Abstract: A fault indicator for indicating the occurrence of a rapid pressure surge within a housing of an electrical device has: a barrel capable of being mounted in an aperture of the housing; an actuating mechanism having a chamber with at least one orifice communicating between interior and exterior surfaces of the chamber within the housing and an actuating member movable in response to a pressure differential between the interior and exterior surfaces of the chamber; a plunger within the bore of the barrel biased outwardly in the barrel and normally retained in an armed position by the actuating member; and a radial seal disposed between the plunger and the barrel. When the pressure differential exceeds a positive threshold value, the actuating member is moved and thereby permits the plunger to move outwardly into a triggered position. The radial seal may be a dual-lip seal.

Abstract: A fault indicator for indicating the occurrence of a rapid pressure surge within a housing of an electrical device has: a barrel capable of being mounted in an aperture of the housing; an actuating mechanism having a chamber with at least one orifice communicating between interior and exterior surfaces of the chamber within the housing and an actuating member movable in response to a pressure differential between the interior and exterior surfaces of the chamber; a plunger within the bore of the barrel biased outwardly in the barrel and normally retained in an armed position by the actuating member; and a radial seal disposed between the plunger and the barrel. When the pressure differential exceeds a positive threshold value, the actuating member is moved and thereby permits the plunger to move outwardly into a triggered position. The radial seal may be a dual-lip seal.