FLANGE GP-EXHAUST 2W7850 - Caterpillar

(in solution), "free and dispersed" (mixed), and "free and settled" (at the bottom of the tank).
Most diesel fuels have some dissolved moisture. Just like the moisture in air, the fuel can hold only a specific maximum amount of moisture at any one temperature, and this amount becomes less as the temperature is lowered. For example, a fuel with 100 ppm (parts per million) (0.010%) of water in solution at 65°F (17°C), can possibly hold only 30 ppm (0.003%) at 40°F (4°C). Any moisture in the fuel which is more than the maximum amount that can be dissolved, becomes "free and dispersed" as very small drops of water mixed in the fuel. Since the water is heavier than the fuel, it will slowly become "free and settled" at the bottom of the tank. In the above example, when the fuel temperature was lowered from 65°F (17°C) to 40°F (4°C), 70 ppm of water became "free and dispersed" in the fuel. The small drops of water cause a "cloudy" look in the fuel and, if the change in temperature is slow, the water can settle (go down) to the bottom of the tank. When the fuel temperature is lowered rapidly to a temperature below freezing, the moisture that comes out of solution changes to very fine particles of ice (like snowflakes) instead of small drops of water. These ice particles are lighter than the fuel, and will not settle to the bottom of the tank. When this type of moisture is mixed in the fuel, it will fill the filters in the same way as wax particles do when the fuel is below the cloud point. If a filter is filled, and fuel flow stops, the only way to find the cause is to remove the filter, cut it open, and inspect it before it becomes warm. This inspection will show the filter is filled with particles of either ice or wax.
The moisture which is "free and settled" at the bottom of the tank can become mixed with the fuel by the force of pump action when fuel is put into, or taken out of the tank. This becomes "free and dispersed" water, and can cause ice in the filters, but it can cause other filter problems at any temperature. Generally, the same force that mixes the water into the fuel will also mix dirt and rust from the bottom of the tank with the water. The result is a dirty mixture of fuel and water which can also fill the filters and stop fuel flow.
Modification Of Fuel Characteristics
CETANE NUMBER: The cetane number of a fuel can be changed if the fuel is mixed with a fuel that has a different cetane number. Generally, the cetane number of the mixture will be in direct relation to the ratio of the fuels that were mixed. Your fuel dealer is the best source of cetane information.
A different method to improve the cetane number of a fuel is with the use of additives.