Hazardous Area Classification

Ensure safety and compliance with hazardous area classification

By identifying the areas susceptible to fire or explosion, hazardous area classification (HAC) assists industries in reducing their chances of experiencing an incident resulting in damage to property and potential injury or loss of life. Originally HAC was used to enable process companies to make the correct choice of electrical equipment to prevent electrical ignition of flammable atmospheres.

Now HAC is being applied in wider risk assessment work and to counter a range of ignition sources, such as electrostatic sparks, and flammable substances, such as solvent vapors, gases or mists and dust clouds. For this reason, HAC is needed not only in chemical plants but in a variety of other industries from food processors to power generation. Both OSHA and the NFPA reference HAC in their safety regulations, as do the ATEX/DSEAR directives in Europe.

Conducting a hazardous area classification can be challenging, as it requires a thorough understanding of the processes used and the equipment associated with them.

We are experts in both the terms of reference for HAC and your obligations and responsibilities under new and existing regulations, identifying those areas in a plant where flammable atmospheres can be found and their frequency. With an international orientation and disciplined approach, we are uniquely suited to provide HAC support and our experts have the know-how and experience to guide you through the complexities of the classification process.

Hazardous area classification – DEKRA
In nine steps to your hazardous area classification

An uncompromising approach to hazardous area classification

Implementing a hazardous area classification exercise requires a thorough knowledge of the relevant industrial processes and equipment. The first step, therefore is to assemble a team with a fundamental understanding of the facility’s operational areas, electrical equipment, processes, and maintenance requirements.

The next step is to compile the appropriate flammability data for the materials of interest. For powders and dusts, this might include explosibility (dust deflagration constant (Kst)) and ignitability (minimum ignition energy of

a dust cloud (MIE), minimum ignition temperature of both a dust cloud and layer (MITc and MITl), minimum explosible concentration (MEC)) tests, and conductivity properties. Where gases or liquids are concerned, important tests include limits of flammability , flashpoints (liquids), gas or vapor density, auto ignition temperature (AIT), minimum igniting current (MIC) and maximum experimental safe gap (MESG).

The team then identifies potential sources of liquid, vapor, gas and dust releases in both normal and abnormal conditions, estimates the duration of leaks or releases and determines if there is an ignitable mixture likely to occur during any release or leakage as a result of repairs or maintenance. An assessment of fuel transmission via trenches, pipes, conduits or ducts is also made, as well as an evaluation of the efficacy of ventilation.

Documentation is an essential component of HAC. In addition to compiling building and equipment layout drawings, the team applies the proper guidelines to assign a class, division or zone rating to the areas under investigation, including the size of the area covered. This classification is then documented, including ratings of equipment used in the hazardous areas.

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