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1
DISTILLATION OF SEA WATER
 
A. FRESH WATER
 
1A1. Importance of fresh water. Fresh water has always been a major item aboard ship; in fact, until comparatively recent times it has been the factor that controlled the length of time a ship could remain at sea. In the era of sailing ships, it was necessary to spread canvas whenever it rained, and to catch the rain water in canvas water monkey bags in order to replenish the supply of fresh water on board. This water was used only for cooking and drinking purposes, there being no need then for fresh water in the operation of steam-driven propulsion machinery.

On modern naval vessels fresh water is of even more importance, for it is used not only for cooking, drinking and bathing, but also in boilers, storage batteries, and as a cooling agent for modern Diesel engines. All large naval vessels have distilling plants operated by steam, either high or low pressure, which vary in capacity and type with the size and class of ship.

1A2. Submarine sea water distillers. The first successful apparatus for distilling sea water on submarines was the Nelseco-Clarkson exhaust evaporator installed about 1916. This evaporator operated by using the exhaust from the main engines to heat the water to the boiling point, and as the salt water boiled, the vapor was led to a condenser where it condensed to fresh water. Since the operating conditions of the engine varied, the heat value of exhaust gas available varied accordingly, and hence it was almost impossible to maintain a heat balance. The quantity and quality of the fresh water varied with the operating conditions. The disadvantage of this evaporator for submarine use was that it could be operated only at full capacity when the submarine was running on the surface at high speeds. It could not be used during periods of submergence.

During the period from 1937 to 1940 a vapor compression type of distilling unit was developed for use aboard submarines. Experiments on this unit were conducted under actual operating conditions

  on board the submarine U.S.S. S-20 at New London, Connecticut, and resulted in the development of the electrically operated Model S vapor compression distilling unit which produces 750 gallons per day (gpd). These units were installed on all new submarines and were used to replace the Nelseco-Clarkson type on older submarines.

Further experiments with distilling units were conducted by the manufacturer in coordination with the Bureau of Ships and in 1943, the Model X (1,000 and 2,000 gpd) vapor compression distilling unit was developed. The Model X-1 (1,000 gpd) distilling units were, for a number of years, the only units to be installed on new submarines.

During the interval from that time until the present (Jan. 1955), a number of improvements and alterations have been made to the original Model X-1 installations. The two-lobed compressors have been replaced with General Motors three-lobed compressors. (Section 7B) The original heat exchangers, in which there were three small tubes inside of each larger tube, have been replaced with the improved type described in this text. The designation of the improved distilling units was changed from Model X-1 to Model AAA-1.

In this text, frequent reference is made to the Model X-1 distilling unit. It is to be understood, unless specifically stated otherwise, that each reference applies also to the Model AAA-1 unit.

Further alterations have been made to adapt the units to snorkeling conditions. It may be expected that the designation of these converted units may be changed again.

There are also several newer models of distilling plants undergoing service tests on some of the later types of submarines. These new models will be described briefly in Chapter 10.

1A3. Submarine distilling equipment. The distilling plants in use on submarines consist of: the

 
(1)

Kleinschmidt, Model S; the Badger Models X-1, Y-1, V 1, WS-1, the Cleaver-Brooks 300 gpd, and the Griscom-Russell 4,000 gpd Soloshell installed on Nautilus. There are two (2) units of each applicable type installed on all of the later class vessels except the SST's, the SSK's, and the SSN's which have only one (1) unit. The Models are described and illustrated separately.

1A4. Consumption of fresh water. A modern submarine consumes during a war patrol an average of approximately 500 gallons per day of fresh water for cooking, drinking, washing and engine makeup water. In addition to this consumption the main storage batteries require about 500 gallons of battery water per week; giving a total requirement of at least 4,000 gallons per week. These minimum requirements will leave enough water for each man in the crew to have a bath at least twice a week.

  1A5. Fresh water stowage capacity. The normal fresh water stowage capacity on most submarines is about 5,600 gallons; of this, 1,200 gallons are battery water and are stored in the battery water tanks. This water will last only about ten days, and it is good practice not to allow the fresh water supply on hand to drop below one-half the normal capacity.

The operation of the submarine itself determines when the distilling plant should be used. On some vessels, the auxiliary tanks are filled with fresh water prior to leaving the tender or base. This water is used for showers and washing of clothes and supplements the normal capacity.

Small fresh water tanks are located in the forward and after compartments and contain emergency fresh water, but this supply is held in reserve and is not normally used.

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