Specific gravity petroleum products

API gravity. The specific gravity of petroleum or petroleum products is often expressed in terms of degrees API on a scale defined by... 

What size of orifice would give a pressure difference of 0.3 m water gauge for the flow of a petroleum product of specific gravity 0.9 at 0.05 m3/s in a 150 mm diameter pipe ... 

In the SI system, the theoretical unit of v is m2/s or the commonly used Stoke (St) where 1 St = 0.0001 m2/s = 100 cSt = 100 centiStoke. Similarly, 1 centiStoke = 1 cSt = 0.000001 m2/s = 0.01 Stoke = 0.01 st. The specific gravity of water at 20.2°C (68.4°F) is almost 1. The kinematic viscosity of water at 20.2°C (68.4°F) is for all practical purposes equal to 1 cSt. For a liquid, the kinematic viscosity will decrease with higher temperature. For a gas, the kinematic viscosity will increase with higher temperature. Another commonly used kinematic viscosity unit is Saybolt universal seconds (SUS), which is the efflux time required for 60 mL of petroleum product to flow through the calibrated orifice of a Saybolt universal viscometer, as described by ASTM-D88. Therefore, the relationship between dynamic viscosity and kinematic viscosity can be expressed as... 

The specific gravity is the ratio of weight of equal volumes of a substance to that of another substance usually water. For petroleum products it is customary to measure the ratio at 15.6 °C (60 °F)... 

Viscosity and Specific Gravity of Common Petroleum Products... 

Petroleum is typically described in terms of its physical properties (such as density and pour point) and chemical composition (such as percent composition of various petroleum hydrocarbons, asphaltenes, and sulfur). Although very complex in makeup, crude can be broken down into four basic classes of petroleum hydrocarbons. Each class is distinguished on the basis of molecular composition. In addition, properties important for characterizing the behavior of petroleum and petroleum products when spilled into waterways or onto land and/or released into the air include flash point, density (read specific gravity and/or API gravity), viscosity, emulsion formation in waterways, and adhesion to soil. 

The data from the density (specific gravity) test method (ASTM D1298 IP 160) provides a means of identification of a grade of naphtha but is not a guarantee of composition and can only be used to indicate evaluate product composition or quality when used in conjunction with the data from other test methods. Density data are used primarily to convert naphtha volume to a weight basis, a requirement in many of the industries concerned. For the necessary temperature corrections and also for volume corrections, the appropriate sections of the petroleum measurement tables (ASTM D1250 IP 200) are used. 

Density (the mass of liquid per unit volume at 15°C) and the related terms specific gravity (the ratio of the mass of a given volume of liquid at 15°C to the mass of an equal volume of pure water at the same temperature) and relative density (same as specific gravity) are important properties of petroleum products as they are a part of product sales specifications, although playing only a minor role in studies of product composition. Usually, a hydrometer, pycnometer, or digital density meter is used for determination in all these standards. 

The density specific gravity) of coke has a strong influence on future use and can affect the characteristics of the products such as carbon and graphite. The density (specific gravity) of coke can be measured conveniently by use of a pycnometer. In the test method (ASTM D5004), the mass of the sample is determined directly and the volume is derived by determining the mass of hquid displaced when the sample is introduced into a pycnometer. Oil or other material sprayed on calcined petroleum coke to control dust will interfere. Such oil can be removed by flushing with a solvent, which must be completely removed before the density determination. 

Petroleum products expand when heated. The coefficient of expansion for most petroleum products will vary and is dependent upon the specific gravity or API of the product. A listing of expansion coefficients for petroleum products is provided in TABLE 4-3. 

As previously discussed, the coefficient of expansion/contraction for petroleum products is dependent upon specific gravity. As fuels cool, their volume will be reduced. 

Fuel Oils Refined petroleum products having specific gravities in the range of 0.85 to 0.98 and flash point temperatures above 55 °C. This includes auto diesel, industrial heating fuels, various bunker fuels, furnace fuels. Refer to Chapter 4 for specific examples and discussion of properties. Fuel Value Refers to the amount of potential energy that can be released by a fuel during combustion. Expressed in units of BTUs per pond of fuel. Examples are asphalt (17,158 BTU/lb typical value), LPG (18,000 BTU/lb), wood shavings (8,250 BTU/lb). 

Fuel Oils Refined petroleum products having specific gravities in the range from 0.85-0.98 and flash points greater than 55°C includes furnace, auto diesel, and stove fuels, plant or industrial heating fuels and various bunker fuels. 

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