The scraper conveyor is the core transport equipment on the fully mechanized mining face of a coal mine, operating continuously under harsh conditions characterized by heavy loads, impact, dust, and high humidity. Issues such as rib spalling, scraper chain jamming, and sudden changes in conveying capacity frequently occur, placing extremely stringent demands on the drive system. Achieving smooth startup, mitigating impact, balancing multi‑unit load distribution, and reducing maintenance costs are critical challenges in the design and retrofitting of scraper conveyor drive systems. As a flexible transmission component, the hydraulic coupling plays an irreplaceable role in this field.

I. Typical Challenges Faced by Scraper Conveyor Drive Systems

In actual operation, the drive system of a scraper conveyor often encounters the following issues:

The starting impact of heavy loads is significant. : Scraper conveyors often require loaded‑start operation; with rigid coupling, the starting current can reach 5 to 7 times the rated value, easily causing power‑grid fluctuations, motor tripping, or even motor burnout.

Severe mechanical impact damage : The enormous torque at startup is directly transmitted to the scraper chain, sprockets, and gearbox, leading to frequent failures such as chain breakage and gear tooth chipping.

Power imbalance in multi-motor drive systems When the head and tail are driven by dual motors, factors such as differences in motor characteristics and uneven sprocket wear can lead to uneven load distribution, causing some motors to operate under prolonged overload conditions.

The fusible plug melts frequently. When the conveyor becomes jammed or operates unevenly, the coupling temperature rises sharply, causing the fusible plug to repeatedly discharge oil. Replacing it is time-consuming and poses a risk of hot oil splashing.

Rapid temperature rise and difficult control of liquid fill volume. : The hydraulic coupling experiences rapid temperature rise during prolonged operation, and inaccurate on-site fluid‑filling control compromises start-up performance and shutdown reliability.

Repeated oil leakage fault : The oil filler plug, thermal protection plug are loose, or the seals have aged, resulting in reduced transmission efficiency and a replenishment rate that cannot keep up with the leakage rate.

II. The Role of the Hydraulic Coupling in Scraper Conveyors

Hydraulic couplings transmit power via a liquid medium and possess inherently flexible transmission characteristics:

Soft start The motor starts nearly under no-load conditions, gradually accelerating the turbine via the hydraulic fluid and thereby reducing the peak inrush current.

Overload protection : Automatically slips to limit torque during sudden load changes, protecting the motor and gearbox.

Multi-machine balancing : By leveraging slip characteristics, each drive point proportionally shares the load, thereby addressing power imbalance among multiple motors.

Vibration damping and cushioning : Absorbs start-up shocks and operational vibrations, extending the service life of chains, sprockets, and gear reducers.

III. Coupling Solutions for ZTE Hydraulic Scraper Conveyors

Guangdong Zhongxing Hydraulic Transmission Co., Ltd. (formerly established in 1958 and formed as a joint venture with Germany’s Voith in 1994) has been deeply engaged in the hydraulic transmission field for decades, offering a comprehensive range of standardized products and customized solutions tailored to the operating conditions of scraper conveyors.

1. Soft start with flexible control, eliminating electrical surges.

By adopting an extended rear auxiliary chamber design, the start-up time is extended to 22–50 seconds, and the peak inrush current is reduced to 1.5–1.8 times the rated value, completely eliminating electrical and mechanical shocks at startup.

2. Automatic load balancing, addressing the challenges of multi-machine driving.

By leveraging the slip characteristics of hydraulic couplings, each drive point proportionally and evenly shares the load, fundamentally mitigating the “load‑sharing” issue in multi‑motor drives.

3. Efficient Heat Dissipation and Reliable Overload Protection

The thermal management design has been optimized, with the slip rate maintained below 4% and transmission efficiency held at 0.96. In the event of overload, the system automatically slips to limit torque; when oil temperature exceeds the threshold, a fusible plug triggers automatic pressure relief, ensuring that only the fusible plug is damaged while the motor and gearbox remain fully protected.

4. High‑standard sealing and easy‑to‑disassemble maintenance

It employs an advanced sealing design to withstand the harsh downhole environment. The standard YOX series offers a maintenance‑free interval of 6–12 months, while the upgraded DXA series extends this to 2–3 years. Its easy‑disassembly design allows the coupling body to be lifted out simply by removing the coupling pin, eliminating the need to move the motor or gearbox.

IV. Application Cases

Case Study 1: Overload Retrofit of a 500 kW Scraper Conveyor at a Coal Mine

The mine’s scraper conveyor is equipped with a 500 kW, 1000 r/min motor. Under full-load operation, it frequently trips due to overload, with the inrush current exceeding six times the rated value. After installing a YOXllz875 hydraulic coupling, the measured inrush current was reduced from six times the rated value to 1.8 times, completely eliminating start-up shock; the full-load slip rate was maintained within 4%, and the transmission efficiency remained at 0.96. Moreover, the maintenance interval has been extended to over 8,000 hours.

Case Study 2: Retrofit of a 280 kW Scraper Conveyor at a Coal Mine in Shanxi Province

Underground scraper conveyors frequently tripped during heavy-load startups, with the motor burning out twice within three months. After installing a YOXvsaz600 torque-limiting hydraulic coupling, the inrush current dropped from a peak of 1,680 A to 950 A, and the torque surge coefficient decreased from 2.8 to 1.25. Over six months of operation, no overload‑related shutdowns have occurred, and the motor bearing temperature rise remains within normal limits.

V. Key Considerations for Selecting Couplings for Scraper Conveyors

Power matching : Select the motor model based on its speed and transmitted power, and allow for a 10%–15% margin to accommodate operating condition variations.

Overload factor : For equipment subject to frequent heavy-duty starts, models with a starting overload factor of ≥1.5 and a braking overload factor of 2–2.5 should be prioritized.

Structural form Coal mine scraper conveyors require an extended start-up sequence to protect the chain; it is recommended to select models with an extended rear auxiliary chamber, with a start-up time of 30–50 seconds being optimal.

Installation interface : Verify the input and output bore diameters, flange dimensions, and overall machine dimensions to ensure alignment accuracy with the existing reducer and motor.

Fluid Fill Volume Control : A properly sized hydraulic flow rate can fully exploit the motor’s peak torque, thereby increasing the starting torque.

VI. Overview of Recommended Models

VII. Corporate Strength and Service Assurance

Guangdong Zhongxing Hydraulic Transmission Co., Ltd. is a national-level high-tech enterprise holding 41 patents. Its “Guangxing” brand fluid couplings enjoy an 85% market share in the domestic torque‑limiting segment and a 60% share in the speed‑regulating segment. The products have obtained coal‑mine safety certification and cover more than 370 specifications. The company traces its origins to a plant established in 1958, and in 1994 entered into a joint venture with Germany’s VOITH, seamlessly integrating cutting-edge international technologies with local operating conditions and mastering a complete technological chain—from materials and processes to system integration.

Zhongxing Hydraulics provides end-to-end technical support to scraper conveyor users, covering selection and calculation, installation and commissioning, and fault diagnosis. Its products are widely employed in fully mechanized mining faces, as well as in the mining, metallurgical, and building materials industries.