Cerrar SIS Pantalla anterior Producto: GEN SET ENGINE Modelo: 3412 GEN SET ENGINE 81Z02545 Configuración: 3412 ENGINE GENERATOR SET 81Z00001-04999
Operación de Sistemas 3408B and 3412C Generator Set Engines Número de medio -SENR2562-03
Fecha de publicación -01/03/2001
Fecha de actualización -16/11/2001
i00730076
Fuel System SMCS - 1250 S/N - 78Z1-UP S/N - 81Z1-UP These engines have a pressure type fuel system. There is one injection pump and one injection nozzle for each cylinder. The injection pumps are in the pump housing (4) on the top front of the engine. The fuel injection nozzles are located in the fuel injection adapters. The fuel injection adapters are under the valve covers. The fuel transfer pump (16) pulls the fuel from the fuel tank (10) through the primary fuel filter (12). The fuel flows from the primary fuel filter (12) to the fuel priming pump (8) and through the main fuel filters (14). The fuel then flows to the manifold of the injection pump housing. The fuel in the manifold of the injection pump housing flows to the injection pumps. The injection pumps are in time with the engine. The injection pumps push fuel at a very high pressure to the injection valves (6).
Illustration 1
g00332354
Fuel flow schematic 3412C shown (1) Fuel inlet line for the injection pump housing. (2) Damper. (3) Restriction orifice. (4) Injection pump housing. (5) Fuel return line. (6) Injection valve. (7) Junction block. (8) Fuel priming pump. (9) Priming bypass valve. (10) Fuel tank. (11) Fuel supply line. (12) Primary fuel filter. (13) Fuel pressure gauge. (14) Main fuel filters. (15) Pressure relief valve. (16) Fuel transfer pump.
A damper (2) is located on the inlet elbow of the fuel manifold (19). The damper (2) reduces the shock loads that are caused by the injection pumps. Some of the fuel in the fuel manifold is constantly sent through a restriction orifice (3). This removes air from the system. This restriction keeps the fuel
pressure high. The restriction also controls the amount of fuel that goes back to the fuel tank through the fuel return line (5).
Illustration 2
g00332357
Location of the fuel system components 3412C shown (1) The fuel inlet line for the injection pump housing. (2) Damper. (3) Adapter with orifice. (5) Fuel return line. (11) Fuel supply line. (16) Fuel transfer pump. (17) The fuel outlet line from the transfer pump and the inlet line to the main filters. (18) The nut for a fuel injection line at the injection pump. (19) The fuel manifold across the injection pump housing. (20) Adapter through the valve cover base.
The fuel priming pump (8) is used to fill the system with fuel. The fuel priming pump also removes air from the low pressure side of the fuel system. The low pressure side of the fuel system consist of the fuel filter, the fuel lines and components.
Illustration 3 The location of the fuel system components 3412C shown
g00332494
(1) The fuel inlet line to the injection pump housing. (5) The fuel return line to the tank. (7) Junction block. (8) Fuel priming pump. (11) Fuel supply line. (14) Main fuel filters. (17) The fuel outlet line from the transfer pump and the inlet line to the main filters.
The fuel transfer pump has a bypass valve and a check valve. The bypass valve controls the maximum pressure of the fuel. The extra fuel goes to the inlet of the pump. The check valve allows the fuel from the tank to go around the transfer pump gears when the priming pump is used.
Illustration 4
g00332514
The location of the fuel system components 3412C shown (1) The fuel inlet line for the injection pump housing. (5) The fuel return line. (7) Junction block. (8) Fuel priming pump. (11) Fuel supply line. (14) Main fuel filter. (17) The fuel outlet line from the transfer pump and the inlet line to the main filter.
Fuel Injection Pump
Illustration 5
g00332516
The cross section of the fuel injection pump housing (1) Fuel manifold. (2) Inlet passage. (3) Check valve. (4) Pressure relief passage. (5) Pump plunger. (6) Spring. (7) Gear. (8) Fuel rack (left). (9) Lifter. (10) Link. (11) Lever. (12) Camshaft.
The rotation of the cams on the camshaft (12) cause the lifters (9) and the pump plungers (5) to move up and down. The stroke of each pump plunger is always the same length. The force of the springs (6) hold the lifters (9) against the cams of the camshaft. The pump housing is in a shape of a V. The shape is similar to the engine cylinder block. There is the same number of pumps on each side. When the pump plunger moves down, the fuel from the fuel manifold (1) flows through the inlet passage (2). The fuel then fills the chamber that is above the pump plunger (5). When the plunger moves up, the plunger closes the inlet passage. The pressure of the fuel in the chamber above the plunger increases until the pressure is high enough to cause the check valve (3) to open. The high pressure fuel flows through the check valve, to the injection valve, through the fuel line until the inlet passage opens into the pressure relief passage (4) in the plunger. The pressure in the chamber decreases and check valve (3) closes.
The amount of fuel forced through the check valve (3) is determined by the period of time the inlet passage (2) is closed. The pressure relief passage (4) will control the amount of time the inlet passage is closed. The amount of time the inlet passage is closed can be changed because of the design of the passage. This can be changed by rotating the plunger. When the governor moves the fuel racks (8), the fuel racks move the gears (7) that are fastened to the plungers (5). This causes a rotation of the plungers. The governor is connected to the left rack. The spring load, located on the lever (11), removes the play between the racks and the link (10). The fuel racks are connected by the link (10). The fuel racks move in opposite directions. When one rack moves in, the other rack moves out.
Fuel Injection Valves And Nozzles The injection valves are located within the fuel injection adapters. The fuel injection adapters are installed in the cylinder head. The fuel injection pump sends fuel with high pressure to the fuel injection valves. The fuel injection valves change the fuel to the correct spray pattern for good combustion in the cylinders. The fuel injection valves will not open until a very high pressure is reached. Once this pressure is reached, the fuel injection valves open quickly. The fuel is released directly into the engine cylinder through six orifices in the tip of each nozzle.
Hydramechanical Governor With Dashpot The governor controls the amount of fuel that is needed by the engine to maintain a desired rpm. The governor maintains a constant rpm for variable engine loads. When the engine is operating, the balance between the centrifugal force of the governor weights and the force of the governor control on the governor spring, controls the movement of a valve and indirectly, the fuel rack. The valve directs pressure oil to either side of a rack positioning piston. The position of the valve controls the rack. The amount of fuel to the engine is controlled by the rack and load conditions.
Illustration 6
g00332517
Hydramechanical governor with dashpot (1) Collar. (2) Collar bolt. (3) Dashpot chamber. (4) Dashpot piston. (5) Lever assembly. (6) Dashpot spring. (7) Governor spring. (8) Governor weights. (9) Valve. (10) Cylinder. (11) Drive assembly. (12) Pin. (13) Lever.
The governor has governor weights (8) that are driven by the engine through the drive assembly (11). The governor has a governor spring (7), a valve (9) and a piston. The valve and the piston are connected to one fuel rack through pin (12) and lever (13) . The governor control is connected to the governor control lever. The governor control controls the compression of the governor spring (7). The compression of the spring gives more fuel to the engine. The centrifugal force of the governor weights (8) always pulls up to get a reduction of fuel to the engine. When these two forces are in balance, the engine runs at a constant rpm.
Illustration 7
g00456122
(A) Pressure oil. (7) Governor spring. (8) Governor weights. (9) Valve. (10) Cylinder. (12) Pin. (14) The oil drain passage for the piston. (15) The upper oil passage in the piston. (16) Piston. (17) The lower oil passage in the piston. (18) The oil passage in the cylinder. (19) Sleeve.
Governor in increased load position The governor oil pump is on top of the fuel injection pump housing. The governor oil pump sends engine oil under pressure to the governor cylinder (10) through passage (18) around sleeve (19) . When the load on the engine increases, the engine rpm decreases. This will cause a slower rotation of the governor weights (8). The governor weights will move toward each other. The governor spring (7) moves valve (9). This will open the oil passages in piston (16). This will also close the oil drain passage (14). This will allow the oil to flow from passage (17), around valve (9), and through passage (15). This will fill the chamber above piston (16). The pressure oil pushes down on piston (16) and pin (12). This gives more fuel to the engine. Engine rpm increases until the rotation of the governor weights is fast enough to be in balance with the force of the governor spring.
Illustration 8
g00456195
(A) Pressure oil. (B) Drain oil. (7) Governor spring. (8) Governor weights. (9) Valve. (10) Cylinder. (12) Pin. (14) The oil drain passage for the piston. (15) The upper oil passage in the piston. (16) Piston. (17) The lower oil passage in the piston. (18) The oil passage in the cylinder. (19) Sleeve.
Governor in decreased load position When there is a reduction in load on the engine, there will be an increase in engine rpm and the rotation of the governor weights (8) will increase. This will move valve (9) to a higher position. This stops the oil flow from passage (17) and the oil pressure above piston (16) goes out around valve (9) through the top of the piston (16). The pressure between sleeve (19) and piston (16) pushes the piston and pin (12) to a higher position. This causes a reduction in the amount of fuel to the engine. The engine rpm decreases until the centrifugal force of the governor weights is in balance with the force of the governor spring. When these two forces are in balance, the engine will run at a constant rpm. When the engine rpm is at LOW IDLE, a spring loaded plunger in the lever assembly (5) is in contact with a shoulder on the adjustment screw for low idle. To stop the engine, move the switch to the "OFF" position. This will cause the shutoff solenoid to move the spring loaded plunger over the shoulder on the low idle adjustment screw. This will move the fuel racks to the fuel shutoff position. With no fuel to the engine cylinders, the engine will stop. To stop the engine manually, turn the shutoff lever on the governor housing to the shutoff position. The oil from the governor pump lubricates the following components:
• The governor weight support and gear • The thrust bearing under the governor spring • The drive gear bearing The other parts of the governor receive lubrication from splash lubrication. Splash lubrication is oil that is thrown by other parts. The oil flows from the governor to the housing for the fuel injection pumps. Electric set engines need a governor that has better control over the engine speed range. A standard hydramechanical governor can not provide this function. The following parts are added to the basic hydramechanical governor. • A dashpot piston (4) • A dashpot spring (6) • A collar bolt (2) • An oil reservoir in the shutoff housing • Two adjustment screws (20) and (21) These parts control the flow of oil into the dashpot chamber (3) and out of the dashpot chamber (3). The dashpot chamber (3) is above the dashpot piston (4). The oil flows through internal oil passages. The correct oil flow into the dashpot chamber (3) and out of the dashpot chamber (3) causes a more precise movement of the governor spring seat. This allows the governor to accurately control the engine speed. Side View Of The Governor
Illustration 9
g00332522
Side view of governor (20) The adjustment screw for the dashpot. (21) Adjustment screw for supply oil to the reservoir.
The oil for the action of the dashpot comes from the engine lubrication system. The adjustment screw (21) controls the oil flow from the lubrication system into the reservoir. The reservoir has an oil overflow that sends the oil back to the mechanical area of the governor. Too much oil flow to the reservoir will fill the governor with oil. This will decrease the engine performance. Too little oil flow does not give enough oil to the reservoir. The decrease in oil will cause the governor to hunt (increase and decrease engine speed constantly) as air gets into the dashpot chamber (3) and allows piston (4) and the lower governor spring seat move faster. The dashpot adjustment screw (20) causes a restriction to the oil flow into the dashpot chamber (3) and out of the dashpot chamber (3). Too much oil flow will allow the lower governor spring seat to move faster. This will allow the governor to hunt. Too little oil flow causes a slower action by the governor.
Automatic Timing Advance Unit
Illustration 10 Automatic timing advance unit
g00332523
(1) Flange. (2) Weight. (3) Springs. (4) Slide. (5) Drive gear. (6) Camshaft.
The automatic timing advance unit is installed on the front of the camshaft (6) for the fuel injection pump. The timing gears drive the automatic timing advance unit. The drive gear (5) for the fuel injection pump is connected to the camshaft (6) by the following components: • Two weights (2) • Springs (3) • Two slides (4) • Flange (1) Each one of the slides (4) is held on the drive gear (5) by a pin. The weights (2) in the timing advance are driven by two slides (4). These slides (4) fit into notches that are made on an angle in the weights (2). When the centrifugal force (rotation) moves the weights (2) outward against the springs (3), the guides in the flange and the slides on the gear make the flange turn a little in relation to the gear. Since the flange is connected to the camshaft for the fuel injection pump, the fuel injection timing is also changed. The unit advances the fuel injection pump camshaft 2% between approximately low idle and 1100 rpm. No adjustment can be made in the advance unit.
Woodward PSG Governors
Illustration 11
g00332574
Schematic of PSG governor (1) Return spring. (2) Output shaft. (3) Output shaft lever. (4) Strut assembly. (5) Speeder spring. (6) Power piston. (7) Flyweights. (8) Needle valve. (9) Thrust bearing. (10) Pilot valve compensating land. (11) Buffer piston. (12) Pilot valve. (13) Pilot valve bushing. (14) Control ports. (A) Chamber. (B) Chamber.
Introduction The Woodward PSG (Pressure compensated Simple Governor) can operate as an isochronous governor or a speed droop governor. This governor uses engine lubrication oil that has been increased
to a pressure of 1200 kPa (175 psi). The pressure is increased by a gear type pump that is located inside the governor. This pump gives the governor a hydramechanical speed control.
Pilot Valve Operation A gear on the rear of the fuel injection pump camshaft drives a vertical pinion shaft. The pinion shaft turns the pilot valve bushing (13) counterclockwise as seen from the drive unit end of the governor. The pilot valve bushing is connected to a ballhead. The ballhead is driven by a spring. Flyweights (7) are fastened to the ballhead by pivot pins. The centrifugal force caused by the rotation of the ballhead causes the flyweights to pivot out. This action of the flyweights changes the centrifugal force to axial force against the speeder spring (5). There is a thrust bearing (9) between the toes of the flyweights and the seat for the speeder spring. The pilot valve (12) is fastened to the seat for the speeder spring. Movement of the pilot valve is controlled by the action of the flyweights against the force of the speeder spring. The engine is at the governed rpm when the axial force of the flyweights is equal to the force of the compression in the speeder spring. The flyweights will be in the shown position. The control ports (14) will be closed by the pilot valve. Fuel Increase The pilot valve will move in the direction of the drive unit when either of the following conditions exist. • The force of compression in the speeder spring increases (operator increases desired rpm) • The axial force of the flyweights decreases (load on the engine increases) This opens control ports (14). The pressure oil flows through a passage in the chamber (B). The increased pressure in the chamber (B) causes the power piston (6) to move. The power piston pushes the strut assembly (4), which is connected to the output shaft lever (3). The action of the output shaft lever causes the clockwise rotation of the output shaft (2). This moves the fuel control linkage (15) in the "FUEL ON" direction.
Illustration 12
g00332576
PSG governor installed (2) Output shaft. (15) Fuel control linkage.
The volume of chamber (A) increases as the power piston moves in the direction of the return spring (1). The pressure in chamber (A) decreases. This pulls the oil from the chamber inside the power piston above the buffer piston (11) into chamber (A). When the oil flows out from above the buffer piston (11), the oil fills chamber (A). This causes the buffer piston to move up in the bore of the power piston. Chamber (A) is connected to the chamber above the pilot valve compensation land (10). Chamber (B) is connected to the chamber below the pilot valve compensation land (10). The pressure difference that is felt by the pilot valve compensation land, adds to the axial force of the flyweights and moves the pilot valve up. This closes the control ports. When the flow of pressure oil to chamber (B) stops, the movement of the fuel control linkage stops. Fuel Decrease The pilot valve will move in the direction of the speeder spring (5) when either of the following conditions exist. • The force of compression in the speeder spring decreases (operator decreases desired rpm) • The axial force of the flyweights increases (load on the engine decreases) This opens the control ports (14). Oil from chamber (B) and pressure oil from the pump will dump through the end of the pilot valve bushing. The decreased pressure in chamber (B) will allow the power piston to move in the direction of the drive unit. The return spring (1) pushes against the strut assembly (4). This moves the output shaft lever (3). The action of the output shaft lever causes the counterclockwise rotation of the output shaft (2). This moves the fuel control linkage (15) in the "FUEL OFF" direction.
Illustration 13
g00332577
Earlier PSG governor (6) Power piston. (8) Needle valve. (10) Pilot valve compensating land. (11) Buffer piston. (14) Control ports. (A) Chamber. (B) Chamber.
As power piston (6) moves in the direction of the drive unit the volume of chamber (A) decreases. This pushes the oil in chamber (A) into the chamber above the buffer piston (11). When the oil from chamber (A) flows into the power piston, the oil moves the buffer piston down in the bore of the power piston. The pressure at chamber (A) is more than the pressure at chamber (B). Chamber (A) is connected to the chamber above the pilot valve compensation land (10). Chamber (B) is connected to the chamber below the pilot valve compensation land (10). The pressure difference that is felt by the pilot valve compensation land, adds to the force of the speeder spring and moves the pilot valve down. This closes the control ports. When the flow of pressure oil from chamber (B) stops, the movement of the fuel control linkage stops. Hunting There is a moment between the time the fuel control linkage stops its movement and the time the engine actually stops its increase or decrease of rpm. During this moment, the following two forces are changed on the pilot valve • The pressure difference at the pilot valve compensation land • The axial force of the flyweights The axial force of the flyweights changes until the engine stops its increase or decrease of rpm. The pressure difference at the pilot valve compensation land changes until the buffer piston returns to the original position. A needle valve (8) in a passage between chamber (A) and chamber (B) controls the
rate at which the pressure difference changes. The pressure difference makes compensation for the change in the axial force of the flyweights until the engine stops its increase or decrease of rpm. If the force on the pilot valve compensation land plus the axial force of the flyweights is not is not equal to the force of the speeder spring, the pilot valve will move. This movement is known as hunting. Hunting is the movement of the pilot valve that is not the result of a change in load or desired rpm of the engine. The governor will hunt each time the engine actually stops its increase or decrease of rpm at any other rpm than the rpm that is desired. The governor will hunt more after a rapid or large change of load or desired rpm than after a gradual or small change.
Illustration 14
g00332579
PSG governor installed (typical example) (8) Needle valve.
Speed Adjustment Speed adjustments are made by a 24V DC reversible synchronizing motor (2). The motor is controlled by a switch (1) that can be put in a remote location.
Illustration 15
g00332580
3 wire synchronizing motor shown (1) Switch. (2) Motor.
The synchronizing motor drives the clutch assembly (3). The clutch assembly protects the motor if the motor is run against the adjustment stops. The link assembly (4) is pushed down by the clutch assembly when the clutch assembly is turned clockwise. The force of the compression in the speeder spring (5) is increased. This causes the pilot valve (6) to move down. Refer to "Pilot Valve Operation". The engine will increase speed and the engine will become stabilized at the new desired rpm.
Illustration 16
g00332581
PSG governor (2) Synchronizing motor. (3) Clutch assembly. (4) Link assembly. (5) Speeder spring. (6) Pilot valve.
When the clutch assembly is turned counterclockwise the link assembly moves up. The force of the compression in the speeder spring is decreased. This causes the pilot valve to move up. The engine will decrease speed and the engine will become stabilized at the new desired rpm. Note: If necessary, the clutch assembly can be turned manually.
Speed Droop Speed droop is the difference between no load rpm and full load rpm. This difference in rpm divided by the full load rpm and multiplied by 100 is the percent of speed droop
Illustration 17
g00332582
PSG governor (1) Pivot pin. (2) Bracket for droop adjustment screw. (3) Output shafts.
The speed droop of the PSG governor can be adjusted. The governor is isochronous when adjusted so that the no load and the full load rpm is equal. Speed droop permits load division between two or more engines that drive generators. These generators can be connected in parallel or the generators can be connected to a single shaft. The adjustment of the speed droop on PSG governors is made by the movement of pivot pin (1). When the pivot pin is put in alignment with the output shafts, movement of the output shaft lever will not change the force of the speeder spring. When the force of the speeder spring is kept constant, the desired rpm will be kept constant. Refer to "Pilot Valve Operation". When the pivot pin is moved out of alignment with the output shafts, movement of the output shaft lever will change. The change in
the force of the speeder spring is proportional to the load on the engine. When the force of the speeder spring is changed, the desired rpm of the engine will change. An adjustment lever outside the governor is connected to the pivot pin (1) by link (4). This is used to make an adjustment of the speed droop.
Illustration 18 Later PSG governor (1) Pivot pin. (4) Link.
g00332615
Copyright 1993 - 2014 Caterpillar Inc. Todos los derechos reservados. Red privada para licenciados del SIS.
Fri Feb 14 19:12:53 EST 2014
