Abstract: An enclosure for a pressure relief device, particularly pressure relief devices mounted on electrical equipment housings, is pre-assembled together with the pressure relief device. The enclosure, which provides for temporarily confining and directing fluids discharged from the pressure relief device, is pre-assembled leaving a clearance space so that the pressure relief device can be mounted on the housing with the enclosure system in place. A peripheral shield with an opening for attaching the enclosure to a discharge pipe or other duct work remains rotatable until deliberately secured in place. Components can be shared between the enclosure and the pressure relief device to provide a more efficient and cost effective design.

Abstract: A pressure relief device for electrical equipment housing, includes a valve body having a pedestal that projects above a mounting flange and a table on the pedestal that supports a two-stage valve assembly that can be sized in diameter independently of the working area of the flange beneath the table. The design is particularly applicable to retrofit applications for large power distribution equipment with the footprint of the pressure relief device fixed by the design of the equipment housings. The first-stage valve opening can be sized substantially as large as vent openings in the housings and the second-stage valve openings can be sized in the desired relationship with the first-stage opening for optimizing valve performance independently of the constraints imposed by the footprint of the device.