Iec 60814 1997

NORME INTERNATIONALE CEI IEC INTERNATIONAL STANDARD 60814 Deuxième édition Second edition 1997 08 Isolants liquides – Cartons et papiers imprégnés d''''huile – Détermination de la teneur en eau par titra[.]

Domaine d'application

This international standard outlines methods for determining the water content in liquid insulators and oil-impregnated cellulosic insulators using the Karl Fischer coulometric titration method.

La méthode de l’article 2 s'applique aux teneurs en eau supérieures à 2 mg/kg de liquides ayant une viscosité inférieure à 100 mm 2 /s à 40 °C.

La méthode d'essai de l’article 3, dans laquelle l'eau est extraite par courant d'azote, est la méthode préférentielle pour les liquides isolants de viscosité supérieure à 100 mm 2 /s.

L’article 4 décrit des méthodes pour déterminer la teneur en eau des papiers et cartons imprégnés d'huile, dans une gamme comprise entre 0,1 % et 20 % en masse.

Champ d'application

Cette méthode s'applique aux teneurs en eau supérieures à 2 mg/kg des liquides ayant une viscosité allant jusqu'à 100 mm 2 /s à 40 °C Les données relatives à la fidélité et indiquées en

2.10 s'appliquent uniquement aux liquides neufs.

1 Pour les liquides en service, la justesse de la méthode peut être affectée par la présence de contaminants et de produits de dégradation.

The method is particularly suitable for hydrocarbons and liquid esters For other liquids, especially silicone fluids, it is essential to use reagents that are free of methanol.

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

INSULATING LIQUIDS – OIL-IMPREGNATED PAPER AND PRESSBOARD –

DETERMINATION OF WATER BY AUTOMATIC COULOMETRIC

This International Standard describes methods for the determination of water in insulating liquids and in oil-impregnated cellulosic insulation with coulometrically generated Karl Fischer reagent.

The method in clause 2 is applicable to water concentrations above 2 mg/kg in liquids having viscosity of less than 100 mm 2 /s at 40 °C.

The test method in clause 3, where water is extracted by means of a nitrogen stream, is the preferred method for insulating liquids of viscosity higher than 100 mm 2 /s.

Clause 4 describes methods for the determination of water content in oil-impregnated paper and pressboard over the range 0,1 % to 20 % by mass.

This International Standard references several normative documents that contain essential provisions At the time of publication, the listed editions were current However, all normative documents may be revised, and parties involved in agreements based on this Standard are encouraged to consider using the latest editions of the referenced documents.

IEC and ISO maintain registers of currently valid International Standards.

IEC 60475: 1974, Method of sampling liquid dielectrics

IEC 60567: 1992, Guide for the sampling of gases and of oil from oil-filled electrical equipment and for the analysis of free and dissolved gases

ISO 595-1: 1986, Reusable all-glass or metal-and-glass syringes for medical use – Part 1:

Design, performance requirements and tests

2 Direct titration for low viscosity liquids

This method is applicable to water concentrations above 2 mg/kg in liquids having viscosity up to 100 mm 2 /s at 40 °C The precision data given in 2.10 apply only to new liquids.

1 For liquids in service, the accuracy of the method may be affected by the presence of contaminants and degradation products.

2 The method has been designed to be particularly suitable to hydrocarbon and ester liquids With other liquids, particularly silicone fluids, methanol free reagents must be used.

Réactions chimiques

The Karl Fischer titration involves complex reactions primarily between water and iodine, facilitated by sulfur dioxide, an organic base, and an alcohol in an organic solvent Initially, the Karl Fischer reagent contained pyridine and methanol, and the reactions can be expressed as follows:

C 5 H 5 N.SO 3 + CH3OH → C 5 H 5 NH.SO 4 CH 3 (2)

D'autres associations base-alcool sont possibles et peuvent être nécessaires pour des titrages dans certains liquides isolants.

In Karl Fischer coulometric titration, the sample is mixed with a base-alcohol solution containing iodide ions and sulfur dioxide Iodine is generated through electrolysis and reacts with water, as illustrated in reactions (1) and (2) According to Faraday's law, the amount of iodine produced is directly proportional to the quantity of electricity consumed in the reaction.

Et comme le montre la réaction (1), une mole d'iode réagit stoechiométriquement avec une mole d'eau, de sorte que 1 mg d'eau correspond à 10,72 C (quantité d'électricité en coulombs).

Se fondant sur ce principe, il est possible de calculer la quantité d'eau directement à partir de la quantité d'électricité (en coulombs) consommée par l'électrolyse.

Appareillage

The titration vessel acts as an electrolysis cell with two compartments divided by a porous diaphragm The anodic compartment holds a mixture of the reagent, solvent, and sample (anodic solution), while the cathodic compartment (generator set) contains the anhydrous reagent (cathodic solution) Electrodes for electrolysis are positioned on either side of the diaphragm.

NOTE – Des titrimètres sans diaphragme poreux peuvent être utilisés.

Iodine generated by electrolysis reacts with water in a manner similar to the reactions described by Karl Fischer The endpoint of this reaction is detected using a pair of platinum electrodes immersed in the anodic solution At the conclusion of the titration, excess iodine depolarizes the platinum electrodes, altering the current-to-voltage ratio, which triggers the endpoint indicator and halts the current integrator.

L'intégrateur de courant somme le courant absorbé au cours de l'électrolyse, calcule la teneur en eau conformément à la loi de Faraday, et finalement l'affiche en microgrammes d'eau.

Les titrimètres coulométriques de Karl Fischer du commerce utilisent des circuits brevetés.

La description suivante d'un des principes acceptables d'appareil est donnée uniquement à titre d'illustration.

Le schéma fonctionnel représenté en figure 1 décrit l'appareil et comprend les éléments ci-dessous.

Karl Fischer titration involves complex reactions primarily between water and iodine, sulfur dioxide, an organic base, and an alcohol in an organic solvent The initial Karl Fischer reagent utilized pyridine and methanol, and these reactions can be represented by specific chemical equations.

Other base-alcohol combinations are possible and may be necessary for titrations on some insulating liquids.

Coulometric Karl Fischer titration involves mixing a sample with a base/alcohol solution containing iodide ions and sulfur dioxide Electrolytic generation of iodine occurs, which then reacts with water, following specific chemical reactions The amount of iodine produced is directly proportional to the quantity of electricity used, in accordance with Faraday's law.

One mole of iodine reacts with one mole of water, where 1 mg of water corresponds to 10.72 coulombs This relationship allows for the direct determination of water quantity based on the amount of electricity, measured in coulombs, needed for electrolysis.

The titration vessel is designed like an electrolysis cell, featuring two compartments linked by a porous diaphragm The anodic compartment holds a mixture of reagent, solvent, and sample, referred to as the anodic solution, while the cathodic compartment, known as the generator assembly, contains anhydrous reagent, termed the cathodic solution Electrolysis electrodes are positioned on either side of the diaphragm.

NOTE – Titrators without the porous diaphragm may be used.

Iodine produced through electrolysis reacts with water, akin to the Karl Fischer reactions The reaction's end-point is identified using platinum electrodes in the anodic solution When excess iodine is present, it depolarizes the electrodes, resulting in a change in the current/voltage ratio that triggers the end-point indicator and halts the current integrator.

The current integrator integrates the current consumed during the electrolysis, calculates the water equivalent according to Faraday's law, and finally displays it in micrograms of water.

Commercial coulometric Karl Fischer titrators use proprietary circuitry The following description of one suitable form of apparatus is given for illustrative purposes only.

The block diagram shown in figure 1 illustrates the apparatus and includes the components detailed below.

Figure 2 illustrates a suitable titration setup However, advancements in technology may lead to radically different designs that meet the technical requirements of the current standard.

L'appareil donné à titre d'exemple se compose:

– d'un récipient de titrage en verre à bride (a), muni d'un orifice d'injection (b) de l'échantillon, et d'un robinet de vidange (c) (facultatif);

– d'un couvercle en polytétrafluoroéthylène à bride (d) s'adaptant au vase de titrage Il possède trois ouvertures permettant d'y adapter les électrodes et le tube dessiccateur;

A combined electrolysis cell consists of a glass tube that is sealed at its lower end with a diaphragm This setup includes platinum electrodes positioned on either side of the diaphragm.

The diaphragm can serve as an ion exchange membrane, a sintered glass disc, a ceramic filter, or any other system that prevents the diffusion of two solutions while allowing the passage of current for electrolysis.

– d'électrodes de détection: une paire d'électrodes en platine pour mesure du potentiel ou du courant (f);

– d'un barreau agitateur recouvert de polytétrafluoréthylène (g);

– de tubes dessiccateurs (h) de l'humidité atmosphérique pour protéger le récipient de titrage et l'ensemble générateur;

Silicone rubber septa are used to seal the injection port Prior to use, it is advisable to make cross incisions in the septum to facilitate the use of square-tipped needles for sample injection It is important to replace the septa as needed to prevent air leaks, which can be indicated by excessive drift in the device.

A stabilized direct current or constant alternating current is applied to the detection electrodes, which consist of a pair of platinum measuring electrodes, allowing for the detection of the end of the reaction through changes in the polarized current or voltage.

2.3.2.3 Circuit de stabilisation du courant

Ce circuit commande l'électrolyse conformément au signal provenant du circuit de détection.

Alimentation en tension continue pour l'électrolyse.

Indique quand le point final a été atteint.

Mesure la quantité d'électricité consommée par la cellule d'électrolyse au cours du titrage, puis calcule et affiche la quantité d'eau correspondante, en microgrammes.

NOTE – Certains appareils ont des possibilités intégrées de calcul et affichent la teneur en eau pour une quantité particulière d'échantillon.

An electromagnetic stirrer operating at a constant and adequate speed is essential for ensuring proper dispersion Typically, the contents of the container will not be homogeneous, as liquid insulators are not completely miscible with reactive liquids.

A suitable titration vessel assembly is illustrated in figure 2, but advancements in instrument technology may lead to the emergence of significantly different designs that meet the technical standards The described apparatus includes:

– a flanged glass reaction vessel (a) with sample injection plug (b) and drain cock (c)

– a polytetrafluoroethylene lid (d), flanged to match the titration vessel, with three holes to receive the electrodes and drying tube;

– a generator assembly (combined electrolysis cell) (e) consisting of a glass tube closed at its lower end by a diaphragm and equipped with platinum electrodes on each side of the diaphragm;

NOTE – The diaphragm may consist of ion exchange membrane, fritted disc, ceramic filter or other system to prevent diffusion of both solutions, while allowing enough current for electrolysis.

– detector electrodes: dual platinum electrodes for measurement of potential or current (f);

– drying tubes (h) to protect the titration vessel and the generator assembly from atmospheric moisture;

Silicone rubber septa are essential for sealing the injection port, and it is advisable to make crosscuts in the septa prior to use This preparation allows for the effective use of blunt, square-ended needles during sample injection To maintain optimal performance and prevent air leakage, septa should be replaced as needed, especially if there are signs of excessive instrument drift.

Réactifs et produits auxiliaires

ATTENTION – Certains réactifs peuvent être nuisibles à la santé et doivent être manipulés avec prudence.

Ready-to-use reagents are commercially available; however, it is essential to ensure that one of these reagents is suitable for the specific type of device being used and the insulating liquid being tested.

Unwanted reactions can occur between methanol-based reagents and certain silicone compounds Additionally, similar reactions may take place with aldehydes, specific ketones, and certain conjugated unsaturated organic acids, which can be found in oils as products or contaminants from degradation In these instances, it is advisable to use methanol-free reagents.

NOTE – L'utilisation de solvants complémentaires ou de substitution peut être nécessaire pour certains liquides isolants.

Auxiliary products include a neutralization solution of methanol containing approximately 20 mg of water per cm³, and a desiccant such as anhydrous magnesium perchlorate or silica gel with an indicator A suitable lubricating grease should be based on polytetrafluoroethylene or fluorinated hydrocarbons, with commercially available options meeting these criteria deemed satisfactory For measuring and injecting samples, glass syringes of 10 cm³ and 5 cm³ conforming to ISO 595 are recommended, equipped with needles of appropriate length and diameter For general use, needles measuring 100 mm in length and 1 mm in diameter are considered adequate, with square-tipped needles preferred to minimize damage to the septum.

Préparation de l'appareil

Préparer et assembler l'appareil, introduire les réactifs et effectuer la procédure de stabilisation conformément aux instructions du fabricant.

Méthodes d'échantillonnage

Si les échantillons prélevés sont destinés à des essais autres que celui de la teneur en eau, l'analyse de la teneur en eau doit être effectuée en premier.

Pour les essais de routine, les méthodes d'échantillonnage décrites à l'article 2 et en 3.1 de la

CEI 60475 doivent être utilisées Les flacons de prélèvement doivent être séchés par chauffage dans une étuve à 115 °C ± 5 °C, pendant 16 h à 24 h.

To achieve better accuracy, especially when the water content is low, it is essential to follow the method outlined in Article 4 of IEC 60567 Sampling bottles should be prepared as specified in section 2.7.1 Syringes and needles must be disassembled, dried at 115 °C ± 5 °C for at least 8 hours, cooled in a desiccator containing anhydrous silica gel, and stored in the desiccator until use.

NOTE – La précision des mesures peut être sérieusement altérée par des prélèvements d'échantillons ôcompositesằ ou ômoyensằ, et ne sont donc pas recommandộs.

WARNING – Certain reagents may be detrimental to health and must be handled with proper care.

Prepared reagents are commercially available, but care is needed that the reagent is suitable for the particular type of instrument used and the insulating liquid under test.

Methanol-based reagents can react with certain silicone compounds, as well as with aldehydes, some ketones, and conjugated unsaturated organic acids found in oils as degradation products or contaminants Therefore, it is advisable to use reagents that are not based on methanol in these situations.

NOTE – Some insulating liquids may require the use of additional or alternative solvents.

2.4.2 Auxiliary materials a) Neutralizing solution, methanol containing approximately 20 mg water/cm 3 b) Desiccant, for example, anhydrous magnesium perchlorate or self-indicating silicagel. c) Lubricant grease: Polytetrafluoroethylene based or fluorinated hydrocarbon types.

Commercially available greases have proven to be effective for this application Additionally, glass syringes, specifically 10 cm³ and 5 cm³, should be used for sample measurement and introduction, adhering to ISO 595 standards, and equipped with appropriately sized needles.

100 mm and bore 1 mm have been found satisfactory for general use Blunt, square-ended needles are preferred, in order to minimize damage to the septa.

Prepare and assemble the apparatus, install the reagents and carry out the stabilization procedure in accordance with the manufacturer's instructions.

If samples taken are intended for additional tests to water content the water analysis shall be carried out first.

For routine tests, the sampling methods described in clause 2 and 3.1 of IEC 60475 shall be used Sample bottles shall be dried by heating in an oven for 16 h to 24 h at 115 °C ± 5 °C.

To enhance accuracy, especially in cases of low moisture content, the methods outlined in clause 4 of IEC 60567 should be followed Sample bottles must be prepared according to section 2.7.1, and syringes and needles need to be disassembled and dried for a minimum of 8 hours.

115 °C ± 5 °C, cooled in a desiccator with anhydrous silica gel, and kept in the desiccator until required.

NOTE – The accuracy of the determination can be adversely affected by the taking of composite or average samples, which is not recommended.

Water samples for analysis must never be exposed to direct sunlight It is essential to keep the samples in darkness from the moment of collection until analysis, and the time between collection and analysis should not exceed seven days.

Mode opératoire

a) Pour des échantillons prélevés en flacon

Clean and dry the glass syringes and appropriately sized needles in a well-ventilated oven at a temperature of 115 °C ± 5 °C, then allow them to cool in a desiccator Fill the syringe with the insulating liquid, ensuring the tip remains submerged Immediately seal the glass bottle Hold the syringe vertically with the needle facing up to eliminate any air bubbles Dispose of the syringe's contents, refill it, and weigh it to the nearest 0.1 g.

Pour les échantillons prélevés en seringue

Eliminer environ 2 cm 3 de liquide isolant afin de rincer l'aiguille Ensuite peser la seringue à 0,1 g près.

The volume to be extracted from the sample is dependent on its assumed water content For most types of insulating liquids, whether new or used, the optimal volume is determined to be 5 cm³ for water contents ranging from 2 mg/kg to 100 mg/kg Next, operate the device according to the manufacturer's instructions to initiate electrolysis, and quickly inject the appropriate volume of sample through the septum into the titration vessel, ensuring that the needle tip does not touch the reagent surface Finally, reweigh the syringe and record the mass \( M \) in grams of the injected volume.

Ensure that the oil is thoroughly mixed with the solvent, and maintain a constant agitator speed once the device has self-balanced or during titration At the end of the titration, record the amount of water displayed, expressed in micrograms (µg) Conduct a second determination by rinsing the syringe twice with the sample oil, refilling it, and weighing it as per the initial instructions, followed by the subsequent steps After multiple determinations, a significant amount of insulating liquid may accumulate in the titration container; remove the excess liquid according to the manufacturer's guidelines, which should also be followed regarding the relative levels of the anode and cathode reagents and the stabilization of the device.

Après plusieurs vidanges, il convient de remplacer la solution de titrage et la solution de l'ensemble générateur par des réactifs neufs, et de répéter le mode opératoire de stabilisation.

Calcul des résultats

teneur en eau (mg/kg) = m

M ó m est la quantitộ d'eau titrộe, en microgrammes (àg);

M est la masse de liquide isolant, en grammes (g).

Rapport

The water content of the insulating liquid sample is calculated as the average of two measurements, expressed in milligrams of water per kilogram (mg/kg) of insulating liquid, and rounded to the nearest whole number.

To ensure accurate water analysis, samples must be protected from direct sunlight at all times They should be stored in the dark from the moment of collection until analysis, and the interval between collection and analysis should not exceed seven days.

2.7 Procedure a) With samples which have been collected in bottles

Clean and dry a glass syringe and needle in a well-ventilated oven at 115 °C ± 5 °C, then cool in a desiccator Fill the syringe with insulating liquid, ensuring the needle tip remains below the liquid surface Immediately re-seal the glass bottle Hold the syringe vertically with the needle facing up to expel all air bubbles, then dispose of the syringe contents Refill the syringe and weigh it to the nearest 0.1 g.

With samples which have been collected in a syringe

Discharge approximately 2 cm 3 to flush out the needle and weigh the syringe to the nearest 0,1 g.

The optimal sample size for testing insulating liquids, both new and used, is typically 5 cm³, particularly when the moisture content ranges from 2 mg/kg to 100 mg/kg To initiate the electrolysis process, follow the manufacturer's instructions to operate the instrument controls, and promptly inject the appropriate amount of sample into the titration vessel through the septum, ensuring that the needle tip does not contact the reagent's surface.

Re-weigh the syringe and record the mass M, in grams, of sample injected.

To ensure accurate titration results, thoroughly mix the oil with the solvent and maintain a constant stirrer speed after the instrument has self-equilibrated Upon completion of the titration, record the quantity of water titrated in micrograms (µg) from the display For reliability, perform a duplicate determination by rinsing the syringe with the oil sample, refilling, and weighing as previously described After multiple determinations, excess insulating liquid may accumulate; follow the manufacturer's instructions to remove this liquid and ensure proper levels of the anode and cathode reagents, as well as re-stabilizing the instrument.

After several withdrawals, the titration vessel and generator electrode should be recharged with fresh solutions and the stabilization procedure repeated.

2.8 Calculation of the result water content (mg/kg) = m

M where m is the quantity of water titrated in micrograms (àg);

M is the mass of insulating liquid in grams (g).

The water content of the insulating liquid sample is the mean of the duplicate determinations, expressed to the nearest integer in milligrams per kilogram (mg/kg).

Fidélité

NOTE – Les valeurs de fidélité sont établies pour des isolants liquides à base d’hydrocarbures.

Tests conducted in duplicate by the same operator should be regarded as suspect at a 95% confidence level if they differ by more than 0.60 mg/kg, where x represents the average of the two measurements.

Lorsque deux laboratoires effectuent des essais sur les mêmes produits, ils doivent fournir deux résultats et la moyenne de ceux-ci.

Il convient de suspecter ces deux moyennes, à un niveau de confiance de 95 %, si elles diffèrent de plus de 1,50 x mg/kg, ó x est la moyenne des deux moyennes.

3 Mộthode d’entraợnement par ộvaporation pour les liquides à forte viscositộ

Champ d'application

Cette méthode est destinée à la détermination de l'eau dans les liquides isolants neufs de viscosité supérieure à 100 mm 2 /s à 40 °C Cette méthode s'applique principalement pour une teneur en eau supérieure à 2 mg/kg.

An alternative method for analyzing the water content in highly viscous liquids involves diluting them in an appropriate solvent, as outlined in Article 2 However, the reliability of this dilution method is influenced by the degree of dilution, the water content, and the viscosity of the selected solvent.

Esquisse de la méthode

Une quantité connue de liquide isolant est chauffée dans une étuve fixée à l'appareil de Karl

Fischer L'eau dộgagộe est entraợnộe complốtement par un courant d'azote sec dans le récipient de titrage ó s'effectue le titrage coulométrique.

Appareillage et réactifs

Le schéma de principe de l'appareil est illustré par la figure 3 et se compose des éléments suivants:

– titrimètre: coulomètre Karl Fischer automatique (voir 2.3);

– évaporateur: récipient en verre de capacité 100 ml, tube d’arrivée d’azote, de diamètre intérieur 1,25 mm (voir figure 4);

– dispositif de chauffage: dispositif en verre clair revêtu d'une couche mince conductrice transparente;

– gaz vecteur: azote, qualitộ du commerce, de teneur en eau infộrieure à 10 àl/l;

– déshydratant du gaz vecteur: une colonne de silicagel associée à deux colonnes d'anhydride phosphorique;

NOTE – Si des substances interférentes sont présentes, l’utilisation de réactifs appropriés dans le titrimètre est aussi importante que pour le titrage direct.

NOTE – Precision data have been established for hydrocarbon based insulating liquids.

Duplicate determinations performed by a single operator are deemed questionable at the 95% confidence level if the differences exceed 0.60 times the average of the duplicate measurements in mg/kg.

When two laboratories carry out tests on identical test material, each shall produce duplicate results and report their mean.

The two means should be considered suspect at the 95 % confidence level if they differ by more than 1,50 x mg/kg, where x is the average of the two means.

3 Evaporative stripping method for high viscosity liquids

This method is intended for measuring water content in unused insulating liquids with a viscosity exceeding 100 mm²/s at 40 °C, specifically for water concentrations greater than 2 mg/kg.

High viscosity liquids can be analyzed for water content using the method outlined in clause 2, provided they are diluted with an appropriate solvent It is important to note that the precision of the dilution procedure will depend on the extent of dilution, as well as the water content and viscosity of the selected solvent.

A known amount of the insulating liquid is heated in a closed vessel located next to the Karl

Fischer apparatus The water evolved is quantitatively transferred into the titration vessel by a stream of dry nitrogen gas where coulometric titration is performed.

The block diagram of the apparatus is illustrated in figure 3 and consists of the following items:

– titrator: automatic coulometric Karl Fischer (see 2.3);

– evaporator: glass vessel, 100 ml capacity; nitrogen inlet tube, 1,25 mm inside diameter

– heater: clear, transparent electro-conductive glass heater;

– temperature controller: automatic control, accuracy ± 2 °C;

– carrier gas: nitrogen gas, commercial grade, less than 10 àl/l water;

– desiccants for carrier gas: one silica gel column plus two phosphorus pentoxide columns;

NOTE – When interfering compounds are present, the need for suitable reagents in the titrator is of equal importance as for direct sample injection.

Mode opératoire

To initiate the Karl Fischer titrimeter, follow the specified procedure in section 2.5 Inject approximately 10 cm³ of base oil into the evaporator through the injector's septum, ensuring that the nitrogen inlet tube is submerged to facilitate gas bubbling The base oil can be the insulating liquid under test or any other oil that is miscible with the sample and has a similar viscosity to the oil being analyzed at the operating temperature Set the evaporator temperature to 130 °C ± 5 °C and allow it to stabilize at this temperature Purge the entire system with dry nitrogen at a flow rate of 50 cm³/min.

To completely dry the base oil, a flow rate of 200 cm³/min is required until the background noise level stabilizes at a low value Next, turn off the titration system switch and perform two blank tests, each lasting 10 minutes, on the initial base oil, following the specified steps If both blank tests yield similar results within 5 µg of water, record the average blank value (m₁) However, if the results differ by more than 5 µg of water, an additional drying of the base oil may be necessary Finally, introduce an appropriate amount of insulating liquid (M) into the evaporator using a syringe.

To ensure accurate measurement, use a syringe with a minimum inner diameter of 2 mm and weigh it before and after liquid injection to determine the exact sample mass For water content above 10 mg/kg, utilize a 10 g sample, while for water content below 10 mg/kg, a sample of 20 g ± 5 g is recommended Turn on the titration system or pause the titration for 10 minutes to allow moisture to escape from the evaporator and accumulate in the titration cell After this period, restart the titration and continue until the endpoint is reached Finally, read the amount of water titrated (m2) on the Karl Fischer apparatus.

If the water content exceeds 50 mg/kg and/or the sample mass is 10 g, incomplete evaporation may occur within the expected time In such cases, it is advisable to repeat steps e) to h) by extending the titration duration and reducing the oil quantity For certain types of titrators, achieving this goal may require selecting a sufficiently long waiting time Additionally, it is good practice to confirm stability conditions by performing another blank determination for 10 minutes If the obtained value matches the initial blank value m1 within 5 µg, no further titration is necessary Finally, conduct a second determination.

NOTE – Pour des essais de routine, les étapes d) et i) peuvent être omises et la durée de 10 min réduite à 1 min dans les étapes f) et g).

Calcul de la teneur en eau

Pour chaque détermination individuelle, calculer la teneur en eau comme suit: teneur en eau (mg/kg) = m m

2− 1 ó m 1 est la moyenne des essais à blanc, en microgrammes (àg); m 2 est la masse de l'eau titrộe au cours de l'analyse de l'ộchantillon, en microgrammes (àg);

M est la masse de l'échantillon, en grammes (g).

Rapport

La teneur en eau de l'échantillon de liquide isolant est exprimée par la moyenne des deux déterminations, arrondie à l'entier le plus proche, en milligrammes par kilogramme.

To perform the Karl Fischer titration, first operate the titrator according to the specified procedures Inject approximately 10 cm³ of base oil into the evaporator vessel to immerse the nitrogen inlet tube, ensuring proper gas bubbling Set the evaporator temperature to 130 °C ± 5 °C and stabilize it while purging the system with dry nitrogen at a flow rate of 50 cm³/min to 200 cm³/min until a low and stable background current is achieved Activate the titration switch and run two 10-minute blanks; if the results differ by more than 5 µg of water, further drying of the base oil may be necessary Introduce a suitable quantity of the insulating liquid into the evaporator using a syringe, weighing it before and after injection for accuracy For water contents greater than 10 mg/kg, use a 10 g sample; for lower contents, use a 20 g ± 5 g sample After a 10-minute pause to allow moisture accumulation, resume titration and record the water quantity titrated from the apparatus.

When water content exceeds 50 mg/kg or the sample mass is 10 g, complete evaporation may not occur, necessitating a repeat of the analysis with an extended titration delay or reduced oil amount For certain titrator designs, a longer delay time can facilitate this adjustment Additionally, it is advisable to verify stable operating conditions by performing another blank determination over a 10-minute period; if the result is within 5 µg of the initial blank value, further titration is unnecessary Finally, a duplicate determination should be conducted.

NOTE – In the case of routine tests steps d) and i) may be omitted and in steps f) and g) the 10 min may be reduced to 1 min.

For each individual determination, calculate the water content as follows: water content (mg/kg) = m m

2− 1 where m 1 is the average blank reading in micrograms (àg); m 2 is the mass of water titrated during sample analysis in micrograms (àg);

M is the mass of the sample in grams (g).

The water content of the insulating liquid sample is expressed as the average of duplicate determinations to the nearest integer in milligrams per kilogram.

4 Détermination de la teneur en eau dans les papiers et cartons imprégnés d’huile

Champ d'application

Ces méthodes s'appliquent au dosage de l'eau dans les matériaux isolants cellulosiques imprégnés d'huile Trois modes opératoires sont décrits:

– suivant la procédure de 4.2, l'eau est tout d'abord extraite avec du méthanol pur et le dosage est réalisé sur cet extrait;

– suivant la procédure de 4.3, l'extraction de l'eau est effectuée directement dans le récipient de titrage (voir note);

This procedure is applicable only to cellulosic materials with a thickness of approximately 1 mm or less For samples thicker than this, the oil impregnation prevents complete extraction within the standard titration time.

According to procedure 4.4, a sample of impregnated paper is heated in an oven connected to the Karl Fischer apparatus; the water vapor generated is fully transferred into the titration vessel using a stream of dry nitrogen.

Détermination de l'eau par extraction préalable au méthanol

ATTENTION – Certains réactifs peuvent être nuisibles à la santé et pour l'environnement et doivent être manipulés et éliminés avec prudence.

In addition to the reagents and products listed in section 2.4, the following items are required: a) analytical-grade methanol with an approximate water content of 0.05%; b) a suitable technical-grade solvent that is chlorine-free; c) magnesium chips.

The apparatus required includes a Karl Fischer coulometric titrator, as mentioned in section 2.3, along with a device for distilling methanol A dry methanol flask is necessary to collect the distilled methanol, which should be protected from atmospheric moisture using a desiccator tube This flask features a drain valve at the bottom and a spherical joint for fitting the extraction bulb The extraction bulb itself should be airtight, graduated, and have an approximate volume of 50 cm³ Additionally, metal tweezers are needed for handling.

It is essential to thoroughly clean all glassware and tweezers to remove any residues from previous samples using an appropriate detergent solution, soapy water, or a chlorinated organic solvent This should be followed by rinsing with hot water, then deionized water, and finally, after draining, with methanol The cleaned equipment should be dried overnight in an oven at 115 °C ± 5 °C and then cooled to room temperature in a desiccator.

4 Determination of water in oil-impregnated paper and pressboard

These methods apply to the determination of the water content in oil-impregnated cellulosic insulation materials Three procedures are described:

– with the procedure in 4.2, water is first extracted with absolute methanol and the determination carried out on the extract;

– with the procedure in 4.3, water extraction takes place directly in the titration vessel

This procedure is limited to cellulosic materials with a thickness of up to about 1 mm, as thicker oil-impregnated samples cannot be fully extracted within the standard determination time.

In accordance with procedure 4.4, a sample of impregnated paper is heated in an oven adjacent to the Karl Fischer apparatus, allowing the evolved water vapor to be quantitatively transferred into the titration vessel using a stream of dry nitrogen gas.

4.2 Determination of water after previous extraction with methanol

WARNING – Certain reagents may be detrimental to health and the environment and must be handled and disposed of with proper care.

In addition to the reagents and materials listed in 2.4, the following is required: a) methanol, analytical reagent grade, water content approximately 0,05 %; b) chlorine free suitable solvent, technical grade; c) magnesium turnings.

The apparatus required for the experiment includes a Coulometric Karl Fischer titrator, a methanol distilling apparatus, and a dried methanol container equipped with a drying tube to protect the distilled methanol from atmospheric exposure This container features a draining cock at its lower part and a spherical joint for adaptation to the extraction tube Additionally, graduated, gas-tight extraction tubes with an approximate capacity of 50 cm³ and metal tweezers are necessary for the procedure.

To ensure proper cleaning of glassware and metal tweezers, wash them thoroughly with a suitable detergent solution or soapy water, followed by rinsing with warm water and deionized water After draining, rinse with methanol and dry the cleaned items in an oven at 115 °C ± 5 °C overnight Finally, allow them to cool to room temperature in a desiccator.

To reduce the water content of methanol below 200 mg/kg, distill it in the presence of magnesium chips Collect the distilled methanol in a suitable container protected from atmospheric moisture using a desiccator filled with magnesium perchlorate, and measure the water content of the methanol, recording the value Additionally, use an extraction flask containing a paper sample, or introduce a paper sample into the extraction flask.

1 Choisir la masse du papier de telle sorte que la quantité d'eau à déterminer soit comprise entre 1 mg et 4 mg.

If the paper or cardboard is too thick, it is advisable to divide it into smaller pieces to enhance extraction, while ensuring that moisture exchange with the environment is avoided Next, adjust the extraction bulb to the flask containing anhydrous methanol, open the upper valve, and briefly apply a vacuum using a vacuum pump Then, using a suitable burette, introduce 1 cm³ to 10 cm³ of methanol.

To begin, close the upper tap and detach the extraction tube Next, repeat the procedure with a blank extraction bulb that does not contain paper, serving as a control test Shake both the bulb with the paper sample and the blank for 2 hours Prepare the Karl Fischer titration apparatus according to the specified procedures Connect the extraction bulb containing the sample to the titration vessel, introduce methanol into the solvent, and titrate until the endpoint is reached, recording the mass of water titrated (m2) Repeat this step with the blank tube and note the displayed reading (m1) Finally, remove the paper from the titration bulb, degrease it with a chlorine-free solvent, and dry it for at least 2 hours at 110 °C ± 5 °C Allow it to cool in a desiccator before weighing.

Noter la masse M, en grammes, du papier. j) Effectuer une deuxième détermination.

4.2.5 Calcul des résultats teneur en eau (% en masse) = (m 2 m 1 ) 10 4

− × − ó m 1 est la masse d'eau mesurộe lors de l'essai à blanc, en microgrammes (àg); m 2 est la masse d'eau mesurộe lors de l'essai avec ộchantillon, en microgrammes (àg);

M est la masse de l'échantillon de papier, en grammes (g).

La teneur en eau de l'isolant est exprimée par la moyenne des deux déterminations arrondie à 0,01 % La teneur en eau du méthanol utilisée doit être indiquée.

Dosage par titrage direct

Outre les réactifs et produits énumérés en 2.4, un solvant convenable, sans chlore, est nécessaire pour déshuiler les échantillons solides.

To reduce the water content of methanol below 200 mg/kg, distill it over magnesium turnings and collect the distilled methanol in a container safeguarded from atmospheric moisture using a drying tube filled with magnesium perchlorate Measure and document the water content of the methanol Next, place a paper sample into an extraction tube for further analysis.

1 Select the mass of the sample so that the amount of water to be measured is within 1 mg to 4 mg.

To enhance extraction efficiency, it is recommended to cut thick cellulosic material while preventing moisture exchange during the process Begin by connecting the extraction tube to the dry methanol container, opening the upper cock, and briefly connecting to the vacuum line to introduce 1 cm³ to 10 cm³ of methanol After closing the upper cock, disconnect the tube and repeat this step with a second tube for a blank test Shake both the sample and blank tubes for 2 hours Follow the specified procedures to operate the Karl Fisher titrator, attaching the sample tube to the titration vessel, transferring the methanol, and titrating to the endpoint to determine the mass of water titrated (m₂) Repeat this process with the blank tube to record the display reading (m₁) After removing the paper from the titration tube, degrease it with a chlorine-free solvent and dry it at 110 °C ± 5 °C for at least 2 hours Allow the paper sample to cool in a desiccator before weighing and recording its mass (M) in grams Finally, perform a duplicate determination for accuracy.

4.2.5 Calculation of the results water content (% by mass) = (m 2 m 1 ) 10 4

− × − where m 1 is the mass of water measured for blank titration, in micrograms (àg); m 2 is the mass of water measured in the sample titration, in micrograms (àg);

M is the mass of the paper sample, in grams (g).

The water content of the insulation is expressed as the average of duplicate measurements to the nearest 0,01 % The water content of the methanol used shall be quoted.

In addition to the reagents and materials listed in 2.4, a suitable chlorine-free solvent is required for degreasing the sample material.

4.3.2 Appareillage a) Titrimètre coulométrique de Karl Fischer indiqué en 2.3. b) Brucelles métalliques.

To initiate the Karl Fischer titrator, follow the procedures outlined in section 2.5 Quickly introduce the paper sample into the titration vessel using dry metal tweezers.

To ensure accurate moisture measurement, open the titration system switch or interrupt the titration for 15 to 25 minutes, as determined by the operator, to allow moisture transfer from the paper to the solvent After the extraction period, resume titration until the endpoint is reached Record the amount of water titrated (m2) using the Karl Fischer apparatus Additionally, conduct a blank test of the same duration to assess the moisture entering the system during the test, noting the titrated mass (m1) In some titrators, drift is continuously monitored and automatically deducted from the water mass reading, making the blank test potentially unnecessary, though maintaining stable operation throughout the titration is essential.

It is crucial to minimize the duration of the determination, which can be set by the operator based on experience and the type of sample being examined The optimal period may be established by repeatedly conducting the procedure with increasing extraction times until a consistent result is achieved To ensure reproducible results across a series of tests, the same extraction period should be used throughout After removing the paper from the titration container, de-oil it with solvent and dry it for at least 2 hours at 110 °C Allow the sample to cool in a desiccator before weighing it, and record the mass \( M \) in grams of the paper A second determination should then be performed.

4.3.4 Calcul des résultats teneur en eau (% en masse) = (m 2 m 1 ) 10 4

− × − ó m 1 est la masse d'eau mesurộe pour l'essai à blanc, en microgrammes (àg); m 2 est la masse d'eau mesurộe pour l'essai avec l’ộchantillon, en microgrammes (àg);

M est la masse de l'échantillon de papier, en grammes (g).

La teneur en eau de l'isolant est exprimée par la moyenne de deux déterminations arrondie à 0,01 % Le temps d'extraction doit être indiqué.

Scope

This International Standard describes methods for the determination of water in insulating liquids and in oil-impregnated cellulosic insulation with coulometrically generated Karl Fischer reagent.

The method in clause 2 is applicable to water concentrations above 2 mg/kg in liquids having viscosity of less than 100 mm 2 /s at 40 °C.

The test method in clause 3, where water is extracted by means of a nitrogen stream, is the preferred method for insulating liquids of viscosity higher than 100 mm 2 /s.

Clause 4 describes methods for the determination of water content in oil-impregnated paper and pressboard over the range 0,1 % to 20 % by mass.

Normative references

This International Standard references several normative documents that contain essential provisions At the time of publication, the listed editions were current However, all normative documents may be revised, and parties involved in agreements based on this International Standard are encouraged to consider using the latest editions of the referenced documents.

IEC and ISO maintain registers of currently valid International Standards.

IEC 60475: 1974, Method of sampling liquid dielectrics

IEC 60567: 1992, Guide for the sampling of gases and of oil from oil-filled electrical equipment and for the analysis of free and dissolved gases

Design, performance requirements and tests

2 Direct titration for low viscosity liquids

Field of application

This method is applicable to water concentrations above 2 mg/kg in liquids having viscosity up to 100 mm 2 /s at 40 °C The precision data given in 2.10 apply only to new liquids.

1 For liquids in service, the accuracy of the method may be affected by the presence of contaminants and degradation products.

2 The method has been designed to be particularly suitable to hydrocarbon and ester liquids With other liquids, particularly silicone fluids, methanol free reagents must be used.

The Karl Fischer titration involves complex reactions primarily characterized by the interaction of water with iodine in the presence of sulfur dioxide, an organic base, and an alcohol within an organic solvent Initially, the Karl Fischer reagent included pyridine and methanol, and the reactions can be represented as follows:

D'autres associations base-alcool sont possibles et peuvent être nécessaires pour des titrages dans certains liquides isolants.

In Karl Fischer coulometric titration, the sample is mixed with a base-alcohol solution containing iodide ions and sulfur dioxide Iodine is generated through electrolysis and reacts with water, as illustrated in reactions (1) and (2) According to Faraday's law, the amount of iodine produced is directly proportional to the quantity of electricity consumed in the reaction.

Et comme le montre la réaction (1), une mole d'iode réagit stoechiométriquement avec une mole d'eau, de sorte que 1 mg d'eau correspond à 10,72 C (quantité d'électricité en coulombs).

Se fondant sur ce principe, il est possible de calculer la quantité d'eau directement à partir de la quantité d'électricité (en coulombs) consommée par l'électrolyse.

The titration vessel acts as an electrolysis cell with two compartments divided by a porous diaphragm The anodic compartment holds the mixture of reagent, solvent, and sample (anodic solution), while the cathodic compartment (generator assembly) contains the anhydrous reagent (cathodic solution) Electrodes for electrolysis are positioned on either side of the diaphragm.

NOTE – Des titrimètres sans diaphragme poreux peuvent être utilisés.

Iodine generated by electrolysis reacts with water in a manner similar to the reactions described by Karl Fischer The endpoint of this reaction is detected using a pair of platinum electrodes immersed in the anodic solution At the conclusion of the titration, excess iodine depolarizes the platinum electrodes, altering the current-to-voltage ratio, which triggers the endpoint indicator and halts the current integrator.

L'intégrateur de courant somme le courant absorbé au cours de l'électrolyse, calcule la teneur en eau conformément à la loi de Faraday, et finalement l'affiche en microgrammes d'eau.

Les titrimètres coulométriques de Karl Fischer du commerce utilisent des circuits brevetés.

La description suivante d'un des principes acceptables d'appareil est donnée uniquement à titre d'illustration.

Le schéma fonctionnel représenté en figure 1 décrit l'appareil et comprend les éléments ci-dessous.

Chemistry

Karl Fischer titration involves complex reactions primarily between water and iodine, sulfur dioxide, an organic base, and an alcohol in an organic solvent The initial Karl Fischer reagent utilized pyridine and methanol, and these reactions can be summarized as follows:

Other base-alcohol combinations are possible and may be necessary for titrations on some insulating liquids.

Coulometric Karl Fischer titration involves mixing a sample with a base/alcohol solution containing iodide ions and sulfur dioxide Electrolytic generation of iodine occurs, which reacts with water, following specific chemical reactions The amount of iodine produced is directly proportional to the quantity of electricity used, in accordance with Faraday's law.

One mole of iodine reacts with one mole of water, where 1 mg of water corresponds to 10.72 coulombs This relationship allows for the direct determination of water quantity based on the amount of electricity, measured in coulombs, needed for electrolysis.

Apparatus

The titration vessel is designed like an electrolysis cell, featuring two compartments linked by a porous diaphragm The anodic compartment holds a mixture of reagent, solvent, and sample, while the cathodic compartment contains anhydrous reagent Electrolysis electrodes are positioned on either side of the diaphragm.

NOTE – Titrators without the porous diaphragm may be used.

Iodine produced through electrolysis reacts with water similarly to the Karl Fischer reactions The reaction's end-point is identified using platinum electrodes in the anodic solution When excess iodine is present, it depolarizes the electrodes, resulting in a change in the current/voltage ratio that triggers the end-point indicator and halts the current integrator.

The current integrator integrates the current consumed during the electrolysis, calculates the water equivalent according to Faraday's law, and finally displays it in micrograms of water.

Commercial coulometric Karl Fischer titrators use proprietary circuitry The following description of one suitable form of apparatus is given for illustrative purposes only.

The block diagram shown in figure 1 illustrates the apparatus and includes the components detailed below.

Figure 2 illustrates a suitable titration setup However, technological advancements in the device may lead to radically different designs that meet the technical requirements of the current standard.

L'appareil donné à titre d'exemple se compose:

– d'un récipient de titrage en verre à bride (a), muni d'un orifice d'injection (b) de l'échantillon, et d'un robinet de vidange (c) (facultatif);

– d'un couvercle en polytétrafluoroéthylène à bride (d) s'adaptant au vase de titrage Il possède trois ouvertures permettant d'y adapter les électrodes et le tube dessiccateur;

A combined electrolysis cell consists of a glass tube that is sealed at its lower end with a diaphragm This setup includes platinum electrodes positioned on either side of the diaphragm.

The diaphragm can serve as an ion exchange membrane, a sintered glass disc, a ceramic filter, or any other system that prevents the diffusion of two solutions while allowing the passage of current for electrolysis.

– d'électrodes de détection: une paire d'électrodes en platine pour mesure du potentiel ou du courant (f);

– d'un barreau agitateur recouvert de polytétrafluoréthylène (g);

– de tubes dessiccateurs (h) de l'humidité atmosphérique pour protéger le récipient de titrage et l'ensemble générateur;

Silicone rubber septa are used to seal injection ports Prior to use, it is advisable to make cross-incisions in the septa to facilitate the use of square-tipped needles for sample injection It is important to replace the septa as needed to prevent air leaks, which can be indicated by excessive drift in the device.

A stabilized direct current or constant alternating current is applied to the detection electrodes, which are a pair of platinum measuring electrodes, allowing for the detection of the end of the reaction through changes in the polarized current or voltage.

2.3.2.3 Circuit de stabilisation du courant

Ce circuit commande l'électrolyse conformément au signal provenant du circuit de détection.

Alimentation en tension continue pour l'électrolyse.

Indique quand le point final a été atteint.

Mesure la quantité d'électricité consommée par la cellule d'électrolyse au cours du titrage, puis calcule et affiche la quantité d'eau correspondante, en microgrammes.

NOTE – Certains appareils ont des possibilités intégrées de calcul et affichent la teneur en eau pour une quantité particulière d'échantillon.

An electromagnetic stirrer operating at a constant speed is essential for ensuring adequate dispersion Typically, the contents of the container will not be homogeneous, as liquid insulators are not completely miscible with reactive liquids.

A suitable titration vessel assembly is illustrated in figure 2, but advancements in instrument technology may lead to the emergence of significantly different designs that still meet the technical requirements of this standard The apparatus demonstrated includes:

– a flanged glass reaction vessel (a) with sample injection plug (b) and drain cock (c)

– a polytetrafluoroethylene lid (d), flanged to match the titration vessel, with three holes to receive the electrodes and drying tube;

– a generator assembly (combined electrolysis cell) (e) consisting of a glass tube closed at its lower end by a diaphragm and equipped with platinum electrodes on each side of the diaphragm;

NOTE – The diaphragm may consist of ion exchange membrane, fritted disc, ceramic filter or other system to prevent diffusion of both solutions, while allowing enough current for electrolysis.

– detector electrodes: dual platinum electrodes for measurement of potential or current (f);

– drying tubes (h) to protect the titration vessel and the generator assembly from atmospheric moisture;

Silicone rubber septa are essential for sealing the injection port, and it is advisable to make crosscuts in the septa prior to use This preparation allows for the effective use of blunt, square-ended needles during sample injection To maintain optimal performance and prevent air leakage, septa should be replaced as needed, especially if there is noticeable instrument drift.

The detector electrodes, which consist of dual platinum measuring electrodes, receive a constant voltage in DC or a constant current in AC This setup allows for the detection of the end-point by monitoring changes in the polarized current or voltage.

This circuit controls the electrolysis according to the signal from the detector circuit.

DC power supply for electrolysis.

Indicates when the end-point has been reached.

Measures the quantity of electricity consumed by the electrolysis cell during the titration, then calculates and displays the quantity of water, in micrograms, corresponding to it.

NOTE – Some instruments have built-in calculation facilities, and display the water concentration for a specific sample quantity.

An electromagnetic stirrer is essential for achieving a consistent speed that ensures proper dispersion in the titration process Typically, the contents of the titration vessel consist of multiple phases, as most insulating liquids do not fully mix with the reagent liquids.

ATTENTION – Certains réactifs peuvent être nuisibles à la santé et doivent être manipulés avec prudence.

Ready-to-use reagents are commercially available; however, it is essential to ensure that one of these reagents is suitable for the specific type of device being used and the insulating liquid being tested.

Parasitic reactions may occur between methanol-based reagents and certain silicone compounds Similar reactions can also take place with aldehydes, specific ketones, and certain conjugated unsaturated organic acids, which may be present in oils as products or contaminants from degradation In these instances, it is advisable to use reagents that do not contain methanol.

NOTE – L'utilisation de solvants complémentaires ou de substitution peut être nécessaire pour certains liquides isolants.

Auxiliary products include a neutralization solution of methanol containing approximately 20 mg of water per cm³, and a desiccant such as anhydrous magnesium perchlorate or silica gel with an indicator For lubrication, a grease based on polytetrafluoroethylene or fluorinated hydrocarbons is recommended, with commercially available options deemed satisfactory Glass syringes for measuring and injecting samples should be 10 cm³ and 5 cm³ according to ISO 595, equipped with appropriately sized needles For general use, needles of 100 mm in length and 1 mm in diameter are considered adequate, with square-tipped needles preferred to minimize damage to the septum.

Préparer et assembler l'appareil, introduire les réactifs et effectuer la procédure de stabilisation conformément aux instructions du fabricant.

Si les échantillons prélevés sont destinés à des essais autres que celui de la teneur en eau, l'analyse de la teneur en eau doit être effectuée en premier.

Pour les essais de routine, les méthodes d'échantillonnage décrites à l'article 2 et en 3.1 de la

CEI 60475 doivent être utilisées Les flacons de prélèvement doivent être séchés par chauffage dans une étuve à 115 °C ± 5 °C, pendant 16 h à 24 h.

Reagents and auxiliary materials

WARNING – Certain reagents may be detrimental to health and must be handled with proper care.

Prepared reagents are commercially available, but care is needed that the reagent is suitable for the particular type of instrument used and the insulating liquid under test.

Methanol-based reagents can react with certain silicone compounds, as well as with aldehydes, some ketones, and conjugated unsaturated organic acids found in oils as degradation products or contaminants Therefore, it is advisable to use reagents that are not methanol-based in these situations.

NOTE – Some insulating liquids may require the use of additional or alternative solvents.

2.4.2 Auxiliary materials a) Neutralizing solution, methanol containing approximately 20 mg water/cm 3 b) Desiccant, for example, anhydrous magnesium perchlorate or self-indicating silicagel. c) Lubricant grease: Polytetrafluoroethylene based or fluorinated hydrocarbon types.

Commercially available greases of this type have proven to be effective Additionally, glass syringes for sample measurement and introduction, specifically 10 cm³ and 5 cm³ syringes that comply with ISO 595 standards, are equipped with appropriately sized needles.

100 mm and bore 1 mm have been found satisfactory for general use Blunt, square-ended needles are preferred, in order to minimize damage to the septa.

Tiêu đề	IEC 60814 1997
Trường học	Not specified
Chuyên ngành	Electrical Engineering
Thể loại	Standard
Năm xuất bản	1997
Thành phố	Ranchi/Bangalore

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Số trang	54
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