Principle #
With this type of protection the encapsulant, typically a thermosetting epoxy resin or thermoplastic, elastomeric material, establishes a complete barrier between any surrounding flammable gas or vapour and the source of ignition within the compound.
Construction #
As the construction standards state that the encapsulant must be free of voids, this method of protection is not suitable where components have exposed moving parts. Small devices where the moving parts are enclosed (e.g. reed relay) may however e protected by encapsulation.
The encapsulant must be able to remain intact during 90%-110% variations in the range of the specified electrical input rating, adverse load conditions and any internal electrical fault.
Minimum clearance distances within the encapsulant are given in the standards, and depend on the type of construction and the free surface area.
