1、BRITISH STANDARD BS EN 62021-1:2003 Insulating liquids Determination of acidity Part 1: Automatic potentiometric titration The European Standard EN 62021-1:2003 has the status of a British Standard ICS 29.040.10; 29.180 BS EN 62021-1:2003 This British Standard was published under the authority of th
2、e Standards Policy and Strategy Committee on 23 December 2003 BSI 23 December 2003 ISBN 0 580 43144 4 National foreword This British Standard is the official English language version of EN 62021-1:2003. It is identical with IEC 62021-1:2003. The UK participation in its preparation was entrusted to T
3、echnical Committee GEL/10, Fluids for electrotechnical applications, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications refer
4、red to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provis
5、ions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation,
6、or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 14, an inside back cover and a back cover.
7、The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEAN STANDARD EN 62021-1 NORME EUROPENNE EUROPISCHE NORM September 2003 CENELEC European Committee for Electrotechnical Standardization Comit
8、 Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 2003 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 62021-1:2003 E ICS 29.040.
9、10; 29.180 English version Insulating liquids - Determination of acidity Part 1: Automatic potentiometric titration (IEC 62021-1:2003) Liquides isolants - Dtermination de lacidit Partie 1: Titrage potentiomtrique automatique (CEI 62021-1:2003) Isolierflssigkeiten - Bestimmung des Suregehaltes Teil 1
10、: Automatische potentiometrische Titration (IEC 62021-1:2003) This European Standard was approved by CENELEC on 2003-09-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard
11、 without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in any other l
12、anguage made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic, Denmark, Finland, Fra
13、nce, Germany, Greece, Hungary, Iceland, Ireland, Italy, Lithuania, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United Kingdom. Foreword The text of document 10/559/FDIS, future edition 1 of IEC 62021-1, prepared by IEC TC 10, Fluids for electrotechnical
14、 applications, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 62021-1 on 2003-09-01. The following dates were fixed: latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2004-06-
15、01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2006-09-01 Annexes designated “normative“ are part of the body of the standard. In this standard, annex ZA is normative. Annex ZA has been added by CENELEC. _ Endorsement notice The text of the Internat
16、ional Standard IEC 62021-1:2003 was approved by CENELEC as a European Standard without any modification. _ Page2 EN620211:2003CONTENTS INTRODUCTION.4 1 Scope.5 2 Normative references.5 3 Terms and definitions .5 4 Principle.6 5 Reagents and auxiliary products.6 5.1 Reagents.6 5.2 Titration reagent6
17、5.3 Titration solvent.6 5.4 Potassium hydrogen phthalate, primary standard 6 5.5 Potassium chloride reference electrolyte .7 5.6 Aqueous buffer solutions.7 5.7 Cleaning solution.7 6 Apparatus.7 6.1 Potentiometric titration apparatus7 6.2 Glass indicating electrode .7 6.3 Reference electrode7 6.4 Sti
18、rrer8 6.5 Titration vessel8 6.6 Titration stand.8 7 Sampling8 8 Preparation and maintenance of electrode system8 9 Calibration of apparatus.9 10 Procedure9 10.1 Standardization of alcoholic potassium hydroxide solution.9 10.2 Blank titration10 10.3 Sample titration.10 11 Calculation.11 12 Precision
19、11 12.1 Repeatability.11 12.2 Reproducibility 11 13 Report12 Annex ZA (normative) Normative refereneces to international publications with their corresponding European publications .13 Bibliography14 Page3 EN620211:2003INTRODUCTION General caution This International Standard does not purport to addr
20、ess all the safety problems associated with its use. It is the responsibility of the user of the standard to establish appropriate health and safety practices and determine the applicability of regulatory limitations prior to use. The insulating liquids which are the subject of this standard should
21、be handled with due regard to personal hygiene. Direct contact with the eyes may cause slight irritation. In the case of eye contact, irrigation with copious quantities of clean running water should be carried out and medical advice sought. Some of the procedures referenced in this standard involve
22、the use of processes that could lead to a hazardous situation. Attention is drawn to the relevant standard for guidance. Environment This standard gives rise to mineral insulating oils, chemicals, used sample containers and fluid-contaminated solids. The disposal of these items should be carried out
23、 according to local regulations with regard to their impact on the environment. Every precaution should be taken to prevent the release into the environment of these oils. Page4 EN620211:2003INSULATING LIQUIDS DETERMINATION OF ACIDITY Part 1: Automatic potentiometric titration 1 Scope This part of I
24、EC 62021 describes the procedure for the determination of the acidity of unused and used electrical mineral insulating oils. NOTE 1 In unused and used mineral insulating oils, the constituents that may be considered to have acidic characteristics include organic acids, phenolic compounds, some oxida
25、tion products, resins, organometallic salts and additives. The method may be used to indicate relative changes that occur in a mineral insulating oil during use under oxidizing conditions regardless of the colour or other properties of the resulting mineral oil. The acidity can be used in the qualit
26、y control of unused mineral oil. As a variety of oxidation products present in used mineral oil contribute to acidity and these products vary widely in their corrosion properties, the test cannot be used to predict corrosiveness of a mineral oil under service conditions. NOTE 2 The acidity results o
27、btained by this test method may or may not be numerically the same as those obtained by colorimetric methods, but they are generally of the same magnitude. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the
28、 edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60475, Method of sampling liquid dielectrics 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 acidity quantit
29、y of base, expressed in milligrams of potassium hydroxide per gram of sample, required to titrate potentiometrically a test portion in a specified solvent to obtain a pH of 11,5 3.2 unused oil mineral oil which has not been used in, or been in contact with, electrical equipment Page5 EN620211:20034
30、Principle The test portion is dissolved in solvent and titrated potentiometrically with alcoholic potassium hydroxide using a glass-indicating electrode and a reference electrode. The meter readings are plotted automatically against the respective volumes of titrant and the end-point is taken when t
31、he volume corresponds to a pH of 11,5. This was found to include all inflection points, with very little effect on the result from the rapid change in pH after the last inflection point. While use of inflection points is more accurate, it was found that measurement of weak inflection points was more
32、 instrument-dependent and gave poorer reproducibility. 5 Reagents and auxiliary products 5.1 Reagents Only reagents of recognized analytical grade and de-ionized water or water of equivalent purity shall be used. 5.2 Titration reagent Standard volumetric alcoholic solution 0,05 mol/l potassium hydro
33、xide. Add 3,0 g of potassium hydroxide to 1 000 ml 10 ml of 2-propanol. Boil gently for 10 min to effect solution. Cool and stopper the flask. Allow the solution to stand in the dark for 2 days and then filter the supernatant liquid through a 5 m membrane filter. Store in a suitable amber glass bott
34、le. The concentration of this solution is approximately 0,05 mol/l and shall be standardized as described in 10.1. For periodic tests on equipment in service, faster titration may be achieved by the use of 0,1 mol/l potassium hydroxide by agreement between the laboratory and the equipment owner, alt
35、hough this may result in poorer precision and detection limit. Store in such a manner that the solution is protected from atmospheric carbon dioxide by means of a guard tube containing soda-lime absorbent and in such a way that it does not come into contact with cork, rubber or saponifiable stopcock
36、 grease. Commercial alcoholic potassium hydroxide solution may be used, if necessary diluting to 0,05 mol/l with 2-propanol. This shall be standardized as described in 10.1. 5.3 Titration solvent 2-propanol (isopropanol, IPA). 5.4 Potassium hydrogen phthalate, primary standard This should be dried b
37、efore use for 2 h at 105 C. NOTE A 0,1 mol/l solution of hydrochloric acid in de-ionized water, prepared as in ISO 6619, may be used. Other acids may be used, provided they are certified against a primary standard. Page6 EN620211:20035.5 Potassium chloride reference electrolyte Prepare a solution of
38、 potassium chloride in de-ionized water at the concentration recom- mended by the electrode manufacturer. Commercially available solutions may be used where available. 5.6 Aqueous buffer solutions Buffer solutions of suitable pH for calibration of electrodes, for example, pH 4, pH 7 and pH 11. 5.7 C
39、leaning solution Weigh 8 g of ammonium peroxydisulphate into a glass beaker. Carefully add 100 ml of 98 % sulphuric acid and gently stir. Before use, the solution should be left overnight for the solid to dissolve completely. WARNING Ammonium peroxydisulphate is a strong oxidizing agent. Sulphuric a
40、cid is a strong corrosive agent. Handle carefully. Commercially available cleaning solutions as recommended by the electrode manufacturer may be used. 6 Apparatus 6.1 Potentiometric titration apparatus An automatic pH titrimeter capable of titrating to a fixed end-point using either variable or fixe
41、d titrant increments. The instrument shall be protected from stray electrical fields so that no change of the reading is produced by touching any part of the system with a grounded lead. An automatic burette with a dispensing accuracy of 0,005 ml or better is required. A reservoir for the titrating
42、solution. It shall be fitted with a guard tube containing soda lime or other carbon dioxide absorbing material. 6.2 Glass indicating electrode A glass electrode specifically designed for non-aqueous titrations is recommended. The electrode shall be connected to the potentiometer by means of a suitab
43、ly screened cable such that the resistance between the screening and the entire length of the electrical connection is greater than 50 000 M . 6.3 Reference electrode The electrode shall be made of glass and shall be provided with a movable joint in the form of a sleeve or plug to facilitate easy wa
44、shing of the reference electrolyte cell. It is recommended that a double junction design is used and the electrolyte cells filled with potassium chloride electrolyte (see 5.5). The electrode shall be reserved for non-aqueous titrations. Page7 EN620211:2003NOTE Certain alternative electrode-electroly
45、te combinations have been found to give satisfactory results, although the precision using these alternatives has not been determined. Combined electrodes may be used provided they otherwise conform to this standard and have at least a similar speed of response. 6.4 Stirrer The stirrer should have a
46、 variable speed and be fitted with a propeller, paddle or magnetic bar of chemically inert surface material. It shall be electrically grounded to avoid any change in the meter reading during the course of the titration. 6.5 Titration vessel This should be as small as possible, sufficient to contain
47、the solvent, sample, stirrer and electrodes and be inert to the reagents. Glass vessels are preferred to prevent build-up of electrostatic charge. 6.6 Titration stand A suitable stand to support the beaker, electrodes, stirrer and burette. 7 Sampling Samples shall be taken following the procedure gi
48、ven in IEC 60475. Ensure that the test portion is representative by thoroughly mixing, as any sediment present may be acidic or have adsorbed acidic material from the liquid phase. 8 Preparation and maintenance of electrode system Although electrodes are not particularly fragile they should be handl
49、ed carefully at all times. 8.1 Preparation Rinse the electrodes with 2-propanol and finally with de-ionized water. Following each titration immerse the electrodes in de-ionized water to remove any surplus electrolyte adhering to the outside of the electrode and allow excess water to drain off. The immersion time should be sufficient to prevent any memory effects on subsequent titrations. When in use, any plug that is present on the reference electr
