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Wartsila’s User Group Forums 50 SG Engine MFI trips – troubleshooting root cause

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  • #2090

    Good Morning All,

    We now have around 1600 hours on our 4 50SG machines and continue to have random MFI trips due to either the SOGAV sticking/leaking or the prechamber gas valve doing the same.   We have been replacing the SOGAV first when this problem arises as it is the easier fix, but on several occasions the issue has been the prechamber, and we can’t see any difference in the symptoms.

    Has anyone out there been able to determine from operating data which of these two possibilities is the root cause of their MFI trips?

    We’d also like to know just what inputs to the UNIC cause the MFI trip…..the information we’ve been provided is somewhat vague.

    Thanks in advance for any tribal knowledge,

    Dave Mordecai, City of Tallahassee

    Ruben Tellez


    What type of Alarm are you getting? is Low MFI? High MFI or MFI Max duration exceeded?




    Ruben, Dave is on vacation this week, but the alarm and trip that we are experiencing are the MFI duration exceeded.


    Pat Faircloth

    Hopkins Plant Mgr.


    Jeremy Saar

    Reset the control power to your UNIC. It should zero out your MFIs to prevent the MFI duration max time.


    MFI duration exceeded is a symptom, not the cause. You need to backtrack the scenario to see what started it. The quickest response time to capture what is going on will be at the local display at the engine. The log in the control room will just muddy up your troubleshooting. Usually we’ll see the MFI trip generated from high cylinder pressures which can be pretty broad. Are you seeing this at a particular load?


    We were getting MFI trips on all units sporadically. However, one of our units was the worst offender. At one time it was tripping almost everyday and sometimes multiple times per day. Then we went about 2 weeks and had no trips. One thing we noticed. When the worst offender was tripping almost everyday the humidity was high and it rained nearly every day. During the two weeks that it didn’t trip it was hot and dry. Today we had rain and the worst offender tripped again to MFI duration exceeded. Has anyone made a correlation with MFI trips and humidity?


    A lot of things change with weather swings. Study your run issues while taking note of charge air temps. They want intake temps at 114 F. If you start climbing into the 124 F and up things will get less stable. What are you’re engines rated at? We top off at 18.9 MW and it’s a tight line when any contributor is less than ideal. Open your charge air drains when you’re at full load on a humid day it will show you how much water they can run with. What they don’t like is unstable fuel delivery, quality or pressure. Keep an eye on that.


    We’re rated at ~18.9MW as well. There is a service bulletin on the charge air drain pots. We’ve filed a warranty claim, but we leave the drain pots cracked open now to keep them free of water.


    We elected to just run open tubing to the floor. 3/4″ Swagelok. Does not affect charge air reference. 18.9 is an ambitious number. Take a look at how fast of a ramp rate they left you with.


    Our CA temps are running 130F plus on a typical 90-95F day.  Will be interesting to see if our reliability improves this fall with reduced temps and humidity.

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