1.What is the main function of a coil core (or steel coil spindle)?
Ensuring Production: Stable uncoiling and rewinding on equipment such as rolling mills, galvanizing lines, and annealing furnaces.
Ensuring Storage and Transportation: Serving as a support and stress point during hoisting, stacking, and transportation, bearing the enormous weight of the steel coils themselves.
2.What forces does the core mainly withstand during storage and transportation?
Compression/Radial Pressure: When steel coils are stacked flat ("lay-down"), the core of the bottom coil is compressed by the weight of the coils above.
Bending Stress: When steel coils are placed upright ("standing") and hoisted using C-hooks through the core, the core acts like a beam, bearing the bending force generated by the weight of the entire coil.
3.What are the key factors affecting the load-bearing capacity of a roll core?
Core materials: Steel core: Most common, high strength, reusable. Strongest load-bearing capacity. Fiber core: Used for lighter rolls (such as some aluminum coils, thin steel coils), low cost, for single use. Very limited load-bearing capacity.
Core wall thickness: This is one of the most critical factors. The thicker the wall, the stronger the resistance to compression and bending. Common steel core wall thicknesses range from a few millimeters to over ten millimeters, and are positively correlated with the weight of the steel coil.
Core inner diameter: There are some standard inner diameters in the industry, such as 508mm (20 inches) and 610mm (24 inches). The larger the inner diameter, the more steel can be used for the core (the wall thickness can be thicker), and the stronger the load-bearing capacity is usually.
4.What are the industry-standard practices and "standards"?
Manufacturer Standards: Professional core manufacturers provide the maximum safe load-bearing capacity for cores of different specifications (inner diameter × wall thickness × length) based on the principles of material mechanics. This is the most direct "standard."
Stacking Layer Limits: To ensure safety, there are strict regulations regarding the number of layers of flat-laid steel coils that can be stacked in warehouses and logistics. Generally:
Heaviest steel coils (e.g., >10 tons): Usually stacked in 1 layer.
Medium-weight steel coils: Stacked in a maximum of 2 layers.
Lighter steel coils: Can be stacked in 3 layers, but it must be ensured that the bottom core and foundation have sufficient load-bearing capacity.
Anything exceeding 3 layers is absolutely prohibited, as the pressure on the bottom core increases exponentially.
Safety Factor: When designing the load-bearing capacity of the core, a large safety factor (e.g., 3-5 times) is introduced to ensure safety in unexpected situations such as dynamic impacts (e.g., swaying during hoisting).
5.What are some safe operating guidelines?
Clear Labeling: The weight should be clearly indicated on the label of the steel coil. Ideally, the core should also have a load-bearing marking.
Proper Lifting:
Use vertical C-hooks for lifting, as this is the most stress-friendly method for the core.
When using wire ropes for lifting through the core, corner guards must be installed to prevent the wire rope from cutting the inner wall of the core.
Proper Stacking:
Strictly adhere to the stacking layer limits.
When stacking horizontally, dedicated wooden blocks or supports must be used between layers to ensure alignment of the upper and lower cores and avoid direct compression of the steel strip.
The foundation must be firm and level.
Inspect Core Condition: Before lifting, inspect the core for any visible flattening, cracking, or severe deformation. If any damage is found, stop using it immediately.