## 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.