DIN EN 14081-3:2012-04

This document (EN 14081-3:2012) has been prepared at the European Committee for Standardization (CEN) by Technical Committee CEN/TC 124 "Timber structures", the secretariat of which is held by AFNOR (France). The responsible committee at DIN, the German Institute for Standardization e. V., is Mirror Committee of NABau NA 005-04-01 AA "Holzbau" (Sp CEN/TC 124, CEN/TC 250/SC 5) ("Timber structures") (Mirror Committee of CEN/TC 124, CEN/TC 250/SC 5). This European Standard specifies requirements for factory production control of machine graded structural timber with rectangular cross-sections shaped by sawing, planing or other methods, and having deviations from the target sizes corresponding to EN 336. The requirements are additional to those given in EN 14081-1. Machine grading is in common use in a number of countries. Two basic systems are used, referred to as "output controlled" and "machine controlled". Both systems require a visual override inspection to cater for strength-reducing characteristics that are not automatically sensed by the machine. The output-controlled system is suitable for use where the grading machines are situated in sawmills grading limited sizes, species and grades in repeated production runs of around one working shift or more. This enables the system to be controlled by testing timber specimens from the daily output. These tests together with statistical procedures are used to monitor and adjust the machine settings to maintain the required strength properties for each strength class. With this system it is permissible for machine approval requirements to be less demanding and for machines of the same type to have non-identical performance. The machine controlled system was developed in Europe. Because of the large number of sizes, species and grades used it was not possible to carry out quality-control tests on timber specimens drawn from production. This system relies therefore on the machines being strictly assessed and controlled. Machine settings which remain constant for all machines of the same type are derived in the process. This requires significant test effort. The acceptability of grading machines and the derivation of settings rely on statistical procedures and the results will therefore depend on the method used. For this reason, this European Standard gives appropriate statistical procedures. The requirements in this European Standard are based on machines in current use and on future types of machines as far as these can be foreseen. Additional clauses or standards may be required if unforeseen developments take place. Compared to EN 14081-3:2006-03, the following modifications have been made: a) indicating property has been defined as a term; b) clause 7 has been revised to form informative Annex B; c) requirements for the use of control planks and a decision diagram for internal verification in connection with control planks have been added as Annex A.