PRINCIPLES OF NAVAL ENGINEERING 



connected to the transfer mains so that the 

 filling lines and deck connections can be used 

 both for receiving and for discharging fuel oil. 

 Pressure filling systems operate with a mini- 

 mum pressure of approximately 40 psi at the 

 deck connections. 



In general, the filling and transfer system 

 consists of large mains running fore and aft; 

 transfer mains; cross-connections; risers for 

 taking on or discharging fuel oil; fuel oil booster 

 and transfer pumps; and lines and manifolds 

 arranged so that the fuel oil booster and trans- 

 fer pumps can transfer oil from one tank to 

 another and, when necessary, can deliver fuel 

 oil to the suction side of the fuel oil service 

 pumps. 



The fuel oil tank stripping system serves to 

 clear fuel oil storage tanks and fuel oil service 

 tanks of sludge and water before oil is pumped 

 from these tanks by fuel oil booster and transfer 

 pumps or by fuel oil service pumps. The strip- 

 ping system is connected through manifolds to 

 the bilge pump or, in some installations, to 

 special stripping system pumps. The stripping 

 system discharges the contaminated oil, sludge, 

 and water overboard or to the contaminated oil 

 settling tanks. 



The fuel oil service system includes the fuel 

 oil service tanks, a service main, manifolds, 

 piping, fuel oil service pumps, meters, heaters, 

 strainers, burner lines, and other items needed 

 to deliver fuel oil to the boiler fronts at the re- 

 quired pressures and temperatures. The fuel oil 

 service system used on any ship depends partly 

 on the type of fuel oil burners^ installed on the 

 boilers. Figure 9-21 illustrates schematically 

 a fuel oil service system typically found on ships 

 having double-furnace boilers and straight- 

 through-flow atomizers in the fuel oil burners. 

 Figure 9-22 shows the fuel oil service system 

 for the forward plant of the frigates DLG 14 and 

 DLG 15, which use return-flow atomizers in the 

 fuel oil burners. As may be seen in figure 9-22, 

 a system of this type requires fuel oil return 

 lines as well as fuel oil supply lines. Also, the 

 use of return-flow atomizers in these burners 

 requires a fuel oil cooler to cool the oil returned 

 from the burners. The cooler (which is not part 

 of the fuel oil service system on ships that do 

 not have return-flow atomizers) serves to keep 



the temperature of the returned fuel oil below 

 the flash point. 



In any type of fuel oil service system, the 

 suction arrangements for oil service pumps 

 allow rapid changes of pump suction from one 

 service tank (or one tank group manifold) to 

 another. The pump suction piping is arranged to 

 minimize contamination that might result from 

 one service pump taking suction from a service 

 tank that is contaminated with water. 



Three classes of fuel oil service pumps are 

 commonly used: main fuel oil service pumps, 

 port and cruising fuel oil service pumps, and 

 hand or emergency fuel oil service pumps. 



Main fuel oil service pumps are usually 

 screw-type rotary pumpslO that are driven by 

 steam turbines. However, other types of pumps 

 are used for this purpose on some ships. 



Port and cruising fuel oil service pumps on 

 recent ships are very similar to the main fuel 

 oil service pumps except that they are driven 

 by two-speed electric motors. The capacity of 

 these pumps can be adjusted by selecting the 

 required speed of the motor and also by using a 

 bypass arrangement to recirculate unused oil 

 from the pump discharge to the pump suction. 

 On older ships, the port and cruising fuel oil 

 service pumps may be rotary pumps or they may 

 be axial-piston variable-stroke pumps; in either 

 case, they are normally driven by electric mo- 

 tors rather than by steam turbines. 



Hand or emergency fuel oil s ervice pumps 

 are used on some ships when boilers must be 

 lighted off and neither steam nor electric power 

 is available. Most hand or emergency fuel oil 

 service pumps are herringbone gear pumps. On 

 recent ships, other means of lighting off without 

 steam or power are used, and the hand or emer- 

 gency fuel oil service pump is not required. 



The fuel oil service system contains a num- 

 ber of valves, all of which are important to the 

 safe and efficient operation of the boiler. The 

 major valves in the fuel oil service system 

 shown in figure 9-20 are listed here both to give 

 some idea of the complexity of the fuel oil ser- 

 vice system and to indicate the degree of preci- 

 sion required of operating personnel in lining 

 up, operating, securing, and controlling casual- 

 ties in the fuel oil service system. 



Fuel oil burners are discussed in chapter 10 of this 

 text. 



Basic types of pumps are discussed in chapter 15 of 

 this text. 



222 



