Product certification HEAT-TREATED TIMBER TR

Transcription

1 Product certification HEAT-TREATED TIMBER

2 2 (13) CONTENTS 1 General Initial testing Inspection visits and external product testing Requirements for quality assurance Description of factory production control (FPC) Staff and organization Production facilities and equipment Testing facilities and equipment Production and quality control records and their archiving Production General Raw material, timber Battening and weights Heat-treatment process Prosess monitoring Meters and sensors Treatment process measurements Dry temperature Wet temperature Wood temperature Finished products testing and quality requirements Sampling (internal quality control testing) Moisture content Colour Equilibrium moisture content (EMC) Dimensional stability Checks Distortions Other defects Cutting to length of timber after heat-treatment Handling of deviating products Packaging, labelling and storage Packaging Labelling Storage Handling of complaints Notification of changes APPENDIX ThermoWood product classification

3 3 (13) Product Certification HEAT-TREATED TIMBER Scope of application Inspecta Certification Technical Committee has confirmed these specifications on The specifications shall enter into force on. Heat-treated timber classified according to ThermoWood product classification Thermo-S and Thermo-D. Applicable norms and standards 1 General 2 Initial testing CEN/TC 175 Thermal Modified Timber Definitions and characteristics, Technical specification. EN :2002 Moisture content of a piece of sawn timber- Part 1: Determination by oven dry method. EN :2002 Moisture content of a piece of sawn timber- Part 2: Estimation by electrical resistance method. These specifications set out the requirements for the quality assurance of heattreated timber manufacturing. Within this product group the certification covers the factory production control of heat-treated timber manufacturing (FPC). The product certification method is described in General Guidelines for Product Certification More information about heat-treated timber and production methods is found in the Thermowood handbook published by Lämpöpuuyhdistys ry. An inspection body shall carry out the initial inspection of the production facility, inspecting internal quality assurance description and implementation.

4 4 (13) 3 Inspection visits and external product testing An inspection body shall carry out an inspection of the production facilities twice a year to check the manufacturer s compliance with quality assurance requirements. The products shall be tested once a year by an external testing facility approved by Inspecta. The samples to be tested shall be selected by a representative of the inspection body. The certificate holder shall bear the costs of the inspection. Samples shall be taken in the following quantities: - 10 pieces, when treatment batch is < 20m³ - 15 pieces, when treatment batch is 20 50m³ - 20 pieces, when treatment batch is > 50m³ In external product testing the measurements that shall always be determined include surface, core and average moisture contents, colour values L*, a* and b* as well as internal crack percentage. The measurements will be approved if 80 % of the tested samples meet the set requirements. 4 Requirements for quality assurance 4.1 Description of factory production control (FPC) The operations and factory production control of the facility shall be described to the following minimum extent: - operation of the facility (e.g. operation chart) - manufacturing process from reception of raw materials to finished products - actuator settings - handling of deviating raw materials and products, including complaints - internal quality control guidelines, which should describe the measures performed during inspection and the recording of results in as great a detail as possible 4.2 Staff and organization The company shall appoint persons in charge of production in different production areas and their deputies, with the authorisation to maintain plant operations at the level required, who are at the same time committed to follow the given public authority and quality assurance guidelines. Staff shall have sufficient training and competence to carry out the appointed tasks. The company shall appoint a person responsible for quality control and his or her deputy.

5 5 (13) Duties of the person in charge of quality control include - ensuring compliance with and maintenance of quality assurance specifications - acting as contact person vis-à-vis the inspection body - being present at inspections The company is obligated to notify the inspection body of changes in the responsibility areas as soon as possible, however, no later than in connection with the next inspection. 4.3 Production facilities and equipment The condition of the production facilities and equipment shall be at all times enable the manufacturing of the products according to the requirements. Guidelines shall be issued for the maintenance of the equipment. 4.4 Testing facilities and equipment The testing facility should be well lit, warm and equipped with the following: - wood cutting circular saw - scale (precision of 0.01g) - oven for drying the test pieces (minimum temperature 103 C) - caliper gauge (readout precision of minimum 0.1mm) - tape measure (precision class II) - wood moisture content meter Guidelines shall be issued for the inspection and calibration of the equipment. The inspection of measuring instruments and moisture meters may be performed by comparing their readings with those of the inspector in connection with inspection visits. 4.5 Production and quality control records and their archiving Internal quality control is used to ensure that the products comply with requirements at various stages of production and delivery. Records should be kept for all quality assurance measures to the following minimum extent: - reception of raw materials - treatment process log - equipment maintenance and calibration

6 6 (13) 5 Manufacturing 5.1 General 5.2 Raw material, timber 5.3 Battening and weights - batch-specific identifiers (code, name of treatment formula, treatment commencement and ending times, temperature information) - complaints and their handling - deviations in production and products as well as resulting measures - quality control results (sampling, testing and statement of compliance) Records should be archived for a minimum of five years. No chemicals are allowed in the heat-treatment process, only water and heat. After heat-treatment the timber may not contain substances that artificially affect the properties of the wood. Such substances include, for example, various impregnants, oils and surface finishes. This does not apply to compounds natural to wood. The manufacturer shall have a procedure ensuring the raw material arriving for treatment complies with the requirements. The quality control records shall indicate the supplier, quality grade, dimensions, quantity and moisture content of received timber. Moisture content shall be measured in accordance with standard EN An electric resistance meter with the option of wood type and temperature selection and with insulated sensor spikes shall be used for measuring. If the meter does not have temperature selection, the set values and the reducement of measurement result shall be marked on the meter. The raw material shall be with sawn surface. The timber may be green or pre-dried. All observations regarding the raw material that may affect the production process or manufacturing of the products in compliance with the requirements shall be recorded. The battening of the treatment load should be performed carefully to ensure the products compliance with requirements as regards distortions, for example. The battens shall be intact and straight, and their thickness shall be as

7 7 (13) 5.4 Heat-treatment process 5.5 Process monitoring Meters and sensors dimensionally accurate as possible. The battens shall be placed on the treatment load at even intervals of approx mm; the last of the battens shall be placed as close as possible to the end of the timber (max. 100mm). During storage the battens shall be kept covered from rain. The use of weights is recommended. Weights help ensure the products compliance with the requirements as regards distortions. The heat-treatment process shall comprise the following three phases - drying - heat-treatment - conditioning Drying is usually the longest phase in the heat-treatment process. The duration of the phase depends on, for example, wood dimensions, type of wood and the initial moisture content of the wood. The treatment phase following drying is heat-treatment, whereby the temperature of the treatment chamber and the wood are raised to the required level, with an exposure period sufficiently long to ensure the product s compliance with the requirements. The phase following heat-treatment is conditioning, whereby the moisture content of the wood is restored to as close as possible to the equilibrium moisture of the products intended usage conditions. The duration of the conditioning phase depends on factors such as dimensions, treatment level and the conditioning circumstances. In addition to drying, heat-treatment and conditioning, the process contains various phases involving temperature increase and decrease. The company shall have sufficient technical equipment capabilities to carry out production process control. The company shall have a computer, visual display unit and if needed accessories enabling remote login. Process logs shall be stored either in electronic form or as paper versions. Reliable meters and sensors shall be available for process measurements and control. Instructions issued by the equipment manufacturer shall be followed in the use, calibration and maintenance of meters and sensors. Faulty meters and

8 8 (13) sensors shall be repaired immediately, or before the commencement of the next process at the latest. Written instructions shall be available for the use and calibration of measuring equipment. The correspondence of monitoring equipment displays with the sensors shall be inspected at least every six months; the results shall be recorded. The date for the next calibration shall be marked on the measuring equipment Treatment process measurements Dry temperature Wet temperature Dry temperature shall be measured for the entire duration of the treatment process. The temperature shall always be measured on the treatment chamber s blower side (before the load), and secondarily on the chamber s suction side (after the load). If the direction of air flow is changed, the measuring side shall also be changed. In processes where wood temperature is not measured, air temperature shall always be measured on both sides. The number of measuring points shall correspond to the treatment chamber load capacity. The minimum number of measuring points shall be as follows: - when the treatment batch is < 20m³, the number of measuring points shall be 1/blow direction - when the treatment batch is 20 50m³, the number of measuring points shall be 2/blow direction - when the treatment batch is m³, the number of measuring points shall be 2 4/blow direction - when the treatment batch is > 100m³, the number of measuring points shall be 4/blow direction If there is more than one measuring point available on both blow and suction sides, the temperatures shown on the display shall be the average temperature of the measuring points on the side in question. Wet temperature shall be measured constantly during the process in connection with temperature increase, drying and conditioning. Before commencing the process, the condition of the sensor and the fabric shall always be inspected, ensuring that water passes to the water dish.

9 9 (13) Wood temperature Measuring of wood temperature is compulsory, if the treatment process is controlled on the basis of wood temperature. The measuring points shall be located on both sides of the treatment load. Holes for the temperature sensors shall be drilled midway through timber thickness; the probe should protrude firmly into the wood to a depth of at least 40mm. The number of measuring points shall correspond to the treatment chamber load capacity. The minimum number of measuring points shall be as follows; - when the treatment batch is < 20m³, the number of measuring points shall be 2 3/side - when the treatment batch is 20 50m³, the number of measuring points shall be 2 4/side - when the treatment batch is m³, the number of measuring points shall be 3 4/side - when the treatment batch is > 100m³, the number of measuring points shall be 4/side The recorded temperature of the wood shall be the average of the measurements. 6 Finished products testing and quality requirements The products compliance with requirements shall be determined through the testing of finished products. Records shall always be kept of testing, indicating the tests carried out on the product batch, test results, party carrying out the testing and statement of the products' compliance with the requirements. 6.1 Sampling (internal quality control testing) The manufacturer shall take test pieces from each treatment batch, from different parts of the treatment load. The samples should be marked to enable the establishment of their origin and compliance with quality control records. Samples should be at least 25 cm in length, taken from approximately one metre from the end of the timber. The sampling shall include 1 sample/piece of timber. Sampling shall be carried out as follows: - 5 pieces, when treatment batch is < 20m³ - 10 pieces, when treatment batch is 20 50m³ - 15 pieces, when treatment batch is > 50m³ The test pieces shall be kept away from rain and sunlight. The test pieces from the last 25 treatment batches shall be preserved.

10 10 (13) 6.2 Moisture content Due to the low final moisture content, the moisture content of heat-treated timber is determined using the so-called dry-weight method in accordance with standard EN Moisture content is determined from cross-sections taken from at least one metre from the end of the timber. Measurements shall be taken from each treatment batch and from different parts of the treatment load, possibly from several batten bundles. Moisture content after treatment should be as close as possible to the equilibrium moisture content of the intended usage conditions, the allowed minimum average moisture content being 4%. The moisture gradient between surface and inner part shall be < 3%. 6.3 Colour Colour shall be determined colorimetrically according to the CIELAB colour space. Measurement shall use the L*a*b* colour coordinates, whose values are processed in numeric form. Coordinate L* shall represent the colour of heattreated wood; the value 0 shall denote black and the value 100 shall denote white. Colour shall be measured on the face of the piece, on a faultless surface of which 2 3mm has been planed off. The colour value L* of each sample shall be the average measurement of three measuring points. Significant deviations from average process duration, timber density, spring and summer wood shares, and growth ring grain angles may cause variation in the colour values. Furthermore, the brand of the colour meter and the sensor probe diameter may also affect the measured colour values. In internal quality control the measuring of colour is voluntary. 6.4 Equilibrium moisture content (EMC) Equilibrium moisture content shall be determined by conditioning the test pieces (dimensions e.g. 20 x 20 x 50mm) under conditions where the temperature is 20 C ±2 C and relatively humidity RH 65% ±5%. The test pieces shall be deemed to have reached equilibrium moisture content, when the difference in their weight compared to the change in the previous weighing is < 1%. The period between the two weighing events shall be no less than 24 hours. Moisture content shall be measured in accordance with standard EN Equilibrium moisture content should meet the requirements outlined in appendix 1. As required, relative humidity shall also be determined under conditions t = 20 C, RH = 35% (dry conditions) as well as t = 20 C, RH 85% (humid conditions). In internal quality control the determination of equilibrium moisture content is voluntary.

11 11 (13) 6.5 Dimensional stability Dimensional stability is determined at a constant temperature (t = 20 ±2 ) by changing relative humidity (RH = 35%, 65%, 85% ± 5%). The measurements shall be indicated as radial, tangential and longitudinal changes in dimension or as the change in the total volume of the piece. Conditioning shall be performed as specified under section 5.4 equilibrium moisture content (EMC). In internal quality control the determination of dimensional stability is voluntary. 6.6 Checks Surface checks extending the full length of the timber are not permitted. Checks running through the timber are not permitted, unless the check is at the end of the piece and its length does not exceed the width of the piece. Checks running through the timber are not permitted on finished products. Internal checks are examined from cross-sectional surfaces of the pieces. The cross-section shall be taken from at least one metre from the end of the piece, in a place where knots cannot be deemed to contribute to the creation of internal checks. If the number of pieces containing internal checks detected through quality control is 15%, the number of pieces to be inspected shall be doubled. The quality requirements for surface and internal checks are presented in the table in appendix Distortions 6.8 Other defects The products shall meet the requirements set for distortions outlined in appendix 1. Mechanical defects are not permitted. Face-through knots are not permitted. 6.9 Cutting to length of timber after heat-treatment Heat-treated timber shall be cut to its final length after the heat-treatment. In connection with planing the timber s cross-sectional dimensions shall be measured and the measurements entered in the quality control logs.

12 12 (13) 6.10 Handling of deviating products Deviations occurring at the treatment facility during the process shall be identified. Possible deviations and measures for their correction shall be recorded. Measures to prevent the reoccurrence of similar deviations shall be launched whenever deviations are detected. 7 Packaging, labelling and storage 7.1 Packaging 7.2 Labelling Heat-treated packages of sawn timber shall be wrapped in plastic or paper, fully covered on at least three (3) sides. Planed products shall be covered on five (5) sides, using corner protection when tying the products together. This practice may be deviated from only upon separate agreement between the manufacturer and the customer. The products or product packages shall be labelled, indicating the following: - manufacturer - treatment batch code or number - product class Thermo-S or Thermo-D - dimension - number of pieces/total volume m³ - certification mark 7.3 Storage The package slip shall be attached to the end of the timber package and the lower part of the side, using weather-resistant staples suitable for woodworking machines. The storaging of the products must not weaken the products properties.

13 13 (13) 8 Handling of complaints 9 Notification of changes The manufacturer has a duty to record all complaints regarding the products. The records shall indicate the reason for the complaint. The manufacturer shall be able to locate the quality control records for the batch against which the complaint was made. Complaint reports shall also contain the facility's measures for rectifying the complaint as well as the outcome of the case. The certificate holder shall notify the inspection body of material changes in the raw materials, manufacturing or quality assurance of the products. APPENDIX Appendix 1. ThermoWood product classification

14 APPENDIX 1 ThermoWood product classification APPENDIX 1 1 (2) The ThermoWood product classification is two-tiered, separately applied to softwood and hardwood. The product classes are called Thermo-S and Thermo-D. Production methods deviating from the instructions do not carry the right to use product classification Thermo-S and Thermo-D. Product classes for heat-treated timber indicate the requirement level set for the class in question in the manual s general ThermoWood product classification. On the basis of the information provided by the manufacturer and the distributor, the user selects the product class for heat-treated timber according to the intended use and environmental conditions. The Thermo marking indicates that the timber has been heat-treated. The code S refers to improved dimensional stability (stability) and D to improved weather resistance (durability). Thermo-S class treated timber is recommended primarily for indoor use and Thermo-D class treated timber for outdoor use. The requirements apply only to tree species grown under average Nordic conditions: pine, spruce and birch as well as grades of timber sawn from these tree species.

15 APPENDIX 1 2 (2) Production and quality requirements for ThermoWood production in product classes Thermo-S and Thermo-D. Softwood Hardwood (birch) Requirement/Property Thermo-S Thermo-D Thermo-S Thermo-D - Treatment temperature C (wood) 190 ± ± ± ± 3 - Treatment time (h) Final moisture average moisture % - Equilibrium moisture content % T = 20 C, RH 65%, Colour, L* component Surface checks check length % timber thickness (mm) < 25 < 35 < 25 < 35 < 25 < 35 < 25 < 35 - Internal checks check % timber thickness (mm) < 5 < 5 < 5 < 5 - Distortions Bow (mm per 2m length) Spring (mm per 2m length) Cupping (% of timber width) Twist (% of timber width) < 4 < 2 < 6 < 4 < 2 < 6 < 4 < 2 < 6 < 4 < 2 < 6