AS 1301.014:2019 Methods of test for pulp and paper
6.2  Dry matter content of the sample
The dry matter content of the chips prior to screening shall be greater than 40 % and preferably less than 70 %. Unless it is certain from experience that the dry matter content of the chips is well within the range 40 % to 70 %, determine the dry matter content of the sample according to the oven-drying method in AS/NZS 1301.010s. If the dry matter content of the chips is less than 40 %, they shall be air or oven-dried until their dry matter content is just above 40 %. For precise work the chips shall be air-dried. For less precise work, the chips may be oven-dried. In both cases the chips shall be spread on a tray with a fine mesh wire bottom for drying, and their dry matter content shall be determined following drying. For oven drying, dry the chips in an oven for up to 40 mins at 105 °C ± 3 °C. Protect the chips from gaining or losing moisture following drying. If they have been oven-dried, this shall be stated in the report.
7  Procedure
Bark, rot and any contaminants shall be removed from the sample either before or after classification and weighed separately.
Arrange the screens to form a stack. Mount the stack in or on the shaking frame. Distribute the test sample on the top screen. Start the shaking mechanism and shake the screens for an appropriate time. The length of time for which the stack is shaken is a minimum of 1 min for every litre of chips fractionated.
The particular shaking time, however, may need to be modified depending upon such factors as the type of classifier used, the degree of shaking vigour applied, the particular combination of screens used and the type, volume and moisture content of the wood chips of the test sample. The appropriate shaking time may be determined by a series of trial runs.
After fractionation has ceased, remove the fractions obtained and weigh them immediately to the nearest 0.1 g. The top screen retains the oversize chips. These chips may include card chips. These should be removed from the oversize fraction, weighed and recorded separately. Card chips can either be reported separately or added to the next hole screen fraction if there is a lower screen separating on length.
NOTE  It is essential for the accuracy of the result that the material does not gain or lose moisture after the fractionation. Therefore, weigh the fractions as quickly as possible on a balance placed near the chip classifier.