Internal fault indicator for electrical equipment

A fault indicator for indicating the occurrence of a rapid pressure surge within a housing of an electrical device, the fault indicator comprising:

• (a) a barrel capable of being mounted in an aperture in the housing;
• (b) an actuating mechanism comprising:
• (i) a chamber within the housing, the chamber having at least one orifice communicating between interior and exterior surfaces of the chamber;
• and
• (ii) an actuating member movable in response to a pressure differential between the interior and exterior surfaces of the chamber;
• (c) a plunger within a bore of the barrel, the plunger biased outwardly in the barrel and normally retained in an armed position by the actuating member;
• and
• (d) a radial seal disposed between the plunger and the barrel so as to permit relative motion of the plunger and the barrel;
• wherein, 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, and wherein the radial seal is sealingly engaged with both the plunger and the barrel in both the armed position and the triggered position.