PRINCIPLES OF NAVAL ENGINEERING 



is followed by a letter. If two boilers serve the 

 No. 3 propulsion unit and the No. 3 shaft, for 

 example, the boilers would be identified as No. 

 3A and No. 3B. Where letters are used, they 

 are used in sequence going from starboard to 

 port and then from forward to aft. 



On older ships, the practice of identifying 

 propulsion units by the number of the shaft 

 they serve is slightly different. In general, each 

 propulsion unit is numbered to correspond 

 with the number of the shaft it serves; but 

 the numbering of the boilers is generally not 

 the same as the numbering of the propulsion 

 units and the shafts. On an older ship, for ex- 

 ample, the No. 1 boiler and the No. 2 boiler 

 might serve the No. 1 propulsion unit and the 

 No. 1 shaft, while the No. 3 boiler and the No. 4 

 boiler would serve the No. 2 propulsion unit and 

 the No. 2 shaft. 



The functional relationships of the major 

 propulsion units and of many auxiliaries are 

 shown in figure 9-1. This illustration does not 

 indicate the actual location of the machinery 

 units; indeed, the physical location is often 

 surprisingly different from the location that 

 might be assumed from a diagram of this type. 

 In considering the physical arrangement of 

 machinery, however, we must keep the functional 

 relationships clearly in mind. The three major 

 piping systems shown in figure 9-1 are the 

 main steam system, the auxiliary steam system, 

 and the auxiliary exhaust system; again, a 

 functional rather than a physical relationship 

 is indicated. The three systems are discussed 

 in more detail later in this chapter; at this point 

 it is only necessary to note the relationships 

 of these vital systems to the propulsion units 

 and auxiliaries. 



The propulsion machinery spaces may be 

 physically arranged in several ways. Some ships 

 have firerooms, containing boilers and the sta- 

 tions for operating them, and enginerooms, 

 containing propulsion turbines and the stations 

 for operating them. On some ships, one fire- 

 room serves one engineroom; on others, two 

 firerooms serve one engineroom. Instead of 

 firerooms and enginerooms, many large ships 

 of recent design have spaces which are called 

 machinery rooms. Each machinery room con- 

 tains both the boilers and the propulsion turbines 

 that serve a particular shaft. On some recent 

 ships that have certain automatic controls, the 

 propulsion machinery is very largely operated 

 from separate enclosed operating stations lo- 

 cated within the machinery room. 



No matter what arrangement of machinery 

 spaces is used, the propulsion machinery is 

 usually on two levels. The condensers and the 

 main reduction gears are on the lower level. 

 The propulsion turbines and the high speed 

 pinion gears to which they are connected are 

 on the upper level with the low pressure tur- 

 bine exhaust directly over the condenser. The 

 boilers occupy both the lower level and the up- 

 per level; the stations for firing the boilers 

 (sometimes referred to as "the firing aisle") 

 are on the lower level, while the stations for 

 operating the valves that admit feed water to 

 the boilers are on the upper level. The boil- 

 ers are usually located on the centerline of the 

 ship or else they are distributed symmetrical- 

 ly about the centerline. The long axis of the 

 boiler drums runs fore and aft rather than ath- 

 wartship. Other machinery, including the pro- 

 pulsion auxiliaries, is arranged in various ways 

 as space and weight considerations permit. 



Figure 9-2 shows the general arrangement 

 of propulsion machinery on destroyers of the 

 DD 445 and DD 692 classes. The machinery is 

 arranged so that the forward fireroom and the 

 forward engineroom can be operated together as 

 one completely independent plant, while the 

 after fireroom and the after engineroom can 

 be operated together as another completely 

 independent plant. All propulsion machinery, 

 including auxiliaries, is duplicated in each 

 plant. The arrangement shown in figure 9-2 is 

 typical of most destroyers, even the newer 

 ones; however, the newer destroyers contain 

 a non-machinery separation space between the 

 forward and after machinery plants. 



Figures 9-3, 9-4, 9-5, and 9-6 show the 

 arrangement of machinery in the No. 1 fire- 

 room and the No. 1 engineroom of the frigates 

 DLG 14 and DLG 15. The arrangement shown 

 in these illustrations is also typical of that in 

 the frigates DLG 6-13. The forward (No. 1) 

 fireroom and engineroom may be operated to- 

 gether as a separate plant, as may the after 

 (No. 2) fireroom and engineroom. 



Figure 9-7 shows the general arrangement 

 of propulsion machinery on the CA 68 class of 

 heavy cruisers. This arrangement is typical 

 of cruisers commissioned during World War 

 II. The two forward firerooms and the forward 

 engineroom constitute one plant; the two after 

 firerooms and the after engineroom constitute 

 the other plant. Cross-connections make it 

 possible for other operational arrangements 

 to be used. 



194 



