Auxiliary Engine - 4 Stroke Engine

4-Stroke Cycle:

1 Inlet valve opens (20° before TDC)

1-2 Suction stroke

2 Inlet valve closes (60° after TDC)

2-3 Compression stroke

3 Injection begins (10° before TDC)

4 Injection ends (12° before TDC)

4-5 Expansion stroke

5 Exhaust valve opens (42° before BDC)

5-6 Exhaust stroke

6 Exhaust valve close (60° after TDC)

There is an over lapping period of 80° during the exhaust stroke. Exhaust stroke is 282°(42°+180°+60°) long but before closing of exhaust valve inlet valve opens.

Checks before starting engine after overhauling:

Confirm all fittings have been done properly.
Adjust tappet clearance. Take crankshaft deflection if bearings renewed.
Open cooling water, check for leakage through cylinder head and check crankcase.
Purge the cooling water line, check pressure. Open warming up line.
Check play of connecting rod and measure clearances.
Check the lube oil level, Start lube oil priming pump, check flow, check pressure, purge L.O cooler and filter.
Engage turning gear and turn the engine few revolution.
If all the above are in order than carry out blow through.
Check temperature and freeness of bearings.
Start engine at reduced speed.
Check all parameters ( LO, FO, Scavenge air & JCW pressure and Exhaust temperature.)
Stop engine and carry out crankcase inspection.
Adjust tappet if required.
If all the above found in order than run it in off load. Check all parameters.
Run engine at partial load and slowly increase the load.

4 Stroke A.E - Construction

Cylinder heads for 4 stroke engines are of a complex design. They have to house the inlet and exhaust valves with rocker arms, the fuel injector, the air start valve, relief valve and indicator cock. The passages for the inlet air and exhaust gas are incorporated, as are the cooling water passages and spaces.

Normally manufactured from spheroidal graphite or nodular cast iron which is easy to cast. Although not as strong as cast steel, which is difficult to cast into complex shapes due to its poor fluidity, it maintains a reasonable strength under load. Adequate cooling is essential to prevent thermal fatigue due to uneven expansion throughout the casting, and bore cooling has been introduced along with cooling spaces to ensure effective cooling of the "flame plate" (the underside of the cylinder head which forms the top of the combustion chamber).

Cracking of cylinder heads can occur due to poor cooling causing thermal fatigue. Poor cooling can be the result of scale build up within the cooling spaces due to inadequate water treatment. Overloading of the unit causing high peak pressures is also a cause as is incorrect tightening down of the cylinder head. Cracking normally occurs between the valve pockets and/or cooling water spaces. Cracked cylinder heads can be repaired by specialized welding; but this must be done under the guidance and with authorization from the classification societies.

The Connecting Rod is fitted between the Piston and the crankshaft. It transmits the firing force, and together with the crankshaft converts the reciprocating motion to a rotary motion. Made from drop forged steel, on the older engines the bottom of the con rod terminates in a flange known as a Marine Palm which is bolted to the split bottom end (Crankpin) bearing, whilst at the top is rounded to accommodate the gudgeon pin bush.

On older engines the bearings were white metal thick wall bearings, scraped to fit. Clearances were adjusted by inserting or removing shims between the bearing halves. Modern bearings are of the "thin wall" type, where a thin layer of white metal or a tin Aluminium alloy is bonded to a steel shell backing. The clearance on these bearings is non adjustable; When the clearance reaches a maximum the bearing is changed.

Oil to lubricate the crankpin bearing is supplied through a drilled hole in the crankshaft from main Bearing. When inspecting the crankpin bearing and journal it is good practice to check the journal for ovality because if this is excessive, a failure in the hydrodynamic lubrication can occur.

The gudgeon pin connects the piston to the connecting rod. To accommodate the high downward load and to aid effective lubrication the pin has a large diameter. This increases the relative speed between pin and bearing. The bottom halves of the bearing shells have oil gutters cut in them to assist the distribution of oil.

Engine crankcase

An engine crankcase houses the crankshaft and main bearings. Main bearings take the load of the crankshaft. Lube oil has to be inspected and maintained at correct pressure and temperature to reduce the wear and increase the life of bearings. Quality of oil is observed everyday while checking the sump oil level.

The crankcase is inspected periodically to check the following:

• External condition of the crankpin and main bearings

• Locking arrangements of connecting rod bolts

• Securing arrangements of balance weights

• Locking arrangements of main bearing bolts

• Connecting rod play in the crankpin

• Condition of the lubricating oil

• Flow of the lubricating oil

• Check the crank case wall for carbon deposit.

• Check the crank case wall for any sign of micro organism.

• Any smell of Hydrogen Sulphide.

• Check the crank case relief door opening by pressing with the hand or if possible check with spring balance so that value of force applied can be seen.

• Any discoloration signifying hot spot.

Fuel pump overhauling

Before overhauling clean the outer surface of fuel pump.
Clamp the fuel pump in the voice and remove the delivery valve holder.
Take out the delivery valve.
Invert the pump depress the plunger guide and take out the stop ring.
Take out the plunger guide.
Remove the spring seat Spring and plunger
Remove the controls sleeve and the Control rack
Remove the barrel set screw and take the plunger barrel out
Clean all the compound with kerosene using soft brush never use steel brush
Always handle plunger and plunger barrel as a pair
Renew the O rings.
Insert the plunger barrel in fix it with the set screws
Insert the control Rack and fix the control sleeve
Match the mark on the control that controls sleeve and plunger a mismatch of the marks affect the fuel delivery
Assemble the spring seat spring guide and the stop ring
Invert the pump and fix the delivery valve
If require replace the valve as a unit, apply Moly coat and tightened the delivery valve holder.
After assembling the fuel pump and showed that control that moves smoothly.

Fuel pump timing

fuel pump timing or injection timing is an important factor in the combustion process. It is the time when fuel is injected into the cylinder with respect to the position of the Piston. Ideal timing is 5° before Piston reaches top dead center during compression stroke.

Peak combustion pressure depends on the fuel injection timing, if fuel is injected in advance peak pressure increases and exhaust temperature decreases. If the timing is delayed the peak pressure reduces, compression continuous in expansion stroke.

The fuel injection timing of all the unit is checked periodically as recommended by the manufacturer.

Spill port method of checking fuel injection timing:

Injection of fuel start when top of fuel pump plunger cover the suction port. To check the fuel injection timing
Shut the fuel inlet valve
Turn the engine and ensure that 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 gooseneck pipe to the pump discharge
Open the fuel inlet valve and release the fuel into the pump. The fuel run through the pump body and flow out through gooseneck pipe.
Turn the camshaft slowly by turning the engine. The plunger moves upward inside the barrel
When the plunger cover the suction port oil flow stops and fuel injection starts. Note the marking on the flywheel which corresponds to the crank angle in degrees before TDC this will be the fuel injection time of that cylinder.

Fuel injection timing can be adjusted by changing the:

position of the cam
relative position of barrel to the plunger
roll guide thrust pin height

Fuel pump timing adjustment

The fuel pump injection timing depend upon the fuel pump lead.
Before adjusting the lead isolate the fuel system by closing inlet and return valves
Check if the roller is resting on the base circle of the cam.
Distance between upper edge of the roller guide housing and top of trust 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 trust piece using a special extraction tool
Add Sims of required thickness to advance or remove the sims already available to retard the timing.
Use a Mallet to Mount the trust peace in the slot measure the lead once again.
Run engine on full load and check the combustion pressure.

Common Problems Found Auxiliary Engines

1. Power Imbalance of the auxiliary engine

The marine engineer is obliged to monitor all auxiliary engine parameters, notably during taking performance readings of the engine. One very potential issue might be the combustion chamber to need immediate overhauling. You can recognize this problem if there is a high peak pressure variation in any of the auxiliary engine units as compared to the average pressure parameters.

Action: The degree of imbalance has to be assessed. For this, the maximum deviation between the minimum and maximum exhaust temperatures is a ready indication. If the average exhaust temperature of the units is around 350°C and the maximum deviation between the average temperature and a particular unit by about 50°C or more, it needs to be investigated. Firstly, the thermometer must be changed/interchanged and the correct reading ascertained. Once you are convinced that truly there is a large deviation, the matter is to be brought to the notice of senior engineers. This must be attended.

2. Auxiliary engine Generator Not Taking Rated Load

This is a potential threat to encounter if the auxiliary engine generator isn't taking the rated load. The generator could need comprehensive checking and monitoring. If signs like very high temperatures of the engine or there are other abnormal parameters that are usually of high importance or there are other unusual fluctuations, the matter must be brought to the notice of senior engineers.

3. If you find White Metal Particles in the auxiliary engine filters

If you find any metal particles in the auxiliary engine filters (small or large), this indicates that there is wear-down / damage to bearings. This issue requires instant attention, including overhauling of the faulty auxiliary engine unit, if need be. Identifying this unit(s) may not be very easy for an engineer without much experience. Therefore, this must be brought to the notice of the senior engineers.

4. Degradation of Lubricating Oil of the auxiliary engine

The quality of the lubricating oil in the auxiliary engine is of prime importance, as well. So you must monitor its quality. If you find that the oil is degrading while checking it, you have to remove it before reaching the running-hours limit, due to indications of sludge / emulsion. This issue might indicate blow past of the engine units or ingress of water. This auxiliary engine condition requires finding out the faulty unit / equipment (say cooler/heater) followed by major overhauling.

5. Over-Speeding of the auxiliary engine Generator

The situation when uncontrolled acceleration of the engine takes place, it may lead to mechanical failure and serious accidents. This is called over-speeding of auxiliary engine. This usually happens during the time of starting, but could be also encountered while its running on load, due to fuel pump getting stuck or any abnormality in the fuel system. You need to monitor whether your engine is over-speeding by suitable monitoring.

6. Unusual Knocking Sound of the auxiliary engine

A very common problem of the auxiliary engine could be indicated its sound. Any marine engineer must be familiar with the usual working of the auxiliary engine. You must keep an eye or rather an ear, if you hear an unusual knocking sound, which may indicate a problem with the machinery system.

7. Abnormal Crankshaft Deflection Readings of the Auxiliary Engine

Any engineer of a ship must take timely measurement of crankshaft i.e. crankshaft deflection with the assistance of dial gauge. If there are abnormal parameters, on levels above the standard limits, then the issue may be in the major bearings or alignment of crankshaft, and they require taking of instant action. Running Hours of the auxiliary engines Last but not the least, any marine engineer must monitor the running hours, because this is of prime importance, to know when the auxiliary engine would require next overhauling.

Piston

Piston is made up of heat resistance aluminium alloy to keep weight down for balancing purposes. Crown bolted to a skirt made of light alloy. Piston crown is Bowl shaped or toroidal shaped. Rim may contain cutout to accommodate the valves when they open.

Piston cooling is achieved by

circulating lube oil underside the crown
Splash or spray
involves oil circulating chambers or coil cast.
cocktail shaker.
piston in two pieces to form precisely cooling chambers below the crown and behind the ring bolt.

Gudgeon Pin in fully floating in both connecting rod small end & piston bosses. It is located endwise either by pads fixed to the piston or by means of circlip into small grooves.

Piston rings

Made up of flake graphite cast iron alloyed with manganese, chromium & 1% molybdenum. In order to seal the gases in the top of cylinder & prevent leakage down the piston.

The pressure of the gas in the clearance space forces the ring down on to the side of the groove and outward on to the cylinder wall. Usually 3 or 4. The top ring sustains the greatest pressure drop across it and it operates at highest temperature. It is chromium plated.

Scraper rings-Unlike the compression ring the oil control rings do not have high gas pressure to force them against the cylinder wall and have to rely on their own strength to generate the wall pressure necessary to keep the oil film to the required thickness.

Cylinder liner

Cylinder liner are made of close grained cast iron, it is cylindrical in shape and flanged at the top end to provide location and securing them in the cylinder block or to the water jacket.
It is pressed down on metal to metal face at top.
A Steel ring the joint between the liner and cylinder cover.
The lower and is fitted rubber rings to form seal for the bottom of the water space and also to prevent oil from the crankcase entering the jackets. A "tell-tale" hole is provided between the upper and lower rings which run outside the engine. It draws attention to the need for renewal of the rings without contamination one fluid to other.
The upper part of the liner bore where the top Piston rings reaches the top of its travel suffers the greatest wear. Because at this point to maintain adequate oil film. Gas pressure is highest forcing it hard against the liner. Top-of-the-line Resort from repeated compression cycles which tend to drive off any oil. Tiny carbonaceous abrasive matter accumulate in the groove around the around the ring leading to wear to promoting conditions.
To reduce wear top part of the liner is kept reasonably cool. Means to promote cooling without sacrificing strength that is bore cooling.
The bores of the cylinder liner have a specially prepared surface designed to achieve the running in of the piston rings and the liner. It is slightly rough in order to retain the oil and promote rapid wear-in. When the Piston rings are renewed the glazed of the liner bore should be broken by honing in order to provide surface suitable for rapid running-in. To provide hard wearing surface some times it is chromium plated which is also porous in nature to provide in an oil retaining surface.

Fuel oil system

For circulation of fuel during stand still of the engine a bypass line is mounted with a non return valve parallel to the feed pump. Each cylinder unit has its own set of injection equipment compressing injection pump, high pressure pipe and injection valve. The injection equipment and the distribution supply pipe are housed in a fully enclosed compartment does minimizing heat loss from the preheated fuel. This arrangement reduces external surface temperature and risk of fire caused by fuel leakage.

Waste oil from the compartment, fuel valve and engine feed pump is lead to a fuel leakage alarm unit consists of a box with float switch for level monitoring. In case of large leakage, the float switch will initiate alarm. The supply fuel oil to the engine is lead through the unit in order to get heated up thereby ensuring free drainage even for high viscosity waste/ leak oil.

Lubricating oil system

The gear wheel type lube oil pump with pressure regulator fitted in NDE through coupling for gear wheel. Draws oil from oil sump and passes the oil through thermostatic valve directly when cold condition and through the cooler and through duplex filter of 60 microns. From where oil is distributed to the following groups from the lubricating point the oil returns by gravity to the oil sump.
The motor driven pre lube oil pump used for standby which is connected from emergency switch board. It runs for 2 minutes intermittently and 10 minutes stand still.
The inlet line to turbochargers is equipped with a fixed throttle to adjust oil flow and non return valve to prevent drainage during still. The non return valve has back pressure function requiring a pressure slightly above the priming pressure to open normal flow.
Lube oil through drilled engine frame to main bearing through bores in crankshaft to lube oil pump drive and connecting rod big end bearing through bored channel in connecting rod to a small end bearing inner circumferential grooves through holes and channels in the Piston pin to Piston cooling.
Lubricating oil pipe for the camshaft drive gear wheel are equipped with nozzles.
Lubricating oil to Governor drive to gear wheels.
Lubricating oil to rocker arm to each cylinder head.
Through a bore in the frame lead to first camshaft bearing and through camshaft bore to other camshaft bearings.

Bottom end bearing bolts

The big and bolts of 4 stroke engine connecting rod are subjected to the following forces:

A dynamic tension loading during the centrifugal force of the masses of connecting rod rotating with the crank pin.
A Dynamic tension loading owing to inertial forces of the reciprocating mass of the piston which is fluctuating with the angular displacement of the crank and having a peak value at an instant of 360° after the firing TDC in a cycle of operation.
A Dynamic shear stress at the parting of the two halves of the bearing housing.

I section connecting rod fulfills this function in the best manner which offer lighting mass but also having sufficient strength.

Light alloy material Piston will fulfill this function in the best manner which offers lighter mass.

Dowel pin with fitted bolts or serration or combination of these are provided at the the parting interface between the two halves of the bearing housing to reduce shear load on the Bolt and any possibility of fretting at the surfaces.

Bolts designed to carry dynamic loading should be constructed out of the material having resilience the material should not be stiffer with respect to the bearing housing otherwise it is likely to carry larger load.

Failure of one of those bearing could lead to total engine failure which brings number of other damages.

The pre-tensioning of the bolts is an important factor which contributes towards the fatigue life of the material of the Bolt. The pre-tension must be kept very high so that the increase in stress owing to dynamic loading remains within the range of stress already given by pre-tension.

Bottom end bolts can be pre-tension by

Using a torque spanner
Turning the nut through specific angle
Using a hydraulic tensioning device
Using an elongation gauge.

While tightening the bolt a good portion of the energy must be used to provide a clamping force between the two halves of the bearings. The first part of the energy applied is used to take up the nip, another portion is lost due to the elasticity of housing and the remaining part only is effective in imparting the desired pre-tension on the Bolt.

The first two methods are not accurate as the frictional forces lost in the thread and the rubbing surface remains undetermined.

Combination of last two methods should be best solution for accurate and predetermined tension of bottom end bolts.

The reversal of trust in the four stroke cause greater cyclic fatigue problem with the bottom end bearing bolts for safety sake therefor running hours given in the manufacture for their bottom end bearing bolt should be strictly adhere to.

Valve reconditioning

The interference angle provided for the line contact between valve head and the valve seat at the largest diameter of the seat so that, even under firing pressure there will be a gap towards the combustion chamber.

First few operating hours annular seat width of approximately 4 mm.

Touching up test

Clean sitting surface Thoroughly.
Apply a very thin coat of touch up paint to the valve head seat and distribute it to obtain a water thin coat.
Insert valve into the cylinder head, turn valve back and forth with the use of touch up tool.
Lift valve out check supporting area (closed ring about 2/3 width).

Reconditioning valves in accordance with findings.

Condition 1:valve seat surface & cylinder head surface clean. Check valve tightness and make touching up test. Contact line at largest diameter of seat should be solid and not interrupted.
Condition 2: face of valve head is not guttered & valve seat is lacquered. Apply coat of fine grinding paste to valve seat and valve head and grind valve on seat until seats are clean. Make Touch up test.
Condition 3: Valve head covered with a thick layer of deposit or valve head seat has corrosion and pitting up to 2 mm long. Coat valve seat and valve head with grinding past and grind valve on seat until corrosion and pitting are removed. Make touch test.
Condition 4: valve head carries a heavy coat of deposit or corrosion pitting of a length of more than 2 mm in valve head seating surface. Seat badly corroded. Re-machine valve head and valve seat with a valve grinder and grind with fine grinding paste. Make touch up test.

Service intervals depending on fuel used charge air pressure extra.

Auxiliary engine overhauling

Safety precautions during maintenance.

Do not open crankcase side cover for at least 10 minute an explosion may occur igniting the oil Mist as fresh air flows into engine.
Revolution of the engine during disassembly or inspection work.

Control handle 'stop' position.
Close valve on air system.
Drain starting air on engine side.
Turn off control power.
When turning the engine, check Rotary section is free.
When working area of the engine disassembled, take the measure to prevent the crankshaft from idle turning.
Put turning device back to disengage position when not required.

Wear protection gear such as gloves hard hat safety shoes in safety goggles.
Engine room floor and surrounding area slippery. Wipe off area & shoe souls.
when disassembling each pipeline set all line valve in closed position loosen air vent plug to release remaining pressure. Filter, joint area of piping to release remaining pressure. Take care of hot oil.
When the spring incorporated valves or devices are dismantled conduct assembly work carefully, since spring can jump.
Don't lift heavy parts use wire ropes and chain blocks. Do not work under lifted things. Check wire rope from brake, twist, specified dimension and weight.
when inspecting and disassembling electrical product turn off power and put a sign.
When handling a liquid strictly observed the following:

Fuel oil & lube oil may be inflammable. Naked light prohibited
Fuel oil corrosive corrosion inhibitor, antifreeze & mercury are poisonous.
Battery electrolyte are poisonous wash away if deposited on skin. Naked flames prohibited.

Precautions for disassembly and maintenance and assembly

Prepare the replacing part tools measuring instrument in advance.
Gaskets, O-rings, split pins, wire rings to be replaced after every disassembly.
Block the openings with tape or clean cloth to prevent foreign matter ingress.
After restoration be sure to remove such tape or cloth.
Place disassembled part in neat order for prevent of damage.
Be sure to assemble with match marks.
Material of the Bolt and nut used in high temperature section such as exhaust manifold are heat resistant, do not mix them with ordinary nuts and bolts.
Tighten each of the Bolt with specific torque or oil pressure.
Measurement of parts to be taken correctly and noted down.
When starting to work, restore the engine by fitting the removed protective cover for thermal insulation covers.
The minded to promptly replenish all the used spare part.

Check items after disassembly, maintenance and assembly.

That all the bolts and nuts are free from loose name and that specified lock washers are inserted securely.
Turn the engine and prime each fluid to check that there is no problems such as interference of the working area and leakages or clogging of each area.
After end of work check, that the flywheel turning device and turning bar used are in disengaged position.
Record the content of the work executed and parts replaced.

Auxiliary engine 4 stroke

Cylinder Block: Being an oil pan type and suspension metal structure made of cast iron constructed box type. The cylinder block builds the boost air chamber, cooling water passage and L.O passage in addition to cam housing.
Crankshaft main bearing and crank pin metal: Crankshaft made of Carbon Steel forging. The main bearing housing firmly fixed to the cylinder block with two mounting bolts and two side clamping bolts.
Piston & Piston rings: Piston made of ductile cast iron. Piston rings consists of three compression rings and one oil scrapper ring.
Connecting rod: Connecting rod carbon steel forging, big end is diagonally split structure, having the serrated mating surface to provide a satisfactory rigidity. The small end adopts a lead bronze Bush.
Cylinder liner: Special cast iron, wear resistance, inner surface precisely honing chemist bore cooling outer periphery cooled.
Cylinder head having sufficient rigidity to take thermal mechanical loads.
Suction and exhaust valves: Four valves Bridge type equipped with Rotocap. Both valves made of heat resistant steel, stellate fitting wall and seat area.
Camshaft: the cam and camshaft is a Monoblock construction.
Cooling water system: Two line cooling system of the engine cooling line. With automatically temperature regulating valve:

Cylinder and cylinder head and the heat exchanger for.
Lubricating oil, air cooling and fresh water cooling.

Disassembly

Detach the bonnet and remove various piping fuel oil HP pipe, leak pipe, Nozzle in-out, cooling water outlet pipe, rocker arm lube oil pipe. Air starting pipe, pilot air pipe etc.
Detach the exhaust and cooling water thermometers.
Remove cylinder air starting valve, Fuel injection valve using extraction tool indicator cock, relief valve etc.
Take off air duct and exhaust manifold
Remove Rocker arm assembly and then rocker arm Chamber. Take off the valve retaining T pushrod and its cover.
Remove the cylinder head mounting nut using hydraulic Jack.
Take out the cylinder head using lifting tool (Strictly observe the standard) chain block and lower the lower it on wooden block. Not to scratch lower surface of the cylinder head. Not to damage O-ring contact surfaces.
Remove cylinder head packing and to be renewed.

Overhaul checks

Check on the state of the carbon adhered on the combustion chamber and suction and exhaust ports.
Attach the valve spring detaching/attaching tool to the fuel injection valve clamping stud. Turn handle hold down the valve rotation rotator and take out cotter. Always use as pair and remove the valve spring. Valve spring and Rotocap can also be removed with removing cylinder head. Bring piston to TDC.
Check the valve spring for crack and corrosion.
Detach Rotocap, disassemble and check interior after cleaning combustion chamber suction and exhaust port. Check for crack by means of color check (cleaner, developer and penetrants)
Inspect inside jackets through cooling water hole. If scale deposit, remove plug and clean inside. Plug to be replaced with lock tight 271.
Check valve guide wear and oval. Example 20mm diameter limit is 0.3mm.
Use seat cutter for correcting seat. measure dimension of valve seat as recommended.
Valve seat can be removed by padding welding on inner surfaces and quenching. Some exhaust valve seat can be removed/fitted by specific tool.
Use liquid nitrogen for fitting valve guide and intake valve seat.
Use liquid CO2 or dry ice for fitting exhaust valve. O-rings damage with nitrogen.
Tappet clearance to be adjusted of concerned cylinder on compression stroke.

Disassembly and assembly of piston and connecting rod

disassembly

Place the Piston 50° before TDC keep waste cloth on Piston upper surface
Remove carbon from the combustion chamber at the upper part of liner.
Bring the Piston to the position of about 55° after TDC
Attach the Piston lifting tool (eye bolt) to the Piston crown and suspend it with the wire rope and chain block.
Using the specific socket wrench loosen four connecting rod bolts and take out three of them first.
Take out the remaining bolt together with the cap
Draw out the Piston and connecting rod by chain block
Reassembly
Set the crank pin about 30° after TDC provide the flywheel lock.
insert the Piston and connecting rod paying attention to the following points:
Use Piston insert tool
Set Piston oil ring by staggering butt and 120°
Face the cut of connecting rod big end with cap towards the maneuvering side. Apply lube oil to the sliding part of the ring and cylinder liner.
Insert Piston, Lever gap of 20mm between connecting rod big end bearing and crank pin, fit the crank pin metal, apply lube oil to metal sliding surface.
Replace connecting rod bolts new one used about 20,000 hrs. Clean the bolts thoroughly and apply lube oil at threaded parts.
Assemble the cap only without metal. Tighten bolts (4 in number) with specific Torque (5 bar) with torque wrench. Punch the match mark on the bolts side.
Loosen the bolt again, insert metal into the cap and assemble it. Tighten the Bolt up to match mark then tighten up to 115° in 3 steps (30°, 80°, 115°. specified tightening angle 115°) tighten the connecting rod bolts after 1,000 hrs. running up to specified torque using torque wrench.

Overhaul checks

Piston and gudgeon pin

Remove the Piston gudgeon pin circlip by circlip plier. Remove piston rings including oil scraper ring By detaching/attaching tools. After cleaning piston rings, all rings to be calibrated (axial thickness, radial thickness, butt clearance).
Check scale adhering in cooling chamber in the underside of the Piston crown.
Clean the Piston by emerging it in wash oil and blow with compressed air.
After cleaning check the Piston by penetrate test for cracks on its top surface, ring grooves (outside and inside) and underside of the Piston, calibrate piston ring grooves tabulate axial clearance renew piston if limit crossed its value.
When incorporating the connecting rod into the piston, match the set mark of the piston with that of the connecting rod.

Connecting rod

Check the serrated surface of the connecting rod big end with cap to see if there is not the wear due to crack, looseness of bolts etc.
Check the connecting rod is small end to see if there is looses in fitting with the gudgeon pin metal nor a crack.
Measure the inner diameter of gudgeon pin Metal. Replace the metal if crosses limit value. Gudgeon pin metal shrink fitted and remove it by hammering.
Measure the bend of connecting rod. (dimension L to be check, if reduced that means connecting rod is bent)

Crank pin metal

Check the current pin metal to see that if there is crack on sliding surface. Measure the inner diameter of crankpin metal after it is incorporated into the connecting rod and bolts are clamped with specific torque.
Metal to be replaced if reached limit value.
If overlay wear off about 30% by sliding area
If thickness differing between a and b (0.04mm or more)
Always replaced by a pair of the upper and lower Metals.
Procedure of checking the crankpin metal without overhauling cylinder head
When engine is in rest, suspend the piston halfway. Turn the crank in about 90 degree

Disassembly and assembly of cylinder liner

Remove the cylinder liner after removing the cylinder head and Piston.
Confirm that water in the cylinder jacket is drained completely.
Place a vinyl sheet or like to receive dirt, foreign matters and water deposits so that they may not drop on the oil Pan.
Install the cylinder liner draw out/ inserting tool. The above tool consists of strong back cross bar eye bolt, jacking nut & spacer.
Turn the jacking nut and draw up to strong back so that lower side O-ring is completely detached.
Now using wire sling and chain block, lift the cylinder liner using eye bolt.

Inspection

Removing O-rings, inspect the outer periphery for cavitation and corrosion.
Remove the scale from cooling water space, including the bore cooling space. Inspect if there is any crack near flange, drilled hole white color check.
Check and repair anti corrosion coating film on cylinder liner outer Periphery.
Clean the contact surface with the cylinder head gasket on the liner upper surface.
Observe the carbon deposited on the cylinder liner inner surface.
Remove the carbon and check the inner surface for scratch, scuffing blow by Mark and corrosion.

Check the outer surface of the protection ring and liner inserting area for corrosion and fretting.
Measure the protection ring thickness with the spherical micrometer and record the result. If crossed limit value, protection ring renewed.
Measure the inner diameter of the cylinder liner using inside micrometer and liner positioning gauge (to know wear rate)

De-glazing of cylinder liner: when the piston is replaced or the cylinder liner inner surface is in the mirror surface condition, dress the inner surface.

Polish the surface with Sandpaper(#80) in the circumferential direction. So the surface may be marked or
Dress the surface by honing so that maybe crosshatch angle of 30°

Match the set mark of cylinder liner with that of cylinder block.
Fit new rubber packing on cylinder liner (not to twist) and coat with white paint.
Again measure inner diameter of liner after reassembly.

Main bearing disassembly

Drain out engine Oil (wet sump type).
Remove crankcase side cover
Unscrew the sidewalls of main bearing.
Turn the crankshaft till the concerned piston is at 90° degree passed TDC.
Attach hydraulic jack to the concerned main bearing studs.
Operate hydraulic pump 600Bar and loosen the clamping nut.
Fix the Jack (pantographic type) & clamp tools to the supporting rail in the oil Pan below the main bearing
Remove the main bearing cap clamping nut and manipulate the Jack to lower the main bearing cap.
Remove the main bearing lower metal.
Insert the upper Metal attaching/detaching pin into the crankshaft hole from the maneuvering side so that the head of the pin comes along the periphery of the crankshaft. Then slowly turned the flywheel in the normal turning direction and pull out the upper metal from the non-maneuvering side . If the clearance between the main bearing metal and the crankshaft journal bearing become larger, the lube oil pressure will drop, resulting in burn out of the metal and increase in the crankshaft deflection, which may include breakage of the crankshaft & other serious accidents.

Main bearing Re-assembly

Turn the flywheel till oil hole visible from maneuvering side.
Attach the upper metal insert tool to the main bearing cap.
Attach the upper Mantle of to the inserting tool.
Insert the attaching/detaching pin from the crankshaft hole on the maneuvering side. Place the pin in contact with the Periphery of the crankshaft with grease it prevents falling.
Manipulate the jack raise the main bearing cap until the metal make contact with the crankshaft.
Slowly turned the flywheel counter clockwise until the end surface of the metal become flush with the end surface of cylinder block.
Lower the main bearing cap, remove pin & inserting tool and attach the lower metal.
Raise the main bearing cap and tighten the cap nut with specific torque.
Remove the Jack tighten the side Bolt.

Disassembly of piston

The cylinder liner upper flange area is of thick wall structure and cooled by bore cooling for the sake of thermal load and cooling water is guided to the cylinder head through the liner support frames attached around the upper outer periphery.
The engine frame and the cylinder liner are tightly sealed with O-ring at both the top and bottom part.
Further the inner periphery of the cylinder liner upper area is provided with the thin wall liner protection ring, for the sake of preventing the accumulation of carbon sludge.
Remove the carbon deposit of the upper areas of the protection ring and the cylinder liner with Sandpaper. Remove the protection Ring with extraction tool. (use plastic Hammer, spray penetrating lubricant to the clearance between liner and protection ring) Measure the protection ring thickness with Spherical micrometer and record the results. Normal size-10.2 mm replace limit 2.5 mm.

disassembly of connecting rod

In case of piston disassemble only, it is not necessary to disassemble the big end part and remove connecting rod palm end from the big end bearing completely.
Turn the crankshaft and place the Piston at BDC .Remove the locking wire of connecting rod palm end Bolts and loosen the connecting rod Bolt to extract it.

disassembly of connecting rod large end part

After extracting of piston
Without extracting the Piston (suspending the Piston). use Piston support Bolt into that thread hole of the Piston upper part using mounting holes of the fuel injection valve.

Disassembly

Turn the crankshaft, and place the large end part at the place near the inspection window with engine frame sitting it sideways
Remove the palm nut for loosening.
Simultaneously loosen the connecting rod bolt and the circular nut using a hydraulic Jack (specific coil pressure 850Bar).
In the state that the large end part is set sideways insert the metal cap fitting and disengaging implement into the underside of large end part
Slowly turn the crankshaft until the large end part lightly contacts with the metal cap fitting and disengaging implemented.
Loose the circular nut with your hand and remove it.
Take out the top and bottom of the large end part from the right and left inspection window respectively (careful not to damage thread of connecting rod bolts)
Remove the crank pin shell from the large end part. Place wooden piece against the claw side of the bearing shell and strike it lightly. Then bearing shell can be removed easily.
Mark the disassembled shells with the cylinder number and ID marks, so that the upper and lower shell can be distinguished from each other.

Tappet clearance

All valves have a smaller clearance between the valve stem and the rocker arm when they are fully closed. Maintain manufactures specified clearance.
Too little clearances causes a valves to stay slightly open at all times and engine heat up and the metal part expand, result loss of Compression, Burnt seat & valve.
Too large clearance, the valve will open slightly late, wont open far enough and will close a little too soon.
By watching the moment of the rocker arms while you slowly rotate the engine, you can determine where in the cycle each piston is, therefore the position of the cam that operates each push rod. Valve clearance to be set when the valve is fully closed at TDC on the compression stroke.
Specific Procedure
In order to find TDC for any cylinder, slowly rotate the crankshaft in its normal direction of rotation. Watch the inlet valve's pushrod as it moves up and down. when it is almost all the way down the piston is at bottom of its inlet stroke. Mark the crankshaft and turn the engine another half a revolution.
Now the Piston will be close to its compression stroke and valve clearances can be set.
Adjustment will have to be made when engine is cold place an appropriate feeler gauge between top of the valve stem and Rocker arm. Tighten the adjusting screw through until the arm just begin to pinch the feeler Gauge and tighten the lock nut.

Crankshaft deflection

If the crankshaft deflection exceeds its limit, the stresses applied to the crankshaft will become excessive, may result breakage of the crankshaft.

Conditions for measuring crankshaft deflection:

Engine is in cold condition, deflection varies with temperature
Record draught, list, cargo (loaded/ballast)
Check the contact of the deflection gauge by pushing with the finger and confirm that the above return to the original position.

Measuring deflection

Open the indicator cock and turn engine.
Place crank pin 30° degree past BDC (Position B)
Install the deflection gauge to the position normally (D/2)
Set the reading on the gauge scale to + 20 at position B (to make clear the positive and negative directions)
Slowly turn the engine in the normal direction of the rotation, measure the reading on the scale when the crankshaft is at the angle of B, C, D, E and A respectively and data recorded.

Calculate the deflection

Vertical deflection, $dx = D-\frac{A+B}{2}$
Horizontal deflection, $dh = C - E$

Adjust the drive equipment using adjusting shim or chock liner, so that the deflection Falls within limit.

Fuel injection valve

Extraction:

Remove the cylinder head cover and heat box cover.
Close nozzle cooling water valve and drain the water.
Loosen the bolts & remove the HP pipe coupling block.
Remove the inlet connector.
Remove the tightening nut using a box wrench.
Extract the fuel injection valve, using a fuel oil injection extracting implement. Remove the circular jacket.

Injection test

Inspecting valve opening pressure

Install the fuel injection valve on the injection test device, after removing the carbon stuck on the tip of the injection valve, and cleaning the tip of Fuel injection valve.

Connect the test pump and fuel injection valve using a high pressure hose for testing.

Quickly operate the test pump liver several times and drain the air until the valve start injection of the fuel as the pressure indicating scale swings.

Slowly turn the test pump lever (once every second), also check the pressure reading (the pressure that has once increased gradually, suddenly starts to decrease due to opening of the valve) normal pressure 320-350bar.

Adjustment valve opening pressure

Remove the cap nut.

Loose the lock nut for the adjusting screw.

Adjust the pressure to the specific pressure by turning the adjusting screw using a screw driver.

Tight the lock nut.

Inspecting fuel oil injection

Quickly operate the test pump lever several times (2-3times/sec) and inspect the fuel injection condition (on a blank paper).

Injection sound, even injection and spray, not of bar pattern nor dripping down.

Disassembling of nozzle

Remove the cap nut
Loosen the adjusting nut
Fix the holder housing in the vice and loosen the retaining nut.
Extract the needle out of the nozzle.
Extract the nozzle out of the retaining nut by striking with a hammer, while placing a pipe type patch on the nozzle, so as not to damage the injecting hole of the nozzle.

Inspecting Nozzle

Clean the nozzle nut and needle valve with gas oil.
Clean the nozzle hole using a nozzle cleaning implement.
Push in and push out the needle valve with your hand. Check the movement is smooth or not check if the moment is too loose.

Assembling

Clean each of the disassembled part with clean gas oil and insert each of them back into the holder housing.
Put the spacer and the knock pin of the nozzle together and install them into the holder housing.
Apply the molykote on the holder housing thread, the seating face of the retaining nut and the outer Periphery of the nozzle and screw the retaining nut into the holder housing.
Loosen the adjusting nut.
Tighten the retaining nut with a specified torque (353-382N-m)
Set the fuel injection valve on the injection test device and adjust the opening pressure.
Mounts fuel injection valve
To the cylinder head in the reverse order of the extracting procedure
Apply molykote on the circular gasket, O-ring, holder housing.
Tighten with specified torque 6 kgf-m.

Troubleshooting

1. Auxiliary engine not turning on air

Insufficient starting air

Insufficient starting air pressure.

Leaks from main stop safety valve on the air bottle
faulty air compressor.
Faulty pressure gauge.

Defective air starting piping system

Close stop valve
Clogged piping

Faulty air starting device

Sticking of starting air operation valve.
Sticking of air starting valve.
Rough seat surface on starting a Rotary valve.

Defective control system

Interrupted power supply
Defective automatic control panel.
Defective/broken new wiring of the electrical contacts for control
Defective solenoid valve for control
Turning device on - turn it off.
Rotation prevention device on - turn it off

2. Engine rotates but not firing on fuel

Not smooth turning

High resistance of moving parts

Cylinder liners Piston
Crankshaft

Too high lubricating oil viscosity

No ignition in all cylinders

Low room temperature
Low cooling water temperature
Degraded fuel oil

Improper properties (Ignitability) use high grade oil.
Water in fuel oil
Air in fuel oil.

No ignition in some cylinders.

Defective fuel injection valve.

Faulty nozzle
Improper valve opening pressure

Defective fuel oil injection pump

Sticking of rack
Sticking of plunger
Faulty delivery valve

Improper fuel injection timing
Insufficient compression pressure

Non air tight piston ring (sticking, worn, damage)
Non air tight intake/exhaust valve
Improper valve end clearance on intake/exhaust valve (tappet clearance)

Flywheel rooted but fuel mixture not Ignited
The normal rotation speed is not reached

3. Generator over speed unable to stop

Defective speed regulator system

Defective governor
Control has come off or is caught.

Sticking of fuel oil injection pump rack.
Defective control power system

Defective control power system
Faulty disconnected contacts.
Defective solenoid valve
Defective speed detector

Defective fuel shutdown system

Defective fuel shut down device
Defective speed detector
Insufficient control air pressure (clogged piping/filter, drop in pressure)

4. Auxiliary engine under study load continuously fluctuating

Defective fuel control system

Defective governor
Control link is caught or shaky

Defective fuel supply system.

Insufficient supply pressure (defective relief valve/pump)
Clogged fuel oil filter - clean it
Water in fuel oil - separate and eliminate water
Air in fuel oil - remove air
Improper viscosity of fuel oil or heavy oil - adjust heating temperature.

Uneven combustion between cylinders

Defective fuel injection valve

Faulty Nozzle
Improve valve opening pressure - adjust it.

Defective fuel oil injection pump

Sticking of rack
Sticking of plunger
Faulty delivery valve.

Improper fuel injection timing - adjust it
Insufficient compression pressure

Non-air tight piston ring (sticking, wear, damage)
Insufficient compression pressure.
Non-air piston (sticking, wear, damage)
Non-air tight intake exhaust valve
Improper valve end clearance on intake exhaust valve (tappet) - adjust it

5. High exhaust gas temperature (exhaust manifold red hot)

High reading on pump rack scale

Overload (excessive torque)
Large resistance on moving parts (e.g seizing)

Cylinder liners, piston
Crank shaft

Improper fuel oil properties

Improper fuel oil viscosity (HO)

Excessively large fuel injection

Improper adjusted reading on injection pump rack scale.
Sticking of rack.

Improper fuel injection timing
Defective fuel injection pump

Sticking of rack
Sticking of plunger
Faulty delivery valve

Defective fuel injection valve

Faulty nozzle
Improper valve opening pressure

Insufficient compression pressure

Non air tight piston ring (sticking, wear, damage)
Non air tight Intel/exhaust valve
Improper valve end clearance on inlet/exhaust valve

Low intake air pressure

Fouled turbocharger (Clogged, pre-filter, fouled blower/turbine side)
Clogged fin for air cooler.
Clogged exhaust outlet.
Negative pressure in engine room.

High intake air temperature.

Facility air cooler (fouled fin, high cooling water temperature, insufficient cooling water)
High intake air temperature - Improve ventilation

Properties of system oil of Aux engine trunk type

(system oil for bearing, running gear and cooling)

Viscosity
Detergency
Dispersancy
Flash point
Alkalinity
Insolubility

Alkalinity to be selected according to the quality fuel oil (sulfur)

Insoluble is fouling substance that do not dissolve in the oil and the main component is soot which is a product product of combustion and Calcium sulphate which is a neutralizing product.

Limit values:

Viscosity
Flash point 180° or higher
Water content 0.3 or less %vol.
n-pentane (Insoluble) 2.5 or less.
BN: 3 or more (D.O) & 10 or more (HO)

Properties of Hydraulic machinery oil

Viscosity
Viscosity index
Pour Point
Flash point
Detergency/Dispersancy
Antioxidation
Slight Alkalinity.
Anti-foaming
Anti-corrosion

Lube oil Test kit:

Viscosity
Water contents
Salt water
Total base number
Strong acid
Insolubles

Questions:

Main bearing lower shell removal procedure and precaution for aux engine?
Crankpin oval ?what will be the remedial action?
Your 4th engineer overhauled the aux engine & he tried the generator ideally? then as a 2nd engineer how you will take it onload?
One unit of aux engine showing more exhaust temp and other unit having less exhaust temp after decarbonization? what may be the reason & how to rectify?
Aux engine Lube oil pressure dropping slowly, what are the possible reasons?
Conventional generator main bearing removal procedure the one which in crankshaft is not underslung.
What is provision in aux engine main bearing which prevent it from turning (Notch on bearing n hole on keep)
How to check Aux Engine fuel pump timing?
Three criteria of aux engine valve grinding?
How to remove and put aux engine exhaust valve seat?
Aux engine liner renewal criteria?
Lube oil test of aux engine?
Aux generator hunting reasons?
Aux engine one unit piston is stuck, how will you remove?
Aux Engine Bottom end bolt what precaution while overhauling?
After decarb, how the generator units are balanced. balancing is done in no load or on-load condition, how pressure is adjusted?
How timing of fuel pump is adjusted, for advance we add or remove shims, where shims are fitted with diagram?
Aux engine peak pressure adjustment procedure
Aux engine fuel pump zero setting?
Aux engine cylinder head overhauling and clearances. Trueness of exhaust valve stem how you will check.
How thrust is taken in Aux. Engine?
How to check tube leaking of A/E lube oil cooler?
Which cycles does 2-stroke main engine and 4-stroke aux engine follow? a. diesel b. Otto c. dual d. miller
Precaution during changing fuel pump of aux engine?
Aux engine one unit exhaust temp going low reason ?

Comparison of 2 and 4 stroke cycles.

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