Wood-based panels - Sampling, cutting and inspection - Part 2: Initial type testing and factory production control

This European Standard specifies methods for internal initial type testing (ITT) and internal factory production control (FPC) as well as external control of wood-based panels for their compliance with EN 13986 and other relevant product specifications. However, it may also apply, at the option of the manufacturer, to wood-based panels applied for non-construction purposes.
This European Standard is not applicable for the assessment of compliance with specifications of panels comprised in consignments. In such cases, EN 326-3 applies.
For internal factory production control, if required, methods for the assessment of conformity of batches and of production over longer periods are given.
For external control, if required, methods for the initial inspection of a factory and initial type testing of a product, and for the surveillance of the factory production control, are given.
In the factory production control small test pieces are used. The statistics of evaluation is based on normal distribution.

Holzwerkstoffe - Probenahme, Zuschnitt und Überwachung - Teil 2: Erstprüfung des Produktes und werkseigene Produktionskontrolle

Diese Europäische Norm legt Verfahren für die Erstprüfung des Produktes und die werkseigene Produk-tionskontrolle sowie für die Fremdüberwachung der Übereinstimmung von Holzwerkstoffen mit EN 13986 und anderen relevanten Produktnormen fest. Sie ist jedoch auch anwendbar für Holzwerkstoffe, die nicht zur Verwendung im Bauwesen vorgesehen sind, wenn der Hersteller dies vorsieht.
Diese Europäische Norm gilt nicht für die Bewertung der Übereinstimmung mit den Anforderungen bei Platten¬lieferungen. In solchen Fällen gilt EN 326-3.
Für die werkseigene Produktionskontrolle, falls erforderlich, werden Verfahren zur Bewertung der Über-einstimmung bei Chargen und bei der Fertigung über längere Zeiten angegeben.
Für die Fremdüberwachung, falls erforderlich, werden Verfahren zur Erstinspektion eines Werkes und einer Erstprü¬fung des Produktes sowie zur Überwachung der werkseigenen Produktionskontrolle angegeben.
Für die werkseigene Produktionskontrolle werden kleine Prüfköper verwendet. Die statistischen Nachweis-verfahren basieren auf einer Normalverteilung.

Panneaux à base de bois - Echantillonnage, découpe et contrôle - Partie 2 : Essai de type initial et contrôle de la production en usine

La présente Norme Européenne prescrit les méthodes pour les essais internes de type initial (ITT) et pour le contrôle de production interne en usine (CPU) ainsi que le contrôle externe des panneaux à base de bois vis-à-vis des exigences de la norme EN 13986 et des normes d’exigences produits pertinentes concernées. Cependant, la présente norme peut aussi s’appliquer, selon le choix du fabricant, aux panneaux à base de bois qui ne sont pas destinés à la construction.
La présente Norme Européenne ne s’applique pas à l’évaluation de la conformité au regard des  spécifications des caractéristiques des panneaux faisant partie de livraisons. Dans ce cas, l’EN 326-3 s’applique.
Pour le contrôle interne de la production en usine, si nécessaire, les méthodes d’évaluation de la conformité des lots et de la production sur de longues périodes sont indiquées.
Pour le contrôle externe, si nécessaire, les méthodes de l’inspection initiale de l’usine et d’essai de type initial d’un produit, ainsi que les méthodes relatives à la surveillance du contrôle de la production en usine sont indiquées.
Pour le contrôle de production en usine, on utilise des petites éprouvettes. Les statistiques d’évaluation sont basées sur une distribution normale.

Lesne plošče - Vzorčenje, razžagovanje in kontrola - 2. del: Začetno preskušanje tipa in kontrola proizvodnje v obratu

Standard EN 326-2+A1 določa metode za notranje začetno preskušanje tipa (ITT) in notranjo kontrolo proizvodnje v obratu (FPC) ter za zunanjo kontrolo lesnih plošč za preverjanje njihove skladnosti s standardom EN 13986 ter drugimi ustreznimi specifikacijami izdelka. Vendar na željo proizvajalca lahko velja tudi za lesne plošče, ki se uporabljajo za negradbene namene. Ta evropski standard se ne uporablja za oceno skladnosti s specifikacijami plošč, zbranih v pošiljkah. V takih primerih se uporablja standard EN 326-3. Po potrebi so za notranjo kontrolo proizvodnje v obratu podane metode za oceno skladnosti serij in proizvodnje v daljšem obdobju. Po potrebi so za zunanjo kontrolo podane metode za začetno kontrolo obrata in začetno preskušanje tipa izdelka ter za nadzor kontrole proizvodnje v obratu. Pri kontroli proizvodnje v obratu se uporabljajo majhni preskusni delčki. Statistika vrednotenja temelji na normalni distribuciji.

General Information

Status
Published
Publication Date
05-Aug-2014
Current Stage
9092 - Decision on results of review/2YR ENQ - revise - Review Enquiry
Due Date
02-Dec-2020
Completion Date
28-May-2020

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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Holzwerkstoffe - Probenahme, Zuschnitt und Überwachung - Teil 2: Erstprüfung des Produktes und werkseigene ProduktionskontrollePanneaux à base de bois - Echantillonnage, découpe et contrôle - Partie 2 : Essai de type initial et contrôle de la production en usineWood-based panels - Sampling, cutting and inspection - Part 2: Initial type testing and factory production control79.060.01Wood-based panels in generalICS:Ta slovenski standard je istoveten z:EN 326-2:2010+A1:2014SIST EN 326-2:2011+A1:2014en,fr,de01-oktober-2014SIST EN 326-2:2011+A1:2014SLOVENSKI

STANDARD
SIST EN 326-2:2011+A1:2014
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 326-2:2010+A1
August 2014 ICS 79.060.01 Supersedes EN 326-2:2010English Version

Wood-based panels - Sampling, cutting and inspection - Part 2: Initial type testing and factory production control

Panneaux à base de bois - Echantillonnage, découpe et contrôle - Partie 2 : Essai de type initial et contrôle de la production en usine

Holzwerkstoffe - Probenahme, Zuschnitt und Überwachung - Teil 2: Erstprüfung des Produktes und werkseigene Produktionskontrolle This European Standard was approved by CEN on 7 August 2010 and includes Amendment 1 approved by CEN on 17 July 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 326-2:2010+A1:2014 ESIST EN 326-2:2011+A1:2014

EN 326-2:2010+A1:2014 (E) 2 Contents Page Foreword ..............................................................................................................................................................4 1 Scope ......................................................................................................................................................5 2 Normative references ............................................................................................................................5 3 Terms and definitions ...........................................................................................................................5 4 Symbols and indices .............................................................................................................................7 4.1 Letter symbols (see also EN 326-1:1994) ............................................................................................7 4.2 Indices (see also EN 326-1:1994) .........................................................................................................8 5 Initial type testing (ITT) .........................................................................................................................9 5.1 General ....................................................................................................................................................9 5.2 Initial type testing by variables ............................................................................................................9 5.2.1 General ....................................................................................................................................................9 5.2.2 Sampling of panels ................................................................................................................................9 5.2.3 Evaluation ............................................................................................................................................ 10 5.3 Initial type testing by attributes ......................................................................................................... 11 5.3.1 Sampling .............................................................................................................................................. 11 5.3.2 Evaluation ............................................................................................................................................ 12 6 Factory production control ................................................................................................................ 12 6.1 General ................................................................................................................................................. 12 6.2 Sampling .............................................................................................................................................. 13 6.2.1 General ................................................................................................................................................. 13 6.2.2 Dimensional tolerances, squareness and edge straightness ........................................................ 13 6.2.3 Other properties assessed as attributes and not included in 6.2.1 or 6.2.2 ................................. 13 6.2.4 Sampling and cutting of test pieces ................................................................................................. 13 6.3 Factory production control by variables .......................................................................................... 13 6.3.1 Characteristics .................................................................................................................................... 13 6.3.2 Product types ...................................................................................................................................... 14 6.4 Control of production ......................................................................................................................... 14 6.4.1 General ................................................................................................................................................. 14 6.4.2 Factory production control by variables for batch production ..................................................... 15 6.4.3 Factory production control by attributes for batch production ..................................................... 17 6.4.4 Internal records of an established product ...................................................................................... 18 6.5 Initial inspection of factory and factory production control (FPC) ................................................ 19 6.6 Continuous surveillance, assessment and approval of the factory production control ............. 20 Annex A (informative)

Example of initial type testing by variables – Evaluation of bending strength of particleboards (see 5.2) .................................................................................................. 21 A.1 Example ............................................................................................................................................... 21 A.2 Sampling (see 5.1.2) ........................................................................................................................... 21 A.3 Test results, records and evaluation (see 5.2.3 and EN 326-1:1994, Clause 7) ............................ 22 Annex B (informative)

Factory production control by variables – Example: Batch production (see 6.4.2) ..................................................................................................................................................... 23 B.1 General ................................................................................................................................................. 23 B.2 Sampling .............................................................................................................................................. 23 B.3 Testing ................................................................................................................................................. 23 B.4 Calculation and recording of test results of the first sample ........................................................ 23 B.4.1 Example for the case that the first sample of one panel fulfils the panel characteristic requirement ......................................................................................................................................... 23 SIST EN 326-2:2011+A1:2014

EN 326-2:2010+A1:2014 (E) 3 B.4.2 Example for the case that the first sample of one panel does not fulfil the panel characteristic requirement ................................................................................................................. 24 Annex C (informative)

Example of initial type testing attributes - Evaluation of bonding quality of plywood (see 6.4.3.1) ........................................................................................................................... 27 C.1 Example ................................................................................................................................................ 27 C.2 Sampling plan ...................................................................................................................................... 27 C.3 Sampling (see 5.3.1) ............................................................................................................................ 27 C.4 Test data and evaluation of bond shear strength and apparent cohesive wood fibre failure percentage ........................................................................................................................................... 27 C.4.1 General ................................................................................................................................................. 27 C.4.2 First sample ......................................................................................................................................... 27 C.4.3 Second sample .................................................................................................................................... 29 C.5 Single sampling plan ........................................................................................................................... 29 Annex D (informative)

Control of factory production control records - Examples of the determination of differences between factory testing and external testing (see 6.6) .................. 30 D.1 General ................................................................................................................................................. 30 D.1.1 Use of unconditioned test pieces ...................................................................................................... 30 D.1.2 Paired testing ....................................................................................................................................... 30 D.2 Example (1): Swelling in thickness tested according to EN 317 .................................................... 31 D.2.1 Sample of example (1) ......................................................................................................................... 31 D.2.2 Control of variability ............................................................................................................................ 31 D.3 Example (2): Internal bond tested according to EN 319 .................................................................. 33 D.3.1 General ................................................................................................................................................. 33 D.3.2 Sample of Example (2) ........................................................................................................................ 33 D.3.3 Control of variability ............................................................................................................................ 33 D.4 Determination of a significant difference between the results from the alternative test procedure and from the standard reference test method ............................................................... 34 Annex E (informative)

Example of the calculation of a linear correlation (see 6.6) ................................... 36 Annex F (informative)

Example of the determination of a significant difference between the results from the alternative test procedure and from the standard reference test method (see 6.6) in accordance with EN 13986 .............................................................................................. 40 F.1 General ................................................................................................................................................. 40 F.2 Control of variability (see Annex D) .................................................................................................. 41 F.3 Determination of a significant difference (see Annex D) ................................................................ 42 Bibliography ...................................................................................................................................................... 43

SIST EN 326-2:2011+A1:2014

EN 326-2:2010+A1:2014 (E) 4 Foreword This document (EN 326-2:2010+A1:2014) has been prepared by Technical Committee CEN/TC 112 “Wood-based panels”, the secretariat of which is held by DIN. 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 February 2015, and conflicting national standards shall be withdrawn at the latest by February 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 includes Amendment 1 approved by CEN on 17 July 2014. This document supersedes !EN 326-2:2010". The start and finish of text introduced or altered by amendment is indicated in the text by tags !". !This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association." A revision of EN 326-2:2000 was necessary in order to adapt this standard to the harmonized European Standard EN 13986:2004. Compared to EN 326-2:2000 the following main changes have been made: a) the procedures of initial type testing as well as of factory production control have been adapted to those specified in EN 13986; b) the terminology has been adapted to EN 13986; c) the specification requirement of the lower 5 % value or the upper 95 % value, respectively, is also fulfilled, if all single 30 mean values comply with the specification limit; d) the procedure of evaluation of linear correlations between test results has been improved. This standard is one of a series of European Standards dealing with sampling, cutting and inspection of wood-based panels. The other parts of this series are listed in Clause 2 and in the Bibliography. 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 326-2:2011+A1:2014

EN 326-2:2010+A1:2014 (E) 5 1 Scope This European Standard specifies methods for internal initial type testing (ITT) and internal factory production control (FPC) as well as external control of wood-based panels for their compliance with EN 13986 and other relevant product specifications. However, it may also apply, at the option of the manufacturer, to wood-based panels applied for non-construction purposes. This European Standard is not applicable for the assessment of compliance with specifications of panels comprised in consignments. In such cases, EN 326-3 applies. For internal factory production control, if required, methods for the assessment of conformity of batches and of production over longer periods are given. For external control, if required, methods for the initial inspection of a factory and initial type testing of a product, and for the surveillance of the factory production control, are given. In the factory production control small test pieces are used. The statistics of evaluation is based on normal distribution. 2 Normative references !The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies." EN 326-1:1994, Wood-based panels — Sampling, cutting and inspection — Part 1: Sampling and cutting of test pieces and expression of test results EN 13986, Wood-based panels for use in construction — Characteristics, evaluation of conformity and marking ISO 8258, Shewhart control charts 3 Terms and definitions For the purpose of this document, the terms and definitions given in EN 326-1:1994 and the following apply. 3.1 acceptable quality level AQL maximum percentage of non-conforming panels that for the purpose of sampling inspection can be considered satisfactory as a process average 3.2 at random sampling of panels in such a way that each panel of the inspection lot has an equal chance of being selected, and cutting of test pieces from a single panel in such a way that each part of the panel has an equal chance of being selected as a test piece 3.3 attribute qualitative panel characteristic which can be taken for a yes or no decision about the conformity of a panel characteristic with the specification requirements SIST EN 326-2:2011+A1:2014

EN 326-2:2010+A1:2014 (E) 6 NOTE An example is given in Annex C. 3.4 batch panels of the same product type produced in a shift 3.5 defective panel which does not meet the required specification limit of the relevant characteristic 3.6 inspection body body which is responsible for external control 3.7 inspection by attributes inspection whereby either the unit of product is classified simply as conforming or non-conforming, or the number of nonconformities in the unit of product is counted, with respect to a given requirement or set of requirements 3.8 inspection by variables inspection whereby the conformity of a panel characteristic can be measured on a continuous scale 3.9 inspection lot (for factory control) portion of production which is presented for sampling and inspection, consisting of panels of the same type, normally within the same thickness range, coming from the same production line and manufactured under essentially the same conditions 3.10 inspection lot size N number of panels in one inspection lot 3.11 lower specification limit L value required by the EN specification that 95 % of the panels should have values greater than or equal to 3.12 panel piece of wood-based sheet material large enough to permit the cutting of test pieces 3.13 percent defective extent of non-conformity of a panel product expressed by percentage defective panels in the total number of panels inspected 3.14 production site single production line 3.15 product type panel type, irrespective of thickness, as defined in the relevant EN specification SIST EN 326-2:2011+A1:2014

EN 326-2:2010+A1:2014 (E) 7 3.16 reference population wood-based panels for which the relationship between test values is relevant 3.17 quality characteristic characteristic that is essential for the evaluation of a product or product type in accordance with a relevant EN specification 3.18 sample collection of panels which are drawn from an inspection lot NOTE Unless otherwise agreed, the panels of the sample are drawn at random. 3.19 test piece piece of panel cut to the size required for testing a specific characteristic 3.20 test value xij single value or measurement of a specific characteristic obtained from a test piece 3.21 thickness range panels with a thickness for which the same specification limits are valid according to the relevant EN specification 3.22 upper specification limit U value required by the EN specification that 95 % of the panels should have values lower than or equal to 3.23 variable test value or measurement which can be measured on a continuous scale 4 Symbols and indices 4.1 Letter symbols (see also EN 326-1:1994) Ac Acceptance number AQL Acceptable quality level a Linear correlation constant b Linear correlation factor cconv Conversion factor F Statistical factor L Lower specification limit m Number of test pieces cut from each single panel of the sample, in either test direction n Sample size (number of panels) SIST EN 326-2:2011+A1:2014

EN 326-2:2010+A1:2014 (E) 8 N Number of panels in one inspection lot, i.e. inspection lot size r Correlation coefficient; coefficient of linear regression Re Rejection number xs Estimate of the standard deviation of a characteristic between panel means jx xsδ Estimate of the standard deviation of the relative differences of the panel means j/x xs∆ Standard deviation between panel differences jws Estimate of the standard deviation of a characteristic within a panel j of the sample 2sjx,alt Variance of panel means of the alternative testing procedure 2jx,refs Variance of panel means of the reference standard test t Statistical factor, see Table 1 U Upper specification limit δ Relative difference ∆ Absolute difference jw,ν Coefficient of variation within a panel j of the sample xν Coefficient of variation between the panel means jx convφ Linear conversion function ijx Single test value or measurement jx Mean value of the m test values (or measurements) obtained from a single panel j nx Grand mean of n single panel mean values altjx, Test value of the population of the alternative test procedure j,refx Test value of the population of the reference standard test method jx∆ Test value of the difference between the alternative test procedure and the reference standard test method 4.2 Indices (see also EN 326-1:1994) alt Related to alternative testing procedure attr Related to inspection by attributes conv Related to conversion function cu Cumulative value d Related to double sample plan SIST EN 326-2:2011+A1:2014

EN 326-2:2010+A1:2014 (E) 9 ext Test results from the external control i Serial test piece number within a panel (i = 1, 2, ..., m) ITT Test results related to initial type testing j Test panel identification number within a sample (j = 1, 2, ..., n) m Related to number of test pieces of a panel n Related to the number of panels of a sample ref Related to reference standard test si Related to single sampling plan w Characteristic within a panel 5 Initial type testing (ITT) 5.1 General Initial type testing shall be performed according to this European Standard on first application of EN 13986, except where tests were previously performed in accordance with the provisions of these standards (i.e. same product, same characteristic(s), test method, sampling procedure, system of conformity, etc.). Initial type testing shall be performed at the beginning of the production of a new product type. 5.2 Initial type testing by variables 5.2.1 General In general, the requirements of the panel properties are fulfilled if at least 95 % of the panel means for each characteristic are above the lower L or below the upper U specification limit respectively. NOTE For examples, see Annex A. 5.2.2 Sampling of panels The initial type testing shall comprise panels from not less than three production shifts. The minimum number of panels in the initial type testing sample nITT of a factory production is 12 panels per product type with at least two panels from each production line. The minimum number of panels may be reduced to 6, if the product properties can be documented from internal records of at least 12 tested panels in the start up period. SIST EN 326-2:2011+A1:2014

EN 326-2:2010+A1:2014 (E) 10 5.2.3 Evaluation 5.2.3.1 Evaluation by using the test results directly 5.2.3.1.1 Compliance of the ITT sample Calculate the mean value jITTx, for each panel, the grand mean value ITTx for the panels and, the standard deviation between the panels ITTxs, for each relevant characteristic in accordance with Equations (1) and (2): ITTnjjjITTITTnxxITT∑===1, (1) and )1()(12,,−−=∑==ITTnjjITTjITTITTxnxxsITT (2) To fulfil the specification requirement the lower 5 % value or upper 95 % value shall be higher than or equal to the lower specification limit L or lower than or equal to the upper specification limit U respectively, when calculated according to the Equation (3) or (4), respectively: ITTxnITTstxLITT,%5⋅−= (3) or ITTxnITTstxUITT,%95⋅+= (4) where ITTnt shall be taken from Table 1. Table 1 — Single sided t – values for different sample sizes m and n Number of test pieces m or of panels n, respectively 4 5 6 8 10 12 16 18 30 tm or tn, respectively 2,35 2,13 2,02 1,89 1,83 1,80 1,75 1,74 1,70 NOTE The table values correspond to a 95 % confidence limit, single-sided case, in accordance with ISO 2602:1980.

5.2.3.1.2 Variability within panels of the ITT sample The mean standard deviation within panels of the ITT sample ITTws,, where "w" is indicating "within" panels, shall be derived from the standard deviation within each panel jws, of the sample [Equation (13)] according to Equation (5): SIST EN 326-2:2011+A1:2014

EN 326-2:2010+A1:2014 (E) 11 ITTnjjjITTwITTwnssITT∑===12,., (5) 5.2.3.2 Evaluation by using relative test results If the sample consists of panels which are covered by different lower L and/or upper U specification limits (for example by combining different thickness ranges of the same standard type of panel product), the evaluation shall be carried out on test results related to each specification limit as follows: Calculate for each individual panel the relative mean jxδ relevant to either the lower L or upper U specification limit according to Equation (6) or (7), respectively: LLxxjLj)(,−=δ (6) or UUxxjUj)(,−=δ (7) Calculate the grand mean of the relative differences of all panels of the inspection sample according to: nxxnj∑=1δδ (8) and the standard deviation xsδ of the relative differences between the panel means according to: 1)(21−−=∑nxxsjnxδδδ (9) To fulfil the specification requirement the lower 5 % value or the upper 95 % value, respectively, shall be equal to or greater than zero for characteristics with a lower specification limit L or equal to or less than zero for characteristics with an upper specification limit U when calculated according to Equation (10) or (11), respectively: xnstxLδδδ⋅−=%5, (10) or xnstxUδδδ⋅+=%95, (11) 5.3 Initial type testing by attributes 5.3.1 Sampling The initial type testing shall comprise panels from not less than three production shifts. SIST EN 326-2:2011+A1:2014

EN 326-2:2010+A1:2014 (E) 12 The minimum number of panels in the initial type testing sample shall be 20 (or 26 = 2 × 13 if a double sampling plan is used). NOTE 1 The sample sizes for the inspection by attributes correspond to a normal inspection of level I according to ISO 2859-1:1989 for a lot size (Nattr) of maximum 500 panels. NOTE 2 For examples see Annex C. 5.3.2 Evaluation 5.3.2.1 General Before sampling the manufacturer shall chose between a single (Option 1) or a double sampling plan (Option 2). 5.3.2.2 Single sampling plan (Option 1) If the number of defectives in the sample is greater than 2, the inspection lot shall be rejected. 5.3.2.3 Double sampling plan (Option 2) (see Table 4) A more reliable initial type testing can be carried out with a double sampling plan, where the second sample size shall be equal to the first sample size, resulting in a cumulative sample of 26 panels. Both the first 13 panels and second 13 panels of the sample shall be selected over the entire inspection lot at random. If the number of defectives found in the first sample is 0, the inspection lot shall be considered acceptable. If the number of defectives found in the first sample is greater than 0, but less than 3, the second sample of 13 panels shall be inspected. If the number of defectives found in the first sample is equal to or greater than 3, the inspection lot shall be rejected. The number of defectives found in the first and the second sample shall be accumulated. If the accumulated number of defectives is equal to, or less than 3, the inspection shall be considered acceptable. If the cumulative number of defectives is equal to or greater than 4, the inspection lot shall be rejected. 6 Factory production control 6.1 General The manufacturer shall control in each separate produc

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