MIL-STD-1518E
g. Defueled product shall not be serviced to U.S. government aircraft unless tested and meets the limits of Table III. Defueled commingled product meeting the requirements of Table III shall not be serviced to aircraft which require JP-5 when the flash point is below 60°C (140°F).
4.3 Contamination. Fuel contamination is generally categorized as chemical, biological or material.
a. Chemical Contamination. This type of contamination results from the mixing of two hydrocarbon fuels or contact of other chemicals with the fuel. The chemical and physical properties of the fuel are affected. This type of contamination is usually detected by laboratory testing. Chemical contamination is prevented by isolating fuels in separate handling systems or positive physical separation between systems; and by alertness of operation personnel. Carelessness is the major contributing factor for this type of contamination.
b. Biological Contamination. This contamination results from growth of bacteria and fungi. The microorganisms are found in water deposits in the systems. This can result in contamination of aircraft by plugging filters, causing fuel quantity probe malfunctions, and contributing to corrosion of integral fuel tanks. To most effectively control biological contamination, remove water from the system.
c. Material Contamination. Material contamination of fuels usually consists of water or sediment.
4.4 Water. Water is usually present in all systems. It may be delivered to tanks during receipt of product or through leaks that permit entry of surface or ground water. It may also be introduced as vapor which condenses within the system. Both fresh and salt water can be found in fuel systems. It may be present as dissolved, entrained, or free water.
4.4.1 Dissolved Water. Fuel always contains some dissolved water. The amount of water that is in solution, and can be retained in solution, is dependent upon the temperature and chemical composition (percent aromatics) of the fuel.
4.4.2 Entrained W ater. This is free water that is present in suspension in the fuel in the form of extremely fine droplets. Small amounts, up to 30 PPM, usually are not visible to the naked eye, but increased percentages create a milky haze or cloud in the fuel. Water can become entrained in the fuel by condensation of the moisture in the atmosphere or in the vapor/air mixture in a tank resulting from a reduction in the ambient temperature. Most entrained water will settle out of fuel, provided the fuel does not contain contaminants or materials such as surfactants, which hold water in suspension. Entrained water is removed by the coalescing action of filter/separators and/or water absorption filters installed in the fuel system.
4.4.3 Free Water. All water that is not in solution in the fuel is a form of free water. Usually, the term free water is used to indicate water that has settled out of the fuel or has been coalesced into large droplets for removal from the system.
4.5 Sediment. Sediment appears as dust, powder, grains, flakes, and stains. Sources of solids or sediment include storage tanks, ferrous vessels or containers, filter or filter/separator elements, valves, pumps, meters, pipelines, hoses, grease, gaskets, diaphragms, and seals. Removal of particles is accomplished with the use of screens, filters and filter/separators.
4.6 Recycled, recovered, or environmentally preferable materials. Recycled, recovered, or environmentally preferable materials should be used to the maximum extent possible, provided that the material meets or exceeds the operational and maintenance requirements, and promotes economically advantageous life cycle costs.
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