Kinematic viscosity is the absolute viscosity of a fluid divided by its density at the temperature of measurement. It is a measure of the fluid's resistance to flow under gravity, as specified in ASTM D 445.
Saybolt Universal Seconds refers to the efflux time of 60 mL of a fluid through a Saybolt Universal viscometer at a given temperature, as described in ASTM D 88.
temperature factor for SUS =
= 1 + (((temperature in degrees Fahrenheit) – 100) * 0.000064)
where:
• Different sources give different values for the factor expressed as 0.000064 above (one is 0.000061 and another is 0.000034).
• I am not sure the temperature range for which the equation is valid, but it works over the range of 100°F to 210°F.
The same kinematic viscosity in centistokes will be seen by a fluid:
(1) with a viscosity of (X) SUS at 100°F
(2) with a viscosity of (X * (temperature factor)) SUS at a higher temperature
The conversion between centistokes and SUS at 100°F is 4.635:
value for fluid in SUS at 100°F =
= (centistokes) * 4.635
value for fluid in SUS at higher temperature =
= (centistokes) * 4.635 * (temperature factor)
Significance of SUS:
• In the range of 1 to 100 SUS at 100°F, the lower the SUS the higher the potential for an aspirated hydrocarbon to cause a chemical pneumonitis.
