1.What factors primarily limit the stacking height of cold-rolled coils?
Steel coil specifications: weight, outer diameter, width, and thickness per coil. Thin coils weighing >=15 tons or with a thickness <=1.0mm are strictly prohibited from being stacked.
Packaging methods: Unpacked coils are strictly prohibited from being stacked; simple packaging (stretch film only) allows a maximum of 2 layers; fully enclosed packaging (rust-proof paper + corner protectors + strapping + inner and outer protective plates) allows for an appropriate increase in the number of layers.
Pallet/saddle structure: The lower pallet must have stacking positioning functions (such as grooves, clips), and the single-layer load-bearing capacity must be no less than 1.5 times the weight of the steel coils placed on it.
Ground conditions: The flatness deviation of the storage area should be <=5mm/2m, and the foundation bearing capacity must meet the total load requirements after stacking.
Storage period: Short-term storage (<1 month) can be appropriately relaxed; long-term storage (>3 months) should reduce the number of layers or be converted to single-layer storage.
2.What is the industry-standard number of stacking layers?
Thin rolls (thickness <=1.5mm) <=8 tons, no more than 2 layers. The bottom layer must use a rigid pallet + anti-deformation pad.
Medium-thickness coils (1.5-3.0mm thick), 8-15 tons, no more than 2 layers. When using 2 layers, the upper and lower coil axes should be aligned.a
Thick rolls (thickness >= 3.0mm) 15-20 tons, no more than 2 layers, single layer recommended. Over 20 tons, stacking is strictly prohibited.
3. How to ensure stability and safety during stacking?
Axis Alignment: The upper layer of steel coils must be perfectly perpendicular to the axis of the lower layer, with an offset not exceeding 5% of the coil width to prevent overturning due to eccentricity.
Contact Surface Protection: A dedicated rubber pad or high-density fiber pad, >=10mm thick, must be placed between the two layers, covering at least 80% of the contact arc surface of the steel coil to prevent localized indentations and slippage.
Anti-Rolling Measures: Anti-rolling blocks must be installed on both sides of the pallet or saddle, with a height not less than 1/5 of the steel coil radius.
Identification Management: Stacked steel coils should be clearly marked with "Number of Stacked Layers," "Stacking Date," and "Overloading Prohibited" warning signs.
4.What are some typical accidents and losses caused by improper stacking?
**Overturning Accident:** In 2022, a coastal warehouse stacked three 18-ton cold-rolled coils in three layers. A minor collision during forklift operation caused the top coil to fall, damaging adjacent coils and resulting in direct economic losses exceeding 800,000 yuan.
**Indentation and Scrap Damage:** An automotive sheet metal processing center stacked two layers of 0.8mm thick cold-rolled coils. Due to insufficient thickness and excessively hard material in the middle layer, indentations up to 3mm deep appeared on the end face of the lower coil, reducing its grade to ordinary material and resulting in a loss of approximately 120,000 yuan.
**Accelerated Corrosion:** When stacked, the gaps between layers are narrow. If the rust-proof packaging is damaged, condensation easily accumulates on the contact surfaces and cannot evaporate, causing corrosion to occur 3-5 times faster than when stored in a single layer.
5.What are the supporting requirements for stacking in warehouse management?
* **Record Management:** Establish a floor plan of the stacking area, marking the specifications, weight, number of stacked layers, and storage date of each stack of steel coils. Strictly adhere to the "first-in, first-out" principle to prevent bottom-layer coils from being compressed for extended periods.
* **Regular Inspection:** Inspect the stacking status at least weekly, focusing on whether the lower pallets have sagged or deformed, whether the rubber pads have aged or shifted, and whether the steel coils are abnormally tilted.
* **Lifting Sequence:** Steel coils must be lifted layer by layer from top to bottom. Directly removing lower-layer coils or moving lower layers before the upper layers have been lifted out is strictly prohibited.
* **Emergency Plan:** Develop an emergency plan for stack collapse, equip sufficient support rods, anti-tipping chains, and other emergency equipment, and provide specialized training to operators.