The 6 phases of the vacuum impregnation cycle of wood
Phase 1: Initial Vacuum
The pile of wood, once positioned on the powered trolley of the autoclave, is placed inside the plant to start the cycle.
The hermetic closing of the door enables the machine to begin treatment by starting the vacuum pump. This phase, which is very important for the success of the cycle, frees the pores of the wood of air, by generating a “vacuum” which will allow the wood “to breathe” in the preserving solution. The length of the vacuum phase can vary from 30 to 90 minutes according to the characteristics of the wood.
Phase 2: Filling
Once the first phase is over, the vacuum is used to convey the treatment solution from the lower tank to the autoclave positioned above.
A level sensor that sends the plant computer a control signal controls the filling phase.
Phase 3 : Application of pressure
The third treatment phase has the important task of “forcing” the solution into the wood. The pressure pump may operate for from between 30 to 180 minutes depending on the characteristics of the wood. The combined action with the vacuum will enable the active principles to establish themselves deep in the wood thus guaranteeing long lasting protection.
Phase 4: Discharging the solution
On termination of the treatment phases, the solution not absorbed by the wood returns to the lower tank by means of a discharge valve positioned on the bottom of the autoclave.
Special automatic systems top up the salt contents and restore the level of the impregnant so that it is ready for a new cycle. All solution not absorbed is available for a new cycle without any waste.
Phase 5: Recovery vacuum
A further vacuum phase lasting about 20-40 minutes facilitates the bonding of the active principles of the wood.
This phase is important in the “dripping” phase of the material being treated.
Phase 6: End of cycle
At the end of the impregnation cycle the autoclave returns to atmospheric pressure and the wood is ready for the following phases.
Duration of the process
The duration of the cycle varies depending on the following factors:
- Characteristics of the wood;
- Quantity and concentration of the salts required to be administered.