Auxiliary Engine

Auxiliary Engine are used on board ship to generate electricity for all the auxiliary equipment in the engine room, navigational equipment, cranes, domestic use like lighting, galley hot plate, etc.

                                         

Starting a generator:-

• Direct starting type
• Air motor starting type

                                                  Pic credit:- Daihatsu Manual

Ways to start a generator:-

1. Local starting- Starting generator from the local station.
2. Remote Starting- Remote starting from the control room.
3. Auto starting- When one generator fails/trips other generator on auto standby automatically starts and takes the load.                                  

Checks before starting the generator:-

1. Check the starting air line.
2. Check the lub oil level from the dip stick.
3. Check the cooling water valves, F.O. valves and pressure.
4. Check F.O. line i.e. H.F.O. inlet to H.F.O. outlet and if D.O. starting then D.O. inlet to D.O. outlet.  
5. Check for any leakage present.
6. Check for turning gear/ turning bar safety switch in the required position i.e. no interlock is active.
7. Check the governor oil level.
8. If indicator valve is present always blow through the engine before starting.

Checks after starting:-

1. Engine RPM.
2. Abnormal sound.
3. Pressure readings.
4. Exhaust temperature readings.
5. Lub oil level.
6. Gas leakage.
7. Leakage and loosening of each part.

After starting the generator, first run the engine on no load condition such that the jacket cooling water and lubricating oil temperature has increased. Then generator should be taken on load. After taking on load gradually increase the load.

Switching between the fuels during running:

Some generators requires D.O. as a fuel for starting and warming up, then after attaining the required temperature they are switched back to H.F.O. for running. And in such generators before stopping/shutting down H.F.O. is changed back to D.O.. Care must be taken during switching/changeover operation.

                                                    

                                                          Change over switch

How to take on load?

1. Auto mode :- When in auto mode generator automatically comes on load starts sharing the load.
2. Manual mode :- When in manual mode first we follow these steps

• Check the generator control is in remote control.
• After that check the voltage of the incoming generator.
• Then switch on the synchroscope.
• Check the movement of the needle/light/pointer moving in clockwise or anticlockwise direction.
• Clockwise direction means running faster i.e. frequency is higher and anticlockwise means running slow i.e. frequency is lower.
• Now Frequency and phase must match so that generators can run in parallel.
• Frequency controller or governor controller is used to control the frequency and thus the  when the pointer in the synchroscope moves slowly in clockwise direction and crosses 11 o' clock then breaker is pressed.
• When pointer is moving slowly clockwise direction and reaches 12 o' clock indicates that the incoming generator and the bus voltages are in phase i.e. synchronism.
• Thus generator is on load i.e. running parallel.
• Now they share the load and if load sharing is in "Auto" then generators will share the load equally, if in "Manual" then the load on the generators is set accordingly.
• Always check the parameters during the full operation.

How to remove from the load :-

• First put the load sharing in manual mode.
• Transfer the load on the other generator.
• When the KW on the generator which has to removed from load reaches to almost zero but not zero so that reverse power trip is not activated, then generator is offloaded by opening ACB.

How to Stop the generator :-

• After taking generator off load, generator can be stopped from the ECR by pressing the stop button.

• It must be noted that if before stopping change over is required the fuel must be changed over from H.F.O. to D.O. before off loading. After the complete change over has been done then only the generator must be stopped.

Preparation before any maintenance work :-

• Take generator in local control.
• Put "Men At Work" sign in the ECR.
• From local panel put lever in stop position.
• Close starting air valve.
• Close fuel oil, cooling water inlet and outlet valves.
• Open the cooling water drain valve to drain the jacket water.
• Open the indicator cock if present.

Removal of Cylinder Head

1. Remove all the covers.
2. Put the piston in TDC/ Top position.
3. Remove all the piping around the cylinder head.
4. Remove the F.O. high pressure joint and inlet connector, and extract the fuel injection valve.
5. Remove the exhaust manifold mounting bolt.
6. Take out the rocker arm device by loosening the mounting nut.
7. Extract the valve retainer tee and push rod.
8. Using the hydraulic jack(Applied pressure must be according to the "Manufacturer Instruction Manual"), remove the cylinder head mounting nut.
9. On the upper surface of the head mount the cylinder head suspending implement. Suspend the head using chain block and wire rope.
10. Cover the cylinder liner and intake duct and remove the cylinder head gasket.
11. When lowering down the cylinder head care must be taken so that no scratch comes on the lower surface of the cylinder head.

                                                 Cylinder Head

Inspection and maintenance of cylinder head

     1. Body:-

• First remove the parts like inlet and outlet valves, also starting valve, indicator and safety valve if present, 
• Inspect the condition of the carbon deposit on the combustion surface, inlet and exhaust port. 
• After the inspection, clean the surface and check for corrosion. Also performance color test on surface for cracks.
• Perform the water leak test at specified pressure.

     2. Intake and exhaust valve guides:-

• Inspect the valve guide for corrosion and measure the inner diameter and record the data.
• In case of replacement of the guide:-
• First remove the valve guide with the help of round bar, and strike out the guide with a hammer.
• Fit the new valve guide by means of cold fitting.

      3. Inlet and exhaust valve seat:-

              Inlet valve seat

• Inspect the valve guide for corrosion and measure the inner diameter and record the data.
• In case of replacement of the guide:-
• First remove the valve by performing the padded welding on the inner surface of the valve seat and quench it with water. Now the seat will contract and will be removed easily.
• Fit the new valve seat by means of cold fitting. 

                 Exhaust valve seat

• Inspect the valve guide for corrosion and measure the inner diameter and record the data.
• In case of replacement of the guide:-
• First remove the valve by performing the padded welding on the inner surface of the valve seat and quench it with water. Now the seat will contract and will be removed easily.
• Fit the new valve seat with new O- Ring by the means of cold fitting.

     4. Inlet and exhaust valve

• For assembly and disassembly special tool is provided by the manufacture.
• After taking out the valves inspect the following:-
• corrosion of valve head area.
• corrosion or bending of valve stem area.
• pitching or blow out of valve seat area.
• contact condition of valve seat and valve stem area.
• crack or corrosion of valve spring, cracks can be found by performing color test.
• Measurement of valve stem
• Measure stem area of inlet and exhaust valve.
• Clearance between the stem area and valve guide.
• Measurement of valve seat and valve head thickness.
• Facing up/ lapping of inlet and exhaust valves.

     5. Valve rotator

• Disconnect the  circlip and  disassemble the parts.
• After washing the parts carefully inspect them and replace if necessary.
• Assemble in the reverse order.

                                        Pic credit:- Daihatsu Manual

    6. Starting valve - if present

• Disassembly
• Remove the starting valve cover and extract the starting valve assembly from cylinder head.
• Extract the spilt pin, nut and starting valve.
• Remove the starting valve piston and spring.
• Inspection and maintenance
• Clean the individual parts.
• Check the sticking of the starting valve and starting valve piston and the leak of gas from the seat area.
• Corrosion or scratch of the spring.
• Assembly
• Reverse order of disassembly.

     7. Rocker arm

• Disassembly
• Loosen the nut and disconnect the rocker arm device assembly.
• Remove the valve retainer tee.
• Remove the snap rings at both the ends of the rocker arm shaft and disconnect the rocker arm and of intake and exhaust valves.
• Inspection and maintenance
• Clean the individual parts.
• Measure the clearance and beyond limit then replace.
• Check the contact conditions of the valve retainer tee and valve retainer guide.
• Check for bend and scratch on the surface.
• Assembly
• Reverse order as of disassembly.

Mounting of Cylinder head

• It should be done in the reverse order of disassembly

NOTE -  Always refer the manual before performing the job and tight according to the specified torque in the "Manufacture Instruction Manual".

For the inspection and maintenance of the Piston, Piston rings, Liner, Connecting rod, Main bearing, Crankshaft, Camshaft, Timing gear, Valve operating device, Governor, Air cooler, Lubricating oil cooler, Fresh water cooler, Turbocharger, Fuel pump, Cooling water pump and Lubricating pump always refer the "Manufacture Instruction Manual".

                                            Pic credit:- MAN Manual

Thrust Bearing

It is mounted on the front and rear surface of the main bearing(flywheel side)

Crankcase And Camcase inspection and Crankshaft deflection

Preparation

• Stop the generator and put the control in local.
• Put Men At work tag.
• Air starting valve closed.
• Indicator cock open. If present.
• Turning gear engaged. 
• When the generator is stopped, After some time stop the pre lub pump and let it cool down before the inspection.  
• Wear proper PPE and use safety lamps and torches.
• Always prepare the necessary permit and SJA before starting the job and conduct a tool box talk with personal involved in the job.

Inspection

• First open all the crankcase door and check the gasket for wear.
• Visual inspection of the crankcase walls, crankshaft and lub oil.
• For lub oil its color in important if it is black means blow past in unit.
• Check the smell of the lub oil.
• Test the lub oil in lub oil testing kit.
• Touch the lub oil feel the sludge content, also check the flow of the oil.
• Check the inside of the liner with the help of torch for scoring marks and cracks.
• Inspect the Connecting rod floating.
• Take the main bearing and con rod bearing clearance.
• Check for hot spot on the surface.
• Condition of the crankpin.
• Condition of the main bearing bolt and con rod bolts.
• Check the balancing weight arrangement.
• Check the crankcase relief doors.
• Check for the slip of web.
• check for any signs of wiped bearing.
• Always check for jacket cooling water leakage.

Deflection of crankshaft

• It varies according to the temperature so it should be taken when the engine is in cold condition. 
• Before measurement check the deflection gauge by pushing the contact piece with hand then contact piece and the dial should return to original position correctly.
• For measuring and calculating the deflection always refer the "Manufacturer Instruction Manual".

Camcase inspection

Check Roller Path of Cams

While turning the engine, examine the cam discs and in particular, check the rollers of cam and guide for cracks, crackles and ruffle.

Cleaning Filters

Fuel oil and lub oil filters remove foreign matters or sludge in oil and keeping the oil clean, and maintaining the normal operation of the various parts of the engine. For maintaining the capability of filters it must be periodically overhaul and cleaned.

Notch type duplex filters, Auto-backwash filter, Cartridge filters and centrifugal bypass filters are fitted.

Performance of the engine

It is taken at about 90% of the engine load and compared with the shop trial data. For measuring the performance maximum combustion pressure is taken i.e. Pmax. We get the Pmax with the help of indicator which is installed on the indicator valve and thus the Pmax is calculated. Now all the data like load(%), engine room temperature, HT and LT temperature and pressure, L.O. temperature and pressure, fuel oil temperature and pressure, charge air pressure and temperature, exhaust gas temperature of individual unit and T/C, governor index, power, voltage, current and power factor are recorded in the performance check sheet provided.

Auto stop/ Trip

• Lub oil low pressure at engine inlet.
• HT jacket cooling water high temperature.
• Overspeed trip.
• Failure of engine speed sensor.

Lambda controller and jet assist

• Lambda controller is used to control the excess fuel injection in the combustion chamber of a marine engine when there is a change in the engine load i.e. during a momentary increase in the engine load.

• A jet assist system installed on the compressor casing can effectively reduce turbocharger lag. This jet assist system is useful to improve the acceleration performance of the turbocharger. Therefore, the application of a jet assist system in turbocharged engines prevents engine stalls and reduces smoke.
  
  

Cooling water and Lub oil system

Both can be understood by looking into the flow line diagram.

                                                              Pic credit:- Daihatsu Manual

Seal Pot

Provided in the middle of the fuel oil pressure gauge piping in case using "Heavy Fuel Oil" and filled with ethylene glycol to replace the pressure, so that the pressure gauge can be prevented from malfunction due to sticking of fuel oil in cold condition.

Pedestal Flange sleeve

Sleeve bearings are flange-mounted on the end-shield. With its excellent quality and performance it can withstand high level of vibration.

• highly suitable for static, radial and axial dynamic load.
• high speed application.
• Since split type easy to maintain. 

Combustion condition

                                         Pic credit:- MAN Manual

Reference:- Daihatsu Manual, MAN Manual and Author's experience

Scavenge Space and Under Piston Space Inspection

Inspection provides useful information about the condition of cylinders, pistons and rings, at low expense. It consists of visually examining the piston, the rings and the lower part of the cylinder liner, directly through the scavenge air ports. To reduce the risk of scavenge box fire, remove any oil sludge and carbon deposits in the scavenge air box and receiver in connection with the inspection.

The port inspection should be carried out at the first stop after a long voyage, e.g. by anchoring if possible, to obtain the most reliable result with regard to the effectiveness and sufficiency of the cylinder lubrication and the combustion cycle (complete or incomplete).

A misleading result may be obtained if the port inspection is carried out after arrival at harbour, since manoeuvring to the quay and low-load running, e.g river or canal passage, requires increased cylinder oil dosage, i.e the cylinders are excessively lubricated.

During low load, the combustion cycle might not be as effective and complete as expected, due to the actual fuel oil qualities and service (running) condition of the fuel injection equipment.

Preparations:-

1. Make sure that vessel as necessary permission from port authorities or bridge for main engine immobilization. Take control of the main engine to ECR. Put aux blowers on manual.
2. Block the starting air supply to the main starting valve.
3. Open the indicator valves. Engage the turning gear.
4. Make sure engine is sufficiently cool before opening up the scavenge space door and under piston door.
5. Complete all the paper work i.e. enclosed space permit, cold work permit, tool box talk and safe job analysis.
6. Remove the inspection covers on the camshaft side of the cylinder frame, and clean the openings. Remove the cover(s) on the scavenge air receiver.
7. After opening the door properly ventilate the space with portable blowers.
8. Ensure pockets are empty and take in a flashlight, mirror, bucket of rags, turning gear operating control and a digital camera.
9. Wear proper PPE.

                                       Scavenge air receiver

Procedure:-

1. Scavenge port inspections are best carried out by two men, the most experienced of whom inspect the surfaces, and state his observations to an assistant, who records them. The assistant also operates the turning gear.
2. Keep the cooling water and cooling oil circulating, so that possible leakages can be detected.
3. Begin the inspection at the cylinder whose piston is nearest BDC.
4. Inspect the piston, rings, and cylinder wall.
5. Wipe the running surfaces clean with a rag to ensure correct assessment of the piston ring condition.
6. Use a powerful lamp to obtain a true impression of the details.
7. Record the results.
8. Measure the total clearance between the piston rings and the ring grooves.
9. Continue the inspection at the next cylinder whose piston is nearest BDC, and so on according to the firing order.
10. Check the non-return valves (flap valves/butterfly valves) in the auxiliary blower system for easy movement and possible damage.
11. Remove any oil sludge and carbon deposits in the scavenge air boxes and receiver.

Observation:-

1. Piston crown condition.
2. Deposits on the top land and ring land.
3. Ring breakage.
4. Ring movement.
5. Surface and lubrication condition of cylinder liner, piston rod, piston ring and piston skirt.
6. Deposits in the scavenge box and scavenge receiver.
7. Check for abrasion on the liner surface form remnants of mechanical wear, corrosion and combustion.
8. Condition of the flaps and non-return valves.
9. Check the scavenge relief valves and temperature probes. Check the security of grids and plates. Sight auxiliary blower fan impellors.

                                                      Pic Credits:- MAN B&W Manual

                                               Pic credits:- marineengineersknowledge.com

                         

                                         Piston Crown

                                         Cylinder Liner

                                        CPR Piston Rings

                                        Under Piston Space

                                                  Flaps

About the observation:-

• Piston Rings: In good Condition

  The rings will move freely in the grooves and also be well oiled, intact, and not unduly worn. The ring edges will be sharp when the original rounding’s have been worn away, but should be without burns.

• Piston Rings: Micro-seizure

  Dry areas are formed on the cylinder wall, these areas and the piston ring surfaces will, by frictional interaction, become finely scuffed and hardened, i.e. the good “mirror surface” will have deteriorated.

  A seized surface, which has a characteristic vertically-striped appearance, will be relatively hard, and may cause excessive cylinder wear.

                                     Pic credits:- marineengineersknowledge.com

• Piston Rings: Scratched

  Scratching is caused by hard abrasive particles originating from the ring itself, or, usually, from the fuel oil.

• Piston Rings: Sticking

  The free movement of the rings in the grooves is essential, and can be checked either by pressing them with a wooden stick (through the scavenge ports) or by turning the engine alternately ahead and astern, to check the free vertical movement.

                                              Pic credits:- marineengineersknowledge.com

• Piston Rings: Breakage/Collapse

  Broken piston rings manifest themselves during the scavenge port inspection by:

  · Lack of “elastic tension”, when the rings are pressed into the groove by means of    a stick.

  · Blackish appearance.

  · Fractured rings.

  · Missing rings.   

           Piston ring breakage is mostly caused by a phenomenon known as “collapse”.                   Collapse occurs if the gas pressure behind the ring is built up too slowly, and                     thereby exerts an inadequate outward pressure. In such a case, the combustion                   gas can penetrate between the liner and ring, and violently force the ring inwards,             in the groove.

           Slow pressure build-up behind the rings can be due to:

            · carbon deposits in the ring groove,

            · too small vertical ring clearance,

            · partial sticking,

            · poor sealing between the ring and the groove floor,

            · “clover-leafing” (see below)

            · ring-end chamfers (see below)

             · too large ring-edge radii, etc.

             “Clover-leafing”, is a term used to describe longitudinal corrosive wear at several

              separate points around the liner circumference.

                                       Pic credits:- marineengineersknowledge.com

              Chamfering at the ring ends is unnecessary and detrimental, as the scavenge                    ports are dimensioned to avoid “catching” the ring ends.

• Piston Rings: Blow-by

  Leakage of combustion gas past the piston rings (blow-by) is a natural consequence of sticking, collapse or breakage. Blow-by is indicated by black, dry areas on the rings and also by larger black dry zones on the upper part of the liner wall.

• Deposits on Pistons

  Usually some deposits will have accumulated on the side of the piston crown (top land). Carbon deposits on the ring lands indicate lack of gas sealing at the respective rings.

• Lubricating Condition

  All piston rings should show oil at the edges. White or brownish coloured areas may sometimes be seen on the liner surface. This indicates corrosive wear, usually from sulphuric acid, and should not be confused with grey-black areas, which indicates blow-by.

Before closing the scavenge door make sure:-

• No personal is left behind.
• Responsible person must check for the tools, rags etc. are not left behind.
• Account for all the nuts and bolts.
• Use correct tightening sequence and proper gasket to seal the door.

Reference:-  

MAN B&W Manual; marineengineeringonline.com; marineengineersknowledge.com

and Authors Experience

Main Engine Performance

In order to monitor the engine performance, we would need to measure the power output and fuel consumption of the engine. For knowing the performance we have  to  study  the  indicator  cards  along  with  their  draw cards, measure  and  estimate  the  power developed  in  each  unit. Where the  performance  of  scavenge  and  exhausting  are  doubtful,  their  light  spring diagrams  must  also  be  taken  for  investigation. In  those  units  where  compression  is  doubtful  their compression cards  must  also  be  taken. Data obtained from the performance is then compared with the ship sea trials/machinery trials, shop trials/ test bed trials and the obtained performance curves which enable the engineers to run the ship safely and economically.

                                                  Pic Credits :- Dieselship.com

Before taking the performance one must make sure the following conditions are meet :-

1.   Performance must be taken in calm sea never in rough weather.

2.   Ship propeller must be fully immersed.

3.   Ship is fully laden.

4.   Engines load must be kept steady till the performance is taken.

5.   Engine running at 85-90% of the MCR.

Readings to be recorded while taking the performance:-

1. Fuel oil and lubricating oil(Cylinder oil) flow meter reading, Rpm, revolution and running hour counter  must be recorded, first at the starting and other exactly one hour after the first reading in same order first  reading were taken.
2. Load percentage/ index and governor index.
3. Fuel pump index, VIT index, exhaust gas temperature, cooling water outlet temperature, piston outlet lubricating oil temperature of individual cylinder must be recorded.
4. Air cooler cooling water inlet and outlet temperature as well as the air inlet and outlet.
5. Exhaust gas temperature before T/C and after T/C.
6. T/C  differential filter pressure.
7. Scavenge air pressure before and after air cooler i.e. differential pressure.
8. T/C rpm.
9. Axial vibration.
10. Scavenge air temperature.
11. Lubricating oil temperature of main engine inlet and outlet as well the T/C inlet and outlet along with the pressure.
12. Fuel oil pressure and temperature.
13. Engine room temperature.
14. Forward and aft draft of ship.
15. Speed of the ship and direction.
16. Wind speed and direction.
17. Wave height.
18. Fuel oil viscosity.
19. Test date and test hour.
20. Thrust bearing temperature.
21. Sea water temperature.
22. Position of the ship is also recorded.

                                                       Pic Credits- MAN B&W Manual

Precautions to be taken while taking performance:-

1. Take proper PPE protection like gloves, safety shoes etc.
2. Indicator cock should be blow through so that it is free of soot and oil.
3. Indicator card piston should be removed; cylinder and piston should be cleaned and well lubricated. Also the indicator piston tightness in the cylinder must be checked. It can be done by dismantling the piston and allowing it to drop slowly through the cylinder. Bottom of the cylinder is closed and the piston should be held in the position.
4. Drum should not hit the stop at the end position. Play in the pencil mechanism will distort the diagram.
5. The stylus should be adjusted to a light writing pressure.
6. The drum when actuated the motion of the power piston by a cam should be correctly positioned. It represents the travel of the power piston. In that case the compression and expansion diagrams with the fuel cut off should coincide. 

Procedure to obtain indicator card:-

1. Stretch diagram paper firmly over the drum.
2. Before connecting the instrument to the Indicator cock, open indicator cock, allow two or three firing strokes, to blow out soot and combustion residues in the cock.
3. Fasten the instrument to the cock so that the cord is taut.
4. Take the atmospheric line with the cock shut.
5. Open the indicator cock and lightly press the stylus against the paper and make vertical lines as the piston moves up and down, when you are ready to pull the roller string, make sure it is in the bottom and pull the string till the cycle is described.
6. Close the cock.
7. Disconnect the cord.
8. Make sure that the instrument is not exposed to high temperature for long time. This may affect its accuracy. Remove the hook, turn the drum by hand to a place clear form for the power diagram, take compression pressure line with the fuel cut off.

After taking indicator cards from all the cylinders, open the instrument and clean all the parts, and lubricate the same.

Types of Indicator Cards

Power or In phase card

Draw or out of phase card

Light Spring card

Compression card

                                                           Pic Credit - Dieselship.com    

Power calculation

The area can be measured by an instrument known as ‘Planimeter’ or by the use of the mid ordinates rule. The area is then divided by the length of the diagram in order to obtain mean height. This mean height, when multiplied by the spring scale of the indicator mechanism, gives the indicated mean effective pressure for the cylinder. The mean effective or average pressure [Pm] can now be used to determine the work done in the cylinder.

Indicated Power of Unit [ip] =Mean Indicated Pressure [Pm] x Area of Piston [A] x Length of Stroke [L] x Number of Power Strokes per Second [N]

Indicated Power of Unit = Pm L A N

Reference :- Dieselship.com;  Authors experience