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Use Clean Fuel in Oil Engines Latest Designs Permit Use of Heavier Fuel—Impurities Must be Removed—-Cheaper, Easier to Obtain and has Greater Heat Value O DIFFERENCE of opinion N should exist in regard to the distinct advantages to be gained by using heavier boiler fuel oils in oil engines instead of being limited entirely to the use of the lighter oils, provided heavy oil can be used with reasonable facility and without detriment to the wearing parts of the engine. The off hand and gen- eral impression is that it cannot be done. It may be worth while to look into this question to see whether this impression is well founded. Heavy fuels are lower in price and, by volume, on which basis they are sold, have a somewhat greater heat value. The lighter oils are not always readily available on the market. Thus it is desirable that an engine be able to burn whatever fuel oil may be procured at any port the ship may enter. The motor ship that is com- pelled to burn only lighter oils is frequently forced to carry a large supply and so sacrifices valuable cargo space. Representatives of the oil en- gine industry, users of oil engines, and oil companies, indicate a marked pref- erence for fuel ranging from 24 de- grees to 36 degrees Baume for oil en- gine use. In a few instances a lower limit of 20 degrees Baume is ac- cepted as satisfactory. A few man- ufacturers express the belief that their engines will operate effectively on any burnable fuel. Cheaper And Easily Obtained Considering that the heavier oils are cheaper and are almost always easier to obtain in quantity than the lighter Diesel fuels, what are the rea- sons for the almost universal de- mand for oils between 24 to 36 de- grees Baume for Diesel fuel? In the past, certain well founded objections have been advanced to the use of the heavier fuels in Diesel engines. These objectives may be enumerated, 1, dif- ficulties in handling oils that are vis- cous at normal temperatures, 2, igni- tion difficulties, 3, difficulties in burn- ing oil after ignition, 4, difficulties caused by the presence of small quan- tities of impurities in the oil. The difficulties listed under the first three headings can, and are being overcome in the design of engines -and in fuel storage and handling sys- BY LEE H. CLARK Engineer, Sharples Specialty Co. tems, and by an understanding of the proper variations necessary in opera- tion to change engines from the use of the lighter to the heavier fuels. It is not possible to overcome the diffi- culties due to impurities in the oil burned in the same manner. The re- moval of impurities constitutes an en- tirely separate problem. Failure to appreciate this distinction has been responsible for attributing many troubles caused by poor operation and CENTRIFUGE OF ENCLOSED PRESSURE TYPE SUITABLE FOR CENTRIFUGING OILS AT HIGHER TEMPERATURES design to foreign matter present in the heavier oils. There is ample evidence that many engine manufacturers have solved the problem of producing Diesel engines that are mechanically capable of burn- ing the heavier oils without difficulty. The majority of the larger engines now being put in service are adapted to’ burn the heaviest fuels, if such fuels are sufficiently free from impur- ities. The same is not true of some types of engines, particularly those of older design, and it is illogical to ex- pect an engine not designed for them to operate effectively upon the heavier 291 oils, even though such oils are well purified before use. The preference that has been noted for the lighter fuels may be explained on the basis of their relative freedom from handling difficulties and from excessive trouble due to impurities. The high Baume gravity oils are nor- mally of low viscosity. They are suf- ficiently mobile for pumping, at nor- mal temperatures. Compared with the low Baume gravity fuels, they are not as apt to hold mechanical impurities in suspension, first, because of their lower viscosity, secondly, because there are greater differences in the specific gravities of the oils and those of the impurities. Purification Has Advantages As a result of these conditions, a large part of any water and solid im- purities settle by gravity while the lighter oils are in storage tanks. Var- ious types of filters have been used to remove impurities that do not set- tle by gravity. Centrifugal treatment is, however, more efficient than either gravity sedimentation or filtration, as can be shown by the impurities re- moved centrifugally from oil even after the two former methods of puri- fication have been used. Even where it is necessary to heat the lighter oils to obtain a more ready purifica- tion, moderate temperatures are suffi- cient. Experience has proven that oil, be- tween the limits of 24 to 86 degrees Baume will burn well in most engines without giving rise to undue mainte- nance charges. It should not be as- sumed from this, however, that an effi- cient purification device cannot be used to advantage to still further im- prove combustion and eliminate en- gine wear. The centrifugal is the most efficient apparatus for this serv- ice since it removes impurities more completely than either the filter or gravity settling tanks. Its operation is not complicated by filter media and does not result in accumulations of sludge or emulsions that result in oil loss, that are difficult to handle and of which it is troublesome to dis- pose. The desire to use oil of any gravity in Diesel engines has probably done more to impress the oil engine user