Optimizing the Design of a NEMA Type 7 ``Explosion-Proof´´ Enclosure Used for Electromechanical Switching Devices

In the past, National Electrical Manufacturers Association (NEMA) Type 7 ``explosion-proof´´ enclosures have often taken the ``brute strength´´ approach, resulting in heavy, bulky, and hard-to-work-on devices from the user´s viewpoint. However, it is possible to design a more optimized NEMA Type 7 enclosure. Presented is a systematic approach to the design of an optimized NEMA Type 7 ``explosion-proof´´ enclosure to provide end users with a better understanding of how these enclosures are designed and how they function. The chemistry of vapor explosions, enclosure geometry considerations, and the functional requirements that these enclosures must meet are examined. Several methods of stress measurement are discussed. An overview of methods and equipment necessary for hydrostatic and explosion testing is presented.