Sight glass
A sight glass or sight-flow indicator provides a window into a process line so an operator can observe the presence and approximate condition of flow, fluid colour, or nearby equipment performance. It is not necessarily a shutoff valve, despite its taxonomy placement, and visual observation is not a substitute for accurate flow measurement or definitive fault diagnosis. Selection should address compatibility of the glass and seals with the medium, pressure and temperature, viewing clarity, orientation, guarding, and cleaning requirements.
Application and duty
Direct observation of approximate flow condition or fluid colour in a pipeline; visual limits and transparent-component compatibility must be reviewed for the service.