Fire-retardant wooden fire doors are crucial for ensuring safety in case of a fire, as their performance directly depends on the fire-resistance limit. To maintain this standard, many manufacturers treat the wood with flame-retardant chemicals during production. However, due to the lack of standardized procedures, different companies use varying techniques, often leading to inconsistent and unreliable results. In some cases, the fire resistance of the door can be compromised, which may pose serious risks to human lives and property.
Common flame-retardant methods for wood include spraying, soaking, steaming, vacuuming, and pressurization. While spraying and soaking are typically used for thin or surface-treated wood, they are not suitable for manufacturing fire doors due to limited penetration. Vacuum and pressurization methods offer better flame resistance but require expensive equipment, which is why they are rarely used in local fire door production. Most companies in our region rely on the steam cooking method. When using this technique, several key factors should be considered to ensure effective flame retardation.
First, the moisture content of the wood plays a significant role in determining the effectiveness of flame retardant treatment. Dry wood tends to absorb more flame-retardant liquid, which enhances its fire resistance. The higher the absorption, the better the oxygen index and flame-retardant depth. However, many manufacturers overlook this factor, treating wet or freshly cut wood without drying it first. This leads to unstable results. Studies show that wood with a moisture content below 15% can achieve an oxygen index increase of over 5 points and a flame-retardant depth of more than 3 mm, compared to wood with over 40% moisture.
Second, the sequence of the flame-retardant process matters. Some companies follow the order: wood → flame retardant → water → start. This approach may cause the wood to absorb low-concentration solutions initially, which affects the overall quality. A better approach is to first prepare the flame-retardant solution at the correct concentration before adding it to the pool. This ensures the wood absorbs the right amount from the beginning, improving the effectiveness of the treatment.
Third, controlling evaporation is essential. During the heating process, if water is added too frequently, the concentration of the flame-retardant solution fluctuates, reducing its efficiency. To avoid this, companies should minimize water addition and maintain a stable concentration. If water must be added, it should be done carefully with high-quality flame retardant to keep the solution consistent.
Finally, discharging the wood at room temperature is important. Many manufacturers discharge the wood immediately after the required time, without allowing it to cool. However, cooling allows the wood to create internal negative pressure, which helps further absorb the flame retardant. This step not only improves the quality but also protects workers from heat exposure during the process.