Wood anti-corrosion autoclave

Wood anti-corrosion autoclave is a process of placing wood into a closed pressure vessel after drying, degreasing, and mechanical processing. The majority of the air outside the wood cells is first evacuated under vacuum, and then the anti-corrosion agent is penetrated into the wood cells under a certain pressure and repeated vacuum conditions, so that the wood structure can effectively adapt to various environments and achieve the purpose of anti-corrosion and insect prevention.

The full cell method is to fill the wood cells with a preservative solution, so that the wood retains a large amount of preservatives. This method is suitable for treating wood with water-based wood preservatives, as well as for treating harbor stakes, sleepers, etc. with coal creosote. The operation process can be divided into 5 stages:

1. Pre vacuum stage:

Place the wood into a pressure infusion tank, close the tank door, turn on the vacuum pump, and vacuum the infusion tank (usually -0.080~-0.095MPa) for 15 minutes to 1 hour to extract air from the wood cell cavity, making the wood easy to be infused with preservatives and reducing the backflow of preservatives during pressure relief, retaining more preservatives in the wood. This is also where this method differs from the empty cell method and the modified empty cell method.

2. Stage of adding preservatives:

Add preservative solution without turning off the vacuum pump, while maintaining the original vacuum level. If the vacuum pump is turned off before filling the pressure infusion tank with preservatives, the residual air in the infusion tank or the vapor generated by the treatment solution will be compressed to the upper part of the infusion tank. When the preservative solution continues to be added, these gases will fill the space in the upper part of the wood pile that was evacuated during vacuuming, causing this part of the wood to absorb a smaller amount of preservative solution and resulting in uneven distribution of wood from the same batch of treatment.

3. Pressure stage:

After filling the pressure infusion tank with preservatives, turn off the vacuum pump, eliminate the vacuum, apply pressure (hydraulic or pneumatic), reach the required pressure (usually 0.8-1.5MPa), and maintain it for a period of time (usually 2-6 hours) until the required amount of preservatives has been deeply pressed into the wood, or until the wood refuses to absorb the preservative solution. When the pressurization stage is completed and the pressure is released, due to the expansion effect of a small amount of compressed air in the wood, 5-15% of the preservative solution absorbed by the wood during the pressurization stage will be backwashed out of the wood and returned to the pressure infusion tank.

4. Drainage stage:

After relieving the pressure, use the gravity of the preservative solution or use a drainage pump to return the preservative solution in the pressure immersion tank to the preservative solution storage tank.

5. Post vacuum stage:

After draining the preservative solution, close all valves, connect the vacuum pump, and start the post vacuum stage. The vacuum degree of the rear vacuum can be the same as the front vacuum (-0.080~-0.095MPa), or slightly lower, and maintained for 10~30 minutes. Then release the vacuum and release the preservative solution extracted in the later vacuum stage. After the atmosphere is restored, open the tank door and remove the treated wood. One cycle of anti-corrosion treatment is completed.