REFLEX LEVEL GUAGE

 LIQUID ZONE 

This zone appears quite dark when the gauge is in operation and lighted as above said. Given the construction, most of the environmental light rays incident on the external face of the glass are quite perpendicular to said face and, therefore, not deviated by the glass. These rays reach the glass/liquid interface with an inclination of approx. 45°. The critical angle glass/liquid is always superior to 45°. Therefore the rays incident within the critical angle (practically the totality) are refracted within the liquid and, since the internal walls of the gauge chamber are not reflecting, the rays cannot be seen from the outside. In fact the zone will appear dark, nearly black, to the observer.

 LIQUID ZONE 

This zone appears almost silver bright to the observer. As for the liquid zone, the light rays reach the glass/gas-vapor interface with an angle around 45°. Since this angle is greater than glass/gas-vapor critical angle, the rays are not refracted , but totally reflected making 90° turn, thus reaching the nearest glass/gas-vapor interface again with angle of 45°. For same reason they will be reflected and turned by 90° towards the observer, to whom the zone will appear silver bright.

 APPLICATIONS 

Reflex glass level gauges can be used in most of the cases and offer great advantages in terms of: low initial cost, low operating cost, easy level reading.
Reflex level gauges cannot be used in certain cases as for example:

• When the separation level between two liquids has to be read (interface)
• When besides the level indication, the observation of the liquid colour is required
• When the process fluid is high-pressure water steam, since in this case the glass must be protected from the solvent action of the boiler water by using mica shields
• When the process fluid is such that can corrode the glass (e.g. high temperature
  alkal ine solut ions or hydrof luor ic acid) , since ica shields or
  Polytrifluorochloroethylene shields must be used to protect the glass