the THERMOSTATIC POSITION. Turn theadjusting wheel until the pointer is opposite 2 onthe scale plate. Loosen the locknut and unscrewthe valve stem until it is free of the thermostaticstem. Then turn the adjusting wheel until thepointer is opposite 8 on the scale plate. (Note: Thepreceding steps should be performed with the ther-mostatic bulb removed from the ship’s piping andwhen the bulb temperature is below 100°F.)Again rotate the manual crankpin until thelower end of the seating sleeve is flush with thelower end of the thermostatic stem. With theseating sleeve and the indicator pointer in thisposition, loosen the screws in the indicator plateand slide the plate up or down as needed to alignthe THERMOSTATIC mark in the center of theplate with the indicator pointer. Then retightenthe screws. (The marks COOLER CLOSED andCOOLER BY-PASS on the indicator plate areonly approximate.) Screw the valve stem into thethermostatic stem and turn it until the cooler pop-pet valve seats firmly. Turn the adjusting wheeluntil the pointer is opposite 2 on the scale plate.Turn the valve stem one full turn into the ther-mostatic stem and retighten the locknut.With the manual control on the THER-MOSTATIC position, turn the adjusting wheelin a direction to bring the pointer to number 9on the scale plate. Run the engine at warmupspeed until the temperature of the fluid, asindicated by the thermometer in the line with thethermostatic bulb, rises to the desiredtemperature. (The desired temperature must bedetermined in advance from applicableinstructions.)With the engine running at warmup speed andthe temperature at the thermostatic bulb at thedesired value, turn the adjusting wheel until thecooler poppet just begins to leave its seat. Thisaction is shown by the movement of the mark onthe valve stem downward from the COOLERCLOSED mark on the valve position indicator.Valves adjusted in accordance with this procedurewill normally maintain the temperature of thefluid at the thermostatic bulb between the desiredvalue and a temperature approximately 20°higher, under any conditions of engine load orinjection temperature. This 20° difference is thetemperature rise required to cause the poppetvalve to move through the necessary travel.HEATING EXCHANGERDEFINITIONSProblems with the cooling system of an enginemay prevent the cooling system from keeping theengine parts and working fluids at safe operatingtemperatures. Failure of the system may lead toseveral of the troubles and casualties that havebeen discussed earlier.In marine installations, lubricating oil andmost of the engine parts are cooled by the circula-tion of seawater, freshwater, or both. When thecooling of an engine part is mostly by oil sprayor oil circulation, the oil is cooled by circulationthrough an oil cooler. Figure 3-11 illustrates acooling system in which both freshwater andseawater serve as coolants.When maintaining engine cooling watertemperatures within specified limits, the principaldifficulties you may encounter are in maintain-ing circulating pumps in operating condition;preventing corrosion; reducing the cause of scaleformation in water jackets and heat exchangers;cleaning jackets and heat exchangers accordingto proper procedures; and in preventing leaks inthe various parts of the system.The coolers (or heat exchangers) which removethe heat from the cooling water of an engine mayvary considerably in design. Those used in cool-ing systems may be classified basically as theradiator type and the tubular type. The radiatoris sometimes referred to as the strut or the Har-rison type, while the tubular is identified as theRoss or shell-and-tube type. A heat exchanger ofboth types is shown in figure 3-12. The heat ex-changer on the top of the picture is a radiator typeheat exchanger; the one on the bottom is atubular-type heat exchanger. In heat exchangersof the radiator type, the freshwater passes throughthe tubes and the seawater passes around them.In the tubular type, the freshwater surrounds thetubes and the seawater passes through them.CASUALTIESAlthough heat exchangers vary in design, theyare all subject to similar casualties. The principaldifficulties which may prevent heat exchangersfrom functioning properly are excessive scaledeposits on the cooler element, clogged coolerelements, or cooler leakage.Chapter 3—ENGINE MAINTENANCE3-11
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