NORME INTERNATIONALE CEI IEC INTERNATIONAL STANDARD 60216 4 3 Première édition First edition 2000 04 Matériaux isolants électriques – Propriétés d''''endurance thermique – Partie 4 3 Etuves de vieillisse[.]
Généralités
The structure must be built robustly using suitable materials All electrical devices and auxiliary systems should be easily accessible for maintenance purposes.
The construction should be designed to accommodate the equipment intended for cutting off the power supply to the oven It is preferable to include an audible alarm that activates when the temperature, monitored by a thermostat, deviates from the permitted range or if the air supply fails.
Chambres destinées aux éprouvettes
Ovens must have at least two approximately cylindrical chambers that are open at the top and fitted with appropriate lids These chambers should be mounted so that their axes are nearly vertical Each lid must create an airtight seal with the chamber, ensuring that gas leakage from the ventilation joint does not exceed 5% of the airflow corresponding to the ventilation gas relative to the chamber containing the sample.
NOTE 1 Certains types de joints de forme circulaire ont été considérés comme satisfaisants.
Sauf spécification contraire, les chambres individuelles doivent avoir au moins 35 mm de diamètre et 200 mm de longueur.
The materials used for the chambers, their covers, and internal components must be free from copper, copper alloys, or any substances that could interfere with volatile materials across the entire temperature range of the oven, such as certain silicone resins.
La conception doit être telle qu’elle permette de nettoyer facilement les chambres après chaque essai.
Rooms should be assembled in a temperature-controlled environment using a thermostat, such as within a metal block, liquid, sand bath, saturated steam bath, or forced air circulation oven Characteristic design examples are illustrated in Figures 1 and 2.
NOTE 2 Les résultats obtenus dans des étuves à circulation d’air forcé sont dans ce contexte habituellement moins intéressants que d’autres systèmes.
Renouvellement d’air
Chaque chambre doit être équipée d’une alimentation en air contrôlée en permanence, filtrée, préchauffée, l’air pénétrant dans la chambre par une extrémité et étant aspiré vers l’autre extrémité.
Si cela est spécifié dans le contrat d’achat, des précautions doivent être prises pour utiliser des gaz de ventilation autres que l’air.
Des taux de renouvellement d’air compris entre 5 et 20 renouvellements par heure doivent être possibles.
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The oven shall be soundly constructed using suitable materials All electrical and other ancillary fittings shall be readily accessible for maintenance purposes.
The construction must include equipment that automatically shuts off the oven and ideally triggers an alarm if the temperature of the thermostatically controlled medium falls outside the permitted range or if there is a failure in the supply of ventilating air.
The ovens must feature a minimum of two open-topped, cylindrical chambers positioned vertically, each equipped with a lid that creates a tight seal The seal's effectiveness is crucial, as the leakage of ventilating gas from the lid should not exceed 5% of the gas flow rate directed to the specimen chamber.
NOTE 1 Some types of 'O' ring seals have been found to be satisfactory.
Unless otherwise specified, the individual chambers shall have a minimum diameter of 35 mm and a minimum length of 200 mm.
The construction materials for the chambers, lids, and internal components must be free from copper, copper alloys, and any substances that could release interfering volatiles within the oven's temperature range, such as certain silicone resins.
The design shall be such as to permit the chambers to be easily cleaned after each test.
The chambers should be installed in a heat transfer medium that is controlled by a thermostat, such as a metal block, liquid bath, sand bath, saturated vapor bath, or an air circulating oven Typical design examples are illustrated in figures 1 and 2.
NOTE 2 The performance of air circulating ovens in this context is usually poorer than the alternative systems.
Each chamber shall be provided with a supply of continuously metered, filtered, pre-heated ventilating air, entering the chamber at one end and being exhausted through the other.
When specified in the purchase contract, provision shall be made for the use of ventilating gases other than air.
Ventilation rates in the range 5 to 20 changes per hour shall be available.
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The incoming air must be directed towards a cylindrical wall of the chamber to create a turbulent flow within the cell, while the overall design should minimize air recirculation within each chamber To prevent cross-contamination of volatile components, the air renewal from one chamber must not come into contact with the samples from another chamber It is advisable for the air extracted from the chambers to be released into the external atmosphere, with precautions in place to ensure that volatile substances emitted from aged samples do not pose a risk to health or the environment.
It is essential to ensure the proper purity of the incoming compressed air to minimize its impact on the results If test outcomes are affected by impurities in the ventilation environment, such as water vapor, this must be monitored and documented.
Dispositions pour le montage des éprouvettes
Measures must be taken to support and/or suspend the test tubes, ensuring they are placed in each chamber without contact with one another or the chamber walls The test tubes and supports should not occupy more than 25% of the cross-sectional area of the chamber in any plane, exceed 50% of the longitudinal cross-sectional area in any plane, or occupy more than 10% of the actual working volume of the chamber.
Commande de température
La température dans le volume d’exposition doit être contrôlable dans les limites données en 5.1.1.
5 Méthodes d’essai et exigences de performance
Variation de température
Exigence
Le volume d’exposition doit être constitué d’au moins 70 % du volume central de la chambre avec la variation maximale autorisée, indiquée dans le tableau 1.
Tableau 1 – Variation de température maximale autorisée
Gamme de températures Variation de température Dérive maximale autorisée de la température moyenne globale au cours d’une période de 5 jours °C K K
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The design of the chamber should ensure that incoming air is directed towards the cylindrical wall to create turbulent flow, minimizing air recirculation within each chamber To prevent cross-contamination of volatile components, the ventilating air from one chamber must not interact with specimens in other chambers It is advisable to vent exhaust from the chambers to the outside atmosphere, while implementing measures to protect health and the environment from harmful volatiles produced by ageing specimens.
To ensure accurate test results, it is essential to maintain the purity of incoming ventilating air Any impurities, such as water vapor, that may affect the outcomes must be controlled and documented.
Each chamber must be equipped to support, suspend, and position specimens without allowing them to touch one another or the chamber walls The combined area of the specimens and their supports should not exceed 25% of the cross-sectional area in any plane, 50% of the longitudinal cross-sectional area in any plane, or 10% of the effective working volume of the chamber.
The temperature in the exposure volume shall be controllable to the limits given in 5.1.1.
5 Test methods and performance requirements
The exposure volume shall constitute at least the central 70 % of the volume of the chamber with the maximum allowable temperature variation given in table 1.
Table 1 – Maximum allowable temperature variation
Temperature range Temperature variation Maximum allowable drift in global average temperature over 5-day period ° C K K
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Méthode d’essai
5.1.2.1 On doit placer une série de capteurs de température d'un diamètre maximal de 3 mm dans le volume d’exposition de la chambre en essai, en s’assurant a) qu’un capteur est situé à 10 mm au plus du centre de la chambre; b) qu’un capteur est situé au sommet du volume en essai et qu’un autre capteur est situé au fond du volume, diamétralement opposé au capteur du haut; c) que six capteurs complộmentaires sont situộs de faỗon à ờtre approximativement équidistants de la ligne centrale et les uns des autres.
To minimize heat conduction from the temperature sensor, it is essential to ensure that there is a sufficient length of connection wire inside the oven Additionally, the wires should be routed close to or through the temperature-controlled environment externally.
If calibrated temperature sensors, such as platinum resistance thermometers or thermocouples, are unavailable, it is possible to use thermocouples made from the same wire coils, provided they yield temperature readings that do not vary by more than 0.2 K when placed adjacent to each other in the test chamber set to its maximum operating temperature.
5.1.2.2 Porter la température de l’étuve à sa température de fonctionnement maximale et la laisser se stabiliser Mesurer à 0,1 K près la température donnée par les capteurs, un certain nombre de fois au cours d’une période d’environ 3 h pour identifier un éventuel comportement cyclique et permettre de déterminer les températures maximale, minimale et moyenne de chacun des thermocouples pendant la période de mesure.
NOTE 1 A partir des lectures faites, il est facilement possible de calculer la fluctuation de température en un point et la différence de température à n’importe quel moment.
NOTE 2 L’utilisation d’un enregistreur de données est judicieuse pour cette opération.
5.1.2.3 Calculer à 0,1 K près la moyenne des neuf températures moyennes et noter cette valeur comme étant la température moyenne globale de la chambre.
5.1.2.4 Calculer la différence entre la température la plus élevée et la température la plus basse, déterminées conformément à 5.1.2.2, et noter cette valeur comme étant la variation de température Celle-ci ne doit pas excéder les valeurs données au tableau 1.
5.1.2.5 Maintenir l’étuve aux mêmes températures pendant cinq jours, c’est-à-dire 120 h.
Temperature variation should be measured once daily, in accordance with sections 5.1.2.2 and 5.1.2.4, and must not exceed the values specified in Table 1 The overall average temperature of the chamber must be determined as per section 5.1.2.3 during each of the six measurement periods Additionally, the maximum variation over a five-day period should not exceed the values listed in Table 1.
Constante de temps
Exigences
Si cela est spécifié dans le contrat d’achat, la constante de temps ne doit pas excéder une valeur spécifiée.
NOTE Ce paramètre est important uniquement si l’étuve est utilisée pour des conditionnements thermiques de courte durée (essai de choc thermique).
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5.1.2.1 A series of 3 mm maximum diameter temperature sensors shall be placed in the exposure volume of the chamber under investigation, ensuring that a) one sensor is located within 10 mm of the centre of the chamber; b) one sensor is located at the top of the volume under consideration and another sensor is located at the bottom of the volume, diametrically opposite to the top sensor; c) six additional sensors are located so as to be approximately equidistant from the centre line and from each other.
To minimize heat conduction from the temperature sensor, it is essential to maintain a sufficient length of connecting wire within the oven and to route the external wires close to or through the thermostatically controlled medium.
If calibrated temperature sensors like platinum resistance thermometers or thermocouples are unavailable, thermocouples made from the same spools of wire can be utilized However, it is essential that these thermocouples, when placed next to each other in the testing chamber at the maximum operating temperature, show temperature readings that differ by no more than 0.2 K.
5.1.2.2 Raise the oven to its maximum operating temperature and allow it to stabilize.
Monitor the temperature of the sensors to an accuracy of 0.1 K multiple times over a span of about 3 hours This process will help identify any cyclic patterns and enable the calculation of the maximum, minimum, and average temperatures for each thermocouple during the measurement period.
NOTE 1 From these readings, the temperature fluctuation at one point and the temperature difference at any one time can be easily calculated.
NOTE 2 Use of a data logger is advisable for this operation.
5.1.2.3 Calculate the average of the nine mean temperatures to 0,1 K and record this value as the global average temperature of the chamber.
5.1.2.4 Calculate the difference between the highest maximum temperature and the lowest minimum temperature determined according to 5.1.2.2 and record this as the temperature variation This shall not exceed the values given in table 1.
5.1.2.5 Maintain the oven at the same set temperature for five days, i.e 120 h Measure the temperature variation once a day according to 5.1.2.2 and 5.1.2.4 This shall not exceed the values given in table 1 The global average temperature of the chamber shall be determined according to 5.1.2.3 during each of the six measuring periods The maximum variation over the five-day period shall not exceed the values given in table 1.
When specified in the purchase contract the time constant shall not exceed a specified value.
NOTE This parameter is only of importance when the oven is used for short term thermal conditioning (thermal shock testing).
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Procédure d’essai
Utiliser une éprouvette normalisée faite d’un cylindre solide en laiton dont le diamètre est de
10 mm ± 0,1 mm et la longueur de 55 mm ± 0,1 mm, auquel a été soudée une liaison avec un thermocouple différentiel.
Set the oven to 200 °C or its maximum usable temperature, whichever is lower, and allow it to stabilize Let the standardized test specimen acclimate to room temperature for about 1 hour.
Follow the manufacturer's instructions to open the chamber and quickly suspend the standardized test tube vertically near the geometric center of the oven using a heat-resistant cord with a diameter not exceeding 0.25 mm Ensure that the free end of the thermocouple is suspended as far away as possible from the standardized test tube without contacting the chamber walls and remains within the actual working volume Keep the chamber open for a total of 60 seconds ± 2 seconds, then replace the chamber cover Record the temperature difference every 10 seconds until reaching the maximum.
Continuer l’enregistrement toutes les 30 s jusqu’à ce que la différence de température chute de
10 % par rapport à son maximum, et reporter les valeurs enregistrées en fonction du temps exprimé en secondes.
Diviser la différence maximale de température par dix et enregistrer cette valeur comme étant T 10
Based on the temperature difference curve over time, determine the time, in seconds, required to transition from the recorded maximum to T 10 This value represents the time constant and must not exceed the specified limit.
The oven supplier must provide essential information, including the temperature range that meets the standard's variation requirements, available air renewal options, and the power supply voltage range along with maximum consumption Additionally, the supplier should specify the maximum ambient temperature for compliance, the number of test chambers, and the exposure volume dimensions for each chamber Test results as outlined in Article 4, external dimensions, and the total mass of the empty oven must also be included Finally, recommendations for quality control methods for air renewal, such as filtering, dehumidification, and appropriate measurement techniques, should be provided.
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Provide a standard specimen consisting of a solid brass cylinder 10 mm ± 0,1 mm in diameter and 55 mm ± 0,1 mm long to which one junction of a differential thermocouple has been soldered.
Preheat the oven to 200 °C or its maximum designed temperature, whichever is lower, and let it stabilize Meanwhile, allow the standard specimen to acclimate to ambient temperature for about 1 hour.
To conduct the experiment, follow the manufacturer's instructions by opening the chamber and suspending the standard specimen vertically at the oven's geometric center using a heat-resistant cord no thicker than 0.25 mm Ensure the thermocouple's free end is positioned away from the specimen and does not touch the chamber walls, remaining within the effective working volume Keep the chamber open for 60 seconds ± 2 seconds before closing it Record the temperature difference every 10 seconds until the maximum is reached, then continue recording every 30 seconds until the temperature difference falls below 10% of the maximum Finally, plot the recorded values against time in seconds.
To determine the time constant, divide the maximum temperature difference by ten to obtain T 10 Next, analyze the plot of temperature difference versus time to measure the duration, in seconds, for the temperature difference to reach its peak and subsequently decrease to T 10 Ensure that this time constant does not exceed the specified limit.
The oven supplier must provide essential information including the temperature range that meets standard variation requirements, available ventilation rates, supply voltage range with maximum power consumption, maximum ambient temperature compliance, number of test chambers, dimensions of each chamber's exposure volume, test results as specified in clause 4, external dimensions, the mass of the empty oven, and recommendations for controlling the quality of ventilating air, such as filtration and dehumidification methods.
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7 Conditions d’utilisation et instructions pour le contrôle en service par les utilisateurs
Conditions d’utilisation
During operation, it is essential to maintain the ambient temperature and power supply voltage within the manufacturer's specified range to ensure the proper functioning of the oven Unless stated otherwise, the air renewal quality must be adequate to avoid significantly impacting the results Additionally, samples and supports should not occupy more than 25% of the cross-sectional area of the chamber in any plane, and no more than 50% of the longitudinal cross-sectional area in any plane.
In any chamber, only test tubes of the same composition should be placed, unless it has been proven that introducing test tubes from additional compounds with different compositions does not significantly affect the results This ensures that the total volume remains at 10%.
Il est recommandé que des dispositions rendent possibles un enregistrement continu de la température en un point donné, dans chacune des chambres.
Contrôle en service
Les essais suivants sur une étuve chargée d’éprouvettes doivent être réalisés immédiatement avant chaque essai de vieillissement.
These tests are designed to verify that the loaded oven meets the requirements of the current standard at the beginning of the aging test During the tests, the overall exposure temperature and temperature variation are measured.
To conduct the testing procedure outlined in sections 5.1.2.1 to 5.1.2.4, first, install a series of temperature sensors within the test chamber Next, adjust the oven temperature to the desired aging value Then, assess the overall exposure temperature and finally, evaluate the temperature variation.
La variation de température doit être maintenue dans les limites indiquées au tableau 1.
Si cela est le cas, noter la température moyenne globale comme étant la température du vieillissement et continuer avec le programme de vieillissement.
Si cela n’est pas le cas, déterminer si l’étuve est en défaut ou si la cause est consécutive au système de chargement des éprouvettes.
Eliminate the source of the difficulties and repeat the series of measures to ensure that the temperature variation meets the required standards Record the new overall average temperature as the aging temperature.
Répéter les mesures après 24 h La variation de la température à ce moment doit encore se situer dans les limites indiquées au tableau 1.
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7 Conditions of use and instructions for in-service monitoring by the user
To ensure optimal performance of the oven, it is essential to maintain the ambient temperature and supply voltage within the manufacturer's specified range The quality of the ventilating air must be adequate to avoid significantly impacting the results Additionally, specimens and supports should not exceed 25% of the cross-sectional area in any plane, 50% of the longitudinal cross-sectional area in any plane, or 10% of the total volume Furthermore, only specimens from a single compound should be placed in one chamber, unless it has been demonstrated that including specimens from other compounds with different compositions does not adversely affect the results.
It is recommended that facilities for making a continuous record of the temperature at one point in each chamber be made available.
The following tests on a specimen-loaded oven shall be made immediately before each ageing test.
These tests are conducted to ensure that the loaded oven complies with the specified standards at the start of the ageing test During the testing process, both the global exposure temperature and the temperature variation are assessed.
To conduct the temperature assessment, first, install a series of temperature sensors within the chamber Next, increase the oven temperature to the specified ageing level After reaching the target temperature, calculate the global average temperature and assess the temperature variation.
The temperature variation shall be within the limits given in table 1.
If this is the case, record the global average temperature as the ageing temperature and proceed with the ageing programme.
If this is not the case, determine whether the oven is faulty or if the cause is due to the system of specimen loading.
Eliminate the root cause of the issue and conduct the measurements again to ensure that the temperature fluctuations meet the specified criteria Document the updated global average temperature as the ageing temperature.
Repeat the measurements after 24 h The temperature variation at this time shall still be within the limits given in table 1.
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General
The oven shall be soundly constructed using suitable materials All electrical and other ancillary fittings shall be readily accessible for maintenance purposes.
The construction must include equipment that automatically shuts off the oven and ideally triggers an alarm if the temperature of the thermostatically controlled medium falls outside the permitted range or if there is a failure in the supply of ventilating air.
Specimen chambers
The ovens must feature a minimum of two open-topped, cylindrical chambers positioned vertically, each equipped with a well-sealing lid It is essential that the lid creates an effective seal, ensuring that the leakage of ventilating gas from the lid does not exceed 5% of the gas flow rate directed to the specimen chamber.
NOTE 1 Some types of 'O' ring seals have been found to be satisfactory.
Unless otherwise specified, the individual chambers shall have a minimum diameter of 35 mm and a minimum length of 200 mm.
The construction materials for the chambers, lids, and internal components must be free from copper, copper alloys, and any substances that could release interfering volatiles within the oven's temperature range, such as certain silicone resins.
The design shall be such as to permit the chambers to be easily cleaned after each test.
The chambers should be installed in a heat transfer medium that is controlled by a thermostat, such as a metal block, liquid bath, sand bath, saturated vapor bath, or an air circulating oven Typical design examples are illustrated in figures 1 and 2.
NOTE 2 The performance of air circulating ovens in this context is usually poorer than the alternative systems.
Ventilation
Each chamber shall be provided with a supply of continuously metered, filtered, pre-heated ventilating air, entering the chamber at one end and being exhausted through the other.
When specified in the purchase contract, provision shall be made for the use of ventilating gases other than air.
Ventilation rates in the range 5 to 20 changes per hour shall be available.
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The incoming air must be directed towards a cylindrical wall of the chamber to create a turbulent flow within the cell, while the overall design should minimize air recirculation within each chamber To prevent cross-contamination of volatile components, the air renewal from one chamber must not come into contact with the samples from another chamber It is advisable for the air extracted from the chambers to be released into the external atmosphere, with precautions in place to ensure that volatile substances emitted from aged samples do not pose health or environmental risks.
It is essential to ensure the proper purity of the incoming compressed air to minimize its impact on the results If test outcomes are affected by impurities in the ventilation environment, such as water vapor, this must be monitored and documented.
4.4 Dispositions pour le montage des éprouvettes
Measures must be taken to support and/or suspend the test tubes, ensuring they are placed in each chamber without contact with one another or the chamber walls The test tubes and supports should not occupy more than 25% of the cross-sectional area of the chamber in any plane, exceed 50% of the longitudinal cross-sectional area in any plane, or occupy more than 10% of the actual working volume of the chamber.
La température dans le volume d’exposition doit être contrôlable dans les limites données en 5.1.1.
5 Méthodes d’essai et exigences de performance
Le volume d’exposition doit être constitué d’au moins 70 % du volume central de la chambre avec la variation maximale autorisée, indiquée dans le tableau 1.
Tableau 1 – Variation de température maximale autorisée
Gamme de températures Variation de température Dérive maximale autorisée de la température moyenne globale au cours d’une période de 5 jours °C K K
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The design of the chamber should ensure that incoming air is directed towards the cylindrical wall to create turbulent flow, minimizing air recirculation within each chamber To prevent cross-contamination of volatile components, the ventilating air from one chamber must not interact with specimens in other chambers It is advisable to vent exhaust air from the chambers to the outside atmosphere, while implementing measures to protect health and the environment from harmful volatiles produced by ageing specimens.
To ensure accurate test results, it is essential to maintain the purity of incoming ventilating air Any impurities, such as water vapor, that may affect the results must be controlled and documented.
Specimen mounting arrangements
Each chamber must be equipped to support, suspend, and position specimens without allowing them to touch one another or the chamber walls The combined area of the specimens and their supports should not exceed 25% of the cross-sectional area in any plane, 50% of the longitudinal cross-sectional area in any plane, or 10% of the effective working volume of the chamber.
Temperature control
The temperature in the exposure volume shall be controllable to the limits given in 5.1.1.
5 Test methods and performance requirements
Temperature variation
Requirement
The exposure volume shall constitute at least the central 70 % of the volume of the chamber with the maximum allowable temperature variation given in table 1.
Table 1 – Maximum allowable temperature variation
Temperature range Temperature variation Maximum allowable drift in global average temperature over 5-day period ° C K K
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5.1.2.1 On doit placer une série de capteurs de température d'un diamètre maximal de 3 mm dans le volume d’exposition de la chambre en essai, en s’assurant a) qu’un capteur est situé à 10 mm au plus du centre de la chambre; b) qu’un capteur est situé au sommet du volume en essai et qu’un autre capteur est situé au fond du volume, diamétralement opposé au capteur du haut; c) que six capteurs complộmentaires sont situộs de faỗon à ờtre approximativement équidistants de la ligne centrale et les uns des autres.
To minimize heat conduction from the temperature sensor, it is essential to ensure that there is a sufficient length of connection wire inside the oven Additionally, the wires should be routed close to or through the temperature-controlled environment externally.
If calibrated temperature sensors such as platinum resistance thermometers or thermocouples are unavailable, it is possible to use thermocouples made from the same wire coils, provided they yield temperature readings that do not vary by more than 0.2 K when placed adjacent to each other in the test chamber set to its maximum operating temperature.
5.1.2.2 Porter la température de l’étuve à sa température de fonctionnement maximale et la laisser se stabiliser Mesurer à 0,1 K près la température donnée par les capteurs, un certain nombre de fois au cours d’une période d’environ 3 h pour identifier un éventuel comportement cyclique et permettre de déterminer les températures maximale, minimale et moyenne de chacun des thermocouples pendant la période de mesure.
NOTE 1 A partir des lectures faites, il est facilement possible de calculer la fluctuation de température en un point et la différence de température à n’importe quel moment.
NOTE 2 L’utilisation d’un enregistreur de données est judicieuse pour cette opération.
5.1.2.3 Calculer à 0,1 K près la moyenne des neuf températures moyennes et noter cette valeur comme étant la température moyenne globale de la chambre.
5.1.2.4 Calculer la différence entre la température la plus élevée et la température la plus basse, déterminées conformément à 5.1.2.2, et noter cette valeur comme étant la variation de température Celle-ci ne doit pas excéder les valeurs données au tableau 1.
5.1.2.5 Maintenir l’étuve aux mêmes températures pendant cinq jours, c’est-à-dire 120 h.
Measure the temperature variation once daily, in accordance with sections 5.1.2.2 and 5.1.2.4 This variation must not exceed the values specified in Table 1 The overall average temperature of the chamber should be determined as per section 5.1.2.3 during each of the six measurement periods Additionally, the maximum variation over a five-day period must not exceed the values listed in Table 1.
Si cela est spécifié dans le contrat d’achat, la constante de temps ne doit pas excéder une valeur spécifiée.
NOTE Ce paramètre est important uniquement si l’étuve est utilisée pour des conditionnements thermiques de courte durée (essai de choc thermique).
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Test method
5.1.2.1 A series of 3 mm maximum diameter temperature sensors shall be placed in the exposure volume of the chamber under investigation, ensuring that a) one sensor is located within 10 mm of the centre of the chamber; b) one sensor is located at the top of the volume under consideration and another sensor is located at the bottom of the volume, diametrically opposite to the top sensor; c) six additional sensors are located so as to be approximately equidistant from the centre line and from each other.
To minimize heat conduction from the temperature sensor, it is essential to maintain a sufficient length of connecting wire within the oven and to route the external wires close to or through the thermostatically controlled medium.
If calibrated temperature sensors like platinum resistance thermometers or thermocouples are unavailable, thermocouples made from the same spools of wire can be utilized However, it is essential that these thermocouples, when placed next to each other in the testing chamber at the maximum operating temperature, show temperature readings that differ by no more than 0.2 K.
5.1.2.2 Raise the oven to its maximum operating temperature and allow it to stabilize.
Monitor the temperature of the sensors to an accuracy of 0.1 K multiple times over a span of about 3 hours This process will help identify any cyclic patterns and enable the calculation of the maximum, minimum, and average temperatures for each thermocouple during the measurement period.
NOTE 1 From these readings, the temperature fluctuation at one point and the temperature difference at any one time can be easily calculated.
NOTE 2 Use of a data logger is advisable for this operation.
5.1.2.3 Calculate the average of the nine mean temperatures to 0,1 K and record this value as the global average temperature of the chamber.
5.1.2.4 Calculate the difference between the highest maximum temperature and the lowest minimum temperature determined according to 5.1.2.2 and record this as the temperature variation This shall not exceed the values given in table 1.
5.1.2.5 Maintain the oven at the same set temperature for five days, i.e 120 h Measure the temperature variation once a day according to 5.1.2.2 and 5.1.2.4 This shall not exceed the values given in table 1 The global average temperature of the chamber shall be determined according to 5.1.2.3 during each of the six measuring periods The maximum variation over the five-day period shall not exceed the values given in table 1.
Time constant
Requirement
When specified in the purchase contract the time constant shall not exceed a specified value.
NOTE This parameter is only of importance when the oven is used for short term thermal conditioning (thermal shock testing).
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Utiliser une éprouvette normalisée faite d’un cylindre solide en laiton dont le diamètre est de
10 mm ± 0,1 mm et la longueur de 55 mm ± 0,1 mm, auquel a été soudée une liaison avec un thermocouple différentiel.
Set the oven to 200 °C or its maximum usable temperature, whichever is lower, and allow it to stabilize Let the standardized test specimen acclimate to room temperature for about 1 hour.
Follow the manufacturer's instructions to open the chamber and quickly suspend the standardized test tube vertically near the geometric center of the oven using a heat-resistant cord with a diameter not exceeding 0.25 mm Ensure that the free end of the thermocouple is suspended as far away as possible from the standardized test tube without contacting the chamber walls and remains within the actual working volume Keep the chamber open for a total of 60 seconds ± 2 seconds, then replace the chamber cover Record the temperature difference every 10 seconds until reaching the maximum.
Continuer l’enregistrement toutes les 30 s jusqu’à ce que la différence de température chute de
10 % par rapport à son maximum, et reporter les valeurs enregistrées en fonction du temps exprimé en secondes.
Diviser la différence maximale de température par dix et enregistrer cette valeur comme étant T 10
Based on the curve recording temperature differences over time, note the time required, in seconds, to transition from the maximum recorded temperature to T 10 This value represents the time constant and must not exceed the specified limit.
The oven supplier must provide essential information, including the temperature range that meets the standard's variation requirements, available air renewal options, and the power supply voltage range along with maximum consumption Additionally, the maximum ambient temperature for compliance, the number of test chambers, and the exposure volume dimensions for each chamber must be specified The supplier should also include test results as outlined in Article 4, external dimensions, the total mass of the empty oven, and recommendations for quality control methods for air renewal, such as filtering, dehumidification, and appropriate measurement techniques.
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Test procedure
Provide a standard specimen consisting of a solid brass cylinder 10 mm ± 0,1 mm in diameter and 55 mm ± 0,1 mm long to which one junction of a differential thermocouple has been soldered.
Preheat the oven to 200 °C or its maximum designed temperature, whichever is lower, and let it stabilize Meanwhile, allow the standard specimen to acclimate to ambient temperature for about 1 hour.
To conduct the experiment, follow the manufacturer's instructions by opening the chamber and suspending the standard specimen vertically at the oven's geometric center using a heat-resistant cord no thicker than 0.25 mm Ensure the thermocouple's free end is positioned away from the specimen and does not touch the chamber walls, remaining within the effective working volume Keep the chamber open for 60 seconds ± 2 seconds before closing it Record the temperature difference every 10 seconds until the maximum is reached, then continue recording every 30 seconds until the temperature difference falls below 10% of the maximum Finally, plot the recorded values against time in seconds.
To determine the time constant, divide the maximum temperature difference by ten to obtain T 10 Next, measure the time in seconds from the temperature difference versus time plot, noting how long it takes for the temperature difference to reach its maximum and then decrease to T 10 Ensure that this time constant does not exceed the specified limit.
The oven supplier must provide essential information including the temperature range that meets standard variation requirements, available ventilation rates, supply voltage range with maximum power consumption, and the maximum ambient temperature for compliance Additionally, details on the number of test chambers, dimensions of each chamber's exposure volume, test results as specified in clause 4, external dimensions, the mass of the empty oven, and recommendations for controlling air quality, such as filtration and dehumidification methods, are also required.
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7 Conditions d’utilisation et instructions pour le contrôle en service par les utilisateurs
7.1 Conditions d’utilisation a) Pendant l’utilisation, la température ambiante et la tension d’alimentation doivent être maintenues dans la gamme stipulée par le fabricant pour obtenir un fonctionnement correct de l’étuve. b) Sauf spécification contraire, la qualité du renouvellement de l’air doit être suffisante pour ne pas affecter significativement les résultats. c) Les éprouvettes et les supports ne doivent pas occuper plus de 25 % de la surface de la section transversale de la chambre dans un plan quelconque, pas plus de 50 % de la surface de la section transversale longitudinale dans un plan quelconque et pas plus de
In any chamber, only test tubes of the same composition should be placed, unless it has been proven that introducing test tubes from additional compounds with different compositions does not significantly affect the results.
Il est recommandé que des dispositions rendent possibles un enregistrement continu de la température en un point donné, dans chacune des chambres.
Les essais suivants sur une étuve chargée d’éprouvettes doivent être réalisés immédiatement avant chaque essai de vieillissement.
These tests are designed to verify that the loaded oven meets the requirements of the current standard at the beginning of the aging test During the tests, the overall exposure temperature and temperature variation are measured.
To conduct the testing procedure outlined in sections 5.1.2.1 to 5.1.2.4, first, install a series of temperature sensors within the test chamber Next, adjust the oven temperature to the desired aging value Then, assess the overall exposure temperature and finally, evaluate the temperature variation.
La variation de température doit être maintenue dans les limites indiquées au tableau 1.
Si cela est le cas, noter la température moyenne globale comme étant la température du vieillissement et continuer avec le programme de vieillissement.
Si cela n’est pas le cas, déterminer si l’étuve est en défaut ou si la cause est consécutive au système de chargement des éprouvettes.
Eliminate the source of the difficulties and repeat the series of measures to ensure that the temperature variation meets the required standards Record the new overall average temperature as the aging temperature.
Répéter les mesures après 24 h La variation de la température à ce moment doit encore se situer dans les limites indiquées au tableau 1.
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7 Conditions of use and instructions for in-service monitoring by the user
Conditions of use
To ensure optimal performance of the oven, it is essential to maintain the ambient temperature and supply voltage within the manufacturer's specified range The quality of the ventilating air must be adequate to avoid significantly impacting the results, unless stated otherwise Additionally, the specimens and supports should not exceed 25% of the cross-sectional area of the chamber in any plane, 50% of the longitudinal cross-sectional area in any plane, or 10% of the total volume Furthermore, only specimens from a single compound should be placed in one chamber, unless it has been demonstrated that including specimens from other compounds with different compositions does not significantly affect the results.
It is recommended that facilities for making a continuous record of the temperature at one point in each chamber be made available.
In-service monitoring
The following tests on a specimen-loaded oven shall be made immediately before each ageing test.
These tests are conducted to ensure that the loaded oven complies with the specified standards at the start of the ageing test During the testing process, both the global exposure temperature and the temperature variation are assessed.
To conduct the temperature assessment, first, install a series of temperature sensors within the chamber Next, increase the oven temperature to the specified ageing level After reaching the desired temperature, calculate the global average temperature and assess the temperature variation.
The temperature variation shall be within the limits given in table 1.
If this is the case, record the global average temperature as the ageing temperature and proceed with the ageing programme.
If this is not the case, determine whether the oven is faulty or if the cause is due to the system of specimen loading.
Eliminate the root cause of the issue and conduct the measurements again to ensure that the temperature fluctuations meet the specified criteria Document the updated global average temperature as the ageing temperature.
Repeat the measurements after 24 h The temperature variation at this time shall still be within the limits given in table 1.
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Le laboratoire d’essai doit au moins indiquer les informations suivantes :
– la variation de la température pour la température globale d’exposition,
– des informations sur la qualité du gaz de ventilation,
– toutes les données relatives au vieillissement comme spécifié par la CEI 60216.
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Report
The testing laboratory shall provide at least the following information:
– the temperature variation at the global exposure temperature,
– details of the quality of the ventilating gas,
– any ageing data in the format specified in IEC 60216.
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Sortie de gaz de ventilation Joint
Entrée des gas de ventilation Tête de dispersion de l'air
Vide rempli d'un matériau isolant thermique
Limite du volume de travail effectif
Appareil de maintien de l'éprouvette
Niveau du liquide de chauffage
Figure 1 – Cellule pour une étuve à chambres multiples utilisant un liquide comme support de chauffage
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Ventilating gas inlet Air dispersion
Void filled with head thermal insulation
Boundary of effective working volume
Level of liquid heating medium
Figure 1 – Cell of a multi-chamber oven using a liquid heating medium
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Entrée des gaz de ventilation
Sortie des gaz de ventilation
Appareil de maintien de l'éprouvette
Corps de la cellule chauffée
Limite du volume de travail effectif
Tête de dispersion de l'air
Figure 2 – Cellule pour une étuve à chambres multiples utilisant un support solide pour le chauffage
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Boundary of effective working volume
Figure 2 – Cell of a multi-chamber oven using a solid heating medium
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