Encoder application in mining machinery

The application of the encoder in mining machinery takes “harsh environment adaptabilit” and “safety and reliability” as the core, and ensures the automatic operation of mining, transportation, lifting and other processes through accurate monitoring of mechanical motion parameters. The following is combined with the typical equipment of mining machinery, and the application scenarios, technical characteristics and explosion-proof design of the encoder are analysed:

Encoder applications in mining excavation and loading equipment

1. Angle monitoring of hydraulic excavators: The boom, stick and bucket joints of hydraulic excavators for open-pit mining (such as large equipment with a bucket capacity of 50m³) need to monitor the angle in real time to achieve accurate excavation trajectory control. A magnetoelectric multiturn absolute encoder (resolution 0.1°) is installed on the piston rod or joint pin of the hydraulic cylinder, and is fed back to the electronic control system by measuring the displacement or rotation angle of the piston. For example, if the boom cylinder stroke is 2.5m, the encoder outputs 10 pulses per 1mm, which can achieve a displacement accuracy of 0.1mm.

2.Harsh environment resistant design: - The shell is made of 316L stainless steel, and the protection level is IP68 (waterproof to a depth of 10m) to resist the erosion of muddy water in the pit; - The vibration resistance level of the magnetic sensitive element is up to 50G (10~2000Hz), which is suitable for the severe impact of excavation operations. Schematic diagram of the installation of the encoder of the excavator section: the encoder is fixed next to the spherical bearing through the flange, the flexible coupling is connected to the rotating shaft, and the output SSI signal is transmitted to the PLC (such as Siemens S7-400) through the explosion-proof junction box, and the “stick angle 45°±0.5°” is displayed in real time.

3.Bucket Position Control for Mining Loaders: Underground mining loaders (such as explosion-proof loaders) need to accurately control the bucket lift height to avoid colliding with the roof when working in narrow tunnels.Solution: Install a magnetostrictive encoder (measuring range 0~3m, accuracy ±0.05%FS) at the bucket cylinder, and transmit the displacement signal through the hydraulic oil, even if the mineral powder adheres to the surface of the cylinder, it does not affect the measurement.

Encoder applications for mine hoisting and hauling systems

1.Precise positioning and safety protection of mine hoist, core requirements: Vertical hoist (depth over 1000m) needs to control the docking accuracy of the tank cage ≤± 50mm, and at the same time prevent 'over-rolling' (lifting the container exceeds the normal terminal position).Technical solution: main encoder: multiturn absolute encoder (such as 24 bits, resolution 1/16777216 turn) is installed at the end of the drum shaft, and the displacement of the tank cage (1 pulse = 4πm/10/16777216≈0.075mm) is calculated by the gear transmission ratio (drum diameter 4m, reduction ratio 1:10);Redundant encoders: Independently install incremental encoders as backups, switch when the main encoder fails, and ensure a safe braking distance of ≤2m.Explosion-proof design: The encoder housing complies with Ex d IMB explosion-proof standard (suitable for underground coal mines), the terminal port adopts flameproof thread, and the internal potting silicone prevents gas ingress.

2.Belt conveyor speed monitoring and slip protection: Long-distance conveyor belts (such as 10km open-pit mine transportation lines) need to monitor the belt speed in real time and trigger a shutdown when the speed deviation exceeds 15% to prevent material accumulation. Encoder selection: Dust-resistant Hall encoder (such as resolution 1024PPR) is used, installed at the shaft end of the driven drum, and the belt speed is calculated by pulse frequency (drum diameter 0.8m, 1024Hz corresponds to belt speed 0.8π×1024/60≈42.7m/s). Anti-dust measures: The encoder is equipped with a stainless steel dust cover and a built-in purge air circuit (connected to compressed air) to continuously remove mineral powder from the surface of the code disc, and the maintenance interval is extended to 12 months.

Encoder applications for mine crushing and screening equipment

1. Cone crusher spindle speed monitoring: When the ore is crushed, the spindle speed (such as 500~1000rpm) needs to be stably controlled to avoid overload and shutdown. When the rotational speed drops by 10%, the system automatically reduces the feed rate. Encoder selection: The high-temperature magnetoelectric encoder (working temperature -40°C~ 120°C) is installed at the non-drive end of the spindle, and is directly driven by the coupling, with strong anti-oil ability (lubricating oil splash does not affect the signal).

2. Vibrating screen amplitude and frequency control, technical scheme: Install an incremental encoder at the eccentric shaft of the vibrating screen, measure the rotation angle of the eccentric block, and calculate the amplitude (such as eccentricity 50mm, speed 1500rpm, amplitude=50×2=100mm). When the encoder detects that the speed fluctuation exceeds 5%, the inverter automatically adjusts the motor frequency compensation. 

Comparison of mine encoder types and adaptation characteristics

Technical challenges and development trends of mine encoders

1. Extreme environmental adaptability challenges--- high temperature and high humidity: the temperature of the underground mining face can reach more than 40 °C, the humidity is 90%, and the encoder needs to pass the damp heat test (40 °C, 95%RH, 1000h no failure). - **Electromagnetic interference**: Mine inverters and motors generate strong electromagnetic pulses when they start, and encoders with a shielding level of ≥80dB (such as metal braided mesh grounding terminals) are required.

2. Intelligent and predictive maintenance trends, sensor fusion: The encoder integrates temperature and vibration sensors to monitor the “code disc temperature rise >60°C” or “vibration acceleration >20G” in real time, and transmit it to the cloud through 4G/5G for early warning (for example, in a mining application case, the encoder bearing wear is predicted 72 hours in advance, and the maintenance cost is reduced by 30%). Wireless encoder: ZigBee or LoRa technology is used to avoid the risk of wear and tear in the roadway for long-distance wiring, and is suitable for mobile equipment (such as mine inspection robots). AI fault diagnosis: Train a neural network based on the encoder's historical data, identify the “abnormal pulse fluctuation”pattern, and predict the gearbox failure (with an accuracy rate of >92%).

Typical case: Renovation of hoist encoder in a metal mine, problems before transformation: The original incremental encoder needs to be shut down and cleaned every month due to the accumulation of mineral dust, resulting in a 15% reduction in the efficiency of the hoist system. Retrofit solution: Replace with EPC 865T explosion-proof encoder with built-in self-cleaning gas circuit (connected to mine compressed air system) and dual-channel signal output (A-B B-). Effect: The maintenance interval was extended to 12 months, the positioning accuracy of the hoist was increased from ±100mm to ±30mm, and the annual output of ore was increased by 200,000 tons.

Summary: In the field of mining machinery, the technological innovation of encoders closely focuses on the three core needs of “explosion-proof, anti-vibration and dust-proof”, and its application not only improves the level of mine automation (such as unmanned mining and intelligent improvement), but also ensures the life safety of underground operators through safety and redundancy design. In the future, with the popularisation of 5G industrial Internet in mines, encoders will develop in the direction of “intelligent perception and edge computing”, and become a key basic component of the digital transformation of mines.