EN 13183-3-2005 en Moisture content of a piece of sawn timber - Part 3 Estimation by capacitance method《锯材水份测量 第3部分 电容估算法》.pdf

1、BRITISH STANDARD BS EN 13183-3:2005 Moisture content of a piece of sawn timber Part 3: Estimation by capacitance method The European Standard EN 13183-3:2005 has the status of a British Standard ICS 79.040 BS EN 13183-3:2005 This British Standard was published under the authority of the Standards Po

2、licy and Strategy Committee on 31 March 2005 BSI 31 March 2005 ISBN 0 580 45799 0 National foreword This British Standard is the official English language version of EN 13183-3:2005. The UK participation in its preparation was entrusted to Technical Committee B/543, Round and sawn timber, which has

3、the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Catalogue under the section ent

4、itled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Complian

5、ce with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related in

6、ternational and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 10, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document

7、 was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEANSTANDARD NORMEEUROPENNE EUROPISCHENORM EN131833 March2005 ICS79.040 Englishversion MoisturecontentofapieceofsawntimberPart3:Estimation bycapacitancemethod TeneurenhumiditdunepicedeboissciPartie3: Estimationparmthodec

8、apacitive FeuchtegehalteinesStckesSchnittholzTeil3: SchtzungdurchkapazitivesMessverfahren ThisEuropeanStandardwasapprovedbyCENon3February2005. CENmembersareboundtocomplywiththeCEN/CENELECInternalRegulationswhichstipulatetheconditionsforgivingthisEurope an Standardthestatusofanationalstandardwithouta

9、nyalteration.Uptodatelistsandbibliographicalreferencesconcernings uchnational standardsmaybeobtainedonapplicationtotheCentralSecretariatortoanyCENmember. ThisEuropeanStandardexistsinthreeofficialversions(English,French,German).Aversioninanyotherlanguagemadebytra nslation undertheresponsibilityofaCEN

10、memberintoitsownlanguageandnotifiedtotheCentralSecretariathasthesamestatusast heofficial versions. CENmembersarethenationalstandardsbodiesofAustria,Belgium,Cyprus,CzechRepublic,Denmark,Estonia,Finland,France, Germany,Greece,Hungary,Iceland,Ireland,Italy,Latvia,Lithuania,Luxembourg,Malta,Netherlands,

11、Norway,Poland,Portugal, Slovakia, Slovenia,Spain,Sweden,SwitzerlandandUnitedKingdom. EUROPEANCOMMITTEEFORSTANDARDIZATION COMITEUROPENDENORMALISATION EUROPISCHESKOMITEEFRNORMUNG ManagementCentre:ruedeStassart,36B1050Brussels 2005CEN Allrightsofexploitationinanyformandbyanymeansreserved worldwideforCE

12、NnationalMembers. Ref.No.EN131833:2005:EEN 13183-3:2005 (E) 2 Contents Page Foreword3 1 Scope 4 2 Normative references 4 3 Terms and definitions .4 4 Moisture content estimation with hand-held capacitance moisture meters .4 4.1 Limits of application4 4.2 Apparatus .5 4.3 Initial type testing 5 4.4 P

13、rocedure .5 4.5 Expression of results 5 5 Moisture content estimation with in-line capacitance moisture meters5 5.1 Limits of application5 5.2 Apparatus and measuring set-up.6 5.3 Initial type testing 6 5.4 Calibration 6 5.5 Procedure .6 5.6 Expression of results 6 Annex A (normative) Procedure for

14、assessing the accuracy of capacitance moisture meters7 Annex B (informative) Moisture content of a lot 9 Bibliography 10 EN 13183-3:2005 (E) 3 Foreword This document (EN 13183-3:2005) has been prepared by Technical Committee CEN/TC 175 “Round and sawn timber”, the secretariat of which is held by AFN

15、OR. 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 September 2005, and conflicting national standards shall be withdrawn at the latest by September 2005. This document is one of a series, dealing

16、 with methods of measurement for round timber and sawn timber. Other standards in this series are: EN 13183-1, Moisture content of a piece of sawn timber - Part 1: Determination by oven dry method EN 13183-2, Moisture content of a piece of sawn timber - Part 2: Estimation by electrical resistance me

17、thod EN 1309-1, Round and sawn timber - Method of measurement of dimensions - Part 1: Sawn timber EN 1310, Round and sawn timber - Method of measurement of features EN 1311, Round and sawn timber - Method of measurement of biological degrade This document includes a Bibliography. According to the CE

18、N/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg

19、, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EN 13183-3:2005 (E) 4 1 Scope This document specifies a non destructive method for estimating the moisture content of a piece of sawn timber. The standard describes the conditions which

20、 shall be met by a capacitance measuring system to derive a moisture content estimate for individual pieces of timber. The standard applies to sawn timber and timber which has been planed or surfaced by other means. 2 Normative references The following referenced documents are indispensable for the

21、application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 844-1:1995, Round and sawn timber - Terminology - Part 1: General terms common to round timber and sawn tim

22、ber EN 844-3:1995, Round and sawn timber - Terminology - Part 3: General terms relating to sawn timber EN 844-4:1997, Round and sawn timber Terminology - Part 4: Terms relating to moisture content EN 844-6:1997, Round and sawn timber - Terminology - Part 6: Terms relating to dimensions of sawn timbe

23、r EN 844-7:1997, Round and sawn timber - Terminology - Part 7: Terms relating to anatomical structure of timber EN 844-9:1997, Round and sawn timber - Terminology - Part 9: Terms relating to features of sawn timber EN 844-12:2000, Round and sawn timber - Terminology - Part 12: Additional terms and g

24、eneral index EN 13183-1, Moisture content of a piece of sawn timber - Part 1: Determination by oven dry method EN ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories (ISO/IEC 17025:1999) 3 Terms and definitions For the purposes of this document, the terms a

25、nd definitions given in EN 844-1:1995, EN 844-3:1995, EN 844-4:1997, EN 844-6:1997, EN 844-7:1997, EN 844-9:1997 and EN 844-12:2000 apply. 4 Moisture content estimation with hand-held capacitance moisture meters 4.1 Limits of application This method is suitable for estimating the average moisture co

26、ntent of a piece of timber having a moisture content between approximately 7 % and 30 %. NOTE Any type of bipolar preservative, flame retardant, chemical or surface treatment may affect the accuracy of the measurement and requires special calibration of the instrument for each type of treatment. The

27、 estimated moisture content can be strongly affected by the type and reach of the moisture sensing system, the moisture content distribution and the wood density under the sensor, the operating modus, the dimensions of the piece of timber to be measured and the operator skills. EN 13183-3:2005 (E) 5

28、 Any air gap between the timber surface and the sensing unit will strongly influence the reading. Very rough sawn or uneven surfaces can only be measured if the shape of the condensator plate or probe secures good contact. 4.2 Apparatus Hand-held capacitance moisture meter equipped with a flat shape

29、d condensator plate surface, surface spring electrodes or special non-invasive measuring probes, graduated up to at least 30 % in units of maximum 1 % moisture content. NOTE Normally capacitance moisture meters are equipped with a setting for correction for density and are applicable or adjustable f

30、or different thicknesses. Density correction may also be carried out by using special tables or formulas provided by the suppliers of the instrument. 4.3 Initial type testing The accuracy of the measuring system and its operating instructions shall be tested in accordance with Annex A of this docume

31、nt by a laboratory compliant with EN ISO/IEC 17025. The results of these tests shall be made available with the apparatus. 4.4 Procedure Before taking measurements the capacitance moisture meter shall be checked according to the instructions provided by the supplier of the instrument. Set the moistu

32、re measuring unit to its basic settings with the assistance of a check block. The capacitance moisture meter shall be adjusted for density. If the actual density of the timber to be measured is unknown, an average density for the species to be measured may be selected from the operating manual provi

33、ded by the supplier of the instrument. Ensure that the instrument being used is adjusted or applicable for the thickness of the timber being measured. Air gaps or bad contact between the condensator plates and the wood surface shall be avoided. The measurement area shall be free from features affect

34、ing the measurement such as bark, knots, resin pockets, wetted surface or checks. The measurement shall be taken at a point 300 mm from one of the ends of the piece. If this position contains any of the defects detailed above the measurement shall be taken on the nearest defect free point towards th

35、e centre of the piece. For pieces less than 600 mm long, measure at mid-length. 4.5 Expression of results The estimation results shall be expressed at least to the nearest one percentage point. 5 Moisture content estimation with in-line capacitance moisture meters 5.1 Limits of application This meth

36、od is suitable for estimating the average moisture content of a piece of timber having a moisture content between approximately 7 % and 30 %. NOTE Any type of bipolar preservative, flame retardant, chemical or surface treatment may affect the accuracy of the measurement and requires special calibrat

37、ion of the instrument for each type of treatment. EN 13183-3:2005 (E) 6 The estimated moisture content can be strongly affected by the type and reach of the moisture sensing system, the moisture content distribution and the wood density in the sensor reach, the operating modus, the geometry of the m

38、easuring set up and variations in the dimensions of the piece of timber to be measured. The air gap between the timber surface and the sensing unit will strongly influence the reading. To reduce this influence, caused by twisted and bowed boards, vibration or unstable transport conditions, a press d

39、evice securing a constant distance to the sensor(s) is recommended. 5.2 Apparatus and measuring set-up A moisture measuring unit consisting of a fixed framework carrying one or several sensing units, through which the timber is passed lengthwise or transversal to the direction of travel, connected t

40、o an evaluation unit. The sensing unit(s) shall be installed at a position in the production line that is easy to access, to keep clean and free of vibrations. The sensing unit(s) and the corresponding cabling shall be shielded to avoid electromagnetic interference. The measuring area shall be kept

41、free of dust or dirt by means of an appropriate system (e.g. pressurised air nozzles). The read-out from the equipment shall be graduated up to at least 30 % in units of maximum 1 % moisture content. 5.3 Initial type testing The accuracy of the measuring system and its operating instructions shall b

42、e tested in accordance with Annex A of this document by a laboratory compliant with EN ISO/IEC 17025. The results of these tests shall be made available with the apparatus. 5.4 Calibration Before an in-line measuring system can be used the system shall be calibrated according to the instructions of

43、the supplier. NOTE 1 Calibration involves the collection of in-line moisture content readings from a number of individual boards with the same dimension and approximately the same moisture gradient. For each of the instrument reading positions on these boards the moisture content is determined by th

44、e oven-dry method according to EN 13183-1. Features such as bark, knots etc should be avoided. This data forms the basis for a linear regression, the coefficients of which are stored by the system forming a measuring programme for the individual dimension and species being measured. NOTE 2 The accur

45、acy of capacitance moisture meters is affected by local density variations. If these density variations within the timber to be measured result in an unacceptable accuracy, a density measuring unit can be connected to the moisture measuring unit. This density measuring unit should be calibrated sepa

46、rately according to the instructions of the supplier. 5.5 Procedure Set the moisture measuring unit to its basic settings with the help of a check block. Select an appropriate measuring programme before changing to the measurement mode. 5.6 Expression of results The estimation results shall be expre

47、ssed at least to the nearest one percentage point. NOTE The indicated moisture content of each board passing through the system is normally the result of various individual measurements which have undergone a filtering and averaging algorithm. EN 13183-3:2005 (E) 7 Annex A (normative) Procedure for

48、assessing the accuracy of capacitance moisture meters A.1 Introduction This procedure shall be followed by laboratories when testing the accuracy of capacitance meter estimations of moisture content in comparison with an oven dry measurement of moisture content taken at the same position on a piece of timber. A.2 Test material The test shall be conducted on three individual named species samples representing pines, spruces and hardwood. The samples shall have a sawn surface finish. Each sample shall contain a minimum of 50 pieces of 50 mm nominal thickness and equal wi