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There is more than one type of level gauge glass you can use for your boiler, oil tank, or other industrial liquid vessel equipment. The two most popular kinds are reflex and transparent.

But what’s the difference between them? Is one sight glass better than the other? 

We answer these questions and more below.


What Is A Reflex Level Gauge Glass?

A reflex glass uses prisms to show the level of liquid inside a vessel. Its interior is divided into two zones: one liquid, one for gas/vapor. When light rays strike the surface of the reflex glass, it is bent to a 45-degree angle. This specific angle has a different effect on each zone. Whereas gas/vapor will reflect the light and emit a bright silver glow, the liquid will refract the light and appear dark.

This stark contrast between light and dark helps the person monitoring the vessel to get an accurate reading of the level of liquid inside.


What Is A Transparent Level Gauge Glass? 

A transparent glass is exactly what it sounds like. It consists of two strong plates of glass that are completely see-through. The liquid rises between these two plates, allowing the observer to determine the fluid levels inside the vessel.

This sight glass does not use prisms of any kind. There is however, a light on the back of it that reflects down onto the person monitoring the gauge. This light allows them to see the separation between the liquid level and the steam/gas/vapor rising off the top of it. 


Which One Should I Use?

Both the reflex and the transparent gauges share many similar characteristics. They can both withstand high temperatures as well as high pressure. If you purchase them from Zight, you will also be guaranteed that they are manufactured with durable, clear tempered borosilicate glass.

In addition, at Zight we manufacture our sight glasses in accordance with DIN 7081, meaning it meets all the standard regulations set by the German Regulatory Institute. We make safe, high quality materials that don’t crack easily under pressure.

So when it comes to which one you should use, it’s not necessarily about which one is better. They’re both great instruments. What you should be thinking about is what you plan to use a sight glass for.

For example, if you need a boiler glass to keep an eye on the water levels in your boiler, you may want to go with the reflex gauge. That’s because reflex gauges are best as measuring the levels of colorless liquids.

On the other hand, if you’re working with a liquid that you need to see the color of, perhaps to monitor how dirty it is, you may want to go with a transparent gauge. Reflex gauges will always show the liquid zone as a dark line. With a transparent glass, you can see the color for yourself without any distortions.

Another smart application of a transparent glass is measuring interface liquids. When two liquids are contained in the same vessel but they don’t mix, like oil and water, they are considered to be interfacing. A transparent level gauge glass will help you monitor both liquids at the same time.

Zight Has You Covered With Both Reflex And Transparent Glasses

Regardless of which one best suits your needs and applications, Zight has you covered. We sell both reflex and transparent glasses. Order them today!