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Ensure safety and ATEX/DSEAR 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.

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 vapour 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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FAQ about Hazardous Area Classification (HAC)

We summarised frequently asked questions on regulations and classification of hazardous areas to give you a deeper understanding of this topic to ensure safe operations as well as regulatory compliance. If you want to learn more about our HAC services, please contact us.

What guidelines relate to HAC?

In the European or ATEX scheme, EN 60079-10-1 and EN 60079-10-2 are the relevant classification documents.

What classification scheme is used?

In the European community (IEC/ATEX), and some other countries, the Zone scheme is used. An area in which an explosive atmosphere is present continually, frequently or for long periods is designated zone 0 for gases and zone 20 for dust. An area in which an explosive atmosphere is likely to occur under normal operating conditions is labelled zone 1 for gases and zone 21 for dust. Finally, an area in which an explosive atmosphere is not likely to occur under normal operating conditions and, if it does occur, will be of short duration falls under zone 2 for gases and zone 22 for dust.

Which hazardous materials contribute to classified areas?

In the IEC/ATEX scheme, hazardous materials are grouped into categories designated I, IIA, IIB, IIB + H2 and IIC. Methane belongs to category I. Category IIA includes gasoline, acetone, ammonia, benzene, butane, cyclopropane, ethanol, hexane, methanol, natural gas, naphta, propane or similarly hazardous gases. In category IIB ethyl, ether and ethylene or gases of an equivalent hazard are grouped. A separate category, IIB + H2, comprises hydrogen, fuel and combustible process gases containing more than 30% hydrogen by volume or similar gases such as butadiene, ethylene oxide, propylene oxide and acrolein. Acetylene belongs to category IIC.

What information needs to be gathered to perform an effective HAC?

Flammability data on relevant substances must be obtained, which requires laboratory testing. For powders and dusts, this could include explosivity (dust deflagration constant (Kst)) and ignitibility (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 vapour density, auto ignition temperature (AIT), minimum igniting current (MIC) and maximum experimental safe gap (MESG). Our experts conduct these tests in our own state-of-the-art laboratories, which streamlines and expedites our services. Building and equipment layouts, evaluations of ventilation and fuel transport systems, estimations of leakage or release probability and duration are examples of other types of information required for the HAC process.

What is the end result of an HAC?

A hazardous area electrical classification report is the culmination of the HAC process and should be prepared for every facility where flammable atmospheres may be created during normal and/or abnormal operating conditions. This documentation should be revised every three years or where substantive changes are made.

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