Field test method for determining the relative protective effectiveness of a wood preservative in ground contact

This European Standard specifies a field test method for evaluating the effectiveness of wood preservatives in a ground contact situation. Wood treated with a reference preservative is included for comparison.
The protective effect of the test preservative is assessed in relation to the effect of a reference wood preservative applied by a specified treatment.

Freiland-Prüfverfahren zur Bestimmung der relativen Schutzwirkung eines Holzchutzmittels im Erdkontakt

Diese Europäische Norm legt ein Freiland-Prüfverfahren zur Bewertung der Wirksamkeit von Holzschutzmitteln bei Erdkontakt fest. Zum Vergleich wird mit einem Referenzschutzmittel behandeltes Holz eingesetzt.
Die Schutzwirkung des zu prüfenden Holzschutzmittels wird bewertet in Bezug auf die Wirkung eines Referenz-Holzschutzmittels, das mithilfe eines festgelegten Behandlungsverfahrens eingebracht wurde.

Essai de champ pour déterminer l'efficacité protectrice relative d'un produit de préservation du bois en contact avec le sol

La présente Norme européenne décrit une méthode d'essai de champ permettant d'évaluer l'efficacité des produits de préservation du bois dans une situation de contact avec le sol. Du bois traité avec un produit de préservation de référence est inclus à des fins de comparaison.
L'effet protecteur du produit de préservation soumis à essai est déterminé comparativement à celui d'un produit de préservation du bois de référence appliqué selon une méthode normalisée.

Terenska preskusna metoda za ugotavljanje relativne preventivne učinkovitosti zaščitnega sredstva za les v stiku z zemljo

Ta standard določa metodo za ugotavljanje relativne preventivne učinkovitosti zaščitnega sredstva za les v stiku z zemljo.

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Published
Publication Date
04-Nov-2014
Current Stage
9093 - Decision to confirm - Review Enquiry
Completion Date
19-Nov-2020

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EN 252:2015
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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.þLQNRYLWRVWLFreiland-Prüfverfahren zur Bestimmung der relativen Schutzwirkung eines Holzchutmittels im ErdkontaktEssai de champ pour déterminer l'efficacité protectrice relative d'un produit de préservation du bois en contact avec le solField test method for determining the relative protective effectiveness of a wood preservative in ground contact71.100.50Wood-protecting chemicalsICS:Ta slovenski standard je istoveten z:EN 252:2014SIST EN 252:2015en,fr,de01-januar-2015SIST EN 252:2015SLOVENSKI

STANDARDSIST EN 252:2004/AC1:2004SIST EN 252:20041DGRPHãþD
SIST EN 252:2015
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 252
November 2014 ICS 71.100.50 Supersedes EN 252:1989English Version

Field test method for determining the relative protective effectiveness of a wood preservative in ground contact

Essai de champ pour déterminer l'efficacité protectrice relative d'un produit de préservation du bois en contact avec le sol

Freiland-Prüfverfahren zur Bestimmung der relativen Schutzwirkung eines Holzchutzmittels im Erdkontakt This European Standard was approved by CEN on 30 August 2014.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre:
Avenue Marnix 17,

B-1000 Brussels © 2014 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 252:2014 ESIST EN 252:2015

EN 252:2014 (E) 2 Contents Page Foreword ..............................................................................................................................................................4 Introduction .........................................................................................................................................................5 1 Scope ......................................................................................................................................................6 2 Principle ..................................................................................................................................................6 3 Wood specimens ...................................................................................................................................6 3.1 Wood species .........................................................................................................................................6 3.2 Wood quality ..........................................................................................................................................6 3.3 Characteristics and dimension of stakes ............................................................................................6 3.4 Number of Stakes ..................................................................................................................................7 3.5 Labelling of stakes.................................................................................................................................7 4 Sample of wood preservative ...............................................................................................................7 5 Conditioning and treatment of the stakes ...........................................................................................7 5.1 Conditioning ...........................................................................................................................................7 5.2 Treating process ....................................................................................................................................7 5.3 Determination of retention of wood preservative product ................................................................8 5.4 Range of preservative retention ...........................................................................................................8 5.5 Post treatment conditioning of stakes ................................................................................................8 6 Reference stakes ...................................................................................................................................8 6.1 Reference preservative .........................................................................................................................8 6.2 Alternative reference preservative .......................................................................................................9 7 Untreated control stakes .......................................................................................................................9 8 Condition of the test field .....................................................................................................................9 9 Installation of the stakes in the test field ......................................................................................... 10 10 Inspections .......................................................................................................................................... 10 11 Evaluation ............................................................................................................................................ 11 11.1 General ................................................................................................................................................. 11 11.2 Attack by microorganisms ................................................................................................................. 11 11.3 Attack by termites ............................................................................................................................... 11 11.4 Simultaneous attack by microorganisms and termites .................................................................. 12 12 Duration of the test ............................................................................................................................. 12 13 Conditions for the validity of the test ............................................................................................... 12 14 Test report ........................................................................................................................................... 12 Annex A (informative)

Guidance for the testing of wood or wood based products that have not been treated with a wood preservative ............................................................................................ 15 Annex B (informative)

Characterization of the field test site ....................................................................... 17 Annex C (informative)

Example of pattern for setting up field stakes into the ground ............................ 18 SIST EN 252:2015

EN 252:2014 (E) 3 Annex D (informative)

Determination of strength characteristics in wood stakes through measuring Modulus of Elasticity ....................................................................................................... 19 Annex E (informative)

Example of a test report ............................................................................................. 21 Bibliography ...................................................................................................................................................... 24

SIST EN 252:2015

EN 252:2014 (E) 4 Foreword This document (EN 252:2014) has been prepared by Technical Committee CEN/TC 38 “Durability of wood and wood-based products”, the secretariat of which is held by AFNOR. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by May 2015 and conflicting national standards shall be withdrawn at the latest by May 2015. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. This document supersedes EN 252:1989. In relation to the previous version of the standard, the following main modifications have been made: — change in the assessment criteria for fungal decay; — minor changes in the description of termite attack; — the addition of informative annexes concerning the determination of strength characteristics in wood stakes by measuring the modulus of elasticity; the characterization of field test sites and the setting-out of the test stakes in the field test sites. According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. SIST EN 252:2015

EN 252:2014 (E) 5 Introduction The method is primarily concerned with protection against microbial attack. However, it is also capable of being used in areas where a termite hazard exists. It should also be noted that microbial decay may alter the resistance of a stake to termite attack and that termite attack may obliterate evidence of microbial decay. This field method provides one criterion by which the effectiveness of a wood preservative product can be assessed in a ground contact situation (Use Class 4 according to EN 335). The main objective of the method described is to evaluate the effectiveness of a preservative relative to a reference material. For this reason permeable timbers are used throughout so that the protective efficacy of various retentions of wood preservative can be determined. NOTE Informative Annex A gives guidance for testing wood or wood based products in ground contact that have or have not been treated with a wood preservative. SIST EN 252:2015

EN 252:2014 (E) 6 1 Scope This European Standard specifies a field test method for evaluating the effectiveness of wood preservatives in a ground contact situation. Wood treated with a reference preservative is included for comparison. The protective effect of the test preservative is assessed in relation to the effect of a reference wood preservative applied by a specified treatment. 2 Principle Wooden stakes are treated with preservative solutions to give a range of preservative retentions. After drying and, if necessary, an appropriate fixation period, the stakes are partially buried in soil in selected test fields in the open. The stakes are regularly inspected and their condition compared with that of untreated controls and that of a group of stakes treated with a reference preservative both of which indicate the aggressiveness of the individual field. The different agents of attack and their respective intensities are recorded. 3 Wood specimens 3.1 Wood species Susceptible wood species that can be completely penetrated with preservative shall be chosen as follows: — for every test the sapwood of Scots Pine (Pinus sylvestris (L)), shall be used; — it is recommended that a hardwood species of local importance is included if the preservative is expected to be used in this type of wood; — if desired other wood species may be incorporated in the test. 3.2 Wood quality The wood shall be straight-grained and free from knots, cracks, stain, decay, insect holes, reaction wood or other defects. Test stakes with a resinous appearance shall be avoided. The wood shall not have been water-stored, floated, chemically treated or steamed or dried at a temperature above 60 °C. The Scots Pine sapwood shall show an average rate of growth of 2,5 to 10 annual rings per 10 mm. If additional wood species are to be used the range in the number of annual rings per 10 mm for each species shall be mentioned in the report. The test report shall also include the mean density and moisture content for the wood used in the preparation of the stakes. 3.3 Characteristics and dimension of stakes The boards shall be conditioned at (20 ± 2) °C, (65 ± 5) % relative humidity. Stakes for test shall be cut from the test wood(s) as follows: SIST EN 252:2015

EN 252:2014 (E) 7 — Each stake shall be planed to within the thickness tolerance indicated. When viewed at the cross-cut end, the rings shall be oriented tangentially to one of the 50 mm edges within the limits (0 ± 25)°; — The dimensions shall be: (500 ± 2) mm x (50 ± 1) mm x (25 ± 0,5) mm when measured at a moisture content of (12 ± 2) % (mass fraction). Each test shall be carried out with stakes of comparable density and any stakes in a test batch which have densities outside the range of 15 % of the mean density shall be rejected. Additional stakes of different dimensions may also be included in the tests. 3.4 Number of Stakes At least 10 stakes per field for each wood preservative and retention shall be tested. A greater number of stakes shall be treated so that stakes with deviating retentions can be rejected (5.3). Additional stakes may also be included for chemical analysis, to aid determination of retentions and/or penetration/distribution (see 5.3). To assess the virulence of the field conditions a series of at least 10 untreated control stakes shall be included in each field (see Clause 7). Include in each field at least two series of 10 standard reference stakes of Scots Pine treated according to 5.2 with a reference preservative (see Clause 6). 3.5 Labelling of stakes Each stake shall be labelled with an inert, long-lasting label or tag. NOTE A map of the position of each stake within the site is desirable. 4 Sample of wood preservative The sample shall be representative of the wood preservative to be tested. It shall be stored and handled in accordance with written recommendations from the manufacturer. It is recommended to chemically quantify the active ingredients content. 5 Conditioning and treatment of the stakes 5.1 Conditioning The stakes should be conditioned in conditions to reach constant mass at (20 ± 2) °C and (65 ± 5) %RH. The stakes shall be air-dried indoors, to a moisture content at which a good penetration of the wood preservative can be obtained. For vacuum / pressure processes the moisture content of the specimens shall be (12 ± 2) % (mass fraction). 5.2 Treating process For the reference stakes and unless otherwise specified for the test stakes a full-cell process is to be used. A typical full-cell process has an initial vacuum which shall be less than 10 kPa (0,10 bar) and maintained for at SIST EN 252:2015

EN 252:2014 (E) 8 least 30 min. Pressure of at least 1 MPa (10 bar) shall be applied for at least 90 min. Complete records of treatment shall be made for each charge. 5.3 Determination of retention of wood preservative product Calculate the volume of each stake before treatment from its dimensions (see Clause 3). If shaped to a point before treatment this shall be taken into account in the calculation. Determine the mass of each stake by weighing to the nearest 0,5 g. After treatment, allow the stake to drain for several minutes. Reweigh each stake to the nearest 0,5 g to determine the mass of treatment solution absorbed. Calculate the retention value of each stake from the mass of treatment solution absorbed, the concentration of the treating solution and the calculated stake volume. Express the retention of the wood preservative product as kilograms per cubic metre of wood. Calculate the mean retention for each series of test stakes. Stakes with individual retentions deviating by more than 10 % from the mean value shall be rejected. 5.4 Range of preservative retention Test each preservative with at least three and preferably five different retention levels. These different levels shall be achieved by using fresh preservative solutions at different dilutions and without varying the treatment conditions. Use a fresh solution at each dilution; the dilution of a quantity of solution which has been used already may be unsatisfactory because preferential absorption may have occurred during the previous treatment schedule. 5.5 Post treatment conditioning of stakes For those products requiring a fixation period the recommendations of the wood preservative manufacturer should be followed. For the reference preservatives the stakes shall first be close-stacked, each retention group separately, and kept wrapped for an appropriate period (at least 3 weeks) at room temperature (above 15 °C) in polyethylene or similar non water permeable material to avoid rapid drying. For drying after fixation, make open piles protected from rain and frost, with inert spacers to allow air flow between the stakes. 6 Reference stakes 6.1 Reference preservative Stakes of Scots Pine sapwood shall be treated according to 5.2 using the reference preservative, with the following composition: CuSO4.5H2O

35,0 % mass fraction K2Cr2O7
45,0 % mass fraction As2O5 .2H2O

20,0 % mass fraction Chemical purity of individual components should be at least 98 %. SIST EN 252:2015

EN 252:2014 (E) 9 Two dry salt retentions shall be used approximating to 2 kg/m3, and 9 kg/m3 respectively. The precise retentions obtained will be dependent on the concentration and uptake of the treating solution. NOTE 1 Alternative raw materials could be used providing the same metal balance is achieved. In terms of elemental metal these retentions equate to the following: — 2 kg/m3 dry salt retention: 0,18 kg/m3 copper, 0,32 kg/m3 chromium, 0,23 kg/m3 arsenic; — 9 kg/m3 dry salt retention: 0,80 kg/m3 copper, 1,43 kg/m3 chromium, 1,02 kg/m3 arsenic. NOTE 2 It is possible to use a third concentration at 6 kg/m3 to provide additional information. As a result of the implementation of the Biocidal Products Directive 98/8/EC there are restrictions in the use of chromium- containing wood preservatives. 6.2 Alternative reference preservative If it is not possible to use a wood preservative containing arsenic the reference stakes shall be treated with an alternative preservative. This preservative shall have the following composition: CuSO4.5H2O 50,0 % mass fraction K2Cr2O7 48,0 % mass fraction CrO3 2,0 % mass fraction Chemical purity of individual components should be at least 98 %. Two dry salt retentions shall be used approximating to 4 kg/m3 and 17 kg/m3 respectively. The precise retentions obtained will be dependent on the concentration and uptake of the wood preservative treatment solution. NOTE Alternative raw materials could be used providing the same metal balance is achieved. In terms of elemental metal these retentions equate to the following: — 4 kg/m3 dry salt retention: 0,51 kg/m3 copper, 0,72 kg/m3 chromium; — 17 kg/m3 dry salt retention: 2,16 kg/m3 copper, 3,06 kg/m3 chromium. 7 Untreated control stakes A series of at least 10 untreated control stakes shall be included in each test field. These stakes shall be interspersed between the stakes treated with the wood preservative product(s). 8 Condition of the test field In order to promote reproducibility and to reduce variation in the test results, avoid overabundant vegetation on the field. The vegetation shall be cut by physical means and in such a way that the buried stakes remain untouched. Chemicals to control the growth of vegetation (herbicides) may affect the fungal attack and shall therefore not be used. SIST EN 252:2015

EN 252:2014 (E) 10 Information about test field quality and characterization is given in informative Annex B. 9 Installation of the stakes in the test field The stakes of each test series shall be installed vertically with at least 300 mm between the stakes. Stakes shall be buried to half their length. NOTE 1 A template aids installation. Stakes of the same type (preservative and retention) shall be distributed across the test plot. An example of a distribution pattern is given in informative Annex C. The stakes shall not be hammered down into the soil, since this may damage the wood (fractures, splits) and influence the test results. NOTE 2 A spike, spade or other convenient tool can be used to make a suitable hole in the ground. Having inserted the stake in the hole it is important to press the surrounding soil tight to the stake so that a good contact is achieved between the soil and all the surfaces of the buried half of the stake. 10 Inspections The stakes shall be examined annually. Inspections after a long dry period should be avoided. However, inspection during rain should be avoided as this also makes evaluation difficult. Withdraw the stake from the ground by a straight upward pull and remove carefully the soil adhering to it while ensuring that the stake and its test position are not unduly damaged. Should the stake be difficult to withdraw, gentle waggling and tapping perpendicular to the narrow plane of the stake is permissible. Examine all sides of the stake for the presence of symptoms of changes in the wood. It is not necessary to use magnification. To determine any change in surface hardness of the wood a blunt pointed instrument can be used for probing. However, the stake should be inspected without undue mutilation or removal of softened wood as this would destroy the surface of the wood and alter the test conditions. The stakes shall be rated according to Clause 11. In case a rating 3 is recorded, a light blow on one of the 50 mm wide face shall be administered in order to assess if a rating 4 is appropriate. If possible, the type of decay shall be recorded. These include white and brown rot, soft rot and bacterial attack. After the inspection the stake is carefully re-installed into its original hole. The soil is carefully pressed against it so that a good contact is ensured between the soil and the surfaces of the buried part of the stake. The half of the stake that had been in the ground before shall be inserted again. Other examinations, e.g. bending tests under carefully controlled conditions, may be carried out at these intermediate times (see informative Annex D). SIST EN 252:2015

EN 252:2014 (E) 11 11 Evaluation 11.1 General The evaluation of the extent of attack is based on a number of observations which cannot be measured in absolute terms. In addition the apparent condition of an individual stake may vary slightly from time to time depending on the climatic conditions before and during the inspection. It is therefore important not to make the rating procedure elaborate. If there is any uncertainty which rating a stake should be given, it is strongly recommended that the lower rating be used. 11.2 Attack by microorganisms Usually fungi are the most destructive microorganisms on wood in ground contact. The rating system described in Table 1 shall be used to assess the extent of attack on the stake caused by microorganisms. Table 1 — Rating system for the assessment of attack caused by microorganisms on test stakes Rating Classification Definition 0 No attack No change perceptible by the means at the disposal of the inspector in the field. If only a change of colour is observed, It shall be rated 0. 1 Slight attack Perceptible changes, but very limited in their intensity and their position or distribution: changes which only reveal themselves externally by superficial degradation, softening of the wood being the most common symptom. 2 Moderate attack Clear changes: softening of the wood to a depth of at least 2 mm over a surface area covering at least 10 cm2, or softening to a depth of at least 5 mm over a surface area less than 1 cm2. 3 Severe attack Severe changes: marked decay in the wood to a depth of at least 3 mm over a wider surface (covering at least 25 cm2), or softening to a depth of at least 10 mm over a more limited surface area. 4 Failure Impact failure of the stake in the field. By adding up the ratings for all stakes in each retention group and dividing by the number of stakes, a notional average rating is obtained for each retention of the wood preservative that has been tested. If all stakes at a given retention have failed (average rating 4) the average life of stakes in the group is calculated together with the standard deviation. In field test sites where wood destroying termites are present, the termite rating and fungal rating are noted and both are recorded in the test report. The final rating of each stake is given as the higher of the two (termites or fungi). 11.3 Attack by termites The evaluation of the extent of termite attack shall be made separately according to the rating system described in Table 2. SIST EN 252:2015

EN 252:2014 (E) 12 Table 2 — Rating system for the assessment of attack by termites on test stakes Rating Classification Definition of condition 0 No attack No sign of attack 1 Slight attack Perceptible, but slight attack, taking the form of a very superficial deterioration of approximately 1 mm to 2 mm deep, at some points or over small areas 2 Moderate attack Moderate attack shown by deteriorated areas covering several cm2 and 2 mm to 5 mm deep, or by scattered points down to a depth exceeding 5 mm, or by different combinations of the two types of attack 3 Severe attack Severe attack, showing extended and deep destruction of approximately 5 mm to 10 mm or tunnels reaching to the centre of the stake, or by different combinations of the two types of severe attack 4 Failure Extreme attack: overall generalized penetration involving a total or almost total destruction of the stake. 11.4 Simultaneous attack by microorganisms and termites In the case of a simultaneous attack by microorganisms and termites the final rating for each stake is given by the higher degree of attack. Both ratings are recorded and reported. 12 Duration of the test The test shall be run for a minimum period of five years (or until all stakes have failed if this occurs earlier). It is advisable to continue the test beyond five years, with inspections at suitable intervals, in order to determine longer performance of the treated stakes. Ideally the test should be continued until all stakes of the product under test have failed. 13 Conditions for the validity of the test The test is valid when: — at least 75 % of untreated stakes are rated 4; — the median rating for the reference stakes at the lower retention is not less than 2,0; — signs of decay exist in at least one stake for the reference stakes at the highest retention. 14 Test report A test report shall indicate: a) the number of this European Standard and the year of issue; b) the name of the applicant; c) the name, the type of the product tested, the declaration or the chemical analysis of the active ingredients; d) the solvent or diluent used; SIST EN 252:2015

EN 252:2014 (E) 13 e) the wood species used and the mean density of the wood selected; f) any additional wood species used including the stake dimensions, the approximate number of annual rings per 10 mm and mean density of the wood selected; g) the number of replicates; h) the concentrations tested; i) the date of treatment and the treatment conditions: — initial vacuum:

. . . kPa/ . . . min — pressure:
. . . kPa/ . . . min — final vacuum:

. . . kPa/ . . . min j) the average amount of solution in litres per cubic meter absorbed in each series and the minimal and maximal values; k) the average retention of preservative in kilograms per cubic metre for each series and the minimum and maximum values; l) the reference preservative (composition, concentration, average retention and minimum and maximum values); m) the method of post treatment conditioning and the dates; n) the date of installation in the field; o) a brief description of the test field including its location; p) the date(s) of inspection of the stakes; q) the duration of the exposure period; r) the grading system used in the evaluation (Clause 11) and the degree of deterioration; s) notional average ratings for controls, reference stakes and test stakes; t) the name of the organization responsible for the report and the date of issue; u) the name and signature of the officer(s) in charge; v) the following note: “The interpretation and practical conclusions that can be drawn from a test report demand a specialized knowledge of the subject of wood preservation and, for this reason this test report by itself cannot constitute an approval certificate.” The test report shall also Iist any variation from the described test method as well as any factors that may have influenced the results. It is recommended to provide in an annex: — the density of each stake; — the wood preservative retention in each stake; SIST EN 252:2015

EN 252:2014 (E) 14 — the rating of each stake for each evaluation; — the biological agents responsible for decay for each st

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