ASSEMBLY AND OVERHAULING OF FUEL PUMP OF AUXILIARY ENGINE ON SHIP

THE PROCEDURE FOR OVERHAULING A FUEL PUMP OF AUXILIARY ENGINE ARE AS FOLLOWS:

1.Dismounting of fuel injection pipe.

1) Remove the high pressure pipe.

2.Dismounting of Fuel and Drain Pipes

2) The lock ring (1), see fig 2 must be shifted into the groove in the center of the pipe.
3) Push the fuel and drain pipes into the adjacent pump until the injection pump is free, see fig

3.Removal of Fuel Injection Pump

4) Separate the spring loaded lever from the regulating rod on the fuel injection pump.

5) Remove the screws in the bottom flange and take the fuel injection pump away.

4.Disassembly of the Pump Element

1) Loosen the 4 nbs. holding screws (63)
see fig
2) Press in the roller  (26) by means of the installation device, see fig .

3) Screw off the blocking screw (349) which is the locking arrangement for rollar and pump spring .

4) Loosen the spring force and demount the installation device.
5) Take off the roller (26) and the roller pin (38).
6) Loosen the 2 nbs. Bolts(63) and take off the roller guide(51).

7) Pull out the thrust piece (171).
 afterwards the pump spring (291), the spring plate (205), and control sleeve (266).

8) Turn the injection pump vertically by 180 degrees.
9) Loosen the cylindrical screws (421)

10) Remove the delivery socket (230) and the pressure valve complete(122)
14) Screw off the buffer bolt (242) which are two in nos on both side, it is the locking arrangement for plunger.

15) Carefully take out the pump element (87) with plunger and barrel

INSTALLATION

16) Pump elements can be exchanged as component groups only. (plunger and barrel).

17) Insert the barrel (99), see fig 1 carefully into the injection-pump casing (229) with an aluminum arbor and a non-fuzzing cloth to protect the high-pressure surface, and screw in the blocking screw (349).Tightening torque 5 Nm.

18) Further assembly see under "Exchange of pressure valve".
19) Turn the injection pump vertically by 180 degrees.
20) Install the control sleeve (266) - care for the marking! - control sleeve (266) milled tooth, control rack (254) groove around circumference.

21) The further assembly is carried in reciprocal order of disassembly (driving pin of the plunger in the direction of the slot of the control sleeve).
22) Marking on the driving pin, installed towards the boring of the control rack.

WORKING AND CONSTUCTION of auxiliary engine fuel pump

 JERK TYPE FUEL PUMP(B&W) make.

LETS TALK ABOUT CONTRUCTION OF FUEL PUMP                                                                     

The figure shows a fuel pump parts which is used in auxiliary engine of ship.The part no 87 shows a pump element complete, which consists of plunger 109 which resciprocates in barrel 099.

The key on the plunger fits over the sleeve 266. The sleeve on the outside has pinion  machined on it ,which engage with the rack. In this way the the plunger may be rotated by movements of rack. 

The lower part of plunger sits on the sloted peice 183 and thrust piece 205. The pump spring sits 291 sits on the thrust peice 205. The thrust peice 205 sits over the top of rollar guide 051 . The rollar pin 38 engages the rollar 26 to the the rollar guide 051. 

As the fuel cam rotates ,the rollar moves up . As the rollar is connected to rollar guide the rollar guide moves up with the thrust peice and compresses the spring ,and moving the plunger in barrel up . As the cam comes to base circle ,the spring force brings back the rollar to the base circle of the cam with the plunger to move down. The trailing flank of cam brings back the plunger to the bottom of its stroke to allow the chambor to refill. The plunger and barrel assembly house in the pump casing 229. 

The top part of the fuel pump is the constant pressure valve 146 in pressure valve housing 134. It is a non return spring loaded discharge valve arranged to reduce pressure on its discharge side as it closes ,ensuring positive Closing of the fuel injector needle and reducing Cavitation within the pump. 

Function of contant pressure valve- 

1.When the plunger of the fuel pump moving upwards the pressure of fuel keep on increasing , and at a time when it covers the spill port  the injection commences. But the time when short circuit take place that is  when helix comes in contact with spill port  so sudden pressure drop above the fuel pump plunger, so due to this the high pressure oil in the pipeline after the fuel pump try to come back to fuel pump.  But it is not possible because of discharge valve is of non return type. This high pressure oil then gets trapped into the high pressure line after the fuel pump and this high pressure fuel can lift the needle valve and  secondary injection can take place so this is the reason we have stagnation control valve.  This is a control valve which will not open during normal injection but if there is a high pressure on the discharge side then it will open and will maintain a constant pressure Above and below the high pressure pump . 

2.After the end of the delivery stroke as the plunger moves down and still it cover the spill port ,so no oil is present above the plunger, because fuel is not coming from spill port to the upper side of the plunger so whatever oil is present it start boiling because vaccum is created on top of the plunger so Cavitation can occur which can damage the plunger so in this case stagnation control valve helps and give oil from the high pressure line to the upper side of the plunger so that the space above the plunger should not go to  vaccum.

NOW LETS SEE HOW FUEL INJECTION TAKE PLACE.

A helix is machined on the plunger. The barrel has two ports one for inlet of the fuel oil and other is spill port . Let mark two points in helix- mark A the top part and mark B the lower part of helix. See the diagram above. 

As the plunger is moved up by the cam .

Start of fuel delivery -when the mark A of helix is alligned with the inlet and spill port. The pressurized oil above will go to the delivery valve and injection take place.

End of fuel delivery- when the mark B of helix alligned with the spill and inlet port. This allows the fuel pressure above the plunger to fall because the oil is given a path through the vertical slot and spill port.

The quantity of fuel delivered is regulated by the vertical lenght of helix where it is in line with the inlet and spill port. This setting may be  altered by rotating the plunger via sleeve 266 through rack and pinion arrangement. The rack is connected to the governor which moves the rack depending upon the load on the engine.

The fuel cam is designed to raise the plunger at the rate required to build up fuel pressure and maintain this for the corresponding period to operate the fuel injector . Since the pump only discharges on its upstroke ,only one flank of the cam operates the timing. The trailing flank of the cam returns the plunger to the bottom of its stroke to allow the chamber to refill.

Oil supply to the pump suction is by means of a continuously operating supply or surcharge pump which causes flooding of the fuel pump chambor as soon as the suction port is uncovered by the plunger.

TAPPET CLEARANCE IN AUXILIARY ENGINE ON SHIP

Alignment of valve tappet clearance

1. Dismantle the cylinder cover.
2. Turn the crankshaft until the cylinder in question  is in TDC position. The valve push rod must rest on the cam circle.
 3. Clean the surfaces, if required.

 4. Insert the feeler gauge (P3 = 0.01 mm). See fi gure 1.
5. Fix the torque spanner (P4) on the coupling of the socket wrench (P2).
6. Attach the socket wrench (P2)
7. Attach the socket wrench (P1)
8. Tighten the adjusting screw with P1 until the feeler gauge is fi xed without clearance.

Note ;Check with the feeler gauge that the clearance is between 0.01 and 0.02.

Adjustment of inlet and exhaust valve clearance.

1) Take all safety precaution before ( like take out from standby , close the breaker , close priming pump etc)
 1) Clean the surfaces, if required.
2) Insert the feeler gauge (P6), see figure 3.between the inlet rocker arm and inlet valve bridge or between exhaust rocker arm and exhaust valve bridge.

 Feeler gauge (P6):
 - L16/24: 0.4 mm inlet valve
 - L16/24: 0.5 mm exhaust valve

4) loosen the lock nut of the the rocker arm by open end spanner
4) Tighten the adjusting screw with screw driver(P5) until the feeler gauge is fixed without clearance.

6)Now Tighten the nut with spanner and keep the adjusting screw in position by means of the screw driver(P5)
7) check by feeler guage the suction valve clearance as 0.4mm and exhaust valve clearance as 0.5mm.

ON THE 3 location clearance in measured as shown 1 ,2 ,3 in diagram

1-between inlet valve bridge and one inlet valve spindle( for alignment of tappet by filler guage of 0.01mm)
2 -mostly between rocker arm and valve bridge.(by feller guage 0.35 and 0.45 mm ,in between one rocker arm and valve bridge of 2 inlet valve and other in other rocker arm and exhaust valve bridge of 2 exhaust valve)
3- Between rocker arm and push rod(rarely)

Note
The feeler gauge must be clean and inserted as equally as possible between the adjusting screw and the valve bridge. The valve clearance of inlet and exhaust valve is 0.6 mm for a cold engine .
 - The spanner must be placed straight on the hexagon lock nut.
 - During tightening the feeler gauge must be moved from side to side, however, it must stay between the adjusting screw and the valve spindle. The screw is tightened until a slight squeeze can be felt. The rocker arm must be pressed against the tappet during the adjusting process to remove the clearance.

Risk advice:
 - Danger of slipping during adjusting process.
Attention: Risk of hand/finger injury.
 - Risk of injury because of sharp-edged feeler
gauge. Attention. Do not put your fingers between adjusting screw and valve spindle.

HONING OF CYLINDER LINER IN SHIP

Honing the Cylinder Liner


When we are going to insert a new liner it is mirror finished,if oil is added it will slip and effective lubrication will not be there . So wear of liner will take so to prevent it honing is done to make a honing groove so that the the oil can retain in liner.

 In order to obtain a round cylindrical cylinder liner a factory honing is required. A honing as described below can only be regarded as a second best solution and might have an impact on the time between
overhaul as well as on the lub. oil consumption.Renovation is made in the workshop.Prior to honing, deposits of coke and possible wear edges at the top of the liner must be removed by scraping.
A used flame ring must be used during the honing process.
The used flame ring must be cleaned in water. Subsequently, the flame ring is remounted in the cylinder before carrying out the honing process.
Note: Upon completion of the honing process the used flame ring is discarded. A new flame ring is always mounted in the cylinder when replacing the piston rings.

The honing is made by means of a flex-honer with grain fineness 80-120. A revolution speed between 80 and 160 rpm is chosen.In order to achieve a required angle between honing grooves, see fig 3, the vertical speed is adjusted to about 1 m/sec. which corresponds to about 2 sec.
for one double movement (the flex- honer is led from below up and down in 2 sec.)
The procedure must be continued until the cylinder wall is covered by honing grooves and the surface has a slightly matt appearance without any signs
of glaze.During the honing it is important to lubricate freely with honing oil or cutting oil.After the honing, the liner is carefully cleaned with gas oil. Make sure that all abrasive particles are removed.

LT WATER COOLING OR CENTRAL WATER COOLING SYSTEM AND COOLING SEA WATER AND SERVICE SYSTEM ON SHIP

Please don"t refer to the old books there they have shown the diagram of system which was used in 90 s .i have sailed on 2013 built ship and all modern ship nowadays uses this type of system which i will show you in my blog with practical explanation.

The corrosion and other problem associated with salt water circulation can be minimized by using central cooling system which uses a LT water which is a distilled water  produced from fresh water generator  with additives added in it.

NOW first take a look at S.W and service system on ship and then we will go into LT cooling water line diagram on ship.

The diagram shows a SW  system on ship.
The sea water is drawn from( high sea chest when the ship is in port and from changeover to  low sea chest when the ship sails away from port in high seas) sea chest through filter . The sea chest are incorporated with filter ,air vent for purging , MGPS (marine growth prevention system), drain hole. The all sea water system is on bottom platform .
 From the sea water manifold the sea water is distributed for various purpose. Many pump such as
1.sea water pump for cooling.
 2.ballast pump for ballasting and de ballasting .
3.fire and gs pump for fire fighting and deck washing.
4.fire and bilge pump for de ballasting aft peak tank , for pumping out bilges during an emergency (rare)  and pumping out cargo hold bilges by the help of eductor
5. Ejector pump for fresh water generator.

In dia you can see all this pump are connected through a common manifold line
Now we are interested in sea water pump only ,we have two s.w pump which take suction from sea water common manifold with changeover arrangement. The sea water pump with a pressure of 3.5 bar approx send sea water to a height to

1. No 1 & No  2 F.W cooler or central cooler
2. Sewage treatment plant.
3. Atmospheric condensor.

And finally after cooling all this equipment it goes overboard.


Now lets talk about LT F.W cooling system line diagram.

As you can see in diagram the LT water i.e distilled water with additives is circulated all around the ship equipment to be cooled.
As the temperature of water is low around 35 to 50 degree than a HT water cooling system which is around 70 to 84 degree celcius ,so it is called low temperature cooling water system.

The low temperature water after cooling all equipment and machine onboard gets heated up and comes to LT F.w Cooler. Here the LT Water is cooled by heat exchanger by sea water on one side . A pneumatic controller continuosly control the LT Cooling water outlet temperature to around 40 degree. If suppose when the ship is in port only air condenser , reefer condensor ,air compressor , 1 generator is running ,so after cooling only this machinery the temperature of LT water will be less . In this case the bypassed to cooler valve is closed see dia.
When the ship is sailing all the machinery are running such as air cooler of ME, lube oil cooler ME , ME jacket cooling water , All the 3 generator etc. In this case the LT water temperature will be high enough, so the  controller will open the bypass valve to cooler so that the LT water will be cooled by the LT FW COOLER.
Now lets talk about all the equipment which is to be cooled by LT water;
 The LT water after LT F.W cooler passes to 3 pipeline:
They are
1.First pipeline goes to cool Engine control room condensor , main air compressor for intercooler, accomodation air conditioning,  bridge control room condensor . All this after cooling meet at a point 3 as shown in figure.
2. Second pipeline is divided into again 3 pipeline. 1st pipeline for ME LO COOLER after cooling it ,it than goes to ME Jacket FW cooler (check my blog HT COOLING FW system). 2nd pipeline goes to cool ME air cooler and the 3rd pipeline goes to cool Intermediate shaft bearing. All this 3 after cooling meets at a point 1 as shown in figure.
3. The third pipeline goes to cool all the 3 generator on ship. The outlet then goes to LT expansion tank. After cooling in generator the outlet goes and meet at point 2 as shown in diag.
The outlet of LT expansion tank meets at point 4 in the diagram.

The LT cooler PUMP than suck the heated water from all  1 ,2 ,3 ,4 point and leads the water to LT FW cooler. This is how the circuits complete.
Note we do not have any controller in sea water cooling circuit.

Thus we can conclude there are 3 circuits 
1) HT JCW FW COOLING
2)LT FW COOLING SYSTEM
3)SW COOLING SYSTEM.

ADVANTAGE OF ALL THIS SYSTEM LT/HT FRESH WATER COOLING ARE AS FOLLOWS;

1. Low maintenance cost -as the system runs with fresh water the cleaning ,maintenance and component replacement reduces .
2. Less corrosion
3. High speed of fluid hence better heat exchange . Higher speed is possible in fresh water system which results in reduced piping and low installation cost .
4. use of cheaper material since corrosion factor decreases, expensive material are not required for valves and pipelines.
5. Constant temperature level maintained -since the temperature controlled is irrespective of sea water temperature, stable temperature is maintained which helps in reducing machinery wear down ,due to thermal expansion if different maintained as for ex in sea water cooling system.
6. Less wear of engine parts - less wear of cylinder liner as the jacket is maintained warm avoiding cold corrosion.
7.  Ideal for unmanned engine room the greater reliability and temperature controlling of the system offered by central cooling system.

 DISADVANTAGE

1.high installation cost
2.limitation of low temperature

LINE DAIGRAM and explanation OF HIGH TEMPERATURE cooling fresh water system on ship

Please dont refer to the old books. There they have shown the diagram of system which was used in 90s . I have sailed on 2013 built ship and all modern ship nowadays uses this type of system which i will show you in my blog with practical explanation.

The main engine during  running produces lots of heat,this heat is tranferred to the jacket water . In my ship jacket water was used to cool cylinder liner ,bore cooling for cylinder cover , exhaust valve and in some engine fuel injector and turbocharger. But nowadays the turbocharger and fuel injector are designed in such a way that there is no need of coolant .

The cooling water enters at the lower end of the cylinder jacket at a temperature of around 74 degree celcius,passing up to connection from top of the jacket to the cylinder cover and then to the exhaust valve cages and seats. In some engine restricted amount of water is used for cooling turbocharger cooling spaces.

As you can see in diagram the heated jacket water at a temperature of 80 to 82 degree celcius comes out of the engine, there is an auto vent valve which release the air from the high temperature water. If the main engine is not running due to in port stay or anchor ,the jacket water is preheated . The preheating is done because of 2 reason

1. It elimates the condenstion of water vapour in the products of combustion because at low temperature dew is formed in liner and after it react with sox of combustion it will form acid causing corrosion wear in liner
2. At low cooling water temperature the liner wall will be cold and now as the engine is started the cylinder oil is injected into the liner and As the liner is cold the cylinder oil will not be heated and its viscocity will be increased and thus difficulty is starting the engine .

For preheating we have ME JW preheater pump and JW preheater . Steam is passed in ME JW preheater to heat the jacket water . During at port stay or anchor, preheater pump is running , JC FW pump is stooped , JW cooler and FWG is bypassed .

When the ship is at sea-sailing , the preheater is bypassed.  The high jacket water temperature at 80 degree passes the fresh water generator ,where most of its heat is utilized in heating the s.w in heater of FWG.
The temp inlet to FWG is controlled by controller to about 82 degree . After utilizing the heat the outlet temp of FWG is almost 78degree celcius . After that it goes to the jacket water cooler where some more heat is dropped here . The outlet of the cooler is automatically control to about 75degree.

If suppose FWG is not running then all jacket water will go to the cooler i.e no bypass from cooler . If FWG is in use then it is already gave up some heat to FWG so some amout of water is bypassed from cooler because no need of cooling any furthur in cooler as it is already got cooled in FWG.

Now after cooler it goes into deaerator tank where some air +water goes into the HT expansion tank ,which is located at top platform that is in boiler platform. Now after removing air and expanded in expansion tank  the jacket cooling water goes to the lower side of  deaerator.
From the deaerator the jcw goes to  the suction side of pump.

 The HT expansion tank has many purpose such as:

1. The temperaure of water is very high and there may be chance of air lock in the system . If the air is not released from the system then the HT pump or JCFW pump will draw air from the system and failure and the main engine will shut down automatically .
2. Provides a low pressure point for the addition of make up cooling water . If suppose before the deaerator the water  is blocked or leaked completely ,so the pump will run dry . so it can act as a makeup of cooling water and the supply of water to the pump and the engine doesnt stop.
3. Allow in increase in water volume as the engine warms up and air is released from the system .
4. Is designed to maintain a constant head in the system so that the pump doesn't lose suction.

Now after cooling in FWG and JCW cooler the temperature drops to 74degree . The coolant jcw now enters at the lower end of cylinder jacket and this  process continues.

The cooling media in jacket water cooler is from the LT cooling FW system. One line from LT cooling FW system is taken for jcw cooler of ME.

Check my blog for LT COOLING FW system on ship.

FUEL OIL LINE DIAGRAM AND EXPLANATION IN SHIP

Engineers must be well conversant with fuel oil and lube oil installation onboard and various associated functions such as bunkering ,transfer, purification ,combustion and disposal . Fuel oil are carried in tanks in the vicinity of the engine room. For daily use oil is first transferred by the transfer pump to the settling tank and then brought through purifier clarifier to the service tank.

 Fuel oil is then handled by the supply and circulating pump and finally by the fuel  injection pump . All pump, filter ,heaters and purifiers are in duplicate with change over arrangement to ensure non stop service .

Separate service tanks are provided for Diesel oil and boiler Fuel oil. Tanks are also provided for receiving overflow, drain oil and dirty oil and sludge. Sludge may be disposed of by burning in the incinerator or by pumping to the Shore reception facility .

Leakage into the bilge is prevented by use of drip tray under various equipment. 

Steam heating coils are provided in all tanks to reduce viscosity before pumping .Steam heaters are used before the fuel oil is used for combustion engine or boiler. Steam traps are provided on the return line of the steam line, so that the latent heat in the steam is fully utilised and only condensate Water Return To The Hot Well. In case of any leak in the steam coil ,may find its way into the hot well and then to the boiler ,to avoid this contamination condensate is lead to an observation tank where oily is  separated and then and can be seen through sight glass . Watch the tank regularly if oil is found on the surface it should be led to the drain oil tank by opening appropriate valve. Leaky coil is identified and isolated to prevent for the furthur contamination. While heating temperature of the oil should not be more than 10 degree Celsius below the flash point. 

Oil tanks are provided with overflow pipes leading to the overflow tank. There is no valve on this lines . Ensure that the overflow tank is empty during starting bunkering or oil transfer.  Watch the sight Glass on the overflow line.  Stop filling the particular tank if oil is seen in the glass. Air vent of the tanks are above  the level of the overflow pipes. Wire mesh are fitted to the air vent to act as heat and Flame arrestor .outlet valve of all tanks other than those below the engine platform are of quick closing valve type with arrangement to close them from a position outside the engine room. this valves should be periodically tried out . Drain valves are of self closing spring loaded type they remain open only till the operator press the handle. sounding pipes for tanks below the engine room are fitted with weighted cock .

  BUNKERING

 -The bunkering plan should be displayed at the bunkering station . Study the SOPEP manual and take precaution to avoid oil spillage on the Deck and into the sea . Record sounding at all times . Overflow tank must be empty.  Decide the quantity to be taken and tanks to be filled. Maintain communication with the shore bunkering station and duty officer. Keep firefighting appliances in readiness. Connect the Shore pipeline to the bunkering land with proper joint between flanges . Open appropriate valves and start receiving the oil.  Do not fill the tank to full capacity as there maybe possibility of overflow. If one tank is nearly full ,open the valve for another tank before closing the valve of the first tank . Inform the shore station to stop pumping when the required quantity is taken on board . At the end blow through the pipeline to remove the remaining oil . Keep taking sounding of the tank to ensure proper flow to the desired tank. Determine the quantity of oil received on board . Take sample of oil while receiving Bunker and seal the bottle for use in case there is any dispute later. Note the property of oil particularly specific gravity ,viscosity , Flashpoint, calorific value ,sulphur content ,pour point, ash content etc. Test certificate issued by an independent accreted agency is accepted after the Shore pipe is disconnected . Blank the bunkering connection

Oil transfer 

Ship fuel oil transfer pumps are used for transfer  oil from one tank to another . separate pumps are used for heavy oil and diesel oil . Daily routine includes transfer a fuel from bunker tank  to the settling tank by the fuel oil transfer pump and then from the settling tank to  service tank through the purifier . This tanks are in duplicate and arranged transversely while transferring there should be a minimum effect on the list of the ship. Screw or gear pump ars used for oil transfer this are positive displacement pump and hence should not be started with discharge valve closed . Pressure regulating valve are fitted on this pump  that maintain constant pressure on the discharge side access  oil is returned to the suction side for recirculation. Efficiency of the pump depends on the radial and axial clearance of the gear or screw in the casing . Pumps can be stopped by pressing emergency control located outside the engine room . 

Plain wire mesh cartridge Turbo and autofilter auto clean filter used. Cartridge require cleaning regularly . Auto clean filter are cleaned  while  in use by  turning the knob  on top of the cover . Impurities collected the bottom of the casing  can be removed by opening the bottom plug, when the oil circulation in stopped . For change over of filter there is a motor mechanism which rotate the filter arrangement from 1st to 2nd filter and air valve is opened to wash the 1st filter and then close the air valve. Now 2nd filter is in use and 1st one is isolated . Timing of operation of motor is controlled by the pressure difference between inlet and outlet of the auto back wash filter. If the difference is more than the motor operates and auto changeover from 1st filter to 2nd filter take place ,with washing of 1st filter and 2nd filter in use.

Oil purification 

Oill is first pumped into the settling tank and stay there for about 12 hours. Water settles down to the bottom of the tank from where it can be removed by operating drain valves . Oil then passes through centrifugal purifier to remove water and sludge . Clean oil passes to the service time for use in the engine. Gravity disc in the purifier is chosen according to the seperation gravity of the oil . 

Fuel oil routines 

Fuel oil consumption is recorded from noon to noon from the flow metres and service tank sounding. As a routine service tanks are normally change over at noon. A typical routine for filling the tank and keeping them ready for the next day is given below 

1. At 12 noon note sounding of both service tank. ensure that the tank is treated to about 80 degree Celsius and there is no water in the oil. check by opening drain valve. 

SOME IMPORTANT POINTS

1. Settling tank fuel oil can also be sent to fuel oil supply unit of engine that is to the f.o supply pump .check no 1 valve in diagram.

2. No 1 HFO purifier supply pump can send fuel oil to no 2 HFO purifier Heater and vice versa.check no 3 valve in diagram

3. HFO Purifier heater can be bypassed and can directly send oil to purifier .check no 2 valve

4.we can bypass the HFO purifier heater and can send oil directly to settling tank if suppose there is a problem in heater. Check no 4 valve in diagram.

5. No 1 and No 2 fuel oil supply pump and circulating pump for G.E and M.E can be auto change over if pressure in the system falls.

6.In between fuel oil supply pump and f.o circulating pump there is a relief valve to maintain a desired pressure at outlet of both the pumps.

7.In steam line ,outlet line all steam valve are of non return type and thus have y type stream trap with strainer and cock.

8. HFO auto filter (35micron), they are turned by turning the spindle.

9. The oil return from ME and GE goes into the cock which diverts the oil to venting box or service tank. See diag

10.From venting box oil goes to the suction side of circulating pump at pressure of 6 bar.

11. Supply pump pressure is 4 bar and circulating pump pressure is 6 bar.

12. Venting box has automatic deaerating valve ,the venting of HFO goes through a sight glass and is drained  to overflow tank. Thus there is prevention of air lock into the fuel oil system which can be due to dissolved water in fuel or from the supply pump suction side.

13. All supply and circulating pump has safety valve to lift.

14. The discharge line of safety valve is connected to suction line of that pump.

15.Fo high pressure pipe leakage alarm (high leakage drain box alarm level)

16. The return oil from fuel valve and pump is led back to the venting box and then to the suction side of circulating pump.

INSPECTION AND MAINTENANCE OF VALVE SEAT/VALVE GUIDE/ROTACAP/CYLINDER HEAD/PISTON/PISTON CROWN/CONNECTING ROD/CONNECTING ROD BOLTS/MAIN BEARING SHELL/CRANK PIN SHELL/LINER/PISTON RING after overhauling an auxiliary engine in ship.

AFTER OVERHAULING an AUXILIARY ENGINE various measurement and inspection of all parts of engine is done. The DETAILS are given below;


1.Inspection of Valves/Valve Seats

-If the valve seat is burnt or scarred, it should be ground using a valve seat grinder, please see working card
505-01.10.

2.Inspection of Valve Guide

Too much clearance between the valve spindle and the spindle guide may cause:
 - increased lub. oil consumption.
 - fouling up of the spindle guide and thus give the risk of the sticking of the valve spindle.
1) Clean the valve spindle guide.
2) Inspect and measure for wear.
 If the inner diameter of the valve spindle guide exceeds the tolerance, please see page 500.35,the valve spindle guide must be replaced.Please see working card 505-01.20.

 Too much clearance also means insufficient guidance of the valve spindle, and thus bad alignment between the spindle head and the valve seat ring.

3.Maintenance and Inspection of Rotocap

Dirt, especially in the ball pockets due to residues in the oil (abrasives, combustion products), can cause the individual parts to become stuck, and interrupt the movement of the balls.Under normal operating conditions rotocap valve rotators need no servicing.
Rotator performance is satisfactory when the valve rotates visibly and evenly.

3.Inspection of Cylinder Head Cooling Water Space

 1) Inspect the cooling water inlet at the bottom of the cylinder head, see fig 1.
2) Remove all possible deposits.
3) If necessary, clean the cooling water inlet and cooling water outlet, see fig 1 with a steel brush.Flush the cooling water space after cleaning.
4) Should the cylinder head cooling water space, contrary to expectation, be blocked with deposits, please contact MAN B&W Diesel.

4.Inspection of Piston

1) Remove the piston and scraper rings.
2) Clean the piston on the outside and on the inside.
3) Inspect the piston ring and scraper ring grooves for wear.
4) condition of carbon deposits on the piston and lubricating condition , scratch and abnormal contact of sliding areas, condition of carbon sludge deposit on the Piston underside ,abnormal contact of the Piston pin and pin Bush inner surface.
Check of Piston Bolt Tension
4) Apply a torque spanner to the piston bolts, adjusted to 20 Nm.
5) Turn the torque spanner.

Maintenance- clean all parts, blow air to oil hole and clean inside of the hole, perform inspection for crack by means of colour check.
Measurement -
1)Piston outer diameter using an external micrometre at four places .
2)clearance between cylinder liner inner diameter and Piston outer diameter 3)Piston pin outer diameter and Piston pin Bush inner diameter.

5.Inspection of Piston Crown

For cleaning and inspection of the piston crown, it must be disassembled.

6) Loosen the bolts and remove the piston
crown.
7)check for cracks by dye penerant test.

7) Clean carefully the piston shirt and piston.The piston crown must be scrapped if:
A) The wear limit on the testing mandrel is exceeded, see fig 1A
 or
 B) The clearance between the new piston/scraper
ring and the ring groove is exceeded, see fig 1B.

Note: At each piston overhaul:
 - The piston and the scraper ring must be
replaced.
 - The cylinder liner must be honed according to the instructions.
 - For position and fittings of piston rings,
please see working card.

6.Cleaning of Connecting Rod

1) Clean all machined surfaces on the connecting rod.
2) Degrease the joint faces, holes and connecting rod screws with a volatile solvent and blow dry with working air.
Visual Inspection of Faces
3) Inspect the joint faces.Damages, in the form of visible wear marks and pittings or even cracks, may be in the joint faces due to relative movements between the surfaces.
 Wear marks and cracks are visible, but not
perceptible with a fingernail. Pittings and impact marks are both visible and perceptible. Dent or peel of the threaded areas and seat surfaces of the connecting rod joint Bolt. Check by dye penetrant

5) Carefully smooth single raised spots in the serration caused by pitting and impact marks with a file.

7.Inspection of Connecting Rod bolts

6) Inspect the connecting rod nuts for seizures in the threads and pittings on the contact surfaces of the screwheads.
7) Turn the connecting rod nuts onto bottom position of the bolts.

Measurement of Big-end Bore

For check of ovalness the bearing cap has to be mounted onto the big-end bore without bearing shells.Fig 1 Point of measurement

8) Mount the bearing cap onto the connecting rod by means of the connecting rod bolts.
9) Tighten the bolts with the prescribed pressure, please see working card .
10) Measure five different diameters in the groove of the boring.
11) Register the measurements.
12) Calculate the maximum ovalness as the difference between biggest and smallest diameter measured.
13) Check if maximum ovalness is exceeded
Example of Measurement Results
 (in case the specified maximum ovalness is exceeded, contact MAN Diesel for overhaul).

For connecting rod No 1 in the example the maximum ovalness is 0.02 mm and thus reuse is acceptable.
For connecting rod No 2 in the example the maximum ovalness is 0.125 mm and therefore the connecting rod is rejected.

Connecting rod bolt  rejection criteria
-Loading of connecting rod bolts of 4 stroke is more severe than two stroke engine as RPM difference 100 and 1200 RPM.
- the centrifugal force and gas force Set up bending and shear stresses in the bolts ,as a result fatigue failure occurs in bolts.
-bolts should be constructed of material having high resilience and should not be stiffer with respect to bearing housing .
Subroutine checks on this part are the (rejection criteria of the bolts )

-check the corrosion by acidic Lube oil discard if any present on shanks.
- check the length of the Bolt against a new or Bolt tolerance it longer yielding of the material should have taken place renew the Bolt in this circumstance.
- check for mechanical damage especially on shanks .
-check for fracture by non destructive test --

-check the landing phases for an uneven tightening .
-discard the Bolt when either designated life, over speed failure or piston seizure has occurred.

8.Inspection of Connecting Rod Bush

14) Inspect the surface of the piston pin and the connecting rod bush.
15) Measure the clearance between the piston pin and bush.
16) Check if max clearance is exceeded
 If the specifi ed clearance is exceeded, con tact MAN Diesel for replacement.

9.Inspection of main bearing shell for big end bearing 

1)check for Cavitation erosion.
2) scratches due to foreign material .
3)scoring deep replace wearing .
4)Fatigue rupture.
5) check for tin oxide corrosion due to water in Lube oil, tin oxide is formed which is hard and brittle with high load this layer can break at high bearing temperature and melt it and failure of a by wiping.
6) wiping of bearing surfaces due to lack of oil -too small bearing clearance.

10.Inspection and maintenance of crank pin shell.

-inspect if there is not fretting on the crank pin shell, also for seizure mark, Cavitation or any embedded foreign matters. repair using oil stone.
- measure shell thickness using spherical micrometer.
- calculate clearance from measurement of inner diameter of large housing thickness of Shell and diameter of crankpin.
-oxidation leads to black is colour .Dye penetrant test and colour check for cracking and scoring.

11.Inspection and maintenance of liners.

-Remove scale or silicone rubber accumulated on the liner outer Periphery using a wire brush.
- Colour check and crack check. Inspect liner outer Periphery for Cavitation or corrosion or freeting. Reason for corrosion or Cavitation 1)cooling water rust preventive agent is not working properly 2)cooling water pressure is low 3) cooling water is mixed with air.
-measure the inner dia of liner in port-stbd and fwd-aft by internal micrometer. Compare with previous reading to get wear down of liner.

Measurement of Cylinder Diameter
While the piston is removed from the cylinder, the latter is measured to record the wear. The measurements are taken by means of an inside micrometer,
with measuring points at TDC-position for the upper-most piston ring, halfway down, and at the BDC in the cylinder liner.
The measurements normally should be taken in both transverse and in longitudinal direction.When measuring, take care that the measuring tool has approximately the same temperature as the liner.
When the wear of a cylinder liner exceeds the value indicated on , when it becomes too troublesome to maintain adequate service conditions, the cylinder liner in question should be replaced.

So overall measurement in auxiliary engine are as follows:
1.piston pin outer dia and piston bush inner dia.
2. The axial clearance of piston ring-0.40mm max.
3. Liner wear rate by measuring inner dia of liner
4. ovalness of bearing cap without bearing shell .
5. Diameter of crankpin .
6. Piston outside dia and liner inside dia.