GB/T 6491-2026Drying quality of sawn timber (English PDF)

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents".

Drafting.

This document replaces GB/T 6491-2012 "Sawn Timber Drying Quality". Compared with GB/T 6491-2012, the main differences are in structural adjustments and editorial changes.

Aside from the modifications, the main technical changes are as follows.

a) The target moisture content values for dried sawn timber for different applications have been revised (see Table 1 in 4.1, Table 1 in 3.2 of the 2012 edition);

Table 2 of 4.2.2.2 (Table 2 of 5.2 in the 2012 edition);

c) The limits for drying uniformity and moisture content deviation on thickness have been changed (see Table 2, Table 2 in version 5.2 of the 2012 edition);

d) Measurement instruments have been added (see 5.1);

e) The method for determining the moisture content of wood by gravimetric analysis has been modified (see 5.4.2, 6.1.3.1 of the 2012 edition);

f) The balancing or re-drying operation has been removed (see 6.1.3.3 in the 2012 version);

g) The location requirements for using electrical methods to assist in the measurement of core and surface water content have been increased (see 5.4.9);

h) The detection conditions for initial and final moisture content have been removed (see 6.1.3.8 in the 2012 version);

i) The degradation rate of dried sawn timber and the acceptance criteria for dried sawn timber have been removed (see 6.8 and 6.9 in the 2012 edition);

j) The equilibrium moisture content values for timber in major Chinese cities have been revised, and equilibrium moisture content values for timber in Hong Kong and Macau have been added (see Appendix A).

Appendix A of the 2012 edition);

k) The diagrams of equilibrium moisture content of timber and final moisture content of dried sawn timber for each region have been removed (see Appendix B of the 2012 edition).

Please note that some content in this document may involve patents. The issuing organization of this document assumes no responsibility for identifying patents.

This document was proposed by the National Forestry and Grassland Administration.

This document is under the jurisdiction of the National Technical Committee on Timber Standardization (SAC/TC41).

1 Scope

This document defines the terminology for sawn timber drying quality, specifies the target moisture content, quality indicators, quality grades, and requirements for dried sawn timber, and describes...

The paper describes the testing methods for the drying quality of sawn timber and establishes the judgment rules for the drying quality of sawn timber.

This document applies to the inspection of dried sawn timber.

2 Normative references

The contents of the following documents, through normative references within the text, constitute essential provisions of this document. Dated citations are not included.

For references to documents, only the version corresponding to that date applies to this document; for undated references, the latest version (including all amendments) applies.

This document.

GB/T 1927.9 Test methods for physical and mechanical properties of wood from small, flawless specimens – Part 9: Determination of bending strength GB/T 1927.10 Test methods for physical and mechanical properties of wood from small, flawless specimens – Part 10: Determination of modulus of elasticity in bending GB/T 1927.11 Test methods for physical and mechanical properties of wood from small, defect-free specimens – Part 11: Determination of compressive strength along the grain GB/T 1927.12 Test methods for physical and mechanical properties of wood from small, flawless specimens – Part 12: Determination of compressive strength across the grain GB/T 1927.13 Test methods for physical and mechanical properties of wood from small, flawless specimens – Part 13: Determination of compressive modulus of elasticity across the grain GB/T 1927.14 Test methods for physical and mechanical properties of wood from small, defect-free specimens – Part 14: Determination of tensile strength along the grain GB/T 1927.16 Test methods for physical and mechanical properties of wood from small, flawless specimens – Part 16: Determination of shear strength along the grain GB/T 1927.19 Test methods for physical and mechanical properties of wood from small, flawless specimens – Part 19: Determination of hardness GB/T 1927.20 Test methods for physical and mechanical properties of wood from small, flawless specimens – Part 20: Determination of splitting resistance GB/T 4823 Defects in Sawn Timber GB/T 15035-2023 Terminology for Wood Drying GB/T 36202 Terminology for Inspection of Sawn Timber

3 Terms and Definitions

The terms and definitions defined in GB/T 4823, GB/T 15035-2023 and GB/T 36202, as well as the following terms and definitions, apply to this document.

final moisture content the moisture content of the dried lumber at the end of the drying process.

[Source. GB/T 15035-2023, 3.5.24, with modifications] 3.2 MCm Technical specifications require the following moisture content for dried lumber.

Drying uniformity

deltaMCZ