PRINCIPLES OF NAVAL ENGINEERING 



at normal speeds. The motor-driven pump 

 serves as standby for the other two lube oil 

 service pumps. 



Figure 9-23 illustrates the lube oil supply 

 and lube oil drain piping of the service system 

 on the frigates DLG 14 and DLG 15. 



COMPRESSED AIR SYSTEMS 



Completely independent compressed air sys- 

 tems with individual compressors include the 

 high pressure air system, the ship's service 

 air system, the aircraft starting and cooling 

 air system, the combustion control air system, 

 the air deballasting system, and the oxygen- 

 nitrogen producer air system. For other ser- 

 vices, air is taken from the high pressure 

 system or from the ship's service air system, 

 as required. Air is provided by high pressure, 

 medium pressure, or low pressure air com- 

 pressors, as appropriate. 



The high pressure air system is designed 

 to provide air above 600 psi and up to 5000 psi 

 for charging air banks and, at required pres- 

 sures, for services such as missiles, diesel 

 engine starting and control, torpedo charging, 

 and torpedo workshops. When air is required 

 for these services at less than the system pres- 

 sure, the outlet from the high pressure air 

 system is equipped with a reducing valve. 



Air for diesel engine starting and control 

 is provided on some ships by a medium range 

 compressure at a pressure of 600 psi or from 

 the high pressure system, through appropriate 

 reducing valves. 



The ship's service compressedair system is 

 a low pressure system that is installed on 

 practically all surface ships. This system pro- 

 vides compressed air at the required pressure 

 for the operation of pneumatic tools, the opera- 

 tion of oil-burning forges and furnaces, the 

 charging of pump air chambers, the cleaning 

 of equipment, and a variety of other uses. The 

 ship's service air system is normally designed 

 for a working pressure of 100 psi; on ships 

 such as tenders and repair ships, however, 

 where there is a greater demand for air, the 

 system is designed for a higher working pres- 

 sure (usually about 125 psi). The ship's service 

 air system is normally supplied from a low 

 pressure air compressor; on some ships, how- 

 ever, the system may be supplied from a higher 

 pressure system, through reducing valves. 



An aircraft starting and cooling air system 

 is installed on aircraft carriers. This system 



is designed to provide air at various tempera- 

 tures (50° to 500° F) and pressures (48 psia to 

 62 psia) by gas turbine. The system supplies 

 compressed air to meet the conditions of starting 

 and cooling aircraft being served. 



Combustion control air systems (more pro- 

 perly called boiler control air systems) are 

 installed on some ships to provide supply air 

 for the pneumatic units in automatic boiler 

 control systems. A boiler control air system 

 usually consists of an air compressor, an air 

 receiver, and the piping required to supply 

 air to all units of the boiler control system 

 On some older ships, compressed air for the 

 operation of the boiler controls is taken from 

 the ship's service air system, through reducing 

 valves. 



An air deballasting system is provided on 

 some ships for deballasting by air. This system 

 is designed to provide large quantities of air 

 (7500 cubic feet per minute) at low pressure 

 (200 psi). All compressors discharge to a com- 

 mon air loop distribution which feeds all ballast 

 tanks. 



Oxygen-nitrogen producer air systems are 

 installed on aircraft carriers and submarine 

 tenders. The air is supplied by high pressure 

 air compressors, via oil filters and moisture 

 separators, directly to the oxygen- nitrogen 

 producer. 



FIREMAIN SYSTEMS 



The firemain system receives water pumped 

 from the sea and distributes it to fireplugs, 

 sprinkling systems, flushing systems, auxiliary 

 machinery cooling water systems, washdown 

 systems, and other systems as required. 



There are three basic types of firemain 

 systems used on naval ships: the single main 

 system, the horizontal loop system, and the 

 vertical loop system. The type of firemain 

 system installed in any particular ship depends 

 upon the characteristics and functions of the 

 ship. Small ships generally have single main 

 firemain systems; large ships usually have 

 one of the loop systems or a composite system 

 which is some combination or variation of the 

 three basic types. 



The single main firemain system consists 

 of one main which extends fore and aft. The 

 main is generally installed near the centerline 

 of the ship, extending as far forward and as far 

 aft as necessary. The horizontal loop firemain 

 system consists of two single fore-and-aft 



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