Encapsulated designs rely on enclosing the electrical circuitry with a permanent covering of insulation. The insulation separates the electrical components from the explosive atmosphere, preventing arcs, sparks and hot components from causing an ignition.
Recent changes to the equipment standards have made encapsulation type 'ma' the only other type of equipment allowed inside of Zone 0 hazardous locations. Previously, only intrinsically safe equipment was allowed inside Zone 0 areas. At time of writing, however, there were technical barriers to actually adopting type 'ma' equipment, meaning more work is necessary.
Encapsulated designs can be inexpensive and relatively easy to design. However, since the encapsulant is permanently bonded, the equipment is often not serviceable. Also, components that are moveable or visible, such as switches and displays, can not usually be encapsulated.
The encapsulant must also pass a significant battery of tests, including thermal endurance and its ability to quench a flame. This testing can take a significant amount of time at the certification agency.
Encapsulation is often useful for design modues, such as battery packs, thare are difficult or impossible to design using other techniques. In these cases, only the inputs and outputs of the module need to electrically protected, as with intrinsic safety, to prevent incendive energy from escaping the potted area.
Go to Protection Techniques.
Go to Certification Standards.
Go to Understanding ATEX.
Go to Understanding IEC 60079.