Prismatic (Reflex) Water Gage Glasses


Reliance Prismatic (reflex) Gages provide a well defined, distinct image of water level, eliminating reading errors or distortions possible with less effective gage types. Highly versatile, Prismatic Gages are easily installed in vertical or Tiltview™ Assemblies. In addition, Reliance Prismatic Gages offer the flexibility of combining multiple gage sections to achieve coverage of extended viewing areas.

Available in two designs, “C” Types are specified for boiler design pressures to 250 PSI and “S” Types for pressures to 350. Typical Prismatic Gage applications include installation on boiler drums, feedwater heaters, deaerators, and other tanks.

Quality Materials Reliance Prismatic Gages feature quality materials and reliable design. The gage glass is of the highest quality borosilicate glass, tempered for improved toughness. The unique Reliance clamping design produces a uniform, firm, compressive load on the glass adding to gage reliability and prolonged service life.


Prismatic glass is flat on the outside. The inside, in contact with either water or steam, is shaped with multiple 90° angle prisms. Rays of light normal to glass strike the prisms at a 45° angle.

The critical angle of a ray passing from glass to steam is 42°. Therefore, the 45° ray is totally reflected and causes the steam space to appear white.

The critical angle of a ray passing from glass to water is 62°. Therefore, with the 45° angle being less, the ray penetrates the water and reveals the gage housing in black.

Large storage tanks, heater tanks and similar applications call for Prismatic Gage assemblies employing multiple gage sections. Double, triple and quadruple assemblies are available, and even longer assemblies can be provided. In multiple assemblies, the space between gage windows is approximately 1 ½ inches. This gap is generally considered insignificant where multiple assemblies are normally installed.

*In gages of three or more sections, side mounted reinforcing bars connect all gage bodies to assure proper alignment.

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