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Acknowledgements

This course was prepared by International Technical Services, a division of 984326 Ontario Inc., in cooperation with the General .\lotors Locomotive Group Customer Training Center, Technical Publications Dept. and Engineering Departments.

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The course content is based partialy on previous publications produced by the Training Center, and pardy on information gathered by the Training Center from Electro-Motive's Service and Engineering Departments. The contents of Chapter 7 were extracted from the EMD document, The Electro-Motive Turbocharger by William Badurski.

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Developed in Cooperation with the General Motors Locomotive Group ElectdMotive Customer Training Center.

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When the engine approaches full load, the heat energy in the exhaust, which reaches temperatures approaching 1000°F (538OC),is sufficient to drive the turbocharger without any help from the engine. At this point, an overrunning clutch in the drive train disengages and the turbocharger drive is mechanically disconnected from the engine gear train.

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COMPONENT FAMILIARIZATION The next section is designed for familiarization with the major turbocharger components. These include the doweling assembly, the turbine wheel, the geardrive assembly, etc. Minor pa& such as hardware, brackets, etc. will not be covered unless these items perform some special function.

Figure 7-1 Turbocharger

Turbocharger Nameplate

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Figure 7-2 Turbocharger Nameplate

Part Number .

The part number specifies exactly what model the turbo is; i.e., 16 cylinder marine turbo, etc. An EMD parts catalog such as #300 will provide a turbo application list on Parts List #174. This chart will indicate specifically what turbo is required on each engine.

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ElectrcMotive Model 567,645 & 710 Series Diesel Engines

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Serial Number

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The serial number indicates the date, production sequence number, and assembly location of the turbo. For example:

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Year (1988)

Month * (Jan)

Type * (New)

Plant * (LaGrange)

Sequence * (#5)

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A = January, B = February, etc. The letter “I” is not used, so a December built turbo carries an “M” designation.

* Type:

A “1 ” indicates a new unit. A “2” indicates a repaired and returned machine. A “3” indicates a Unit Exchange (UTEX) turbo.

* Plant:

There are three plants involved in the assembly of turbochargers. 1 = LaGrange, 11. 5 = Halethorp, Md. 6 = Commerce, Ca.

* Sequence:

The last three digits of the serial number indicate the sequence number of turbos built at a specific plant each month. The “005” in the example indicates that the turbo was the 5th one built at the LaGrange plant during the month of January, 1988.

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Identification Code

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The identification code indicates the turbo model, gear ratio, and most recent significant change or revision from the original design which was in effect at the time that the turbo was assembled. For example:

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Model

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Model:

E = 645 Engine Turbo; T = 567 Engines; G = 710 Engines

Ratio:

The gear ratio of the turbo with respect to engine crankshaft speed. An 18 indicates that the turbo runs at 18 times the crankshaft speed. 16.8:l and 17.9:l are also common gear ratios.

Revision:

There have been several revisions or improvements incorporated into the turbo since its inception. The letter code designates the latest revision which was applied to the turbo.

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Doweling Assembly The doweling assembly forms the backbone or casing for all the turbo’s internal components. The assembly is comprised of 6 iron castings, which are aligned to one another by dowels and held together by various threaded fasteners. The alignment of these parts is critical, and the bore through which the turbine wheel passes is held to a maximum of .0005 t.i.r. Consequently, during manufacture, the six pieces are aligned and then doweled to maintain that alignment. Next, they receive stamped “doweling numbers” which identify them as a matched set. In the event that one of these components becomes damaged during the life of the turbo, a new part must be aligned to the remaining set components. This new part will then receive a matching doweling number to identify it as part of the original set.

Figure 7-3 Turbocharger Doweling Assembly

The doweling assembly is comprised of the following: 1. COmpressor Scroll - Forms the scroll through which compressor air flows from the turbine wheel to the engine.

2. Compressor Bearing Support - Provides a location point for the turbine wheel compressor-end support bearing. (Also forms the rear half of the air scroll.)

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3 . Turbine Bearing Support - Provides a location for the rotating assembly turbine-end support bearing. (Also contains the planetary gear system on all turbos and the overrunning clutch on 567 and 645 turbos.)

- The central component to which the others attach.

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5. Idler Gear Support - Attaches to the “back of the turbo and contains various threaded holes for the attachment of the external gears which

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connect the rotating assembly to the engine gear train.

6. Carrier Bearing Support - Provides a location for the roller bearing which is used to support the planetary gear carrier shaft.

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Main Housing “Cradle”Gasket Area The gasketed surface between the main housing and compressor bearing support (which is known as the “cradle”) was changed from its original 3-piece conventional gasket design to incorporate improved sealing technology. The area which requires sealing is an oval-shaped oil drainage passage at the. bottom of the “cradle”. The original configuration utilized a paper-type gasket at the bottom one-third of the cradle sealing the opening. O n each side of the paper gasket was another made of metal shim stock. These 2 metal gaskets were not required for sealing purposes, but rather were necessary in that their thickness matched the compressed paper gasket thickness. Consequently, the metal gaskets served to maintain parallelism between the two doweling components when the paper gasket was installed. Due to the unfavorable environment in which the cradle gasket was located (heat and vibration), a more durable seal was desired. In the late 1970’s a revised sealing arrangement was released. The turbo main housing oil drain hole was changed from an oval shape to a double round hole configuration with counterbores for O-rings. The 0ring type turbos required no gaskets between the main housing and compressor bearing support. In order to improve the seal on older castings which were made with oval-shaped openings, a new seal was developed. This seal, known as the “Parker Seal”, is equipped with an oval-shaped O-ring on each side of a metal plate. The seal is retained by two of the doweling assembly through bolts. These improved seals can be applied to most turbos utilizing the oval oil drain configuration by simply machining a relief in the cradle flange of the turbo main housing during overhaul.

Figure 7-4 Original 3-Piece Cradle Gasket (Model Code Designations Prior to “R”)

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Figure 7-5 Parker Seal (,” Model Code Designations)

Electro-Motive Model 567,645 & 710 Serles Diesel Engines

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Double 0-Ring Application ("Wand Later Designations)

Turbine Wheel The turbine wheel or rotating assembly as it is sometimes called, is the heart of any turbocharger. It is comprised of a shaft, on which both the turbine blades (exhaust fan) and the impeller (air compressor fan) are located. The shaft is supported near each end by 2 support bearings. The bearing nearest the impeller is called the compressor bearing, and the one nearest the turbine blades is known as the turbine bearing. O n the EMD turbo, a small gear is located on the extreme end of the shaft near the turbine blades. This gear, in conjunction with a series of others, provides the connection of the turbine wheel to the engine crankshaft as previously discussed. T h e balance of the rotating assembly is extreme+ critical in order to ensure that vibrations which might occur at the high rotational speeds are minimized. Beginning at the impeller-end, the components of the rotating assembly are as follows: 1. Impeller Retaining Nut

- Plastic insert type.

2. Retaining Washer - Secures impeller on shaft. 3. Compressor Impeller - An aluminum castings (forging on 710 model) which contains the blades used to pump air. Blade quantities:

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567 & 645E/EB Models 645EC & 645FB Models 7 10-G Models

16 Blades 22Blades 34Blades

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Figure 7-7 lmpeller Design Comparisons

4. Impeller Spacer - A machined washer which acts as a portion of one of the 3 air seals along the rotating assembly shaft.

- The finished surface on the compressor portion of the shaft which corresponds to the compressor bearing.

5. Compressor Bearing Journal

6. Heat-Dam Washer - A large washerldisc featuring lands on the surface which contact the turbine wheel to minimize metal to metal contact, thus reducing heat transfer from the turbine wheel to the bearing surface. 7. Compressor Seal - A machined surface on the turbine wheel which acts as a portion of the‘second air seal along the rotating assembly shaft.

8. Turbine Wheel - The central hub of the rotating assembly, on which all the turbine blades are located. 9. Turbine Blades - The blades which collect the exhaust gas flow and cause the rotating assembly to turn. Numbers of blades: 567 & 645 All Models 710-B Models

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Sun Gear Shaft - The rotating assembly shaft is actually split into two parts. The turbine wheel forms the “front” end, containing the impeller and turbine blades, while the sun gear shaft forms the “rear” end. The sun gear shaft comprises 3 distinct components. a. Turbine Seal: A machined surface on the shaft which acts as a portion of the third air seal along the rotating assembly shaft. b. Turbine Bearing Journal: The finished surface on the turbineend of the shaft which corresponds to the turbine bearing. c. Sun Gear: A gear which is a part of the sun gear shaft, and acts as the central gear in the planetary geardrive system.

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ElectrMotive Model 567, 645 & 710 Series Diesel Engines

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Figure 7-8 Rotating Assembly

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Turbocharger Bearings As previously discussed, the rotating assembly is supported by two bearings which are located in the doweling assembly. Due to the high speeds and temperature levels that the turbine wheel is exposed to, the design and construction of these bearings is rather unusual. Both the compressor journal bearing and the turbine journal bearing are designed with cylindrical tapers which form oil wedges that develop powerful radially oriented hydraulic forces to center the rotating journals. Thus, rather than using a concentric bore on the inside diameter of the bearings, oil “ramps” are utilized. The hydraulic forces developed in the journal bearings and thrust bearing far exceed the engine lube oil pressure. Also, because these forces are generated by the rotating journals, the hydraulic forces increase as rotor speed increases. There may be 3,4, or 5 ramps on the inner surface of the rotating assembly support bearings. Each ramp begins at an oil “channel” or groove. The distance from the surface of the bearing to the journal is greatest at this point. As the ramp extends around the inside of the bearing, its height increases and the clearance between the bearing and the journal decreases. The difference in ramp “height” from the low-end at the oil channel and the high-end is approximately .003-,004”. The lubricating oil which is pumped into the bearings is drawn along the oil ramps by the rotation of the turbine wheel. As this oil flows along the ramp, the bearing clearance decreases, which increases the centering force exerted on the journal. This is known as a “hydra-dynamic” bearing design.

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Compressor Bearing: The hydra-dynamic bearing through which passes the impeller-end of the rotating assembly. The compressor bearing supports the compressor portion of the rotating assembly shaft. The inboard end of the compressor bearing is flared and manufactured with a convex surface to form a part of the thrust bearing assembly. The compressor bearing is located in the compressor bearing support, and is retained by an interference fit.

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Thrust Bearing: A disc-shaped bearing through which the turbine wheel shaft also passes. One side is concave to correspond with the flared end on the compressor bearing. These curved surfaces permit a self-aligning feature. The opposite side of the thrust bearing appears flat, but actually consists of a series of tapered pads on the thrust face which form oil wedges that develop hydraulic pressure to separate the bearing from the rotating heat dam thrust washer. 6

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The thrust forces found in the rotating assembly are caused by the pitch of the impeller blades. These blades are shaped to pull air through, similarly to the propeller on an airplane. Unlike the airplane, which uses this concept to pull the machine through the air, a turbocharger impeller must remain stationary to pump the air through its compressor section.

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It is the function of the thrust bearing to control the tendency of the turbine wheel to move forward. Exhaust pressure against the wheel also contributes to the load the thrust bearing must control. The thrust bearing is located between the flared edge of the compressor bearing and the heat dam washer on the turbine wheel.

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Turbine Bearing: This bearing supports the 2un gear end of the rotating assembly. Its construction is similar to that of the compressor bearing, except that it does not have the flared edge. The turbine bearing is located in the “clutch support”, which in turn is located in the turbine bearing support.

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Planet Gear Bearings: A set consisting of three identical bearings, one for each of the 3 planetary gears. These bearings differ from those previously discussed in that the oil ramp is on the outside diameter of the bearing. One bearing is installed in the bore of each planet gear, and the gears rotate on the stational? bearings.

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PLANET GEAR BEARING Pin Engagement Notch

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Figure 7-10 Turbocharger Bearings

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TURBINE BEARING

Turbocharger Labyrinth SeaIs The seals usedin the turbo utilize air pressure as the a c b d seal. No physical contact between the turbine wheel shaft and the seal occurs. Instead, pressurized air from the compressor scroll is ported to three “labyrinth” seals through a “bleed” air duct. Once in the seals, the air emits from a small hole in the bore through the center of the seal. This bore, through which the rotating assembly passes, contains several grooves or “labyrinths”.The air flows around the seal in these grooves, effectively sealing the area.

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Figure 7-1 1 Turbocharger Bearings 6.Labyrinth Seals

These seals are effective at separating the lubricating oil from the exhaust gases. However, improperly filtered air can form dirt deposits within the air passages, which will restrict the air flow and reduce the effectiveness of the seals. There are 3 labyrinth seals in the EMD turbo. 1. Impeller Seal: Located directly behind the impeller, this seal prevents oil in the compressor bearing area from being drawn out into the compressor air scroll by the suction created as the impeller spins.

2. Compressor Seal: This seal is located between the turbine blades and the compressor bearing. Its function is to prevent oil from migrating into the exhaust section from the compressor bearing.

3. Turbine Seal: The turbine seal is located between the turbine blades and the turbine bearing. It prevents oil from migrating into the exhaust duct from the turbine bearing.

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Turbine Inlet Scroll The high-energy exhaust gas is deliverecl to the single-stage turbine by the exhaust inlet scroll. This component is a welded assembly made from “chromemoly” plate which is formed so that the incoming gas flow is smoothly and evenly distributed with a minimum of turbulence.

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Figure 7-13 Turbine Inlet Scroll 6 Nozzle Ring

Nozzle Ring The nozzle ring is located in the exhaust portion or turbine section of the machine. The nozzle ring consists of a series of stationary vanes through which the exhaust gas from the engine must pass in order to reach the turbine blades. Each passage between the vanes is called a nozzle. The nozzle ring is therefore simply a ring of individual nozzles which are mounted on a common ring. The gas is throttled and directed by the nozzles into the turbine wheel blades. The size of the nozzle openings must be matched to the amount of exhaust gas generated by the particular engine that the turbo is designed for. Larger passages are found on nozzle rings for larger engines, etc. This is due to the fact that larger engines flow a higher exhaust gas volume than do small ones. Consequently, a small nozzle ring would choke a large engine’s exhaust gas flow. Conversely, a large nozzle on a small engine would not provide enough restriction for the gas flow to develop the correct amount of velocity as it flows through the passages. rd.

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The principle may be more easily understood if compared to a garden hose nozzle. As the nozzle opening is decreased more energy or force is obtained from the flow of the water. In the turbocharger, the optimum nozzle opening is just enough to allow an engine’s maximum exhaust gas volume to pass without creating a back-pressure. If the gas cannot flow through the nozzle quickly enough, it will begin to “back-up” in the exhaust system and the turbo will eventual1 “sur e”. The term surge refers to a reversal of the gas flow through the turbo. The mac ine actually “burps” exhaust back through the engine due to a greater pressure within the engine or exhaust system than that of the incoming air supply.

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Turbine Shroud and Retaining Clamp The turbine shroud is a metal band which encircles the turbine blades. Because the turbo’s power is generated by the exhaust gas between the blades, high efficiency is obtained by minimizing leakage around the blades. Consequently the turbine shroud is formed around the blade tips on the turbine wheel. The shroud’s function is to ensure that the exhaust gas flow across the turbine blades is maximized by reducing gas leakage around the blade tips. The blade tip to shroud clearance must be small enough to minimize gas leakage, but large enough to prevent contact with the blade tips as they enlarge through thermal growth. For this reason, the inside diameter of the EMD turbine shroud is Figure 7-14 Turbine Nozzle Ring sprayed with a “soft metal” abrasable coating. The blades can actually establish their own path in this coating as their temperatures normalize, creating a custom-fitting shroud for each individual turbo. The shroud is retained (in most turbo models) by a clamping ring known as the “Marmon Clamp”. This clamp consists of a metal band, to which 4 channel segments are spot-welded. The channels engage a flange on the edge of the turbine shroud, securing it within the turbo. A “T-bolt” and nut are used to apply clamping load to .the assembly. An improvement was made to the Marmon clamp in the early 1980’s. Prior to this improvement, the strap to which the T-bolt is attached was spot welded to the clamp. Tests in the field indicated that the clamp could suffer from metal fatigue in the area adjacent to these welds after repeated thermal cycling. An improved clamp was released which utilizes rivets to secure the T-bolt strap. This clamp has proven more durable in severe service applications.

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Exhaust Diffuser The exhaust diffuser is another aerodynamic device located in the turbine section of the turbo. The diffuser is basically an arrangement of 3 or 4 vanes (stationaryfins) which are placed directly behind the turbine blades. As the exhaust gas flows through the turbine blades, it next must enter the turbo’s exhaust duct. In order to direct this flow of gas from the blades smoothly into the duct, the diffuser vanes provide a smooth transition path for the gas to follow, thereby eliminating turbulence.

Exhaust Duct

Figure 7-16 Turbine Shroud Retainer, Exhaust D u d and Exhaust Difiser

The exhaust duct acts as the outlet for the engine’s exhaust gas after it has passed through the turbine blades. The duct “floats” to allow for thermal expansion and is mounted with bolted spring washers located along a mounting “foot” on each side where it rests on the main housing. The duct is sealed to the turbo by means of a half-lap joint and retainer ring on the compressor bearing support side and two spring-tensioned seal rings at the inlet scroll end. There are two basic exhaust ducts which are applied to the EMD turbo, The “standard” duct is attached to the turbo main housing by 3 spring washer sets on each mounting foot. This duct was used on most applications until the late 1970’s.The other basic duct, known as the “big-foot” duct, is two inches shorter than the standard duct, and is attached to the turbo by 5 spring washer sets on each mounting foot. This duct was designed for the application of an exhaust silencer atop the turbo duct, and is therefore made shorter and is heavily reinforced to support the added weight.

A built-in aspirator tube provision in both ducts allows for the installation of an “eductor tube”, which produces a suction that is applied to the engine crankcase for ventilation. As exhaust gas flows upward and out of the duct, a negative pressure is established behind the beveled end of the tube. The outboard, flanged end of the tube is connected tewarfidter which contains a screen called the lube oil separator. The suction applied above the screen in the separator draws vapors from the engine crankcase, while the screen prevents lube oil from being drawn out. Locomotive applications which utilize an exhaust silencer, as well as most marine and industrial applications, use an “ejector‘ arrangement. This system uses compressor discharge air directed through a venturi and combined with the eductor tube suction to aspirate the crankcases of these engines which have inhibited exhaust gas flow due to restrictions such as silencers or long runs of exhaust ductwork. 7-16

ElectroMotive Model 567.645 81710 Series Diesel Engines

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A drain opening is provided near the bottom of the duct to allow for the drainage of rdinwater which may enter the duct while the engine is shut-down. This drain hole location corresponds with a small tube that passes through the compressor bearing support from the impeller side. The drain hole is of a larger diameter than that of the tube. When the impeller is spinning, pressurized air is blown through the tube, and into the duct drain. This pressure, being greater than the exhaust gas pressure in the duct, effectively prohibits gas leakage through the drain. However, when the impeller is not in operation, no air pressure flows through the tube. In this case, the drain hole in the duct will allow any fluids which have collected in the exhaust duct to drain into the turbo main housing, which has a corresponding hole near the bottom for further drainage out of the entire turbo.

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COMPRESSOR DIFFUSER The compressor diffuser consists of a row of fins or (‘vanes’’which are attached to a mounting ring and positioned around the circumference of the impeller. The vanes direct the flow of compressed air which is discharged from the impeller and provide a smooth air delivery which is free of turbulence. The compressor diffusers are manufactured with specifically sized “throat passages” between the vanes. The size of these passages controls the air flow so that the compressor power requirements are balanced with the power generated in the turbine by the exhaust gas energy at full load. For this reason, the compressor diffuser throat area must be “matched” to the turbine nozzle ring area during turbo assembly.

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These throat passage sizes also correspond to the volume of air that the turbo supplies. For example, a turbo for a 16 cylinder engine contains a diffuser with larger throat passages than one designed for use on a 12 cylinder application.

Figure 7-18 Compressor Diffusers

Figure 7-19 Compressor Diffusers

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Electrdvlotive Model 567,645 81710 Series Diesel Engines

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PLANET GEARS

G The sun gear which is machined onto the end of the turbine wheel meshes with

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3 planet gears. These gears engage with the sun gear at 120 degrees intervals, and are

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located by a planetary gear carrier shaft. The carrier shaft is basically a disc, from the face of which extends 3 pins. Each pin passes through the center of a planet gear. O n the opposite side of this disc, the carrier shaft itself is splined.

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There are two basic planet gear designs: the original or “standard” 32 tooth gear and the “high-capacity” 47 tooth gear. It is a fact that all gears transmit a vibration as their teeth mesh. The level of vibration varies with such things as wear, roughness, and tooth profile. The original configuration planet gear set performed satisfactorily in the rail applications for which it was designed, but when EMD turbocharged engines began to see service in high gear-loading applications such as generating set installations, a more durable gear design was desired. Generating sets, for example, are subjected to constant high rpm regardless of the amount of load on the system. This constant speed is necessary in order to maintain the electrical “line frequency”. Such engines often run at less than full rated load. Consequently, exhaust gas energy levels are lower than normal, which means that the turbo gear drive must make-up for the less powerful exhaust. The end result of continued operation in this mode is accelerated planet gear wear. Worn planet gears can cause seriously increased gear vibration levels. The increased vibrations in the planet system cause the turbine wheel to vibrate. This vibratory input results in turbine blade fatigue fractures in worst-case situations, and rapid clutch wear in many cases. The solution to the problem is to reduce the vibration level generated by the gear mesh by increasing the tooth to distribute loading over a larger area. These “high-contact” or “high capacity” gears significantly reduced the light-load vibratory levels, and tooth wear was nearly eliminated under high gear train loading conditions. Usage of the high-capacity gear train has spread over the years from marine drilling applications only to marine propulsion, industrial generator sets, and rail engines as well. Turbos utilizing the standard gear design carry 18:l or 19.7:l gear ratio designations.Those which contain the high-capacity gears utilize ratios of 16.7,16.8,or 17.9:l. In any case the ratio designation refers to the speed differential between the turbocharger impeller and the engine crankshaft.

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RING GEAR AND CLUTCH HOUSING The third element in the planetary gear tralli is the ring gear. The ring gear surrounds the 3 planet gears, and is manufactured with internally cut teeth on the inside diameter. Consequently, each planet gear’s teeth are actually engaged to 2 gears simultaneously:

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the sun gear on the turbine wheel shaft the ring gear which surrounds them.

T h e ring gear is attached to a housing which encases the turbo clutch. The means of this attachment are bolts, so the ring gear is locked to the clutch housing. This clutch housing is located within the turbine bearing support (part of the doweling assembly), and rotates on the outside diameter or the clutch support (where the turbine bearing is located). Bronze thrust washers and bushings are used as bearing surfaces between the clutch support and the clutch housing.

Figure 7-20 Ring Gear and Clutch Housing

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CLUTCH CAMPLATE AND ROLLERS The overrunning clutch design allows rotation in one direction, and engagement or “lock-up” in the other. This is accomplished through the use of a center hub called the support, a set of cylindrical rollers, and a surrounding ring called the camplate, which utilizes a series of wedge-shaped pockets in which the rollers are located. The 12 pockets in the camplate are designed with an angled ramp in each. Thus, the distance from the outside diameter of the support to the ramp varies depending on where the measurement is taken. This pocket depth at one end of the ramp is greater than the diameter of the roller. However, at the opposite end of the ramp, the pocket depth is less than the roller’s diameter. Consequently, when the roller approaches this end, it becomes wedged between the support and the camplate ramp, locking the two parts.

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On the example below, note that if the camplate were rotated in a clockwise direction, the rollers would move into the large ends of the camplate ramps, allowing the camplate to rotate free of the support. However, if the camplate were turned counterclockwise, the rollers would travel to the small ends of the ramps and effectively lock the camplate to the stationary clutch support. The camplate is located in the clutch housing, on the end of which is also found the ring gear. The camplate is attached to the clutch housing by means of 6 “drive pins” or dowels. As a result, the camplate and ring gear operate as one unit, each one being attached to the clutch housing at opposite ends. Since the clutch support is stationary in’the turbo (being bolted to the turbine bearing support), when the camplate locks to the support, the clutch housing and ring gear also become locked.

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GEAR DRIVE SYSTEM The splined-end of the carrier shaft extends through the idler gear support, which is the plate at the back of the turbo. Two bearings are used to support the carrier shaft: 1) a ball bearing located in the idler gear support; and, 2) a roller bearing which is in the carrier bearing support.

O n the splines of the shaft, a carrier drive gear is mounted. This gear is actually externally mounted on the turbo, although most of it is obscured from view by the carrier bearing support. Located on a small stub-shaft attached to the idler gear support below the carrier gear is the turbo idler gear. The idler gear is engaged with the carrier drive gear at the top, and with the engine’s gear train at the bottom. The idler gear is mounted on a special, barrel-faced roller bearing. This bearing has a self-aligning feature due to the barrel-shaped rollers. As a result, the gear can actually be “wob bled” on its stubshaft if force is applied.

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: Carriar Shaft Spacer 2. Set Of 3 Matched Planet Gears 3. Planet Gear Shafts 4. Planet Gear Bearings 5. Carrier Shaft 6. Carrier Shaft Ball Bearin 7. Idler Gear #upport 8. Idler Geer

9. Idler Gear Roller Bearing 10. Idler Shaft 11. Carrier Drive Gear 12. Carrier Shaft Retainer Plate 13. Carrier Gear Roller Bearing 14. Lube Oil Jumper

Assepbly 16. Carrier Bearing Support

Figure 7-23 Gear Drive Section

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Electro-MotiveModel 567,645 & 710 Series Diesel Engines

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GEAR-DRIVE SYSTEM Right-Hand Drive Applications: Some marine propulsion applications of EMD engines employ two counterrotating engines. In such installations, a pair of engines, one left-hand rotating (standard) and one right-hand rotating share a common hull. Since the gear train of the right-hand rotation engine turns in the opposite direction from that of the standard engine, a special turbocharger is required. The turbo for use on these right-hand rotation engines utilizes two turbo idler gears rather than the single gear on more common models. In this way, even though the engine gears turn in the opposite rotation, the turbine wheel is driven in the same direction on all EMD turbochargers.

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LEFT HAND ROTATION GEAR TRAIN

RIGHT HAND ROTATION GEAR TRAIN

Figure 7-24 Gear Drive Systems

LUBE OIL SYSTEM The turbocharger’s lubrication system is actually an extension of the engine oil system. Following is a description of flow: 1. As oil travels through the main oil gallery in the crankcase towards the rear of the engine, it enters the stubshaft bracket assembly on the end sheet of the engine.

2. An oil passage or groove in this bracket directs the oil to an oil manifold which is also attached to the end-sheet. The oil flows through the manifold and is delivered to the turbo oil filter mounted on the engine. 3.

Oil flows through this filter, which carries the same rating as the filters in the main filter tank.

4. Provided the filter is not plugged, oil leaves the filter and flows back through the lower leg of the oil manifold. Note: If the filter is plugged, no oil will flow through the small oil pressure sensing line which connects the engine governor to the downstream side of the turbo filter. 5.

Oil flows through another grooved passage in the engine stubshaft bracket and is admitted to the upper idler stub.

ITS Locomotive Training Series - Student Text

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6. Oil flows through a passage in the center of the stubshaft into the 4inch bore in the turbo main housing.

7 . A vertical passage in the turbo main housing called the “main oil supply” directs the oil upwards.

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8. The main oil passage emits oil at the top for the clutch and planetary gears. A branch line from the main passage passes through the main housing carrying oil to the auxiliary generator drive and also intercon nects to the compressor and turbine bearing lines.

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SOAK-BACK SYSTEM Due to the fact that the turbo is dependent upon the engine main oil system, an additional lubrication system is required to protect the turbo during those periods when main oil system flow is unavailable.

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The main oil system is driven by a gear train connected to the crankshaft. Consequently, oil flow is present only when the crankshaft turns. During an engine shutdown, the crankshaft continues to turn for 5-10 seconds after the shutdown is triggered. However, due to the high speed at which the turbine wheel operates, the momentum of the mass causes the turbine to “run down” for periods as long as 3540 seconds. Consequently, no lubrication is provided to the turbo’s bearings by the main oil system during this time.

As a result, an electrically-driven oil pump called the “soakback Pump’’ is mounted on the engine to provide lubrication to the turbo during this rundown period. As the engine shutdown cycle occurs, the pump is energized and begins to supply the turbo with oil. After the engine stops, the soak-back pump continues to . heat operate for 30-35 minutes. During this time, the flow of lube oil is used to carry from the turbo’s seals and bearings(hence the name “soakback"). The soakback pump is also energized during the engine start sequence. In this instance, the bearings in the turbo are supplied with oil even before the oil flow from the main system can reach them. In this way the soakback pump serves to prelubricate the bearings.

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EiectroMotive Model 567,645 & 710 Series Diesel Engines

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Figure 7-25 Turbo Lube Oil System

PLANETARY SYSTEM OIL DRAINAGE SCREEN Lube oil drainage from the planetary system of the turbo passes through openings in the idler gear support. In the event of a planetary system failure, metal fragments and broken gear teeth may be carried-off with oil drainage. To prevent these metal fragments from entering the engine oil sump or passing through the diesel engine's rear gear train, a screen is installed in the idler gear support. The original screen was located in a small triangular-shaped opening in the idler gear support. Most planetary system drain oil flows through this area. However, turbos which are equipped with the highcapacity type planet gears have a higher oil flow rate which requires an increased oil drainage provision. The idler gear support on such turbos utilizes three slotted passages on the face of the support in addition to the triangular opening. Drain oil flows through all four of these passages. Consequently, it is necessary to provide increased protection in the way of a larger screen.

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In the mid-l980's, an improved screen was released for retrofit in the high-capacity turbos. The screen is installed on the inboard side of the idler gear support, and oil must pass through it as it flows through any of the four possible drainage paths. Turbos so-equipped do not utilize the previous triangular screen.

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GEAR TRAIN OPERATION The EMD turbocharger utilizes a geardrive system which takes energy from the engine’s crankshaft and transmits it to the turbine wheel at the sun gear. This planetary gear drive system is used when exhaust gas energy levels are not sufficient to drive the turbine wheel, such as during engine starting and low speedflight load periods of operation. Dependency on the gear drive system decreases as exhaust energy levels increase, until eventually no mechanical assist is required. It is the function of the overrunning clutch to “disengage”the gear drive. This is accomplished by allowing the rotating assembly to overspeed the driving gear train while the gears remain engaged. This power take-off originates at the upper idler gear in the engine’s camshaft drive gear train. This upper idler gear is equipped with a shock damping device which uses packs of coil springs to absorb torsion shocks in the engine’s gear train. Attached to this damping device is a turbo drive gear. The turbo drive gear, which serves as the power take-off for the turbo’s gear train, is isolated from the inherent engine torsional vibrations which can be detrimental to the turbo’s longevity. Figure 7-26 Spring Drive Gear The next gear in the turbo gear train is mounted on the “rear” of the turbo at the idler gear support. This gear is appr0priate.j named the turbo idler gear. The idler gear drives a turbo-mounted carrier shaft drive gear. This gear is located on the end of the planetary gear carrier shaft. The carrier shaft extends through the rear “bulkhead” of the turbo and carries the 3 planetary gears.

The planet gears are engaged to both the sun gear on the end of the turbine wheel, and to a ring gear. The 3 planet gears surround the central sun gear, Obeing meshed with the sun at 120 degree intervals. These planet gears are also surrounded by a ring gear. The ring gear is manufactured with internal teeth, so that a “track” is formed on which the 3 planet gears can travel. The ring gear is attached to the clutch camplate, and the two components operate together as one. If the camplate rotates, so does the ring gear. Conversely, if the camplate is locked, the ring gear cannot move. .

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To understand how the engine gear train drives the turbine wheel, a simulated engine start-up sequence follows:

1. As the starter motor pinions engage the flywheel, the crankshaft is rotated

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Electro-MotiveModel 567,645 & 710 Serbs Diesel Engines

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2. The lower idler gear in the camshaft gear train is turned by the force transmitted from the gear teeth on the crank gear to those on the lower idler.

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3. The lower idler gear teeth transmit force to the upper idler gear teeth which they engage with, turning the upper idlerhpring-drive gear ass embly.

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The turbo drive gear (on the spring-drive gear) assembly transmits force to the teeth of the turbo idler gear.

5 . The turbo idler gear teeth turn the carrier shaft drive gear.

6. The carrier drive gear turns the entire carrier shaft assembly. 7 . The 3 planet gears located in the rotating carrier shaft pass the torque on to both the sun gear and the ring gear.

8. The torque input to the ring gear turns it (and the clutch housing) in the opposite direction. However, after a very short travel the camplate locks to the clutch support due to the rollers which have become wedged in the ramps. 9. With the ring gear held stationary, gear train torque is transmitted through the planet gears to the sun gear. This causes the sun gear to drive the turbine wheel (in a counterclockwise direction as viewed from the impeller). Due to the speed-increasing nature of a planetary gear system, the sun gear’s rotational speed is significantly higher than that of the carrier shaft assembly which drives it.

10. As the impeller is rotated, air drawn through the engine filters increases in velocity while passing through the compressor di&ser and air scroll with a minimum of turbulence. The size of the passages in the compres sor d i h s e r controls the air flow so that the compressor power require ments are balanced with the power generated in the turbine by exhaust gas energy at full rated load. (It is for this reason that the compressor diffuser throat area must be “matched” to the turbine nozzle area when the turbo is assembled.)’

11. As air is pumped into the engine, the combustion process begins. As the engine runs, the exhaust gases from the individual cylinders are directed through the turbine section of the turbocharger. The energy extracted from these gases is applied to the turbine blades, and this force aids the engine gear train in turning the rotating assembly.

12. Two sources of torque are fed into the planetary gear system. The torque developed by the turbine is fed through the sun gear, and the torque transmitted by the gear train is fed through the carrier shaft to the planet gears. Thus, the torque transmitted to the ring gear is the difference between the levels of the two torque inputs. ITS Locomotive Training Series - Student Text

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13. When the turbine does not develop sufficient power to turn the rotor at the enginedetermined driving speed, the torque input through the planet gears continues to hold the ring gear and camplate in the “locked”direction as previously described. However, when the power developed in the turbine is capable of driving the rotor faster than the speed dictated by the turbo gear ratio, the increased torque from the sun gear is fed through the planet gears to rotate the ring gear and camplate in the “unlocked”direction. The clutch housing now rotates around the clutch support at a speed and turbine wheel RPM.During this overrunning condition, the clutch rollers are in the wide end of the wedge-shaped pockets formed by the camplate ramps.

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14. The turbo continues to operate in this “free-wheeling” state so long as the exhaust gas energy level and flow rate are sufficient to provide enough power to drive the rotating assembly faster than the gear train would. However, if the engine speed or load is reduced, the amount of energy in the exhaust decreases, and the turbine speed begins to drop. When the turbine speed returns to that of the gear train, the clutch reengages and the gear train once again provides a portion of the energy requirement to drive the rotating assembly.

TURBOCHARGERS WITH EXTERNAL CLUTCH All 567-T and most 645-E/F turbos utilize the internally located 12 roller clutch design as discussed. However, in the early 1980’s an experimental “external clutch” was field tested in selected applications where loads on the conventional clutch were severe. These tests were conducted with 645 turbos primarily in marine towing service. The external clutch became “basic” or standard equipment with the 710-G engine. This design removes the clutch from within the turbo and places it in the engine camshaft drive gear train instead. The spring-drive gear assembly found in the previous 6 4 5 series is replaced with a new double gear assembly which is interconnected by means of a large version of the roller clutch configuration. The clutch utilizes 16 three-quarter inch diameter rollers in place of the 12 one-half inch diameter rollers found in the internal clutch. The new rollers are one and one-half inches long, whereby the 12 roller clutch used one inch long rollers. Correspondingly, the camplate diameter of the external clutch is approximately 11.750” compared to the 7.750” of the previous type. Also, the camplate roller pockets are inverted, or open towards the outside diameter rather than toward the center of the p+$ q OE previous versions. The increased size of these components, coupled with the more numerous rollers, has improved the load-carrying characteristics of the roller clutch tremendously.

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ElectrMotive Model 567,645 & 710 Series Diesel Engines

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The principle of operation is exactly the same as that of the internal clutch. However, since the clutch disengagement takes place in the engine gear train, the turbo’s planetary ring gear is now “locked” in a stationary position. This lock-up device occupies the space where the roller clutch had been on previous turbo models. The clutch support has been modified from its original configuration with the addition of a row of gear teeth. The outside diameter of these teeth is the same as that of the three planet gears in the carrier shaft assembly. The ring gear is now much longer than its predecessor, with two rows of identical teeth cut on the inside diameter. This new ring gear bears a resemblance to a sleeve such as is used to synchronize gears in automobile transmissions. The clutch support teeth enter the ring gear at one end, and the planet gears from the other. Since the clutch support is fixed in place, its tooth engagement with the ring gear prevents rotation of the ring gear. Although not a common practice, the external clutch can be applied to 645 type turbos equipped with high-capacity planetary systems.

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Figure 7-27 External Clutch

ITS Locomotive Training Series - Student Text

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EXTERNAL INSPECTION AND OPERATIONAL PROBLEM DIAGNOSIS Over the past several years, many items have been written and discussed regarding how to qualify an EMD turbocharger for continued service when a problem has been reported. Many of these techniques have been passed on verbally, while others were written procedures foun‘d in Engine Manuals, Troubleshooting Guides, or various written correspondence. In some cases, these procedures have become obsolete or in need of revision due to the evolution of the turbo, as well as a broader base of practical experience from which to draw on. The following pages are offered to assist EMD customers in troubleshooting and requalifying their turbos.

CHECKS WHICH CAN BE MADE WHILE THE TURBO IS STILL ON THE ENGINE

A.

ROLLER CLUTCH TEST

1.

Idle engine until normal operating temperature is reached. (If engine cannot be started, remove rubber boot from turbo inlet and verify that the impeller locksup when attempting to turn in a clockwise direction by hand. If this does not occur, either the clutch has completely failed or a planetary gear train failure has occurred. Refer to paragraph Additional External Inspections.)

2.

With engine warmed-up, push injector control linkage lever inward, increasing engine speed to approximately 700 RPM.

3.

Pull injector control linkage lever out completely to “No Fuel” position, overriding the engine governor. (At this time, the clutch will disengage, allowing the turbine to spin free of the gear drive.)

4.

As the engine begins to stall, push the injector linkage lever in once again, providing more fuel, which should increase engine speed. The decelerating turbine wheel will “meet” the accelerating eqgine gear train and the roller clutch should engage, providing sufficient air for continued engine speed increase.

If the clutch fails to engage, the injector rack linkage will move toward “full fuel” position, black smoke will emit from the exhaust duct due to a lack of air, and the engine may stall. These symptoms indicate an imminent clutch failure, consequently the turbocharger should be replaced. Turbocharger roller-type clutches tend to h i €gradually rather than suddenly.

This characteristic refers to the fact that in early stages of clutch wear-out, the slippage may be intermittent. In such instances, the engine may smoke heavily or stall during speed changes, yet behave normally later. T o ensure that the clutch is not in this early stage of failure, the aforementioned test procedure may be repeated a few times. However, articles stating that as many as 30 consecutive tests may be required are in error.

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ElectroMotive Model 567, 645 & 710 Series Diesel Engines

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To avoid damaging a good clutch, injector linkage manipulation should not be performed more than 2 or 3 times to qualify a clutch. If the clutch is in fact defective, the turbo should exhibit the reference symptoms within this number of trials.

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Since 1976, virtually all regular production 567 and 645 EMD turbos have been built with a roller-type clutch. Prior to that date, some turbos had utilized a ratchet-type clutch/friction drive gear configuration which required a special requalification procedure using a torque wrench. Under no circumstances should a wrench be applied to the compressor impeller nut to determine roller clutch condition. A test of the older design friction drive gear called for the application of a torque wrench to the impeller nut. The observed “break-away torque” provided an indication of the condition of the friction drive gear, but no conclusion could be drawn as to the turbocharger clutch condition from this test. Furthermore, this test was valid only on turbos equipped with the previous “ratchet” clutch. Engines equipped with roller clutch turbos should not be subjected to this procedure.

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TURBOCHARGER OIL PRESSURE TEST

In some instances, it may be prudent to confirm that the main engine and soi--back oil systems are actually delivering lube oil to the turbo. This test would -e recommended after the installation of a turbo which was not run in a test cell after assembly by the remanufacturer, or upon installation of a replacement turbo after a “bearing failure” had occurred. Turbocharger bearing failures are usually a result of an external condition such as an imbalance of the rotating assembly (due to foreign object damage) or to a lack of proper lubrication. Therefore, when an impeller is observed to be rubbing the inside of the air inlet portion of the turbo and no damage is observed on the turbine blades, it is wise to confirm the flow of lube oil through the new turbo prior to returning the engine to service. 1.

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Locate and remove the compressor bearing oil passage pipe plug on the right bank side of the engine turbocharger. This plug is installed in the compressor bearing support, which is the 3” thick casting between the main housing and the air scroll. The 1/2” PT lug accepts a 3/8” male square drive such as that of an ordinary ratchet wrench. The plug will be found above the right-bank turbo air scroll to aftercooler duct mounting flange.

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Temporarily install an oil pressure gauge in the oil passage. Operate the soak-back pump while observing the oil pressure gauge. The gauge should indicate the presence of oil pressure, typically in the 15-30 PSI range. (At the same time, check to make sure that no oil is observed flowing from the engine camshaft bearings - this condition would indicate that the check valve in the turbo filter assembly is defective.) If not oil pressure is observed at the turbo, do not start the engine until the cause is determined.

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Standing adjacent to the flywheel for viewing, energize a stopwatch at the moment when the crankshaft is observed to stop rotating.

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Listen carefully for the compressor impeller to stop rotating (identified by the cessation of a whirring sound). Stop the timer immediately.

8.

Due to the momentum of the rotating assembly, the elapsed time should not fall below 27 seconds. Actual run-down times will vary, depending upon the speed of the rotating assembly at the time of shut-down. However, a time of less than 27 seconds from full-speed/full-load indicates that a condition exists which inhibits the rotor from turning freely.

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ADDITIONAL TURBOCHARGER EXTERNAL INSPECTIONS

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It is fact that 60-75 percent of all “turbocharger failures” are caused from an external source such as foreign object damage, overheat/overspeed, lack of proper lubrication, etc. Consequently, unless the damaged turbo undergoes a thorough diagnosis, the condition that existed within the engine which actually caused the failure cannot be determined. Likewise, unless this undesirable condition is corrected, repetitive “turbo failures” can and will occur. The following information is provided in order to help properly identify the true cause of a “turbocharger failure”. The key to the proper diagnosis of turbo problems is to perform ALL the inspections rather than to stop when one condition is observed. In many cases, several symptoms will be present, and all must be reviewed to fully understand what occurred. There are 4 external inspection areas:

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2. Exhaust Outlet Inspection

3. Exhaust Inlet Inspection

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1. Air Inlet & Impeller Inspection

4. External Gears and Oil Drainage Screen Inspection

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Figure 7-28 External lnspection Areas

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AIR INLET AND IMPELLER INSPECTION (Remove Air Inlet Boot to View)

Inspect for the following conditions: a.

Broken Impeller Blades: Indicate possible foreign object damage, or metal fatigue.

b.

Nicked Leading Edges on Impeller Blades: Indicates foreign object passage through air stream. Check air filter box, air duct, and replace air filters.

C.

Blade Rub on Inside of Cast Iron Impeller Cover: Indicates loss of support of turbine wheel in the form of a compressor, turbine, or thrust bearing failure. However, the cause of the bearing failure must also be determined. Continue with the inspections. NOTE: Always replace air filters and check aftercooler cores, aftercooler ducts, and air box for aluminum debris.

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Impeller Locks-Up When Rotated Clockwise: Turning the impeller by hand in a counter-clockwise direction should result in a freewheeling condition. When turned clockwise, the impeller should “lock-up”.If the impeller free-wheels in both directions, either the clutch has failed completely, or a planetary system failure has occurred. If the impeller cannot be turned in either direction, the rotor is locked-up, and the inspection should continue.

EXHAUST OUTLET INSPECTION: (View Down the Exhaust Duct of the Turbo)

Inspect for the following conditions: a.

Warped Exhaust Diffuser: Exhaust diffuser vanes will appear to be “wavy” when viewed from above if the turbo has been subjected to an “Overheat-Overspeed” condition. The thermal expansion which occurs at escalated temperatures causes the part to “grow”. The diffuser is secured in position within the turbo by a series of metal rods. If it becomes overheated, this expansion forces the thin metal vanes to distort permanently. A warped diffuser is always an indication of excessive engine exhaust gas temperatures.

When a condition exists within an engine that results in excessive exhaust heat energy, the high heat level causes the turbine to spin faster than normal. Consequently, the name “Ov&eet-Wetspeed” is associated with this phenomenon. As the turbine spins faster, the blades begin to soften and stretch, and may eventually bred. Also, the impeller tries to pull the turbine wheel forward, out through the air inlet. This overloads the thrust bearing and usually causes it to fail as well.

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Electrdvlotive Model 567.645 & 710 Series Diesel Engines

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Typical causes of excessive heat energy are:

G 1. Broken Piston Rings 2. Worn Injector Tips 3. Broken Exhaust Valves 4. Improperly Timed Fuel Injectors 5 . Incorrect Valve Timing 6. Plugged Aftercooler Cores 7 . Plugged Engine Air Filters

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Any of these conditions can provoke either an “Air Box Fire” or an “Exhaust Manifold Fire”. Evidence of such fires will be found in the form of gray colored ash at localized areas where the fire occurred. Thus, it is necessary to inspect the air box and the exhaust manifold with a bright lamp whenever an Overheatloverspeed failure claims a turbo. Unless the condition is detected and corrected, it will continue to damage replacement turbos.

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Air boxes should be cleaned whenever a thick, wet, sponge-like soot deposit accumulates to depths approximating l/2”. The cause of the deposit formation must be found and corrected.

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Bulged or Punctured Turbine Shroud: The turbine wheel blades are surrounded by a band or shroud. The clearance between this shroud and the blade tips is quite small. Consequently, in the event that an Overheatloverspeed occurs, any plates which stretch will likely contact the shroud and deform or bulge it. In cases of blade breakage, the shroud may become punctured.

C.

Broken Shroud Retainer Clamp: A narrow clamping ring is used to secure the shroud in most turbos. In some cases, this clamp may break due to metal fatigue. If this is observed, the turbo must be removed immediately. If the shroud drops from its pilot, it will damage the turbine blades.

d.

Oil Out of the Exhaust Stack: The seals in the turbo require air to function properly. If the Engine Air Filters are restrictive, the turbo seals may be starved for sufficient air. Check the filter pressuredrop prior to changing the turbo. Also, the source of the oil may be within the engine itself. Before changing the turbo, remove the exhaust screen and check the turbine inlet for wet, shiny deposits, which indicate the oil is coming from the engine, not the turbo.

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EXHAUST INLET INSPECTION:

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Wet, Oily Deposits: The inlet should appear to be dry, with a light amount of flat-black, sooty coloring. If wet, shiny deposits are observed, the engine prob ably has an oil control problem, and an exhaust manifold or air box fire may occur at any time. Bent or Plugged Nozzle Ring Passages: Using a bright lamp, view into the turbine exhaust inlet. The nozzle ring, which is a series of stationary vanes, will be observed. Exhaust gas must flow through this ring in order to act upon the blades in the rotating assembly. If the nozzle is dented and bent, it is generally an indication of foreign object passage. Also, deposits formed on the openings indicate an engine problem such as a cooling water leak. Deposits can also form due to the type of fuel used. In any case, the restriction to gas flow imposed by dented or plugged nozzles can cause the turbo to surge or “burp” at higher engine speeds. This is an undesirable condition. Nicked or Broken Turbine Blades: The blades around the rim of the turbine wheel cause the rotating assembly to spin whenever exhaust gas flows through them. If they are nicked, foreign material has passed through with the gas. This material is generally in the form of small, sharp pieces of broken piston rings or exhaust valves. The nicked blades in the turbine wheel unbalance the highspeed rotating assembly, and a compressor or turbine bearing failure will generally occur if the turbo is permitted to remain in operation. In some cases, the blades may break due to: a severe impact; stretching as a result of an overheat/ overspeed; or metal fatigue. In such instances, the rotor unbalance is tremendous and a severe bearing failure is imminent.

EXTERNAL GEARS AND OIL DRAINAGE SCREEN INSPECTION: (Required Turbo Removal)

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Damaged Turbo Idler or Carrier Drive Gears: Damage to the externally mounted gears on the back-side of the turbo is generally an indication of an engine gear train problem rather than a turbo malfunction. In extreme cases, one of these gears may exhibit broken teeth if the turbo rotating assembly is seized. Metallic Debris in Oil Drainage Screen: Located just below the turbo-mounted idler gear is a small triangular-shaped screen*. All lubricating oil from the planetary gear train passes through this screen as it drains from the turbo. Hence, if a planetary gear train component is h k c n , the oil drainage will carry this debris with it, and will deposit the chips against the inside of the screen.

* The triangular screen was replaced with a larger, internal screen in 1988.

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ADDITIONAL TROUBLESHOOTING INFORMATION

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Check engine air filters for plugging. A lack of air to the turbo’s labyrinth seals will cause oil migration across the seals, especially at higher speeds.

2.

Remove eductor tube and inspect lube oil separator assembly. Check for damaged or missing screen, which would allow oil to be drawn out with crankcase vapors.

3.

Remove the expansion joint between the turbo exhaust inlet and the exhaust screen assembly. Inspect the turbine inlet scroll. If coated with wet, shiny oil, the source of the oil out of the stack is within the engine. Inspect the engine in accordance with the Maintenance Manual to determine the source of the oil in the exhaust gas.

4.

If the turbine inlet is dry, the turbo may have a true seal problem. Since

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labyrinth seals are non-wearing components, they have either plugged due to dirt or have become physically damaged from contact with the rotor as a result of a bearing failure. At this point, the turbo must be removed.

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Exhaust Leaks 1.

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Exhaust leaks usually occur at the expansion joints between the exhaust manifold sections or at the connection to the turbine inlet scroll. These leaks are dangerous to operating personnel, and detract from the turbo’s efficiency.

If a crack is found in the turbine inlet scroll, no repair in-place will be successful. The turbo must be removed.

Noise Identical turbos can make varied sounds due to manufacturing tolerances and operating characteristics. Generally, noise should not be a factor when determining a turbo’s condition. Exceptions would be loud screeching noise or severe humming accompanied by vibration. Turbos commonly emit “chirping” noises, particularly at low speeds such as idle. Also, it is common to hear a “chirp” in varying cadence when releasing the injector control lever from higher engine speeds. This noise is simply the turbine coming back onto the gear train.

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Burping and Smoking This symptom indicates a reversal of the normal exhaust gas flow through the engine and turbocharger. There is typically an approximate 2 psi drop across the engine power assemblies. This means that air box pressure is 2 psi greater than exhaust manifold pressure throughout the speed range. If this condition changes, whereby exhaust pressure exceeds air box pressure (momentarily), a surge or burp will occur. This relieves the excess pressure through the turbo air inlet, and engine operation may return to normal until the back-pressure builds once against. A surging condition is detrimental to the turbo. First, the hot exhaust gas reversal into the engine air box may ignite any combustible deposits in the air box, causing an air box fire and resultant turbo overheat/overspeed. Second, the load imposed upon the clutch and planetary gear drive system is significant.

When surging occurs, the following procedure should help in determining the cause:

1. Locate another engine of the same type and model; i.e., 16-645E3B. 2. Install a 0-30 psi pressure gauge on a modified handhole cover of each engine. 3. Run each engine at full-speed, no load and record pressure reading.

4. Since each engine was operating on the gear train (due to no load), each turbo was operating as a geardriven blower. Pressure variation should be no more than 1 psi between the two engines.

High Air Box Pressure on Suspect Engine:

1. Check turbine exhaust inlet screen for plugging.

2. Inspect turbine nozzles for plugging and turbine blades or damage. 3. Check cylinder liner inlet ports for plugging.

4. Check valve timing (late?). Low air Box Pressure on Suspect Engine:

1. Check engine air filters for restriction or plugging (max. 13.5” H,O).

2. Check aftercooler cores with manometer for plugging (max. 10’’ H,O). 3. Inspect for air box leak.

4. Test turbocharger for slipping clutch.

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Electro-ivlotive Model 567.645 & 710 Series Diesel Engines

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OVERHEAT/OVERSPEED FAILURE An overheatloverspeed failure is an overspeeding of the turbine wheel which is caused by excessive (overheated) exhaust gas temperature. Exhaust gas temperature will vary with ambient weather conditions, fuel characteristics, engine load, etc. However, normal temperatures generally range from 850 to 1050 degrees F at full speed, full load.

An overheatloverspeed is typically the most destructive type of failure which can occur to a turbocharger. It is caused by conditions external to the turbo such as worn power assemblies and dirty air boxes. Consequently, if the cause is not determined, the replacement turbo will also incur a similar failure.

Normally, a turbine wheel’s speed increases at approximately 450-500 rpm per second during a throttle “wipe”. However, during an overheatloverspeed, it is not unheard of to observe turbine speed increases of 5000 rpm per second. This can be accompanied by dramatic air box pressure increases of as much as 10 psi quite abruptly. If the overspeed occurs while the turbo is operating near its peak rpm (usually 18,500 to 21,500), within one second the speed of the turbine can exceed its safe limits and severe damage will occur. It is impossible to counteract for this condition quickly enough with the technology available today. Therefore, the only way to control overheatloverspeed failures is through preventative maintenance. Typical symptoms of an overheatloverspeed failure are a warped or deformed exhaust diffuser (resulting from excessive temperature) and stretched or elongated turbine blades (due to a combination of softening from excessive heat and lengthening due to centrifugal forces).

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Stretched Blade

Warped Exhaust Diffuser

Figure 7-29 Typical OverheatlOverspeed Conditions

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ITS Locomotive Training Series -.StudentText

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Any of the following conditions, which increase air box temperature, are contributors to overheat/overspeedfailures:

1.

Dirty Aftercoolers 2. Broken Compression Rings 3. Late Injector Timing 4. Incorrect Valve Timing 5. Plugged Exhaust Screen 6. Plugged Engine Air Filter 7 . Damaged Injector Tips 8. Exhaust Manifold Fire

FOREIGN MATERIAL DAMAGE TO TURBINE The mechanical break-up of any part of a power assembly or exhaust system component can result in foreign material damage to the turbine nozzle ring and turbine wheel blades. Common sources of foreign material are broken compression rings resulting from too much side clearance and fragments of an exhaust valve head which is disintegrating due to improper lash or excessive temperature. The turbocharger is reasonably protected from this material by the exhaust screen. However, since the screen must flow a large volume of gas with a minimal restriction, small objects can pass through. Also, larger sharp objects can eventually tear the screen grid and pass through to the turbo. Consequently, the exhaust screen should be periodically removed, cleaned and inspected. Any time that an indication of foreign object damage is observed, the source must be identified and corrected to prevent turbocharger failure. Due to the high rotational speed of the turbine wheel, small nicks near the outside diameter on the turbine blades cause serious unbalance of the rotating assembly, This unbalance is very detrimental to the turbo bearings, and will bring about their failure. Consequently it is recommended that whenever foreign material damage is observed in the turbine section, the turbo should be removed prior to running it to destruction and thereby increasing its repair cost.

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Typical Foreign Material Damage

Figure 7-30 Nicked Blade and Nicked Nozzle Ring

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ElectroMotive Model 567. 645 & 710 Series Diesel Engines

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FOREIGN MATERIAL DAMAGE TO COMPRESSOR IMPELLER Since the air inlet of the turbocharger is protected by a highly effective air filter, this type of damage should not be common. On the contrary, a surprising number of turbochargers fail due to this condition. Damage such as nicks to the leading edges of the compressor impeller blades result in the same serious unbalance condition and consequences as that of nicked turbine blades.

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Figure 7-3 1 Nicked lmpeller Blades

This type of failure is usually a result of one of the following:

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1.

Previous turbocharger failure, whereby broken pieces -.Jm the previous compressor impeller were driven into the air filter of filter housing and not removed.

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2.

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Misapplication of the compressor inlet boot or clamp. The clamp must be tightened squarely on the inlet or it may vibrate loose and enter the turbo.

CLUTCH FAILURE

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The clutch is one of the few areas of the turbo where there can actually be metal to metal contact during operation. Thus, it is a wearing item. EMD’s current recommendation is to replace the turbo to prevent clutch failure every 4 years or 24,000 hours of operation.

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Clutch life can become adversely affected if the turbo is subjected to:

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2. 3. 4.

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1.

Abnormal vibration levels due to rotor imbalance. Worn planetary gears. Frequent abnormal cycling such as from surging. Contaminated lubricating oil.

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ITS Locomotive Training Series -Student Text

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3 3

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Roller “Skid“ Mark

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Worn Ramp

Polished Ramp

(Grooved)

(Shiny-No Groove)

Figure 7-32 Camplate Ramp Wear

LACK OF PROPER LUBRICATION This mode of failure may occur due to a malfunction in the lubrication system such as a failed soakback pump, failed lube oil pump, blockage in a lubricating passage, or contaminatedhnacceptable oil. Other possible contributors include interruption of the soakback oiling prior to the completion of its timed cycle, and excessive engine rpm immediately following start-up. It is possible to “wipe”a bearing during engine start-up unless the injector control linkage is manually controlled to avoid great speed increases, particularly during cold ambient weather conditions. In the case of a lack of lubrication failure, most if not all, of the six bearings in the turbo may exhibit distress such as smearing to varying degrees. Since the compressor thrust bearing is typically the most heavily loaded surface in the turbo, the amount of damage sustained there is usually greater than that of other areas such as planet bearing surfaces. Since the turbo relies on the engine for its lubrication, this is yet another mode whereby the root cause of one failure must be corrected prior to the installation of a replacement turbo. Also, upon the installation of the replacement, it is good practice to confirm that oil pressure is actually reaching the turbo by carrying out the Turbocharger Oil Pressure Test. Oil pressure must be observed during soakback pump operation prior to engine start-up, or the replacement turbo will fail.

BEARING FAILURES Turbocharger bearing failures rarely occur without an external ontributin input. These inputs generally are rotor unbalance due to foreign material damage, over1 at/ overspeed, or lack of proper lubrication. Consequently, the failed turbo must undergo a thorough inspection in order to identif) all of the related failure modes. Once this has been accomplished, the sequence of events leading up to the failure can be reconstructed in order to arrive at the root cause of the bearing failure. Misapplied aftercooler ducts can also cause bearing failures through distortion of the doweling assembly. 7-42

Electro-MothteModel 567, 645 & 710 Series Diesel Engines

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For example, if the impeller has rubbed the cover, obviously a bearing failure has occurred. However, further inspection may reveal nicked turbine or impeller blades, which are caused by foreign object passage and lead to rotor unbalance. Therefore, the conclusion should be that foreign material struck the rotor, causing a vibration. This unchecked turbo operation in a vibrating condition resulted in the breakdown of the oil film on the bearing surface, and a smear on the bearing took place. The smeared bearing eventually progressed to a loss of support for the turbine wheel, and the impeller rubbed the inside of its cover. Unless the cause of the foreign material is identified and corrected, the replacement turbo is likely to fail in an identical manner.

Smeared

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Figure 7-33 Smeared Bearing

In some cases, it may be possible to determine which bearing has failed or has suffered the most severe distress by means of an external inspection. The key to this identification lies in the location of the heaviest concentration of aluminum particles on the inside of the impeller cover. In each case, each of the impeller blades will be rubbed at their edges, representing 360 degrees of damage to the impeller. However, the impeller cover can provide clues concerning the major bearing distress.

If the aluminum particles are evenly distributed 360 degrees around the inside of the cover, it is safe to assume that the thrust bearing failed, and the rotor moved forward. If the aluminum is primarily located in the bottom or 6:OO position of the cover, the compressor bearing has failed and that end of the rotor has dropped. Conversely, if the aluminum concentration is primarily at the top or 12:OO position, the turbine bearing has likely failed and allowed the sun gear end of the rotor to drop, raising the impeller end. In any event, the diagnosis must continue so as to determine what condition brought on the bearing failure in the first place. ,,, 8

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ITS Locomotive Training Series -Student Text

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PLANETARY GEAR TRAIN FAILURE The planetary gear train is another area where damage without external input is rather unusual. Although the gears are considered wearing parts, their design is such that they should not wear out within the prescribed turbo service life. However, vibration and heavy loading for long periods are detrimental to long gear life.

If the engine operates for long periods at light-load, the demand on the planetary system is dramatically increased and rapid gear wear can result. Once this gear wear becomes excessive, the mesh of the gears becomes “loose” and initiates a high frequency vibration. The existence of this condition is confirmed at the time of turbo disassembly, since the planet bearings will exhibit erosion of the silver plating at the end of the oil ramps. Oscillation of the sun gear within the planetary system can also produce a similar erosion of the turbine bearing. Furthermore, the planet gears themselves may actually strip, causing a complete loss of drive for the turbine. In such cases, the initial symptoms would parallel those of a clutch failure. However, upon removal of the turbo from the engine, metal debris would be visible in the turbo oil drain screen and possibly even on the “ledge” of the turbo main housing near the spring drive gear.

Figure 7-34 Broken Planet Gears Erosion

Erosion

I

Noraal Planet Bearing

Eroded Planet Bearing

Eroded Turbine Bearing

Figure 7-35 Eroded Bearing Conditions

. .. 4

In extreme cases, the vibration of the planetary system can lead to turbine blade fatigue. This condition involves the breakage of one or more turbine blades at a high stress location through simple metal fatigue. In the event of a planetary failure, the engine oil pan, oil strainers, and the oil itself should be checked for the presence of debris. Also, the oil filters should be changed. The external turbo gears, as well as those in the engine camshaft drive gear train, should be inspected for damage. The bolt torque on the spring drive gear should also be verified, since the shock loading brought on by such failures can sometimes break these fasteners.

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7-44

ElectroMotive Model 567, 645 & 710 Series Diesel Engines

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TURBINE BLADE FATIGUE Turbine blades may break off the rotating assembly through metal fatigue. Although rather uncommon, once this has occurred, the damage to the entire turbo is considerable. This is due to the extreme unbalance condition which results when so much mass it removed from one side of the wheel near its outside diameter. In many cases, the rotating assembly shaft will actually bend just ahead of the compressor journal, swinging the impeller out towards the “light” side of the wheel. Turbine blade fatigue can occur as a result of a high frequency vibratory input from a poor planetary gear system mesh. It also can result from a manufacturing defect of the blade itself. Generally speaking, manufacturing related problems tend to cause fractures early in the life of the machine, while gear mesh problems may occur after a considerable length of service has been reached.

Figure 7-36 Blade Fatigue Fracture

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Key Components in Evaluating a Turbocharger Failure:

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1. Turbine Blades 2. Impeller and Cover 3. Exhaust Diffuser

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4. Turbine Shroud 5. Nozzle Ring 6. Planet Gear Train 7. Bearings

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Turbocharger failures have been classified into a group of distinct types or “modes”. Each failure’mode has specific characteristics and is known by the areas of distress which are exhibited. The following list contains the most common failure modes, and a brief description of the areas of distress which can be used for root cause determination.

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OVERHEAT/OVERSPEED

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1.

Exhaust diffuser distorted or “warped” indicating severe thermal distress.

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Turbine shroud bulged and deformed from elongation of turbine blades.

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ITS Locomotive Training Series Student Text

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3.

Rotating assembly “frozen” (unable to turn) due to elongated turbine blades. Blades soften at excessive temperature, and stretch due to centrifugal force until they either contact the shroud or simply separate in the center of the airfoil portion.

4.

Presence of grayish-colored ash deposits within the engine air box or exhaust manifold. The greatest concentration of this ash will indicate the location of the fire’s origin.

5.

Blistered paint on air box handhole covers.

6.

Subsequent damage frequently associated with overheat/overspeed: a. b. c. d. e.

Bearing Failure (thrust, compressor, or turbine) Impeller Rub Clutch Failure Planet Gear Train Damage Labyrinth Seal Damage

FOREIGN MATERIAL D A M A G E T O TURBINE SECTIONS 1.

Nozzle ring nicked, dented or bent on front or back.

2.

Turbine blades nicked or torn on leading edges. \

3.

Subsequent damage frequently associated with €oreign material: a. b. c. d.

Bearing Failure Labyrinth Seal Damage Impeller Rub Clutch Failure

THRUST BEARING FAILURE 1.

Compressor impeller blades rubbed on inside of impeller cover.

2.

Thri.1.at bearing ramps smeared.

3.

Subsequent damage associated with thrust bearing failure: a. Planetary Gear Train Failure

b. Turbine Blade Breakage or Exit from Rotor c. Exhaust Diffuser Damage

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Electro-Motive Model 567, 645 & 710 Series Dlesel Engines

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COMPRESSOR BEARING FAILURE 1.

Impeller rub on cover (primarily at bottom).

2.

Subsequent damage which may accompany compressor bearing failure: a. b. c. d.

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Labyrinth Seal Damage Turbine Blade Tip Rub Planet Gear Train Failure Clutch Failure

TURBINE BEARING FAILURE 1.

Impeller rub on cover (primarily at top). Subsequent damage: See Compressor Bearing Failure.

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2.

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ROLLER CLUTCH FAILURE

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1.

Heavy carbon deposits on compressor impeller and engine air box.

2.

Inability to start engine.

3.

Smoke from engine exhaust (particularly during speed changes).

4.

Subsequent damage which could possibly occur due to clutch failure:

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Air Box Fire (due to heavy carbonaceous deposit formation).

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FOREIGN MATERIAL D A M A G E T O COMPRESSOR SECTION 1.

Nicked or torn impeller blades.

2.

Subsequent damage which can occur as a result of foreign material:

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a. b. c. d.

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Dented or Bent Compressor Diffuser Vanes Bearing Failure Impeller Rub Labyrinth Seal Damage

e. Clutch Failure

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PLANETARY GEAR TRAIN FAILURE 1.

Inability to start engine.

2.

Subsequent damage which can accompany planetary system failure: a.

Engine Rear Gear Train Damage

ITS LocomotiveTraining Series - Student Text

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LACK OF PROPER LUBRICATION 1.

All internal bearings exhibit distress (smearing, discoloring).

2.

Subsequent damage from lack of lubrication: a. Turbine Wheel Damage (impeller rub, blade tip contact; journal scoring, grooving or discoloration) b. Clutch Failure c. Planetary Gear Train Failure

TURBINE BLADE FATIGUE FRACTURE 1.

One or more turbine blades broken off at first serration in base.

2.

Turbine blade(s) broken off above base in airfoil section. (In either case, no signs of overheat/overspeed or foreign material damage will be present, simply a broken blade.)

3.

Subsequent damage which frequently accompanies blade fatigue: Bearing Failure Impeller Rub Clutch Failure C. d. Torn Exhaust Diffuser e. Punctured Turbine Shroud f. Planetary Failure g. Exhaust Duct Deformation h. Broken Turbine Wheel I. Loose Bolts in Turbo Cradle Area (severe vibration) Cracked Doweling Assembly Components 1.

a. b.

EXHAUST GAS LEAK 1.

Identified by presence of carbon on side of exhaust duct (on either the seal ring side or lap joint side).

TURBINE SHROUD RETAINING CLAMP FAILURE 1.

Clamp loose or missing when viewing down exhaust duct.

2.

Shroud displaced, bent or missing.

3.

Subsequent damage which may accompany clamp failure: a. b.

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Turbine Blade Tips Rubbed Bearing Failure ElectrMotive Model 567,645 & 710 Series Diesel Engines

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POOR PLANETARY GEAR TRAIN MESH 1.

Eroded planet bearings.

2.

Fatigue fracture of turbine blade.

3.

Planet gear or sun gear broken.

4.

Subsequent damage which may occur:

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a.

b. c.

Rotating Assembly Distress Clutch Failure Impeller Blade Fatigue Fracture

INTERNAL OIL LEAK 1.

Oil out of stack (no filter problems, no engine oil loss).

EXTERNAL GEAR DAMAGE 1.

Broken gear teeth on either idler or carrier drive gear.

2.

Damage on turbo drive gear portion of spring drive assembly.

3.

Subsequent damage which may occur: a. b.

Clutch Failure Planetary System Failure

TURBOCHARGER INSTALLATION TIPS The following precautions should be taken to minimize the risk of repetitive turbocharger failures:

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a. Inspect exhaust manifold and screen for foreign material or cracks. b. Inspect engine gear train for damage. c. Inspect engine air filter housing for debris or cracks.

d. Replace engine air filters. e. Replace engine oil filters if previous failure contaminated oil. f. Inspect aftercoolers for deposits and debris. g. Inspect engine power assemblies and air box. h. Check valve and injector timing.

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3 1.

Determine impeller “eye” clearance on replacement turbo prior to installation on engine as follows: a.

Remove turbo from box.

b.

Chalk mark one impeller blade at 1200 position.

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C.

Insert same thickness feeler blades at opposing blades between blade edge and impeller cover to determine clearance. Record:

d.

Install turbo on engine.

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Install aftercooler ducts:

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1200 16:OO Positions = 3:OO 19:OO Positions =

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1. Snug bolts at turbo end of duct 2. Torque bolts at engine end of duct (65 ft. lbs.). 3. Remove bolts from turbo end of duct. 4. With gasket in place, confirm that .008” feeler will not enter. 5. If .008” feeler enters, loosen and reposition duct on engine. 6. If necessary, holes in engine end of duct may be enlarged. 7 . Torque engine end bolts, repeat flange check. 8. Torque turbo end bolts.

f.

Repeat “eye” check now with turbo mounted:

1. Position chalk-marked blade at l2:OO. 2. Verify that all four readings are unchanged. 3. If readings cannot be repeated, loosen aftercooler bolts and re-align (if hole enlargement required, ream engine-end holes). g.

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If previous failure could have resulted from lubrication problem, such as an unexplained bearing failure, confirm oil flow to turbo prior to start-up. This can be accomplished with the soakback pump. Instructions can be found on page 4-3 under Turbocharger Oil Pressure Test.

ElectreMotive Model 567,645 & 710 Series Diesel Engines

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Oil seals in each end plate seal the rotor shafts to prevent oil from getting into the rotor housing .The rotor drive gears are splash lubricated and the lubricating oil is returned to the engine sump by an external drain line located at the bottom of the rear cover. Each blower is driven by a splined drive hub that is bolted to the blower drive gear which is driven by the camshaft drive gear. The splines of the drive hub mate with the splines of the quill shaft which has a flange on the other end which is bolted to one of the blower rotor gears.

From Engine Filter

To Air Box

Figure 7.39 Blower End View Cross Section -Air Flow

Blower Inspection Blowers should be inspected at intervals specified in the Scheduled Maintenance Program. They can be viewed by removing the rear air box covers and looking up through the blower support housing. Any signs of aluminum dust in the blower support housing or air box indicates blower bearings that have become worn enough to cause rotor interference. Any blower showing aluminum dust should be renewed as soon as possible. Oily rotor lobes, oil in the air box, and oil running down the blower support are signs of leaking oil seals, which indicates the blower should be changed. Clean strips on the rotor tips is a normal condition, caused by the close clearances between the rotors and the rotor housing. Also small scratches may be found on the clean strips, caused by dirt particles which have found their way into the blower, but these usually do not cause a problem, unless aluminum dust is present.

EXHAUST SYSTEM COMPONENTS rcJ,

Exhaust Manifold Function is to collect exhaust gases and remove them from engine with minimal restriction. Systems are comprised of sections which may span 1,2, or 3 pairs of cylinders and are interconnected.

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Electro-MotiveModel 567, 645 & 710 Series Diesel Engines

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Blower Engine Exhaust System Blower type system uses outlets or stacks, which number from 1 through 4 on various applications. Manifold sections connected to one another with strap-type clamps

NOTE: All sections have 114” drain holes at bottom. Three basic manifold types: Standard - Basic low restriction design.

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Spark Arrester - Has “traps” to collect carbonaceous particles to avoid throwing this material out stack. (Approved by U.S. Forestservice.)

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SilencerEpark Arrester - Similar to Spark Arrester type, but incorporating a silencing chamber to reduce noise.

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Figure 7.40 Typical 16 Cylinder Standard Exhaust System

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Figure 7.41 Typical Turbocharger Engine Exhaust System

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ITS Locomotive Training Series Student Text

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Screen Inspection Port The Screen Inspection Port must be periodically inspected for damage or plugging. The port makes inspection easier and eliminates removal of screen for inspection. EMD has a kit available to retrofit existing manifolds under part number 9336983. Refer to MI 9622 for installation details. This kit is designed for 645 rear manifold chamber and is not intended for 567 straight barrel. The inspection port provides 4” opening for viewing the condition of the screen.

Screen Inspection Port

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ullL._i Figure 7.42 Screen Inspection Port

NOTE: Screen still requires removal for cleaning.

Screen Assembly The screen assembly is located between turbocharger and rear manifold and is manufactured with numerous small diameter openings designed to prevent passage of foreign material. This protects the turbocharger (within limits) from broken power assembly components such as ring or valve fragments. Such material can destroy the turbocharger if it strikes the blades of the critically balanced turbine wheel. The screen is susceptible to plugging from carbon (souping), water treatment residue (cracked head or liner), etc. Plugged screen lowers turbo efficiency arid ultimately causes “burping” due to gas flow restriction. The screen plate attached to metal support strips within housing to allow thermal expansion without tendency to fracture.

I7-54

Screen

Figure 7.43 Typical Exhaust Met Screen.

Electro-Moti Model 567.645 & 710 Series Diesel Engines

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There are three major design variations:

1.

Standard (8358828) - Grid pattern of approximately 1/8” diameter holes.

2.

Trap - Type (8482700) - Same as above, but included small pocket located at bottom of housing to catch foreign objects and prevent them from repeatedly gouging at screen.

Objects would eventually tear screen or wear themselves down until small enough to pass. Trap keeps foreign material out of gas flow. Clean-out plug intentionally omitted from design to require screen removal. In this way, the exhaust manifold can be inspected for further debris. 3.

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Reduced Gradient “Starburst” Type P/N 9526331 - Included trap as above, but screen plate featured revised hole pattern. Holes positioned in radial lines from center outward. Resulted from tests indicating thermal expansion pattern was same. This screen’s service life is approximately double that of its predecessor. All 645 screens are now converted to this type. Figure 7.43 illustrates a typical “Starburst”type screen assembly.

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Exhaust System Data Engine Model

Turbine Inlet Temp

16-567C 16-645E3 20-65E3 16-645F3 16-645E3C 16-645F3B

900 (Ex Out) 870 Turbine In 930 Turbine In 980 Turbine In 864 Turbine In 880 Turbine In

Ex Gas CFM 14,100 21,100 22,900 23,750

--

19,975

Air Box Pressure

4-5 psi 17.5 18.4 20.5 19.5 21.8

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ITS Locomotive Training Series -Student Text

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CHAPTER Engine Speed Control

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Introduction

deals only

The engines covered in this program are equipped with a Woodward PGR governor as shown in Figure 8.1 which:

With

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conventional engine control.

regulates the amount of fuel delivered to the engine cylinders by the fuel injectors.

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EMDEC is covered in a separate training

assists in controlling main generator output by regulating main generator excitation through the load regulator.

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Program.

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b

By balancing generator load with a set engine speed, the governor maintains a constant kilowatt output by the engine/generator combination for each throttle position. Speed selection is accomplished through the actuation of combinations of electric solenoids within the governor; fuel control through the governors internal hydraulic system, hence the term electro - hydraulic. The governor senses engine RPM and adjusts the position of the layshaft, which in turn regulates fuel injector output to maintain engine RPM at the operator selected level.

The Woodward governor is a complex precision device; it will be covered in depth in a subsequent course however, this chapter will briefly cover some of the significant points.

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ITS LocomotiveTraining Series - Student Text

8-1

a

3 The governor has three main systems:

3 u)

speed sensing speed control load regulation

It also has a completely self contained hydraulic system with reservoir, pump, and accumulators to lubricate the internal parts and operate various parts of the governor,

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The governor has protective devices which will shut the engine down should there be a loss of pressure in the engines' lube oil system or a failure of the engines cooling system. Figure 8-1 Woodward Electro-Hydraulic Governor

16. OilDrainCock 17. T e n i d Shaft control

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Speed Sensing and Fuel Control The basic operation of the Woodward governor is illustrated in Figure 8.2. Fuel Limit Lock Nut Fuel Limit Nut 0.79 mm (1/32") Gap At Idle

Shutdown Rod Bushing Locknut Shutdown Bushing

Speed Setting Piston

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Figure 8.2 Basic Operation 8-2

ElectroMotive Model 567,645 & 710 Series Diesel Engines

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The governor drive shaft is driven from the accessory gear train through an angle drive unit and provides the energy to drive the governors components and sense and respond to changes in engine speed. This drive shaft turns the enclosed hydraulic gear pump, the flyweight assembly and the rotating bushing which encloses the pilot valve. As the governor rotates, oil is pumped into accumulators to provide a working supply of oil under pressure for the governor. The flyweights are mounted on pivots and held inwards by the pressure of the speeder spring on their fingers. These fingers are also connected to the top of the pilot valve that controls the flow of oil to and from the power piston.

As the engine is started, the centrifugal force of the flyweights is insufficient to overcome the pressure of the speeder spring. The pilot valve is held down and allows oil to flow from the accumulators, through the rotating bushing, and through the buffer piston to the underside of the power piston. Oil pressure under the power piston builds up and overcomes spring pressure to move the piston upwards. Fuel injection rates are controlled by the power piston, which through the layshaft and racks, controls the fuel injectors. Raising the power piston moves the layshafts, which in turn move the injector racks inwards to a higher fuel position.

As more fuel is delivered to the engine and speed increases, centrifugal force on the flyweights causes them to move outwards, raising the pilot valve plunger and shutting off the supply of oil to the underside of the power piston. This action maintains fuel delivery, and engine speed, at a set level. Should engine speed increase beyond desired, the weights move outwards further, raising the pilot valve plunger. This opens ports to allow oil to drain back from the underside of the power piston. The power piston moves down, cutting back the amount of fuel delivered to the engine. Engine RPM stabilizes in the "balance" position, controlled by the action of the flyweights and speeder spring pressure.

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ITS LocomotiveTraining Series - Student Text

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Speed Control In the last section we saw how the governor maintains engine speed in the "balance" position. Now we will look at how the governor responds to changes in the throttle position by means of the speed setting system (Figure 8.3) Speed setting of the governor is accomplished by energizing different combinations of the four electric solenoids (A,B,C,D). The A, B, and C solenoids have plungers that bear on a triangular plate, attached to a fulcrum point on a lever. Each of these three solenoids is positioned at a different distance from the fulcrum point of the plate.

By energizing different solenoids (or combinations of solenoids) the plate is depressed to different levels.

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Figure 8.3 Speed Control

The lever is attached to the top of the speed control pilot valve on one end; and through linkages to the top of the speed setting piston on the other end. The D solenoid is attached to another rotating bushing which surrounds the speed setting pilot valve. When the throttle is moved to a higher position, calling for more engine speed, one solenoid (or a combination of solenoids) are energized. Energizing the solenoids causes the triangular plate to be depressed. Through the plate and lever, the speed setting pilot valve is depressed, allowing oil to flow to the top of the speed setting piston. 8-4

Electro-Motive Model 567.645 & 710 Series Diesel Engines

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Load Regulation The next part of the governor to be covered is the load regulation system (Figure 8.4). This system controls the excitation of the main generator, and balanced with engine RPM, the power output. This section provides a brief description of the operation as system will be dealt with in detail in later courses. The system uses linkages and a load regulator pilot valve to control oil flow to and from the load regular vane motor.

Figure 8.4 Load Regulation

The vane motor operates a resistor that controls the current used for main generator excitation, and therefore output. (on microprocessor controlled locomotives, the load regulator sends a reference signal to the computer to control loading). 8-6

Electro-MotiveModel 567,645 & 710 Series Diesel Engines

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If the horsepower demand is less than or greater than the engine is adjusted to develop for a given RPM, then this system will increase or decrease generator excitation

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(and therefore output) to meet the changed demand.

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If the horsepower demand is less than rated, oil is directed to one side of the vane motor to increase resistance in the main generator field circuit, and cut back horsepower developed. At the same time, the governor responds by cutting back fuel delivery to maintain a constant engine RPM.

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If the horsepower demand is more than is proper for a set engine speed, again the load regulator system will limit the main generator output and engine fuel delivery to maintain a maximum rated output. In addition to basic load regulation, the system also compensates for engine performance variations caused by barometric pressure changes. Should barometric pressure (or airbox pressure) reduce, the load regulator system is affected by the change in pressure. The lower the air box pressure, the sooner the load regulator will limit main generator excitation. Another component of this system is the overriding solenoid (ORS),which when energized by other systems, such as wheel slip, will act to reduce excitation.

Protective Devices

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The low lube shutdown system protects the engine in case of a failure of the mechanical support systems.

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The shutdown system can be activated by:

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"True" low lubricating oil pressure;

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"False" low lube pressure caused by a failure of i e cooline svstem ant detected by either of the low cooling water portion of the E.P.D. or hot oil detector;

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"False" low lube pressure caused by the E.P.D. sensing a positive crankcase pressure (crankcase is normally under a slight vacuum);

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"False" low lube pressure caused by manual engagement of the system connected to a lube oil line from the engine on one side and speed setting oil pressure on the other side.

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u cus 3 ts 3 3 Figure 8.5 Low Lube Oil Shut Down

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Should oil pressure in the line drop below the speed setting oil pressure, the system will take action to shut down the engine.

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When the engine is at idle, there is a mechanism that builds in a delay of 50 to 60 seconds. This delay is to allow oil pressure to build up when starting the engine. The delay is reduced in steps to the third throttle position. In the fourth position and higher there is no time delay in the shut down system.

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To shut the engine down, the system bleeds the speed setting oil from the top of the speed setting piston. The governor reacts by moving the layshaft and racks to the no fuel position, shutting down the engine.

A switch is tripped setting off an alarm in the operators cabin, and a plunger protrudes from the side of the governor exposing a red band. The engine cannot be restarted until this plunger is reset. The hot oil detector and engine protective device both simulate a loss of oil pressure by bleeding oil pressure off of the line to the governor.

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Eiectro-Motive Model 567,645 & 710 Series Diesel Engines

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Governor Maintenance Governor oil should be changed at regularly scheduled intervals. Always maintain governor oil level to the top mark in the governor oil level gauge. A large percentage of governor problems are caused by dirty oil. Always use clean oil and a clean container when topping up or refilling the governor. Dirt and other impurities can be introduced with governor oil or can form when oil breaks down or forms sludge. Dirt or sludge can cause the valves, pistons, or plungers inside the governor to stick or seize in their bores causing erratic operation and poor response.

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In some instances where it is not possible to remove the governor to disassemble and clean it, governor performance may be restored by flushing the governor with fuel oil or kerosene. Solvents should not be used to flush a governor, as they can damage sea,, and gaskets.

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Governor Flushing Open the drain cock and drain the governor oil.

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Refill the governor with clean fuel oil and restart the engine.

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Using the injector control lever, vary the engine speed from approximately 400 to 500 RPM for about five minutes, then stop the engine and drain the fuel oil from the governor.

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Repeat the process until the fuel oil drained appears clean, then fill the governor with clean governor oil.

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Restart the engine and repeat the above process, then drain the oil to remove any trapped kerosene.

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Fill the governor with clean oil. Adjust the compensation needle valve using the following procedure.

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Compensation Adjustment The compensating mechanism prevents the engine from "hunting" or racing by arresting the movement of the power piston after it has travelled a sufficient amount to give the desired speed. Compensation adjustment is the only adjMsDent that is recommended-to be done with the governor on the engine. All other governor adjustments should be done on a calibrated test stand by specially trained personnel. Adjustment of the compensation mechanism is required when an engine is being started for the first time, after installation of a new or reconditioned governor, or after a governor has been drained and cleaned and new oil added.

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ITS Locomotive Training Series Student Text

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This adjustment purges the governor oil system of trapped air. Adjust the compensation as follows: Ensure that the governor oil level is between the lines on the sight glass.

Start the engine and operate at idle speed. Open the compensating needle valve by turning counterclockwise several turns. Loosen the vent plug several turns, but do not remove it. The engine will hunt and surge, and air will bleed from the system at the vent plug. When onlv oil flows from the vent plug, slowly close the compensating needle valie until the hunting stops or slows. Tighten the vent plug to prevent oil leakage, and add oil to the governor if necessary. Allow the engine to reach normal operating temperature, then open the compensating needle valve and allow the governor to hunt. Close the needle valve until the hunting stops. Test the governor by changing speeds with the injector control lever observing the governor recovery. If the governor returns to a steady speed, the adjustment is satisfactory. If hunting resumes, close the compensating needle valve slightly then test again. This compensating needle valve should be kept open as far as possible to prevent sluggishness and still maintain even governor operation. After compensation is set, it should not require another adjustment.

17. Temhul Shalt canmi

Figure 8.6

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Electro-Motive Model 567.645 & 710 Series Diesel Engines

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Governor Qualification

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Many governors are needlessly changed out because of the lack of proper troubleshooting procedures. Governor problems usually show up as engine speed variations such as hunting, surging or jiggle, but an engine showing signs of engine speed variation does not necessarily have a governor problem. Before changing a suspected governor, verify that the speed variation is not caused by one of the following conditions:

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Check the linkage between the governor and the fuel racks for binding or excessive backlash.

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Disconnect each injector from the injector control shaft by removing the pin from the adjusting link, then operate the injector rack in and out checking for binding or tight spots. Make sure all injectors are the proper type for the application.

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Check engine operation to be sure that all cylinders are firing properly.

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Check for bubbles in the return fuel sightglass. If evident, verify that the fuel system is functioning properly, using the checks in the fuel system troubleshooting section of this text.

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Check the setting of the governor compensation needle valve. Ensure that the load on the engine is not fluctuating and causing the engine RPM to respond to these changes. Items to check include the load regulator wiper arm to make sure the vane motor is not causing the load regulator to hunt, excitation circuit causing overexcitation of the main generator and ma1 function of protective device such as current overload relays.

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With the engine at maximum speed and full load, check the quadrant on the governor. If the rack dimension is shorter than the limit on the governor identification plate, the engine is either overloaded or lacking fuel.

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Check speed setting circuits for correct voltage levels and proper sequencing.

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Check the governor drive for any evidence of misalignment, roughness, or excessive backlash.

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Flush governor following the procedure outlined in this chapter. _

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ITS LocomotiveTraining Series -Student Text

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CHAPTER Protective Devices

Introduction There are many devices and systems on the locomotive designed to protect the locomotives mechanical and electrical systems. In this section we will focus on the main protective devices that protect the engine against;

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Low water, Crankcase Pressure HotOil LowOi1,and Engine Overspeed

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EPD ENGINE PROTECTION DEVICE

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Low Water & Crankcase Pressure Protection

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A low water detecting portion of the EPD,(Figure 9. l), balances water pressure against airbox pressure. When water pressure falls, the device dumps oil from the

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governor supply line, causing an engine shutdown.

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While there is no air box pressure when an engine is shut down, there is spring pressure. This spring pressure must be acted against by water pressure in order to keep the device latched in. On certain devices the static water pressure working against spring pressure will not keep the device latched in when the engine is shut down. This is not necessarily an indication that the device is defective. It is merely necessary to reset the device immediately after engine start.

Figure 9.1 EPD

Testing EPD Operation Operation of the low water shutdown device, Fig.9.2, should be checked at the intervals stated in the Scheduled Maintenance Program or whenever faulty operation is suspected.

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To test operation of the low water detecting device, run the engine at idle speed and turn the test cock mounted on the water pump discharge elbow to the horizontal position. The low water button should pop out smoothly without hesitation after water trapped behind he operating diaphragm escapes through the drain hole provided (in not mom than a fa0 seconds oftime). Return the test cock to the vertical position.

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Figure 9.2 Test Cock Operation

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Observe the low oil plunger on the governor as it moves out. The plunger should extend fully and the engine begin to shut down in about 5 5 seconds. As the engine begins to shut down reset the low water button and the low oil plunger. Operate the rack positioning lever to bring the engine back up to idle speed before complete shutdown. Verify that the low water button stays set. If the low water shutdown reset pushbutton does not pop out freely without assistance when the test cock is opened and the engine is at idle. the device should be removed and replaced with an operative device. Refer to the Service Data page for a listing of instructions covering maintenance and qualification of the low water protector. Special apparatus is required for proper testing. The crankcase pressure detector may be tested in a similar manner by applying a rubber tube over the test opening on top of the detector and applying suction to trip the upper button. The combination low water and crankcase pressure detector is a mechanically operated, pressure-sensitive device designed to determine abnormal conditions of engine coolant and crankcase pressures. The low water safety device is a spring loaded, normally open, two-way valve piloted by a latching mechanism on a diaphragm stack. There are two diaphragms in the stack; one sensing water pressure into the engine, and the other sensing engine air box pressure.

-NOTE:

The air box-to water diaphragm area ratio for TURBOCHARGED IS 1 :l.

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The air box-to water diaphragm area ratio for BLOWER (ROOTS)IS 3:l.

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Under normal operating conditions water pressure exceeds air box pressure.

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The low water reset button WILL TRIP when water pressure IS within 1/2 psi of air box pressure. The following conditions will cause the detecor to trip:

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Loss of water level.

Pump cavitation due to air entrainment (during sxrting).

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Pump cavitation due to water temperature apprcaching boiling point. Applicable to non-pressurized systems.

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Excessive air box pressure due to turbine surging at low throttle

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speeds. (Turbochargedengines only.)

OVERFILLING the water tank can cause low waTer shutdown.

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ITS LocomotiveTraining Series -Student Text

3. Air Box Pressure 4. Oil In From Governor 5. Trip Position 6. Latch Position 7. Oil Return To Crankcase 8. Vent Fitting 9. Crankcase Pressure

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Figure 9.3 Low Water Pressure Condition

In some installations, the test cock is locateu at the bottom of the device while, in others, it is in the water pump outlet elbow. By rotating the test cock handle as illustrated in Figure 9.2, to the horizontal position, the discharge of water from the small orifice hole in the cock should be a steady flow. Because of contaminants in the cooling water, the small orifice in the cock may become plugged, reducing or restricting the bleed off of water pressure on the water diaphragm. In most cases, rapidly opening and closing the test cock a few times will dislodge the obstruction and allow the low water detector to trip. Plugging of the test cock in no way affects the operation of the low water device. With the engine running at idle speed, placing the test cock in the horizontal position, and obtaining a free flow of water from the orifice, should trip the device on the first or second try. If the device does not trip, the device should be taken off and checked on a test panel to determine the cause of malfunction. It is recommended that .”* ector be checked monthly. the operation of the lo *CI ”’4.X rb(

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ElectroMotive Model 567.645 & 710 Series Diesel Engines

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1. Water Pump Discharge Pressure 2. Water Pump Inlet Pressure 3. Alr Box Pressure 4. Oil In From Governor 5. Latch Position 6. Trip Position 7. Oil Return To Crankcase 8. Vent Fitting 9. Crankcase Pressure Positive

Figure 9.4 Positive Crankcase Pressure Condition

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Crankcase Pressure Detector (EMDEC)

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The crankcase pressure detector used on EMDEC equipped engines senses any malfunction which causes a positive, rather than the normally negative engine crankcase pressure. When the device senses a positive crankcase pressure, it trips a switch to signal the EMDEC master Electronic Control Module (ECM) which shuts the engine down.

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The EMDEC switch type crankcase pressure detector has a long stem held in a latched position until a positive pressure builds up in the crankcase. This pressure pushes on the large diaphragm which, in moving, releases the long stem. Outward movement of the stem operates a lever to close contacts in a switch mechanism attached to the bottom of the detector. This switch provides the shutdown signal to the ECM. Negative pressure is normally maintained by the crankcase ventilating equipment. The following are sonqiitions (upgly to troth EMDEC and mechanical injector systems) that can cause a crankcase pressure detector to trip: Blocked oil separator or aspirator tube in the exhaust, excessive oil level in crankcase, resulting in blockage of oil separator. Cylinder compression leak into the oil pan or top deck from a cracked cylinder head, cracked piston, loose injector, improperly installed or broken rings, broken valves or badly worn valve guides. I

ITS Locomotive Training Series - Student Text

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Pressurized air from the air box leaking to the crankcase from hardened or broken liner seals, broken crab bolts, loose crab bolt retainers or extreme cylinder scoring. Overheated part in crankcase igniting oil vapours (crankcase explosion). Incorrectly installed lube oil pressure relief valve, allowing oil splash to reach the diaphragm of the detector.

-WARNING: Following an engine shutdown caused by the tripping of a conventional or EMDEC crankcase pressure detector, DO NOT open any handhole or top deck covers to make an inspection until the engine has been stopped and allowed to cool for at least 2 hours. DO NOT attempt to restart the engine until the cause of trip has been determined. The action of the pressure detector indicates the possibility of a condition within the engine, such as an overheated bearing, that may ignite the oil vapours with an explosive force, if air is allowed to enter the engine. If the crankcase pressure detector cannot be reset, DO NOT operate the engine until the pressure detector has been replaced, since the diaphragm backup plates may be damaged.

Figure 9.5 Crankcase Pressure Detector

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Electro-MotiveModel 567,645 & 710 Series Diesel Engines

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Hot Oil Detector A thermostatic valve located on the outlet elbow from the main lube oil pump is calibrated to open when lube oil temperature reaches nominally 260°F (126OC).At this temperature the probability exists that either the lube oil cooler is plugged on the water side, or steam pressure in the cooling system is preventing engine shutdown by the low water detector. When oil temperature causes the valve to open, pressure in the line to the oil pressure sensing device in the engine governor is dumped. The device sees low oil pressure and reacts to shut the engine down.

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Fig. 9.6 Hot Oil Detector Thermostatic Valve

and Location (Right)

The thermostatic valve is non latching, and it will reset automatically when oil temperature falls. The engine may then be restarted when the governor low oil plunger is reset. -WARNING: After it has been determined that hot oil is the cause for engine shutdown, make no further engineroom inspections until the engine has cooled sufficiently to preclude the possibility that hot oil vapor may ignite. When a low Oil shutdown occurs, always inspect for an adequate supply of water and oil before attempting to restart the engine. Also check engine water temperature. Do not add cold water to an overheated engine.

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ITS Locomotive Training Series -Student Text

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The hot oil detector should be removed from the engine and tested at intervals suggested in the applicable Scheduled Maintenance Program. Test the hot oil detector as follows: Connect a 50 psi (345 kPa) air line to the hot oil detector inlet port (port with arrow) Attach a return line to the outlet port to prevent creating oil spray when detector opens. Place detector in a 235" F ( 112.6'C) oil bath with a thermometer. Check for leaks between the body and cap. Increase the temperature of the oil bath to 258" F (12SoC),the valve should open. If not the detector should be replaced with a qualified unit, On locomotives equipped with EMDEC fuel injection, the Hot Oil Detector has been replaced with a Lube Oil Temperature sensor which reports the oil temperature to the computer.

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Low Lube Oil Shut Down

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The low lube shutdown system protects the engine in case of a failure of the mechanical support systems.

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3 The shutdown system can be activated by:

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"True" low lubricating oil pressure;

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"False" low lube pressure caused by a failure of the cooling system and detected by either of the low cooling water portion of the E.P.D. or hot oil detector;

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"False'' low lube pressure caused by the E.P.D. sensing a positive crankcase pressure (crankcase is normally under a slight vacuum);

4.

"False" low lube pressure caused by manual engagement of the system connected to a lube oil line from the engine on one side and speed setting oil pressure on the other side.

Should oil pressure in the line drop below the speed setting oil pressure, the system will take action to shut down the engine. When the engine is at idle, there is a mechanism that builds in a delay of 50 to 60 seconds. This delay is to allow oil pressure to build up when starting the engine. The delay is reduced in steps to the third throttle position. In the fourth position and higher there is no time delay in the shut down system.

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To shut the engine down, the system bleeds the speed setting oil from the top of the speed setting piston.

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LOW Oil Pressure Shutdown Plunger

The governor reacts by moving the layshaft and racks to the no fuel position, shutting down the engine.

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A switch is tripped setting off an alarm in the operators cabin, and a plunger protrudes from the side of the governor exposing a red band. The engine cannot be restarted until this plunger is reset.

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The hot oil detector and engine protective device both simulate a loss of oil pressure by bleeding oil pressure off of the line to the governor. Figure 9.7 Low Oil Shutdown Button

Engine Overspeed The engine overspeed trip is a mechanical safety device to stop fuel injection if engine speed exceeds specified limit. A flyweight mounted on counterweight at front of right bank camshaft activates the trip. ll centrifugal force exceeds adjustable spring tension, flyweight moves out. LATCHED msinoN TRIPPED POSrnON When the flyweight moves out, it contacts the trip pawl. Figure 9.8 Overspeed Trip The Trip pawl uses an actuating spring to move connecting links, which rotate a trip shaft on each bank of the engine. The trip shafts extend along each top deck behind thecylinder heads. Under each : injector rocker arm,-there is a pawl in contact with a small cam on the trip shaft. C T ~pt*) When the tri cam rotates upward, it raises a pawl under the rocker arm to prevent further actuation o the el injector.

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An external latch lever is located on the overspeed trip housing just above the accessory drive housing.

Trip speed is usually set at 10% in excess of normal engine full speed; 900 rpm units trip at 990 rpm.

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ITS Locomotive Training Series Student Text

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Figure 9.7 Overspeed Trip

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16-71OG limit has been revised to 1035-1050 rpm to prevent tripping system during locomotive transition.

Adjustment Determine trip speed using a hand tach applied to end of camshaft through access cover on RH front camshaft cover of trip housing. Run engine up until trip lever moves. NOTE If trip does not occur before 990 rpm (orotherwise specified maximum speed), do not exceed the 10% overspeed. The mechanism needs adjustment.

Shut engine down and remove large cover from right side of housing. Back-off spring tension by loosening locknut, then adjusting nut.

Note: Loosening spring tension decreases t i p speed. Secure nuts and restart engine. Again using hand tach, observe trip speed. Repeat as necessary to fall within specified range.

Note: Always make adjustments in tightening direction.

The minimum clearance between flyweight and pawl is .010".

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Electro-Motive Model 567,645 & 710 Series Diesel Engines

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SYSTEM BLOCK DIAGRAM "EMDEC" 16 Cylinder

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