fuel pumps and valves
Fuel pump MAN B&W
Fuel Pump description
Fuel pump timing
MAN B&W Fuel Pump - VIT
Construction and functioning of slide type fuel valve
Removal of seized fuel injector
Pressure testing of slide-type valve
Overhauling of slide-type valve
Auxiliary Engine Fuel Injector
Related article: Fuel Injection system
Two bores are provided in the base for toothed racks. The upper rack serves to adjust the injection timing via the timing guide, and the lower rack controls the quantity of fuel oil delivered by the pump via the regulating guide. At the top, the pump housing is closed by a top cover, which incorporates a combined puncture valve and suction valve. The cover is attached by means of nuts and studs fitted in the pump housing. A sealing ring is fitted in the lower part of the top cover, to seal between barrel and top cover.
Oil is supplied through a flanged connection on the front of the pump housing. A corresponding flange on the back of the housing is fitted with a shock absorber which neutralizes the shock caused when the plunger uncovers the cut-off holes at the end of each delivery stroke.
The shock absorber consists of a cylinder with a spring-loaded plunger which is pressed back when the surplus oil from the delivery chamber is forced out into the inlet space round the pump barrel.
Two plug screws are fitted in the pump housing opposite the cut-off holes of the barrel.
The oil jets which are ejected through the cut-off holes at the end of the delivery stroke, hit the plug screws, which can be replaced when they are eroded.
A guide pin fitted at the top of the pump housing ensures correct positioning of the parts.
Pump Barrel and Timing Guide
The pump barrel is guided at the top and bottom of the pump housing. Three low-friction sealing rings are fitted in grooves in the barrel to seal between barrel and housing. The barrel is provided with a drain bore between the two sealing rings in the lower end.
The pump barrel has a threaded lower end which fits into the internal threads of the timing guide.
The timing guide has a gear rim to mesh with the upper toothed rack at the base of the pump housing. The gear rim and toothed rack are marked with lines enabling the parts to be positioned correctly after disassembly.
The toothed rack is linked to a servo-air cylinder which is controlled by the position of the regulating shaft. The position of the upper toothed rack determines the vertical position of the barrel relative to the plunger through the threaded connection.
In this manner, the initial moment of fuel oil injection into the cylinder can be adjusted by a servo-air cylinder. The pump barrel is prevented from turning by means of a guide screw mounted on the front of the pump housing.
Pump Plunger and Regulating Guide
The pump plunger is fitted within the barrel and ground accurately to form an oil-tight seal. Barrel and plunger must always go together and cannot be replaced individually. During the travel of the plunger, cut-off holes in the barrel are covered and uncovered.
This function, in conjunction with the turning of the plunger effected by the regulating gear, serves to regulate the amount of oil injected into the engine cylinder.
The pump plunger is provided with a guide block designed to travel in the milled keyway in the regulating guide. At the bottom it has a foot which rests on a thrust disc in the bayonet joint at the roller guide neck. A clearance of approx. 0.1 mm between the plunger foot and the roller guide permits the plunger to turn in the roller guide.
The regulating guide has a gear rim that engages with the lower toothed rack at the base of the pump housing. The gear rim and toothed rack are marked with lines enabling the parts to be positioned correctly after disassembly. The toothed rack is linked together with the regulating gear of the engine through a spring-loaded connection. Thus, in the event of a sticking pump plunger, the regulating gear for the remaining fuel pumps will not be blocked.
Puncture Valve
A puncture valve is fitted in the top cover of the pump. The puncture valve consists of a piston that communicates with the control air system of the engine. In the event of actuation of the shut-down system, or the "Fuel Oil Leakage Alarm System", (option) or when STOP is activated, compressed air is supplied to the top of the piston, causing the piston to be pressed downwards and puncture the oil flow to the fuel valve. As long as the puncture valve is activated, the fuel oil is returned through bores to the pump housing, and no injection takes place.
Fuel Oil System
The fuel oil is supplied through a pipe on the front of the pump housing from the electrically driven circulating pump. The oil pressure is kept constant by means of the overflow valve, which is located between the main fuel oil supply line to the pumps and the return line. The fuel pump and the fuel valves are designed for the circulation of warm oil, enabling them to be preheated during standstill and in between the fuel oil injections.
Fuel Oil Injection
During the suction stroke, the spring-loaded suction valve opens and the delivery chamber is filled with oil. As soon as the plunger has covered the cut-off holes in the pump barrel during its upward movement, injection commences through the fuel valves. The vertical position of the cut-off holes thus controls the injection timing. The injection will last until the cut-off holes are uncovered by the oblique cut-off edges, following which the oil is forced through and out through the cut-off holes of the barrel during the rest of the delivery stroke.
Fuel Pump Actuating Gear
A roller guide housing containing the fuel pump, the exhaust valve actuating gear and the indicator drive, is bolted onto the side of the cylinder frame. On reversible engines, the roller guide for each fuel pump incorporates an angularly displaceable reversing link. The fuel pump is actuated by a cam on the camshaft. The movement is transmitted through the roller guide to the plunger in the barrel of the pump housing which through the high-pressure pipes is connected with the fuel valves on the cylinder cover.
The roller guide is forced downwards by the action of a helical spring fixed between the roller guide and the pump base so that the roller of the roller guide follows the cam on the camshaft. The pump base is attached to the camshaft housing by four studs.
The thread on two of these is long enough to permit the gradual easing of the roller guide spring when dismantling the components.
The plunger rests on a thrust piece in the neck of the roller guide and is locked to the roller guide by a bayonet lock. The roller guide itself is prevented from turning by means of a guide block mounted in the liner of the housing. The top of the roller guide neck is located inside the pump base and is equipped with a cap. This cap, together with a sealing bush that is shrunk into the pump base, form a labyrinth to prevent fuel oil from entering the camshaft lube oil.
Each roller guide housing is provided with a lifting device that can lift the fuel pump roller guide roller free of the fuel cam. The lifting device is mounted on the side of the roller guide housing.
Reversing mechanism
Reversing is achieved by shifting the roller in the fuel pump drive mechanism at each cylinder. The link connecting the roller guide and roller is provided with a reversing arm, and a pivot is mounted at the top end of the reversing arm. The pivot travels in a reversing guide connected to an air cylinder. The link is self-locking in either the AHEAD or ASTERN position without the aid of external forces. Each cylinder is reversed individually, and the reversing mechanism is activated by compressed air.
Fuel Oil High-Pressure Pipes
All high-pressure pipes in the system are provided with flexible, steel wire-armoured hoses or a protective outer pipe. The space between the pipe and the protective hose communicates, through drilled passages in the flanges, with a drain bore in the pump top cover.
Fuel Oil Leakage Alarm (Required for Unattended Machinery Spaces, UMS)
Alternative 1:
Each fuel pump is, via drain pipes, connected to a common drain tank, which incorporates a level switch. The drain tank is also equipped with an overflow pipe, which has a small drain bore below, whereby oil from small leakages can be drained to the outlet, without actuating the level switch.
In the event of pipe fractures or major leakages in the system, the aforementioned bore will not be large enough to allow the increased oil quantity to pass, and the oil level in the drain tank will rise until it reaches the level of the overflow pipe. The rising oil level will cause the level switch to actuate an alarm.
Alternative 2:
The drain pipes of each fuel pump are connected to a diaphragm valve, which sets off an alarm and activates the puncture valve in order to stop the fuel oil flow from the pertaining cylinder.
Alternative 3:
The drain pipes of each fuel pump are connected to a diaphragm valve, which sets off an alarm and activates the automatic lifting arrangement for the fuel roller guide, in order to stop the fuel oil flow from the pertaining pump.
To check the fuel injection timing shut the fuel inlet valve.
Turn the engine and ensure that the fuel pump roller rests on the base circle of the cam.
At this position, the plunger will be at the lowest position.
Disconnect the high-pressure discharge pipe.
Remove the delivery valve.
Fit a gooseneck pipe to the pump discharge.
Open the fuel inlet and release the fuel into the pump. The fuel runs through the pump body and flows out through gooseneck pipe.
Turn the camshaft slowly by turning the engine.
The plunger moves upward inside the barrel.
When the plunger covers the suction port, oil flow stops and fuel injection starts.
Note the marking on the flywheel, which corresponds to crank angle in degree before TDC. This will be the fuel injection time of that cylinder.
Adjustment: The fuel injection timing depends on the fuel pump lead.
Before adjusting the lead, isolate the fuel oil system by closing the inlet and return valves.
Check if the roller is resting on the base circle of the cam.
Measure the distance between the upper edge of roller guide housing and top of thrust piece, using a depth gauge.
Compare the reading with the prescribed value in the manufacturer's manual.
To adjust the fuel pump lead, remove the thrust piece using a special extraction tool.
Add shims of required thickness to advance or remove the shims already available to retard the timing.
Use a mallet to mount the thrust piece in the slot.
Measure the lead once again.
Run the engine on full load and check the combustion pressure.
Conventional V.I.T System:-
i) plunger with the oblique cut profile.
ii) Plunger without oblique cut profile.
point 'A' at 78% load and point 'B' at 100% load. It is mechanism for varying the ignition timing used on smaller B&W engine. Here the pump plunger is profiled i.e it has extra oblique cut.
Super V.I.T System:-
Used in large MAN & B&W engine. This mechanism automatically adjusts the commencement of fuel injection, such that at the MCR Pmax is Kept constant as the engine load is reduced from 100% down to pre-specified part load.
Fuel Pump description
Fuel pump timing
MAN B&W Fuel Pump - VIT
Construction and functioning of slide type fuel valve
Removal of seized fuel injector
Pressure testing of slide-type valve
Overhauling of slide-type valve
Auxiliary Engine Fuel Injector
Related article: Fuel Injection system
Fuel pump MAN B&W
Fuel Pump description
Each engine cylinder is equipped with its own VIT (Variable Injection Timing) fuel pump, which is mounted on the roller guide housing over the camshaft section corresponding to the cylinder concerned. The square base of the fuel pump housing is provided with a groove to receive any leaking oil, which is subsequently drained off through a drain pipe.Two bores are provided in the base for toothed racks. The upper rack serves to adjust the injection timing via the timing guide, and the lower rack controls the quantity of fuel oil delivered by the pump via the regulating guide. At the top, the pump housing is closed by a top cover, which incorporates a combined puncture valve and suction valve. The cover is attached by means of nuts and studs fitted in the pump housing. A sealing ring is fitted in the lower part of the top cover, to seal between barrel and top cover.
Oil is supplied through a flanged connection on the front of the pump housing. A corresponding flange on the back of the housing is fitted with a shock absorber which neutralizes the shock caused when the plunger uncovers the cut-off holes at the end of each delivery stroke.
The shock absorber consists of a cylinder with a spring-loaded plunger which is pressed back when the surplus oil from the delivery chamber is forced out into the inlet space round the pump barrel.
Two plug screws are fitted in the pump housing opposite the cut-off holes of the barrel.
The oil jets which are ejected through the cut-off holes at the end of the delivery stroke, hit the plug screws, which can be replaced when they are eroded.
A guide pin fitted at the top of the pump housing ensures correct positioning of the parts.
Pump Barrel and Timing Guide
The pump barrel is guided at the top and bottom of the pump housing. Three low-friction sealing rings are fitted in grooves in the barrel to seal between barrel and housing. The barrel is provided with a drain bore between the two sealing rings in the lower end.
The pump barrel has a threaded lower end which fits into the internal threads of the timing guide.
The timing guide has a gear rim to mesh with the upper toothed rack at the base of the pump housing. The gear rim and toothed rack are marked with lines enabling the parts to be positioned correctly after disassembly.
The toothed rack is linked to a servo-air cylinder which is controlled by the position of the regulating shaft. The position of the upper toothed rack determines the vertical position of the barrel relative to the plunger through the threaded connection.
In this manner, the initial moment of fuel oil injection into the cylinder can be adjusted by a servo-air cylinder. The pump barrel is prevented from turning by means of a guide screw mounted on the front of the pump housing.
Pump Plunger and Regulating Guide
The pump plunger is fitted within the barrel and ground accurately to form an oil-tight seal. Barrel and plunger must always go together and cannot be replaced individually. During the travel of the plunger, cut-off holes in the barrel are covered and uncovered.
This function, in conjunction with the turning of the plunger effected by the regulating gear, serves to regulate the amount of oil injected into the engine cylinder.
The pump plunger is provided with a guide block designed to travel in the milled keyway in the regulating guide. At the bottom it has a foot which rests on a thrust disc in the bayonet joint at the roller guide neck. A clearance of approx. 0.1 mm between the plunger foot and the roller guide permits the plunger to turn in the roller guide.
The regulating guide has a gear rim that engages with the lower toothed rack at the base of the pump housing. The gear rim and toothed rack are marked with lines enabling the parts to be positioned correctly after disassembly. The toothed rack is linked together with the regulating gear of the engine through a spring-loaded connection. Thus, in the event of a sticking pump plunger, the regulating gear for the remaining fuel pumps will not be blocked.
Puncture Valve
A puncture valve is fitted in the top cover of the pump. The puncture valve consists of a piston that communicates with the control air system of the engine. In the event of actuation of the shut-down system, or the "Fuel Oil Leakage Alarm System", (option) or when STOP is activated, compressed air is supplied to the top of the piston, causing the piston to be pressed downwards and puncture the oil flow to the fuel valve. As long as the puncture valve is activated, the fuel oil is returned through bores to the pump housing, and no injection takes place.
Fuel Oil System
The fuel oil is supplied through a pipe on the front of the pump housing from the electrically driven circulating pump. The oil pressure is kept constant by means of the overflow valve, which is located between the main fuel oil supply line to the pumps and the return line. The fuel pump and the fuel valves are designed for the circulation of warm oil, enabling them to be preheated during standstill and in between the fuel oil injections.
Fuel Oil Injection
During the suction stroke, the spring-loaded suction valve opens and the delivery chamber is filled with oil. As soon as the plunger has covered the cut-off holes in the pump barrel during its upward movement, injection commences through the fuel valves. The vertical position of the cut-off holes thus controls the injection timing. The injection will last until the cut-off holes are uncovered by the oblique cut-off edges, following which the oil is forced through and out through the cut-off holes of the barrel during the rest of the delivery stroke.
Fuel Pump Actuating Gear
A roller guide housing containing the fuel pump, the exhaust valve actuating gear and the indicator drive, is bolted onto the side of the cylinder frame. On reversible engines, the roller guide for each fuel pump incorporates an angularly displaceable reversing link. The fuel pump is actuated by a cam on the camshaft. The movement is transmitted through the roller guide to the plunger in the barrel of the pump housing which through the high-pressure pipes is connected with the fuel valves on the cylinder cover.
The roller guide is forced downwards by the action of a helical spring fixed between the roller guide and the pump base so that the roller of the roller guide follows the cam on the camshaft. The pump base is attached to the camshaft housing by four studs.
The thread on two of these is long enough to permit the gradual easing of the roller guide spring when dismantling the components.
The plunger rests on a thrust piece in the neck of the roller guide and is locked to the roller guide by a bayonet lock. The roller guide itself is prevented from turning by means of a guide block mounted in the liner of the housing. The top of the roller guide neck is located inside the pump base and is equipped with a cap. This cap, together with a sealing bush that is shrunk into the pump base, form a labyrinth to prevent fuel oil from entering the camshaft lube oil.
Each roller guide housing is provided with a lifting device that can lift the fuel pump roller guide roller free of the fuel cam. The lifting device is mounted on the side of the roller guide housing.
Reversing mechanism
Reversing is achieved by shifting the roller in the fuel pump drive mechanism at each cylinder. The link connecting the roller guide and roller is provided with a reversing arm, and a pivot is mounted at the top end of the reversing arm. The pivot travels in a reversing guide connected to an air cylinder. The link is self-locking in either the AHEAD or ASTERN position without the aid of external forces. Each cylinder is reversed individually, and the reversing mechanism is activated by compressed air.
Fuel Oil High-Pressure Pipes
All high-pressure pipes in the system are provided with flexible, steel wire-armoured hoses or a protective outer pipe. The space between the pipe and the protective hose communicates, through drilled passages in the flanges, with a drain bore in the pump top cover.
Fuel Oil Leakage Alarm (Required for Unattended Machinery Spaces, UMS)
Alternative 1:
Each fuel pump is, via drain pipes, connected to a common drain tank, which incorporates a level switch. The drain tank is also equipped with an overflow pipe, which has a small drain bore below, whereby oil from small leakages can be drained to the outlet, without actuating the level switch.
In the event of pipe fractures or major leakages in the system, the aforementioned bore will not be large enough to allow the increased oil quantity to pass, and the oil level in the drain tank will rise until it reaches the level of the overflow pipe. The rising oil level will cause the level switch to actuate an alarm.
Alternative 2:
The drain pipes of each fuel pump are connected to a diaphragm valve, which sets off an alarm and activates the puncture valve in order to stop the fuel oil flow from the pertaining cylinder.
Alternative 3:
The drain pipes of each fuel pump are connected to a diaphragm valve, which sets off an alarm and activates the automatic lifting arrangement for the fuel roller guide, in order to stop the fuel oil flow from the pertaining pump.
Fuel pump timing
Injection of fuel starts when the top of the fuel pump plunger covers the suction port.To check the fuel injection timing shut the fuel inlet valve.
Turn the engine and ensure that the fuel pump roller rests on the base circle of the cam.
At this position, the plunger will be at the lowest position.
Disconnect the high-pressure discharge pipe.
Remove the delivery valve.
Fit a gooseneck pipe to the pump discharge.
Open the fuel inlet and release the fuel into the pump. The fuel runs through the pump body and flows out through gooseneck pipe.
Turn the camshaft slowly by turning the engine.
The plunger moves upward inside the barrel.
When the plunger covers the suction port, oil flow stops and fuel injection starts.
Note the marking on the flywheel, which corresponds to crank angle in degree before TDC. This will be the fuel injection time of that cylinder.
Adjustment: The fuel injection timing depends on the fuel pump lead.
Before adjusting the lead, isolate the fuel oil system by closing the inlet and return valves.
Check if the roller is resting on the base circle of the cam.
Measure the distance between the upper edge of roller guide housing and top of thrust piece, using a depth gauge.
Compare the reading with the prescribed value in the manufacturer's manual.
To adjust the fuel pump lead, remove the thrust piece using a special extraction tool.
Add shims of required thickness to advance or remove the shims already available to retard the timing.
Use a mallet to mount the thrust piece in the slot.
Measure the lead once again.
Run the engine on full load and check the combustion pressure.
MAN B&W Fuel Pump - VIT
V.I.T Fuel pump [Man B&W] variable injection timing was developed to fulfil the requirement of maintaining the maximum continuous rating Pmax under part-load conditions, in order to improve thermal efficiency and to save fuel.Conventional V.I.T System:-
i) plunger with the oblique cut profile.
ii) Plunger without oblique cut profile.
point 'A' at 78% load and point 'B' at 100% load. It is mechanism for varying the ignition timing used on smaller B&W engine. Here the pump plunger is profiled i.e it has extra oblique cut.
Super V.I.T System:-
Used in large MAN & B&W engine. This mechanism automatically adjusts the commencement of fuel injection, such that at the MCR Pmax is Kept constant as the engine load is reduced from 100% down to pre-specified part load.
The pump barrel is moved up and down (relative to the plunger) by means of a Rack and Pinion in combination with a double threaded fuel pump with helix and ports controlling the fuel quantity can have the timing of injection advanced by lowering the pump barrel relative to highest and lowest points of the plunger movement.
The movement of the plunger is controlled by the fuel pump cam and return spring. Commencement of injection occurs when the plunger moves upward and closes off the inlet and spill ports.
If the pump barrel is lowered, injection commences earlier as inlet and spill ports are cut off earlier.
- When it is required to retard the injection period, the pump barrel is raised.
- The fuel cam is used to adjust the timing of the beginning of injection as normal.
Pmax adjustment:
1. The Maximum Combustion Pressure (Pmax) is adjusted for the individual units at the fuel pump VIT index arm.
2. Loosen lock nut B and then turn to adjust screw H. The link can be adjusted by approx. 3 index marks.
3. To increase Pmax, adjust to a higher VIT index (advance injection).
To decrease Pmax, adjust to a lower VIT index (delay injection).
Change of 1 index mark, corresponds to Pmax being altered approx. 3-4 bar.
The individual Pmax value must not deviate more than 3 bar from the average value for all cylinders.
The complete spindle guide consists of a spindle guide, thrust piece and spindle with a cut-off slide. The spindle guide is assembled with a press fit. The spindle is pressed against the tapered valve seat of the spindle guide by the action of the thrust spring, the spring pressure is transmitted through the slotted thrust foot. The thrust spring determines the opening pressure of the valve.
Optionally, an extra disc can be inserted to raise the opening pressure by 30 bar.
The non-return valve consists of housing, thrust piece, slide and spring. The nonreturn valve is assembled with a press fit.
The slide is pressed by the spring against the tapered valve seat inside the non-return valve. In this position, the head of the slide uncovers a small bore arranged for circulation purposes in a thrust piece.
The functioning of the fuel valve is as follows:
Position I:
The electrical fuel oil circulating pump circulates preheated oil through the fuel pump and fuel valve. In the fuel valve the oil passes through the central bore of the valve head and continues to the thrust piece of the non-return valve, leaving through the circulation bore of the latter. Thence the oil is passed through the interior of the valve body to an outlet pipe on the side of the valve head.
The space round the tapered valve seat of the spindle is also filled with oil, but the circulating pump pressure is insufficient to overcome the force of the spring and lift the spindle.
If, for some reason, valve spindle, spindle/cut-off slide should not close during engine standstill, then the closed spindle in the non-return valve will prevent the circulating pump from pressing oil through the nozzle, and thus obviate the risk of the engine cylinder being filled with oil.
Position II:
When, at the beginning of the delivery stroke, the pressure has risen to about 10 bar, the force of the spring in the non-return valve will be overcome and spindle pressed back against the shoulder of thrust piece. Position III:
When the spindle in the non-return valve is pressed upwards, the circulation bore of the thrust piece is closed, and the oil passes the seat of the spindle and enters the space round valve spindle seat in spindle guide. When the pressure has risen to the preset opening value of the fuel valve, the spindle is lifted, and oil is forced through the nozzle into the engine cylinder.
At the termination of the delivery stroke, first the valve spindle and then the spindle in the non-return valve will be pressed against their respective seats, the injection of fuel stops, and oil is again circulated through the valve (position-I).
A. Use of special Tool
A special tool is provided by the manufacturer to draw a sticky injector out of pocket shown in the figure. Remove the nuts but not completely out and fix the tool as shown in diagram. The tool is constructed in such a way that a long lever provided in the tool transmits a high torque which pushes the injector out of body. Sometime a little tapping by hammer assist in the job.
In case the injector is still stuck, a rag soaked with release oil to be rapped around the injector. The oil will seep into the clearance and dissolve the hard cake, it should be left there for some time. Now the process of extracting with special tool can be repeated, with a little hammer tapping. As the injector is loose, now the nuts can be removed compeletely and so the injector.
B. Cooling the injector:
Metals property of expanding with increasing temperature and contracting by cooling is useful when clearance between the mating surfaces is negligible.
Using a release oil and forcing the injector out if failed, the injector can be cooled by using ice. Use a cylindrical dam or a small piece of pipe to keep ice around the injector. Let the injector get cooled for sufficient time. Now the process of extracting the injector by using special tool should be applied.
C. Pulling by using chain block:This is a dangerous process require high level of safety to be followed. Slig wire and chain block is used and arranged as shown in diagram. The may also require assistance of the tool. Take care that the pulling should be in the direction in the axis of injector, Nuts should not be taken out completely before injector is loose.
Fuel valve tightening torque 25 Nm
Inlet seat, max. diameter 18 mm
Fuel valve weight 8 kg
Safety precautions:-
Stopped engine
Shut off starting air supply – At starting air receiver
Block the main starting valve
Shut off starting air distributor/distributing system supply
Shut off safety air supply – Not ME engines
Shut off control air supply
Shut off air supply to exhaust valve – Only with stopped lubricating oil pumps
Engage turning gear
Shut off cooling water
Shut off fuel oil
Stop lubricating oil supply
Lock the turbocharger rotors
The fuel valves must be given the utmost attention and care, as the greater part of irregularities that may occur during the running of the engine can be attributed to defects in these valves.
If the engine gives normal performance in accordance with diagrams and exhaust temperatures, it is only necessary to inspect the fuel valves after the service period stated in the Checking and Maintenance Schedules.
In order to obtain reliable results during testing of the fuel valves, all fuel valves that are dismantled from the engine must be disassembled, cleaned, inspected and re-assembled befire testing.
"In the event that the slide-type fuel valve is pressure tested without being cleaned between the fuel nozzle and the cut-off slide, the opening pressure value measuered might be considerably lower than specified."
All fuel valves must be function-tested before being mounted in the cylinder cover.
1. Pressure testing pump
If an air supply of 10 bar is not available, working air of 7 bar can be used.
Prescribed oil: Hydraulic oil (rust-preventing) with a viscosity of between 7 and 10 cSt at 50°C.
2. Setting-up the fuel valve
Place the fuel valve in the test rig and secure it with the tubular spacers and nuts. Tighten the nuts to the torque stated in Data.
Mount the oil pipe between the pressure testing pump and the fuel valve.
3. Pressure testing procedure
The subsequent items must be followed in the sequence stated. Items 4, 6, 7 and 8 are each divided into the following four subitems:
A. Objective
B. Procedure
C. Acceptance criteria
D. Cause of fault.
4. Flushing and jet control
A. Objective: To remove air in the system and check the fuel jet.
B. Procedure: The control handle must be in the OPEN position. Slowly increase the working pressure until straight jets of oil are ejected from the nozzle holes (no atomization).
C. Acceptance criteria: There is to be a continuous jet of oil through at least one of the nozzle holes. Owing to the geometry of the internal part of the nozzle – and because the height to which the spindle is lifted during pressure testing is lower than the height it is lifted during normal engine operation – the fuel oil will not necessarily flow from all of the nozzle holes.
D. Cause of fault: If the above point C is not fulfilled, the cause may be:
• Dirt in the nozzle holes.
• The nozzle is not mounted correctly.
5. Atomization test
Do NOT attempt to carry out an atomization test on slide type fuel valves, as this may damage the cut-off slide and nozzle.
The reason is that the atomization test may damage the valve because it makes the needle oscillate, with a small lift at a very high frequency. The high pressure drop across the cut-off edge and the high contact pressure between slide and fuel nozzle, in combination with the poor lubricity of the test oil, increase the risk of seizures between cut-off slide and nozzle.
All of these conditions involve the risk of seizure between the cut-off slide and the nozzle.
6. Opening pressure.
A. Objective: To check the opening pressure.
B. Procedure: The control handle is to be in the OPEN position. Increase the oil pressure until oil is admitted through the nozzle holes.
C. Acceptance criteria: Check the opening pressure on the pressure gauge.
D. Cause of fault: If the opening pressure is higher than specified, the cause may be that a wrong type of spring is used – replace the spring on the thrust spindle, if necessary, replace the complete thrust spindle.
If the opening pressure is lower than specified, the cause may be that the spring has sagged – replace the spring, or add a special thin disc.
If a spring or a disc has been changed, the pressure testing procedure of the fuel valve must be repeated from step 4. 7. Sealing test and sliding function A. Objective: To check the needle valve seat for tightness and the slide for correct closing. B. Procedure: The control handle must be in the OPEN position. Slowly increase the oil pressure to about 50 bar below the opening pressure. Maintain the built-up pressure by moving the control handle into the CLOSED position. Repeat the procedure two or three times. C. Acceptance criteria: Oil must not flow from the nozzle holes. The pressure drops relatively slowly to about 15 bar, after which it drops quickly to 0 (the slide is pressed against the conical seat and opens for circulation oil). Oil flows out of the leak oil outlet when the fuel valve is full of oil.
D. Cause of fault:
D.1 Sealing test
If oil flows out of the nozzle holes, the cause is either:
• Defective spindle guide at needle seat, or a sticking spindle. Examine and/or replace the spindle guide.
• Too quick pressure drop:
– the clearances of the movable parts, both of the spindle guide and of the nonreturn valve, are too large, or – the seats between the thrust piece/ spindle in the spindle guide or thrust piece/valve slide in the non-return valve are damaged.
Examine and/or replace both the spindle guide and non-return valve.
D.2 Sliding function
The pressure drops relatively slowly to about 15 bar, after which it drops quickly to 0 (the slide is pressed against the conical seat and opens for circulation oil).There will always be an oil flow from the leak oil outlet when the fuel valve is full of oil.
If a quick pressure drop from 15 to 0 bar cannot be registered:
• The valve slide is sticking; or
• the vent hole in the thrust piece is blocked.
If so, disassemble and examine the spindle guide, replace if necessary.
8. Pressure test, O-ring sealings
A. Objective: To ensure that the leak oil (circulation oil) remains in the closed system. B. Procedure: The control handle is to be in the OPEN position. Build up a working pressure of about max. 10 bar until oil flows out of the leak oil outlet.
C. Acceptance criteria: Close the leak oil outlet with a gasket and plug screw. Increase the working pressure to about 100 bar. Move the control handle to the CLOSED position. The built-up pressure of about 100 bar should be maintained. D. Cause of fault: If oil leaks out at the union nut, the O-ring inside the fuel valve head is defective, and must be replaced.
1. Close the fuel oil inlet and outlet valves. Dismantle the high-pressure pipe. Disconnect the return oil pipe from the fuel valve.
2. Remove the nuts and the tubular spacers.
3. Take out the valve. If the valve is sticking, use the fuel valve dismantling tool to pull the valve clear of the top cover. If the valve is not to be overhauled immediately, the valve should be immersed in diesel oil until overhauling.
When fuel valves are overhauled, all parts should be handled carefully and be kept clean. Use only clean, non-fluffy rags for wiping purposes. Make sure to remove all liquid or solid impurities.
Whenever fuel valves are overhauled, all sealing rings should be discarded and replaced by new, faultless sealing rings before reassembly.
1. Measure the length of the protruding part of the nozzle, and write down the result for correct re-assembling of the valve.
2. Place the valve holder in a machine vice, mount the fuel valve in the holder and fit the valve with the guide disc from the grinding tool.
3. Compress the fuel valve and the spring inside, by means of a drilling machine, to avoid seizures in the union thread. Hold the fuel valve compressed and unscrew the union nut with a hook spanner. Remove the valve from the valve holder.
4. Pull the valve head clear of the valve housing.
Remove the:
• Non return valve
• Thrust spindle parts
• Thrust foot
• Spindle guide and fuel nozzle from the valve housing.
Remove and discard all the O-rings.
5. Carefully clean and examine all surfaces of the:
• Fuel valve housing
• Fuel valve head
• Thrust spindle
If necessary, grind the seating surfaces by means of the grinding mandrels and a fine-grain abrasive (such as Carborundum No. 500).
This grinding must only be carried out manually. After the grinding, wash the parts in gas oil and blow clean by means of compressed air to remove any remains of the grinding compound. In the event of more serious damage to the seating surface for the high-pressure pipe in the valve head, the milling tool can be used.
Normally, the milling tool is turned by hand, but it may be fitted in the chuck of a column type drilling machine provided that the number of revolutions is kept at a minimum (not exceeding approx. 100 r/min). An ample supply of cutting emulsion must be used.
Note! Take care not to exceed the maximum diameter of the seat
6. The complete spindle guide to be overhauled
7. The non-return valve to be overhauled.
8. Mount the complete spindle guide, including the fuel nozzle, in the fuel valve housing. Carefully slide the spindle guide down into the valve holder, and turn the nozzle until it engages correctly with the guide pin. Check that distance A corresponds to the measurement taken before the valve was disassembled.
Make sure that the fuel nozzle engages correctly with the guide pin in the fuel valve housing. This can be ascertained by attempting to turn the nozzle by hand after mounting. It must not be possible to turn the nozzle.
9. Mount:
• the thrust foot
• the parts of the thrust spindle
• the non-return valve
in the fuel valve housing.
Mount a new O-ring in the uppermost groove of the fuel valve housing.
Lubricate the thread of the valve head with molybdenum disulphide (MoS2).
Fit the valve head with new O-rings.
10. Make sure that the guide pin between valve housing and valve head is intact. Press the valve head down into the valve housing and check that the guide pin engages correctly so as to prevent relative turning of the parts.
11. Assemble the valve by means of the union nut. Place the valve in the valve holder in a drilling machine. Compress the fuel valve and the spring inside. Keep the valve compressed and tighten the union nut with a hook spanner. After overhaul, the fuel valve must be tested in the test rig.
12. If the fuel valve is not to be mounted in the engine immediately after the overhaul, cover all openings of the valve with plastic to prevent dirt from entering the valve during storage.
Mounting
1. Before mounting the fuel valve, thoroughly clean the valve bore in the cylinder cover and check the seating in the bore for marks which, if any, must be eliminated. Mount new O-rings on the fuel valve. Lubricate the valve with molybdenum Disulphide (MoS2).
2. Mount the valve in position in the cylinder cover. Mount the tubular spacers and nuts. Tighten the nuts as stated in Data.
3. Lubricate the thread on the union nipple of the fuel oil pipe with a heat resistant anti seize grease before mounting. Mount the overhauled fuel oil pipe.
Mount and tighten the union nuts. Reconnect the return oil pipe to the fuel valve. Turn on the fuel oil supply. Spindle Guide Overhaul
Replace the complete spindle guide after 8000 hours of operation.
The spindle guide, thrust piece and spindle are matched parts and may not be replaced individually.
1. Clean the outside of the spindle guide in pure gas oil or kerosene. The individual parts of the spindle guide are not interchangeable, therefore only one guide is to be disassembled at a time.
2. Place the spindle guide in a bench vice provided with “soft” jaws, and use the brass mandrel to disassemble the spindle guide.
3. Mount the pulling tool around the fuel nozzle on the spindle guide. Turn the nut to pull the fuel nozzle off the spindle guide.
4. If no pulling tool is available, the fuel nozzle can be dismantled from the spindle guide using two screwdrivers. Place the screwdrivers opposite each other in the small gap between the fuel nozzle and the spindle guide and very carefully force the fuel nozzle off the spindle guide.
5. Clean all the parts of the spindle guide in gas oil and wipe dry with a clean piece of cloth. Clean all parts again in kerosene or ‘Electro cleaner’ and wipe dry with a clean piece of cloth.
Place all the parts on a clean, lint-free cloth and examine them through an 8-10 times magnification magnifying glass and an inspection lamp.
During the examination, pay special attention to the seating surfaces and sliding surfaces of the parts.
6. Remove any deposits or very fine scratches by placing the spindle, thrust piece or spindle guide respectively in a lathe, and polishing with a very fine conventional polishing linen ‘grade 360’. Use also a little oil for the polishing (a coarser polishing linen must absolutely not be used).
After polishing, clean the parts again and re-check the seat on thrust piece/spindle, the seat on slide valve/spindle, and the seat on spindle/guide. Use an inspection lamp and an 8-10 times enlargement magnifying glass. If the seats are not in order, i.e. if there are pressing-in marks or similar on the seats, the complete spindle guide must be discarded.
The sliding surface of the cut-off slide may only be polished VERY carefully. The sliding surface must not be damaged.
7. Clean any carbon deposits from the central bore of the fuel nozzle by means of the special brass brush. During this operation be very careful not to push the drill too far to avoid scratching the snug-fit surface on the inside of the fuel nozzle.
Clean the spray holes, using gas oil and the special drills. Clean the fuel nozzle with kerosene and wipe dry with a clean cloth. Then test the spray holes with the test pin. If the test pin is able to enter just one of the holes, the fuel nozzle must be discarded.
This also applies to nozzles with oval holes (can be ascertained with a magnifying glass). Check the fuel nozzle before mounting on the spindle guide, the cut-off slide must be able to move freely inside the nozzle.
8. Lubricate the spindle and the thrust piece with the cut-off slide with a little Molybdenum
9. Assemble the thrust piece, the spindle and the spindle guide and carefully knock the parts together using a soft hammer.
10. Shake the spindle guide back and forth. The spindle with the cut-off slide must be able to slide freely back and forth inside the spindle guide, with a ‘clicking’ sound.
11. Lubricate the sliding surfaces of the nozzle and the spindle with a little Molybdenum Disulphide (MoS2). See Procedure 913-11. Mount the nozzle on the spindle guide. Place the parts on the plane of a drilling machine or hydraulic press and position the mounting tool over the parts. Make sure that all the parts are perfectly aligned. Press the nozzle on to the spindle guide. If no mounting tools are available, the nozzle can be mounted on the spindle guide using a short piece of pipe. Place the pipe around the nozzle, so that the lower end of the pipe rests on the ‘foot’ of the fuel nozzle. Then press the parts together the same way as when using the mounting tools. Check that the spindle inside the spindle guide is able to move freely, by ‘shaking’ the spindle guide.
12. If the spindle guide is not to be mounted in a fuel valve immediately after the overhaul, cover all openings of the spindle guide with plastic to prevent dirt from entering the spindle guide during storage.
Fuel Valve Non-return Valve Overhaul:- Extreme care and accuracy should be exercised when carrying out this operation.
1. Clean the outside of the non-return valve with pure gas oil. The individual parts are not interchangeable, therefore only one guide is to be disassembled at a time. Except for the slide valve spring, defective parts cannot be replaced individually by new ones.
Place the non-return valve in a bench vice provided with “soft” jaws, and disassemble the non-return valve, using the disassembling tool and a hammer.
2. Clean all the parts for the spindle guide in gas oil and then blow clean. Finally, clean in either gas oil, kerosene or ‘Electro-cleaner', and blow the parts dry with compressed air.
3. Now place the parts on clean, lint-free rags and examine with an 8-10 times enlargement magnifying glass, and an inspection lamp with magnifying glass.
4. Examine the slide faces of movable parts for coating. Vent slide/housing will be too tight if there is a coating. Fix vent slide and, subsequently, housing in a lathe and remove the coating by means of very fine conventional polishing linen ‘grade 360'.
Also a little oil should be used (a coarser polishing linen must absolutely not be used).
5. Check spring for the thrust piece for outside wear marks. If defective, it should be exchanged. Check the seat on thrust piece /vent slide, and the seat on vent slide/housing. Use an inspection lamp and an 8-10 times enlargement magnifying glass. If the seats are not in order, i.e. if there are pressing-in marks or similar on the seats, the complete spindle guide must be discarded.
6. Mount the non-return valve as follows:
• Lubricate all movable parts with molybdenum disulphide (MoS2).
• Place the loosely-assembled non-return valve on the plane of a drilling machine, with the tool.
• Make sure that the thrust piece and the other parts are perfectly aligned and that the thrust piece is guided in the vent slide.
• Press the handle until the housing and thrust piece meet.
7. If the non-return valve is not to be mounted in a fuel valve immediately after the overhaul, cover all openings of the non-return valve with plastic to prevent dirt from entering the valve during storage.
Dismantling Fuel Injection Valve from Cyl. Head
1. Unscrew the nuts which are holding the support at the top of the injector.
2. Dismantle the support from fuel injection valve.
3. Install the removal device on the fuel injection valve.
4. Take out the high pressure injection pipe.
5. Pull out the fuel injection valve from the cylinder head by rotating the nuts of removal device.
6. Clean the fuel injection valve and nozzle. Take care not to damage or clog the nozzle holes.
Function Test of Fuel Injection Valve
1. Mount the fuel injection valve on the testing device.
The locating pin should be fitted to the groove in testing holder correctly.
2. Connect the high pressure pipe to the fuel injection valve.
3. Pump slowly by hand, and check the valve opening pressure and spray pattern.
Valve opening pressure : 450 bar
Don’t put hands near spray area during testing. High injection pressure may damage to the human body.
Adjustment of Valve Opening Pressure
If the valve opening pressure is not 450 bar, adjust opening pressure as following process.
1. Loosen the locking nut fitted at top.
2. Turn the adjusting screw slowly and check valve opening pressure while pumping.
3. Adjust the valve opening pressure by the step of 10 bar.
4. When pressure setting is finished, tighten the locking nut with a torque spanner to fix the adjusting screw.
Tightening torque : 100 Nm (with molycote)
Dismantling of Fuel Valve Nozzle using the special tool.
1. Fix the tool on support.
2. Insert fuel valve on the tool.
3. Fix fuel valve on tool with bolts.
4. Loosen the locking nut.
5. Remove the sealing gasket (sealing ring)
6. Loosen the nozzle holder nut with a torque spanner.
Carbon between nozzle and nozzle holder nut can make Dowel pin broken when dismantling nozzle. Be careful of damage of dowel pin.
Cleaning of Nozzle hole
If some of holes are clogged, the nozzle should be dismantled and cleaned by using special cleaning tool.
After cleaning the nozzle, reassemble the fuel valve and repeat the above function test. If the spray pattern is not normal or still clogged, scrap the nozzle and replace with new ones.
Remove carbon, and clean the nozzle nut and nozzle. Especially clean surface for contact between the nozzle holder nut and nozzle in order to prevent leakage by abnormal contact.
Assembling of Fuel Valve Nozzle by using special tool:-
1. Fix the tool on support.
2. Insert fuel valve on the tool.
3. Fix fuel valve with bolt.
4. Loosen the locking nut.
5. Insert dowel pin in pin hole.
6. Connect the nozzle holder nut with nozzle in fuel valve body
7. Tighten the nozzle holder nut(J) with a torque spanner.
Tightening torque : 300 Nm (with molycote 1000 or copaslip)
8. Install seal ring on nozzle.
Lapping of Fuel Injection Valve Bush after coating with small amount of a fine lapping compound on seating surface, rub the surface by rotating the lapping tool manually several times in order to remove carbon and clean the bush before mounting the fuel injection valve on the cylinder head.
Mounting Fuel Injection Valve on Cyl. Head
1. Replace the O-rings with new ones, and clean fuel injection valve and cylinder head.
2. Mount the fuel injection valve on the cylinder head, and tighten the nuts of support slightly. The locating pin should be fitted to the groove in cylinder head correctly. Take care not to damage the nozzle and O-rings during mounting.
3. Tighten the nuts of support. Tightening torque : 200 Nm (with molycote)
4. Insert the injection pipe correctly and tighten the nut. Tightening torque : 10 Nm -> 30 Nm -> 60 Nm by three steps (with molycote)
Reconditioning of Fuel Injection valve
Purpose
It is generally recognized that atomization pattern deteriorates gradually due to seat wear after a certain period of diesel engine-running.
Though mal-injection pattern was observed, its phenomena can be reconditioned by lapping in order to revive the performance for continuous re-use.
How to Lap on Seat
1. Necessary tools and material
(a)Drilling machine or electric drill
(b) Lapping powder No. 1500 ~ No. 1800
(c) Cleaning oil, gas oil, lube. oil and compressed air
2. Procedure
(a) Fit needle valve into drill chuck.
(b) Apply lapping powder dissolved in lube. oil to needle valve seat.
(c) Insert needle valve into nozzle body. Fit them by rotating for minimum lapping (approx. 15 seconds) to find circumferential contact-trace on needle seat. When circumferential contact trace was not found and/or demanded area due to foreign substance was still remained, lapping is more necessary.
(d) When circumferential contact-trace on needle seat was found, clean by oil and do air-blow. Then apply lube.oil to needle seat and assemble it back.
(e) Reconditioning of fuel injection valve could be available once or twice.
Fuel Injection Valve Checking Atomizing Condition
As an atomizing condition of F.O has many effects on the engine combustion, maintenance should be observed according to the regulated schedule.
Maintenance schedule:
The procedure of Checking Atomizing Condition Carries out checking the atomizing condition of the fuel injection valve according to the standard maintenance procedure.
Maintenance procedure:
Heavy fuel oil residues in injection valves may adversely affect the test results and impede cleaning. Operate the engine on Diesel oil for approx. one hour prior to dismantling injection valves. If this is not possible and the engine has to be shut down from operation on heavy fuel oil, the injection valve has to be disassembled and cleaned before the checks described here can be carried out.
Only absolutely clean anticorrosion oil should be used for testing the injection valves.
The hydraulic pressure has to be increased slowly until the opening pressure is reached, as otherwise, faults will occur when reading off the opening pressure. (The test pressure must not exceed the regulated value.) During the fuel injection valve test, the test criteria are nozzle hole clogging and leaking F.O. When the abnormal condition occurs after checking the atomizing condition, the fuel injection nozzle should be changed by a new one.
Checking Atomizing Condition (1)
The Nozzle Bores
1. Checking procedure
(a) Open the pressure relief valve.
(b) Loosen the hexagon nut of the fuel injection valve, and turn back the set screw until the tension of the compression spring has been released.
(c) Close the pressure relief valve. Actuate the hand pump evenly, and adjust the opening pressure to 30 bars by means of the set screw.
2. Criterion of decision
(a) All nozzle holes open: normal
(b) Partly clogged: Disassemble the fuel injection valve and clean or change to the new one.
Maintenance procedure:
Checking Atomizing Condition (2)
Keeping the tightness
1. Checking procedure
(a) Actuate the hand pump evenly until the pressure gauge shows 250 bars.
(b) The injection nozzle can be considered tight if no drop falls within a period of 5 seconds.
2. Criterion of decision – All nozzle holes open
(a) Keeping the tightness: normal
(b) Dripping on nozzle: re-conditioning or changing to a new one.
When testing injection valves, it may show the pattern of penetration because the nozzle’s behaviour during engine operation cannot be equal by means of the nozzle tester. It is because of the pressure gap between the cylinder chamber and the atmosphere, and using the hand pump is hard to make a similar pattern such as fuel injection pump during the engine running. If there is no dripping on the tip of the atomizer and no closed holes, and the exhaust gas temperature and maximum pressure in each cylinder is in normal condition, the nozzle can be expected to make appropriate engine performance.
If the pump barrel is lowered, injection commences earlier as inlet and spill ports are cut off earlier.
Similarly, inlet and spill ports open earlier i.e end of the injection takes place earlier with no change in fuel delivered, provided the plunger is not moved circumferentially.
- When it is required to retard the injection period, the pump barrel is raised.
- The fuel cam is used to adjust the timing of the beginning of injection as normal.
Pmax adjustment:
1. The Maximum Combustion Pressure (Pmax) is adjusted for the individual units at the fuel pump VIT index arm.
3. To increase Pmax, adjust to a higher VIT index (advance injection).
To decrease Pmax, adjust to a lower VIT index (delay injection).
Change of 1 index mark, corresponds to Pmax being altered approx. 3-4 bar.
The individual Pmax value must not deviate more than 3 bar from the average value for all cylinders.
Construction and functioning of slide type fuel valve.
The fuel valve consists of a valve head, union nut, valve body, and nozzle. Fitted within the valve body is a nonreturn valve with a combined slide/valve, thrust spindle with thrust spring, thrust foot, and spindle guide. When the fuel valve is fitted in the cylinder cover, the valve parts are tightened together by the pressure from the nuts being transmitted through the valve head, non-return valve, thrust spindle, spindle guide and nozzle to the valve body, which is pressed into the tapered bore in the cylinder cover. The union nut keeps the valve head and valve body together during the dismantling of the fuel valve.
The complete spindle guide consists of a spindle guide, thrust piece and spindle with a cut-off slide. The spindle guide is assembled with a press fit. The spindle is pressed against the tapered valve seat of the spindle guide by the action of the thrust spring, the spring pressure is transmitted through the slotted thrust foot. The thrust spring determines the opening pressure of the valve.
Optionally, an extra disc can be inserted to raise the opening pressure by 30 bar.
The non-return valve consists of housing, thrust piece, slide and spring. The nonreturn valve is assembled with a press fit.
The slide is pressed by the spring against the tapered valve seat inside the non-return valve. In this position, the head of the slide uncovers a small bore arranged for circulation purposes in a thrust piece.
Position I:
The electrical fuel oil circulating pump circulates preheated oil through the fuel pump and fuel valve. In the fuel valve the oil passes through the central bore of the valve head and continues to the thrust piece of the non-return valve, leaving through the circulation bore of the latter. Thence the oil is passed through the interior of the valve body to an outlet pipe on the side of the valve head.
The space round the tapered valve seat of the spindle is also filled with oil, but the circulating pump pressure is insufficient to overcome the force of the spring and lift the spindle.
If, for some reason, valve spindle, spindle/cut-off slide should not close during engine standstill, then the closed spindle in the non-return valve will prevent the circulating pump from pressing oil through the nozzle, and thus obviate the risk of the engine cylinder being filled with oil.
Position II:
When, at the beginning of the delivery stroke, the pressure has risen to about 10 bar, the force of the spring in the non-return valve will be overcome and spindle pressed back against the shoulder of thrust piece. Position III:
When the spindle in the non-return valve is pressed upwards, the circulation bore of the thrust piece is closed, and the oil passes the seat of the spindle and enters the space round valve spindle seat in spindle guide. When the pressure has risen to the preset opening value of the fuel valve, the spindle is lifted, and oil is forced through the nozzle into the engine cylinder.
At the termination of the delivery stroke, first the valve spindle and then the spindle in the non-return valve will be pressed against their respective seats, the injection of fuel stops, and oil is again circulated through the valve (position-I).
Removal of seized fuel Injector
Carbon soot and high temperature between the injector body and pocket causes it to seize. Sometime it becomes very difficult to remove the injector out of the pocket, Non conventional methods can be used to remove injector when such a condition exist, Precautions must be taken because these method involve high force, injector can jump out and injury to personnel can take place. The Nuts must not be removed out completely till the injector is loose.A. Use of special Tool
A special tool is provided by the manufacturer to draw a sticky injector out of pocket shown in the figure. Remove the nuts but not completely out and fix the tool as shown in diagram. The tool is constructed in such a way that a long lever provided in the tool transmits a high torque which pushes the injector out of body. Sometime a little tapping by hammer assist in the job.
In case the injector is still stuck, a rag soaked with release oil to be rapped around the injector. The oil will seep into the clearance and dissolve the hard cake, it should be left there for some time. Now the process of extracting with special tool can be repeated, with a little hammer tapping. As the injector is loose, now the nuts can be removed compeletely and so the injector.
Metals property of expanding with increasing temperature and contracting by cooling is useful when clearance between the mating surfaces is negligible.
Using a release oil and forcing the injector out if failed, the injector can be cooled by using ice. Use a cylindrical dam or a small piece of pipe to keep ice around the injector. Let the injector get cooled for sufficient time. Now the process of extracting the injector by using special tool should be applied.
C. Pulling by using chain block:This is a dangerous process require high level of safety to be followed. Slig wire and chain block is used and arranged as shown in diagram. The may also require assistance of the tool. Take care that the pulling should be in the direction in the axis of injector, Nuts should not be taken out completely before injector is loose.
Pressure testing of slide-type valve
Fuel valve opening pressure 350 - 380 barFuel valve tightening torque 25 Nm
Inlet seat, max. diameter 18 mm
Fuel valve weight 8 kg
Safety precautions:-
Stopped engine
Shut off starting air supply – At starting air receiver
Block the main starting valve
Shut off starting air distributor/distributing system supply
Shut off safety air supply – Not ME engines
Shut off control air supply
Shut off air supply to exhaust valve – Only with stopped lubricating oil pumps
Engage turning gear
Shut off cooling water
Shut off fuel oil
Stop lubricating oil supply
Lock the turbocharger rotors
The fuel valves must be given the utmost attention and care, as the greater part of irregularities that may occur during the running of the engine can be attributed to defects in these valves.
If the engine gives normal performance in accordance with diagrams and exhaust temperatures, it is only necessary to inspect the fuel valves after the service period stated in the Checking and Maintenance Schedules.
In order to obtain reliable results during testing of the fuel valves, all fuel valves that are dismantled from the engine must be disassembled, cleaned, inspected and re-assembled befire testing.
"In the event that the slide-type fuel valve is pressure tested without being cleaned between the fuel nozzle and the cut-off slide, the opening pressure value measuered might be considerably lower than specified."
All fuel valves must be function-tested before being mounted in the cylinder cover.
1. Pressure testing pump
If an air supply of 10 bar is not available, working air of 7 bar can be used.
Prescribed oil: Hydraulic oil (rust-preventing) with a viscosity of between 7 and 10 cSt at 50°C.
2. Setting-up the fuel valve
Place the fuel valve in the test rig and secure it with the tubular spacers and nuts. Tighten the nuts to the torque stated in Data.
Mount the oil pipe between the pressure testing pump and the fuel valve.
3. Pressure testing procedure
The subsequent items must be followed in the sequence stated. Items 4, 6, 7 and 8 are each divided into the following four subitems:
A. Objective
B. Procedure
C. Acceptance criteria
D. Cause of fault.
4. Flushing and jet control
A. Objective: To remove air in the system and check the fuel jet.
B. Procedure: The control handle must be in the OPEN position. Slowly increase the working pressure until straight jets of oil are ejected from the nozzle holes (no atomization).
C. Acceptance criteria: There is to be a continuous jet of oil through at least one of the nozzle holes. Owing to the geometry of the internal part of the nozzle – and because the height to which the spindle is lifted during pressure testing is lower than the height it is lifted during normal engine operation – the fuel oil will not necessarily flow from all of the nozzle holes.
D. Cause of fault: If the above point C is not fulfilled, the cause may be:
• Dirt in the nozzle holes.
• The nozzle is not mounted correctly.
5. Atomization test
Do NOT attempt to carry out an atomization test on slide type fuel valves, as this may damage the cut-off slide and nozzle.
The reason is that the atomization test may damage the valve because it makes the needle oscillate, with a small lift at a very high frequency. The high pressure drop across the cut-off edge and the high contact pressure between slide and fuel nozzle, in combination with the poor lubricity of the test oil, increase the risk of seizures between cut-off slide and nozzle.
All of these conditions involve the risk of seizure between the cut-off slide and the nozzle.
6. Opening pressure.
A. Objective: To check the opening pressure.
B. Procedure: The control handle is to be in the OPEN position. Increase the oil pressure until oil is admitted through the nozzle holes.
C. Acceptance criteria: Check the opening pressure on the pressure gauge.
D. Cause of fault: If the opening pressure is higher than specified, the cause may be that a wrong type of spring is used – replace the spring on the thrust spindle, if necessary, replace the complete thrust spindle.
If the opening pressure is lower than specified, the cause may be that the spring has sagged – replace the spring, or add a special thin disc.
If a spring or a disc has been changed, the pressure testing procedure of the fuel valve must be repeated from step 4. 7. Sealing test and sliding function A. Objective: To check the needle valve seat for tightness and the slide for correct closing. B. Procedure: The control handle must be in the OPEN position. Slowly increase the oil pressure to about 50 bar below the opening pressure. Maintain the built-up pressure by moving the control handle into the CLOSED position. Repeat the procedure two or three times. C. Acceptance criteria: Oil must not flow from the nozzle holes. The pressure drops relatively slowly to about 15 bar, after which it drops quickly to 0 (the slide is pressed against the conical seat and opens for circulation oil). Oil flows out of the leak oil outlet when the fuel valve is full of oil.
D. Cause of fault:
D.1 Sealing test
If oil flows out of the nozzle holes, the cause is either:
• Defective spindle guide at needle seat, or a sticking spindle. Examine and/or replace the spindle guide.
• Too quick pressure drop:
– the clearances of the movable parts, both of the spindle guide and of the nonreturn valve, are too large, or – the seats between the thrust piece/ spindle in the spindle guide or thrust piece/valve slide in the non-return valve are damaged.
Examine and/or replace both the spindle guide and non-return valve.
D.2 Sliding function
The pressure drops relatively slowly to about 15 bar, after which it drops quickly to 0 (the slide is pressed against the conical seat and opens for circulation oil).There will always be an oil flow from the leak oil outlet when the fuel valve is full of oil.
If a quick pressure drop from 15 to 0 bar cannot be registered:
• The valve slide is sticking; or
• the vent hole in the thrust piece is blocked.
If so, disassemble and examine the spindle guide, replace if necessary.
8. Pressure test, O-ring sealings
A. Objective: To ensure that the leak oil (circulation oil) remains in the closed system. B. Procedure: The control handle is to be in the OPEN position. Build up a working pressure of about max. 10 bar until oil flows out of the leak oil outlet.
C. Acceptance criteria: Close the leak oil outlet with a gasket and plug screw. Increase the working pressure to about 100 bar. Move the control handle to the CLOSED position. The built-up pressure of about 100 bar should be maintained. D. Cause of fault: If oil leaks out at the union nut, the O-ring inside the fuel valve head is defective, and must be replaced.
Overhauling of slide-type valve
Dismantling1. Close the fuel oil inlet and outlet valves. Dismantle the high-pressure pipe. Disconnect the return oil pipe from the fuel valve.
2. Remove the nuts and the tubular spacers.
3. Take out the valve. If the valve is sticking, use the fuel valve dismantling tool to pull the valve clear of the top cover. If the valve is not to be overhauled immediately, the valve should be immersed in diesel oil until overhauling.
When fuel valves are overhauled, all parts should be handled carefully and be kept clean. Use only clean, non-fluffy rags for wiping purposes. Make sure to remove all liquid or solid impurities.
Whenever fuel valves are overhauled, all sealing rings should be discarded and replaced by new, faultless sealing rings before reassembly.
1. Measure the length of the protruding part of the nozzle, and write down the result for correct re-assembling of the valve.
2. Place the valve holder in a machine vice, mount the fuel valve in the holder and fit the valve with the guide disc from the grinding tool.
3. Compress the fuel valve and the spring inside, by means of a drilling machine, to avoid seizures in the union thread. Hold the fuel valve compressed and unscrew the union nut with a hook spanner. Remove the valve from the valve holder.
4. Pull the valve head clear of the valve housing.
Remove the:
• Non return valve
• Thrust spindle parts
• Thrust foot
• Spindle guide and fuel nozzle from the valve housing.
Remove and discard all the O-rings.
5. Carefully clean and examine all surfaces of the:
• Fuel valve housing
• Fuel valve head
• Thrust spindle
If necessary, grind the seating surfaces by means of the grinding mandrels and a fine-grain abrasive (such as Carborundum No. 500).
This grinding must only be carried out manually. After the grinding, wash the parts in gas oil and blow clean by means of compressed air to remove any remains of the grinding compound. In the event of more serious damage to the seating surface for the high-pressure pipe in the valve head, the milling tool can be used.
Normally, the milling tool is turned by hand, but it may be fitted in the chuck of a column type drilling machine provided that the number of revolutions is kept at a minimum (not exceeding approx. 100 r/min). An ample supply of cutting emulsion must be used.
Note! Take care not to exceed the maximum diameter of the seat
6. The complete spindle guide to be overhauled
7. The non-return valve to be overhauled.
8. Mount the complete spindle guide, including the fuel nozzle, in the fuel valve housing. Carefully slide the spindle guide down into the valve holder, and turn the nozzle until it engages correctly with the guide pin. Check that distance A corresponds to the measurement taken before the valve was disassembled.
Make sure that the fuel nozzle engages correctly with the guide pin in the fuel valve housing. This can be ascertained by attempting to turn the nozzle by hand after mounting. It must not be possible to turn the nozzle.
9. Mount:
• the thrust foot
• the parts of the thrust spindle
• the non-return valve
in the fuel valve housing.
Mount a new O-ring in the uppermost groove of the fuel valve housing.
Lubricate the thread of the valve head with molybdenum disulphide (MoS2).
Fit the valve head with new O-rings.
10. Make sure that the guide pin between valve housing and valve head is intact. Press the valve head down into the valve housing and check that the guide pin engages correctly so as to prevent relative turning of the parts.
11. Assemble the valve by means of the union nut. Place the valve in the valve holder in a drilling machine. Compress the fuel valve and the spring inside. Keep the valve compressed and tighten the union nut with a hook spanner. After overhaul, the fuel valve must be tested in the test rig.
12. If the fuel valve is not to be mounted in the engine immediately after the overhaul, cover all openings of the valve with plastic to prevent dirt from entering the valve during storage.
Mounting
1. Before mounting the fuel valve, thoroughly clean the valve bore in the cylinder cover and check the seating in the bore for marks which, if any, must be eliminated. Mount new O-rings on the fuel valve. Lubricate the valve with molybdenum Disulphide (MoS2).
2. Mount the valve in position in the cylinder cover. Mount the tubular spacers and nuts. Tighten the nuts as stated in Data.
3. Lubricate the thread on the union nipple of the fuel oil pipe with a heat resistant anti seize grease before mounting. Mount the overhauled fuel oil pipe.
Mount and tighten the union nuts. Reconnect the return oil pipe to the fuel valve. Turn on the fuel oil supply. Spindle Guide Overhaul
Replace the complete spindle guide after 8000 hours of operation.
The spindle guide, thrust piece and spindle are matched parts and may not be replaced individually.
1. Clean the outside of the spindle guide in pure gas oil or kerosene. The individual parts of the spindle guide are not interchangeable, therefore only one guide is to be disassembled at a time.
2. Place the spindle guide in a bench vice provided with “soft” jaws, and use the brass mandrel to disassemble the spindle guide.
3. Mount the pulling tool around the fuel nozzle on the spindle guide. Turn the nut to pull the fuel nozzle off the spindle guide.
4. If no pulling tool is available, the fuel nozzle can be dismantled from the spindle guide using two screwdrivers. Place the screwdrivers opposite each other in the small gap between the fuel nozzle and the spindle guide and very carefully force the fuel nozzle off the spindle guide.
5. Clean all the parts of the spindle guide in gas oil and wipe dry with a clean piece of cloth. Clean all parts again in kerosene or ‘Electro cleaner’ and wipe dry with a clean piece of cloth.
Place all the parts on a clean, lint-free cloth and examine them through an 8-10 times magnification magnifying glass and an inspection lamp.
During the examination, pay special attention to the seating surfaces and sliding surfaces of the parts.
6. Remove any deposits or very fine scratches by placing the spindle, thrust piece or spindle guide respectively in a lathe, and polishing with a very fine conventional polishing linen ‘grade 360’. Use also a little oil for the polishing (a coarser polishing linen must absolutely not be used).
After polishing, clean the parts again and re-check the seat on thrust piece/spindle, the seat on slide valve/spindle, and the seat on spindle/guide. Use an inspection lamp and an 8-10 times enlargement magnifying glass. If the seats are not in order, i.e. if there are pressing-in marks or similar on the seats, the complete spindle guide must be discarded.
The sliding surface of the cut-off slide may only be polished VERY carefully. The sliding surface must not be damaged.
7. Clean any carbon deposits from the central bore of the fuel nozzle by means of the special brass brush. During this operation be very careful not to push the drill too far to avoid scratching the snug-fit surface on the inside of the fuel nozzle.
Clean the spray holes, using gas oil and the special drills. Clean the fuel nozzle with kerosene and wipe dry with a clean cloth. Then test the spray holes with the test pin. If the test pin is able to enter just one of the holes, the fuel nozzle must be discarded.
This also applies to nozzles with oval holes (can be ascertained with a magnifying glass). Check the fuel nozzle before mounting on the spindle guide, the cut-off slide must be able to move freely inside the nozzle.
8. Lubricate the spindle and the thrust piece with the cut-off slide with a little Molybdenum
9. Assemble the thrust piece, the spindle and the spindle guide and carefully knock the parts together using a soft hammer.
10. Shake the spindle guide back and forth. The spindle with the cut-off slide must be able to slide freely back and forth inside the spindle guide, with a ‘clicking’ sound.
11. Lubricate the sliding surfaces of the nozzle and the spindle with a little Molybdenum Disulphide (MoS2). See Procedure 913-11. Mount the nozzle on the spindle guide. Place the parts on the plane of a drilling machine or hydraulic press and position the mounting tool over the parts. Make sure that all the parts are perfectly aligned. Press the nozzle on to the spindle guide. If no mounting tools are available, the nozzle can be mounted on the spindle guide using a short piece of pipe. Place the pipe around the nozzle, so that the lower end of the pipe rests on the ‘foot’ of the fuel nozzle. Then press the parts together the same way as when using the mounting tools. Check that the spindle inside the spindle guide is able to move freely, by ‘shaking’ the spindle guide.
12. If the spindle guide is not to be mounted in a fuel valve immediately after the overhaul, cover all openings of the spindle guide with plastic to prevent dirt from entering the spindle guide during storage.
Fuel Valve Non-return Valve Overhaul:- Extreme care and accuracy should be exercised when carrying out this operation.
1. Clean the outside of the non-return valve with pure gas oil. The individual parts are not interchangeable, therefore only one guide is to be disassembled at a time. Except for the slide valve spring, defective parts cannot be replaced individually by new ones.
Place the non-return valve in a bench vice provided with “soft” jaws, and disassemble the non-return valve, using the disassembling tool and a hammer.
2. Clean all the parts for the spindle guide in gas oil and then blow clean. Finally, clean in either gas oil, kerosene or ‘Electro-cleaner', and blow the parts dry with compressed air.
3. Now place the parts on clean, lint-free rags and examine with an 8-10 times enlargement magnifying glass, and an inspection lamp with magnifying glass.
4. Examine the slide faces of movable parts for coating. Vent slide/housing will be too tight if there is a coating. Fix vent slide and, subsequently, housing in a lathe and remove the coating by means of very fine conventional polishing linen ‘grade 360'.
Also a little oil should be used (a coarser polishing linen must absolutely not be used).
5. Check spring for the thrust piece for outside wear marks. If defective, it should be exchanged. Check the seat on thrust piece /vent slide, and the seat on vent slide/housing. Use an inspection lamp and an 8-10 times enlargement magnifying glass. If the seats are not in order, i.e. if there are pressing-in marks or similar on the seats, the complete spindle guide must be discarded.
6. Mount the non-return valve as follows:
• Lubricate all movable parts with molybdenum disulphide (MoS2).
• Place the loosely-assembled non-return valve on the plane of a drilling machine, with the tool.
• Make sure that the thrust piece and the other parts are perfectly aligned and that the thrust piece is guided in the vent slide.
• Press the handle until the housing and thrust piece meet.
7. If the non-return valve is not to be mounted in a fuel valve immediately after the overhaul, cover all openings of the non-return valve with plastic to prevent dirt from entering the valve during storage.
Auxiliary Engine Fuel Injector
In case that the exhaust temperature of a particular cylinder deviates considerably from the others, dismount and inspect the fuel injection valve carefully. The possible causes are an incorrect mounting of fuel injection valve, or uneven injection of fuel oil to combustion chamber, or wrong valve opening pressure. In order to check correct operation of the fuel injection valve, functional test should be performed by means of the hand pump before mounting the fuel injection valve.1. Unscrew the nuts which are holding the support at the top of the injector.
2. Dismantle the support from fuel injection valve.
3. Install the removal device on the fuel injection valve.
4. Take out the high pressure injection pipe.
5. Pull out the fuel injection valve from the cylinder head by rotating the nuts of removal device.
6. Clean the fuel injection valve and nozzle. Take care not to damage or clog the nozzle holes.
Function Test of Fuel Injection Valve
1. Mount the fuel injection valve on the testing device.
The locating pin should be fitted to the groove in testing holder correctly.
2. Connect the high pressure pipe to the fuel injection valve.
3. Pump slowly by hand, and check the valve opening pressure and spray pattern.
Valve opening pressure : 450 bar
Don’t put hands near spray area during testing. High injection pressure may damage to the human body.
Adjustment of Valve Opening Pressure
If the valve opening pressure is not 450 bar, adjust opening pressure as following process.
1. Loosen the locking nut fitted at top.
2. Turn the adjusting screw slowly and check valve opening pressure while pumping.
3. Adjust the valve opening pressure by the step of 10 bar.
4. When pressure setting is finished, tighten the locking nut with a torque spanner to fix the adjusting screw.
Tightening torque : 100 Nm (with molycote)
Dismantling of Fuel Valve Nozzle using the special tool.
1. Fix the tool on support.
2. Insert fuel valve on the tool.
3. Fix fuel valve on tool with bolts.
4. Loosen the locking nut.
5. Remove the sealing gasket (sealing ring)
6. Loosen the nozzle holder nut with a torque spanner.
Carbon between nozzle and nozzle holder nut can make Dowel pin broken when dismantling nozzle. Be careful of damage of dowel pin.
Cleaning of Nozzle hole
If some of holes are clogged, the nozzle should be dismantled and cleaned by using special cleaning tool.
After cleaning the nozzle, reassemble the fuel valve and repeat the above function test. If the spray pattern is not normal or still clogged, scrap the nozzle and replace with new ones.
Remove carbon, and clean the nozzle nut and nozzle. Especially clean surface for contact between the nozzle holder nut and nozzle in order to prevent leakage by abnormal contact.
Assembling of Fuel Valve Nozzle by using special tool:-
1. Fix the tool on support.
2. Insert fuel valve on the tool.
3. Fix fuel valve with bolt.
4. Loosen the locking nut.
5. Insert dowel pin in pin hole.
6. Connect the nozzle holder nut with nozzle in fuel valve body
7. Tighten the nozzle holder nut(J) with a torque spanner.
Tightening torque : 300 Nm (with molycote 1000 or copaslip)
8. Install seal ring on nozzle.
Lapping of Fuel Injection Valve Bush after coating with small amount of a fine lapping compound on seating surface, rub the surface by rotating the lapping tool manually several times in order to remove carbon and clean the bush before mounting the fuel injection valve on the cylinder head.
Mounting Fuel Injection Valve on Cyl. Head
1. Replace the O-rings with new ones, and clean fuel injection valve and cylinder head.
2. Mount the fuel injection valve on the cylinder head, and tighten the nuts of support slightly. The locating pin should be fitted to the groove in cylinder head correctly. Take care not to damage the nozzle and O-rings during mounting.
3. Tighten the nuts of support. Tightening torque : 200 Nm (with molycote)
4. Insert the injection pipe correctly and tighten the nut. Tightening torque : 10 Nm -> 30 Nm -> 60 Nm by three steps (with molycote)
Reconditioning of Fuel Injection valve
Purpose
It is generally recognized that atomization pattern deteriorates gradually due to seat wear after a certain period of diesel engine-running.
Though mal-injection pattern was observed, its phenomena can be reconditioned by lapping in order to revive the performance for continuous re-use.
How to Lap on Seat
1. Necessary tools and material
(a)Drilling machine or electric drill
(b) Lapping powder No. 1500 ~ No. 1800
(c) Cleaning oil, gas oil, lube. oil and compressed air
2. Procedure
(a) Fit needle valve into drill chuck.
(b) Apply lapping powder dissolved in lube. oil to needle valve seat.
(c) Insert needle valve into nozzle body. Fit them by rotating for minimum lapping (approx. 15 seconds) to find circumferential contact-trace on needle seat. When circumferential contact trace was not found and/or demanded area due to foreign substance was still remained, lapping is more necessary.
(d) When circumferential contact-trace on needle seat was found, clean by oil and do air-blow. Then apply lube.oil to needle seat and assemble it back.
(e) Reconditioning of fuel injection valve could be available once or twice.
Fuel Injection Valve Checking Atomizing Condition
As an atomizing condition of F.O has many effects on the engine combustion, maintenance should be observed according to the regulated schedule.
Maintenance schedule:
The procedure of Checking Atomizing Condition Carries out checking the atomizing condition of the fuel injection valve according to the standard maintenance procedure.
Maintenance procedure:
Heavy fuel oil residues in injection valves may adversely affect the test results and impede cleaning. Operate the engine on Diesel oil for approx. one hour prior to dismantling injection valves. If this is not possible and the engine has to be shut down from operation on heavy fuel oil, the injection valve has to be disassembled and cleaned before the checks described here can be carried out.
Only absolutely clean anticorrosion oil should be used for testing the injection valves.
The hydraulic pressure has to be increased slowly until the opening pressure is reached, as otherwise, faults will occur when reading off the opening pressure. (The test pressure must not exceed the regulated value.) During the fuel injection valve test, the test criteria are nozzle hole clogging and leaking F.O. When the abnormal condition occurs after checking the atomizing condition, the fuel injection nozzle should be changed by a new one.
Checking Atomizing Condition (1)
The Nozzle Bores
1. Checking procedure
(a) Open the pressure relief valve.
(b) Loosen the hexagon nut of the fuel injection valve, and turn back the set screw until the tension of the compression spring has been released.
(c) Close the pressure relief valve. Actuate the hand pump evenly, and adjust the opening pressure to 30 bars by means of the set screw.
2. Criterion of decision
(a) All nozzle holes open: normal
(b) Partly clogged: Disassemble the fuel injection valve and clean or change to the new one.
Maintenance procedure:
Checking Atomizing Condition (2)
Keeping the tightness
1. Checking procedure
(a) Actuate the hand pump evenly until the pressure gauge shows 250 bars.
(b) The injection nozzle can be considered tight if no drop falls within a period of 5 seconds.
2. Criterion of decision – All nozzle holes open
(a) Keeping the tightness: normal
(b) Dripping on nozzle: re-conditioning or changing to a new one.
When testing injection valves, it may show the pattern of penetration because the nozzle’s behaviour during engine operation cannot be equal by means of the nozzle tester. It is because of the pressure gap between the cylinder chamber and the atmosphere, and using the hand pump is hard to make a similar pattern such as fuel injection pump during the engine running. If there is no dripping on the tip of the atomizer and no closed holes, and the exhaust gas temperature and maximum pressure in each cylinder is in normal condition, the nozzle can be expected to make appropriate engine performance.
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