Description
Frederickseal Reflex flat gauge glass – a type of sight glass used to visually monitor liquid levels in boilers, tanks, and industrial vessels. Its design uses optical principles to clearly distinguish between the liquid and vapor phases without needing additional lighting or accessories.
Key Features
Flat, machined glass panel mounted in a metal gauge body.
One side of the glass is smooth (the outer side you look at).
The inner side has precision-molded grooves or prisms—this is the “reflex” surface.
Light-reflecting effect:
In the vapor space, light hitting the grooved surface is reflected, appearing bright or silvery.
In the liquid space, light is absorbed, producing a dark appearance.
This strong contrast makes the liquid level highly visible.
How It Works
The prismatic grooves create different optical behaviors:
- Liquid in contact with the grooves reduces light reflection → dark zone.
- Vapor in contact with the grooves reflects light back → bright zone.
This built-in contrast eliminates the need for colored media or external illumination.
Typical Applications
- Boiler drum level indication
- Chemical processing tanks
- Petroleum and petrochemical vessels
- Water treatment equipment
- Storage tanks where clear, easy-to-read level indication is needed
Advantages
- Very clear level indication due to natural light contrast
- No moving parts → highly reliable
- Withstands high pressure and temperature when paired with proper gauge bodies
- Low maintenance
- More economical than transparent gauge glasses
Limitations
- Cannot be used with corrosive media or high-viscosity liquids that may distort optical effects
- Not suitable where visual inspection of the fluid’s color or clarity is required (transparent gauge glasses are used instead)
