributes such as corrosion resistance and environmental compatibility receive far less attention.

To be totally effective, specifiers and contractors must consider the inherent corrosion resistance of the selected structural materials of the product for the environment they will operate in and any potential interaction these materials may have with adjacent materials as well as the corrosion prevention technologies such as coatings and other compounds needed to minimize maintenance requirements. If little thought is given up-front to select the best combination of structural materials and corrosion prevention technologies, then a maintenance nightmare may be in the making! In addition, the incorrect selection of product can compromise the explosion protection technique resulting in a potentially explosive environment.

Sylvania Lighting Australasia (SLA) is accredited to manufacture CSE Ex hazardous and arduous environment products and SLA and CSE are both Australian manufacturers.