Schauglas

Schauglas is a German term meaning "viewing glass" used in engineering to describe a transparent window integrated into a vessel, pipe, or valve to permit visual inspection of its contents. These sight glasses are used to observe liquid levels, color changes, contamination, and gas presence without opening the system. They are common in boilers, chemical reactors, digesters, and oil and gas processing equipment. A typical Schauglas consists of a glass pane sealed into a metal housing with appropriate gaskets and a protective guard; high-pressure or high-temperature versions may use quartz glass and multiple seals to prevent breakage and leaks. In some configurations, the glass is set at a vertical orientation to allow drainage of condensate away from the viewing surface.

Designs vary in material and mounting: borosilicate glass for moderate conditions; quartz for higher temperatures; some include light sources and external viewing windows for backlighting. Safety considerations include glass breakage risk, proper support, and rated pressure-temperature limits; installation must satisfy relevant standards in the chemical, petrochemical, and power industries. The term is used primarily in German-speaking contexts, but in English-language technical literature it is often translated as sight glass or viewing window.

Schauglas may also be encountered as a proper noun in other contexts, including surnames or place names in German-speaking regions, though these uses are less common than the generic term for equipment windows.