Daihatsu 6DC-17 High exhaust temperature

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BsV
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Daihatsu 6DC-17 High exhaust temperature

Post by BsV »

Hi everyone, As a newly promoted 3E am a bit stuck with where to start with. All 3 generators are showing exhaust temperature of 500 degrees in 50 to 60 percentage load. The boost air temperature is around 46 to 53 depending on load and engine room temperature remains between 38 to 44 degrees. I've checked the injectors and cylinder head was recently replaced by the last 3E. What else should I look for. The fuel racks are showing the values around 5 points more than shop trial. Kindly give some suggestions. Thank you
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Merlyn
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Re: Daihatsu 6DC-17 High exhaust temperature

Post by Merlyn »

All three exhausting to a common uptake/exhaust?
Minor blockage = increased exh. temps?
Funny it's common to all three?
Law of averages demands all three can't have the same problem so I would look for a common factor linked to all three maybe.
Can you measure back pressure without drilling/tapping into piping and inserting psi gauge?
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.
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JK
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Re: Daihatsu 6DC-17 High exhaust temperature

Post by JK »

what is the water temp to the CA coolers? Are you on a central cooling system or is the recirc sending the water back to the engines?
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Re: Daihatsu 6DC-17 High exhaust temperature

Post by Atlantic »

How is the temps recorded? Local or remote. Check that it’s showing the true temp. What fuel are you running on?
popeye62
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Re: Daihatsu 6DC-17 High exhaust temperature

Post by popeye62 »

Atlantic asks a crucial question; are you burning HFO? At continual low load it will become a problem. I don't know if 50-60% is low load in this case. I have a manual which states that low load is below 90kWe. Engines without VIT cannot cope with low load very well, I can't figure out the electrical load as I don't know the capacity of the alternator or the power developed by the engine at MCR. As Merlyn says the problem is common which is combustion and scavenging and the uptakes are worth looking at especially if they combine into one and use one silencer which can rot away without anyone noticing. Also not likely a timing problem. Look at the system as a flow of air and start at the beginning; is there enough air in the engine room? An odd question you may think but are the ER doors hard to open when the D/A and ME are running? Are any of the supply or exh fans off? If you don't have an air pressure monitor in the ER you can make your own manometer. Next is the filter cloth 'Bondini' around the T/C intake/silencer that you replace...how often? Does it get dirty quickly? Next the T/C itself, is it running at the right speed, the 'normal' speed or better still the test-bed/sea trial speed? Does it bark at load changes? You are religiously cleaning the compressor every 24 hours at the stated load and washing the gas-side turbine every 500 hours? If you don't water wash then DO NOT start now. Following the gas back into the engine, is the nozzle ring restricted/blocked? Is there a protection grid for the T/C and is it restricted? Is the exh manifold space thick with carbon or showing wet oil. Next is the exh valve but the heads were replaced. Were they all replaced or overhauled with valve/valve gear etc? The temp. of 500 is at the T/C inlet (the alarm for cyl. outlet is 500, T/C inlet 600) so within limits but too high for me, the T/C should be dropping the exh inlet temp by at least 100 degrees. 400 at outlet? What happens if you pile the load on, temp go up or down? Following the air from the compressor wheel through the diffuser, what is the pressure? this is a crucial parameter and so is delta P, the pressure drop across the charge air cooler (it's what we call boost air). The manual does not give a limit but I would say no more than 100mmW. How often/are the coolers cleaned air-side/water side? ultrasonic is best. The temp seems reasonable (pre-cooler it will be >100 if it is a high power engine) Clean scavenge spaces? Get the engine up to 85% and take a full log when stable. Use your PMI equipment to check the performance, if you don't have any tell the chief to order a Kistler, a Doctor Diesel, a Malin or any of the others on the market. You will use it a lot. An increase of fuel pump index, when everything else is the same is indicative of worn pumps. Tell the chief you want a freshly calibrated gauge for the injector test rig.
BsV, it is daunting going from 4E to 3E and I am making an assumption that the path is the same as the British Merchant Navy. Who cares as a 4th if the separator falls over or you forget to put tablets in the shit tank? Even as a 2nd I have lost the main engine and got it back on before the bridge even noticed but when the generators fall over everyone and his mum knows about it, but don't worry you 'should' always have a spare and you can concentrate on YOUR generators. To get you to the top of the 3E charts know everything about your generators inside and out and write it down in the PMS, use it to its best, I don't know what you use but they are only as good as the information in them so use it well. Specifics; Never adjust a rack because of an exhaust temp, always keep the T/C as spotless as you can but the best thing I can tell you is to keep the LO clean. The thing is, BsV, the 4E has the most crucial job on the ship when it comes to development of an engineer and the breakdown history and the insurance history of the vessel, and no, it's not forgetting to put tablets in the shit tank it is operation of the separators. After 20 years at sea in 30+ ships, the majority of which nobody wanted to join and 10 years as an investigator for lawyers, underwriters, clubs, charterers and owners I have seen just about everything and 95% of failures have a lack of treatment of either FO or LO as a significant issue. A separator can run all day long at the right temp and the right back pressure but not actually doing anything. You probably don't purify these sumps and I can't see in the manual the time for an oil change but do the analysis and clean/change the sumps regularly. There is a lot of noise about 'bad fuel' and yes, engines do run on bad fuel but they run IN LO, I cannot stress this enough. Once you have the oil sorted and there are no fuel leaks sort out the JCW quality.
Finally, make sure the parts comply with the Nox technical file as you are likely non-conformant if you are logging high temperatures (never flog a log, someone will find out!). Make sure there is no smoke or PSC might get interested
Good luck. Did the lights just dip then...just joking.
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