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.
Conducting a hazardous area classification can be challenging, as it requires a thorough understanding of the processes used and the equipment associated with them.
- Compliance to the safety regulations
- Assessment of fuel transmission
- Determination of the areas in which combustible atmospheres are present
- Complete documentation
The first step of our hazardous area classification 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.
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.