Plain glass tube level gauges, also known as sight glass or gauge glass, are tubular glass gauges that are not encased in metal plates. These tubular gauges come in a clear color or with a red line, which improves the visibility of clear liquids. Tubular gauges come in many different diameters and lengths, which are often custom cut to the client’s specifications. Finishes on the ends of tubular glass gauges are seen cut, ground, or polished depending on client specifications. Tubular Glass Gauges are often used in low-pressure applications up to 600 psi.
Transparent Level Gauges
Transparent gauges contain the liquid medium between two pieces of glass on opposing sides of the chamber. Light shines through one side of the gauge, and the level is viewed from the other side. The fluid level is indicated as the result of the different transparency of the two media. Transparent Level Gauges can be purchased with tubular glass or flat glass. While tubular glass is more cost-effective, flat glass designs can better withstand applications with high pressures.
Transparent gauges are a good choice in applications where the actual liquid characteristics need to be seen, as well as with liquid to liquid interfaces and applications with repetitive thermal shock. They can also be used when corrosive liquids are present with the addition of mica shields. Mica shields are used when acidic solutions or hot alkaline are present to protect the integrity of the glass.
Reflex Level Gauges
Reflex glass level gauges work off light refraction and reflection. The glass has several grooves for reflecting prisms. The liquid level is easily identified with different brightness levels of the glass in the liquid and no illumination is required to view the liquid level.
Reflex Level Gauges allow for a better view of clear liquids because they are equipped with special optics that make the liquid visible. Reflex level indicators are often used in high-temperature applications, specifically for boiling liquids. Boiling liquids levels can be hard to read with other types of level gauges since their bubbles make the surface level questionable. The manual adjustment of the isolation valve as the process fluid enters the chamber reduces the bubbling. Reflex Level Gauges are also suitable in applications with high pressures and corrosive process fluids. Reflex level gauges are not suitable for when the interface between two liquids needs to be read.
Magnetic Level Gauges
A magnetic level gauge, or magnetic level indicators measure fluid levels by utilizing a float that rises and falls with the fluid level. The moving of the magnet assembly adjusts a series of bi-color magnetic flags that provide a visual indication of the liquid level. The mechanics of these level indicators are simple are require no power source yet are very effective and reliable at recording liquid levels. They are also virtually maintenance-free, and the magnetic force can affect optional switches or transmitters mounted outside of the chamber.
Magnetic level gauges are used as security against leakages when process fluids are chemically aggressive, poisonous, inflammable or explosive. Magnetic level indicators can be used in a wide variety of applications and are considered alternative to glass gauges.
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