Recently, two four-rope iron ore grabs ordered by a Kuwaiti shipowner were successfully assembled and tested, and were officially delivered to the customer. This grab will be matched with the four rope cargo crane of bulk carriers and used for loading and unloading operations of highly abrasive bulk cargo such as iron ore. As a four rope clamshell grab, it controls the opening, closing, and lifting of the grab bucket through the coordinated operation of four steel wire ropes, featuring stable operation and high productivity.
Material optimization plan for iron ore processing conditions
The handling of iron ore is recognized as one of the most extreme working conditions in port operations - the material density typically ranges from 2.5 to 3.5 t/m³, and it is highly abrasive, which places extremely high demands on the wear resistance of all components of the four-rope grab. The grabs delivered this time have undergone refined classification design in material selection, and the selection of each piece of steel corresponds to the actual working conditions:
The side and back plates of the grab shell: Hardox 450
The shell of the grab is responsible for both the overall structural strength and the material carrying capacity. The average hardness of Hardox 450 is 450 HBW. It has excellent wear resistance while also having good toughness and welding performance, making it suitable for parts and structures that need to withstand wear. Using Hardox 450 for the main body of the shell not only ensures the overall structural strength of the grab but also provides convenience for subsequent welding manufacturing.
Internal wear-resistant liners (bottom plate, inner surface of the jaw plates): Hardox 500
The interior of the grab bucket is the area that comes into direct contact with the iron ore and undergoes the most frequent friction. The average hardness of Hardox 500 reaches 500 HBW, enabling it to withstand severe wear and is highly suitable for working in harsh wear environments. Using Hardox 500 for key lining parts such as the bottom plate and inner surface of the jaw plates can significantly extend the service life of the grab in iron ore handling operations.
Cutting edge plate: Hardox 500 + surface tungsten carbide wear-resistant layer
The cutting edge of the four rope clamshell grab is the part that comes into the most intense contact with the materials and experiences the most severe wear during iron ore handling. The cutting edge continuously withstands the impact and grinding of the materials, and its wear resistance directly determines the overall lifespan of the grab bucket.
In this design, on the basis of Hardox 500, the surface of the cutting edge plate is further treated with tungsten carbide overlay - the tungsten carbide-based alloy can have a hardness of over HRC 60, and its wear resistance is 2 to 3 times that of ordinary wear-resistant steel. This "double protection" design enables the cutting edge to possess an anti-wear ability far exceeding that of a single wear-resistant steel plate.
Reinforcing ribs, flanges, and hinge supports: Q355 high-strength steel
For the components that mainly bear structural connections and force transmission in the grab, Q355 high-strength structural steel is selected. Q355 ensures sufficient strength and stiffness while having good welding performance and economy, making the overall structure of the grab more reliable.
The advantages of the four-rope clamshell grab in iron ore handling
The four-rope clamshell grab achieves smooth lifting and precise opening/closing of the grab through the coordinated work of two lifting ropes and two opening/closing ropes. In the handling of iron ore, which is a high-density and highly abrasive material, the load distribution of the four-rope system is more balanced, effectively reducing the fatigue wear of the steel wire ropes and the grab structure. At the same time, the reasonable bucket capacity design and the matching of material density can ensure that each grab operation achieves the best loading efficiency.
Strict assembly and testing
The clamshell grab delivered this time underwent complete assembly and functional testing before leaving the factory. This ensured that all hinge parts, pulley systems and wire rope systems operated smoothly, and the opening and closing actions of the grab were stable and reliable. Each grab carried the commitment to the efficiency of port operations and the lifespan of the equipment.
Conclusion
From the shell to the liner plate, from the cutting edge to the structural components, every material selection of this four-rope iron ore grab has undergone targeted optimization. The combined application of Hardox 450 and Hardox 500, along with the tungsten carbide welding reinforcement on the cutting edge, enables this grab to possess the robustness to handle the extreme wear conditions of iron ore. Its successful delivery once again demonstrates the crucial value of refined material design in port bulk cargo handling equipment.