Introduction
Health and Safety
This document is not intended to solve all safety problems related to its use. When using this document, users are responsible for establishing appropriate health and safety rules to ensure the applicability of this document.
The mineral oil involved in this document should be well protected. Direct contact with eyes may cause slight pain. In case of contact with eyes, large quantities of clean and flowing water can be used to wash eyes and seek medical advice in time.
Some tests involved in this document may lead to hazardous situations. Please refer to the relevant guidance documents. Environment This document will cover mineral oils, chemicals and used sample containers. Relevant disposal should avoid environmental impact, and various preventive measures should be taken to prevent mineral pollution.
The acid value measurement standards for insulating liquids are widely used in the R&D, production, quality inspection, sales, acceptance and technical exchange of insulating liquid products. The formulation of this series of standards can guide the industry to more effectively carry out the detection and evaluation of the acid value of insulating liquids, and can improve the quality and application reliability of insulating liquid products.
The acid value measurement standards for insulating liquids are prepared in different parts. In order to maintain the basic consistency with the preparation methods of corresponding IEC standards, different parts shall be listed separately when preparing this series of documents.
GB/T 41633 describes the standard method for the determination of acid value of insulating liquids. The following parts are proposed:
——Part 1: Automatic potentiometric titration. The purpose is to determine the method and step of measuring the acid value of insulating liquid by automatic potentiometric titration.
——Part 2: Colorimetric titration. The purpose is to determine the method and step of determining the acid value of insulating liquid by colorimetric titration.
——Part 3: Test methods for non mineral insulating oils Determination of unused and used non mineral insulating oleic acids for electrical purposes
Two test methods of the value; Automatic potentiometric titration and colorimetric titration.
1 Scope
This document describes two test methods for acid value of unused and used non mineral insulating oil for electrical purposes: potentiometric titration and colorimetric titration.
Note 1: In unused and used non mineral insulating oils for electrical purposes, acidic components include organic acids, phenolic compounds, oxidation products, resins, organic metal salts and additives
This document can be used to indicate the relative changes of non mineral insulating oil for electrical purposes during use under oxidation conditions, regardless of whether its chromaticity or other characteristics have changed.
Acid value can be used for quality control of unused non mineral insulating oil for electrical purposes. The oxidation products existing in the used non mineral insulating oil for electrical purposes will affect its acid value, and these oxidation products have large differences in corrosion characteristics, so this document cannot be used to predict the corrosivity of non mineral insulating oil for electrical purposes in use.
Note 2: The acid value results measured by potentiometric titration and colorimetric titration may be the same or different in value, but they are usually in the same order of magnitude.
2 Normative References
The contents in the following documents constitute indispensable provisions of this document through the normative A in the text. Where, for dated references, only the version corresponding to that date applies to this document; For undated references, the latest version (including all amendments) is applicable to this document.
ISO 5725 (all parts) Accuracy (trueness and pre precision) of measurement methods and results
Note: GB/T 6379 (all parts) Accuracy (correctness and precision) of measurement methods and results [ISO 5725 (all parts)]
ISO 6619 Petroleum products and lubricants - Neu titration number - Potentiometric titration method
IEC 60475 Method of sampling insulating liquids Note: GB/T41146-2021 Sampling methods for insulating liquids (IEC 60475:2011, IDT)
3 Terms and definitions
The following terms and definitions apply to this document.
three point one
Acid value
The amount of alkali required for titration to the end point after dissolving the sample in the specified solvent by potentiometric titration or colorimetric titration, expressed by the mass fraction of potassium hydroxide in the sample.
Note: See Appendix A for the acid value of non mineral insulating oil determined by photometric titration
4 Method A: Automatic potentiometric titration
4.1 Principle
Any acid-base titration can be carried out by potentiometry. Dissolve the insulating oil sample in the solvent, use the glass indicator electrode and reference electrode, and use potassium hydroxide isopropanol solution for potentiometric titration. The potential difference (which can be expressed by pH value after calibration) is measured after continuous addition of a known amount of potassium hydroxide isopropanol solution.
The apparent inflection point detected from the first derivative of the titration curve should be considered as the end point. If there is only a weak inflection point, the potential difference corresponding to pH 11.5 is more reproducible and less instrument dependent.
4.2 Reagents and auxiliary materials
5 Method B: Colorimetric titration
5.1 Principle
Dissolve the insulating oil sample in the specified solvent, use alkaline blue 6B as the indicator, and titrate it with potassium hydroxide isopropanol solution to the specified color.
Note: Colorimetric titration may not be applicable to dark insulating oil.
5.2 Reagents
5.2.1 General
The reagent shall be the certified analytical reagent, and the test water shall be deionized water or water of the same purity.
5.2.2 Titration reagent
0.01 mol/L and 0.05 mol/L potassium hydroxide isopropanol standard solutions are used as titration reagents for the test.
Appendix A (informative) Determination of Acid Number of Non mineral Insulating Oil by Photometric Titration
Forword
Introduction
1 Scope
2 Normative References
3 Terms and definitions
4 Method A: Automatic potentiometric titration
5 Method B: Colorimetric titration
Appendix A (informative) Determination of Acid Number of Non mineral Insulating Oil by Photometric Titration
引言
健康和安全
本文件并非旨在解决与其使用相关的所有安全问题,在用本文件时使用者有责任建立适当的健康和安全规则,确保本文件的适用性。
本文件所涉及的矿物油宜做好个人防护,如直接接触眼睛可能引起轻微的疼痛,如接触眼睛,可用大量干净流动的水冲洗眼睛并及时就医。
本文件会涉及的一些试验可能导致危险情况的发生。请参考相关的指导文件。环境本文件会涉及矿物油,化学药品和使用过的样品容器。有关处置宜避免对环境产生影响,宜采取各种预防措施防止矿物污染环境。
绝缘液体酸值测定标准广泛应用于绝缘液体产品的研发、生产,质检、销售、验收及技术交流等,制定该系列标准可指导行业更有效地开展对绝缘液体酸值的检测和评定,可提高绝缘液体产品的质量及应用可靠性。
绝缘液体酸值测定标准分为不同的部分编写的,为保持与对应的IEC标准编写方法基本一致,在编制本系列文件时需单列不同部分进行编制。
GB/T 41633描述了绝缘液体酸值测定的标准方法,拟出下列部分构成:
——第1部分:自动电位滴定法。目的是确定用自动电位滴定法测定绝缘液体酸值的方法和步骤。
——第2部分:比色滴定法。目的是确定用比色滴定法测定绝缘液体酸值的方法和步骤。
——第3部分:非矿物绝缘油试验方法d县的是确定未使用的和使用过的电气用非矿物绝缘油酸
值的两种试验方法;自动电位滴定法和比色滴定法。
1范围
本文件描述了未使用的和使用过的电气用非矿物绝缘油酸值的两种试验方法:电位滴定法和比色滴定法。
注1:在未使用的和使用过的电气用非矿物绝缘油中,酸性组分包括有机酸,酚类化合物,氧化产物、树脂类,有机金属盐及添加剂等.
本文件可用于指示电气用非矿物绝缘油在氧化条件下使用期间所发生的相对变化,而不考虑其色度或其他特性是否发生改变。
酸值可用于未使用的电气用非矿物绝缘油的质量控制。使用过的电气用非矿物绝缘油中存在的氧化产物会对其酸值产生影响,且这些氧化产物在腐蚀特性方面具有较大的差异,故本文件不能用于预测使用中的电气用非矿物绝缘油的腐蚀性。
注2:通过电位滴定法测得的酸值结果与比色滴定法测得的酸值结果在数值上可能相同也可能不同,但是它们通常是在同一个数量级的。
2规范性引用文件
下列文件中的内容通过文中的规范性A用而构成本文件必不可少的条款。其中,注日期的引用文件,仅该日期对应的版本适用于本文件;不注日期的引用文件,其最新版本(包括所有的修改单)适用于本文件。
ISO 5725(所有部分)测量方法和结果的准确度(正确度和精密度)[Accuracy (trueness and pre-cision) of measurement methods and results]
注:GB/T 6379(所有部分)测量方法与结果的准确度(正确度与精密度)[ISO 5725(所有部分)]
ISO 6619石油产品和润滑剂﹐中和值﹑电位滴定法(Petroleum products and lubricants - Neu-tralization number - Potentiometric titration method)
IEC 60475绝缘液体取样方法(Method of sampling insulating liquids)注:GB/T41146-2021绝缘液体取样方法(IEC 60475:2011,IDT)
3术语和定义
下列术语和定义适用于本文件。
3.1
酸值acidity
用电位滴定法或比色滴定法将试样溶解在指定的溶剂中后,进行滴定至终点时所需的碱量,以试样中氢氧化钾的质量分数表示。
注:有关光度滴定法测定非矿物绝缘油的酸值见附录A.
4方法A:自动电位滴定法
4.1原理
任何酸碱滴定都可以通过电位法进行。将绝缘油试样溶解在溶剂中,使用玻璃指示电极和参比电极,用氢氧化钾异丙醇溶液进行电位滴定。电位差(校准后可用pH值表示)是在连续添加已知数量的氢氧化钾异丙醇溶液后测量的。
从滴定曲线一阶导数中检测到的明显拐点宜被视为终点。如果只出现一个微弱的拐点,对应于pH值为11.5的电位差更具有重现性,仪器依赖性更小。
4.2试剂和辅助材料
5方法B:比色滴定法
5.1原理
将绝缘油试样溶解在指定的溶剂中,采用碱性蓝6B作为指示剂,用氢氧化钾异丙醇溶液滴定至指定的颜色。
注:比色滴定法可能不适用于深色绝缘油。
5.2试剂
5.2.1通则
试剂应采用经过认证的分析纯试剂,试验用水应采用去离子水或是相同纯度的水。
5.2.2滴定试剂
试验用滴定试剂采用0.01 mol/L和0.05 mol/L的氢氧化钾异丙醇标准溶液。
附录A(资料性)
光度滴定法测定非矿物绝缘油的酸值