Causes of marine auxiliary engines hunting problems, encountered during operation

CAT ENGINE

The engine has started but there is a fluctuation in the RPM. You think that the tachometer cable might have broken but you hear the sounds of acceleration and de-acceleration. The governor linkages are moving like crazy sometimes increasing the RPM and sometimes decreasing it. The auxiliary engines have an Isochronous governor, which means that the engine has to operate at a constant speed after starting. "Iso" means same and "chronus" means speed and thus it is supposed to be a constant speed governor, unlike the main engine governor, which you can run at various speeds. 

How to troubleshoot or service? 

Firstly,  stop the engine,  if  already on loaded condition ,  Transfer load and stop the engine and check the following reasons ;

1) The engine is cold and leads to uneven combustion. This can be caused by forgetting to put the engine on pre-heating after stopping last time. Check for the engine temperature before starting,  it should maintain 35-40C.  Check the Golden book ( manufacturer manual)

2)  The tachometer or its wire may be out of order. They may be rubbing, or the pin might have turned round and is about to give in. Try lubricating the wire, or changing the tachometer.

3) The fuel line may be having air. Yes!, now you remember you had changed the filter but had forgotten to purge the air and prime the system. This is a good time to do it.

4) Some fuel injectors getting stuck and firing intermittently. This might happen in engines which are run on Heavy fuel oil. These engines are supposed to be changed over to diesel oil for approximately half an hour before stopping. The half an hour figure is only a rough guide line, practically the purpose is to flush the pipe lines.

5) Faulty governor;the governor oil is supposed to be removed and spaces flushed with clean kerosene, before filling up with oil again. Sometimes the pilot valves have some sludge stuck and hence the hunting.

Reference,

Introduction to Marine Engineering: by D.A. Taylor

Maritime power plants and maintenance.

Reason why safety valve may open.

In a very good day,  you happily move to the generator or your marine diesel engine for starting process. Lets say you have blown through the generator by air or hand tuning and when you start it, there  came a loud sound like “tat.. tat.. tat.. .” Probably very afraid, thinking it is a crankcase explosion... Thank God it was not. Suddenly realization dawns; you saw safety valve that has lifted. It lifted because there is an uncontrolled combustion inside the cylinder which can be due to the following:

A. Defective fuel oil valves.

B. Wrong fuel pumps timings.

C. Engine is over cooled.

D. Dripping fuel injectors.

E.  Fuel linkage problems or fuel rack stuck in maximum position.

F. The opening pressure of the safety valve is low caused by a broken spring or a loosened nut.

Actually,  on the modern engines,  some other safety measures has been put in place to manage such conditions.  We will discuss that in the next article.  Subscribe with us for more.

Starting Problems On Marine Auxiliary Diesel Engine

On this article, I will like to briefly explain the various causes of Marine Auxiliary engine problems. I hope it would prove beneficial for junior engineers as well as practicing marine engineers.

THE DEFINITION OF MARINE AUXILIARY ENGINE!!

Marine auxiliary diesel engines are used for the production of electricity on board merchant or offshore ships. They are called auxiliary because the main diesel engines are used for the propulsion of the ship. The auxiliary engines are generally four stroke diesel engines. It could be air or battery starting... It doesn't matter.

Lets say you come on your normal watch and find out that the Chief Engr or second Engr has written a note instructing you to change over the generators because the 250 -  500 hour routine of the running generator is due..After you take a round, check the various parameters of the running machineries and then go to the generator platform. After checking the level of the oil and opening all the valves you blow through the engine and then close the indicator cock ( if Available) . Now you give it an air or battery kick and engine keep turning but the engine does not pick up. You try again and the same result. Now need to troubleshoot.

The Troubleshooting Marine Auxiliary Diesel Engines (Engine turning but can't start).

Below are the areas you most troubleshoot :

1. Fuel does not reach the fuel injection pump because there is air in the system.

2. The fuel oil filters are choked.

3. The fuel line valve is not open.

4. The trips have been not reset after the last stopping.

5. Fuel oil service tank is at low level. Beware the other generator is also going to stop.

6. There is water in the line.

7. The fuel valves are faulty and not giving proper atomization or are choked.

8. The fuel pump timing is wrong.

9. Leaking fuel injection pipes.

10. Seized plungers of the fuel pumps.

11. Fuel rack linkage stuck in position.

12. Seized delivery valves or broken plunger springs in injection pump.

13. The engine is cold.

If you check all the above mentioned,  and still not to start,  you need to check the electrical side (E.g the governor connection).

There are other problems that can cause not starting... We shall discuss that in the next article.  Subscribe with us and stay tuned.

Why Seafarers are always in hurry, on sign off day?

If you are a seafarer,  you will note that being at sea is the most difficult time,  in the terms of missing your Family and friends. Sometime you won't communicate with them for months.
 
The above reason makes most of the seafarers during there sign off time,  they don't even remember to collect all there documents or the required information they will need in the next sea sign on. 

Please we urge you all,  to always pay good attention during sign off and pick all required by you.

Happy weekend to all our blog readers...

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