FI69576C - FOER FARING FOR EXPLORATION OF FUNCTIONAL VIRKEY I FUKTIGHETSKLASSER - Google Patents

Description

'69576

MEMETELHÄ HAKAU WOOD WAX FOR DISTRIBUTION MOISTURE RESISTANT

The invention relates to a method by means of which wet timber can be divided into categories on the basis of moisture. An example is how the method is suitable for sorting veneer and sawn timber.

5 At present, when veneer is dried, it is not sorted on the basis of moisture, but the veneer sheets are dried mixed, in which case the speed and power of the dryer must be adjusted according to the wettest veneer sheets. In this case, the drying of the drier veneer sheets takes place unnecessarily slowly and, on the other hand, they are dried unnecessarily dry.

According to a study (Pertti Goyrilä, Jarl-Ounnar Salin and Matti Tuominen: Energy Forest Industry Energy Research 1980 - 1982. Optimization of Veneer Drying. State Technical Research Center, Studies 15,156), the moisture content of veneer turned from spruce heartwood ratio ranged from 100 to 207%. According to Gama's study, the moisture ratio of birch veneer varied between 41 and 101 yo. According to a study by F. E. Siimes (Matti Jalava: Wood structure and properties of 20. 1952), the moisture content of the surface wood of growing pine varied between 85 and 200 fr and between heartwood 28 and 42%. Thus, it can be stated that the moisture dispersion of the veneer before drying is very large.

The idea of dividing wet veneer sheets into classes according to humidity has long been known, but the problem has been the lack of a good measurement method, because e.g. electronic humidity meters only work in the humidity range 5 - 30 fr.

With the method according to the invention, the veneer sheets are divided into 50 moisture classes on the basis of basis weight, whereby the determination of the moisture ratio of 2,69576 is only approximate, but still sufficient for optimizing drying.

The method is such that the surface area of the veneer sheet is determined, the sheet is weighed and the microcomputer sorts the veneer sheets into categories based on a weight of 5 square meters, which are thus also approximate moisture classes. In practice, veneer sheets are usually standard size, so their surface area can be fed directly into the computer. If the sheets are of different sizes, their surface area can be measured 10, e.g. with laser equipment.

The following basic values can be taken as a starting point, which are the basis weights of an absolutely dry 1.4 mm girder-thick veneer.

Wood type Weight per square meter g / m2 15 Birch veneer 820

Pine veneer böO

Six veneers 600 These output values can be changed based on factory measurements to exactly match the situation of each of the 20 factories.

The initial basis weight weights of thicker veneers are obtained from these basic values by reduction according to thickness.

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Example: In the case of sorting wet spruce veneer, the sheets can be divided into five moisture classes as follows:

Veneer sheet basis weight, w Moisture ratio, m g / m2% 5 w? 1080 m <60 1080 <w <1320 80 <m X 120 1320 <w <1560 120 <m X 160 1560 <w X 1800 160 <m X 200 1800 <w 200 <m 10 In practice, when delivered by the method according to the invention, the veneer is treated as follows: that after turning the veneer mat is cut into sheets. After the oen, the sheets are fed into measuring-weighing equipment, which sorts the sheets into categories based on moisture. Drying of each of the 15 grades then takes place in an optimal manner, taking into account the initial humidity of the grade. The method achieves significant savings in veneer drying costs. According to the study by Söyrilä et al. With the method according to the invention, the veneer sheets can be divided into more than two categories on the basis of the initial moisture content, so that the advantage to be achieved is even greater. As the moisture variation of pine wood is even greater than that of spruce wood, even more significant cost savings are achieved in drying pine veneer. The moisture dispersion of birch veneer is not nearly as large as that of softwood veneer, so there is no potential for about large savings in drying birch veneer, but the savings achieved in drying 4,69576 birch veneers are also significant.

Next, it is shown how the method according to the invention is suitable for sorting wet sawn timber.

5 At present, when drying sawn timber, before drying, the pieces are in no way sorted according to moisture, but the same load enters sawn timber of different moisture content. In this case, the drying operation must be adjusted according to the wettest pieces, so that the drying of the drier kappa-10 leaves takes place unnecessarily slowly and they are dried unnecessarily dry. The moisture differences of the sawn timber before drying are large, which is due to e.g. that sawn goods from both floated and overland supports may enter the same drying load. From the point of view of optimizing the drying 15, it would be very advantageous for the sawn goods to be divided into categories on the basis of moisture and each category to be dried according to its initial moisture in the most advantageous way possible.

With the method according to the invention, the sawn timber is divided into 20 moisture classes on the basis of weight, whereby the determination of the moisture ratio is only approximate, but still sufficiently accurate from the point of view of optimizing drying. The method according to the invention uses a computer, a scale and measuring equipment, with which it is possible to measure the length of the saw-25 workpiece, e.g. laser equipment. In practice, sorting is done by measuring the length of a piece of sawn timber, weighing it, and the computer divides the pieces into categories based on weight / length value, which are also approximate moisture classes. Only one dimension of lumber is placed in the drying load 30, so that the dimension can be entered directly into the computer and the thickness and width of the lumber need not be measured.

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The following values can be used as a basis for the calculations: The volume weight of pine sawn timber is assumed to be absolutely dry at 430 kg / m3 and spruce sawn timber at 400 kg / a3. In this case, the weight / length-5 values of the most common sawn timber dimensions (i.e. the weight of a one-meter-long piece of sawn timber) in absolute dryness are shown in the table below.

Lumber Weight / length value dimension in absolute dry 10 mm x mm kg / m Pine Spruce 19 X 100 0.617 0.760 19 x 125 1.02 0.950 22 x 100 0.946 0.860 15 22 x 125 1.18 1.10 25 x 100 1, 08 1.00 25 x 125 1.21 1.13 50 x 100 2.15 2.00 50 x 125 2.69 2.50 20 50 x 150 3.23 3.00 50 x 175 3.76 3.50 50 x 200 4.30 4.00 63 x 150 4.06 3.76 63 x 175 4.74 4.41 25 75 x 150 4.84 4.50 75 x 175 5.64 5.25 75 x 200 6 .45 6.00 rz --------— 6 69576

The following table shows by way of example what the weight limits of the moisture classes of a pine board with dimensions of 19 x 100 mm could be.

Weight / length value Moisture ratio 5 w m kg / m% w <1.47 m 80 1.47 <w? 1.80 00 <m t 120 1, 30 <w? 2.12 120 <m Z 160 10 2.12 <w Z 2.49 160 <m '<200 2.45 <w 200 <m

The values shown in the table are examples of how the limit values are in principle determined. All information needs to be adapted to the conditions of each plant.

The method according to the invention achieves significant advantages, the most important of which are: When each moisture class is dried in an optimal manner according to the initial humidity, a large increase in drying capacity and a reduction in energy consumption are achieved.

As the initial moisture dispersion of the sawn timber entering each drying load decreases, the moisture dispersion of the dried article also decreases, which is a significant advantage in terms of the quality of the sawn timber.