Introduction: Engine Room Machineries

• The instruments on board ship are marked in metric system of units-

Temperature sensors used onboard-

Characteristics of diesel engine-

• All diesel engines fall under the category of internal combustion engines [ICE].

• Combustion engines are manly of 2 types- spark ignition engines [petrol engines] and compression ignition engines [diesel engines].

• All diesel engines onboard are compression ignition types.

• There is further classification of CI engines 2 stroke and four stroke.

• Two stroke engines are cross-head type and four stroke engines are trunk type on basis of their construction.

Operating principal of compression ignition engine

• An engine uses both reciprocating motion and rotary motion to transmit energy.

• Four main parts of engine are as follows- a cylinder, a piston, a connecting rod and a crankshaft.

Essential systems for the function of the engine

Lubricating oil system- this system is sued for lubrication of moving parts.

Cooling water system- this system is used for dissipating heat from the engine parts as there is continuous heat generation.

Fuel oil system- this system is used for giving fuel to the engine.

Starting air system- this system is used for starting main or aux. engine by means of injecting 30 bar air into the engine.

Speed regulation and safety system- this system is for operation of safety devices for the engine.

Characteristics of auxiliary engine-

1.eSmaller in size.

2.Medium speed engines. [250-800 RPM]

3.Usually used for electrical power generation.

4.Most of the diesel ships have 3 or 4 diesel engines.

5.Before departure and arrival port 2 diesel engines are run to bear additional load coming from mooring machinery, simultaneous operations of two compressors, operations of bow thrusters tc.

Characteristics of main engine-

a) reversible engines.

b) Slow speed engines [up to 300 RPM]

c) Large in size and used to propel the ship

Parts of main and auxiliary engines are given below-

Top dead centre-
when the piston is at the highest point in the cylinder, the position is called the top dead centre or TDC.

Bottom dead centre-
when the piston is at the lowest point in the cylinder, the position is bottom dead centre or BDC.

Stroke-
each movement of the piston from top to bottom or from bottom to top is called a stroke.

Two stroke cycle- 

Intake and compression-
air enters the cylinder as the piston from TDC to BDC and air is compresses when the piston moves from BDC to TDC and the temperature of air rises.

Ignition and power stroke-
just before the TDC fuel is injected at high pressures and it ignites. Pressure and temperature increase further & pushes the piston.

Scavenge and exhaust-
fresh air starts entering and the burst of gases are removed from the cylinder.

Four stroke cycle-

Intake stroke-
inlet valve is open in this stroke and gush of fresh air enters the combustion chamber and piston is travelling from TDC to BDC.

Compression stroke-
inlet and exhaust valves are closed and the piston is travelling from BDC to TDC.

Power stroke-
he power stroke begins when the fuel and air are In the correct ratio and the surrounding air becomes heated up due to compression stoke, due the which burning of fuel takes place and piston is pushed downwards towards BDC.

• Exhaust stroke- in this stroke the exhaust gases are expelled out during this cycle the exhaust valve is open and the inlet valve is closed.

Turbo-altternaor-
waste heat of main engine exhaust gasesit is a generator operating on steam produced from . It is also possible to operate an exhaust turbine driven generator in arrangement similar to steam turbine.

Shaft generator-
some ships may have shaft generator driven by main engine by means of gears and coupling, main propulsion shaft is arranged to drive a generator that is coupled to the main bus bar.

Crankcase lubricating oil in an engine functions-

• LO is used for lubrication of all bearings, cross head guides, chains, cams and gears within the crankcase.

• Reducing friction between moving parts in contact.

• Cooling and cleaning of parts.

• Protecting components against corrosion.

Cylinder lubrication in main engine-

• Cylinder LO reduces friction between piston rings and the liner.

• It neutralizes acidic conditions created by products of combustion.

• Act as insulating film between cylinder wall and hot gases.

Cam shaft lubrication-

• The function of camshaft is to operate fuel pumps for each unit and operate exhaust valves.

• On some engines to prevent contamination of LO from leaking FO from fuel pumps, independent systems are used for lubrication

Turbo-charger bearing lubrication-
Turbo-charger bearing gets supply from the main LO system or it may have dedicated sump on each side [blower and turbine side].

Fuel system-

• Fuel is supplied to main engine needs to be clean and at appropriate quantity, viscosity & pressure.

• The fuel is passed through purifiers, duplex filters to ensure its cleanliness and through gear pumps and fuel injectors to ensure its optimum pressure and atomization.

Cooling water system-

• Functions of CW system- to cool charge air before it enters the combustion chamber, cooling of liners and piston, maintains temperature of LO.

• In modern ships central cooling system is used in which fresh water is used as cooling medium.

Air starting and reversing system-

on direct drive ships having fixed pitch propellor , starting system has an arrangement to start the engine in reverse rotation for astern movement of the ship.

Air charging system-

•The function of air charging system is to supply air to the cylinders.

•The efficiency of the system has to be such that all exhaust gases are removed and the cylinder gets charged at pressure higher than the atmosphere.

Safety features of diesel engines-

• Relief valve on each cylinder.

• Crankcase relief doors.

• Over-speed trip.

• Oil mist detector.

• High exhaust temperature alarm.

• High CW temp. alarm.

• Bearing high temperature alarm.

• High piston cooling oil temperature.

• High scavenge air temperature alarm.

• Low pressure for LO supply.

• Low pressure for CW supply.

• Low level at tanks for water and oil.

Compressed air-

It is used on board ships for various purposes which are given below-

• Starting diesel engines @20-30 bar.

• Used as control air for remote operating systems.

• Used as general service air for maintenance in engine room.

• Charging of breathing apparatus bottles [around 220 bars].

• Operation of air operated hand tools and machines.

Air compressor-

• ·Air in normal state cannot do any of the above-mentioned tasks, unless it is compressed, but on compression temperature and pressure increases while the volume decreases.

• ·Air compressor run by an electric motor to do the work of adding energy to the air.

• ·Ships are fitted with at least 2 air compressors and compressed air is stored in air bottles.

Starting of air compressor manually-

1. Change the switch to manual position on the switch board.

2. Check the L.O sump level and condition.

3. Open the moisture drain valve.

4. Open the compressor discharge valve & charging valve of air bottle.

5. Open cooling water system valves.

6. Turn the compressor flywheel by hand (one turn).

7. Start the motor, after draining the moisture shut the drain valve.

8. Check the motor ampere consumed.

9. Check the pressure gauge readings.

10. Frequently drain the moisture.

11. When charging full, open drain valve and stop the compressor

Steering gear-

 just like we need steering wheel in cars and trucks to give direction, same work is done by steering gear on a ship, it directs ship towards port and starboard side depending upon the order given to it via steering wheel.

Steering gear components-

Steering gear watchkeeping routine-

• ·Oil level in tanks of steering gear system.

• ·Leakage from pumps, pipe joints etc.

• ·Abnormal noise and vibration.

• Load of the pump on electric motor in Amps.

• Condition of links for controlling pumps, control mechanism etc. 

Bow thrusters-

• These are the type of propellor which are smaller in size and which helps in better manoeuvrability of ships.

• These are used for vessel manoeuvring operations of vessels in port waters.

• Generally, bow thrusters are transverse thrusters placed at the forwards of the ship.

• Advantages – better manoeuvrability, safety of ship increases, saves money by less usage of tugs.

Lagging-

• Lagging is an insulating material wrapped around pipes , boilers or tanks to prevent loss of heat.

• Insulating material are generally poor conductor of heat thus, preventing any heat transfer to the external environment.

• It is used around pipes , boiler, hot filter around tanks and in refrigerated compartment etc.

• •It usually comes in the form of a fibrous material that can be stuffed in a water/heat resistant cloth which could be wrapped around pipes and kept in place by clips, wires or metal casing.

• While working with insulating materials such as glass wool, you must protect the body use gloves & goggles. While handling any powdery material use face mask.

• While dismantling pipes or equipment that is insulated , take care in removing the lagging and putting it back after completing the work.