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Tag Archive: temperature

Temperature-Viscosity Chart

The interpolation calculator provided below is used to determine:

  • the kinematic viscosity values, depends from temperature, calculated by the formulas specified in ASTM D341 – (‘Standard Practice for Viscosity-Temperature Charts for Liquid Petroleum Products’);
  • the Viscosity Index (VI) by the formulas specified in ASTM D2270 (`Standard Practice for Calculating Viscosity Index from Kinematic Viscosity at 40 and 100°C 1`) or in ISO 2909 (`Standard Practice for Calculating Viscosity Index from Kinematic Viscosity at 40 and 100°C 1`) or in ГОСТ 25371-2018 (`Нефтепродукты. Расчёт индекса вязкости по кинематической вязкости`)

Annotation.

Any mineral oil is supplied with the specification of kinematic viscosity values at two different temperatures, usually at 40°C and at 100°C (or at 100°F and at 210°F). These data is enough to determine kinematic viscosity at any other values of temperature and as well Viscosity Index.

You can calculate pre-filled values of oil classified by ISO 3448 with grades VG22, VG32, VG46 or VG68 (at viscosity Index = 100) or enter specific values for any other oils.

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Pressure change due to temperature

A change in temperature will cause hydraulic fluid to try to have a corresponding change in volume. If the fluid is trapped in a chamber and is unable to change volume, there will be a change in pressure.

The difference in pressure is based on the bulk modulus (stiffness) of the fluid. A mineral based oil may have a pressure difference of about 11 bar for each 1°C change in temperature (90 psi for each 1°F change in temperature):

\triangle p=\triangle t\cdot k,

where k= 90 (imperial units) or k= 11 (metrical units):

\triangle p\;\lbrack PSI\rbrack\;=\triangle t\;{\lbrack^\circ F}\rbrack\cdot90

or:

\triangle p\;\lbrack bar\rbrack\;=\triangle t\;{\lbrack^\circ C}\rbrack\cdot90