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Wartsila’s User Group Forums 50 SG Engine Raw NOx from engine

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  • #2139

    We have 4 18V50 SG engines and we have had several problems that lead us to believe the engines were not tuned correctly. Dave Mordecai and Pat Faircloth have already posted about the MFI trips we have been having.

    We’ve also had many failures of the HUG SCR measurement system and the HUG rep noticed there was a lot of ‘soot’ in the sample lines. After this, we also noticed that the raw NOx from the engines is not stable. On one engine it varies from 150 ppm to 130 ppm when there is no change in load, fuel gas pressure, charge air pressure or any other combustion parameter we can think of.

    Are other users seeing the same variation in NOx from the engine? Anyone else have soot in the HUG systems?

    I have a trend of our NOx if anyone is interested, send me an e-mail.

    Mike Muhly



    Steven Osgood

    Port Westward has never seen “soot” in the lines but we continually fight our HUG system to stay in compliance.  We have had HUG out twice to “tune” our system at various loads.  This worked for about 2 weeks and then back to fighting the system.

    Jeremy Saar

    There might be charge air pressure fluctuations or wastegate movement. Fluctuations is the waste gate will cause significant nox spikes. I have also seen faulty sensors cause a short and make the engine load fluctuate a few percent up and down and during those swings the nox will fluctuate that much.


    We have 34’s but noticed when we had alot of raw nox when the waste gate on one of the engines was out of whack.  We recently we to the bridge type spark plugs and the raw nox inlet droped 30-50 ppm.  It was enough that we retested for our air permit due to using too little urea (not able to make our minimum 4.2 gal/hr over 3 hours).

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