Diesel Fuels in Marine Operations

There are a variety of diesel engines Used in marine service, ranging from small life boat and generator engines up to high horsepower, low-speed, main propulsion units having cylinder diameters of 30 in. or more. In a particular ship, moreover, several sizes of engines are generally used, one for propulsion, and others for the various auxiliary uses. In order to present a picture of the fuels in use, together with the trends and problems encountered, it is expedient to make some arbitrary grouping of the engines employed. Such a grouping, based on the rated revolutions per minute of the engines, is as follows: Group A—1200 rpm and higher. The group largely consists of “automotive” type, high-speed engines for auxiliary uses, as well as main propulsion on small craft. Group B—700 to 1200 rpm. This group consists of engines of intermediate horsepower range used for propulsion as well as auxiliary services. Group C—365 to 700 rpm. This group includes large auxiliaries as well as main propulsion units of intermediate horsepower range. Group D—365 rpm and lower. Most of the main propulsion engines of deep sea vessels fall in this category. Some large auxiliaries also fall in this category. In considering the fuels employed in marine service, one finds a variety of names being used to describe products available at various ports aud bunkering points. However, taken generally the fuels may be placed into four categories as follows: Type I—A light distillate material similar to ASTM Grade No. 1-D classification. Type II—A distillate of about the characteristics of ASTM Grade No. 2-D. Type III—A heavy distillate, or blend of distillate, with some residual material. Type IV—Various blends of residual with distillate material, generally classed as light bunker fuel oils. Also included in this group are the heavy bunker fuel oils commonly called Bunker C, or boiler fuel. Some measure of the characteristics of types II and III fuels is shown in Table I. Samples of mam engine fuel, taken from ships arriving in the port of New York, show the characteristics for a representative number from the survey. These fuels were obtained at a variety of ports over the world. Incidentally since all of these ships carried only one fuel, the auxiliaries also operated with the fuel shown. Lifeboat engines and the emergency generators had their own supplies of either a type I or type II fuel.