Jerguson ® Level Gages
One of the simplest techniques for indicating liquid level is by means of a direct reading device with which the level can be seen visually. A common method of providing such visual indication is by installing direct reading gages in the vessel itself. These direct reading gages are placed at different locations or points to indicate the liquid height. More often, separately mounted gage glasses are used to provide a continuous indication of level over a certain vertical distance on the vessel.
The transparent glass gage consists of a one piece central chamber with cover plates oneach side that hold the two glass windows. The chamber and cover plates have machined recesses that keep all the parts aligned and prevent the gaskets and cushions from shifting. When the level of caustic or acidic fluids is indicated, the inside surfaces of both glasses are lined with a protective coating of transparent mica. After prolonged exposure to high temperature, chemically-treated water, the mica will become opaque. This discoloration indicates that the mica has failed and water is now in direct contact with the glass. When this happens, the glass should be changed, before it fails. See Glass Example
The glass itself is also tempered for resistance to both mechanical and thermal shock. Care must be taken when assembling the unit and tightening the bolts to prevent glass failure. It is safest to use the crossover method of tightening by starting at the center and working outwards.
Besides being suitable for caustic and acidic liquids, the flat glass is also suitable for dirty materials, high pressure steam applications and other service where it is necessary to illuminate the glass from the rear.
The reflex gage is best suited for clean, colorless, non-viscous, and non-corrosive fluids including light and heavy hydrocarbons. This gage has special optical properties that create a sharp line of demarcation at the liquid level. A dark area represents the liquid in the glass gage contrasted by a light area above the liquid. Our Gage & Valve Selector Slide Rule is shown to the right (can't get that from the competition !)