DIESEL FUELS & DIESEL FUEL SYSTEMS

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Diesel Fuels & Diesel Fuel SystemsApplication and Installation Guideeach situation requires anassessment. Jacket-water heatedfuel filters, available from fuelequipment suppliers, are oftensuitable for heating the crude. Ifthis is not appropriate for youapplication, an external heatingsystem will be necessary.2. The crude oil must not have toohigh a viscosity. For maximumlife and minimum maintenance ofthe fuel pumping and injectionsystems, the viscosity of thecrude oil in these systems shouldbe within 1.4 to 20 cSt at 104°F(40°C). If the crude’s naturalviscosity is higher than this, itmay be heated or diluted toreduce it. The degree of heatingrequired will vary from one crudeoil to another and will have to beestablished in each case. Anothermethod of reducing viscosity isto blend the original crude with asufficient amount of lighterdistillate material. Again, theblending proportions would haveto be determined for each crudeoil.3. The crude must have a cetanenumber of at least 40. Thisbrings its distillationcharacteristics into the picture.The cetane number should bedetermined by actual engine testbecause calculated numbers ofcrude oils are unreliable. Thecetane number of a crude oil is afunction of its composition.Crude is generally subdivided intofractions by boiling temperatures.The combination of the gasolineand naphtha fractions, whichhave low cetane numbers, shouldnot exceed 30% of the totalcrude. The kerosene, distillateand gas oil fractions combinedshould make up at least 30% ofthe total because they have highcetane numbers.4. Another problem created byhighly volatile crude oils (lowinitial boiling points) is vaporlocking of the fuel system. Thissituation can be handled by an“air eliminator.” This, in somecases, can be an ordinary floattypesteam trap inverted, but itshould be made of corrosionresistantmaterials. It should belocated after the auxiliary filters.If the engine is stoppedoccasionally and allowed to cool,coagulation may build up in thisvapor trap and cause it to beinoperative.5. The proper oil changerecommendation must be made ineach case. Many crude oilscontain large amounts of materialthat accelerate lube oildeterioration. For this reason, thestandard change period withrecommended oils should bereduced by one-half. From thispoint, the length of change periodwith crude is determined bysulfur content the same as withdistillate fuels. With 0.4-1.0%sulfur, the change period shouldagain be reduced by one-half.When sulfur content exceeds1.0%, still further reduction isrecommended. In many cases, itmay be desirable to install alarger capacity lube oil system toPage 50©2005 Caterpillar®All rights reserved.
Application and Installation GuideDiesel Fuels & Diesel Fuel Systemsavoid short oil changes. The useof Caterpillar S•O•S SM , is stronglyrecommended.Crude Oil MaintenanceIntervalsEngine inspection intervals shouldbe reduced by 50% when usingcrude oil as fuel, and maintenanceroutines should be modified basedon the results of these increasedinspections.Crude Oil Settling TanksA great deal of sludge can beremoved from crude oil by propersettling. A recommended settlingsystem consists of two conebottomedtanks, Figure 11, eachholding a little more than four daysusable supply of fuel.Sludge in the bottom third isdiscarded before refilling. The tanksmust be housed in a heated building,and each fitted with heating coils.Immediately after filling, hot wateris circulated through the heating coiluntil the tank is heated to 100°F(38°C). The heat is then shut offand the fuel allowed to settleundisturbed for four days.During this time, fuel is being usedfrom a second tank. Temperatureinside the settling tank buildingshould be maintained above 70°F(21°C), and the tanks must bevented outside the building.A two-day supply of diesel fuelshould be maintained for emergencyuse. This supply can also be used tostart and stop engine when thecrude oil fuel is highly viscous orheavy with paraffins.Figure 11©2005 Caterpillar®All rights reserved. Page 51
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DIESEL FUELS & DIESEL FUEL SYSTEMS

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