Knowledge Pressure equalization with breathing membrane vents


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A membrane vent is used to equalize pressure within an enclosure and reduce condensation while filtering out liquids and other contaminants. The outdoor environment and a variety of indoor spaces call for the use of sealed luminaires of high ingress protection (IP) ratings, e.g. IP6X. But over time, seal performance will decline and the level of ingress protection degrades accordingly when pressure differentials within the enclosure repeatedly stress the seal. Pressure differentials are created when there are extreme changes in temperature. For LED luminaires, the temperature change can be internal, external or both. High density light engines generate a significant amount of heat and result in high internal temperatures. Externally, pressure differentials can be created due to the dramatic changes in outdoor temperature. A strong thunderstorm on a hot summer day or diurnal temperature variation (variation between a high temperature and a low temperature that occurs during the same day), for example, can create a vacuum inside the sealed enclosure.

If pressure differentials are not dissipated, either the positive or negative buildup will put significant stress on the seals. No matter how rugged the seal, repeated stress caused by pressure differentials over time cause seals to fail, which in turn compromises the enclosure integrity. In addition to failed seals that cause the degree of protection against external dust and water to be degraded, moisture can get inside enclosures by diffusion. Moisture ingress leads to condensation on lenses if water vapor that enters a sealed enclosure has no way to escape. Condensation inside the luminaire can cause lumen depreciation, color shift, and corrode sensitive electronics.

To maintain seal performance and reduce condensation it is crucial to equalize pressures within the enclosure. Pressure equalization membranes made from expanded polytetrafluoroethylene (ePTFE) provide an effective membrane solution for venting applications due to the unique microstructure as well as high chemical and temperature resistance of ePTFE. ePTFE's microstructure allows gas molecules and vapor to pass through the membrane easily. The ability to enable the flow of air and moisture vapor into and out of sealed enclosures allows effective equalization of pressure differentials and prevention against moisture condensation. Meanwhile, ePTFE's microstructure provide a durable barrier against the ingress of liquid, dust, dirt and other contaminants.