BS EN 73-2020 pdf free download – Durability of wood and wood-based products — Accelerated ageing of treated wood prior to biological testing — Evaporative ageing procedure
The evaporative ageing procedure shall be carried out no more than 3 months after the end of the preparation of test specimens for testing described in the relevant biological test standard. This includes any treatment and subsequent conditioning period where relevant. An alternative period can be used if specified by the product supplier. This shall be stated in the test report. Prior to testing the specimens may be stored at (20 ± 2) °C and (65 ± 5) % relative humidity. Deviation from this must be stated in the biological report.
6.2 Number of test specimens
The number of test specimens shall allow the relevant biological tests to be carried out in accordance with the instructions in the appropriate standards, bearing in mind that in some tests the evaporative ageing procedure shall be applied to control specimens as well as to test specimens.
The control specimens may be of the following kinds where required by the relevant test standard:
— check test specimens that will not be subjected to attack by biological agents after the evaporative ageing procedure.
These will serve as controls for changes in mass in those tests in which this factor is taken into consideration;
— untreated control or reference species specimens which, after evaporative ageing, are subjected to the test by biological agents to check any variation in the behaviour of the reference species.
7 Procedure
7.1 Arrangement of the test specimens Arrange the test specimens in the compartments on grids made from metal or any other inert material which can be decontaminated, resting them with one of their faces on the base so that none of the other faces is less than 10 mm from the side partitions.
The faces parallel to the grain of the wood shall be parallel to the general direction of air flow and they shall be at least 10 mm from the corresponding faces of the adjacent test specimens. Do not place in the same compartment test specimens of different species, specimens treated with different products or with different concentrations or loadings of the same product, specimens from wood modified using different processes or to different extents, or both test and control specimens:
— test specimens The arrangement of the test specimens may vary from that described above in the following cases:
— test specimens for which the faces perpendicular to the grain of wood are sealed before treatment Arrange the test specimens as above.
The sealed faces may, however, be brought closer together. For example, specimens intended for testing in accordance with EN 118 (termites).
— test specimens with one treated face only Rest the test specimens on the opposite face to that which has been treated. For example, test specimens intended for the test determining preventive action against termites (EN 118) and the larvae of Hylotrupes bajulus (EN 46-2).
7.2 Starting and adjustment of the apparatus With the test specimens in position, establish an air current controlled at a temperature of (40 ± 2) °C which enters the compartments at a speed of (1 ± 0,3) m/s.
7.3 Ageing procedure
Maintain the test specimens in the arrangement specified in 7.1 and under the conditions specified in 7.2 for two weeks (14 days). In order to obtain homogeneous evaporation from all the treated faces of a test specimen, rotate the test specimens through an angle of 180° on its small horizontal axis every two week (14 days) period (see Figure 2).
Test specimens with only one treated surface shall be rotated through an angle of 180° on their vertical axis every two weeks (14 days) period (see Figure 3).
If a compartment contains more than one test specimen, at the same time as rotating the test specimens, change the position of the specimens within this compartment, the method depending on the number of test specimens which it contains and on the duration of the procedure (see Figure 1).BS EN 73 pdf download.