Fuel system deposits

This formulation is designed as a complete treatment, providing improved atomization and combustion, sludge dispersancy, demulsifi-cation of water from oil, prevention of bacterial slimes at the water-oil interface, reduced cold-end corrosion, and less fuel system deposits. 

Total sediment includes measurement of insoluble fuel asphaltenes, inorganic compounds, catalyst fines, and other compounds which can be filtered from the fuel. This value is important because sediment may plug filters and strainers, overload centrifuge systems, and contribute to fuel system deposits. 

The result of this testing provides information on whether fuel components are susceptible to attack by oxygen. If fuel components do react with oxygen, then further degradation of the fuel can be expected. The final result could be gum formation, fuel discoloration, and fuel system deposits. 

Detergents minimize fuel system deposits at low concentrations, and at high concentrations can remove deposits that have already formed. Detergents are molecules that have a highly polar end group and a nonpolar hydrocarbon tail. A conventional amino amide type detergent is shown in... 

The fuel systems of ground-based turbiaes are far less critical, siace coolants other than fuel can be used and fuel lines can be well iasulated. The tendency for deposit formation ia fuel is not a concern ia ground systems. 

Deposition and fouling can occur in the fuel system and in the hot section of the turbine. Deposition rates depend on the amounts of certain compounds contained in the fuel. Some compounds that cause deposits can be removed by fuel treating. 

Carbon residue, pour point, and viseosity are important properties in relation to deposition and fouling. Carbon residue is found by burning a fuel sample and weighing the amount of earbon left. The earbon residue property shows the tendeney of a fuel to deposit earbon on the fuel nozzles and eombustion liner. Pour point is the lowest temperature at whieh a fuel ean be poured by gravitational aetion. Viseosity is related to the pressure loss in pipe flow. Both pour point and viseosity measure the tendeney of a fuel to foul the fuel system. Sometimes, heating of the fuel system and piping is neeessary to assure a proper flow. 

Fuel system fouling is related to the amount of water and sediment in the fuel. A by-product of fuel washing is the desludging of the fuel. Washing rids the fuel of those undesirable constituents that cause clogging, deposition, and corrosion in the fuel system. The last part of treatment is filtration just prior to entering the turbine. Washed fuel should have less than. 025% bottom sediment and water. 

Detergents/deposit control additives Help prevent deposit buildup on fuel system parts such as carburetors, fuel injectors, intake valves, valve seats, and valve guides some additives will remove existing deposits... 

Jet fuels are blended primarily from straight-run distillate components and contain virtually no olefins. Aromatics in jet fuel are also limited. High aromatic content can cause smoke to form during combustion and can lead to carbon deposition in engines. A total aromatic content >30% can cause deterioration of aircraft fuel system elastomers and lead to fuel leakage. 

Alumina, iron, nickel, silica, sodium, and vanadium are examples of compounds which can be found in residual fuel ash. If the vanadium content of residual fuel is high, severe corrosion of turbine blades can occur and exhaust system deposit formation can be enhanced. Vanadium-enhanced corrosion can occur at temperatures above 1200°F (648.9°C). 

Whenever deposits from fuel systems are analyzed and are found to contain high levels of iron, corrosion is probably occurring somewhere within the fuel system. 

When water pH is <6, iron corrosion and the formation of corrosion products such as colloidal ferric hydroxide can result. Colloidal ferric hydroxide, however, is difficult to detect and difficult to remove through filtration. Fuel containing these particles appears bright and clear. Only about 1 micron in diameter, colloidal ferric hydroxide compounds can pass through fuel filters and deposit onto fuel system components. Further system corrosion can follow. 

Fuels such as diesel fuel and heating oil are sometimes stored in large tanks for extended periods of time. At temperatures below the cloud point of the fuel, wax can form and fall from solution. Accumulated wax within fuel systems can deposit onto component parts and settle into areas of low turbulence. Problems such as filter plugging and flow limitations can be due to accumulated wax. 

A variety of fuel performance problems can be directly linked to the presence of olefinic compounds in a fuel. Problems such as darkening of fuel color, gum and sludge formation, and combustion system deposits can be directly linked to the presence of olefins. 

Other elements such as boron and silicon can be found in fuel and oil system deposits. They can originate from the following sources ... 

Paraffins function poorly as a solvent for some organic compounds. This fact can have various consequences. For example, gums, deposits, and fuel degradation products will not be dissolved or held in solution by high-paraffin-content fuels. As a result, gums and degradation products will fall from solution and settle onto fuel system parts such as storage tank bottoms and fuel system lines. The KB value for selected petroleum products is provided in TABLE 5-4. 

The amount of carbon present in fuel components can be correlated with a tendency to form deposits in fuel systems. Although the use of various detergent and dispersant additives helps to minimize deposit formation, the carbon residue value is still quite useful. 

High-carbon-residue values for marine diesel fuel, marine gas oil, and heavy marine bunker fuel can contribute significantly to exhaust system deposit problems. Deposit formation on exhaust ports and exhaust turbines have been linked directly to high carbon residue in fuel. 

Some distillate fuel stabilizers possess dispersant-like properties. By acting as a dispersant, any sludge or deposit-like component which may form can be suspended in the fuel and maintained as a soluble compound. As a result, deposits do not accumulate onto fuel system components, but remain dispersed in the fuel. However, due to this dispersing action, the fuel may appear dark in color. 

Mechanical components used in fuel systems such as pumps, valves, and bearings may contain copper or copper-containing alloys. As a fuel system component, copper is especially undesirable because it acts as a catalyst in promoting the oxidation of fuel paraffins to oxygen-rich, gumlike deposits. The following reaction sequence represents how copper ions can catalyze the oxidation and degradation of hydrocarbons. 

Corrosion inhibitors used to protect fuel system components such as storage tanks, pipelines, and combustion system equipment are typically dissolved in the fuel and delivered to the metal surface with the fuel. The inhibitor is deposited onto exposed metal surfaces as the fuel passes through the fuel distribution and handling system. 

Fuel olefins have been implicated as the primary cause of deposits in gasoline fuel injectors and carburetors. High-boiling-point, high-molecular-weight aromatic components have also been shown to contribute to intake system deposit and gum formation. Once formed, other compounds in the fuel can adhere to these deposits to form an amorphous-type deposit. 

For this reason, extreme care should be taken when using high concentrations of dehazers to clear fuel of water haze. The excess dehazer may also act to solubilize deposits which are present within a fuel system. The deposits may then be carried with the fuel throughout the distribution system. 

Some stabilizer formulations can function as dispersants to prevent the settling and accumulation of deposits in fuel systems. If fuel containing a stabilizer with dispersant properties is stored or transported in a system having existing deposits, the dispersant would act to break loose and suspend the deposits into the fuel. The resulting fuel would appear dark in color. 

Deposit formation on fuel system components (i.e., line varnish, valve deposits, etc.)... 

HSD Stabilizer (Diesel Stabilizer) additive is a multicomponent, oil soluble formulation, specially designed to maintain the total sediments level in diesel fuel within the specified limits, as per ISO 1460 1995. The additive will ensure that the diesel does not deteriorate on storage and the fuel system is protected from deposit formation and corrosion. The additive consists of three major components, namely ... 

Photon correlation spectroscopy measurements for growth rate, together with a quartz crystal microbalance for mass deposition, have been integrated into a single platform to permit simultaneous in-situ real time measurement at times and temperatures representative to those found in aviation fuel systems [323],... 

---