How do you evaluate the conformity of a batch of wood flooring elements? We take a close look at a EU Standard that might not yet received all the attention it deserves...
What a technical standard is and its importance are both probably well known by the vast majori- ty of operators in the sector: anyone who works in the wood flooring market today is required to know the standard if they want to be professionally prepared and ready to answer any question their cus- tomer or anyone else asks.
In the universe of EU technical standards (EN) that are widely (perhaps) applied by operators in the sector (such as prod- uct standards EN 13226, EN 13227 and EN 13489, Standard EN 14342 issued in 2008 for EC marking) there are also many that are not as widely adopted, perhaps because they are relatively unknown or have received less attention but which are no less important than the others just the same. These technical standards are no less important because they often provide information and values that help provide better knowledge of a determined term, as is the case of Standard EN 13756:2002 (Wood flooring – Terminology) or be- cause they enable the monitoring of a determined characteristic, such as Standard EN 1534:2011, which provides an analy- sis of the ways to check resistance to in- dentation.
The constantly expanding complex and intricate universe of technical standards also includes EU Standard EN 14762 issued in February 2006 by the Technical Committee CEN/TC 175 "Round and sawn timber" with identification code ICS 79080. According to the directives of the European Standards Committee, this Eu- ropean standard has been assigned the status of national standard, and when- ever in a European Union member nation a national standard contrasts with this one (not in Italy, in this case), the former must be withdrawn. The European Technical Committee CEN/CENELEC has specified the na- tional standards bodies of the nations bound to comply with European Stan- dard EN 14762: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Fin- land, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,Luxemburg, Malta, Netherlands, Nor- way, Poland, Portugal, Romania, Slova- kia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom.
Field of application and content of the Standard
The full name of the Standard identified with Number 14762 approved by the CEN on December 30, 2005 and valid since February 2006 is: “Wood flooring – Sampling procedures for evaluation of con- formity of a batch of wood flooring ele- ments”. This European Standard defines the sam- pling procedures to be used for the eval- uation of conformity in product stan- dards for a batch of wood flooring ele- ments at the time of first delivery of the product.
It applies separately to each of the fol- lowing characteristics: moisture content, dimensions and appearance. For all the other characteristics and properties of wood floor laying elements, it would be better for the evaluating parties to apply specific evaluation procedures and adopt adequate methods of verification. Euro- pean Standard 14762:2006 applies to wood flooring elements in the following product standards:
- EN 13226 (Wood flooring - Solid par- quet elements with grooves and/or tongues );
- EN 13227 (Wood flooring - Solid lam- parquet products);
- EN 13228 (Wood flooring - Solid wood overlay flooring elements including blocks with an interlocking system);
- EN 13488 (Wood flooring - Mosaic par- quet elements);
- EN 13629 (Wood flooring - Solid pre-as- sembled hardwood board);
- EN 14761 (Wood flooring - Solid wood parquet - Vertical finger, wide finger and module brick).
As regards flooring product Standard EN 13489 (Wood flooring – Multi-layer par- quet elements with an interlocking sys- tem), only the moisture content and dimensions of the laying elements can be evaluated for conformity.
General index and reference standards
The European standard in question is di- vided into five specific chapters: 1) Scope; 2) Reference Standards; 3) Terms and de- finitions; 4) Rules for evaluation of con- formity and 5) Methods for the drafting of the final conformity evaluation report. A useful bibliography of standards to be consulted (see the panel enclosed) is pro- vided at the end.
In addition to the regulatory framework provided in the bibliography Standard EN 14762 emphasizes the importance of two other specific Standards documents that are indispensable to its application: EN 13756:2002 (Wood Flooring - Termi- nology) and ISO 2859-1 (Sampling pro- cedures for the inspection of attributes - Part 1: Sampling methods indexed to Ac- ceptance Quality Limit (AQL) per batch under evaluation).
Terms and definitions
Chapter 3 of Standard EN 14762, dedi- cated to the terms and definitions that must be known in order to better com- prehend and apply the Standard in ques- tion is both important and exhaustive.
- Batch. This is the limited quantity of el- ements delivered at one time that can be assembled together and where the elements are defined to conform to es- tablished requisites.
- Batch dimensions. This is the number of elements in a batch to be checked, and is identified with the letter “N”.
- Sample. This is the number of elements taken from the batch for the evaluation of the conformity of a specific proper- ty envisioned as written above.
- Dimensions of the sample. This is the number of the wooden elements in- cluded in the so-called sample and is represented by the letter “n”.
- Sampling element. This is one of the el- ements that make up the sample.
- Acceptance limit. This is the maximum number of non-conforming elements in the sample with which the batch can still be accepted, and is represented by the letters “Ac”.
- Non-acceptance limit. This is the mini- mum number of non-conforming ele- ments in the sample with which the batch will not be accepted, and is rep- resented by the letters “NAc”.
Chapter 4 of Standard EN 14762 specifies the methods to be applied when evalu- ating conformity. The sampling plan (provided in Prospec- tus 4) is based on statistics Technical Standard ISO 2859-1. The AQL value (Acceptance Qual- ity Value) is set at 6.5, which is equal to a normal quality control level of 2.
Prospectus 4 also specifies the number of elements to be evalu- ated, while bearing in mind that wood floor laying elements must be tak- en at random from the batch and that the sample, in turn, must be evaluated for the characteristics of the product (described above in Scope) and that all must be a part of the same sample. As regards the moisture content of the el- ements, 10 tests must be made on the el- ements selected at random from each sample, making sure to calculate the mean value for subsequent use in evalu- ating the conformity of the entire batch from which the sample was taken.
Evaluation of conformity
Chapter 4, Paragraph 2.1 specifies the property to which the elements compos- ing the sample must be subjected for con- formity evaluation. Every single element must be evaluated individually in regard to species of wood, classification, geo- metrical characteristics, moisture content and any other characteristic(s) mutually agreed between the parties.
Type of wood and qualitative classification
The evaluation of the type of wood must be performed through visual inspectionor instrumental measurement unless oth- er agreements have been reached be- tween the parties. An evaluation of the qualitative classifi- cation of the species of wood of the wood floor laying elements must adopt as ref- erence the limits indicated in the various prospectuses provided in the various product standards or the other agree- ments in the contract. In this case as well so, evaluation must be performed by vi- sual inspection and comparing and ver- ifying the specific requisites provided in individual product standards.
Geometric characteristics and moisture percentage
Also the dimensional and geometric char- acteristics of the elements must be eval- uated through the use of the methods above and the limits specified in indi- vidual product standards or stipulated by contract wherever such characteristics are indicated.
Moisture content, on the other hand, must be evaluated with the use of the methods established by the specific stan- dard; the mean value obtained must be analyzed by consulting the standard for the specific product or compared with the value set in the contract.
Whenever agreed between the parties, specific properties must conform to either the limits specified in individual product standards (when present) or the values established in the contract.
Evaluation conclusions and the Report
The Standard provides for various types of evaluation. The batch is considered accepted when the number of non-conforming elements falls within the limits of acceptance spec- ified for each dimension of the batch spec- ified in the Prospectus.
Whenever the number of non-conform- ing elements is equal to or greater than the limit of non-acceptance after the first sample, the batch is rejected.
Whenever the number of non-conform- ing elements is included between the lim- it of acceptance and the limit of non-ac- ceptance after the first sample, a second sample must be taken into consideration. The batch is considered accepted when- ever the number of non-conforming ele- ments is included within the level of ac- ceptance for the second sample. Whenever the number of non-conform- ing elements is equal to or greater than the limit of non-acceptance after the sec- ond sample, the batch is rejected.
The final part of Standard EN 14762 spec- ifies the methods to be followed for the drafting of the evaluation report on the conformity of the entire batch considered. Such report must contain at least the in- formation regarding: the name of the par- ty requesting inspection; the name of the producer; information on the product (species of wood, classification, evalua- tion date); dimension of the batch (N); di- mensions of the sample (n); evaluation results (with the suggestion to report and analyze also the most probable causes of the non-conformities observed during an- alytic evaluation).
Even if this Standard may initially ap- pear complex and difficult to apply, it is not necessarily so in reality because the characteristics to monitor are common- ly verified by operators in the sector (moisture percentage, dimensions, tol- erances), the evaluation methods are simple and widely-known, and because the statistical model to be applied is re- duced to a minimum.
Considering that the average wood floor is composed of hundreds of wooden elements, the application of this Standard permits an efficacious re- sult to be obtained, in addition to the tangible possibility of correctly, un- equivocally and precisely knowing, monitoring, checking, and comparing whatever you produce, sell, or lay, and all of which in complete respect of the requisites established between the pro- ducer, the seller, the floor’s layer and the final consumer.
THREE EXAMPLES OF APPLICATION
1. A 100 sq m wood floor composed of single-layer elements of 350 x 70 x 10 mm dimensions amounts to approx. 5,555 elements laid. The dimension of the sample is 125 elements on which to perform the simple checks specified by the Standard. The batch will be accepted with no more than 11 elements that do not conform to the requisites established in the product standards for single characteristics. If, instead the number of non-conforming elements is 16, the batch will not be accepted, whereas if such non-conformities are in the range of 12 - 15 elements, a second sampling (also composed of 125 elements) must be performed. After the checks conducted on this second sample, if the number of non-conforming elements is 26, the batch is accepted, whereas if such non-conformities are 27 or more, the batch is not accepted.
2. A 150 sq m wood floor composed of multi-layer elements of 1.800 x 300 x 14 mm dimensions amounts to approx. 278 elements. The dimension of the sample is therefore 20 elements. The batch will be accepted with no more than 2 elements that do not conform to the requisites established in the product standards for single characteristics. If, instead the number of non-conforming elements is 5, the batch will not be accepted, whereas if such non-conformities are in the range of 3 - 4 elements, a second sampling (also composed of 20 elements) must be performed. After the checks specified by the Standard have been conducted on this second sample, if the number of non-conforming elements is 6 or below, the batch is accepted, whereas if such non-conformities are 7 or more, the batch is not accepted.
3. An 80 sq m wood floor composed of multi-layer elements of 900 x 120 x 14 mm dimensions amounts to approx. 740 elements. The dimension of the sample is therefore 50 elements. The batch will be accepted with no more than 5 elements that do not conform to the requisites established in the product standards for single characteristics. If, instead the number of non-conforming elements is 9, the batch will not be accepted, whereas if such non-conformities are in the range of 6 - 8 elements, a second sampling (composed of 50 elements) must be performed. After the checks specified by the Standard have been conducted on this second sample, if the number of non-conforming elements is 12 or below, the batch is accepted, whereas if such non-conformities are 13 or more, the batch is not accepted.