Equipping silos with “eyes”: An analysis of the application of level gauges in the mining and crushing field.

So, what role do level gauges play in the mining crushing field?

How do we choose the appropriate material level monitoring solution when facing harsh conditions such as high dust levels, large materials, and strong vibrations? This article will provide a detailed analysis.

I. Why are level gauges needed in mining crushing?

The core purpose of material level monitoring in the mining crushing process is to achieve “full feed”—that is, to maintain a suitable material level in the crushing chamber of the crusher. This sounds simple, but it’s not easy to do.

In the past, many mines used manual observation or open-loop control methods, with operators in the control room manually adjusting the feeder frequency based on experience. This method has significant drawbacks:

Efficiency loss: Operators cannot adjust the feed rate in time, the crusher cannot maintain a full feed state, resulting in low hourly efficiency and wasted energy.

Equipment Wear and Tear: Idle operation or unstable material levels in the crusher can cause vertical vibration, leading to damage to hydraulic cylinders, loosening of anchor bolts, and damage to copper bearing sleeves, thus shortening equipment lifespan.

Safety Accidents: Taking a coarse crusher as an example, operators cannot directly observe the material level in the lower hopper. Even slight negligence can cause ore accumulation accidents. Once ore accumulates in the hopper, handling it is extremely difficult and severely impacts production.

Therefore, the mining industry has gradually recognized that equipping hoppers and crushers with reliable “eyes” is a necessary condition for achieving automated and intelligent production.

II. Comparison of Mainstream Level Gauge Technologies: Which is More Suitable for Mines?

Mining environments are characterized by high dust levels, large particle sizes, and strong vibrations, making not all level gauges suitable. The following is a comparison of the performance of several common technologies in mining crushing scenarios:

1. Radar Level Gauge (Non-Contact)

Working Principle: Emits frequency-modulated continuous wave (FMCW) microwave signals and calculates distance by measuring the frequency difference between the emitted and reflected waves.

Applicable Scenarios: Mine level measurement, crusher level measurement, and level monitoring in various silos.

Advantages:
① Strong dust penetration capability; high-frequency radar (e.g., 80GHz) beam focusing, less susceptible to dust interference.

② Unaffected by material repose angle, high reliability.

③ Non-contact, wear-free, and low maintenance cost.

④ High measurement accuracy (millimeter level) and large measuring range (over 100 meters).

Limitations: Higher cost and relatively complex installation and commissioning.

Application Case: In a limestone quarry, the VEGAPULS 67 radar level gauge was installed on a crusher, successfully solving the measurement challenges in low-reflectivity media and dusty environments.

2. Rotary Paddle Level Gauge (Contact Type)
   Working Principle: Driven by a motor, the blades rotate. When material obstructs the blade rotation, a limit signal is triggered.

Applicable Scenarios: Feed hopper blockage detection, high-level alarm in silos.

Advantages:

① Simple structure, low cost

② Sensitive action, reliable alarm

③ Particularly suitable for detecting blockages in lumpy materials

3. Laser Level Gauge
   Working Principle: Emits laser pulses and measures the reflection time difference to calculate distance (Time-of-Flight method).

Applicable Scenarios: Large ore stockpiles, high-precision inventory management.

Advantages: Extremely high accuracy (millimeter level), long measurement distance (up to 500 meters), narrow beam, less susceptible to interference.

Limitations: Laser signal is easily attenuated and scattered by high concentrations of dust; higher cost.

4. Ultrasonic Level Gauge
   Working Principle: Emits ultrasonic pulses and measures the echo time difference.

Advantages: Mature technology, low cost.

Limitations: Weak signal, greatly affected by dust, temperature, and pressure changes; poor reliability in dusty mining environments. Not recommended for high-dust mining crushing scenarios.

III. Selection Recommendations: How to select for different locations in the crushing process? Based on technical characteristics and actual working conditions, here are the selection recommendations for each stage of the crushing production line:

Application Location | Recommended Solution | Key Considerations

Coarse Crusher Lower Hopper | Radar Level Gauge | Large measurement range, strong dust penetration ability

Medium/Fine Crusher Crushing Chamber | Radar Level Gauge + Rotary Paddle Type (Backup) | Real-time monitoring of material level in the crushing chamber, achieving full feeding

Feeding Hopper/Clubbing | Rotary Paddle Type Level Gauge | Detects blockages, achieving interlock control

Buffer Ore Bin/Finished Product Silo | Radar Level Gauge | Non-contact, maintenance-free, continuous and reliable measurement

Vibrating Screen Discharge Hopper | Rotary Paddle Type or Radar (depending on working conditions) | Rotary paddle type can be used for high-level alarm when space is limited

IV. Installation Points: Avoid These Pitfalls

Selecting the right equipment is only the first step; improper installation can also lead to measurement failure. The following are key considerations during installation:

1. Avoid the feed inlet and the main impact zone of the material.

Under vertical discharge conditions (such as chute discharge), the material has a huge impact force on the probe, which can easily cause the probe to bend or be damaged.

Solution: 1. Nest-style installation: The level switch is installed in a side recess, allowing the probe to avoid the main impact path of the material. The critical dimension ‘a’ must be greater than the probe insertion depth to ensure effective protection.

2. High-frequency radar preferred for high-dust environments: In high-dust areas such as inside crushers, ordinary radar signals may suffer severe attenuation. 80GHz high-frequency radar has a more concentrated beam and stronger dust penetration, making it the preferred choice for such conditions.
3. Inclined installation to prevent material buildup: For horizontally installed probes (such as rotary paddle or tuning fork types), a 20° tilt is recommended to prevent material buildup on the probe and avoid malfunctions.
4. Signal integration with control system for interlocking: The value of level gauges lies not only in “seeing” but also in “controlling.” The level signal should be integrated into a PLC or DCS system to achieve automatic interlocking control with the feeding equipment, truly realizing automated production with “full feed.”

The application of level gauges in the mining crushing field has evolved from an early “auxiliary tool” to a “core control element.” It is not only the “eyes” of the silo, but also the nerve endings that enable automated and intelligent production.

By selecting appropriate level gauge technology (high-frequency radar is the preferred choice for harsh mining conditions) and using the correct installation method to connect the signal to the automatic control system, mining companies can significantly improve crushing efficiency, reduce equipment failure rates, and minimize manual intervention costs.