Normally, diesel fuel oils for use in the Submarine Service are purchased by the Bureau of Supplies and Accounts. | 5 DIESEL ENGINE FUEL SYSTEMS A. DIESEL FUELS 5A1. General. Normally diesel fuel oils for use in the Submarine Service are purchased by the Bureau of Supplies and Accounts. At the time of delivery the diesel fuel oils are inspected to make sure that they meet the specifications set up by the Bureau of Ships. However emergencies occasionally arise both in the supply and in the handling of diesel fuels that make it imperative for operating engineering personnel to have at least a fundamental knowledge of the requirements for diesel fuel oil. 5A2. Cleanliness. One of the most important properties necessary in a diesel fuel oil is cleanliness. Impurities are the prime sources of fuel pump and injection system trouble. Foreign substances such as sediment and water cause wear gumming corrosion and rust in the fuel system. Diesel fuel oil should be delivered clean from the refinery. However the transfer and handling of the oil increase the chance of its picking up impurities. The necessity for periodic inspection cleaning and care of fuel oil handling and filtering equipment is emphasized under the subject of maintenance for each system. 5A3. Chemistry of diesel fuel oil. Diesel fuel oils are derived from petroleum more generally known as crude oil. All crude oils are composed of compounds of carbon and hydrogen known as hydrocarbons. The structure of the oil is made up of tiny particles called molecules. In crude oil a molecule consists of a certain number of atoms of carbon and a certain number of atoms of hydrogen. The ratio between carbon and hydrogen atoms in a molecule determines the nature of the crude oil. Crude oil is separated into various products by a process known as stopped at any point leaving a residue of a heavier viscous liquid. This residue may be cracked in cracking stills by the application of heat and pressure in the presence of a catalyst. This cracking process may be controlled so as to get products of almost any given type of hydrocarbon molecular
