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7
LUBRICANTS AND LUBRICATION SYSTEMS
 
A. GENERAL
 
7A1. Purpose of a lubricant in a diesel engine. Lubricating oil in a diesel engine is used for the following purposes:

1. To prevent metal-to-metal contact between moving parts.

2. To aid in engine cooling.

3. To form a seal between the piston rings and the cylinder wall.

4. To aid in keeping the inside of cylinder walls free of sludge and lacquer.

A direct metal-to-metal moving contact has an action that is comparable to a filing action. This filing action is due to minute irregularities in the surfaces, and its harshness depends upon the finish and the force of the contacting surfaces as well as on the relative hardness of the materials used. Lubricating oil is used to fill these minute irregularities and to form a film seal between the sliding surfaces, thereby preventing high friction losses, rapid engine wear, and many operating difficulties. Lack of this oil film seal results in seized, or frozen pistons, wiped bearings, and stuck piston rings. The high-pressures of air and fuel in diesel engines can cause blow-by of exhaust gases between the piston rings and cylinder liner unless lubricating oil forms a seal between these parts.

Lubricating oil is used to assist in cooling by transferring or carrying away heat from localized hot spots in the engine. Heat is carried away from bearings, tops of the pistons, and other engine parts by the lubricating oil. It is the volume of lubricating oil being circulated that makes cooling of an engine possible. For example, under average conditions, an 8-inch by 10-inch cylinder requires about 24 drops of oil per minute for lubrication of the cylinder wall. About 30 drops of oil per minute normally will lubricate a large bearing when the engine is running at high speed. Yet some engines

  circulate as much as 40 gallons of lubricating oil per minute. This illustrates how much of the lubricating oil is used for cooling purposes.

Lubricating oil that is used to form a seal between piston rings and cylinder walls or on any other rubbing or sliding surface must meet the following requirements:

1. The oil film must be of a sufficient thickness and strength, and must be maintained under all conditions of operation.

2. The oil temperature attained during operation must be limited.

3. Under normal changing temperature conditions the oil must remain stable.

4. The oil must not have a corrosive action on metallic surfaces.

It is important not only that the proper type of oil be selected but that it be supplied in the proper quantities and at the proper temperature. Moreover, as impurities enter the system, they must be removed. Diesel engines used in the present fleet type submarines use a centralize pressure feed lubrication system. In this system is incorporated an oil cooler or heat exchanger in which the hot oil from the engine transfers its heat to circulating fresh water. The fresh water is then cooled by circulating sea water inside the fresh water cooler. The heated sea water is then piped overboard.

In order to maintain a strong oil film or body under varying temperature conditions, a lubricating oil must have stability. Stability of the oil should be such that a proper oil film is maintained throughout the entire operating temperature range of the engine. Such a film will insure sufficient oiliness or film strength between the piston and cylinder walls so that partly burned fuel and exhaust gases cannot get by the piston rings to form sludge.

7A2. Chemistry of lubricating oils. As explained in Chapter 5, lubricating oil is the product of the fractional distillation of crude

 
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petroleum. Lubricating oils obtained from certain types of crude petroleum are better adapted for diesel engine use than others, therefore it was formerly highly important that the oils be manufactured from crudes that contained the smallest possible percentage of undesirable constituents. Modern refining methods, by employing such processes as fractionation, filtration, solvent refining, acid treating, and hydrogenation have, however, made it possible to produce acceptable lubricating oils from almost any type of crude oil.

7A3. Properties of lubricating oils. To insure satisfactory performance a lubricating oil must have certain physical properties which are determined by various types of tests. These tests give some indication of how the oil may perform in practice, although an actual service test is the only criterion of the quality of the oil. Some of the tests by which an oil is checked to conform to Navy specifications are as follows:

1. Viscosity. The viscosity of an oil is the measure of the internal friction of the fluid. Viscosity is generally considered to be the most important property of a lubricating oil since friction, wear, and oil consumption are more or less dependent on this characteristic.

2. Pour point. The lowest temperature at which an oil will barely pour from a container is the pour point. High pour point lubricating oils usually cause difficulty in starting in cold weather due to the inability of the lubricating oil pump to pump oil through the lubricating system.

3. Carbon residue. The amount of carbon left after the volatile matter in a lubricating oil has been evaporated is known as the carbon residue of an oil. The carbon residue test gives an indication of the amount of carbon that may be deposited in an engine. Excessive carbon in an engine leads to operating difficulties.

4. Flash point. The lowest temperature at which the vapors of a heated oil will flash is the flash point of the oil. The flash point of an oil is the fire hazard measure used in determining storage dangers. Practically all lubricating oils have flash points that are high enough to eliminate the fire hazard during storage in submarine, tender, or base stowage facilities.

  5. Corrosion. The tendency of an oil to corrode the engine parts is known as the corrosive quality of the lubricating oil. The appearance of a strip of sheet copper immersed in oil at 212 degrees F for 3 hours formerly was thought to indicate the corrosive tendency of an oil. This test, however, is not necessarily a criterion of the corrosive tendency of the newer compounded oils, some of which do darken the copper strip but are not corrosive in service. Corrosive oil has a tendency to eat away the soft bearing metals, resulting in serious damage to the bearing.

6. Water and sediment. Water and sediment in a lubricating oil normally are the result of improper handling and stowage. Lubricating oil should be free of water and sediment after leaving the purifier and on arriving at the engine.

7. Acidity or neutralization number. The neutralization number test indicates the amount of potassium hydroxide, in milligrams, necessary to neutralize one gram of the oil tested. It is, therefore, proportional to the total organic and mineral acid present. The results are apt to be misleading or subject to incorrect interpretation, since the test does not distinguish between corrosive and noncorrosive acids, both of which be present. The chief harm resulting from the presence of organic acid, which is noncorrosive, is its tendency to emulsify with water. This emulsion picks up contaminants and is a sludge which may interfere with proper oil circulation. The neutralization number of new oils is generally so low as to be of no importance.

8. Emulsion. The ability of an oil to separate from water in service is known as the emulsibility of the lubricating oil. The emulsibility of a new oil has little significance. Two oils that have different emulsifying tendencies when new, may have the same emulsion tendency after being used in an internal combustion engine for a few hours. The emulsibility of an oil that has been in use for some time is important.

9. Oiliness or film strength. The ability of a lubricating oil to maintain lubrication between sliding or moving surfaces under pressure and at local high temperature areas is known as the oiliness or film strength of the oil. Film strength is the result of several oil properties, the most important being viscosity.

 
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10. Color. The color of a lubricating oil is useful only for identification purposes and has nothing to do with lubricating qualities. If the color of a nonadditive oil is not uniform, it may indicate the presence of impurities; however, in additive lubricating oils, a nonuniform color means nothing.

11. Ash. The ash content of an oil is a measure of the amount of noncombustible material present that would cause abrasion or scoring of moving parts.

12. Gravity. The specific gravity of an oil is not an index of its quality, but is useful for weight and volume computation purposes only.

13. Sulphur. The test for sulphur indicates the total sulphur content of the oil and does not distinguish between the corrosive and noncorrosive forms. A certain amount of noncorrosive sulphur compounds is allowable, but the corrosive compounds must be eliminated because of their tendency to form acid when combined with water vapor.

14. Detergency. The ability of an oil to remove or prevent accumulation of carbon deposits is known as its detergent power.

7A4. Viscosity of lubricating oils. The viscosity of a lubricating oil at the operating temperature in the engine is one of the most important considerations in selecting oil, since viscosity is the characteristic that determines film thickness and the ability to resist being squeezed out. The viscosity of an oil changes with temperature. Therefore, the viscosity should be measured at the operating temperatures of that particular part of the engine which the oil is to lubricate. From the viewpoint of lubrication, engines can be considered in two classes, those in which the cylinders and bearings are lubricated separately, and those in which only one lubricating system is used. If there are separate lubrication systems for cylinders and bearings, it is possible to use two grades of oil, the heavy one for cylinders and a medium one for bearings. The operating temperature to which the oil is subjected in the cylinders is naturally much higher than in the bearings. Also the motion in a cylinder is sliding, and a heavier oil is required to provide sufficient body to prevent metallic contact and

  wear. In the bearings, however, the temperatures are lower and the rotation tends to create a fluid film permitting a lighter oil to be used. When a single lubricating system supplies oil to cylinders and bearings, it is necessary to compromise on an oil that will do the best job possible in both places. All modern submarine diesel engines are of the latter type, having a single lubricating system.

Temperature, however, is not the only consideration in selecting an oil of the proper viscosity. Clearances, speed, and pressures are also important factors. Their effects on required viscosity may be summarized as follows:

1. Greater clearances always require higher viscosity.

2. Greater speed requires lower viscosity.

3. Greater load requires higher viscosity.

The oil selected for a diesel engine is therefore a compromise between a high- and a low-viscosity oil. Most high-speed engines run better using low-viscosity oils, but the viscosity must not be so low that the oil film wedge is too thin for efficient lubrication. On the other hand, oil of a greater viscosity than necessary should not be used because:

1. An oil of too great a viscosity increases starting friction.

2. Increased friction raises oil temperatures, and thereby promotes oxidation.

3. The more viscous oils usually have a higher carbon residue.

4. An oil of too great a viscosity places an overload on the lubricating oil pump with a possible inadequate supply reaching some moving parts.

For practical purposes the viscosity is determined by noting the number of seconds required for a given quantity of oil to flow through a standard orifice at a definite temperature. For light oils the viscosity is determined at 130 degrees F, and for heavier oils at 210 degrees F. The Saybolt type viscosimeter with a Universal orifice is used for determining the viscosity of lubricating oils. The longer it takes an oil to flow through the orifice, at a given temperature, the heavier or more viscous the oil is considered.

7A5. Tests. Viscosity tests are frequently conducted on board ship to determine the amount of dilution caused by leakage of fuel oil

 
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into the lubricating oil system. The test is made with a Visgage (Figure 7-1), a small instrument consisting of two glass tubes, each of which contains a steel ball, and a scale calibrated to indicate seconds Saybolt Universal (SSU) at 100 degrees F. One of the glass tubes is sealed and contains oil of a known viscosity. The other has a nozzle at one end and contains a plunger with which the oil to be tested is drawn into the tube. The instrument should be warmed by hand for a few minutes so that the temperature of the sample oil will be the same as that of the oil sealed in the master tube. Then, starting with both steel balls at the zero marking on the scale, the instrument is tilted so that the balls will move through the oil. On the instant that the leading ball reaches the 200 marking at the end of the scale, the position of the other ball in relation to its scale is noted. That reading indicates the viscosity of the sample oil in SSU at 100 degrees F direct.

The percentage of dilution of the lubricating oil by the diesel fuel oil is determined by use of the viscosity blending chart. This chart is essentially a graph of oil viscosity against percentage. Both right and left vertical boundary lines are marked in terms of viscosity SSU. The horizontal lines are divided into percentages from 0 to 100 percent. In using the viscosity blending chart, a line is drawn between the lubricating oil viscosity marked on the left vertical boundary line and the diesel fuel oil viscosity marked on the right vertical boundary line. This line represents only one particular lubricating oil viscosity. Figure 7-2 is an expanded portion of one section of a viscosity blending chart with lines drawn in for Navy symbol lubricating oils most commonly used. To determine the percent dilution of a lubricating oil, the viscosity of a test sample of the used oil is obtained, usually with a Visgage. The intersection of this valve on the chart with the line representing the Navy symbol oil in use gives a direct reading of the percentage of dilution on the horizontal scale.

Example:

SSU at 100 degrees F
New lubricating oil, viscosity 9250550
Diesel fuel oil37
Used lubricating oil (measured by Visgage)420
  Figure 7-1. Visgage.
Figure 7-1. Visgage.

As shown on the chart, the dilution is approximately 5 percent.

7A6. Detergent lubricating oils. Detergent or additive oils as they are usually called, consist of a base mineral oil to which chemical additives have been added. The additive agent has the following beneficial effect on the performance of the base lubricant:

1. It acts as an oxidation inhibitor.

2. It improves the natural detergent property of the oil.

3. It improves the affinity of the oil for metal surfaces.

For Navy use, heavy duty detergent lubricating oils of the 9000 series are used in most diesel installations. The use of these oils in a diesel engine results in a reduction in ring sticking and gum or varnish formation on the piston and other parts of the engine. In dirty engines, a heavy duty detergent oil will gradually remove gummy and carbonaceous deposits. This material being carried in suspension in the oil will

 
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Figure 7-2. Section of viscosity blending chart.
Figure 7-2. Section of viscosity blending chart.
 
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tend to clog the oil filters in a relatively short time. Normally, a dirty engine will be purged with one or two fillings of the sump, depending upon the condition of the engine and the quantity of the oil used. During the cleaning-up process, the operator should drain the sump and clean the filter if the oil gage indicates an inadequate oil flow.

In using additive or detergent type oils the following points should be considered:

1. All Navy approved oils are miscible. However, to obtain the maximum benefit from additive oils, they should not be mixed with straight mineral oils except in emergencies.

2. Detergent oils on the approved list are not corrosive. Should ground surfaces be found etched, or bearings corroded, it is probable that contamination of the lubricant by water or partially burned fuel is responsible. It is important that fuel systems be kept in good repair and adjustment at all times. The presence of water or partially burned fuel in lubricating oil is to be avoided in any case, whether mineral oil or detergent oil is used. However, small quantities of water in the Navy symbol 9000 series oils are no more harmful than the same amount of water in straight mineral oils. They will not cause foaming nor will the additives in the oils be precipitated

7A7. Sludge. Almost any type of gummy or carbonaceous material accumulated in the power cylinder is termed sludge. The presence of sludge is dangerous for several reasons:

1. Sludge may clog the oil pump screen or collect at the end of the oil duct leading to a bearing, thereby preventing sufficient oil from reaching the parts to be lubricated.

2. Sludge will coat the inside of the crankcase, act as an insulation, blanket the heat inside the engine, raise the oil temperature, and induce oxidation.

3. Sludge will accumulate on the underside of the pistons and insulate them, thereby raising piston temperatures.

4. Sludge in lubricating oil also contributes to piston ring sticking.

Sludge is usually formed by one or a combination of the following causes:

1. Carbon from combustion chambers.

  2. Carbon caused by the evaporation of oil on a hot surface, such as the underside of a piston.

3. Gummy, partially burned fuel which gets past the piston rings.

4. An emulsion of lubricating oil and water which may have entered the system.

Sludge is often attributed to the breaking down of lubricating oil, but generally this is not true.

Sludge gathers many dangerous ingredients, such as dust from the atmosphere, rust caused by water condensation in the engine, and metallic particles caused by wear, which contribute to premature wear of parts and eventual break down of the engine.

7A8. Bearing lubrication. The motion of a journal in its bearing is rotary, and the oil tends to build up a wedge under the journal. This oil wedge lifts the journal and effectively prevents metallic contact. The action of the oil film is explained in Figure 7-3 which illustrates the hydrodynamic theory of lubrication. This theory, involving the complete separation of opposing surfaces by a fluid film, is easily understood when the mechanism of film formation in a plain bearing is known. The diagram shows first the bearing at rest with practically all of the lubricant squeezed from the load area. Then, as rotation begins, an oil film is formed which separates the journal from the bearing. When rotation starts with the clearance space filled with oil there is a tendency for the journal to climb or roll up the bearing as a wheel rolls uphill. As the center of the bearing does not coincide with the center of the journal, the clearance space is in the form of a crescent with its wedge-shaped ends on either side of the contact or load area. Because of the fact that oil is adhesive and sticks to the journal, rotation causes oil to be drawn into the wedge-shaped space ahead of the pressure area. As the speed of rotation increases, more oil is carried into the wedge by the revolving journal, and sufficient hydraulic pressure is built up to separate completely the journal and bearing. When this film has formed, the load on the journal tends to

 
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Figure 7-3. Formation of bearing oil film.
Figure 7-3. Formation of bearing oil film.
cause it to drop to the lowest point. However, the pressure built up in the converging film ahead of the pressure area tends to push the journal to the other side of the bearing. The wedging action of the oil builds up a film pressure of several hundred pounds per square inch. The oil pump pressure, however, need only be sufficient to insure an adequate supply of oil to the bearings. All oil openings should be in the low-pressure section of the bearing in order to keep the lubricating oil pump pressure to a minimum. Diesel bearing pressures normally are not much over 1000 psi, and an oil film of straight mineral oil will usually withstand pressures of over 5000 psi.

The viscosity required to produce the proper oil film thickness depends on several factors. A rough or poor bearing needs a more viscous oil than a smooth, properly fitted bearing. Bearing clearances should always be enough to form an oil film of the proper thickness. Excessive bearing clearances reduce the oil pressure and only an excessively viscous oil will stay between the bearing surfaces. The greater the load on the bearing, the greater the oil viscosity required to carry the load. On the other hand, higher speeds permit a reduction in viscosity since the high shaft rotation helps build up the oil film pressure.

Bearing trouble and failure are usually attributable to improper lubrication. This may

  result from either a lack of sufficient lubricant or the use of an improper lubricant. Lack of lubricant may be due to excessive bearing wear, excessive bearing side clearance, low oil level, low oil pressure, and plugged oil passages. Failure, due to the use of an improper oil, results not only from incorrect original lubricant, but more frequently from continued use of an oil that should be replaced. Viscosity, in particular, is subject to change due to bearing temperature variation, dilution by unburned fuel, and oxidation. Bearing temperature variation is controlled by the proper operation of the cooling system. Lubricating oils may become corrosive in service, due to contamination by products of combustion or to inherent characteristics of the oil itself. Bearing corrosion is, of course, most likely to occur at high temperatures.

To insure against corrosion, the lubricating oil should be changed frequently, especially if oil temperatures are high or if easily corroded bearing materials are used. A pitted bearing usually indicates corrosion, which may be due to fuel, lubricant, or water.

7A9. Cylinder lubrication. The oil supplied to the cylinders must perform the following functions:

1. Minimize wear and frictional losses.

2. Seal the cylinder pressures.

3. Act as coolant.

 
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If no lubricant were employed, the metal surfaces would rub on one another, wearing away rapidly and producing high temperatures. The cylinder oil must prevent, as much as possible, any metallic contact by maintaining a lubricating film between the surfaces. Since oil body, or viscosity, determines the resistance of the oil against being squeezed out, it might seem that the thicker the oil, the better. This holds true in regard to wear, but there are other factors to be considered The body of the oil which prevents the film from being removed from the rubbing surfaces also provides a drag, resisting motion of the piston and reducing the power output of the engine. In addition, an oil that is too heavy does not flow readily, and spots on the cylinder walls remote from the point of lubrication may remain dry, causing local wear. Very heavy oils tend to remain too long on the piston lands and in ring grooves. While this condition may result in lower oil consumption, it will eventually cause gumming due to oxidation of the oil, and the final result will be sticky rings. For cylinder lubrication, therefore, it is desirable to use the lightest possible oil that will still keep the cylinder walls and piston lubricated. Use of a light oil will result in faster flow of the oil to the parts requiring lubrication, reduce starting wear, and minimize carbon deposits. This will result in lower fuel consumption, lower temperatures, longer periods between overhauls, and finally, lower total operating costs The lubricating oil consumption will probably be slightly higher, but the saving in fuel alone will more than make up for the additional lubricating oil expense.

The sealing function of the oil is tied in with its lubricating property. In order to make a good seal, the oil must provide a film that will not be blown out from between the ring face and the cylinder wall nor from the clearance space between the ring and the sides and back of the ring groove. The effectiveness of this seal depends partly upon the size of the clearance spaces. With a carefully fitted engine, in which clearances are small, a light oil can be used successfully. If the oil is heavy enough to provide a good seal, it will have a good margin of safety for the requirement usually stressed, that of preventing metallic contact.

  The oil aids in cooling by transmitting heat from the piston to the cylinder wall. To fulfill this requirement the oil should be as light as possible, since with light oils there is more movement in the oil film, a condition which aids the transfer of heat.

7A10. Navy specifications and symbols for lubricating oil. The symbol numbers used in Navy lubricating oil classification tables are for the ready identification of the oils as to use and viscosity. Each number consists of four digits, of which the first classifies the oil according to its use, and the last three indicate its viscosity. For example, the symbol 2250 indicates that the oil is a force feed oil (viscosity measured at 130 degrees F) and has a viscosity of 250 seconds Saybolt Universal. The following is a list of the classification of lubrication oils as to use:

Series Classification Navy Symbol
Examples
1000 Aviation oils 1065, 1080, 1100, 1120, 1150
2000 Forced feed oils (viscosity measured at 130 degrees F) 2075, 2110, 2135, 2190
3000 Forced feed oils (viscosity measured at 210 degrees F) 3065, 3080, 3100
4000 Compound marine engine oils 4065
5000 Mineral marine engine and cylinder wall oils 5065, 5150, 5190
6000 Compounded steam cylinder oil (tallow) 6135
7000 - -
8000 Compounded air compressor cylinder oils 8190
9000 Compounded or additive type heavy duty lubricating oils (viscosity measured at 130 degrees F) 9110, 9170, 9250, 9370, 9500
 
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The most common lubricating oil classification is that known as the SAE (Society of Auto motive Engineers) classification. Since the SAE numbers are more generally used outside of the Navy, a comparison showing the viscosity limits of the various numbers is given in the accompanying table.  
SAE No. Viscosity Seconds Saybolt
At 130 degrees F At 210 degrees F
10 90-120
20 120-185
30 185-255
40 255- 80
50 80-105
60 105-125
70 125-150
 
B. LUBRICATING SYSTEMS
 
7B1. Basic requirements of a lubricating system. Lubrication is perhaps the most important single factor in the successful operation of diesel engines. Consequently, too much emphasis cannot be placed upon the importance of the lubricating oil system and lubrication in general. It is not only important that the proper type of oil be used, but it must be supplied to the engine in the proper quantities, at the proper temperature, and provisions must be made to   remove any impurities as they enter the system. In general, the basic requirements that a lubricating system must meet to perform its functions satisfactorily are:

1. An effective lubricating system must correctly distribute a proper supply of oil to all bearing surfaces.

2. It must supply sufficient oil for cooling purposes to all parts requiring oil cooling.

3. The system must provide tanks to

Figure 7-4. General arrangement of lubricating off tanks.
Figure 7-4. General arrangement of lubricating off tanks.
 
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collect the oil that has been used for lubrication and cooling, so that it can be recirculated throughout the system.

4. The system must include coolers to maintain the oil temperature within the most efficient operating temperature range.

5. In order to exclude dirt and water from the working parts of the engine, filters and strainers must be included in the system to clean the oil as it circulates.

6. Adequate facilities must be provided on the ship for storing the required quantity of lubricating oil necessary for extensive operation and for transferring this oil to the engine lubricating systems as needed.

7B2. Ship's lubricating oil tanks and sumps. A typical lubricating oil system installation on recent submarines consists of three normal lubricating oil tanks and one reserve lubricating oil tank. These tanks are located inside the pressure hull adjacent to the engineering spaces and have approximately the following capacities:

Normal lubricating oil tank No. 1 1534 gallons
Normal lubricating oil tank No. 2 973 gallons
Normal lubricating oil tank No. 3 1092 gallons
Reserve lubricating oil tank 1264 gallons

In addition to these storage tanks, there is a sump tank under each main engine and under each of the two reduction gears. These tanks collect the oil as it drains from the engine oil pans. The sump tanks are always partially filled in order to insure a constant supply of oil to the lubricating oil pumps. As, the sump tanks are never completely filled with lubricating oil, their capacity is usually indicated as 75 percent of the actual total tank capacity. The approximate capacities of the various sump tanks (at 75 percent) are:

Main engine sump tanks Nos. 1, 2, 3, 4 382 gallons each
Motor and reduction gear lubricating oil sumps Nos. 1, 2 165 gallons each
  A filling connection is provided on the main deck to a five-valve filling and transfer manifold located on the starboard side of the forward engine room. This manifold is connected not only to the filling connection, but also directly to each of the normal lubricating oil tanks and the reserve lubricating oil tank. The oil to fill the tanks normally is passed through a strainer before it reaches the filling and transfer manifold. This oil strainer may be bypassed. A drain from the bottom of the strainer makes it possible to drain out any salt water that might have leaked into the filling line through the outboard filling connection.

The tanks are provided with vents and air connections from the 225-pound air service lines. By the use of these lines, lubricating oil may be blown from any lubricating oil storage tank to any other lubricating oil tank. Oil to be discharged may be blown or pumped overboard through the deck filling connection or through a hose connection in the filling line.

7B3. Operation of engine lubricating oil system. Oil is drawn from the sump tank by the attached lubricating oil pump. The discharge from this pump passes through the lubricating oil strainer. Between the discharge side of the pump and the strainer is a relief valve built integral with the pump. From the strainer the oil is carried to the lubricating oil cooler and thence to the engine main lubricating oil headers. The strainer is always placed forward of the cooler in the system because, if the temperature of the lubricating oil is higher, its filtering efficiency will be greater and the power necessary to force the oil through the strainer will be less.

In most installations the lubricating oil goes from the main lube oil headers to the engine main bearings and thence to the connecting rod bearings. The oil then passes through a drilled hole in the connecting rod up to the piston pin bearing which it lubricates and sprays out onto the under surface of the piston crown. Next, it drains down into the oil drain pan, carrying away from the piston much of the heat caused by combustion. From the oil pan, the oil drains to the engine sump tank from which it is recirculated

 
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Figure 7-5. Typical lubricating oil flushing and filling system.
Figure 7-5. Typical lubricating oil flushing and filling system.
 
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Between the oil pan and the sump tank, screens and basket type strainers may be inserted to prevent small metallic particles from draining down into the sump tank.

Lubricating oil for the main generator bearings is also provided by the main lubricating oil system. The oil used for this purpose is piped from the main lubricating oil line, at a point just before it enters the engine oil header, to the tops of the generator main bearings. From the bottoms of the bearings, the oil drains back to the sump tank, either directly or through the engine oil system.

The attached lubricating oil pumps are driven directly by the engines and therefore cannot be used for priming the lubricating oil system before starting. For this purpose, detached lubricating oil service pumps are provided, one in each engine room. These pumps should be started approximately five minutes before starting an engine. When an engine has been started and its attached pump is supplying oil to the engine system, the service pump may be shut down. The service pumps may also be used to circulate lubricating oil to cool an engine after it has been stopped.

Figure 7-5 shows a typical lubricating oil flushing and filling system in one engine room. In this system the detached lubricating oil service pump may be used to prime the engine lubricating oil systems prior to starting, to replenish the sump tanks from the normal lubricating oil stowage tank, and possibly to flush out the engine lubricating oil system when necessary. When the system is used for priming, the detached service pump takes a suction from the sump tank and discharges the oil into the engine lubricating oil system at the discharge side of the attached lubricating oil pump. When the detached pump is used for replenishing the sump tanks, it takes a suction from the normal lubricating oil tank and discharges the oil to either sump tank as necessary.

Lubricating oil may be purified by drawing the oil from the sump tanks with the service pump and discharging the oil back to the sump tanks through a purifier. Figure 7-6 illustrates a typical main engine lubricating oil purifying system for one engine room. Two engines and

  their respective sump tanks are shown, together with the piping that connects these units with the auxiliaries necessary for lubricating oil purification. These include a lubricating oil purifier, detached lubricating oil service pump, lubricating oil heater, and lubricating oil filters. The normal path of the oil during purification is from the sump tanks to the lubricating oil service pump thence to the oil heater, the purifier, the filters, and then back to the sump tanks. In actual installations, the filling and flushing and the purifying systems are combined in one system. For clarity the systems are separated as shown in Figures 7-5 and 7-6.

The lubricating oil pumps are designed to deliver considerably more oil than is normally required to pass through the engines. This insures sufficient lubrication when changes in the rate of oil flow occur because of cold starting, changes in speed, changes in viscosity of the oil due to heat, or increases in bearing clearances.

Pressure gages are placed in the system to indicate the pressures of the lubricating oil entering the strainer, leaving the strainer, and entering the engine. Through a change in pressure readings at these gages, troubles such as air binding of pumps, broken supply lines, or dirty strainers may be localized and remedied.

The lubricating oil is cooled by fresh or salt water circulating through an oil cooler. The pressure of the lubricating oil is higher than the pressure of the water so that, in the event of a leak, water cannot enter the oil system.

7B4. Detached lubricating oil service and standby pumps. All fleet type submarines use a detached lubricating oil service pump in each engine room for the purpose of supplying the purifier, filling the sump tanks from the storage tanks, and for flushing and priming the engine lubricating oil system. These ships also have a standby pump located in the maneuvering room for the purpose of filling the lubricating oil storage tanks, discharging used oil from the ship, and for transferring oil from one tank to an other. This pump also serves to supply the main motor bearings and reduction gears in the event that the oil pressure in that system drops below the safe operating limit, or the reduction gear sump pumps become inoperative. Both the

 
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Figure 7-6. Typical main engine lubricating oil purifying system in one engine room.
Figure 7-6. Typical main engine lubricating oil purifying system in one engine room.
 
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detached service and standby pumps are of the positive displacement type, driven by electric motors.

7B5. Lubricating oil coolers. The oil cooler is a Harrison radiator heat exchanger. This cooler is made up of a tube bundle or core and an enclosing case. The tubes are oblong and each tube encloses a baffled structure which forms a winding passage for the flow of oil. The tubes are fastened in place with a header plate at each end and with an intermediate reinforce ment plate. These plates are electroplated with tin. The tube and plate assembly is mounted in a bronze frame by means of which the tube bundle is fastened to the covers on each end of the casing.

The header plates, at the end of the tubes, separate the water space in the casing from the lubricating oil ports in the end covers. The lubricating oil flows through the tubes in a straight path from one cover port to the other. The intermediate tube plate acts as a baffle to form a U-shaped path for the water, which flows around the outside of the tubes, from one opening in the bottom of the casing to the other.

All the lubricating oil coolers are provided with zincs which act as electrodes. Electrolytic action is always present in all water systems on a submarine, and these electrodes allow the zinc rather than the cooler tubes to be eaten away. Zincs are mounted on removable plates and should be replaced when they show marked deterioration.

In all cooling systems it is a universal rule that the pressure of the liquid cooled be greater than that of the cooling agent. In a lubricating oil cooler this means that the pressure of the lubricating oil should be greater than the pressure of the fresh or salt water, whichever is used. If a leak should develop in the system, the water would then be prevented from leaking into the lubricating oil.

7B6. Lubricating oil strainers and filters. a. General. Strainers and filters are incorporated in the lubricating oil system for removal of foreign particles. In most installations the oil is passed through two strainers located forward of the cooler. Filters generally are located in the

  lubricating oil purifying system on the discharge side of the purifier. Various types of strainers and filters may be found in service. Some strainers consist of an element of edge-wound metal ribbon, others use a series of edge type disks. Filters may employ absorption type cellulose, waste, or wound yarn elements which are replaced when dirty. A few of the commonly used strainers and filters are described in the following paragraphs.

b. Edge disk type strainer. The edge disk type of lubricating oil strainer consists of an assembly of thin strainer disks separated slightly by spacer disks. The lower end of this assembly is closed and the upper end is open to the strainer discharge. The oil comes into the strainer and is forced through the strainer disks into the center of the strainer assembly. The oil then passes up through the assembly and out the top of the strainer. In passing through the strainer, the oil must pass through the slots between the strainer disks. In the bottom of the strainer element a relief valve is provided to avoid the possibility of excess pressure building up in the strainer should the slots become filled with foreign matter. This relief valve bypasses the oil up through the center of the strainer element and out the strainer discharge. The valve is set to open when the differential pressure reaches 10 psi. The disadvantage of this relief valve is that its functioning allows any foreign matter that may have collected in the bottom of the strainer to pass to the discharge side of the strainer and into the lubricating oil system.

When the assembly is turned by means of the external handle, the solids that have lodged against or between the disks are carried around until they meet the stationary cleaner blades. The stationary cleaner blades comb the solids clear of the strainer surface. The solids are compacted by the action of the cleaner blades and fall into the sump where they are filtered out of the stream of incoming oil. To keep the strainer in its clean and free filtering condition, the external handle is given one or more complete turns in a clockwise direction at frequent intervals. It is therefore not necessary to break any connections or interrupt the flow of oil through the strainer to clean the strainer unit.

 
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Figure 7-7. Cutaway of latest type Harrison heat exchanger.
Figure 7-7. Cutaway of latest type Harrison heat exchanger.
 
Figure 7-8. Cutaway of older type Harrison heat exchanger showing internal construction.
Figure 7-8. Cutaway of older type Harrison heat exchanger showing internal construction.
 
143

Figure 7-9. Edge disk type oil strainer.
Figure 7-9. Edge disk type oil strainer.
If the handle turns hard it indicates that the strainer surfaces have heavy deposits of solids on them. The handle should be turned frequently; there is no danger of turning the handle too often as there are no parts to wear out. If the strainer cannot be cleaned by turning, the head and disk assembly must be removed and soaked in a solvent until the solids have been removed. A wrench or other type of tool should never be used to turn the strainer handle. During periods of overhaul the head and disk assembly should be removed and the disk assembly rinsed in a clean solvent. The disk assembly should never be disassembled. If it is in such a condition as to warrant disassembly it should be replaced with a new unit. When cleaning the disk assembly, the strainer body and sump should be thoroughly drained and cleaned. Extreme care is necessary when cleaning the strainer, to prevent injury to the strainer element and the introduction of dirt and foreign material into the clean side of the strainer.

c. Edge-wound metal ribbon type strainer.

  This strainer, manufactured by the Purolator Company, is so constructed that the oil required by the engine is continuously filtered except when its filtering element must be removed for cleaning or servicing. When this is done, the control valve handle is turned to the bypass position. This shunts the oil flow through the filter head, permitting removal of the element without interruption of oil flow to the engine. Under normal conditions the oil comes into the strainer and surrounds the ribbon element. It then passes through and up the center of the strainer element to the outlet passage. One complete turn of the cleaning handle on top of the element rotates the element winding, and foreign material is removed from the element. The element consists of a cage of accurately spaced slots or perforations covered with a continuous, closely compressed coil of stainless steel wire. The wire is passed between rollers to produce a wedge-shaped wire or ribbon, one edge thicker than the other. On one side, projections are spaced at definite intervals while the other
 
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side is smooth. The projections on one side of the wire touch against the smooth side of the wire on the next coil to provide a spacing of approximately 0.005 inch. The thick edge of the wire is on the outside of the coil so that a tapered slot is formed through the coil, with the narrowest part of the slot on the outside. This insures that the dirt particles small enough to pass the outside, or narrowest point will not become stuck halfway and clog the oil flow. The dirt removed from the oil remains on the outside and can readily be removed by rotation of the cleaning handle.

The control valve handle on the strainer operates the bypass valve. When the handle is

Figure 7-10. Cutaway of edge-wound metal
ribbon type oil strainer.
Figure 7-10. Cutaway of edge-wound metal ribbon type oil strainer.

in the ON position, the lubricating oil is flowing through the strainer. When the handle is in the BYPASS position, the oil is flowing directly through the head of the unit, and the strainer case and element can be removed and cleaned. The ON and BYPASS positions are indicated on the strainer head.

  The pressure drop through the strainer is an indication of the condition of the straining element. When the pressure drop becomes abnormal and cannot be reduced by turning the cleaning handle, the strainer element should be removed and cleaned with an approved solvent. Care must be taken to prevent entrance of dirt to the inside of the element while it is being washed. The strainer element should not be cleaned with a wire brush or a scraper. The drain plug may be removed when the element is bypassed, thereby making it possible to drain out sludge and foreign material from the bottom of the strainer.

Most filters of this type have a relief valve installed in the lower end of the element. This valve lifts when there is a differential pressure of 7 to 10 psi. This design makes it possible for dirt to be bypassed to the clean side of the filter; therefore foreign matter must not be allowed to accumulate in the filter housing.

d. Absorption type filter. The absorption type filter consists of a number of cellulose, waste, or wound yarn filter elements supported in a steel container. The steel container is partitioned so that oil entering the tank completely surrounds all filter elements. A pressure relief valve mounted in the partition is permanently set to maintain the correct pressure differential across the filter for proper clarification. Oil in excess of the set pressure (usually about 20 psi) is discharged through the valve and the filter outlet from which it returns to the sump tank for recirculation.

Filters of this type vary considerably in design and construction but are similar in operating principle. Some designs employ only two large filter elements, while others may have over twenty. The location of the partition and the position of the relief valve and the inlet and outlet openings also vary depending upon the make and model of the filter.

7B7. Lubricating oil clarifier. a. General. Clarification of the lubricating oil is accomplished by the Sharples centrifuge which also serves as the fuel oil purifier (Section 5C4). The machine is set up as a clarifier by installing

 
145

Figure 7-11. Absorption type filter.
Figure 7-11. Absorption type filter.
a clarifier sleeve, or ring dam, on the top of the bowl, thus closing the outlet passage through which the water is discharged. The term clarifier is applied to the machine when it is set up to discharge a single liquid from which solid matter has been removed by centrifugal force. If the machine is set up to separate two liquids from solid matter and from each other (such as oil and water in a fuel oil purifier) it is called a separator. The machine is usually set up as a separator for fuel oil purification and as a clarifier for lubricating oil purification.

The lubricating oil purifier consists essentially of a rotor, or bowl, which rotates at high speeds. It has an opening in the bottom to allow the dirty lubricating oil to enter and two sets of openings to allow the oil and water or the water by itself to discharge. The bowl, or hollow rotor, of the centrifuge is connected by a coupling unit to a spindle which is suspended from a ball bearing assembly. The pulley of this bearing assembly is driven by an endless belt from an electric motor mounted on the rear of the frame.

  Tension on the belt is maintained by an idler pulley.

The lower end of the bowl is entered into a drag bushing mounted in the drag assembly. This is a flexibly mounted guide bushing. In side the bowl is a three-wing partition consisting of three flat plates equally spaced radially. The three-wing partition rotates with the bowl and its purpose is to force the liquid in the bowl to rotate at the same speed as the bowl. The liquid to be centrifuged is fed into the bottom of the bowl through the feed nozzle under pressure so that it jets into the bowl in a stream. For lubricating oil clarification the three-wing partition has a cone on the bottom against which the feed jet strikes to bring the liquid up to speed smoothly without making an emulsion. This cone is not necessary for fuel oil separation since fuel does not have the tendency to emulsify.

b. Operation. When a mixture of oil, water, and dirt stands undisturbed, gravity tends to effect a separation into an upper layer of oil,

 
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an intermediate layer of water, and a lower layer of the solid. When the mixture is placed in a rapidly revolving centrifugal bowl, the effect of gravity is negligible in comparison with that of centrifugal force, which acts at a right angle to the vertical axis of rotation of the bowl. The mixture tends to separate into a layer of solids against the periphery of the bowl, an intermediate layer of water, and a layer of oil on the inner surface of the water. The discharge   holes of the bowl may be so arranged that water can be drawn off and discharged into the upper cover. The solids will deposit against the wall of the bowl, to be cleaned out when necessary or as operations permit.

If an oil contains no moisture, it need only be clarified, since the solids will deposit in the bowl, and the oil will discharge in a purified state. If, however, the oil contains some moisture, the continued feeding of wet oil to the bowl

Figure 7-12. Cross section of Sharpies purifier.
Figure 7-12. Cross section of Sharpies purifier.
 
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results eventually in a bowl filled with water, and from that time on, the centrifuge is not accomplishing any separation of the water from the oil. Even before the bowl is completely filled with water, the presence of a layer of water in the bowl reduces the depth of the oil layer. As a result, the incoming oil passes through the bowl at a very high velocity. This higher velocity means that the liquid is under centrifugal force for a shorter time, and the separation of water from the oil is, therefore, not so complete as it would be if the bowl were without the water layer, or if the water layer were a shallow one. Because of this, the centrifuge should not be operated as a clarifier unless the oil contains very little or no water. A small amount of water can be satisfactorily accumulated, together with the solids, to be drained out when the bowl is stopped for cleaning, but if there is any appreciable amount of water in the oil, the bowl should be operated as a separator.

The length of time required to clarify lubricating oil is determined to a great extent by the viscosity of the oil. The more viscous the oil, the longer it takes to purify it to a given degree of purity. The use of a pressure in excess of that normally used to force a high-viscosity oil

  through the purifier will result merely in less efficient purification. Decreasing the viscosity of the oil by heating is therefore one of the most effective methods of facilitating purification.

The capacity rating of the centrifuge is based on the use of 2190 oil at 130 degrees F, which represents a viscosity of approximately 200 SSU. For good results no oil should be purified at a higher viscosity than this and other oils may need to be heated above 130 degrees F to reach 200 SSU. (See temperature table below.)

A reduction in the pressure at which the oil is forced into the centrifuge will increase the length of time the oil is under the influence of centrifugal force, and therefore will tend to Improve results. The effective output of the machine in any case will depend on viscosity, pressure, the size of the solid particles, the difference in specific gravity between the oil and the water, and the tendency of the oil to emulsify. If a used lubricating oil contains no water, but merely metallic particles, it may be cleaned at a higher rate (high input pressure). If the same oil contains a large percentage of water, and has a tendency to emulsify, the input pressure will necessarily have to be lower to obtain the required degree of purity.

 
TEMPERATURE TABLE
Oil,
Navy symbol
Temperature*
in degrees F
Oil,
Navy symbol
Temperature*
in degrees F
Oil,
Navy symbol
Temperature*
in degrees F
1042 89 2135 116 5065 143
1047 102 2190 129 5150 190
1065 137 2250 142 5190 209
1080 151 3050 119 6135 192
1100 166 3065 135 7105 173
1120 179 3080 154 8190 128
1150 190 3100 163 9170 123
2075 92 3120 180 9250 140
2110 95 4065 140 9370 158
* Minimum temperature of oil to obtain viscosity of 200 SSU
 
C. GENERAL MOTORS LUBRICATING SYSTEM
 
Oil for the GM lubricating system is circulated by the positive displacement attached lubricating oil pump driven through the camshaft drive gear train. This pump draws oil from the sump tank,   passes it through a safety relief valve at the discharge side of the pump, then through a lubricating oil strainer and a cooler. From the cooler, the oil enters the engine's main lubricating oil manifold. After circulating through the various
 
148

Figure 7-13. Lubricating oil system, GM.
Figure 7-13. Lubricating oil system, GM.
passages in the engine, the oil drains into the engine oil pan and then back into the sump tank from which it is recirculated.

Oil for the generator bearings is taken from the lubricating oil piping between the cooler and the engine inlet. When the engine is running, the bearing drains are placed under a suction head by the attached generator bearing scavenging pump to prevent flooding of the main generator bearings. The plug cock in the gravity drain line leading from the generator bearings to the sump tank is closed and the oil is drawn from the bearing drains into the engine lubricating system, whence it drains into the oil pan and back to the sump tank. Before starting, or when flushing the engine with the detached lubricating oil service pump, the plug cock in the gravity drain line is opened, permitting the oil to drain directly into the sump tank.

Mercury type thermometers are located at the lubricating oil cooler inlet and at the engine

  inlet. A bypass line with a relief valve is provided to bypass the cooler when for any reason the cooler cannot handle the full flow volume. This bypass is also used when cooling of the oil is not required, as when starting an engine in cold weather.

Engines on SS 313 to 318 have a relief valve set at 80 psi. All other engines for the SS 313 Class have a 30-pound differential pressure relief valve. The 80-pound relief valve is not considered satisfactory for this service.

Duplex type pressure gages are provided in the system to register the oil pressure at the engine inlet and at the inlet and outlet of the lubricating oil strainer. The system is provided with a low-pressure alarm consisting of a pressurestat at the engine inlet which energizes a horn and light whenever the oil intake drops to 15 psi or less. Continuous reading type thermometers indicate the temperature of the oil drain from the engine and the generator bearings.

 
149

Figure 7-15. Crankshaft oil passages, GM.
Figure 7-15. Crankshaft oil passages, GM.

7C2. Engine lubricating system. The lubricating oil enters the engine at a connection on the control side of the camshaft drive housing. The relief valve ahead of the inlet keeps the pressure of the oil at 40-50 psi. Any oil bypassed by the relief valve returns to the camshaft drive housing from which it drains to the oil pan.

From the engine inlet connection, the oil flows to the main lubricating oil manifold which extends the length of the engine and is bolted to the bottom of the main bearing supports. The oil flows from the manifold up through drilled passages in the supports to each main bearing. The crankpin bearings are lubricated with oil that is received from the adjacent main bearings through oil passages in the crankshaft. A drilled passage in the connecting rod conducts this oil to the piston pin bearing and to the piston cooling chamber formed by an integral baffle under the piston crown. Lubricating oil under pressure flows from the top of the connecting rod, through an oil sealing assembly and into the cooling

 

Figure 7-16. Piston and piston pin lubrication
and cooling, GM.
Figure 7-16. Piston and piston pin lubrication and cooling, GM.

chamber. The sealing assembly consists of a bronze oil seal saddle which rides on the machined top of the connecting rod and is held against the connecting rod by a spring. The heated oil overflows through two openings in the integral baffle and down to the oil pan from which it drains to the sump tank.

The lubricating oil for the camshaft drive gear train is supplied by branch lines from the main lubricating oil manifold. These branch lines conduct oil to the lubricating oil distributor block on each side of the camshaft drive housing. From each of the distributor blocks a pipe supplies oil to each camshaft drive gear bearing. The drilled camshafts are supplied with oil through passages in the camshaft gear hubs and the camshaft drive sleeves. The oil then passes through the hollow camshafts and supplies the camshaft bearings by radial holes through the camshaft bearing journals. Oil for lubricating the rocker levers and cam rollers flows through a tube from the camshaft bearing cap at each

 
150

Figure 7-14. ENGINE LUBRICATING SYSTEM, GM.

Figure 7-17. Camshaft drive lubrication, GM.
Figure 7-17. Camshaft drive lubrication, GM.
 
151

Figure 7-18. Attached lubricating oil pump, GM.
Figure 7-18. Attached lubricating oil pump, GM.
engine cylinder. This oil also lubricates the valve assemblies. The oil flows from the end of the camshafts down the camshaft drain tubes to the engine oil pan.

Each rocker lever assembly is lubricated with oil that is received from an adjacent camshaft bearing. The oil flows from the top of the camshaft bearing through a tube to the plate connection that is fastened to one end of the rocker lever shaft. From this connection, the oil flows through drilled passages in the rocker lever shaft to the three bearings in the rocker lever hubs.

A drilled passage in each of the rocker lever forgings conducts the lubricating oil from a hole in the hub bushing to the camshaft end of the lever. The rocker lever motion permits oil to flow intermittently under pressure from the hole in the shaft, through one hole in the bushing and rocker lever to the cam roller. The bearing in each of the cam rollers receives oil through drilled holes in the roller pin and in the bearing bushings.

  Oil from the cylinder heads and valve operating gear drains through the micrometer link passages to the control shaft compartment and thence through tubes to the crankcase.

A manifold, bolted to the blower end of the main lubricating oil manifold, supplies the lubricating oil for the blower gears and bearings, and the accessory drive gears and bearings. The manifold carries oil to the blower rear end plate, to the blower front end plate, and the accessory drive housing. Steel tubing cast into the ribs of the end plates and the housing carries the lubricating oil to the blower drive gear bearings and to the gear bearings in the accessory drive. Excess oil drains through the lower blower housing into the oil pan.

The engine main lubricating system also furnishes lubricating oil to the overspeed governor. When the engine speed exceeds a predetermined limit, this lubricating oil is pumped under pressure to the overspeed injector lock on each cylinder head and prevents the injector from operating.

 
152

7C3. Attached lubricating oil pump. The lubricating oil pump used for the GM pressure lubricating system is mounted on the camshaft drive housing cover and is a positive displacement helical spur gear type pump.

The lubricating oil pump body and body base are bronze castings. The spur gears and shafts are integral forgings and the shafts revolve on bronze bushings which are pressed into the housing and cover, the cover being used to close the outside of the body.

The spur gear that does the driving has its shaft extended and splined to fit into the hub of

  the oil pump drive gear. The camshaft drive gear meshes with the oil pump drive gear to operate the pump.

A spring-loaded pressure safety valve is frequently attached to the lubricating oil pump to prevent the lubricating oil pressure in the system from exceeding a safe operating pressure, The spring pressure is adjusted with a regulating screw which is enclosed by a cover on the valve head. The regulating screw is adjusted so that the valve opens when the lubricating oil discharged from the pump reaches a gage pressure of 90 pounds. The bypassed oil is returned to the suction side of the pump.

 
D. FAIRBANKS-MORSE LUBRICATING SYSTEM
 
7D1. General description. The lubricating oil system outside the engine in an F-M installation is similar to the GM system described in section 7C1. Lubricating oil is drawn from the sump tank by the attached positive displacement gear pump mounted on a plate at the control end of the engine and driven by the lower crankshaft through gears and a flexible coupling. From the attached pump, the oil is passed through a strainer and two coolers. Leaving the coolers, the oil is piped to the engine where it enters the lower lubricating oil header through an inlet flange. A pipe connection ahead of the engine inlet supplies lubricating oil to the generator bearings. After circulating through the engine, the lubricating oil drains into the engine oil pan and back to the sump tank for recirculation. Oil from the generator bearings returns directly to the sump tank.

An electrical resistance thermometer bulb is installed in the lubricating oil line between the pump and the strainer. Temperature of the oil at this point is indicated on a gage mounted on the engine gage board. This gage board also supports a duplex type pressure gage which indicates the pressure of the oil in the line between the strainer and the attached pump and in the line ahead of the engine inlet. Also near the lubricating oil inlet to the engine is a mercury bulb thermometer and a pressure static contact maker which closes a circuit to energize

  a low-pressure alarm signal whenever the lubricating oil pressure drops to 15 psi or less.

The coolers may be bypassed if the operating conditions warrant. In this bypass line a spring-loaded pressure relief valve, set to open at a pressure of 45 psi, is installed. This bypass and relief valve insures circulation of the oil should its viscosity be such as to cause a restricted flow through the coolers.

7D2. Engine lubricating system. Entering the lower lubricating oil header from the inlet near the control end, the oil flows through the lower header toward the blower end. There, a vertical pipe carries the oil to the upper header. Both headers extend longitudinally the entire length of the engine.

Through supply pipes from both lower and upper headers, oil is forced to each main bearing, and thence, through tubes swedged into the crankshaft, to each crankpin bearing. From each crankpin bearing, oil passes through the drilled passage in the connecting rod to the piston pin bearings and to the piston oil cooling pockets.

The surfaces between the thrust shells and the crankshaft flanges are lubricated through openings in the thrust bearing shells.

The cooling oil from each lower piston is discharged through the lower piston cooling oil outlet into the oil pan. Oil from each upper

 
153

Figure 7-19. Lubricating system, F-M.
Figure 7-19. Lubricating system, F-M.
piston is discharged through the upper piston cooling outlet into the compartment around the tipper ends of the cylinders. This oil can drain either to the blower or to the control end of the engine and then down to the oil pan.

The two camshafts receive lubrication from the upper oil header. Oil enters the hollow camshafts through the camshaft bearing at the control end of the engine, and small openings at each bearing journal allow oil to reach the camshaft bearing surfaces. An opening in the end of each camshaft, and excess oil from the No. 1 main bearing, supply oil to the timing chain at the control end of the engine. The oil spray from the timing chain provides lubrication for the bearings of the idler sprockets, for the control mechanisms, drive gears, and bearings of the governor, and for the water, fuel, and lubricating oil pumps. Spray from the timing chain also lubricates the air start distributor and the air start control valve located in the lower part of the control end compartment. The air start distributor valves admit a minute quantity of

  oil which is carried by the air to lubricate the air start check valves.

The drive bushings of the pump flexible drive (on the control end of the lower crankshaft) receive lubrication through an opening in the lower crankshaft from the control end main bearing.

Oil from the upper engine compartment enters the injection pump housing and lubricates the tappet assembly. The excess oil is drained through leads to a return header which conducts the oil to the control end compartment.

The blower drive gears are lubricated by sprays of oil from special nozzles located on each side of the centerline of the engine. These nozzles are attached to the oil piping connecting the lower and upper oil headers.

The blower flexible drive gear is lubricated through openings in the drive spider. Oil is brought to these openings from the nearest main bearing by means of drilled passages in the upper crankshaft.

 
154

Figure 7-20. ENGINE LUBRICATING OIL CIRCULATION. F-M.

Figure 7-21. Sectional views of F-M piston showing oil passages.
Figure 7-21. Sectional views of F-M piston showing oil passages.
 
Figure 7-22. Thrust bearing oil passages, F-M.
Figure 7-22. Thrust bearing oil passages, F-M.
 
155

Figure 7-23. Piston assembly oil passages, F-M.
Figure 7-23. Piston assembly oil passages, F-M.
  The inner and outer blower impeller bearings are lubricated by branches and oil tubes from the upper oil header.

The vertical drive gears and pinions are lubricated by a spray of oil from nozzles connected to the upper and lower oil headers by

Figure 7-24. Oil supply to camshafts, F-M.
Figure 7-24. Oil supply to camshafts, F-M.

Figure 7-25. Camshaft and camshaft bearing lubrication, F-M.
Figure 7-25. Camshaft and camshaft bearing lubrication, F-M.
 
156

Figure 7-26. Drive end of attached lubricating oil pump, F-M.
Figure 7-26. Drive end of attached lubricating oil pump, F-M.
 
Figure 7-27. Gear end of attached lubricating oil pump, F-M.
Figure 7-27. Gear end of attached lubricating oil pump, F-M.
 
157

tubes. Other tubes supply oil to the vertical drive pinion shaft roller and thrust bearings.

Having performed its various functions. the lubricating oil drips down into the oil pan below the lower crankshaft. From the oil pan, the oil drains into the sump tank from which it is recirculated.

7D3. Attacked lubricating oil pump. The attached lubricating oil pump used in the F-M pressure lubricating system is mounted on a pump mounting plate on the control end of the engine. It is driven, through gears and a flexible coupling, by the lower crankshaft. The pump is a positive displacement herringbone (impeller) gear type and consists essentially of a pump body, a driver and driven timing gear, a driver and driven impeller, inner and outer wearing plates, and inner and outer bearing plates. A

  spring-loaded relief valve, set at 50 to 60 pounds pressure, is located in the discharge opening of the pump body.

The impeller shafts are supported on bearings pressed into the bearing plates. The inner and outer wearing plates are located against the inner surfaces of the bearing plates and provide a clearance of 0.002 to 0.004 inch between the wearing plates and the impellers. The longitudinal clearance between the impellers and the pump body is 0.003 to 0.0045 inch. The driver timing gear is pressed on the end of the driver impeller shaft and the driven timing gear is pressed on the end of the driven impeller. Both timing gears are enclosed within the pump cover. The drive coupling is attached to the end of the driver impeller outside the outer bearing plate.

 
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