In the automation industry, hazardous areas are defined as locations where explosive or flammable substances may exist in sufficient quantities to create a risk of fire or explosion. These hazardous areas are classified based on the type and quantity of explosive or flammable substances that may be present.
The classification of hazardous areas is done according to international standards, such as the International Electrotechnical Commission (IEC) and the National Electrical Code (NEC) in the United States. The classification process involves determining the likelihood of a hazardous event occurring, the severity of the event, and the probability of ignition sources being present.
There are three main factors that are considered when classifying hazardous areas in the automation industry:
- The type and properties of the hazardous substance(s) that may be present, including the ignition temperature, flashpoint, and explosive limits.
- The likelihood of the hazardous substance(s) being present in the atmosphere, which depends on factors such as the process being carried out, the type of equipment being used, and the frequency of maintenance activities.
- The possible sources of ignition, such as electrical equipment, static electricity, and hot surfaces.
Based on these factors, hazardous areas are classified into different zones or divisions. The specific classification system used depends on the country and region where the facility is located. The following are the commonly used hazardous area classification systems:
- IEC Classification: In the IEC classification system, hazardous areas are classified into zones based on the likelihood and duration of the presence of explosive atmospheres. There are four zones in the IEC classification system:
- Zone 0: An area in which an explosive atmosphere is present continuously or for long periods.
- Zone 1: An area in which an explosive atmosphere is likely to occur in normal operation.
- Zone 2: An area in which an explosive atmosphere is not likely to occur in normal operation, but if it does, it will exist only for a short time.
- Zone 20: An area in which an explosive dust atmosphere is present continuously or for long periods.
- Zone 21: An area in which an explosive dust atmosphere is likely to occur in normal operation.
- Zone 22: An area in which an explosive dust atmosphere is not likely to occur in normal operation, but if it does, it will exist only for a short time.
- NEC Classification: The NEC classification system is used in the United States and classifies hazardous areas into divisions based on the properties of the hazardous substance(s) and the likelihood of the substance(s) being present in the atmosphere. There are two divisions in the NEC classification system:
- Division 1: An area where an explosive atmosphere is present or likely to be present in normal operation.
- Division 2: An area where an explosive atmosphere is not likely to be present in normal operation, but if it does, it will exist only for a short time.
- ATEX Classification: The ATEX classification system is used in the European Union and classifies hazardous areas into zones based on the likelihood and duration of the presence of explosive atmospheres. It is similar to the IEC classification system.
In conclusion, the classification of hazardous areas in the automation industry is crucial for ensuring the safety of personnel and equipment. The specific classification system used depends on the location of the facility and the properties of the hazardous substance(s) present. It is important to comply with the relevant standards and regulations when working with hazardous materials to prevent accidents and ensure the smooth operation of automation systems.
