Reflective level gauges (also known as "two-color level gauges" or "bull eye level gauges") work using the principle of optical refraction. The glass of its observation window is not ordinary flat glass, but a special prism structured glass column. When there is a light source shining behind, the prism refracts different media (gas phase and liquid phase), and the observer will see that the gas phase appears red (or white) and the liquid phase appears green (or black), forming a sharp contrast and clearly indicating the liquid level.
Feature:
1. Excellent optical performance
High transmittance: Ensure sufficient light and clear and bright display.
Low bubbles and impurities: Internal defects can affect the propagation of light, causing blind spots or misjudgments in observation.
Accurate prism angle: The oblique angle of the prism is precisely calculated and processed, and is the optical core that produces the "dual color" effect.
2. Extremely high mechanical strength
High pressure resistance: It must be able to withstand the internal pressure of the container, usually ranging from a few megapascals to tens of megapascals in design pressure.
Heat shock resistance: able to withstand rapid temperature changes without breaking (e.g. cold water splashing onto high-temperature glass).
3. Excellent chemical stability (corrosion resistance)
This is one of the most important characteristics. Glass must be able to withstand long-term corrosion from the measured medium, including acids, alkalis, organic solvents, etc.
Corrosion can cause the glass surface to become "hairy" and opaque, which can affect observation in mild cases and lead to a decrease in glass strength and leakage in severe cases.
4. Good thermal stability
It can maintain stable performance within the working temperature range and has a small coefficient of thermal expansion.
二 . Structural form
The glass of a reflective level gauge is usually not a single piece, but is combined with a metal frame to form a "glass plate component" or "observation window module":
1. Glass column: the core optical prism part.
2. Gaskets/Seals: Graphite, polytetrafluoroethylene (PTFE), metal gaskets, etc. are usually used to ensure reliable sealing under pressure and temperature.
3. Cover/frame: Metal parts (such as carbon steel, stainless steel, alloys) are tightened by bolts to press the glass and gasket onto the liquid level gauge body.
三. Key selection points (providing suggestions for users)
When selecting or replacing glass for a reflective level gauge, the following parameters must be confirmed, which are usually engraved on the edge of the glass or in the product manual:
1. Media compatibility: This is the top priority. The chemical name, concentration, and temperature of the process medium must be clearly defined. Select based on the corrosion resistance table of the glass.
2. Working pressure and temperature: The rated pressure of glass must be higher than the maximum working pressure of the container, taking into account the safety factor. Temperature can affect the strength and sealing performance of glass.
3. Glass material code: Inquire or confirm the specific type of glass (such as borosilicate 3.3, aluminum silicon, etc.).
4. Size and connection standards: Ensure that the length, width, thickness, number of prisms, and installation hole spacing of the glass plate match exactly with the original level gauge.
5. Safety standards: Confirm whether the product complies with relevant industry or international safety standards.
