PRINCIPLES OF NAVAL ENGINEERING 



cross-connected mains. The two mains are 

 installed in the same horizontal plane but are 

 separated athwartships as far as practicable. 

 In general, the two mains are installed on the 

 damage control deck. The vertical loop firemain 

 system consists of two single fore-and-aft 

 cross-connected mains. The two mains are 

 separated both athwartship and vertically. As 

 a rule, the lower main is located below the 

 lowest complete watertight deck and the upper 

 main is located below the highest complete 

 watertight deck. 



FLUSHING SYSTEMS 



The shipboard flushing system is supplied 

 with sea water by a branch from the firemain. 

 On very small ships, a separate sanitary and 

 flushing pump is provided which takes suction 

 from the sea. When the flushing system is 

 supplied from the firemain, the branch is taken 

 as near the top of the main as possible so that 

 sediment from the firemain will not enter the 

 flushing system. Since the firemain pressure is 

 too high for a flushing system, the water is 

 led through a strainer to a reducing valve which 

 reduces the pressure to 35 psi. Air chambers 

 are installed in the flushing system where it 

 runs to urinals and water closets; the air 

 chambers absorb water hammer caused by the 

 quick closing of the flush valves and spring- 

 closing faucets. 



DRAINAGE SYSTEMS 



The drainage system aboard ship is divided 

 into two parts: (1) the main and secondary sys- 

 tems, and (2) the plumbing and deck drains. 

 Between them, these systems collect and dispose 

 overboard all the shipboard waste fluids. 



The main drainage system consists of piping 

 installed low in the ship, with suction branches 

 to spaces to be drained and direct connections 

 to eductors or drainage pumps. This system 

 generally serves the main machinery spaces 

 and a few other spaces. 



The secondary drainage system supplements 

 the main drainage system wherever the main 

 drainage system cannot be extended because of 

 interference of spaces through which the passage 

 of piping is prohibited or because the length of 

 piping would be too great for efficient drainage. 

 Each secondary drainage system is independent 

 of the main drainage system and has its own 

 pumps or eductors and its own sea connections. 



Plumbing and deck drains are divided into 

 two groups— soil drains and waste drains. Soil 

 drains convey fluids from urinals and water 

 closets. Waste drains convey fluids from all 

 other plumbing fixtures and deck drains. 



SPRINKLING SYSTEMS 



Sprinkling systems are installed aboard ship 

 in magazines, turret handling rooms, hangar 

 decks, missile spaces, and other spaces where 

 flammable materials are stowed. Water for 

 these systems is supplied from the firemain 

 through branch lines. 



Most sprinkling systems aboard ship are 

 of the dry type— that is, they are not charged 

 with water beyond the sprinkling control valves 

 except when they are in use. Sprinkling systems 

 in magazines which contain missiles are of the 

 wet type. The sprinkling control valves in 

 magazine sprinkling systems are operated auto- 

 matically by heat-actuated devices. Other 

 sprinkling control valves are operated manually 

 or hydraulically, either locally or from remote 

 stations. In those areas of the ship in which 

 major flammable liquid fires could occur, 

 such as in aircraft hangars, foam sprinkling 

 systems are provided. 



WASHDOWN SYSTEMS 



Washdown systems are installed aboard ship 

 for the purpose of removing radioactive con- 

 tamination from the topside surfaces of a ship. 

 Essentially, a washdown system is a dry-pipe 

 sprinkler system, with nozzles especially de- 

 signed to throw a large spray pattern on all 

 weather decks. For ships under construction 

 or conversion, a permanent washdown system 

 is installed; for ships already in service, 

 interim washdown system kits are provided 

 for installation by ship's force. In either case, 

 water for the washdown system is supplied 

 from the firemain. 



POTABLE WATER SYSTEMS 



Potable water systems are designed to pro- 

 vide a constant supply of potable water for all 

 ship's service requirements. Potable water is 

 stored in various tanks throughout the ship. 

 The system is pressurized either by a pump 

 and pressure tank or by a continuously opera- 

 ting circulating pump. The potable water system 

 supplies scuttlebutts, sinks, showers, scullery, 



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