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Oil viscosity as a function of temperature

C compressormanMember
I've searched several places but can't find a method for calculating viscosity of a lube oil as a function of temperature. Typically oil viscosity is given by the manufacturer at two points, xx SUS at 100F and 210F or xx cSt at 40C and 100C. How do I calculate the viscosity at my actual operating temperature using the given data points?
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M mikhailMember
Hi Compressor Man,
Many years ago I found the formula using for calculation the oil viscosity for temperatures more than 100C.
Vt = V100 x Ct, where
Vt - kinematic viscosity at required temperature (cSt),
V100 - kinematic viscosity at 100C (cSt),
Ct - averaged coefficient that equal
Ct = 1/[(e raise to t/103) - 1.63]
Maybe it will be useful for you.
Regards,
H hussamadeniMember
Mineral oils follow behaviour of Newtonian fluids. Oils of the same VI can be plotted on a linear graph. On a XY linear graph you will have to plot the known values of Viscosity at KV 40 and that of KV 100 and draw a straight line between the points. For any temperature between 100 and 40 Deg C just draw a perpendicular and arrive at the KV x. In fact you can extrapolate the line above 100 deg C or below 40 deg C and still have an accurate KV for that temperature.

Hussam Adeni
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