IEC 61868:1998 pdf download – Mineral insulating oils – Determination of kinematic viscosit yat very low temperatures

IEC 61868:1998 pdf download – Mineral insulating oils – Determination of kinematic viscosit yat very low temperatures.
IEC 61868 specifies a procedure tar the determination of the kinematic viscosity of mineral insulating oils, both transparent and opaque, at very low temperatures. after a cold soaking period of at least 20 h. by measuring the time for a volume of liquid to flow under gravity through a calibrated glass capillary viscorneter.
It is applicable at all temperatures to both Newtonian and non-Newtonian liquids having viscosities of up to 20000 mm2 x s1. It is particularly suitable for the measurement of the kinematic viscosity of liquids for use in cold climates, at very low temperatures (—40 °C) or at temperatures between the cloud and pour-point temperatures (typically —20 °C) where some liquids may develop unexpectedly high viscosities under cold soak conditions.
2 Normative references
The following normative documents contain provIsions which, through reference In this text. constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All normative documents are Subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. Members of lEG and ISO maintain registers of currently valid International Standards
ISO 3104:1994. Petroleum products — Transparent and opaque liquids — Determination of kinematic viscosity and calculation of dynamic viscosity
ISO 3105:1994, Glass capillary kinematic viscometers — Specification and operating instructions
3 Definitions
For the purpose of this International Standard, the following definitions apply:
3.1
kinematic viscosity
the ratio between the viscosity and the density of the liquid. It is a measure of the resistance to flow of a liquid under gravity
NOTE — In me SI, the unit ot knemalic viacoelly Is me square metre pe second rn2
3.2
newtonian liquid
a liquid having a viscosity that is independent of the shear stress or shear rate. If the ratio of shear stress to shear rate is not constant,
5.2 Viscometer holders
The holder shall allow the viscometer to be suspended In a position similar to that adopted for calibration. The proper alignment of a vertical datum part may be confirmed by using a plumb line.
5.3 Vlseometer bath arid aceessorles
A suitable set-up, placed in a freezer tank, is described in figure 1. Any transparent liquid bath may be used provided that it Is of sufficient depth that at no time during the measurement will any portion of the sample in the viscometer be less than 20 mm below the surface of the bath liquid or less than 20 mm above the bottom of the bath. Methanol has been found appropriate as a bath medium. However, any liquid which as clear, does not freeze at operating temperature, and does no harm to the silicone-based caulking material used for the glass bath construction, can e used Instead ol methanol, for example -propanoI
The temperature control shall be such that the temperature of the bath medium does not vary by more than 0.03 C over the length of the viscometers, or between the position of each viscometer, or at the location of the thermometer,
5.4 Temperature measuring device
Calibrated liquid-in-glass thermometers of a minimum accuracy after correction of 0,02 C may be used, or any other thermometric or battery-operated device of equal accuracy. All readings and corrections shall be made at least to the nearest 0.02 C. IP Standard thermometer 68C or ASTM standard thermometer 73C (corresponding to ASTM specification El).