ASTM D2161 Standard Practice for Conversion of Kinematic Viscosity ot Saybolt Universal Viscosity or to Saybolt Furol Viscosity
5. Procedure for Conversion to Saybolt Universal Viscosity
5.1 Convert kinematic viscosities between 1.81 and 500 mm2/s (cSt) at 100°F, and between 1.77 and 139.8 mm 2/s (cSt) at 210°F, to equivalent Saybolt Universal seconds directly from Table 1 (see Appendix X1, Example 1).
NOTE 2 - Obtain viscosities not listed, but which are within the range given in Table 1, by linear interpolation (see Appendix X1, Example 2).
5.2 Convert kinematic viscosities greater than the upper limits of Table 1 at temperatures of 100 and 210°F to Saybolt Universal viscosities as follows (see Appendix X1, Example 3):
Saybolt Universal seconds = centistokes x B
where B = 4.632 at 100°F = 4.664 at 210°F.
5.3 At temperatures other than 100 or 210°F, convert kinematic viscosities to Saybolt Universal viscosities as follows (see Appendix X1, Example 4):
NOTE 3 - The multipliers for Saybolt Universal seconds in Eq 2 are given as Factor A in Table 2 for a range of temperatures.
5.4 Since the relationship between Saybolt and kinematic viscosities is linear above 75 mm2/s (cSt), kinematic viscosities above this limit may be converted to Saybolt Universal viscosities at any temperature between 0 and 350°F by use of Eq 1 (4.2), selecting the proper factor for B from Table 2 (see Appendix X1, Example 5).
6. Procedure for Conversion to Saybolt Furol Viscosity
6.1 Convert kinematic viscosities between 48 to 1300 mm2/s (cSt) at 122°F, and between 50 and 1300 mm2/s (cSt) at 210°F, to equivalent Saybolt Furol seconds directly from Table 3 (see Appendix X1, Examples 6 and 7).
NOTE 4 - Viscosities not listed, but which are within the range given in Table 3, may be obtained by linear interpolation (see Appendix X1, Example 8).
6.2 Convert kinematic viscosities above 1300 cSt to equivalent Saybolt Furol seconds by use of the following equations (see Appendix X1, Example 9):
Saybolt Furol seconds at 122°F = 0.4717 x mm2/s (cSt) at 122°F
Saybolt Furol seconds at 210°F = 0.4792 x mm2/s (cSt) at 210°F
7. Procedure for Computer Calculation
7.1 Table 1 and Table 3 were computed by fitting a smooth curve to the original experimental data points. The derived equations are given as follows for the convenience of those who wish to use a computer for conversion rather than refer to the tables:
7.2 (Eq 5) and (Eq 6) and Table 1 are limited to values of Saybolt Universal of 32.0 s and above.
7.3 (Eq 7) and (Eq 8) and Table 3 are limited to values of Saybolt Furol of 25.1 s and above.
8. Supplementary Conversion Equivalents
8.1 The following units and equivalents are frequently used in connection with viscosity conversions:
poise = cgs unit of absolute viscosity.
centipoise = 0.01 poise.
stokes = cgs unit of kinematic viscosity.
centistokes = 0.01 stokes.
centipoise = centistokes x density (at temperature under consideration).