Reflex Level Gauge Enables Boiling Liquid Reading

Reflex level gauge, also known as reflex liquid level gauge or reflex glass level gauge, is designed to indicate the liquid level based on the difference in the refractive indices of liquid and vapour. It is highly recommended for colorless liquid.

Reflex level gauge is made in hermetically sealed structure with a reflex gauge glass inside. The reflex gauge glass consists of a smooth face towards the operator and a face having prismatic grooves with section angle of 90° fitted towards the liquid chamber. It is then connected to the vessel to be observed with flanges.

It offers a clear image of the liquid level and reduces the risk of distortion or inaccurate reading, giving a clear, visualized reading. Meanwhile, it can be used in a variety of combination to expand the observation range. In addition, it also has a self-closing function to effectively avoid economic losses and casualties caused by accidents.

Reflex level gauges are widely used for the liquid level measurement of water heaters, deaerators, boiler drums and other types of containers in the fields of petroleum, chemical, power, metallurgy, pharmaceutical, etc.

1-section reflex level gauge and a reflex gauge glass

Reflex level gauge


  • Clear & accurate readings. The reflex gauge glass installed on the reflex level gauge is provided with prismatic grooves and will not create an invisible area, thus proving accurate liquid level images.
  • Boiling liquid reading. The isolation valve at the input of the media entering the chamber can be manually adjusted to reduce the boiling liquid bubbles and offer a clear observed liquid level.
  • Rigid structure. It provides advantages for highly dense and viscous liquids as the body is made of forged construction only.
  • Great flexibility. It can be used in a variety of combinations to fit containers of different sizes and expand the observation area.
  • Self-closing function. The steel ball inside the needle valve at both ends of the reflex level gauge functions as a check valve. In the event of the glass breaking, the steel ball will automatically close the liquid channel under pressure to prevent the liquid from flowing out, thereby reducing economic losses and avoiding casualties.
  • High temperature and high-pressure resistant. It can provide a long-term, stable liquid level measurement under high temperature and high-pressure conditions.
Specification of Reflex Level Gauges
Range of Measurement 300–2000 mm
Operating Pressure 1.6–6.4 MPa
Operating Temperature ≤ 450 °C
Chamber Material Carbon steel or stainless steel
Gauge Glass Material Borosilicate glass, aluminosilicate glass
Surface Treatment Galvanized, power coated, etc.
Visible Range 100–300 mm
Way of Observation Visual inspect from the front view
Way of Connection Flange connection
Note: Reflex level gauges can be customized to match up with the size and shape of containers.


1-section reflex level gauge structure diagram

Reflex level gauge structure diagram

Working Principle

The reflex level gauge is designed to measure the liquid level based on the laws of refraction and reflection of light.

The contact surface between the glass and the liquid is prism-shaped, while the surface for observation is smooth. When the light enters from the smooth surface of the glass vertically, it is then refracted within the liquid, and is not reflected by the inner wall of reflex level gauge.

In the event of the light striking the area of the glass covered by liquid, the area appears dark due to the light refraction; in the event of the light striking the area covered by gas or air, the area appears bright due to the full reflection of the light.

As a result, the reflex level gauge can be used to observe the liquid level changes by discriminating the bright and dark areas of the light.

The working principle diagram of reflex level gauge

Reflex level gauge schematic diagram


1-section reflex level gauge

1-section reflex level gauge

2-section reflex level gauge

Multiple-section reflex level gauge

Notes: This multiple-section reflex level gauge contains 2 and above reflex gauge glasses and is suitable for the liquid level measurement of large containers.


Reflex level gauges are widely used in the fields of petroleum, chemical, power, metallurgy and pharmaceuticals, etc.

  • In the petrochemical plants, it is mainly used to measure the liquid level of oil tanks.
  • In the chemical plants, it is mainly used to measure the liquid level of chemical boilers.
  • In the thermal power plants, it is mainly used to measure the liquid level of boiler drums.
  • In the metallurgic plants, it is mainly used to measure the liquid level of boilers.
Reflex level gauge for chemical boilers

For chemical plants

Multiple-section reflex level gauge for oil tanks in petrochemical plants

For petrochemical plants

Reflex level gauge for boilers in metallurgic plants

For metallurgic plants

Reflex level gauge for thermal power plants

For thermal power plants

An array of tubular gauge glass is vertically placed on the desk.

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