Seasoning of Wood, Joseph Bernard Wagner [best beach reads txt] 📗
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Fig. 97. The Recording Thermometer.
In Figure 97 is shown the Recording Thermometer for observing and recording the temperatures within a dry kiln, and thus obtaining a check upon its operation. This instrument is constructed to record automatically, upon a circular chart, the temperatures prevailing within the drying room at all times of the day and night, and serves not only as a means of keeping an accurate record of the operation of the dry kiln, but as a valuable check upon the attendant in charge of the drying process.
Fig. 98. The Registering Thermometer.
Fig. 99. The Recording Steam-Pressure Gauge.]
The Registering ThermometerIn Figure 98 is shown the Registering Thermometer, which is a less expensive instrument than that shown in Figure 97, but by its use the maximum and minimum temperatures in the drying room during a given period can be determined.
The Recording Steam GaugeIn Figure 99 is shown the Recording Steam Pressure Gauge, which is used for accurately recording the steam pressures kept in the boilers. This instrument may be mounted near the boilers, or may be located at any distance necessary, giving a true and accurate record of the fluctuations of the steam pressure that may take place within the boilers, and is a check upon both the day and night boiler firemen.
The Troemroid ScalometerIn Figure 100 is shown the Troemroid Scalometer. This instrument is a special scale of extreme accuracy, fitted with agate bearings with screw adjustment for balancing. The beam is graduated from 0 to 2 ounces, divided into 100 parts, each division representing 1-50th of an ounce; and by using the pointer attached to the beam weight, the 1-100th part of an ounce can be weighed.
Fig. 100. The Troemroid Scalometer.
The percentage table No. II has a range from one half of 1 per cent to 30 per cent and is designed for use where extremely fine results are needed, or where a very small amount of moisture is present. Table No. III ranges from 30 per cent up to 90 per cent. These instruments are in three models as described below.
Model A. (One cylinder) ranges from 1⁄2 of 1 per cent to 30 per cent and is to be used for testing moisture contents in kiln-dried and air-dried lumber.
Model B. (Two cylinders) ranges from 1⁄2 of 1 per cent up to 90 per cent and is to be used for testing the moisture contents of kiln-dried, air-dried, and green lumber.
Model C. (One cylinder) ranges from 30 per cent to 90 per cent and is applicable to green lumber only.
Test Samples.—The green boards and all other boards intended for testing should be selected from boards of fair average quality. If air-dried, select one about half way up the height of the pile of lumber. If kiln-dried, two thirds the height of the kiln car. Do not remove the kiln car from the kiln until after the test. Three of four test pieces should be cut from near the middle of the cross-wise section of the board, and 1⁄8 to 3⁄16 inch thick. Remove the superfluous sawdust and splinters. When the test pieces are placed on the scale pan, be sure their weight is less than two ounces and more than 13⁄4 ounces. If necessary, use two or more broken pieces. It is better if the test pieces can be cut off on a fine band saw.
Weighing.—Set the base of the scale on a level surface and accurately balance the scale beam. Put the test pieces on the scale pan and note their weight on the lower edge of the beam. Set the indicator point on the horizontal bar at a number corresponding to this weight, which may be found on the cylinder at the top of the table.
Dry the test pieces on the Electric Heater (Fig. 101) 30 to 40 minutes, or on the engine cylinder two or three hours. Weigh them at once and note the weight. Then turn the cylinder up and at the left of it under the small pointer find the number corresponding to this weight. The percentage of moisture lost is found directly under pointer on the horizontal bar first mentioned. The lower portion on the cylinder Table No. II is an extension of the upper portion, and is manipulated in the same manner except that the bottom line of figures is used for the first weight, and the right side of cylinder for second weight. Turn the cylinder down instead of up when using it.
Examples (Test Pieces)
Model A. Table No. II, Kiln-dried or Air-dried Lumber:
If first weight is 901⁄2 and the second weight is 87, the cylinder table will show the board from which the test pieces were taken had a moisture content of 3.8 per cent.
Model B. Tables No. II and III, Air-dried (also Green and Kiln-dried) Lumber.
If the first weight on lower cylinder is 97 and the second weight is 76, the table will show 21.6 per cent of moisture.
Model C. Table III, Green Lumber:
If the first weight is 94 and the second weight is 51, the table shows 45.8 per cent of moisture.
Saw Mills.—Should test and mark each pile of lumber when first piled in the yard, and later when sold it should be again tested and the two records given to the purchaser.
Factories.—Should test and mark the lumber when first received, and if piled in the yard to be kiln-dried later, it should be tested before going into the dry kiln, and again before being removed, and these records placed on file for future reference.
Kiln-dried lumber piled in storage rooms (without any heat) will absorb 7 to 9 per cent of moisture, and even when so stored should be tested for moisture before being manufactured into the finished product.
Never work lumber through the factory that has more than 5 or 6 per cent of moisture or less than 3 per cent.
Dry storage rooms should be provided with heating coils and properly ventilated.
Oak or any other species of wood that shows 25 or 30 per cent of moisture when going into the dry kiln, will take longer to dry than it would if it contained 15 to 20 per cent, therefore the importance of testing before putting into the kiln as well as when taking it out.
The Electric HeaterIn Figure 101 is shown the Electric Heater. This heater is especially designed to dry quickly the test pieces for use in connection with the Scalometer (see Fig. 100) without charring them. It may be attached to any electric light socket of 110 volts direct or alternating current. A metal rack is provided to hold the test pieces vertically on edge.
Fig. 101. The Electric Heater.
Turn the test pieces over once or twice while drying.
It will require from 20 minutes to one hour to remove all the moisture from the test pieces when placed on this heater, depending on whether they are cut from green, air-dried, or kiln-dried boards.
Test pieces cut from softwoods will dry quicker than those cut from hardwoods.
When the test pieces fail to show any further loss in weight, they are then free from all moisture content.
BIBLIOGRAPHY American Blower Company, Detroit, Mich. Imre, James E., "The Kiln-drying of Gum," The United States Dept. of Agriculture, Division of Forestry. National Dry Kiln Company, Indianapolis, Ind. Prichard, Reuben P., "The Structure of the Common Woods," The United States Dept. of Agriculture, Division of Forestry, Bulletin No. 3. Roth, Filibert, "Timber," The United States Dept. of Agriculture, Division of Forestry, Bulletin No. 10. Standard Dry Kiln Company, Indianapolis, Ind. Sturtevant Company, B. F., Boston, Mass. Tieman, H. D., "The Effects of Moisture upon the Strength and Stiffness of Wood," The United States Dept. of Agriculture, Division of Forestry, Bulletin No. 70. Tieman, H. D., "Principles of Kiln-drying Lumber," The United States Dept. of Agriculture, Division of Forestry. Tieman, H. D., "The Theory of Drying and its Application, etc.," The United States Dept. of Agriculture, Division of Forestry, Bulletin No. 509. The United States Dept. of Agriculture, Division of Forestry, "Check List of the Forest Trees of the United States." The United States Dept. of Agriculture, Division of Forestry, Bulletin No. 37. Von Schrenk, Herman, "Seasoning of Timbers," The United States Dept. of Agriculture, Division of Forestry, Bulletin No. 41. Wagner, J. B., "Cooperage," 1910.
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