Determination of moisture content of plywood

1 Main content and scope of application

This standard specifies the method for measuring the moisture content of plywood as defined by GB9846.2.
This standard applies to plywood consisting of at least three layers of veneers, but also to all other plywood.

2 Reference standard

GB 9846.2 Plywood Terms and Definitions GB 9846.8 Plywood General Plywood Extraction Method GB 9846.9 Plywood Test Piece Saw

3 instruments

3.1 Balance, the reading is accurate to 0.01g.

3.2 Air convection drying oven, the temperature of each point in the box can be maintained at 103±2°C.

3.3 Dryer, use desiccant to make the air in the dryer as close as possible to the dry state.

4 sampling and test pieces

4.1 Extract the sample according to the provisions of GB 9846.8.

4.2 Sawing the test piece according to the provisions of GB 9846.9.

4.3 The test piece can represent the entire cross section of the plate. The test piece should not contain defects such as knots, joint holes and gaps, and the loose pieces and sawdust on the test piece should be removed.

5 procedures

5.1 Weighing of test pieces shall be carried out in the same state as at the time of sampling, to the nearest 0.01g.

Note: The test piece should be sawed immediately after sampling and the first weighing is performed. If this is not possible, precautions should be taken to avoid changes in moisture content from sampling to weighing.

5.2 The test piece is at 103±2°C. Dry to a constant mass at the temperature. Care should be taken not to fill the dry box. When the test piece in the dry box is close to the final weighing condition, do not put a new test piece.

Note: When the weighing result of the test piece is 2h before and after the difference of not more than 0.01g, it can be considered that the constant mass is reached.

5.3 After the test piece is cooled in the desiccator, it is quickly weighed according to the aforementioned accuracy. It is necessary to prevent the water content from increasing by more than 0.1% due to untimely weighing.

6 Calculation and representation of test results

6.1 The moisture content of the test piece shall be expressed by the absolute moisture content, calculated by the following formula, to the nearest 0.1%.


Where: H—the absolute moisture content of the test piece, %:
MH—the quality of the specimen when it is sampled, g;
MO—The quality of the specimen after drying, g.

6.2 The moisture content of one or several sheets is equal to the arithmetic mean of the moisture content of all relevant specimens. This value shall be accurate to 0.1%.

6.3 The above-mentioned calculation of the revised values ​​shall be carried out according to the digital rounding rules of “four rounds, six inputs, five singles and two rounds”.

7 test records and test reports

7.1 The test record shall include the following:

a. the species, type of plywood, and all the details required to identify such plywood;
b. Measured data and calculation results.

7.2 The test report shall include the following:

a. The species, type of plywood, and all the details required to identify such plywood;
b. determining the calculation result;
c. Does not include any operations within this standard, as well as factors that may affect the results of the assay.

Additional information:

This standard is under the jurisdiction of the Institute of Wood Industry of the Chinese Academy of Forestry.

This standard was drafted by the Institute of Wood Industry of the Chinese Academy of Forestry.

The main drafters of this standard: Cao Zhongrong, Huang Zhenghong.

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