V. SUPPLY SYSTEM CONSIDERATIONS
C. Viscosity
Basic metric viscosity units are the poise (absolute/dynamic viscosity) and the stokes (kinematic viscosity). More customary expression of these units are centipoise and centistokes respectively, each equal to 1/100th the of basic metric viscosity unit. The relationship between the English units for medium viscosity liquids, SSU (Saybolt Universal Seconds), and metric absolute viscosity is:
n (absolute viscosity, centistokes) = 0.22 (SSU) - 180
(SSU)
Introducing the mass density of the liquid (r) allows the expression of the relationship between absolute viscosity to Kinematic viscosity as follows:
m (Kinematic viscosity, centipoise) = rn
Example 10:
Find viscosity in centistokes (n) and centipoise (m) of a liquid with S.G. = 0.8 with a viscosity of 500 SSU.
n = 0.22 (500) - 180 = 109.64 centistokes
500
Then,
m = 0.8 x 109.64 = 87.71 centipoise
The basic pump speed, and its relationship with various ranges of liquid viscosity, are discussed in further detail in Appendix A.
