1.What are the core control principles?
Absolute Priority Principle: Avoid "Cold Spots".
When the ambient air temperature is higher than the surface temperature of the steel plate, condensation will form on the steel plate surface. This often occurs in:
Seasons with large diurnal temperature variations (such as spring and autumn).
Cold-rolled coils are transported directly from low-temperature environments (such as outdoor areas in winter or refrigerated transport vehicles) to warm warehouses.
Inadequate ventilation in the warehouse or proximity to cold walls.
Therefore, the core of temperature control is not setting a specific degree, but maintaining a uniform and stable temperature inside the warehouse and on the steel plate, and ensuring it is higher than the dew point temperature of the ambient air.
2.What are the basic safety temperature range and strategies?
Recommended internal temperature: +5℃ to +35℃, and maintain it as constant as possible.
Lower limit +5℃: Primarily to prevent equipment (such as dehumidifiers) from freezing in winter and to ensure operational safety. In cold regions, if there is no temperature control system inside the warehouse, ensure the temperature does not drop below 0℃ to prevent any condensation from freezing and causing further damage.
Upper limit +35℃: Excessively high temperatures can accelerate the volatilization or deterioration of certain rust-preventive oils and affect the working environment. More importantly, the air has a high saturation moisture content at high temperatures, making it easier to reach the dew point when temperatures drop.
Golden rule: Maintain the steel plate temperature at least 2-3℃ higher than the ambient air dew point temperature. This needs to be achieved by controlling the temperature and humidity inside the warehouse.
3.How to prevent condensation caused by "cold materials entering the warehouse"?
Problem: In winter or low-temperature regions, the outdoor temperature is -10℃, and the temperature of the cold-rolled coil is also -10℃. If it is directly placed into a warehouse with a temperature of +20℃, the moist, warm air will immediately condense a large amount of water droplets on the surface of the cold steel plate, causing corrosion within a few hours.
Solutions:
Set up a buffer/heating zone: Establish a temperature transition zone at the warehouse entrance, allowing the steel coils to slowly and naturally warm up to near the warehouse temperature before entering the main storage area.
Control the pace of entry: Avoid placing outdoor steel coils directly into the warehouse during periods of extreme temperature difference (such as at night or early morning).
Pre-ventilate: If the outside air is cold and dry, open the warehouse doors and windows appropriately before entry to lower the temperature inside and reduce the temperature difference.
4.How to prevent condensation caused by diurnal/seasonal temperature differences?
Problem: High temperature and humidity in the warehouse during the day, followed by a sudden drop in temperature at night, causing the surface temperature of the steel plates to fall below the dew point of the air.
Solutions:
Warehouse Insulation: Insulate the warehouse walls and roof to mitigate the impact of external temperature changes on the interior.
Keep Equipment Running at Night: During seasons prone to condensation, continue running dehumidifiers or air conditioners at night to reduce absolute humidity and thus lower the dew point temperature.
Close Doors and Windows: Strictly close warehouse doors and windows during humid nights or early mornings to prevent the intrusion of damp, cold air.
5.Storage considerations for high-value or high-surface-requirement materials?
Requirements: For automotive exterior panels, high-end appliance panels, and mirror-finish stainless steel, a "zero-defect" standard is required.
Countermeasures:
Constant temperature and humidity warehouse: This is the highest standard. Temperature is typically controlled at 20℃ ±5℃, and relative humidity at 50% ±10%. Under these conditions, the dew point temperature is very low (approximately 9℃), and the steel plate temperature is easily maintained above the dew point, virtually eliminating the risk of condensation.
Comprehensive protection: Utilizing vapor phase corrosion inhibitor (VCI) paper, protective films, etc.