Long-stroke closed-loop systems of the grab bucket: Operating range and dynamic control challenges and solutions
Engineering Significance of the Travel Stroke Setting: For example, A closed-loop travel of 17800mm (17.8 meters) means the grab bucket can perform digging or feeding operations to a depth of nearly 18 meters in the vertical direction.
This typically corresponds to the following working conditions:
Deep silo excavation: such as cement silos, grain silos, etc.
High stack material handling, such as grabbing the top of ore piles or coal piles.
High-height unloading: unloading into high hoppers or trucks.
Technical Problems Arising from Long Strokes
Wire Rope Swaying and Torsion: The longer the rope, the greater its flexibility. During lifting, lowering, and bucket closing, it is prone to lateral swaying and torsion around its axis, leading to positioning difficulties and collisions with the bucket walls.
Tension Fluctuations and Impacts: When the clamshell grab bucket cuts into the material pile, sudden changes in resistance cause drastic changes in wire rope tension. Long rope systems have weak damping effects on tension fluctuations, easily causing impact loads.
Wear Concentration and Reduced Lifespan: During repeated bending over long strokes, the contact sections between the rope and pulleys/drums are prone to concentrated wear at the rope entry and exit points, especially localized crushing and wire breakage along the rope diameter.
Systemic solutions
| problem dimensions | Specific measures |
|---|---|
| Anti-sway and anti-torsion | Equip with a mechanical rope guide or a non-contact laser correction device; adopt independent length measurement and feedback of dual ropes to achieve active torsion control. |
| Tension intelligent control | The hydraulic grab bucket closing system integrates pressure sensors and proportional valves to achieve "resistance-adaptive" bucket closing; the electrical system adopts frequency conversion drive + tension closed-loop algorithm to maintain stable rope tension. |
| Wear extension design | Optimize the hardness and surface smoothness of the rope grooves of the pulleys and drums; use rotating wire ropes to make the wear points change periodically; and regularly fine-tune the rope length to change the bending contact position. |
