EN 62021-1:2003

Insulating liquids - Determination of acidity - Part 1: Automatic potentiometric titration

Describes the procedure for the determination of the acidity of unused and used electrical mineral insulating oils. 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 quality 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. The acidity results obtained 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.

Isolierflüssigkeiten - Bestimmung des Säuregehaltes - Teil 1: Automatische potentiometrische Titration

Liquides isolants - Détermination de l'acidité - Partie 1: Titrage potentiométrique automatique

Décrit la procédure pour la détermination de l'acidité des huiles isolantes minérales électriques neuves et usagées. La méthode peut être utilisée pour indiquer des modifications relatives qui se produisent dans une huile minérale isolante pendant son utilisation par oxydation, indépendamment de la couleur ou d'autres propriétés de l'huile. L'acidité peut être utilisée dans le contrôle de la qualité des huiles minérales neuves. Comme divers produits d'oxydation présents dans l'huile minérale usagée contribuent à l'acidité et comme ces produits varient largement du point de vue de leurs propriétés de corrosion, l'essai ne peut pas être utilisé pour prévoir la corrosivité d'une huile minérale dans des conditions de service. Les résultats d'acidité obtenus par cette méthode d'essai peuvent ou peuvent ne pas être numérique-ment les mêmes que ceux obtenus par des méthodes colorimétriques, mais ils sont généralement du même ordre de grandeur.

Insulating liquids - Determination of acidity - Part 1: Automatic potentiometric titration (IEC 62021- 1:2003)

General Information

• Status: Published
• Publication Date: 24-Sep-2003
• Withdrawal Date: 31-Aug-2006
• ICS: 29.040.10 - Insulating oils
• ICS: 29.180 - Transformers. Reactors
• Technical Committee: CLC/SR 10 - Fluids for electrotechnical applications
• Drafting Committee: IEC/TC 10 - IEC_TC_10
• Parallel Committee: IEC/TC 10 - IEC_TC_10
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 25-Sep-2003
• Completion Date: 25-Sep-2003
• Ref Project: SIST EN 62021-1:2004 - Insulating liquids - Determination of acidity -- Part 1: Automatic potentiometric titration

Overview

EN 62021-1:2003 (CLC), identical to IEC 62021-1:2003, specifies an automatic potentiometric titration method for the determination of acidity in unused and used electrical mineral insulating oils. The procedure measures the quantity of base (expressed as mg KOH/g sample) required to reach a potentiometric end-point of pH 11.5 after dissolving the oil in a titration solvent. The method is intended for tracking relative changes in acidity caused by oxidation during service and for quality control of unused oil. It is not intended to predict oil corrosiveness under actual service conditions.

Key Topics and Technical Requirements

• Scope: Applicable to unused and used mineral insulating oils; detects acidity from organic acids, phenolics, oxidation products, resins, organometallic salts and additives.
• Principle: Sample dissolved in solvent (2‑propanol / isopropanol) and titrated potentiometrically with alcoholic KOH (standard ~0.05 mol/L) using a glass indicating electrode and a reference electrode. Endpoint taken at pH 11.5.
• Reagents:
  • Alcoholic potassium hydroxide titrant (approx. 0.05 mol/L, standardized against primary standard)
  • 2-propanol (IPA) as titration solvent
  • Potassium hydrogen phthalate (primary standard)
  • Potassium chloride reference electrolyte, buffer solutions (pH 4, 7, 11)
  • Electrode cleaning solution (ammonium peroxydisulphate + sulfuric acid) or manufacturer-recommended cleaners
• Apparatus:
  • Automatic potentiometric titrimeter with software/curve-plotting to determine endpoint
  • Automatic burette with dispensing accuracy ±0.005 mL
  • Electrode system (indicating and reference), stirrer, titration vessel and stand
• Calibration & Maintenance: Electrode calibration with aqueous buffers, standardization of alcoholic KOH (see clause 10.1), periodic cleaning and calibration to ensure accuracy.
• Limitations: Results may differ numerically from colorimetric acidity tests but are generally of the same magnitude. The test does not reliably predict corrosiveness because oxidation products contributing to acidity have varied corrosion behaviour.

Applications and Users

• Who uses it:
  • Transformer and electrical equipment manufacturers
  • Utilities and substations for routine oil monitoring
  • Analytical and accreditation laboratories performing dielectric fluid testing
  • Oil producers and quality control laboratories
• Practical uses:
  • Routine quality control of unused insulating oils
  • Monitoring oxidation and degradation trends in service-aged oils
  • Comparative assessments of oil condition during maintenance programs

Related Standards

• IEC 62021-1:2003 (identical international text)
• IEC 60475 - Method of sampling liquid dielectrics (referenced for sampling practice)

Keywords: EN 62021-1:2003, insulating liquids, acidity determination, potentiometric titration, mineral insulating oils, automatic titrator, KOH titrant, oil quality control.

Standards Content (Sample)

SLOVENSKI SIST EN 62021-1:2004

STANDARD
april 2004
Insulating liquids - Determination of acidity - Part 1: Automatic potentiometric
titration (IEC 62021- 1:2003)
ICS 29.040.10 Referenčna številka
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

EUROPEAN STANDARD EN 62021-1
NORME EUROPÉENNE
EUROPÄISCHE NORM September 2003

ICS 29.040.10; 29.180
English version
Insulating liquids -
Determination of acidity
Part 1: Automatic potentiometric titration
(IEC 62021-1:2003)
Liquides isolants -  Isolierflüssigkeiten -
Détermination de l'acidité Bestimmung des Säuregehaltes
Partie 1: Titrage potentiométrique Teil 1: Automatische potentiometrische
automatique Titration
(CEI 62021-1:2003) (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 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
language 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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für 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
Foreword
The text of document 10/559/FDIS, future edition 1 of IEC 62021-1, prepared by IEC TC 10, Fluids for
electrotechnical 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) 2004-06-01

– 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 International Standard IEC 62021-1:2003 was approved by CENELEC as a European
Standard without any modification.
__________
- 3 - EN 62021-1:2003
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of any
of these publications apply to this European Standard only when incorporated in it by amendment or
revision. For undated references the latest edition of the publication referred to applies (including
amendments).
NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
1)
IEC 60475 - Method of sampling liquid dielectrics - -

1)
Undated reference.
NORME CEI
INTERNATIONALE IEC
62021-1
INTERNATIONAL
Première édition
STANDARD
First edition
2003-06
Liquides isolants –
Détermination de l'acidité –
Partie 1:
Titrage potentiométrique automatique
Insulating liquids –
Determination of acidity –
Part 1:
Automatic potentiometric titration
© IEC 2003 Droits de reproduction réservés ⎯ Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. the publisher.
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Pour prix, voir catalogue en vigueur
For price, see current catalogue

62021-1 © IEC:2003 – 3 –
CONTENTS
FOREWORD . 5
INTRODUCTION .7
1 Scope . 9
2 Normative references. 9
3 Terms and definitions . 9
4 Principle .11
5 Reagents and auxiliary products .11
5.1 Reagents .11
5.2 Titration reagent .11
5.3 Titration solvent.11
5.4 Potassium hydrogen phthalate, primary standard.11
5.5 Potassium chloride reference electrolyte.13
5.6 Aqueous buffer solutions .13
5.7 Cleaning solution.13
6 Apparatus .13
6.1 Potentiometric titration apparatus .13
6.2 Glass indicating electrode.13
6.3 Reference electrode .13
6.4 Stirrer .15
6.5 Titration vessel .15
6.6 Titration stand .15
7 Sampling .15
8 Preparation and maintenance of electrode system .15
9 Calibration of apparatus.17
10 Procedure.17
10.1 Standardization of alcoholic potassium hydroxide solution .17
10.2 Blank titration .19
10.3 Sample titration .19
11 Calculation.21
12 Precision .21
12.1 Repeatability.21
12.2 Reproducibility.21
13 Report .23
Bibliography.25

62021-1 © IEC:2003 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
INSULATING LIQUIDS –
DETERMINATION OF ACIDITY –
Part 1: Automatic potentiometric titration
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International
Organization for Standardization (ISO) in accordance with conditions determined by agreement between the
two organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62021-1 has been prepared by IEC technical committee 10: Fluids
for electrotechnical applications.
The text of this standard is based on the following documents:
FDIS Report on voting
10/559/FDIS 10/564/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until 2012.
At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
62021-1 © IEC:2003 – 7 –
INTRODUCTION
General caution
This International Standard does not purport to address 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 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 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 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.

62021-1 © IEC:2003 – 9 –
INSULATING LIQUIDS –
DETERMINATION OF ACIDITY –
Part 1: Automatic potentiometric titration
1 Scope
This part of IEC 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 oxidation 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 quality 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 obtained 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 magnitud
...