Are you working in an explosive environment? Are the areas in your workplace properly classified according to the necessary documentation? Is the equipment installed and properly rated for safe operation in those explosive atmospheres?
In the first article of the series, we introduce you to explosive environments in the workplace. We give an overview on how to classify explosive areas according to the necessary standards, and explain the compliance standards your company should adhere to, for specific areas, at all times. Furthermore, we identify what to look for when installing and operating electrical equipment in an explosive area.
Explanation of Zones
Precautions must be implemented to prevent fire and explosions in areas that consist of an explosive atmosphere. For example, lighting will have to be designed accordingly to ensure sparks are prevented as it may lead to the ignition of a flammable substance.
Hazardous areas are classified into zones for the ease of monitoring and specification. These zones will govern the level of protection and precaution required for it. The zone classifications of gases, vapours and mist are recognised as Zone 0, Zone 1, and Zone 2.
IEC/SANS 60079-10-1 for gas zones should be used when assessing the extent of the hazard.
Zone 0
An area where an explosive atmosphere is present continuously for long periods of time and will frequently occur.
Zone 1
This is an area where an explosive atmosphere may likely occur during normal operation. The explosive atmosphere may be a result of repair, maintenance operations or leakage.
Zone 2
This is an area where an explosive atmosphere will not occur in normal operation but if it does occur it will persist for a short period of time. These areas become hazardous if there is an accident or an unusual operating condition.
Standards and Codes to Comply With
Hazardous locations in the workplace must comply with the Occupational Health and Safety (OHS) Act, to ensure safety of personnel and equipment.
Standards that are used for the classification of hazardous locations can be found in SANS 10108:2017 (Ed. 6.01). SANS 10108 states that preference must be given to IEC standards and these standards should be implemented for the specific plant that is being classified. Hence, SANS 60079-10-1 (flammable gasses and vapours) and SANS 60079-10-2 (combustible dusts and fibres) are the primary standards.
Safety of Equipment
In areas where the risk of explosion is caused by the presence of explosive gas such as zone 0, these types of zones shall require equipment that has a very high level of protection. Locations that have a low risk, such as zone 2, will require lower levels of protection. It is vital that a risk analysis be done according to the standards set out by SANS 60079-10-1 and SANS 60079-10-2.
The table below shows the minimum protection level for equipment and explanation for each level.
Electrical Equipment
Electrical equipment that is installed in a gaseous atmosphere is divided into two groups. Group I makes reference to equipment that is used in mines of which has gases such as methane or similar vapours in the atmosphere whilst group II refers to equipment that is used above ground. The group is further divided into three subgroups where group IIA consists of atmospheres that have propane, or gases and vapours of equivalent hazard. Group IIB is used for atmospheres that contain ethylene, or gases and vapours of equivalent hazard whilst group IIC includes atmospheres containing hydrogen or gases and vapours of equivalent hazard.
The table below refers to the identifiers found on the nameplate of electrical equipment. These identifiers show which atmosphere the equipment can operate in.
In the next article of the series, we cover temperature classification, IP ratings and nameplates We end off with a summary of some explosions that took place at South African facilities.
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