1、BRITISH STANDARD Wood based panels Determination of dimensional changes associated with changes in relative humi di ty The European Standard EN 3 18:2002 has the status of a British Standard ICs 79.060.01 BS EN 3 18:2002 Wk present to the responsible European committee any enquiries on the interpret
2、ation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. - A list of organizations represented on this committee can be obtained on request to its secretary. Cr oss-r e fer enc e s The British Standards
3、 which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard do
4、es not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an ins
5、ide front cover, the EN title page, pages 2 to 8, an inside back cover and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. O BSI 11 April 2002 ISBN O 580 39492 I EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 318 March 2002 ICs 79.06
6、0.01 Supersedes EN 31 8:1993 English version Wood based panels - Determination of dimensional changes associated with changes in relative humidity Panneaux base de bois - Dtermination des variations dimensionnelles sous linfluence de variations de lhumidit relative Holzwerkstoffe -,Bestimmung von Ma
7、nderungen in Verbindung mit Anderungen der relativen Luftfeuchte This European Standard was approved by CEN on 24 February 2002. CEN members are bound to comply with the CENKENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard
8、 without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other languag
9、e made by translation under the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Icela
10、nd, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION EUROPISCHES KOMITEE FR NORMUNG COMIT EUROPEN DE NORMALISATION Management Centre: rue de Stassart, 36 B-1050 Brussels O 2002 CEN All rights of ex
11、ploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 318:2002 E EN 318:2002 (E) Contents page Foreword 3 1 2 3 4 4.1 4.2 4.3 4.4 4.5 4.6 4.7 5 6 6.1 6.1 . 1 6.1.2 6.1.3 6.2 6.3 6.4 7 7.1 7.2 7.3 7.4 8 Scope 4 Normative references 4 Principle 4 Balance . 4
12、Measuring instruments for length and thickness . 4 Calibration bar 4 Climate chamber 4 Drying cabinet 5 Hygrometer . 5 Thermometer 5 Test pieces 5 Procedure . 5 Test piece preparation . 5 General 5 Thickness measuring points 5 Length measuring points 5 Conditioning . 6 Measurements 6 Drying 7 Expres
13、sion of results 7 Moisture content 7 Change in length 7 Change in thickness 7 Panel results . 8 Apparat us . 4 Test report 8 2 EN 318:2002 (E) Foreword This document (EN 318:2002) has been prepared by Technical Committee CEN/TC 112 “Wood-based panels“, the secretariat of which is held by DIN. This E
14、uropean Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by September 2002, and conflicting national standards shall be withdrawn at the lat- est by September 2002. This document supersedes EN 31 8:1993. Compared t
15、o the version EN 318:1993 the following modifications have been made: a) The scope has been extended from fibre boards to wood-based panels b) The conditioning procedure has been modified According to the CENKENELEC Internal Regulations, the national standards organizations of the following coun- tr
16、ies are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Swe- den, Switzerland and the United Kingdom. 3 EN 318:2002 (E) 1 Scope This European Stan
17、dard specifies a method for the determination of dimensional changes in wood-based panels, due to changes in the relative humidity of the air. 2 Normative references This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are
18、cited at the appropriate places in the text, and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest ed
19、ition of the publication referred to applies (including amendments). EN 322, Wood-based panels - Determination of moisture content. EN 326-1, Wood-based panels - Sampling, cutting and inspection - Part I: Sampling and cutting of test pieces and expression of test results. 3 Principle Because variati
20、ons in relative humidity affect the moisture content of a panel and result in changes to its dimen- sions, test pieces are measured after conditioning to different levels of relative humidity. The equilibrium moisture content of panel products is dependent on the history of moisture change. Higher e
21、quilibrium moisture contents for any one relative humidity are achieved in desorption compared with adsorption; this gives rise to a hysteresis effect. In order to obtain the true dimensional change, this is measured between 65 % relative humidity and 85 % relative humidity in adsorption and 65 % re
22、lative humidity and 30 % relative humidity in desorption. 4 Apparatus 4.1 Balance Balance as described in EN 322. 4.2 Measuring instruments for length and thickness Instruments for measuring length and thickness with an accuracy of f 0,Ol mm. An example of a length measuring equipment is shown in Fi
23、gure 1. 4.3 Calibration bar Corrosion resistant metal bar of sufficient length and shape to calibrate the length measuring equipment. The length of the calibration bar shall be known to within 0,Ol mm. 4.4 Climate chamber Climate chamber(s) capable of maintaining the required temperature to f 1 “C a
24、nd relative humidity to f 3 %. 4 EN 318:2002 (E) 300 I I Figure 1 - Example of length measuring equipment 4.5 Drying cabinet Ventilated drying oven, capable of being controlled at (103 f 2) OC. 4.6 Hygrometer Hygrometer with an accuracy of f 1 % relative humidity to measure and record the relative a
25、ir humidity in the climate cham ber. 4.7 Thermometer Thermometer with an accuracy off 0,5 OC to measure and record temperature in the climate chamber 5 Test pieces The normal dimensions of test pieces are (300 f 2) mm x (50 f 2) mm x t (panel thickness) but longer test pieces may be used. From each
26、panel, two sets of four test pieces shall be cut in each panel direction to give 16 test pieces per panel in total. The general conditions for sampling of the test pieces shall be in accordance with EN 326-1. 6 Procedure 6.1 Test piece preparation 6.1 .I General The test pieces shall be prepared wit
27、h suitable markings to ensure that the measurement will be carried out at the same position each time. 6.1.2 Thickness measuring points The marks are placed on the centre line of the test piece 50 mm from the ends and at the mid point, as shown in Fig- ure 2. Ink marks on the surface of the test pie
28、ce are considered to be adequate. Other types of markings may be used if proven to give correct results. 6.1.3 Length measuring points A suitable reference system comprises glass plates with a thickness of at least 1 mm glued to the ends of the test piece. An alternative reference system is metal kn
29、obs, placed at a distance of 250 mm apart, approximately 25 mm from each end. The knobs can be mechanically fastened or glued onto the surface of the test piece. The adhesive shall not be water-based or hygroscopic. Other types of reference systems may be used if proven to give correct re- sults. 5
30、EN 318:2002 (E) L I 1 B Dimensions in millimetres 50 100 100 - - - - I- l 1 Step (No.) 1 2 3 1 2 Set No. 1 20 OC, 30 % relative humidity 20 OC, 65 % relative humidity 20 OC, 85 % relative humidity Set No. 2 20 OC, 85 % relative humidity 20 OC, 65 % relative humidity 20 OC, 30 % relative humidity 300
31、 1 Ink mark 2 Glass plate Figure 2 - Example of a suitable 300 mm long test piece with glass plates 6.2 Conditioning The two sets of test pieces will be treated separately and each conditioned in three steps. Condition the test pieces to constant mass in each of the steps given in Table 1. Measure l
32、ength, thickness and mass according to 6.3 after steps 2 and 3. Constant mass is considered to be reached when the results of two successive weighing operations, carried out at an interval of 24 h, do not differ by more than 0,l % of the mass of the test piece. The climate shall be measured and reco
33、rded at an interval of not less than once an hour during the conditioning of the test pieces . 6.3 Measurements After steps 2 and 3 of the conditioning periods the following parameters shall be measured on the test pieces: - the distance between the length markings. Before measuring the length, the
34、equipment shall be calibrated by using the calibration bar described in 4.3. Warped or bent test pieces shall be straightened during the meas- urement; - the thickness of the test pieces. The measurements shall be carried out at three points, see Figure 2; - the mass of the test pieces. 6 EN 318:200
35、2 (E) All the measurements have to be performed in the conditioning atmosphere or within 5 minutes after the test pieces have been taken out from the climate chamber. 6.4 Drying After the test, the test pieces shall be dried according to EN 322 and then be weighed. 7 Expression of results 7.1 Moistu
36、re content For each test piece calculate the moisture content for the three climates in steps 2 and 3 in accordance with EN 322 by using the results from 6.3 and 6.4. When necessary, the recorded masses shall be corrected to take account of the mass of the markings used. NOTE give misleading results
37、. For cement bonded particle boards determination of moisture content according to EN 322 is not relevant and could 7.2 Change in length For each test piece the relative change in length is calculated according to equations (1) and (2), and rounded off to the nearest 0,l mm/m. s165,85 = 85 - 65 . I
38、000 (using set I results) l65 8165.30 = 30 - 65 . I 000 (using set 2 results) (2) l65 is the length between measurement points at 20 OC, 85 % relative humidity, corrected when necessary for the effect of the markings used, in millimetres; is the length between measurement points at 20 OC, 65 % relat
39、ive humidity, corrected when necessary for the effect of the markings used, in millimetres; is the length between measurement points at 20 OC, 30 % relative humidity, corrected when necessary for markings used, in millimetres; is the relative change of length for a change of the relative humidity fr
40、om 65 % to 85 %, in millimetres per metre; is the relative change of length for a change of the relative humidity from 65 % to 30 %, in millimetres per metre. 7.3 Change in thickness For each test piece calculate the change in thickness for each of the three points according to equations (3) and (4)
41、. The final result for the test piece is the mean value for all three measured points rounded off to the nearest 0,l %. St65, 85 = t85 - . I 00 (using set I results) t65 (3) Jt65,30 = t30 - t65 . I 00 (using set 2 results) t65 (4) 7 EN 318:2002 (E) where t85 t65 t30 8 t65, 85 8 t65. 30 is the thickn
42、ess at 20 OC, 85 % relative humidity, corrected when necessary for the effect of the markings used, in millimetres; is the thickness at 20 OC, 65 % relative humidity, corrected when necessary for the effect of the markings used, in millimetres; is the thickness at 20 OC, 30 % relative humidity, corr
43、ected when necessary for the effect of the markings used, in millimetres; is the relative change of the thickness for a change of the relative humidity from 65 % to 85 %,in percent; is the relative change of the thickness for a change of the relative humidity from 65 % to 30 %, in percent. 7.4 Panel
44、 results For each panel and panel direction, calculate the mean value and the range for moisture content and changes of length and thickness. 8 Testreport According to EN 326-1. 8 BS EN 3 18:2002 BSI 389 Chiswick High Road Lon don w4 4AL BSI is the independent national body responsible for preparing
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