Flat Glass Water Gages - Prismatic Level Gages

Clark Reliance Prismatic Gages provide a well defined, distinct image of water levels, 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, Clark Reliance Prismatic Gages offer the flexibility of combining multiple gage sections to achieve coverage of extended viewing areas.

Available in two designs, "C" Types should be specified for pressures to 250 PSI and "S" Types for pressures to 350 PSI.

Typical Prismatic Gage applications include installation on boiler drums, feedwater heaters, deaerators, and other tanks.

Quality Materials Clark Reliance Prismatic Gages feature quality materials and reliable design. Gage glass is of the highest quality borosilicate glass, tempered for improved toughness against shattering. As an important safety feature, should breakage occur, glass fragments will interlock and remain in place.             

The unique Clark Reliance clamping design produces a uniform, firm, strictly compressive load on the glass adding to gage reliability and prolonged service life. Click for Larger Image of Prismatic Gage

Large storage tanks, heater tanks and similar applications call for Prismatic Gage assemblies employing multiple gage sections. Double, triple and quadruple assemblies are readily available, and even longer assemblies can be provided.

In multiple assemblies, the space between gage windows is approximately 1½ inches. This gap is considered insignificant where multiple assemblies are normally installed.

Note the various dimensions and specifications for multiple gage assemblies listed in tables presented elsewhere on these pages.

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.

When specifying Prismatic Gages, refer to the Vertical Valve Center dimension "A" in the tables provided. Locate the "A" dimension that corresponds to your own gage valve centers.

The over all length of the Prismatic Gage, including nipples, is equal to a Tubular Glass gage length.

A change to Prismatic Gages reduces the length of visible water range 3" to 6" depending upon gage and valve combinations.

Nipples are ¾" diameter. Minimum length of top nipple is 1¾". Minimum length of bottom nipple is 1¾"  when Clark Reliance bronze valves are used.

NOTE: When installing a Prismatic Gage to replace an existing tubular glass gage, a reduction in gage visibility can be avoided by installing an offset assembly. The offset assembly accepts a Prismatic Gage long enough to provide the necessary visibility, using valves rotated 90°.  When ordering, please specify gage valve centers and Clark Reliance Water Column and Valve part numbers.