IEC 62961:2018 pdf download

IEC 62961:2018 pdf download.Insulating liquids – Test methods for the determination of interfacial tension of insulating liquids – Determination with the ring method
1 Scope
This document establishes the measurement of the interfacial tension between insulating liquid and water by means of the Du Noüy ring method close to equilibrium conditions. In order to obtain a value that provides a realistic expression of the real interfacial tension, a measurement after a surface age of approximately 1 80 s is recorded.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 862, Surface active agents – Vocabulary ISO 3675, Crude petroleum and liquid petroleum products – Laboratory determination of density – Hydrometer method ISO 1 21 85, Crude petroleum and petroleum products – Determination of density – Oscillating U-tube method EN 1 4370, Surface active agents – Determination of surface tension
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 862 and the following apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: • IEC Electropedia: available at http://www.electropedia.org/ • ISO Online browsing platform: available at http://www.iso.org/obp 3.1 interfacial tension tension at the interface between two phases Note 1 to entry: The SI unit of interfacial tension is the Newton per metre (N/m). In practice, the submultiple millinewton per metre (mN/m) is used.
4 Principle
The maximum force, F, necessary to pull or to force a ring of perimeter πD out of the interface between insulating liquid and water in the direction of the insulating liquid is measured. The interfacial tension, σ , is obtained by calculation, where the following approximate equation (1 ) serves as the base:To obtain exact values for surface or interfacial tension, it is necessary to measure the maximum force on pulling the ring out of the liquid. Because of the great risk of detachment in the case of the manual apparatus, extremely smooth manipulation is necessary since the value obtained immediately prior to detachment of the film is not identical to the maximum value. Automatic tensiometers can determine the maximum value electronically and reverse the platform movement promptly prior to detachment of the film. This makes it possible to obtain reliable, accurate time-consistent serial measurements without tearing the film.
5 Apparatus
5.1 Tensiometer The tensiometer shall be designed for a ring and shall consist mainly of two parts: • support for the sample vessel in the form of a small horizontal platform which can be moved up and down; • apparatus for measuring the force exerted on the ring; the uncertainty of measurement shall not exceed ± 1 0 -6 N, which corresponds to a maximum error of ± 0,1 mg weight measurement. Instead of a torsion balance as stated in ASTM D971 , a lever balance or an electronic balance (laboratory, analytical or microbalance) can be used. To obtain higher efficiency and reproducibility, it is recommended to use an automatic tensiometer incorporating a balance, motor driven platform and evaluation unit.
7 Procedure
7.1 General The measurement shall be done in the temperature range between 1 8 °C and 25 °C. The water and insulating liquid shall be at the same temperature. The density of the insulating liquid shall be determined at the temperature of measurement or can be calculated from a linear extrapolation of density from measurement at a standard temperature (e.g. 20 °C) to the temperature used for the IFT measurement. Round robin test results have shown that variations within this temperature range do not practically influence the test results. The correction according to Zuidema and Waters [5] shall be used. The correction of Zuidema and Waters [5] is the preferred correction, since it is the most widely used in existing standards (ASTM D971 , EN 1 421 0, EN 1 4370). Further corrections known are those of Harkins and Jordan [6], Fox and Chrisman [7], and Huh and Mason [8]. If another correction formula is used, this shall be noted in the test report.