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DIN Standards Committee Building and Civil Engineering

Overview

Machine grading is in common use in a number of countries. Two basic systems, referred to as "output controlled" and "machine controlled", are used. 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 are used together with statistical procedures 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. The system relies therefore on the machines being strictly assessed and controlled. Furthermore, considerable effort is required to derive the machines settings, which remain constant for all machines of the same type. The acceptability of grading machines and the derivation of settings rely on statistical procedures. The results will therefore depend on the method used. For this reason, this document 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 their use can be foreseen. Additional clauses or standards may be required if unforeseen developments take place. This document specifies requirements, additional to those in EN 14081-1, for initial type testing 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. This includes requirements for strength grading machines and test equipment for proof loading graded material. The following changes have been made with respect to DIN EN 14081-2:2006-03: a) EN 336 has been moved from the normative references to the Bibliography; b) EN 14081-4 has been added to the normative references; c) clause 6 has been revised and extended; d) a simplified formula to formula (A.1) has been added to Annex A; e) B.2 in Annex B has been revised; f) the standard has been completely editorially revised.

Document: references other documents

Responsible national committee

NA 005-04-01 AA - Timber structures (national mirror committee for CEN/TC 250/SC 5, ISO/TC 165)  

Responsible european committee

CEN/TC 124/WG 2 - Solid timber