Case Studies

Case #01: Enclosure with Purging Protection

A general purpose lighting source is required to be used in an aircraft hangar where it is defined as "Class I Division 2" according to NEC Article 513. However, S-Airline concerned much more safety and treated the workshop as "Class I Division1". ATE engineer adopted a X-Purge Unit and customized an air-tight stainless steel enclosure (500mmx500mmx250mm) to house all "general purpose" electrical devices such as lighting source, MCB, transformer and magnetic contactor. Relief valve and spark arrestor with orifice were included as well. Such design meets the standard of National Fire Protection Association NFPA496. Its major function is that electric supply will be automatically powered on after the enclosure is purged for a presetting Purge Time (e.g. 10 minutes) and keep maintaining pressurized at 1 to 4 inch water high. When pressurization fails, power supply will be cut off immediately.

What is Z-Purge?
Z-Purge Unit makes unclassified equipment be used safely in Zone 2 (or Division 2). In this case, equipment inside the enclosure can be any "general purpose" one. In another word, Z-Purge Unit can reduce an enclosed space from Division 2 (or Zone 2) to unclassified.

What is Y-Purge?
Y-Purge Unit makes Zone 2 (or Division 2) equipment be used safely in Zone 1 (or Division 1). In this case, equipment inside the enclosure must be approved or certified for safe use in location of Zone 2 (or Division 2 ) hazardous area. In another word, Y-Purge Unit can reduce an enclosed space from Zone 1 (or Division 1) to Zone 2 (or Division 2).

What is X-Purge?
X-Purge Unit makes unclassified equipment be used safely in Zone 1 (or Division 1). However, an enclosure with X-Purge Unit may have equipment or devices which can cause ignition of flammable atmosphere so that the X-Purge Unit is required to control electric power to enclosure automatically and to provide remote alarm annunciation upon loss of positive purging pressure.