This type of protection is suitable for Zone 2 or 22 hazardous areas, and can apply to a large range of equipment.
Generally any electrical device that does not have potentially sparking contacts can be accommodated.
To prevent sparking on PCB’s and other critical electric components, creepage and clearance distances need to be addressed carefully. ATEX coating can be used to reduce risk of arcs and sparks between conductors. In most cases the enclosures need to be dust/water tight to avoid tracking across live circuits.
In addition, specific requirements apply to certain recognised types of equipment, such as motors, luminaires and batteries.
Equipment with potentially sparking contacts such as PCB’s, potentiometers, relays or switches, can be protected in a number of ways:
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Encapsulation
Suited to higher power circuits or where creepage and clearance distances on a circuit board are below the required minimum.
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Sealed
The sparking device is sealed in an enclosure so that the flammable atmosphere cannot gain access.
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Restricted breathing
The enclosure may contain either hot components but no sparking components, or sparking components but with low internal air temperature rise. This method relies on a tight gasket seal on the enclosure joints.
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Enclosed break
Applies to small enclosures where the design of the enclosure joints prevents an internal ignition from transmitting to the flammable atmosphere outside. Similar to Ex d but without flame path design requirements.
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Energy limited (see intrinsic Safety (Ex i) – EN 60079-11)
Similar to intrinsic safety, the energy available in potentially sparking parts is limited to prevent an ignition occurring. Suitable for circuit designs where detailed knowledge of the design is available and modifications can be accommodated.
