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8
COOLING SYSTEMS
 
A. GENERAL
 
8A1. Purpose of cooling systems. The high-speed high-output diesel engines of today are strictly limited as to the maximum temperature at which they can safely operate. To maintain the temperature below the maximum allowable limit, various types of cooling systems are used. The thermal efficiency of an engine would be greatly improved if it were not necessary to provide a cooling system. The cooling system losses, together with the loss of heat during the combustion, working, and exhaust periods, cut down the thermal efficiency of the engine to a relatively small percentage. Shown below are the percentages of useful work and various losses obtained from the combustion of a fuel oil in a diesel cylinder:

To useful work (brake thermal efficiency)30-35 percent
To exhaust gases30-35 percent
To cooling water and friction30-35 percent
Radiation, lube oil, and so forth0- 5 percent

There are three practical reasons for cooling an engine:

1. To maintain a lubricating oil film on pistons, cylinder walls, and other moving parts as explained in Chapter 7. This oil film must be maintained to insure adequate lubrication. The formation of an oil film depends in large degree on the viscosity of the oil. If the engine cooling system did not keep the engine temperature at a value that would insure the formation of an oil film, insufficient lubrication and consequent excessive engine wear would result. If the engine is kept too cool, condensation takes places in the lube oil and forms acids and sludge.

2. To avoid too great a variation in the dimensions of the engine parts. Great differences between operating temperatures at varying loads cause excessive changes in the dimensions of the moving parts. These excessive changes also occur when there are large differences between the cold and operating temperatures of the parts. These changes in dimensions

  result in a variation of clearances between the moving parts. Under normal operating conditions these clearances are very small and any variation in dimension of the moving parts may cause insufficient clearances and subsequent inadequate lubrication, increased friction, and possible seizure.

3. To retain the strength of the metals used. High temperatures change the strength and physical properties of the various ferrous metals used in an engine. For example, if a cylinder head is subjected to high temperatures without being cooled, the tensile strength of the metal is reduced, resulting in possible fracture. This high temperature also causes excessive expansion of the metal which may result in shearing of the cylinder bolts.

Cylinder heads, cylinder jackets, cylinder liners, exhaust headers, valves, and exhaust elbows usually are cooled by water. Pistons may be cooled either by water or oil. In present fleet type submarine installations, the pistons are cooled by lubricating oil which is in turn cooled by engine cooling water. It is important to keep all parts of the engine at as nearly the same temperature as possible. This can be accomplished to some extent by engine design. For instance, the water jacket should cover the entire length of the piston stroke to avoid possible unequal expansion of various sections of the cylinder and cylinder liner.

It requires time to conduct heat through any substance, therefore the thicker the metal, the slower the conduction. This is one of the reasons the size of cylinders in diesel engines is limited, because the larger the cylinder, the thicker the material necessary for liners and cylinder heads in order to withstand the pressures of combustion. Thicker metals cause the inside surfaces to run hotter, because the heat is not conducted so rapidly to the cooling water.

8A2. Operation of a cooling system. One of the principal factors affecting the proper

 
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cooling of an engine is the rate of flow of water through the system. The more rapid the rate of flow, the less danger there is of scale deposits, and the formation of hot spots, since the high water velocity has a scouring effect upon the metal surfaces of the jackets, and the heat is carried away more quickly. When the velocity of the circulating water is slower, the discharge temperature is higher and more heat per gallon of water circulated is carried away. When the circulation is speeded up, each gallon of water carries away less heat and the discharge temperature of the water drops, resulting in a relatively cool running engine.

The temperature of the engine can be controlled by the discharge temperature of the cooling water. This can be done in two ways, depending upon the arrangement of the piping and the type of pump used. A common and simple method is to control the amount of water pumped, by means of a throttling valve in the pump discharge to the engine cooling system. The water can then be made to pass more slowly through the engine and be discharged at a higher temperature, or to pass more rap idly at a lower temperature. If the pump is driven separately by an electric motor, the same effect can be obtained by slowing down or speeding up the pump. The other method to control the temperature is to bypass some of the warm discharged water around the cooler and directly to the suction side of the pump. This method gives a more uniform temperature throughout the cooling system and keeps the passage of water at a higher velocity.

In all modern engines, the latter method is used and accomplished automatically by means of a temperature regulator. These regulators may be set to give any desired temperature at the engine outlet. They are used not only to regulate the fresh water but also to regulate indirectly the temperature of the lubricating oil leaving the lubricating oil cooler. This is possible because the fresh water that is passed through the regulator and fresh water cooler is used as the cooling agent in the lubricating oil cooler. This permits the maximum amount of controllability of fresh water and lubricating oil temperatures with the use of the minimum amount of equipment.

  8A3. Types of cooling systems. Two types of cooling systems are in common use, the open system and the closed system. In the open system the engine is cooled directly by salt water. In the closed system the engine is cooled by fresh water and the fresh water is then cooled by salt water. The closed type of cooling system is in common use today in all modern medium- and high-speed diesel engines.

The open type of cooling system has many disadvantages, the most important being the exposure of the engine to scale formation, marine growth and dirt deposits in the piping, and fluctuating sea water temperature. Scale or deposits not only restrict water flow in the engine water passages but also act as a blanket and hinder heat transfer to the cooling water. This prevents adequate cooling of engine parts which may result in serious difficulties.

8A4. Open type cooling systems. The term open system is used because salt water is drawn directly from sea, passed through the system, and then discharged overboard.

In a typical system the salt water is drawn through sea valves and a strainer by a centrifugal pump and then discharged through the lubricating oil heat exchanger or cooler where it cools the lubricating oil. The water then passes to the cylinder liner jackets, exhaust manifold jackets, exhaust uptake jackets, the inboard exhaust valve, overboard sea valves, and to the outboard exhaust valve jackets and sprays. Part of the water may be piped to the fuel compensating water system. The remaining water passes through the muffler jackets and then overboard.

The open type of cooling system is used only on engines in the older types of submarines, particularly the O, R, and S classes. All of the later fleet type submarine engines are designed with cooling systems of the closed type.

8A5. Closed type cooling systems. Closed type, or fresh water cooling systems consist basically of two entirely separate systems-the fresh water cooling system and the salt water cooling system. In the fresh water cooling system the same fresh water is reused continuously for cooling the engine. The water is circulated throughout the engine cooling spaces

 
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by an attached circulating fresh water pump. The water is then led to a fresh water cooler, where it is cooled by the salt water of the salt water cooling system. After it leaves the cooler, the fresh water may or may not, depending on the installation, go through the lubricating oil cooler to act as cooling agent for the lubricating oil. The water then returns to the fresh water pump, completing the circuit.

Fresh water temperature is usually regulated by means of an automatic regulating valve which maintains the fresh water temperature at any desired value by bypassing the necessary amount of water around the fresh water cooler.

An expansion tank is provided which aids in keeping the fresh water system filled at all times by keeping available a ready supply of water. A vent usually is provided in the high point of the line to keep the system free of air, thereby preventing the water pump from becoming air bound. The expansion tank also is equipped with a gage glass by which the level of water in the tank may be constantly observed. If the level of water in the tank becomes too low, the system may be replenished from the ship's fresh water service system through a make-up line into the suction side of the attached fresh water pump. Any large rapid fluctuation in the level of water in the expansion tank signifies some type of leak into or out of the fresh water system. It usually indicates a cracked cylinder liner.

The salt water section of the closed type cooling system consists of an attached salt water pump, usually similar to the fresh water pump which draws salt water from sea through a sea chest, a stop and check valve, and a strainer, and discharges it through the fresh water cooler and then overboard. The overboard discharge performs varying functions, depending upon the individual installation. Normally it is used to cool the outboard exhaust valve, outboard exhaust piping, and muffler. The ship's compensating water and header box discharge lines also receive their water from

  the salt water circulating water overboard discharge.

On generator type engines the attached salt water pump furnishes salt water to the generator air coolers and returns the water to the overboard discharge. Throttling valves frequently are placed in lines to the fresh water cooler and generator air coolers to control the flow of water through these heat exchangers.

Thermometers and pressure indicators are placed in the system at various places. Salt water temperatures should not exceed 122 degrees F. Fresh water temperatures should be between 140 degrees F and 180 degrees F, with a minimum of 140 degrees F at the engine inlet. Outlet fresh water temperatures should be between 160 degrees F and 180 degrees F. Cooling water temperatures should not be allowed to drop below 140 degrees F, otherwise excessive engine wear and corrosion may result if the temperature drops, below the dewpoint.

8A6. Detached fresh water circulating pumps. Earlier General Motors and Fairbanks-Morse models (the GM 16-248 and the F-M 38D 8 and the 9-cylinder 38D 8 1/8) were equipped only with attached fresh water pumps. This design made it impossible for fresh water to be circulated in the engine for cooling purposes after the engine had been stopped. During normal operations in peacetime this is not too great a disadvantage because before stopping, the engine can be idled until it is properly cooled. During the war, however, emergency dives were a common occurrence and lack of a detached pump resulted in very high engine and engine room temperatures immediately after diving. This was not particularly good for the engine and imposed a hardship on engine room crews, especially in tropical climates. This condition resulted in the installation in all new submarines of detached fresh water pumps for circulation of the water after the engine has been stopped. An authorized alteration provides for the same installation in older fleet type submarines.

 
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Figure 8-1. Typical fresh and salt water cooling systems.
Figure 8-1. Typical fresh and salt water cooling systems.
 
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Figure 8-2. Salt water cooling system in superstructure.
Figure 8-2. Salt water cooling system in superstructure.
 
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8A7. Fresh water coolers. The engine water is cooled in a Harrison type heat exchanger or cooler, similar to the cooler used in the lubricating oil system. Although coolers used on various installations may differ in appearance and possibly to some extent in interior design, their operating principle is identical.

The cooler consists of a tube nest containing a number of oblong tubes fastened to a header plate at each end to form a core assembly. This assembly is attached to the cooler casing. The oblong tubes are baffled to form a winding passage for the liquid to be cooled. The liquid is cooled as it passes through the tubes, by the cold salt water (fresh water in lubricating oil coolers) which enters the casing, flows between the tubes and is discharged through the salt water outlet. The cooler is equipped with zinc plates in the sea water inlet and outlet passages and at the bottom of the cooler. These zincs centralize the electrolysis present in all submarine salt water systems. Their presence causes electrolytic action to eat away and disintegrate the zincs rather than the material of which the cooler tubes are made. This reduces to a minimum the number of cooler leaks to be expected in submarine installations. Zincs should be examined every 30 days or oftener where experience indicates the necessity. At each inspection they must be scraped clean. If this is not done, the efficiency of the zincs may become negligible and the electrolytic action will work on the tubes. When more than 50 percent of the zinc has been eaten away, the zinc should be renewed.

Coolers should be cleaned as frequently as found necessary to provide an unrestricted flow of water. In certain types of climate and service, deposits form more rapidly than in others. Heavy deposits cause an objectionable increase in pressure drop through the cooler and a consequent decrease in the cooling effect. Chemical cleanings at regular intervals in accordance with approved instructions will insure maximum operating efficiency at all times. Wires or prods which would damage the internal structure of the tubes must not be used in the cleaning operation. It is a universal rule that where the installation permits, the liquid to be

  cooled enters the cooler at a higher pressure than the cooling agent. Thus, in a fresh water cooler the pressure of fresh water should, if possible, be greater than the pressure of salt water, so that in case of leaks, the fresh water will leak into the salt water, a more desirable condition than leakage of the salt water into the fresh water system. This is also true in a lubricating oil cooler wherein the pressure of the lubricating oil is found to be greater than that of the fresh water. This prevents water from getting into the engine lubricating oil if cooler leaks develop.

8A8. Temperature regulator. The fresh water in the engine is maintained at a uniform temperature by the temperature regulator which controls the amount of fresh water flowing through the fresh water cooler and by bypassing the remainder of the water around the cooler.

When the fresh water temperature is higher than the temperature for which the regulator is adjusted, the regulator valve is actuated to increase the flow of fresh water through the fresh water cooler and decrease the flow through the bypass. When the engine water temperature is lower than the temperature for which the

Figure 8-3. Salt water corrosion of zincs.
Figure 8-3. Salt water corrosion of zincs.

 
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regulator is adjusted, the valve decreases the flow of fresh water through the fresh water cooler and increases the flow through the bypass.

The temperature regulator consists of a valve and a thermostatic control unit which is mounted on the valve. The thermostatic control, unit consists of two parts, the temperature control element and the control assembly.

  The temperature control element consists of a bellows connected by a flexible armored tube to a bulb mounted in the engine cooling water discharge line. The temperature control element is essentially two sealed chambers. One is formed by the bellows and cap which are sealed together at the bottom. The other chamber is in the bulb. The entire system (except for a small space at the top of the bulb) is
Figure 8-4. Fulton-Sylphon temperature regulator.
Figure 8-4. Fulton-Sylphon temperature regulator.
 
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filled with a mixture of ether and alcohol which vaporizes at a low temperature. When the bulb is heated, the liquid vaporizes and increases the pressure within the bulb. This forces the liquid out of the bulb and through the tube to move the bellows down and operate the valve.

The control assembly consists of a spring-loaded mechanical linkage which connects the temperature control element to the valve stem. The coil spring in the control assembly provides the force necessary to balance the force of the vapor pressure in the temperature control element.

Thus, the downward force of the temperature control element is balanced at any point by the upward force of the spring. This permits setting the valve to hold the temperature of. the engine cooling water within the allowed limits.

The regulator operates only within the temperature range marked on the name plate, and may be adjusted for any temperature within this range. The setting is controlled by the range

Figure 8-5. Thermostatic control unit.
Figure 8-5. Thermostatic control unit.

  adjusting wheel located under the spring seat. A pointer attached to the spring seat indicates the temperature setting on a scale attached to the regulator frame. The scale is graduated from 0 to 9, representing the total operating range of the regulator.

The temperature regulator can be controlled manually by turning the manual crankpin projecting from the side of the frame. This operates the regulating valve spring through a pair of beveled gears and a threaded sleeve. A pointer, attached to the threaded sleeve, indicates the valve position. When the pointer is in the BYPASS CLOSED position, the valve is set to allow all of the fresh water to be pumped directly through the water cooler. When the pointer is in the THERMOSTATIC position, it indicates that the unit is controlled completely by the automatic system as described. When the pointer is in the COOLER CLOSED position, it indicates that all of the fresh water is being bypassed around the water cooler. For automatic operation the pointer must be set at the THERMOSTATIC position.

Figure 8-6. Temperature control element.
Figure 8-6. Temperature control element.

 
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Figure 8-7 METHOD OF ADJUSTING AUTOMATIC TEMPERATURE REGULATORS.

Figure 8-8. Temperature regulator bulb.
Figure 8-8. Temperature regulator bulb.

8A9. Fresh water treatment. A treating compound may be added to fresh water in a closed cooling system for the prevention of scale formation and corrosion. This compound, when added, must be correctly measured in relation to the amount of water in the system. Too little will have no effect on the prevention of scale formation, whereas too much will increase the corrosion tendencies of the cooling water. The compound consists of a mixture of six parts (by weight) of trisodium phosphate and one part of cornstarch. The mixture must be completely

  dissolved in warm water, then added to the circulating pump suction.

To determine whether the water contains a sufficient amount of treating compound, a sample of water is drawn from the system. After cooling the sample to 85 degrees F or lower, about 10 milliliters of the cooled sample is transferred to a test tube and one drop of indicator solution, known as corrosion control indicator, is added. The addition of the one drop of indicator solution will change the color of the sample water. If the resulting color is yellow, insufficient treatment is indicated. If the color is red, satisfactory treatment is indicated, and if the resulting color is purple, it denotes that an excessive amount of treating compound has been added.

It should be noted that the addition of the treating compound is a preventive treatment only. It will not remove scale deposits already in the cooling system. If the system is clean and filled with fresh water only, a test of the water as outlined above should result in a yellow color. This indicates that the fresh water is suitable for use and that it will require the addition of at least one standard dose of treating compound, consisting of an ounce of treatment per 100 gallons of water, to bring it into the satisfactory (red) range of the test. If the color of the same test remains yellow after the addition of one standard dose, another dose should be added and this process repeated until a red color is obtained.

Should the test sample result in a purple color, about one-fourth of the cooling water should be drained from the system and replaced with fresh water. If on retest the purple color

Figure 8-9. Cutaway of thermal bulb.
Figure 8-9. Cutaway of thermal bulb.
 
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persists, additional water must be drained and replaced with fresh water. The color of the test sample must be red. It should never be permitted to enter the purple range.

Anti-freeze solutions. Approved anti-freeze solutions may be used to obviate the necessity of draining fresh water systems during freezing temperatures. The liquid usually used is ethylene

  glycol (Prestone). During freezing weather, all water jackets, cooling chambers, etc., not filled with anti-freeze solution must be thoroughly drained and blown out one at a time, using low-pressure air. Proper blowing out of the water can be accomplished only by closing off all cooling spaces and emptying them separately.
 
B. FAIRBANKS-MORSE COOLING SYSTEM
 
8B1. System piping. The F-M engine is cooled by circulating fresh water through its water passages. This water circulates in a closed system.

The external part of the system consists of the expansion tank, electrical resistance thermometer, high-temperature alarm contact maker, fixed orifice, temperature regulator, fresh water and lubricating oil coolers, and connecting piping with mercury bulb thermometers and

  pressure gages. After performing its engine cooling functions, the water leaves the engine and is piped to the fresh water cooler. There the fresh water is cooled by being passed through a large number of tubes around which cool sea water flows. After leaving this cooler, the fresh water is used as the coolant for the lubricating oil coolers. It is then piped back to the suction inlet, to repeat its passage through the engine.

A cooler bypass pipe connects the outlet

Figure 8-10. Fresh wafer system, F-M.
Figure 8-10. Fresh wafer system, F-M.
 
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line from the engine and the suction line to the pump. An orifice in this pipe permits passing a predetermined portion of the fresh water directly back to the pump, rather than through the coolers. This permits cooling of that portion of water going through the complete part of the system sufficiently so that it, in turn, can cool the lubricating oil adequately. From the oil cooler the water mixes with the uncooled fresh water, and enters the engine at the desired temperature.

A bypass pipe is installed across the fresh water cooler inlet and outlet. Flow of water through this cooler bypass is controlled by the automatic temperature regulator. By adjustment of this regulator, the temperature of the water can be controlled at the desired point in the engine under varying operating conditions. Also, when starting the engine, cold water is quickly brought up to good operating temperature range. If the fresh water temperature exceeds a certain set limit, a high-temperature alarm contact maker, mounted in the line between the engine outlet and the cooler, closes the alarm circuit to ring a warning gong.

  A small pipe leads from the engine water header to the expansion tank. Another small pipe leads from the pump suction line to the expansion tank. This arrangement enables the closed system to accommodate variations in water volume which result from the expansion and contraction of heating and cooling. Water is added to the system through the fresh water filling line from the ship's fresh water system. Excess water is discharged through the expansion tank vent. The bulb of a continuous reading electrical resistance thermometer is in the line from the engine to the cooler. The indicator for the thermometer is mounted on the engine gage board. Between the fresh water pump and the engine inlet a small tube leads to the fresh water pressure gage on the engine gage board. A mercury bulb thermometer is installed near the inlet to the lubricating oil cooler, and another on the line from the coolers to the fresh water pump.

The other pump mounted opposite the fresh water pump on the engine circulates the salt water. This pump draws salt water from the ship's sea chest and forces it through the

Figure 8-11. Salt water system, F-M.
Figure 8-11. Salt water system, F-M.
 
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Figure 8-12. Fresh water passage through F-M cylinder.
Figure 8-12. Fresh water passage through F-M cylinder.
fresh water cooler and the generator air cooler. Leaving the coolers, the salt water flows through the exhaust piping jackets and overboard. A mercury bulb thermometer indicates the temperature of the salt water, flowing from the fresh water cooler. From the pump discharge pipe, a small tube leads to the salt water pressure gage on the engine gage board.

8B2. F-M engine cooling passages. Entering the engine through an inlet in each exhaust nozzle, the fresh water moves through passages which surround the exhaust nozzles, and on into the exhaust manifold water passages extending the full length of the engine. The exhaust passages from the cylinder liners and the lower part of the liner are also cooled by the fresh water circulation around the exhaust belts. The water enters from the exhaust manifolds at openings at the lower side of the belts and returns to the manifolds at openings at the top. The water then rises from the exhaust manifolds to pass through an inlet elbow on either

  side of each cylinder. These elbows carry the water to the spaces between the cylinder liner and its jacket. Cast-in ribs on the cylinder liner direct the water upward, to cool the liner thoroughly from the bottom. Water passages also lead to the water jackets on the injection nozzle, cylinder relief valve, and air start check valve adapters, to cool these units. Upon reaching the top of the cylinder liner jacket, the water passes out of the cylinder water space through an outlet pipe which leads to the water header. This header, rectangular in cross section, extends along the opposite side of the cylinder block from the control quadrant, just below the air receiver. Its outlet flange is at the control end of the engine where it joins the external part of the system piping.

8B3. Fairbanks-Morse water pumps. The fresh water and salt water circulating pumps in the F-M installations are identical centrifugal pumps. The pumps, mounted on opposite sides at the control end of the engine, are driven by

 
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the lower crankshaft through the flexible drive which also drives the fuel and lubricating oil pump and the governor.

The internal construction of the pump at the impeller end is similar to that of the GM pump. The pump shaft, however, is supported on two bearings, a guide bearing near the impeller

  end and a thrust bearing at the drive end. Lubricating oil reaches the bearings from the control end compartment of the engine through openings in the pump frame. The oil is distributed by the bearing spacer on the pump shaft. Leakage of oil to the outside of the engine is prevented by an oil seal ring and retainer.
Figure 8-13. Cross section of F-M circulating water pump.
Figure 8-13. Cross section of F-M circulating water pump.
 
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C. GENERAL MOTORS COOLING SYSTEM
 
8C1. System piping. With the exception of minor differences in the piping arrangement, the cooling system for GM engines is similar to that used in F-M engines. The external part of the closed system is composed of the expansion tank located at the highest point in the system, the fresh water and lubricating oil coolers, the automatic temperature regulator, electrical resistance and mercury bulb thermometers, a pressure gage at the fresh water pump discharge, and the necessary piping. After circulating through the engine, the fresh water passes through a temperature regulator before reaching the fresh water cooler. Water passing through the fresh water cooler is cooled by salt water. Part of the water is bypassed around the cooler and part of it flows through it, depending on the setting of the temperature regulator. The water then goes through the lubricating oil cooler where it acts as the cooling agent. From the lubricating oil cooler, the fresh water returns to the suction side of the fresh water pump for recirculation through the engine. Variations in water volume resulting from expansion and contraction caused by heating and cooling are controlled by two pipe lines, one extending from the expansion tank to the suction side of the pump, the other extending from the expansion tank to the engine fresh water manifold. A vent line at the expansion tank keeps the system free of air, thereby preventing the fresh water pump from becoming air bound, a condition that would result in excessive water temperature.

The salt water pump draws salt water from the sea chest through a strainer and forces it through the fresh water cooler and out through the overboard discharge. A branch line leaving the main line ahead of the fresh water cooler supplies salt water to the generator air cooler. The discharge from the generator cooler joins the outlet pipe extending from the fresh water cooler for overboard discharge. The pressure of the salt water before entering the fresh water cooler is indicated by a pressure gage and is controlled by a throttling valve located between the salt water pump discharge and the fresh water cooler. A similar valve is used to control the flow of water to the generator cooler.

  The salt water overboard discharge is split into several parts. Some of the water goes to the outboard exhaust lines where it circulates through the exhaust line jacket. This water then goes through the outboard exhaust valve for cooling purposes and into the exhaust muffler. Part of this water is sprayed into the muffler to act as a spark arrester, and the rest is piped over the side.

Another line from the salt water system connects into the fuel compensating water line and to the header box. Most of the water going into this line is discharged over the side through the header box, but any water needed to keep the fuel oil and compensating water systems filled flows by gravity to the desired tank through the fuel compensating water line.

8C2. General Motors engine cooling passages. The attached fresh water pump forces fresh water to a manifold located in the scavenging air chamber in each cylinder bank. From the manifolds, the water passes into the cooling spaces of the cylinder liners by way of a water

Figure 8-14. Cross section of GM cylinder liner
showing cooling passages.
Figure 8-14. Cross section of GM cylinder liner showing cooling passages.

 
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Figure 8-15. FRESH WATER SYSTEM, GM 16-278A.

Figure 8-16. SALT WATER SYSTEM, GM 16-278A.

Figure 8-17. Cross section of circulating wafer pump, GM.
Figure 8-17. Cross section of circulating wafer pump, GM.
connection at the lower deckplate in the engine cylinder block. The water is then forced upward into the cylinder heads through ferrules in the top of the liner, into the water jacket around the exhaust elbows, and finally into the water jacket surrounding the exhaust manifold. From the exhaust manifold, the water enters the external piping leading to the temperature regulator.

8C3. General Motors water pumps. The salt water and fresh water pumps used in GM. cooling systems are of the centrifugal type. The pumps are mounted on opposite sides of the blower housing of the engine and are driven by the crankshaft through the accessory drive gear train. The principal differences between the two pumps are in size and capacity. The salt water pump has a capacity of 560 gallons per minute, the fresh water pump, 350 gallons per minute. The following description applies to both pumps.

The principal parts of the pump are the housing, impeller, drive shaft, and pump supporting head. The impeller is keyed to the tapered end of the driving shaft and consists of a number of vanes which throw the water entering at the center of the impeller, outward

  through the pump outlet. The impeller rotates in the housing on two pairs of replaceable wear rings. A valve sleeve that prevents shaft wear is keyed to the pump shaft and butts against the impeller. A small packing ring fitted in a recess in the end of the valve sleeve provides a watertight seal. The packing is compressed between the sleeve and the shaft by a locking sleeve held in place by a setscrew. When tightening the packing it is first necessary to remove the packing gland which provides access to the setscrew. After loosening the setscrew, the locking sleeve can be rotated with a spanner wrench.

The stuffing box packing that surrounds the shaft sleeve is made up of five rings composed of a plastic binder impregnated with lead and graphite. Each ring is about 5 1/16 inch thick.

The pump drive shaft rotates in a ball bearing that is pressed on the shaft and is supported in a bearing housing inside the supporting head of the pump. The bearing is splash lubricated from the accessory drive gear train. A felt seal prevents oil from leaking out of the housing. Water that may work its way along the shaft is prevented from reaching the bearing by a finger locked to the shaft with a setscrew.

 
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