| 摘要 |
A portable electric lamp suitable for use in hazardous locations includes a fixture which is purged continuously with air during operation. Pressurized air is introduced at an input end of the fixture, through a plenum which establishes a generally laminar flow of air through the fixture during purging. To insure that the fixture is satisfactorily purged before power is applied to the lamps, differential pressure is measured over a precision orifice at the discharge end of the lamp, and total flow is determined. During the start-up cycle, pressure within the fixture must exceed a predetermined minimum threshold; but following start-up, the operating pressure may drop lower than the initial minimum pressure, as long as a positive pressure is maintained within the fixture.
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