How Wheatstone‘s CoDesigned ExplosionProof Servo Motors Solve Space Constraints with Integrated Compact Structure

In longwall mining, the stage loader (SZZ) is the critical connection between the armoured face conveyor (AFC) and the belt conveyor, transferring coal from the face to the gate road. However, the drive unit of the stage loader is typically located in a confined space between the roadway side wall and the loader head, with hydraulic lines, power cables, and cooling pipes crisscrossing around it. The available space for the motor is extremely limited. Standard motors, due to their large external dimensions and mismatched interfaces, often require adapter plates or long couplings to be fitted, wasting precious space and adding transmission elements and failure points. Jiangsu Wheatstone has adopted a codesign approach for the specific conditions of stage loader drives, integrating the motor profile with the hydraulic pump interface. The motor and pump can be mounted sidebyside or embedded, saving axial and radial space – delivering a “tailormade” power solution for confined underground stage loader drives.

I. Four Core Requirements for Stage Loader Drive Motors

Compact construction – fitting tight installation spaces: The gap between the stage loader head and the roadway side wall may be less than 300 mm. Motor axial length and radial dimensions must be tightly controlled to avoid interference with hydraulic lines and cables.

High starting torque – handling heavyload starts: When starting under full load, the stage loader must overcome chain and material friction, requiring starting torque 23 times rated torque.

Explosion protection and high ingress protection: Stage loaders operate in underground methane and coal dust environments, requiring Ex d I Mb mining safety certification and IP66 or higher ingress protection.

Corrosion resistance and long life: Underground humidity and sulphideladen mine water demand stainless steel or heavyduty anticorrosion coatings.

II. Core Advantages of Wheatstone‘s CoDesigned Servo Motors

1. Integrated codesign – precise matching of motor and hydraulic pump interface: Wheatstone mining explosionproof servo motors are codesigned with the stage loader hydraulic pump interface. The motor flange and pilot dimensions are customised to match the pump mounting dimensions. The motor and pump can be mounted sidebyside or directly embedded into the pump station bracket, eliminating intermediate adapter plates. Axial length is reduced by 2030 % and radial width by 1520 % compared to standard motors, eliminating “won‘t fit, won‘t align” problems.

2. 3× peak overload capacity – handling heavyload starts: The motor delivers peak torque up to 3× rated torque, ensuring smooth, jerkfree fullload starting. In one mine application, the start success rate of the stage loader increased to 99.5 % after upgrading to Wheatstone motors.

3. Ex d I Mb mining safety certification and IP66 protection: MA certified, flamepath surface roughness ≤6.3 μm, IP66 fully sealed, optional 316L stainless steel housing and heavyduty anticorrosion coating.

4. Compact terminal box with side cable entry options: For confined stage loader spaces, the terminal box can be customised with side or bottom cable entry, making cable routing more flexible and avoiding interference with hydraulic lines. Terminal box height is reduced by 30 %.

5. Highprecision speed control: Optional 23bit absolute encoder or resolver, enabling precise speed regulation via VFD to match coal flow variations.

III. RealWorld Application Cases

Case 1 – Stage loader motor codesign retrofit at a mine in Shanxi, China: The original motor‘s axial length was excessive, causing interference with hydraulic lines, preventing proper installation. Wheatstone engineers performed onsite measurements and supplied a codesigned explosionproof servo motor (75 kW, Ex d I Mb, IP66) with axial length reduced by 25 % and a custom flange perfectly matching the pump interface. After installation, the motor ran for 18 months without failure.

Case 2 – Stage loader VFD speed control upgrade at a mine in Shaanxi, China: The original motor ran at fixed speed, causing high starting shock and reducing chain life. After upgrading to a Wheatstone servo motor with VFD for soft starting, starting current was reduced from 1200 A to 400 A, and chain life was extended by 30 %.

Case 3 – Stage loader motor corrosion protection upgrade at a mine in Inner Mongolia, China: The mine water had high sulphide content; the original motor housing corroded within three months. After replacing with a Wheatstone 316L stainless steel housing motor, the motor has run for two years with no corrosion and no seized fasteners.

IV. Selection Guide

Wheatstone offers custom mining explosionproof servo motors with frame sizes 180250 mm, power 45315 kW, voltage AC 660 V / 1140 V, with options for codesigned flanges, side cable entry, stainless steel housing, etc.

V. Conclusion

The stage loader is the “throat” of the longwall face transport system. The compactness and reliability of its drive motor directly affect production continuity. Wheatstone‘s codesigned explosionproof servo motors – with integrated interfaces, short axial dimensions, 3× overload capacity, and IP66 protection – deliver a “tailormade, snugfit” power solution for confined underground stage loader drives.