Durability of wood and wood- based products一Testing and classification of the durability to biological agents of wood and wood -based materials
BS EN 350:2016 pdf free.Durability of wood and wood- based products一Testing and classification of the durability to biological agents of wood and wood -based materials.
4 Sampling of wood and wood-based materials to be tested
4.1 Testing wood species
The origin of test specimens and the number of replicates Is of great Importance for the reliability of the test results.
The reliability of conclusions relating to the durability of a wood species increases with the number and diversity of growing sites from which trees are taken and the number of replicates from those trees. The recommendations given in 4.1.2 to 4.1.3 shall be regarded as minima.
NOTE Background information on sampling can be found in ISO 2859-2 and ISO 3129.
4.1.2 Sampling logs
A log shall be taken from at least 3 trees of the species under test, originating from 3 different sites representative of the diversity of the geographical regions or sites where the tree species grows. Samples should be taken from at least 5 planks, originating from at least 3 trees when only sawn wood is available (see Annex A).
If high between-tree variation Is expected (e.g. different botank species), it’s recommended to test a larger number of trees (e.g. S – 10).
NOTE) It n hr LisrfuI to test In paraIId mitrrIal derived from wixxi %pccw with known dunihility.
Each log shall be of sufficient size to permit the required number of test specimens to be obtained from It.
Each log shall be taken from the main trunk avoiding its extreme ends. Knots and other features which can influence durability shall be avoided.
Sampling shall consider sapwood, heartwood and juvenile wood separately. While testing heartwood. the region within at least 3 cm of the pith shall be excluded in order to avoid juvenile wood, which Is often less resistant than the mature heartwood. For hcartwood sampling, both the Inner (closest to the pith) and the outer (closest to the sapwood and thus including transition wood) parts of the heartwood shall be Incorporated.
NOTE 2 For some species, in order to better assess the variability, there can be a need to sample the transition wood and juvenile wood separately.
For logs of large diameter, a larger number of samples shall be taken from the outer part (outer third of the heartwood radius which Is closest to the sapwood).
For each part of the wood (heartwood. transition wood, sapwood, juvenile wood) to be tested, at least 30 test specimens shall be taken for each test vanable (for example test method or test organism9. A minimum of 6 specimens shall be taken from each log.
Depending on the selected test method. additional specimens might be required to determine the density of the wood species and the moisture content of the specimens. The sampling shall be done according to the relevant standards (ISO 13061.2 for density and ISO 13061-1 for moisture content).
NOTE 3 A scheme of a suitable preparation and distribution of the specimens for testing Is showed in Annex A.
4,1.3 Sampling sawn timber
Wood pbced on the market is mostly available as sawn timber and hence it is difficult to identify pieces originating front specific trees. For this reason, it is preferred to sample as many pieces as possible so as to better estimate the overall durability. A minimum of 30 pieces originating from minimum 5 batches and providIng 1 specimen per piece is required. The general considerations described In 4.1.2 related to sampling also apply for sawn wood.
4.2 Testing of sets of wood
Since timbers are mostly presented on the market as commercial supplies there is a need to assess their durability. A maximum of wood pieces shall be used for the realization of the test specimens (e.g. 2 replicate test specimens from each of 20 pieces are preferred to 10 specimens from each of 4 pieces). To give a good indication on the variability of the tested set of wood, it Is recommended to test at least 30 specimens per variable (for example test method or test organlsm).
4.3 TestIng of wood-based materials
The sampling should take Into account the variability of the wood-based material to be tested.
For each variation in processing parameter (e.g. a change in temperature, particle size, wood species), a minimum of 30 specimens Is required, derived from at least 3 produced items (e.g. boards) sampled at random from 3 different batches. A minimum of 5 specImens from each batch should be tested.
If the material contains both sapwood and hcartwood, care has to be taken that both sapwood and heartwood are used to produce the test specimens.
5 General principles for testing and classification
5.1 General principles for testing wood speciniens
When testing a wood species, an identification of the tree or the wood species shall be done. Wood species shall be specified accordingto EN 13556.
In order to get a homogeneous set of samples in terms of moisture content, the test specimens shall be conditioned pflor to testing in a ventilated conditioning chamber at controlled temperature and relative humidity, until their weight and moisture content are stabilized.
The sample selection requirement for reference specimens shall follow the Instructions of the relevant test method. If several wood species are tested at the same time, one set of reference specimens is sufficient.
Test timber used to determine the durability of a wood species should not be oven-dried at temperatures above 60 °C prior to the test.
If laboratory test vessels are used, reference specimens and test specimens shall be tested In separate vessels.
EN 73 or EN 84 are ageing procedures which might be required prior to biological testing.
The properties of the test specimen shall, as far as possible, be representative for the wood species being tested even it this does not follow the instruction given on sample selection in the relevant test standard. However, the results still cannot be expected to take into account the full range of variation of properties within a species.
EXAMPLE 1: If the test method excudes the use of’ wood of resinous appearance”, but the species to be tested normally has a naturally resinous appearance, this exclusion is ignored.
EXAMPLE 2: If the test method requires a certain number of growth rings per centimetre, this restriction is ignored if growth rings do not exist or are too widely spaced. This is of importance for some tropical timbers,because it is sometimes impossible to see the growth rings; the rings can also correspond not to the annual growth but to the alternation of dry and wet seasons.BS EN 350 pdf download.Durability of wood and wood- based products一Testing and classification of the durability to biological agents of wood and wood -based materials