Month: November 2018

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Operations of IC Engine as Main Propulsion Engine:

  1. Warming Up (Preparation for Standby)
  2. Manoeuvring
    1. Starting
    2. Reversing

(i) When running at manoeuvring speed

(ii) When running at Full Away (full speed/full power)

  1. Full Away (Full Speed / Full Power)

Limitations and Care during Full Away & Manoeuvring

 

Warming Up (Preparation of ME for Standby)

Main Engine will be stopped on Arrival at a Port

Main Engine has to be started when Departure from the Port

Before Starting the Main Engine, after a stay in port, Main Engine should be Warmed Up Warming Up time depends upon the size of the Engine

In modern Engines, Warming Up of ME is done ½ hour before the ETD (Estimated Time of Departure)

 

Various supply tanks, filters, valves and drains should be checked

JCW System should be started

JCW temperature should be raised / increased gradually

[This will enable the various engine parts to expand in relation to one another]

JCW temperature should be raised / increased near to its operating temperature

Lubricating Oil System, Fuel Oil System & Steam Tracing System should be started and their temperatures should be increased gradually near to their operating temperatures

All controls and alarms should be checked for correct operation

Indicator cocks are opened, turning gear engaged and the engine turned through several complete revolutions

[This will enable the water, which may have collected in the cylinder, to be forced out]

(Cylinder Lubrication should be supplied by manual operation of the lubricators)

Turning gear is disengaged

Auxiliary Scavenge Blowers, if manually operated, should be started

Engine is blown through air (Engine is turned by air)

Indicator cocks are closed

 

Manoeuvring – Starting

  1. The direction handle is positioned ahead or astern. This handle may be built into the telegraph reply lever. The camshaft is thus positioned relative to the crankshaft to operate the various cams for fuel injection, valve operation, etc
  2. The manoeuvring handle is moved to ‘start’. This will admit compressed air into the cylinders in the correct sequence to turn the engine in the desired direction
    3. When the engine reaches its firing speed the manoeuvring handle is moved to the running position. Fuel is admitted and the combustion process will accelerate the engine and starting air admission will cease

 

Manoeuvring – Reversing (When running at manoeuvring speeds):

  1. Auxiliary Scavenge Blowers, if manually operated, should be started
    2. Fuel supply is shut off. This will Stop the Engine
    3. Direction handle is positioned astern. This will reset the camshaft for astern running
    4. Compressed air is admitted to the engine to turn it in the astern direction
    5. Fuel is admitted. Engine will accelerate (i.e. combustion process takes place)
  2. Air admission is stoppedManoeuvring – Reversing (When running at full speed/full power):
    1. Auxiliary Scavenge Blowers, if manually operated, should be started
  3. Fuel is shut off. This will slow down the engine
  4. Direction Handle is positioned astern. This will reset the camshaft for astern running
    3. Blasts of compressed air may be used to slow the engine down from its ahead running direction
    4. When the engine is stopped, Compressed air is admitted to the engine to turn it in the astern direction
  5. Fuel is admitted. Engine will accelerate (i.e. combustion process takes place)
  6. Air admission is stopped

 

Full Away (Full Power / Full Speed)

Limitations and Care during Full Away & Manoeuvring

 

  1. Normal Service Power at Full Away (Full Speed / Full Power)
  2.  Vibration during Manoeuvring and Full Away
  3. Operation on Heavy Fuel Oil during Manoeuvring
  4. Maximum period in Standstill/Stopped position during manoeuvring

Normal Service Power at Full Away (Full Speed / Full Power)

At Full Away (Full Speed / Full Power) Main Engine must be run at Normal Service Speed / Power

At Full Away ME can be run at less than Normal Service Speed / Power – if directed by the Company or under emergency conditions involving safety of life or safety of the ship
If ME normal service speed / power is required to be altered then the fact and the reason for the alteration should be reported to the Company and noted in the Engine Log Book

 

Vibration during Manoeuvring and Full Away

ME may experience excessive vibration at particular speeds (critical speed / rpm) (barred Speeds)

Vibration can cause severe damage to machinery, bearings, pipes, fittings, instrumentation and structure

ME must not be run at critical speed / rpm (barred Speeds)

ME may also experience excessive vibration at certain other speeds due to combination of draught, trim and weather. These speeds should also to be avoided

ME may also experience Vibration due unbalanced cylinder loads and also due to improper tightness of holding down bolts

Vibration may be detected and measured using condition monitoring equipment

Any significant increase in vibration levels, that cannot be arrested,  must be reported to the management ashore

Operation on Heavy Fuel Oil during Manoeuvring

Modern Main engines can be manoeuvred on heavy fuel

If engine encounters some problem, due to fuel oil, then engine must be changed over to diesel oil (irrespective of whether the engine is operated using bridge control, or ECR control or engine room control

 

Maximum period in Standstill/Stopped position during manoeuvring

This period varies from engine to engine

If this period has exceeded, then correct procedures should be followed for re-starting the engine

 

Selection Criterion of IC Engines

Reasons why 2 stroke engines are preferred than 4 stroke engines as main propulsion engine on ships

 

Fuel: Two stroke engine can burn low grade fuel oil and hence reduce running cost

Efficiency: Thermal Efficiency and Mechanical Efficiency of 2 stroke engine is more

Power to weight ratio: 2 stroke engines are large stroke engines that produce more power. Hence 2 stroke engine has high power to weight ratio

More Cargo: Due to high power to weight ratio of 2 stoke engine, Ship can carry more weight (more cargo)

Less Maintenance: Maintenance requirement of two stroke engine is less (less moving parts)

Direction control: Direct starting and reversing is easier with two stroke engine

No speed reduction attachments: Two stroke engine is low speed engine. Hence there is no requirement of reduction gear (speed reduction) arrangement / attachment as required for high speed four stroke engine

 

Power to Weight Ratio of IC Engine = Power generated by the Engine   kW/kg

Mass of the Engine

Example:

Engine’s Power = 250 kW

Engine’s Mass = 380 kg

Power-to-Weight Ratio = 0.65 kW/kg

 

Power to Weight Ratio is used for comparing the Performance of one Engine with the performance another engine

 

 

Specific Fuel Oil consumption (SFOC) of IC Engine = Mass of fuel consumed per hour  g/kWh

                                                                                                              Power developed

 

Consumption of Fuel Oil per Unit Energy at the Output Shaft of the Engine for given time

(Or)

Mass of Fuel Oil Consumed per average Shaft Power developed by the Engine for a given time

 

SFOC = Co D 106

h Pe

106 is multiplied to convert the fuel oil unit in tonnes to gram

Co = Fuel Oil Consumed Over the period in m3

D = Temp. Corrected Density in kg / m3

h = Measuring period in hours

Pe = Brake Horse Power in kW

Take flow meter reading for specific time interval [usually 1 hr period, h = 1 hr)

i.e. Diff between initial readings and final reading (after 1 hr) = Co in m3

Density is given in Bunker Delivery Note in kg /m3

Calculate Temp Corrected Density (Take Temp of fuel at the flow meter)

Temp Corrected Density D = (Density of Fuel Oil @ 150C) * [1-{(T-15) * 0.00064}] kg/m3

Calculate Shaft Power at the given interval/period = Pe in kW

 

SFOC is used to determine the Efficiency of the Engine

 

 

Definitions (Formulae) and Calculations (Numericals/Problems)

Indicated Power

Brake Power

Shaft Power

Delivered Power

Thrust Power

Effective Power

Various Efficiencies

Fuel Consumption

Economic Speed

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