The drying process of the periodical forced circulation […]
The drying process of the periodical forced circulation wood drying room includes: preparation work, control of drying benchmarks, end of drying and storage of dry materials.
Preparatory work before drying includes inspection of drying equipment, establishment or selection of drying benchmarks, determination of medium moisture content and drying quality indicators, sawing inspection boards and test panels and testing their moisture content, timber stacks or timber vehicles entering the drying room, etc.
Equipment inspection: In addition to the regular inspection of the drying equipment, the drying equipment must be checked again before each drying operation, such as changing the gauze for the wet bulb thermometer, changing the balance moisture content test piece, injecting lubricating oil, etc., to ensure that the drying equipment is in good condition. No fault condition.
Develop or select drying benchmarks: Select or formulate drying benchmarks according to the species, specifications, drying quality requirements and performance of drying equipment of the wood to be dried.
Determine the final moisture content and drying quality index: determine the final moisture content and drying quality index according to customer or production requirements. Generally, the final moisture content of dried sawn timber is determined based on the equilibrium moisture content of the area where the timber is used, and the usage of the sawn timber should also be referred to. Generally, the final moisture content of dried sawn timber is 2%-3% lower than the equilibrium moisture content of the sawn timber corresponding to the local average relative humidity. If the dried sawn timber is used indoors, the final moisture content can be lower.
Saw inspection boards and test boards, test their moisture content: each drying must have inspection boards, but there is no need for test boards.
The following precautions should be paid attention to when the pile or truck enters the drying room:
①The wood to be dried in the same drying room must have the same species or similar material properties, the same thickness, and the initial moisture content is basically the same.
② When loading materials, be careful not to damage the door, wall and indoor equipment, and the piles of materials should be parked or stacked stably and neatly.
③The windward side must be filled with piles without leaving gaps. That is to say, for a track-type drying room, the airflow passes through the material pile horizontally, and must be filled along the length and height of the drying room; length direction) and height direction must be filled. If the pile is not enough to fill a room, the width of the total pile (or the number of columns of the pile) can be reduced, but the total length and height of the pile, or the number of nodes and stacks of each row of piles cannot be adjusted. Reduce, so as not to leave voids, short-circuit the airflow, cause uneven drying, and have developed drying defects.
④The piles of sections in the same pile should be as close as possible to each other without leaving gaps, and the front and rear positions of adjacent piles should be slightly staggered so as to avoid unavoidable interpenetration of the end-to-end joints or ends of the piles.
⑤ Pay attention to the heavy objects on the top of the pile.
⑥ Place the moisture content inspection board and stress inspection board. If the electric moisture content measurement method is used, the moisture content measurement points should be at least three, and they should be evenly arranged at different positions in the material pile, and finally the connecting wires should be inserted into the corresponding sockets installed on the chamber wall. If the inspection board weighing method is used, the initial moisture content and initial weight of the moisture content inspection board should be measured, and the total dry weight of the inspection board should be calculated. After the end of the inspection board is sealed with waterproof paint, put it into the inspection window or inspection door piles of wood, and prevent condensation from dripping on it.