Iec 60216 4 2 2000

NORME INTERNATIONALE CEI IEC INTERNATIONAL STANDARD 60216 4 2 Première édition First edition 2000 07 Matériaux isolants électriques – Propriétés d''''endurance thermique – Partie 4 2 Etuves de vieillisse[.]

Généralités

L’ộtuve doit ờtre construite de faỗon robuste, en utilisant des matộriaux appropriộs conỗus pour un fonctionnement continu dans toute la gamme des températures autorisées.

Toutes les adaptations électriques et auxiliaires doivent être facilement accessibles, pour des raisons de maintenance.

Caractéristiques mécaniques

Etuve

Les matériaux de construction de l’étuve et les aménagements intérieurs doivent être choisis de manière à ne pas influencer les propriétés des éprouvettes.

NOTE 1 Les alliages d’aluminium et d’acier inoxydable ont été considérés comme adaptés dans beaucoup de cas.

It is essential to ensure that the door leading to the oven is equipped with an effective seal, and that all sealing materials used do not affect the properties of the samples.

La chambre d’exposition doit être munie d’un moyen de ventilation de l’air préchauffé qui doit être orienté de manière à produire des turbulences dans la chambre.

NOTE 2 Quand cela est possible, il convient que l’alimentation en air soit en permanence filtrée, mesurée et contrôlée.

NOTE 3 Des amộnagements d’ộvents d’entrộe et de sortie munis d’amortisseurs conỗus pour permettre le rộglage du taux de ventilation ont été considérés comme satisfaisants.

Boợte isotherme

The manufacturing process must ensure that the temperature variation and temperature difference requirements are met in over 50% of the interior space of the insulated box when installed in any of the ovens Additionally, the ventilation rate must comply with the specified requirements.

NOTE Les boợtes constituộes à partir de feuilles d’alliage d’aluminium ont ộtộ considộrộes comme satisfaisantes.

LICENSED TO MECON Limited - RANCHI/BANGALORE FOR INTERNAL USE AT THIS LOCATION ONLY, SUPPLIED BY BOOK SUPPLY BUREAU.

3.10 iso-box metal box with a close-fitting door, mounted in the oven chamber and used in preference as the exposure chamber

3.11 ventilation continuous passage of pre-heated air through the exposure chamber

3.12 temperature deviation calculated difference in the exposure temperature from the intended value due to the combination of the temperature difference, temperature fluctuation and the error in the measurement of temperature

3.13 halving interval difference between two exposure temperatures which causes the halving of the heat ageing period required to arrive at a certain agreed level of property change of the material under test (see IEC 60216-1)

The oven system shall be soundly constructed of suitable materials designed for continuous operation over the whole of the allowable temperature range.

All electrical and other ancillary fittings shall be readily accessible for maintenance purposes.

The materials of construction of the oven chamber and the interior fittings shall be so chosen as to not influence the properties of the specimens.

NOTE 1 Aluminium alloys and stainless steel have been found suitable in many cases.

It is crucial to ensure that the oven chamber door has an effective seal, and that the gasket materials used do not affect the properties of the specimens.

The exposure chamber shall be provided with a supply of preheated ventilating air which shall be directed in such a manner as to produce turbulence throughout the chamber.

NOTE 2 Wherever possible, the supply should be continuously filtered, metered and monitored.

NOTE 3 Inlet and outlet vent fittings with dampers designed to allow adjustment of the rate of ventilation have been found to be satisfactory.

The construction must ensure that temperature fluctuations and differences are maintained in over 50% of the iso-box's interior when installed in any selected oven Additionally, the ventilation rate must meet specified requirements.

NOTE Boxes made from aluminium alloy sheet have been found to be satisfactory.

La boợte isotherme doit ờtre munie d’une porte fermant hermộtiquement sans aucun joint d’étanchéité.

Tout air entrant dans l’ộtuve comme air de ventilation doit passer par la boợte isotherme de manière à réaliser des turbulences.

Commande de température et indicateurs

The thermal container, also known as an insulated box, must be equipped with at least two temperature sensors (labeled 1 and 2) Prior to installation, sensors 1 and 2 should be calibrated against a suitable standard (sensor 3) to ensure a maximum measurement uncertainty of ±0.5 K It is essential to record the reading differences between the two sensors as the temperature varies.

Le capteur 3 doit avoir une incertitude maximale égale à ±0,1 K.

Le capteur de température 1 doit être relié à un appareil de mesure placé de manière adaptée et utilisé pour indiquer en permanence la température de la chambre.

NOTE 1 L’appareil de lecture permet également une identification précoce d’un quelconque mauvais fonctionnement du système.

The temperature sensor 2 should be positioned as close as possible to the location where the samples will be placed Its position must be clearly defined and reproducible, and it can be removed after the measurements are taken.

An independent sensor can be utilized to monitor temperature, with its installation left to the manufacturer's discretion The control system must maintain a drift of less than 1 K per year.

NOTE 2 Les capteurs peuvent être d’un type quelconque, satisfaisant aux exigences (par exemple thermomètre rempli de liquide, thermomètre résistance).

Thermocouples are less precise than liquid-filled thermometers and resistance systems, making them unsuitable for temperature measurements However, they are considered appropriate for measuring temperature differences.

Quand on utilise des thermomètres remplis de liquide, on doit faire attention de s’assurer que la profondeur d’immersion utilisée est la même que celle lors du calibrage.

The oven must be equipped with an independent overheating control device that operates separately from the main temperature control system This device should disconnect the electric heaters if the actual temperature exceeds a predefined threshold Additionally, the system must ensure that a warning light is activated when the overheating device is in operation, and the heaters should not automatically restart once the oven temperature falls below the set value; instead, a manual reset is required after the warning light has been turned off.

Si, dans la pratique, on s’attend à ce que les éprouvettes et les supports occupent plus de

25 % du volume d’exposition, il convient que le fabricant et le fournisseur se mettent d’accord avec l’utilisateur sur le fait d’utiliser des charges anormales pendant la détermination des performances.

The iso-box shall have a door which shall be close-fitting without any sealing gasket.

All air that enters the oven as ventilating air shall pass through the iso-box in such a manner as to produce turbulence.

4.3 Temperature control and indicator systems

The oven chamber, also known as an iso-box, must be equipped with at least two temperature sensors, labeled 1 and 2 Prior to installation, these sensors should be calibrated against a reliable standard, referred to as sensor 3, ensuring a maximum measurement uncertainty of ±0.5 K Additionally, the temperature readings from both sensors must be documented to analyze their differences.

Sensor 3 shall have a maximum uncertainty of ±0,1 K.

Temperature sensor 1 shall be connected to a readout, mounted in a convenient manner, and used to indicate the chamber temperature on a continuous basis.

NOTE 1 The readout also allows early identification of any malfunction in the system.

Temperature sensor 2 should be installed near the test specimens for accurate readings Its positioning must be clearly defined and consistent for reproducibility The sensor can be removed after the measurements are completed.

An independent temperature sensor can be utilized, with its placement determined by the manufacturer The control system is required to maintain a drift rate of under 1 K per year.

NOTE 2 The sensors may be of any type that meets the requirements (for example liquid-filled thermometer, resistance thermometer).

Thermocouples are generally less precise than filled thermometers and resistance systems, making them unsuitable for accurate temperature measurement However, they can be effectively used for measuring temperature differences.

Where liquid-filled thermometers are used, care shall be taken to ensure that the immersion depth in use is the same as that used during calibration.

The oven must include an independent excess temperature control device that automatically shuts off the electrical heaters if the temperature exceeds a predetermined limit Additionally, this system will activate a warning light when the excess temperature device is triggered Once the oven temperature falls below the set value, the heaters will not restart automatically; instead, a manual restart is required after the warning light is turned off.

When test specimens and supports are anticipated to exceed 25% of the exposure volume, it is essential for the manufacturer and supplier to collaborate with the user to determine the necessity of using dummy loads during performance assessments.

Températures

It should be possible to control the temperature of the display volume within the specified limits for temperature difference and fluctuations throughout the range declared by the manufacturer.

Différence maximale de température

Au sein du volume d’exposition, la différence de température ne doit pas excéder ±0,5 K.

Fluctuation maximale de la température

Au sein du volume d’exposition, la fluctuation de température ne doit pas excéder ±0,5 K.

Ecart maximal de la température

Au sein du volume d’exposition, l'écart de la température ne doit pas excéder ±2 K.

Type et taux de ventilation

Des taux compris entre 5 et 20 renouvellements par heure doivent être rendus possibles dans la chambre d’exposition de manière à réaliser les turbulences.

On doit faire attention de s’assurer de la pureté adéquate de l’air entrant afin de minimiser les influences sur la tenue au vieillissement.

Quand cela est spécifié dans le contrat d’achat, des précautions doivent être prises en ce qui concerne l’utilisation de gaz de ventilation autres que l’air.

Volume d’exposition

The exposure volume must be adequate to accommodate the samples, and it should not be less than 50% of the chamber's volume of the oven or the insulated box if one is used.

NOTE L’expérience a montré qu’un volume d’exposition de 35 l à 70 l est généralement considéré comme satisfaisant.

6 Méthode d’essai et mode opératoire

The dimensions and shape of the exposure volume are determined based on experimental results regarding temperature differences and fluctuations This is achieved by utilizing various locations with a series of temperature sensors for three specific temperatures, along with the expected ventilation rates These temperatures include the minimum and maximum operating temperatures of the oven, as well as a midpoint temperature, such as 50 °C, 175 °C, and 300 °C.

During performance measurements, it is essential to monitor the ambient temperature and the power supply voltages applied to the oven These parameters must remain within the manufacturer's specified range to ensure proper oven performance.

Température et paramètres correspondants

Considérations pratiques

La température de la chambre de l’étuve et, finalement, du volume d’exposition doit être déterminée en utilisant le capteur de température numéro 2.

The temperature of the exposure volume can be precisely controlled within the manufacturer's specified limits for both temperature difference and fluctuation across the entire claimed range.

Within the exposure volume, the temperature difference shall not exceed ±0,5 K.

Within the exposure volume, the temperature fluctuation shall not exceed ±0,5 K.

Within the exposure volume, the temperature deviation shall not exceed ±2 K.

5.5 Type and rate of ventilation

Rates in the range 5 to 20 changes per hour shall be made available in the exposure chamber in such a manner as to produce turbulence.

Consideration shall be given to ensure adequate purity of the incoming air to minimize influences on the ageing behaviour.

When specified in the purchase contract, provision shall be made for the use of ventilating gases other than air.

The exposure volume must be adequate to fit the test specimens, ensuring it is at least 50% of the oven chamber's volume or the iso-box's volume if applicable.

NOTE Experience has shown that an exposure volume of 35 l to 70 l is generally found to be convenient.

The exposure volume's size and shape are established through experimental measurements of temperature differences and fluctuations, utilizing various placements of temperature sensors These measurements are taken at three key temperatures: the minimum and maximum operational temperatures of the oven, along with a midpoint temperature, such as 50 °C, 175 °C, and 300 °C, reflecting the expected ventilation use rates.

To ensure optimal performance of the oven, it is essential to maintain the ambient temperature and supply voltages within the manufacturer's specified range during all performance measurements.

The temperature of the oven chamber and, finally, of the exposure volume shall be determined using temperature sensor number 2.

To determine temperature differences and fluctuations, install a series of temperature sensors (maximum diameter of 5 mm) within the oven chamber or the insulated box, if one is used, ensuring proper placement for accurate readings.

– qu’un capteur est situé à moins de 25 mm du centre de la chambre;

– qu’un capteur supplémentaire est situé à une distance de (50 ± 10) mm des parois en chacun des huit coins de la chambre.

To minimize heat conduction from temperature sensors, it is essential to ensure that the connecting wires inside the oven are of adequate length Additionally, these wires should be thermally insulated externally and maintained in conditions that are largely free from drafts.

To assess temperature differences and fluctuations without calibrated temperature sensors, thermocouples made from the same wire coil and prepared similarly can be utilized It is essential that these thermocouples yield temperature values with a difference not exceeding 0.2 K when positioned adjacent to each other in the test chamber, under maximum operating temperature conditions.

Régler le niveau de ventilation au minimum indiqué par les fabricants.

Laisser la température de la chambre se stabiliser.

Measure the temperature of each sensor with an accuracy of 0.1 K multiple times over a period of approximately 3 hours This approach will facilitate the identification of any cyclical behavior and enable the determination of the maximum, minimum, and average temperatures for each temperature sensor during the measurement period.

Calculs

Check the data and calculate the maximum temperature difference recorded over a 3-hour period for each of the nine sensors Identify the largest of these differences and record it as the temperature fluctuation for the first day.

Check the data and calculate the maximum temperature difference in the exposure chamber at any point during the three-hour period Record this difference as the temperature variation from the first day.

Résultats

Si les résultats satisfont aux exigences de différence et de fluctuation de température, répéter chaque jour les mesures pendant cinq jours.

Répéter les calculs pour le reste des données et noter les différences de température des jours

2, 3, 4 et 5 Choisir la plus grande de ces différences de température du jour et la noter comme étant la différence de température (de l’étuve) δT 1.

Repeat the calculations for the remaining data and record the temperature fluctuations for days 2, 3, 4, and 5 Identify the maximum temperature fluctuation for each day and document it as the temperature fluctuation (of the incubator) δT 2.

If the measured temperature differences and fluctuations within the oven meet the specified requirements, the oven can be deemed compliant for that particular chamber temperature and ventilation level The exposure volume is defined as the space between the eight corner sensors.

For the determination of temperature difference and temperature fluctuation, place a series of temperature sensors (maximum diameter, 5 mm) in the oven chamber (iso-box, when used) under investigation, ensuring that

– one sensor is located within 25 mm of the centre of the chamber;

– one additional sensor is located (50 ± 10) mm distance from the walls in each of the eight corners of the chamber.

To minimize heat conduction from temperature sensors, it is essential to use a sufficient length of connecting wire within the oven and ensure that the external wires are thermally insulated and kept in draught-free conditions.

To assess temperature differences and fluctuations without calibrated sensors, thermocouples from the same spool and prepared identically can be utilized It is essential that these thermocouples, when positioned next to each other in the testing chamber at maximum operating temperature, yield temperature readings that do not vary by more than 0.2 K.

Set the level of ventilation at the manufacturer's stated minimum.

Allow the temperature of the chamber to stabilize.

To accurately assess the performance of individual sensors, measure their temperatures to an accuracy of 0.1 K multiple times over a span of approximately 3 hours This approach will help identify any cyclic behavior and enable the calculation of the maximum, minimum, and average temperatures for each sensor during the measurement period.

Analyze the data to determine the maximum temperature difference recorded by each of the nine sensors over a 3-hour period Identify the largest temperature fluctuation among these differences and label it as the "day 1 temperature fluctuation."

Inspect the data and calculate the maximum temperature difference present in the exposure chamber at any one time during the period of 3 h Record that as the "day 1 temperature difference".

If the results meet the requirements for temperature difference and fluctuation, repeat the measurements every day for a period of five days.

Calculate the temperature differences for days 2, 3, 4, and 5, and identify the largest difference among these days Record this maximum temperature difference as the oven temperature difference, denoted as δT 1.

Repeat the calculations for the remainder of the data and record the day 2, 3, 4 and 5 temperature fluctuations Select the maximum day temperature fluctuation and record as the

The oven is considered compliant with the specified requirements if the measured temperature difference and fluctuation levels meet the established criteria for the specific chamber temperature and ventilation level The exposure volume refers to the area encompassed by the eight corner sensors.

Si les résultats ne satisfont pas aux exigences, replacer les capteurs à environ 25 mm plus loin des parois et répéter les essais et les calculs.

If the measured temperature differences and fluctuations within the oven meet the specified requirements, the oven can be deemed compliant for that particular chamber temperature and ventilation level The exposure volume is defined as the space between the eight repositioned corner sensors.

Répéter les mesures avec les deux autres températures de chambre en utilisant les taux de ventilation appropriés pour déterminer le volume d’exposition de ces températures.

The temperature difference, denoted as \$\delta T_d\$, must be calculated according to Annex B, utilizing the computed value of the temperature difference and temperature fluctuation This difference is derived from the readings of temperature sensors 1 and 2, based on the initial calibration, and referenced against the exposure temperature indicated by sensor 1 during long-term thermal aging experiments.

Taux de ventilation

On peut utiliser n’importe quelle méthode adéquate pour déterminer le taux de ventilation si l’on n’utilise pas une alimentation dont le débit a été mesuré.

Annex A provides a procedure based on measuring the increase in electrical consumption required to maintain the temperature in the oven chamber above the required level with vents open, compared to the consumption needed to keep the exposure chamber at the same temperature with vents closed.

L’alimentation en air et le système d’aspiration doivent être réglés jusqu’à ce que le taux de ventilation mesuré satisfasse aux exigences.

NOTE L’utilisation d’amortisseurs facilite ces réglages.

Le fournisseur de l'étuve doit au moins donner les informations suivantes:

– gamme des tensions d'alimentation pour laquelle l’étuve est conforme à cette norme;

– gamme des températures ambiantes dans laquelle l’étuve est conforme à cette norme;

– masse de l’étuve complète (vide) et dimensions extérieures;

– gamme des températures du volume d’exposition dans laquelle les exigences de différence de température et de fluctuation de température sont conformes à cette norme;

– gamme des taux de ventilation disponibles;

– résultats des essais décrits à l’article 6.

If the results do not meet the requirements, reposition the sensors approximately 25 mm further from the walls and repeat the tests and calculations.

The oven is considered compliant with the specified requirements if the measured temperature difference and fluctuation levels meet the established criteria for the specific chamber temperature and ventilation The exposure volume refers to the area encompassed by the eight repositioned corner sensors.

Repeat the measurements at the other two chamber temperatures using appropriate ventilation rates to determine the exposure volume for these temperatures.

The temperature deviation \$\delta T_d\$ will be determined according to annex B, utilizing the calculated temperature difference and fluctuation, along with the initial calibration readings from temperature sensors 1 and 2 This calculation will also reference the exposure temperature indicated by sensor 1 during long-term heat aging experiments.

Any adequate method may be used to determine the rate of ventilation if a metered supply is not used.

A method outlined in annex A measures the increase in power consumption needed to keep the oven chamber at a consistent temperature with the vents open, compared to the power required to maintain the same temperature with the vents closed in the exposure chamber.

The air supply and exhaust system shall be adjusted until the measured rate of ventilation meets the requirements.

NOTE The provision of dampers facilitates these adjustments.

The supplier of the oven shall provide at least the following information:

– range of supply voltage over which the oven conforms with this standard;

– range of ambient temperature over which the oven conforms with this standard;

– mass of the complete (empty) oven and external dimensions;

– range of exposure volume temperatures over which the requirements for temperature difference and temperature fluctuation conform with this standard;

– range of available ventilation rates;

– results of the tests described in clause 6.

8 Conditions d’utilisation et instructions pour le contrôle en service par l’utilisateur

Conditions d’utilisation

During operation, it is essential to monitor the ambient temperature and power supply voltages within the manufacturer's specified range to ensure the proper functioning of the oven Unless stated otherwise, the air ventilation quality must be adequate to avoid significantly impacting the results In cases where test outcomes are affected by impurities in the ventilation medium, such as water vapor, this should be monitored and noted Additionally, when multiple aging ovens are used in the same area, precautions must be taken to prevent cross-contamination of volatile components, ensuring that the ventilation air from one oven does not come into contact with samples in another oven.

It is recommended that exhaust gases from each oven be vented directly to the outside atmosphere Precautions must be taken to ensure that volatile products from the aging process do not pose a risk to health or the environment If significant levels of volatile and/or harmful substances are released during aging, careful attention should be given to product standards to apply the most appropriate ventilation rate During temperature exposure, specimens should not be stored outside the exposure volume and must only contact the supports without touching each other.

Mode opératoire

Before long-term thermal aging, the temperature in the oven chamber (or in the insulated box, if used) must be set to the nominal exposure temperature as measured by temperature sensor 2, which should be positioned as close as possible to where the test specimens will be located The sensor's placement must be clearly defined and reproducible.

Si l’on utilise des thermomètres remplis de liquide, on doit faire attention à s’assurer que la profondeur d’immersion utilisée est la même que celle utilisée pendant le calibrage.

Contrôle en service

Les essais suivants doivent être réalisés sur une étuve chargée, immédiatement avant chaque essai de vieillissement.

These tests are conducted to verify that the oven meets the specifications at the beginning of the aging test During these assessments, the overall exposure temperature and the temperature variation are determined.

Following the general operating procedure outlined in section 6.1, a series of eight temperature sensors should be placed inside, but around the periphery of the mounted specimens within the evaluation exposure volume The oven should then be heated to the planned temperature and allowed to stabilize After approximately 3 hours, the overall average temperature, assumed to be the initial exposure temperature, and the temperature variation should be determined using data from the eight sensors in addition to that from sensor 2.

8 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 voltages within the manufacturer's specified range The quality of the ventilating air must also be adequate to avoid significantly impacting test results; any impurities, such as water vapor, should be monitored and reported Additionally, when multiple ageing ovens are in operation nearby, precautions must be taken to prevent cross-contamination of volatile components, ensuring that the ventilating air from one oven does not interact with specimens in another.

It is essential to vent the exhaust from each oven directly to the outside atmosphere to ensure safety Precautions must be implemented to protect health and the environment from harmful volatiles produced during the ageing process When significant levels of volatiles or degradation products are released, the product standard should specify an appropriate ventilation rate Additionally, during temperature exposure, test specimens must remain within the exposure volume, only making contact with the supports and not with each other.

Before conducting long-term heat aging, the oven chamber temperature, or that of the iso-box if applicable, must be set to the specified exposure temperature This temperature should be accurately measured by temperature sensor 2, which needs to be positioned as close as possible to the test specimens The placement of the sensor must be clearly defined and consistently reproducible.

The following test on a loaded oven shall be made immediately before each ageing test.

These tests are conducted to ensure that the loaded oven complies with the specifications at the start of the ageing test They involve determining the global exposure temperature and the temperature variation.

To evaluate the exposure volume, first, position eight temperature sensors near the periphery of the mounted specimens Next, increase the oven temperature to the desired level and allow it to stabilize Finally, measure the global average temperature, considered the initial exposure temperature, and assess the temperature variation over approximately three hours using data from all eight sensors, including sensor 2.

If the results do not meet the requirements, complete the aging program and rearrange the setups used for the specimen assembly, or adjust the equipment until confirmation is achieved by repeating the tests.

To obtain a more accurate exposure temperature than what was determined in the previous test, it is essential to calculate a long-term average of the temperature measured using sensor 2.

If the results fail to meet the specified requirements, discontinue the ageing program and reorganize the test specimen mounting arrangements or adjust the equipment Repeat the tests until conformance is confirmed.

To achieve a more accurate estimation of exposure temperature beyond the initial test, it is essential to compute a long-term average using the measurements obtained from sensor 2.

Méthode d'essai pour déterminer le taux de ventilation

Toute autre méthode que celle décrite ci-dessous ayant une précision équivalente peut être utilisée.

Etuve étanche

L'étuve doit être correctement étanche, y compris les entrées par les évents, la porte, les passages du capteur de température, de l'extracteur ou du ventilateur général, s'ils existent.

A wattmeter with an accuracy of ±1 Wh or better should be connected to the power source of the oven, which must be powered on It is essential to select and adjust an appropriate temperature control.

Après stabilisation de l'étuve en température, les mesures suivantes doivent être effectuées:

The ambient temperature at a point located 2 meters from any significant heat source should be measured at least 1 meter away from any solid objects and approximately at the same height as the inlet vent of the oven.

– consommation d'énergie électrique pendant une période d'au moins 1 h avec une précision sur la mesure de l'énergie de ±2 Wh, et sur le temps de ±3 s.

Etuve ventilée

After removing all joints, the dimensions of the inlet vent's damping must be assessed to achieve the required ventilation rate Once the oven temperature stabilizes, the electrical energy consumption should be measured as outlined in Article A.1 over the same duration.

Calcul

Le taux de ventilation est calculé avec la formule suivante :

N est le taux de ventilation;

P1 represents the average power consumed, measured in watts, for the non-ventilated oven It is calculated by dividing the energy consumption E1, expressed in watt-hours, obtained from the wattmeter reading by the duration of the test, measured in hours.

P2 represents the average power consumption in watts for the ventilated oven It is calculated by dividing the energy consumption E2, measured in watt-hours from the wattmeter reading, by the duration of the test in hours.

V o est le volume de la chambre d’exposition, en litres;

T a est la température ambiante moyenne, en kelvins;

T est la température d’exposition, en kelvins.

Test method to determine the rate of ventilation

Any other method of equivalent accuracy may be used.

Ensure the oven is properly sealed, including all vent ports, the door, the temperature sensor port, and the blower shaft or complete blower if necessary Connect a watt-hour meter with an accuracy of ±1 Wh or better to the oven's power supply line and energize the oven Select and set an appropriate control temperature for optimal performance.

After the oven temperature has stabilized, the following measurements shall be taken:

– room temperature at a point 2 m distance from any significant thermal source, at least 1 m from any solid object and at about the same level as that of the oven inlet vent;

– electrical energy consumed over a period of time of at least 1 h to within ±2 Wh, with the corresponding time measured to within ±3 s.

Once all seals are removed, the damper size for the inlet vent must be calculated to achieve the necessary ventilation rate Additionally, after the oven temperature stabilizes, the electrical energy consumption should be assessed as outlined in clause A.1 for the corresponding time period.

The rate of ventilation is calculated by the following equation:

N is the rate of ventilation;

The mean power consumption, denoted as P 1 in watts, of the non-ventilated oven is calculated by dividing the energy consumption E 1, measured in watt-hours from the watt-hour meter reading, by the duration of the test in hours.

The mean power consumption, denoted as P 2 in watts, of the ventilated oven is calculated by dividing the energy consumption E 2, measured in watt-hours from the watt-hour meter reading, by the duration of the test in hours.

Vo is the volume of the exposure chamber, in litres;

Ta is the mean ambient temperature, in kelvins;

T is the exposure temperature, in kelvins.

NOTE Le calcul est basé sur les hypothèses suivantes.

– La densité de l’air à la température ambiante est d Ta = d 20 T 20 /T a en kg/l avec T 20 = 293 K

– Dans le calcul, une valeur moyenne est utilisée pour la capacité spécifique thermique à 180 °C, qui est c p = 1,022 × 1 000 in J/kg K

– La masse totale du flux d'air au cours de la période d'essai est

M = 3 600 (E 2 – E 1 ) / c p (T – T a ) (kg) si le flux d'air est chauffé de T a à T et si E 1 et E 2 sont les énergies consommées en Wh obtenues à partir des lectures faites sur le wattmètre

– Le volume total du flux d'air au cours de la période d'essai est

– Le volume par heure est

– Le taux de ventilation est

NOTE The calculation is based on the following assumptions.

– The density of air at ambient temperature is d Ta = d 20 T 20 /T a in kg/l with T 20 = 293 K

– For calculation purposes a mean value is used for the specific thermal capacity at 180 °C, which is c p = 1,022 × 1 000 (J/kg K)

– The total mass of air flow during the test period is

M = 3 600 (E 2 – E 1 ) / c p (T – T a ) (kg) when the air flow is heated from T a to T and E 1 and E 2 the energy consumption in Wh derived from the Watt-hour meter readings

– The total volume of air flow during the test period is

– The volume per hour is

– The rate of ventilation is

Exemples de calcul de l'écart de température

Erreur de mesure

General

The oven system shall be soundly constructed of suitable materials designed for continuous operation over the whole of the allowable temperature range.

All electrical and other ancillary fittings shall be readily accessible for maintenance purposes.

Mechanical requirements

The materials of construction of the oven chamber and the interior fittings shall be so chosen as to not influence the properties of the specimens.

NOTE 1 Aluminium alloys and stainless steel have been found suitable in many cases.

It is crucial to ensure that the oven chamber door is equipped with an effective seal, and that the gasket materials utilized do not affect the characteristics of the specimens.

The exposure chamber shall be provided with a supply of preheated ventilating air which shall be directed in such a manner as to produce turbulence throughout the chamber.

NOTE 2 Wherever possible, the supply should be continuously filtered, metered and monitored.

NOTE 3 Inlet and outlet vent fittings with dampers designed to allow adjustment of the rate of ventilation have been found to be satisfactory.

The construction must ensure that temperature fluctuations and differences are maintained in over 50% of the iso-box's interior when installed in any selected oven, while also adhering to the specified ventilation requirements.

NOTE Boxes made from aluminium alloy sheet have been found to be satisfactory.

La boợte isotherme doit ờtre munie d’une porte fermant hermộtiquement sans aucun joint d’étanchéité.

Tout air entrant dans l’ộtuve comme air de ventilation doit passer par la boợte isotherme de manière à réaliser des turbulences.

4.3 Commande de température et indicateurs

The insulated container, also known as a thermos, must be equipped with at least two temperature sensors (labeled 1 and 2) Prior to installation, sensors 1 and 2 should be calibrated against a suitable standard (sensor 3) to ensure a maximum measurement uncertainty of ±0.5 K It is essential to record the reading differences between the two sensors as the temperature varies.

Le capteur 3 doit avoir une incertitude maximale égale à ±0,1 K.

Le capteur de température 1 doit être relié à un appareil de mesure placé de manière adaptée et utilisé pour indiquer en permanence la température de la chambre.

NOTE 1 L’appareil de lecture permet également une identification précoce d’un quelconque mauvais fonctionnement du système.

The temperature sensor 2 should be positioned as close as possible to the location where the samples will be placed Its position must be clearly defined and reproducible, and it can be removed after the measurements are taken.

An independent sensor can be utilized to monitor temperature, with its installation left to the manufacturer's discretion The control system must maintain a drift of less than 1 K per year.

NOTE 2 Les capteurs peuvent être d’un type quelconque, satisfaisant aux exigences (par exemple thermomètre rempli de liquide, thermomètre résistance).

NOTE 3 Comme la performance des thermocouples est moins précise que celle des thermomètres remplis de liquide et des systèmes à résistance, leur utilisation n’est pas recommandée pour les mesures de température, même si on les considère comme adaptés aux mesures de différence de températures.

Quand on utilise des thermomètres remplis de liquide, on doit faire attention de s’assurer que la profondeur d’immersion utilisée est la même que celle lors du calibrage.

The oven must be equipped with an independent overheating control device that operates separately from the main temperature control system This device should disconnect the electric heaters if the actual temperature exceeds a predefined threshold Additionally, the system must ensure that a warning light is activated when the overheating device is in operation, and the heaters should not automatically restart once the oven temperature falls below the set value; instead, a manual reset is required after the warning light has been turned off.

Si, dans la pratique, on s’attend à ce que les éprouvettes et les supports occupent plus de

25 % du volume d’exposition, il convient que le fabricant et le fournisseur se mettent d’accord avec l’utilisateur sur le fait d’utiliser des charges anormales pendant la détermination des performances.

The iso-box shall have a door which shall be close-fitting without any sealing gasket.

All air that enters the oven as ventilating air shall pass through the iso-box in such a manner as to produce turbulence.

Temperature control and indicator systems

The oven chamber, also known as an iso-box, must be equipped with at least two temperature sensors, designated as sensor 1 and sensor 2 Prior to installation, these sensors should be calibrated against a reliable standard, referred to as sensor 3, ensuring a maximum measurement uncertainty of ±0.5 K Additionally, the temperature readings from both sensors must be documented to track their differences.

Sensor 3 shall have a maximum uncertainty of ±0,1 K.

Temperature sensor 1 shall be connected to a readout, mounted in a convenient manner, and used to indicate the chamber temperature on a continuous basis.

NOTE 1 The readout also allows early identification of any malfunction in the system.

Temperature sensor 2 should be installed near the test specimens for accurate measurements Its positioning must be clearly defined and consistent, and it can be removed after the testing is complete.

An independent temperature sensor can be utilized for control, with its placement determined by the manufacturer The control system is required to maintain a drift rate of under 1 K per year.

NOTE 2 The sensors may be of any type that meets the requirements (for example liquid-filled thermometer, resistance thermometer).

NOTE 3 Since the performance of thermocouples is less precise than filled thermometers and resistance systems, their use is not recommended for the measurement of temperature, although they may be found suitable for the measurement of temperature difference.

The oven must include an independent excess temperature control device that automatically shuts off the electrical heaters if the temperature exceeds a predetermined limit Additionally, this system will activate a warning light when the excess temperature device is triggered Once the oven temperature falls below the set value, the heaters will not restart automatically; instead, a manual restart is required after the warning light is turned off.

When test specimens and supports are expected to exceed 25% of the exposure volume, it is essential for the manufacturer and supplier to consult with the user regarding the potential use of dummy loads during performance assessments.

It should be possible to control the temperature of the display volume within the specified limits for temperature difference and fluctuations throughout the range declared by the manufacturer.

Au sein du volume d’exposition, la différence de température ne doit pas excéder ±0,5 K.

5.3 Fluctuation maximale de la température

Au sein du volume d’exposition, la fluctuation de température ne doit pas excéder ±0,5 K.

5.4 Ecart maximal de la température

Au sein du volume d’exposition, l'écart de la température ne doit pas excéder ±2 K.

5.5 Type et taux de ventilation

Des taux compris entre 5 et 20 renouvellements par heure doivent être rendus possibles dans la chambre d’exposition de manière à réaliser les turbulences.

On doit faire attention de s’assurer de la pureté adéquate de l’air entrant afin de minimiser les influences sur la tenue au vieillissement.

Quand cela est spécifié dans le contrat d’achat, des précautions doivent être prises en ce qui concerne l’utilisation de gaz de ventilation autres que l’air.

The exposure volume must be adequate to accommodate the samples and should not be less than 50% of the chamber's volume or the volume of the insulated box if one is used.

NOTE L’expérience a montré qu’un volume d’exposition de 35 l à 70 l est généralement considéré comme satisfaisant.

6 Méthode d’essai et mode opératoire

The dimensions and shape of the exposure volume are determined based on experimental results regarding temperature differences and fluctuations This is achieved by utilizing various locations with a series of temperature sensors for three specific temperatures, along with the expected ventilation rates These temperatures include the minimum and maximum operating temperatures of the oven, as well as the midpoint temperature, for instance, 50 °C, 175 °C, and 300 °C.

During performance measurements, it is essential to monitor the ambient temperature and the power supply voltages applied to the oven This ensures that they remain within the manufacturer's specified range, which is crucial for the oven to function correctly.

La température de la chambre de l’étuve et, finalement, du volume d’exposition doit être déterminée en utilisant le capteur de température numéro 2.

Temperatures

The temperature of the exposure volume can be precisely controlled within the manufacturer's specified limits for both temperature difference and fluctuation across the entire claimed range.

Maximum temperature difference

Within the exposure volume, the temperature difference shall not exceed ±0,5 K.

Maximum temperature fluctuation

Within the exposure volume, the temperature fluctuation shall not exceed ±0,5 K.

Maximum temperature deviation

Within the exposure volume, the temperature deviation shall not exceed ±2 K.

Type and rate of ventilation

Rates in the range 5 to 20 changes per hour shall be made available in the exposure chamber in such a manner as to produce turbulence.

Consideration shall be given to ensure adequate purity of the incoming air to minimize influences on the ageing behaviour.

When specified in the purchase contract, provision shall be made for the use of ventilating gases other than air.

Exposure volume

The exposure volume must be adequate to hold the test specimens, ensuring it is at least 50% of the oven chamber's volume or the iso-box's volume if applicable.

NOTE Experience has shown that an exposure volume of 35 l to 70 l is generally found to be convenient.

The exposure volume's size and shape are established through experimental measurements of temperature differences and fluctuations, utilizing various placements of temperature sensors These measurements are conducted at three key temperatures: the minimum and maximum operational temperatures of the oven, along with a midpoint temperature, such as 50 °C, 175 °C, and 300 °C, reflecting the expected ventilation use rates.

To ensure optimal performance of the oven, it is essential to maintain the ambient temperature and supply voltages within the manufacturer's specified range during all performance measurements.

Temperature and related parameters

The temperature of the oven chamber and, finally, of the exposure volume shall be determined using temperature sensor number 2.

To determine temperature differences and fluctuations, a series of temperature sensors (maximum diameter of 5 mm) should be placed in the oven chamber or in an insulated box if one is used, ensuring proper placement for accurate readings.

– qu’un capteur est situé à moins de 25 mm du centre de la chambre;

– qu’un capteur supplémentaire est situé à une distance de (50 ± 10) mm des parois en chacun des huit coins de la chambre.

To minimize heat conduction from temperature sensors, it is essential to ensure that the connecting wires inside the oven are of adequate length Additionally, these wires should be thermally insulated externally and maintained in conditions that are largely free from drafts.

To assess temperature differences and fluctuations without calibrated temperature sensors, thermocouples made from the same wire coil and prepared similarly can be utilized It is essential that these thermocouples yield temperature values with a difference not exceeding 0.2 K when positioned adjacent to each other in the test chamber, under maximum operating temperature conditions.

Régler le niveau de ventilation au minimum indiqué par les fabricants.

Laisser la température de la chambre se stabiliser.

Measure the temperature of each sensor with an accuracy of 0.1 K multiple times over a period of approximately 3 hours This approach will facilitate the identification of any cyclical behavior and enable the determination of the maximum, minimum, and average temperatures for each temperature sensor during the measurement period.

Check the data and calculate the maximum temperature difference recorded over a 3-hour period for each of the nine sensors Identify the largest of these differences and record it as the temperature fluctuation for the first day.

Check the data and calculate the maximum temperature difference in the exposure chamber at any point during the three-hour period Record this difference as the temperature difference for the first day.

Si les résultats satisfont aux exigences de différence et de fluctuation de température, répéter chaque jour les mesures pendant cinq jours.

Répéter les calculs pour le reste des données et noter les différences de température des jours

2, 3, 4 et 5 Choisir la plus grande de ces différences de température du jour et la noter comme étant la différence de température (de l’étuve) δT 1.

Repeat the calculations for the remaining data and record the temperature fluctuations for days 2, 3, 4, and 5 Identify the maximum temperature fluctuation for each day and document it as the temperature fluctuation (of the incubator) δT 2.

If the measured levels of temperature difference and fluctuations within the oven meet the specified requirements, the oven can be deemed compliant for that particular room temperature and ventilation level The exposure volume is defined as the space between the eight corner sensors.

For the determination of temperature difference and temperature fluctuation, place a series of temperature sensors (maximum diameter, 5 mm) in the oven chamber (iso-box, when used) under investigation, ensuring that

– one sensor is located within 25 mm of the centre of the chamber;

– one additional sensor is located (50 ± 10) mm distance from the walls in each of the eight corners of the chamber.

To minimize heat conduction from temperature sensors, it is essential to use a sufficient length of connecting wire within the oven, while ensuring that the external wires are thermally insulated and kept in draught-free conditions.

To assess temperature differences and fluctuations without calibrated sensors, thermocouples from the same spool and prepared identically can be utilized These thermocouples must be placed next to each other in the testing chamber at the maximum operating temperature, ensuring their readings do not vary by more than 0.2 K.