What are the applications of industrial laser ranging sensors in high-temperature liquid level measurement?

September 23, 2025

Industrial laser ranging sensors have unique advantages and specific application scenarios in high-temperature liquid level measurement.

First, let's clarify the core principle: a laser ranging sensor calculates distance by measuring the time between the emission of a laser pulse and its reflection by an object (time of flight, ToF) or the phase difference. This distance value is converted to the liquid level.

A. Why choose laser ranging sensors for high-temperature liquid level measurement?

Laser sensors are chosen to measure high-temperature liquid levels primarily to address the pain points of other measurement methods. Their core advantages include:

1. Non-contact measurement: This is the advantage. The sensor does not need to come into contact with high temperature, corrosive or viscous media, avoiding the risk of damage, corrosion or adhesion, and has a long service life.

2. Strong anti-interference ability: Lasers are not easily affected by complex working conditions such as high temperature, high pressure, steam, dust, and changes in dielectric constant. In contrast, radar waves may attenuate under certain working conditions (such as large amounts of foam and certain steam).

3. High precision and high resolution: Lasers have excellent focusing capabilities and very small spot sizes (even at long distances), enabling millimeter-level or even higher measurement accuracy and the ability to target very small measurement points (such as conduits or specific areas within a tank).

4. Suitable for extreme high temperatures: As long as the ambient temperature of the sensor's installation location is within its allowable range (usually achieved through air cooling or water cooling jacket), it can measure the surface of any temperature medium, whether it is molten metal at thousands of degrees or high-temperature asphalt.

B. Main Application Scenarios

Laser ranging sensors are particularly suitable for the following high-temperature and high-risk liquid level measurement occasions:

1. Metal smelting and processing

a.	Application scenarios: Continuous monitoring or fixed-point detection of liquid levels of molten iron (blast furnace, ladle, mixing car), molten steel (converter, ladle, tundish), molten aluminum, molten copper, etc.
b.	Value: This allows for control of iron/steel tapping, prevents major safety incidents such as spillage (steel and aluminum leakage), and optimizes the casting process. This is its high-end application area.

 
2. High-temperature chemical and petrochemical raw materials

a.	Application scenarios: Liquid level measurement of high-temperature reactors, polymerization reactors, asphalt tanks, high-temperature oil tanks (such as hot fuel oil), molten salt storage tanks, liquid sulfur, etc.
b.	Value: These media are often highly corrosive, easily solidified, and viscous. Non-contact laser measurement avoids instrument corrosion and clogging, ensuring production safety.

3. Glass manufacturing industry

a.	Application scenarios: Liquid level control in glass melting furnaces (glass liquid), tin baths (float glass), etc.
b.	Value: Precise liquid level control is key to ensuring uniform thickness and stable quality of glass products. Lasers can withstand the high-temperature radiation environment of melting furnaces

 
4. Energy industry (waste-to-energy, biomass power generation)

a.	Application scenario: Drum liquid level measurement of waste heat boiler.
b.	Value: As a high-precision auxiliary or redundant measurement method for traditional differential pressure transmitters, it provides a more direct and reliable reference to ensure safe operation of boilers.

 
5. Cement industry

a.	Application scenario: Material level monitoring of the clinker cooler (grate cooler) at the kiln head of a cement rotary kiln.
b.	Value: Although it measures solid material level, it also faces the challenges of extreme high temperature (red-hot clinker) and high dust. Laser sensors are one of the few technologies that can meet these requirements.

 

C. Important Notes and Limitations

Despite the advantages, the following limitations must be considered and measures taken when applying laser sensors:

1. Surface characteristics to be measured:

a.	Mirror reflection problem: This is the biggest challenge. If the liquid surface is as smooth as a mirror (such as calm molten metal), the laser will be reflected at a fixed angle, and only a small amount of light will return to the sensor, which may cause measurement failure..
b.	Solution: Intentionally create a slight inclination angle (non-vertical incidence), or aim at a fixed, rough measuring point (such as a refractory brick or draft tube installed in the container).
c.	Foam and steam: Although the anti-interference ability is stronger than most technologies, excessively thick foam or dense steam will still severely attenuate or completely block the laser signal.

 
2. Sensor cooling and protection:

a.	The sensor body must be kept away from heat sources. An air purge and water cooling jacket are usually required.
b.	Air purge: Continuously blows clean, dry cold air (or nitrogen) to the sensor lens, which has two functions: 1. Cooling the lens; 2. Preventing dust and smoke from contaminating the lens..
c.	Water cooling jacket: The sensor is installed in a jacket with circulating cooling water to achieve forced cooling of the sensor body, so that it can work in places with extremely high ambient temperature (such as steelmaking workshop).

 
3. Cost:

The cost of high-performance industrial-grade laser ranging sensors that can adapt to extreme working conditions and their cooling protection systems is very high.

 
4. Comparison with other technologies:

Measurement Technology	Principle	Advantage	Disadvantage	High Temperature Liquid Level Applications
Laser ranging	Optical, time of flight	Non-contact, extremely high precision, anti-electromagnetic interference	Non-contact, extremely high precision, anti-electromagnetic interference.	Molten metal, high-temperature chemical media, and occasions requiring extremely high precision.
Radar level meter	Microwave	Non-contact, less affected by steam and dust.	The accuracy is lower than that of laser, and the signal is weak when the dielectric constant is very low	Large high-temperature storage tanks, asphalt tanks, some reactors
Ultrasonic level meter	Sound Wave	Non-contact, low cost	Affected by temperature and pressure, steam and dust attenuation is serious	Generally not used for extreme high temperatures, but can be used for medium and low temperatures
Guided wave radar.	Microwave, contact	Small influence from surface characteristics, high precision	Need to contact the medium, the probe is prone to corrosion, adhesion, and damage:	Not suitable for corrosive, viscous or molten high temperature media

In summary, industrial laser ranging sensors are a high-precision, cutting-edge option for solving the challenges of level measurement in extremely high temperatures and high-risk environments. They are particularly suitable for applications involving molten metals and high-temperature, corrosive chemical raw materials. Their non-contact and high-precision features provide reliable assurance for safe production and process control. However, issues such as surface reflection and sensor cooling must be properly addressed. When selecting a sensor, be sure to discuss the specific operating conditions with the supplier in detail.