Accelerated ageing of treated wood prior to biological testing
BS EN 73:2020 pdf free.Durability of wood and wood-based products – Accelerated ageing of treated wood prior to biological testing一Evaporative ageing procedure.
Test specimens are prepared for biological testing against either fungi or insects using the appropriate standards methods. Test specimens are exposed, for a specified period, in a dust-free current of air of a defined velocity and temperature.
Equipment A wind tunnel which is compartmented and fitted with devices for heating and distributing air.
The air shall be dust-free and shall not be polluted by chemical products which could have an effect on the results of biological testing.
The heating and distribution devices shall be such that the temperature and air velocity are maintained constant and uniform in each compartment.
The air leaving the tunnel shall be led away in such a manner that it cannot re-enter the tunnel.
A device which:
a) controls the temperature within the defined limits stated in 72
b) measures and records the air temperature within the defined limits as stated in 22.
An anemometer capable to measuring air velocity of (1 ± 0,3) rn/s.
The test specimens and their preparation are defined in the standards concerning the biological tests to which they are intended to be subjected.
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.
62 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.
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).
Starting and adjustment of the apparatus With the test specimens in position, establish an air current controlled at a temperature of (40土2) °C which enters the compartments at a speed of(1土0,3) m/s.
Maintain the test specimens in the arrangement specified in Zj. and under the conditions specified in 72 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 1800 on its small horizontal axis every two week (14 days) period (see Eigur2).
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 [igurd).
The duration of the exposure period is 12 weeks.
For certain specific applications alternative periods of ageing may be used, in which case the ageing
period should be mentioned in the report of the biological test concerned.
8 Destination of the test specimens after the evaporative ageing procedure
For practical reasons it may not be possible to conduct the biological test immediately after the completion of the ageing procedure. The test specimens may be subjected to the start of the biological test up to a maximum of 12 months following the completion of the ageing procedure.
9 Reference to this document in biological test reports
Quote the evaporative ageing procedure by giving the following information in the biological
— the number of this document (i.e. EN 73:2020)
— the duration of evaporative ageing period and the date ol the start of the biological tests in the test report for each biological test, the duration and conditions of storage ((20 ± 2) °C and (65 ± 5) % relative humidity) of the test specimens between initial preparation and the start of the ageing procedure, the period of time between the completion of the ageing procedure and the start of the biological test;
— the temperature and relative humidity conditions in which the test specimens were kept prior to the start of the biological test, any deviation from the method described in this document.BS EN 73 pdf free download.Accelerated ageing of treated wood prior to biological testing