Cat 3412 Pump Tecni 1

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Producto: GEN SET ENGINE

Modelo: 3412 GEN SET ENGINE 81Z02545

Configuración: 3412 ENGINE GENERATOR SET 81Z00001-04999

Operación de Sistemas3408B and 3412C Generator Set EnginesNúmero de medio -SENR2562-03 Fecha de publicación -01/03/2001 Fecha de actualización -16/11/2001

i00730076

Fuel SystemSMCS - 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 nozzlefor each cylinder. The injection pumps are in the pump housing (4) on the top front of the engine. Thefuel injection nozzles are located in the fuel injection adapters. The fuel injection adapters are underthe 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 mainfuel filters (14). The fuel then flows to the manifold of the injection pump housing. The fuel in themanifold of the injection pump housing flows to the injection pumps. The injection pumps are in timewith 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 theshock loads that are caused by the injection pumps. Some of the fuel in the fuel manifold is constantlysent 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 throughthe fuel return line (5).


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) Fuelsupply 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 removesair from the low pressure side of the fuel system. The low pressure side of the fuel system consist ofthe fuel filter, the fuel lines and components.


The location of the fuel system components 3412C shown

(1) The fuel inlet line to the injection pump housing. (5) The fuel return line to the tank. (7) Junction block. (8) Fuelpriming pump. (11) Fuel supply line. (14) Main fuel filters. (17) The fuel outlet line from the transfer pump and the inletline to the main filters.

The fuel transfer pump has a bypass valve and a check valve. The bypass valve controls the maximumpressure of the fuel. The extra fuel goes to the inlet of the pump. The check valve allows the fuel fromthe tank to go around the transfer pump gears when the priming pump is used.


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 mainfilter.

Fuel Injection Pump


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 moveup 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 thesame number of pumps on each side.

When the pump plunger moves down, the fuel from the fuel manifold (1) flows through the inletpassage (2). The fuel then fills the chamber that is above the pump plunger (5). When the plungermoves up, the plunger closes the inlet passage.

The pressure of the fuel in the chamber above the plunger increases until the pressure is high enoughto cause the check valve (3) to open. The high pressure fuel flows through the check valve, to theinjection 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 inletpassage (2) is closed. The pressure relief passage (4) will control the amount of time the inlet passageis closed. The amount of time the inlet passage is closed can be changed because of the design of thepassage. 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 theplungers.

The governor is connected to the left rack. The spring load, located on the lever (11), removes theplay between the racks and the link (10). The fuel racks are connected by the link (10). The fuel racksmove in opposite directions. When one rack moves in, the other rack moves out.

Fuel Injection Valves And NozzlesThe injection valves are located within the fuel injection adapters. The fuel injection adapters areinstalled in the cylinder head.

The fuel injection pump sends fuel with high pressure to the fuel injection valves. The fuel injectionvalves change the fuel to the correct spray pattern for good combustion in the cylinders. The fuelinjection valves will not open until a very high pressure is reached. Once this pressure is reached, thefuel injection valves open quickly. The fuel is released directly into the engine cylinder through sixorifices in the tip of each nozzle.

Hydramechanical Governor With DashpotThe governor controls the amount of fuel that is needed by the engine to maintain a desired rpm. Thegovernor maintains a constant rpm for variable engine loads.

When the engine is operating, the balance between the centrifugal force of the governor weights andthe force of the governor control on the governor spring, controls the movement of a valve andindirectly, the fuel rack. The valve directs pressure oil to either side of a rack positioning piston. Theposition of the valve controls the rack. The amount of fuel to the engine is controlled by the rack andload conditions.


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 areconnected to one fuel rack through pin (12) and lever (13) .

The governor control is connected to the governor control lever. The governor control controls thecompression 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 theengine. When these two forces are in balance, the engine runs at a constant rpm.


(A) Pressure oil. (7) Governor spring. (8) Governor weights. (9) Valve. (10) Cylinder. (12) Pin. (14) The oil drainpassage 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 sendsengine 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 ofthe 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 drainpassage (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) andpin (12). This gives more fuel to the engine. Engine rpm increases until the rotation of the governorweights is fast enough to be in balance with the force of the governor spring.


(A) Pressure oil. (B) Drain oil. (7) Governor spring. (8) Governor weights. (9) Valve. (10) Cylinder. (12) Pin. (14) Theoil drain passage for the piston. (15) The upper oil passage in the piston. (16) Piston. (17) The lower oil passage in thepiston. (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 therotation of the governor weights (8) will increase. This will move valve (9) to a higher position. Thisstops 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 pistonand pin (12) to a higher position. This causes a reduction in the amount of fuel to the engine. Theengine rpm decreases until the centrifugal force of the governor weights is in balance with the force ofthe 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 contactwith 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 theshoulder 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 theshutoff 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 oilthat is thrown by other parts. The oil flows from the governor to the housing for the fuel injectionpumps.

Electric set engines need a governor that has better control over the engine speed range. A standardhydramechanical governor can not provide this function. The following parts are added to the basichydramechanical 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 moreprecise movement of the governor spring seat. This allows the governor to accurately control theengine speed.

Side View Of The Governor


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 oiloverflow that sends the oil back to the mechanical area of the governor. Too much oil flow to thereservoir will fill the governor with oil. This will decrease the engine performance. Too little oil flowdoes not give enough oil to the reservoir. The decrease in oil will cause the governor to hunt (increaseand 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 tomove faster. This will allow the governor to hunt. Too little oil flow causes a slower action by thegovernor.

Automatic Timing Advance Unit


Automatic timing advance unit

(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 injectionpump. The timing gears drive the automatic timing advance unit. The drive gear (5) for the fuelinjection 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 advanceare 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), theguides 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 isalso changed.

The unit advances the fuel injection pump camshaft 2% between approximately low idle and 1100rpm. No adjustment can be made in the advance unit.

Woodward PSG Governors


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 isochronousgovernor 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 locatedinside 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 shaftturns 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 ballheadcauses the flyweights to pivot out. This action of the flyweights changes the centrifugal force to axialforce against the speeder spring (5). There is a thrust bearing (9) between the toes of the flyweightsand 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 thespeeder spring.

The engine is at the governed rpm when the axial force of the flyweights is equal to the force of thecompression 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 conditionsexist.

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). Theincreased pressure in the chamber (B) causes the power piston (6) to move. The power piston pushesthe strut assembly (4), which is connected to the output shaft lever (3). The action of the output shaftlever causes the clockwise rotation of the output shaft (2). This moves the fuel control linkage (15) inthe "FUEL ON" direction.


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 powerpiston above the buffer piston (11) into chamber (A). When the oil flows out from above the bufferpiston (11), the oil fills chamber (A). This causes the buffer piston to move up in the bore of thepower 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 pressuredifference that is felt by the pilot valve compensation land, adds to the axial force of the flyweightsand 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 followingconditions 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 dumpthrough the end of the pilot valve bushing. The decreased pressure in chamber (B) will allow thepower piston to move in the direction of the drive unit. The return spring (1) pushes against the strutassembly (4). This moves the output shaft lever (3). The action of the output shaft lever causes thecounterclockwise rotation of the output shaft (2). This moves the fuel control linkage (15) in the"FUEL OFF" direction.


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 fromchamber (A) flows into the power piston, the oil moves the buffer piston down in the bore of thepower piston. The pressure at chamber (A) is more than the pressure at chamber (B). Chamber (A) isconnected to the chamber above the pilot valve compensation land (10). Chamber (B) is connected tothe chamber below the pilot valve compensation land (10). The pressure difference that is felt by thepilot valve compensation land, adds to the force of the speeder spring and moves the pilot valvedown. This closes the control ports. When the flow of pressure oil from chamber (B) stops, themovement of the fuel control linkage stops.

Hunting

There is a moment between the time the fuel control linkage stops its movement and the time theengine actually stops its increase or decrease of rpm. During this moment, the following two forcesare 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. Thepressure difference at the pilot valve compensation land changes until the buffer piston returns to theoriginal 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 thechange in the axial force of the flyweights until the engine stops its increase or decrease of rpm. If theforce on the pilot valve compensation land plus the axial force of the flyweights is not is not equal tothe 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 ofthe engine.

The governor will hunt each time the engine actually stops its increase or decrease of rpm at any otherrpm than the rpm that is desired. The governor will hunt more after a rapid or large change of load ordesired rpm than after a gradual or small change.


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 controlledby a switch (1) that can be put in a remote location.


3 wire synchronizing motor shown

(1) Switch. (2) Motor.

The synchronizing motor drives the clutch assembly (3). The clutch assembly protects the motor if themotor is run against the adjustment stops. The link assembly (4) is pushed down by the clutchassembly when the clutch assembly is turned clockwise. The force of the compression in the speederspring (5) is increased. This causes the pilot valve (6) to move down. Refer to "Pilot ValveOperation". The engine will increase speed and the engine will become stabilized at the new desiredrpm.


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 thecompression in the speeder spring is decreased. This causes the pilot valve to move up. The enginewill 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 dividedby the full load rpm and multiplied by 100 is the percent of speed droop


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 sothat the no load and the full load rpm is equal. Speed droop permits load division between two ormore engines that drive generators. These generators can be connected in parallel or the generatorscan 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 willnot change the force of the speeder spring. When the force of the speeder spring is kept constant, thedesired rpm will be kept constant. Refer to "Pilot Valve Operation". When the pivot pin is moved outof 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 speederspring 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 tomake an adjustment of the speed droop.


Later PSG governor

(1) Pivot pin. (4) Link.

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Fri Feb 14 19:12:53 EST 2014

Cat 3412 Pump Tecni 1

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