U.S. Navy Ship Salvage Manual Volume 6 - Oil Spill Response

S0300-A6-MAN-060Figure 2-1. Typical Petroleum Distillation Fractions.expressed as American Petroleum Institute (API) gravities or degrees API. API gravities are basedon the arbitrary assignment of a gravity of 10 degrees to fresh water. Liquids with higher gravitiesare lighter than water; those with lower API gravities are heavier than water. API gravities are calculatedby:Oils having low density (high API gravity) generally have low viscosities and contain a high proportionof volatile compounds. Conversions between specific gravity, API gravity and density aregiven in Chapter 1 and Appendix B of the U.S. Navy Ship Salvage Manual, Volume 5, S0300-A6-MAN-050.2-2.1.2 Viscosity. Viscosity is a measure of the resistance to flow or the internal friction of theproduct. Kinematic viscosity is expressed in centistokes (cSt) and varies with temperature formost liquids. The viscosity of water at 68°F is approximately 1.00 cSt. Viscosity may also be tabulatedin other units:• Absolute or dynamic viscosity is given in units of Poise. Absolute viscosity is kinematicviscosity multiplied by density.• Viscosity is sometimes expressed as the number of seconds required for a specifiedquantity of oil to flow through an orifice of specified size. More viscous oils flow moreslowly and have higher values. There are several viscosity scales based on this concept,2-2