Main Engine High Exhaust Temperatures

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Main Engine High Exhaust Temperatures

Postby Pengze » Sun Nov 11, 2012 4:30 am

Dear Sir,
For a 4-stroke diesel medium speed engine operating on 180cst, the remedial works were carried out as below but we still encounter high exhaust temperatures on all units, anybody out there would like to share & advise for troubleshooting:-
1. All cylinder heads were overhauled & replaced.
2. All fuel injector nozzles were renewed and pressure tested as per maker's manual.
3. All the valve tappet clearances were found to be in order.
4. All the piston rings were renewed.
5. All the fuel pump timings were checked and found satisfactory.
6. The air cooler was ultrasonic cleaned.
7. The turbocharger was recently overhauled.
8. The air inlet temperature into the main engine was kept at optimum just below the dew point, slightly above the engine room ambient temperature.
9. The fuel pump & governor rack indexes were found to be within range.
10. The economizer / boiler smoke tubes were hosed down.
11. The funnel exhaust smoke colour is colourless / normal.
12. The inlet fuel temperature / viscosity into the main engine is within the range.
13. The cylinder peak pressures are okay corresponding to the power output.

These baffles us why the problem is still there.
Still searching for clues.

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Re: Main Engine High Exhaust Temperatures

Postby JK » Sun Nov 11, 2012 4:51 am

How dirty is your hull?

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Re: Main Engine High Exhaust Temperatures

Postby Big Pete » Mon Nov 12, 2012 12:47 am

Hi again Pengze,

To properly clean the exhaust gas economiser takes many hours of water washing, I remember there was a dicussion about this earlier, in this Forum. The problem being that you can not discharge the dirty water from washing the economiser overboard when in Port and you can't waterwash the the Economiser when you are at Sea because the engine is running. If you let the water go into the Bilges you will have to pump it overboard via the OWS and the carbon/soot from the economiser will totally destroy the filters in the OWS.
The best system would be to have a tank holding acouple of tons of water and pump that through the Economiser letting it drain back to the tank and keep circulating for 24 hours or longer, pressure is not important but you must have a good flow rate to ensure that the water washes all the tubes thoroughly, I think Jimmy pointed out that if the soot was only partially washed off there was a very high risk of a Carbon fire starting in the tube nest.

Once you are well out to Sea you could pump your circulating tank overboard because it does not contain oil, only Carbon and it has never been in the Machinery Space Bilges. BUT NOT in USA waters because it would cause a discolouration of the surface which is illegal there.
Hope all this helps.

It is always better to ask a stupid question than to do a stupid thing.

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Re: Main Engine High Exhaust Temperatures

Postby Pengze » Mon Nov 12, 2012 7:20 am

Dear Sir,
For the Hull conditions, we could not determine.
I wonder if the propeller is entangled with fishing nets and ropes will cause the exhaust temperatures to rise substantially.

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Re: Main Engine High Exhaust Temperatures

Postby jimmys » Mon Nov 12, 2012 7:24 am

What is the condition of your liners you do not mention them. You must have taken sizes. Did you put the delapena hone through them to grind the glaze. At a certain stage the liners need to go for reconditioning.
Consider a high performance ring pack . Expensive but well worth it. A number of the UK ferries have them in now with very good results. They make them for Pete's favourite the Peilstick PC4. I sailed with that as a tanker engine in years gone by. Wish I had them then. A nightmare.


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Re: Main Engine High Exhaust Temperatures

Postby Mikkelsborg » Wed Jan 02, 2013 4:23 am

This could be caused by a blocked nozzlering in the turbocharger, or poor turbocharger performance........
What make and turbocharger type is fitted ?
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Re: Main Engine High Exhaust Temperatures

Postby JFC » Wed Jan 02, 2013 3:41 pm

You donot say what kind of propulsion system you have.

Did you perform any work to the propulsion shafting and propellers? Change props/Pitch, tailshaft bearings etc...If the bearings are tight or to poor fit, and or poor manufacturer they may swell or result in higher exhaust gas temps. Also if you were on dock for a sustained period of time without any protection from foreign debris entering the bearings or strut bearings etc.....
Damage to oil lumbricated bearings or shafting missalignment.

Also don't overlook timing of the fuel pumps too.


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Re: Main Engine High Exhaust Temperatures

Postby DJB » Sun Aug 25, 2013 9:14 am

Realize that this is late to the discussion however it is about sharing of knowledge.
We had this issue on the ship that I was C/E on, MAK VM32C-16, 10,000 hp.
Went through the same process, came down to a damaged intercooler for the turbo chargers. Replaced unit no further trouble, which was a relief as constantly answering exhaust alarms was a real pain not to mention distracting.
Was amazing how little damage it took to create this condition.

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