| 摘要 |
A sight glass for a fluid vessel that includes a housing with facility for mounting to a fluid vessel wall, and a transparent window mounted within the housing for viewing fluid within the vessel from outside of the vessel wall. A valve mounted within the housing has a normally open position for permitting passage of fluid from within the vessel to adjacent the window, and a closed position for blocking such fluid passage. The valve includes structure responsive to one or more predetermined conditions at the sight glass for moving the valve to the closed position so as to block passage of fluid to the window, and thereby provide a visual indication of occurrence of the predetermined conditions from outside of the vessel. The predetermined condition(s) sensed by the sight glass in the various embodiments of the invention include fluid leakage at the side glass, cracking or rupture of the viewing window, a high temperature or pressure condition within the vessel, and/or a high temperature condition outside of the vessel.
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