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Function of diesel engine - Preparations for standby, starting,reversing and running at full speed

Marine diesel engine operation
: The diesel engine is a type of internal combustion engine which ignites the fuel by injecting it into hot, high-pressure air in a combustion chamber. In common with all internal combustion engines the diesel engine operates with a fixed sequence of events, which may be achieved either in four strokes or two, a stroke being the travel of the piston between its extreme points. Each stroke is accomplished in half a revolution of the crankshaft.



Main Engine Power and Vibration
The normal service power of the Main Engine must be maintained as instructed in the vessel's commissioning letter unless otherwise directed by the Company, except under emergency conditions involving safety of life or safety of the ship.
Should the vessel's normal service power require to be altered the fact, together with the reason for the alteration, is to be reported to the Company and noted in the Engine Log Book. The Chief Engineer is to take instructions from the Master for the specific voyage requirements, always keeping within safe operating parameters.

Vibration can cause severe damage to machinery, bearings, pipes, fittings, instrumentation and structure. To minimise this damage the main machinery must be regulated at all times to avoid speeds at which excessive vibration may be experienced. Besides the barred-speed ranges prescribed by the engine designers, operation at certain speeds where the combination of draught, trim and weather leads to severe vibration, is also to be avoided.

MAN B&W engine
Fig: MAN B&W L70MC engine

Particular attention must be paid to the balancing of cylinder loads in Diesel engines and to the tightness of holding down bolts on all reciprocating machinery. Full use must be made of all condition monitoring equipment supplied to detect and measure vibration, and any significant increase in vibration levels that cannot be accounted for must be reported to the management ashore.


Warming Through

Main engines are to be warmed through gradually following a stay in port or other occasion when they have been shut down. The jacket water circulation temperature is to be raised over a period of time to as near to the operating temperature as possible. The period of time is dependent on the jacket water temperature prior to the commencement of circulation, the heating medium and size of main engine etc. As a general rule circulation should commence not less than 12 hours before the estimated time of departure. Other circulating systems are to be put on line during this period i.e.
Precautions Prior to Standby Departure

All circulating systems are to be as near as is possible normal operating parameters according to the manufacturer’s instructions for the engine type. On vessels where the engine or engines are directly coupled to the propeller or propellers, the Deck Officer of the watch or Duty Deck Officer is to be contacted and permission to turn the engine requested. Once the Deck Officer has confirmed that this can safely be carried out, then and only then can the engine be turned.

All the indicator cocks are to be opened. The engine is then to be turned a minimum of one revolution with the turning gear during which time the indicator cocks are to be sighted for any evidence of oil or water discharge. If this test is satisfactory, then the indicator cocks are to be shut and the turning gear disengaged. It is of the utmost importance that the disengagement of the turning gear is physically checked. No reliance is to be placed on the indicator light in the control room, interlocks etc. It is the Chief Engineer’s responsibility to ensure that this physical check is carried out.

On vessels where the engine or engines are directly coupled to the propeller or propellers, the Deck Officer of the watch or Duty Deck Officer is to be contacted and permission to turn the engine on air requested. Once the Deck Officer has confirmed that this can safely be done, then and only then can the engine be turned on air. All indicator cocks are to be opened. In conjunction with the Bridge and as applicable, the engine is to be "kicked" ahead and astern on starting air. The indicator cocks are then to be closed.

Following the satisfactory turning of the engine on air, the Deck Officer of the watch is to be contacted and permission to turn the engine on fuel requested. Once the Deck Officer has confirmed that this can safely be done then, and only then, can the engine be turned on fuel. In conjunction with the Bridge the engine is to be turned dead slow ahead and astern on fuel.


Operation on Heavy Fuel Oil

Main engines designed to manoeuvre on heavy fuel oil are to be operated according to the manufacturer’s instructions. In the event of problems during manoeuvring on engines using heavy oil there must be no hesitation in changing over to diesel oil irrespective of whether the engines are being operated using bridge control, or using engine room control.

It is the Chief Engineer's responsibility to inform the Master of the particular engine type’s maximum period that it can safely remain in the stopped position. He is also to inform the Master of the procedures which will have to be carried out if the particular engine type’s maximum period at standstill during manoeuvring is exceeded.


Preparations for standby

1. Before a large diesel is started it must be warmed through by circulating hot water through the jackets, etc. This will enable the various engine parts to expand in relation to one another.

2. The various supply tanks, filters, valves and drains are all to be checked.

3. The lubricating oil pumps and circulating water pumps are started and all the visible returns should be observed.

4. All control equipment and alarms should be examined for correct operation.

5. The indicator cocks are opened, the turning gear engaged and the engine turned through several complete revolutions. In this way any water which may have collected in the cylinders will be forced out.

6. The fuel oil system is checked and circulated with hot oil.

7. Auxiliary scavenge blowers, if manually operated, should be started.

8. The turning gear is removed and if possible the engine should be turned over on air before closing the indicator cocks.

9. The engine is now available for standby.

The length of time involved in these preparations will depend upon the size of the engine.


Engine 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.A separate air start button may be used.

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.




Engine reversing

When running at manoeuvring speeds:

1. Where manually operated auxiliary blowers are Fitted they should be started.

2. The fuel supply is shut off and the engine will quickly slow down,

3. The direction handle is positioned astern.

4. Compressed air is admitted to the engine to turn it in the astern direction.

5. When turning astern under the action of compressed air, fuel will be admitted. The combustion process will take over and air admission cease.


When running at full speed:

1. The auxiliary blowers, where manually operated, should be started.

2. Fuel is shut off from the engine.

3. Blasts of compressed air may be used to slow the engine down.

4. When the engine is stopped the direction handle is positioned astern.

5. Compressed air is admitted to turn the engine astern and fuel is admitted to accelerate the engine. The compressed air supply will then cease.



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