The purpose of hazardous area classification is to ensure that ignition sources are generally not available to ignite potential flammable atmospheres.
Refer below image for Hazardous Area Classification Drawing
Hazardous areas extent, definition and identification, which is based on the Area Classification Code for Installations Handling Flammable Fluids, Institute of Petroleum Model Code of Safe Practice, Part 15 3rd Edition.
The overall design philosophy shall be to make the site as safe as possible by minimizing potential sources of release of flammable gas and ensuring efficient ventilation to disperse any gas release.
A Hazardous area classification document containing Hazardous area schedule shall be prepared. Also Hazardous area classification drawings showing plan view and elevations shall be prepared. A hazardous area schedule and related drawings shall be produced identifying potential sources of emission, the process material, its operating conditions, flash point, fluid category, hazardous area boundary dimensions from source and source of release grading.
Release Frequency Level II will be applicable as a minimum (average occupancy of operations and maintenance is assumed. this a conservative approach).
Gas group IIB and temperature class T3 will be applicable as a minimum requirement for electrical equipment and instrumentation (IIB for H2S, T3 for crude, conservative approach). (reference: BS EN 60079-20-1:2010).