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

S0300-A6-MAN-060CHAPTER 2OIL CHARACTERISTICS AND BEHAVIOR2-1 INTRODUCTIONThe behavior, spread and impact of oil on the water depends on the quantity of oil, the marineenvironment, prevailing weather and most importantly, the physical and chemical properties ofthe substance. Response actions must be tailored to the conditions of the spill. The type of oil andits characteristics must be identified as the first step of a timely and adequate spill response.2-2 CHEMICAL AND PHYSICAL CHARACTERISTICS OF OILThe term oil includes crude petroleum and refined petroleum products, as well as nonpetroleumoils (animal and vegetable oils). Both chemical and physical properties are important in assessingspill impact and developing appropriate response tactics. The chemical properties of concern areboiling point range, solubility in water, aromatic content and the presence of dissolved nonhydrocarboncompounds. The physical properties of greatest concern are density, viscosity, pour point,flash point and surface tension. The importance of each of these properties is discussed in the followingparagraphs. Appendix F gives pertinent properties of petroleum and nonpetroleum oils.Petroleum products are refined in a distillation process (boiling and vapor recovery) that separatesfractions from the crude oil stock. The fractions or ends, with the lowest boiling points boil offand distill early in the refining process and are called light ends because of their characteristicallylow density. The fractions with higher boiling points, that distill later, are called heavy ends.Those that remain after all the lighter ends have been boiled off are called residuals. Like crudeoil, refined products are not simple compounds, but mixtures of hydrocarbon compounds that boil(and distill) within a given temperature range. Figure 2-1 shows a typical fraction separation.2-2.1 Physical Characteristics. As hydrocarbon mixtures, the physical properties of oil are acomposite of the physical properties of the various constituent compounds. If the relative proportionsof the constituent compounds change, through evaporation, dissolution or other processes,the composite properties will also change. Several physical properties that affect behavior ofspilled oil on both land and water are viscosity, pour point, density or specific gravity, surface tension,flash point and emulsibility.2-2.1.1 Density and Specific Gravity. Density is the mass per unit volume and is expressed aspounds per cubic foot, grams per cubic centimeter or similar units. Density is expressed alternativelyas specific gravity, the ratio of the density of a material to the density of fresh water at a certaintemperature-usually 60°F. The specific gravity of water (at 60°F) is therefore 1.0. Most oilshave a specific gravity of less than 1.0, which means that the material is lighter than and floats onfresh water. However, some oils have a specific gravity greater than 1.0 and will sink in freshwater. The specific gravity of saltwater is 1.025. A few oils have specific gravities greater than1.025 and will sink in saltwater. The density of crude oils and petroleum products is also2-1