AS 1301.014 pdf download
AS 1301.014 pdf download.Methods of test for pulp and paper
5 Apparatus
5.1 Chip classifier The chip classifier shall be comprised of several screens and a fines pan mounted above each other in a shaking frame in such a way that there is no loss of chips or fines during screening. 5.1.1 Shaking frame The shaking frame may function in a reciprocating motion (side-to-side) or circular vibrating motion. The frame shall have a mechanism for shaking the screens continuously and vigorously so that screening is completed within the time specified in the procedure. 5.1.2 Screens Screens with holes separate the chips according to length. Screens with slots separate the chips according to thickness. The number of screens in the stack and the dimensions of the screen apertures determine the distribution of the chips between the fractions. Some preferred screen combinations are given below. These are guidelines only, and other configurations and screen apertures are acceptable. Where the apertures are circular, all holes need to be complete circles. Part holes, i.e. at the edges of the screen, are not allowed. If the diameter of the hole is 6.5 mm or less, permissible variation in diameter is 5 %. If the diameter of the hole is greater than 6.5 mm, permissible variation in diameter is 3 %. The holes shall be placed in a pattern of equilateral triangles, and the distance between the centres of adjacent holes shall be the diameter of the hole plus at least 20 %. Screens with slots are generally made up of two rows of parallel rods of diameter 5 mm or 6 mm as illustrated in Figure 2. The slot dimension is the distance between two adjacent rods in different rows. Permissible variation in the slot dimension is 5 %. The slot dimension corresponds to the maximum chip thickness which can pass through the screen.The screens and the fines pan shall be firmly fastened vertically above each other in or on a shaking frame. In all cases measures are to be taken to avoid loss of sample as dust or when emptying the pan before weighing the fines. The dimensions of the screen apertures should be checked regularly. Deposits of sticky material (resin etc.) should be removed with the aid of a solvent such as acetone. NOTE In some classifiers the fines pan is larger than the screen trays and is mounted in a fixed position under the shaking frame. 5.2 Balance The balance shall be capable of weighing the samples to within ±0.1 g.
6 Sampling
6.1 Obtaining the sample Collect a representative wood chip sample. This may present considerable difficulty. The sampling plan needs to be one which is appropriate to the circumstances. In particular, experience has shown that taking samples directly from a chip pile can lead to considerable errors. For this method it is recommended that regular samples be taken from the input to the pile or from the outlet stream moving to the next processing stage. AS/NZS 1301.013rp describes the procedure for sampling of wood chips. Protect the chips from gaining or losing moisture. The test sample size for each fractionation will depend on the dimensions of the screens. Prior to the commencement of screening, the chips should completely cover the top screen to a depth of approximately 40 mm. For example, if the screen area is approximately 0.25 m 2 , then a 10 L sample would be suitable. If the sample has to be subdivided to obtain a test sample of the required size, take precautions to avoid any fractionation of the material. 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.
