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Greetings team members,

Diesel Generators onboard ships about 600-1000 kw rating, YANMAR make, Axial vibration around crankshaft. The present video vibration is too high and instrument showing Over.

The other video on crankshaft top but slightly away from the crankshaft showing satisfactory.

There are many other taken bottom of crankshaft, left hand side and right hand side found vibrations are lower than top of the shaft.

Appreciate your feedback and I will add the spectrum in later stages as per your request.

regards

chary

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Videos (2)
DG1 Crankshaft top 2
DG1 Crankshaft top away from Shaft
Original Post

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The 1st video has accelerometer mounted on a thin flange of a cover. It would be good to check mounting location by moving to the engine case/block.

If the signal is real and causing accelerometer overloads, then check for dominant frequency in spectrum and view the acceleration-time waveform for impact events.

If vessel has two D-G, then make comparison measurements including on the auxiliary components (water and oil pumps). Any other signs of poor condition such as cylinder pressures and temperatures and lube oil flow and temperatures?

Walt

Mr. Oli we did not had any damper and the shown gear train sketch is for your guidance.

Mr. Walt for your queries the following are below. Feel free if you need anymore queries. From Engine makers response is very slow.

The 1st video has accelerometer mounted on a thin flange of a cover. It would be good to check mounting location by moving to the engine case/block.

ANS: This cover  flange is for the access to Marin driving gear of Crankshaft. Attached the document. The nearest to Crankshaft position to measure Axial vibration. This flange is robust one and fully secured on to the Engine casing.

If the signal is real and causing accelerometer overloads, then check for dominant frequency in spectrum and view the acceleration-time waveform for impact events.

Ans: The spectrum I will share with you. Rpm 900 and the Axial spectrum with 23.85 mm/s overall recorded and when displaying the value is over the instrument in that position.

If vessel has two D-G, then make comparison measurements including on the auxiliary components (water and oil pumps). Any other signs of poor condition such as cylinder pressures and temperatures and lube oil flow and temperatures?

Ans: Vessel has 3 DGs and No.3 is ok No2 is moderate and No1 is too excessive. Attached around crankshaft vibrations axial, Port side is satisfactory other top, bottom, stbd showing high vibrations.

Appended most of the data and many videos recorded in all 4 points of crankshaft top, bottom, Port and Stbd directions Axial vibrations.



DG1 Vibration reading at Engine NDE Free End

ENGINE NDEHVA
Velocity mm/s / Acceleration g8.79/15.676.57/15.4153/0.01


DG2

ENGINE NDEHVA
Velocity mm/s / Acceleration g14.54/24.638.32/18.9923.93/28.51

DG 3  

6.04/10.25.95/9.8113.3/13.5

Thanks and regards

Chary Tatta

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Images (11)
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Torsion dampers are common on such in one or both ends, not necessarily a part of the motor drivetrain but attached outside. Reason for asking is that this is a part with limited operational life that require frequent maintenance or inspection depending on type eg. a few years or so and not always cared for.

Next question, did you check the floor mounting? Rubber feet or shockfast type of mounting? Is it the same looking on all 3? Including the steelworks, any cracks or similar? 

Greetings Mr. Oli

Thanks for your quick reply.

Your first point: Torsion dampers are common on such in one or both ends, not necessarily a part of the motor drivetrain but attached outside. Reason for asking is that this is a part with limited operational life that require frequent maintenance or inspection depending on type eg. a few years or so and not always cared for.

What you said is very correct. However, It appears, YANMAR is not provided such Torsional dampers, present the makers Engine manual of this model is not with me to refer and I wrote to the YANMAR service team about this issue. Once some info arrives from them, I will share in this forum.

Your 2nd Point: Next question, did you check the floor mounting? Rubber feet or shockfast type of mounting? Is it the same looking on all 3? Including the steelworks, any cracks or similar?

There are 5 nos of resilient pads on each side support for each engine and all 3 DGs are provided. Images attached.

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Images (10)
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So did you check if the compression is about the same on pads on the 3 motors?
Just to check from what you can see on pictures, there are no obvious problem anyway.
So if it end up a gear problem? I had a similar problem on a Mitsubishi last year in 1 unit on a brand new set of dieselgens for a hospital and I could estimate what gear that was the problem as it was not that bad so I got FFT data to look at.
Final it was the old test to have a look at the oil, we just pulled the dipstick and took a look at a clean cloth and it was no argument, real disaster metal particles all over and relative large. You can also listen to it with a screwdriver to your ear protector, it should sound like a disaster......
So if you can measure a bit further away so you don't get overload and get data to analyze it would be good, and have a look at the oil. If it is bad there are not really any analysis required it is quite obvious. You can also do the old trick and compare the weight of the oil filter to one of the good ones.

Greetings Mr. OLI

Pleased to see your interests and quick response.

1. So did you check if the compression is about the same on pads on the 3 motors?

Ans: There is no issue of the resilient mounts as the Alternator end/Engine end radial vibrations appearing in limit.

2. Just to check from what you can see on pictures, there are no obvious problem anyway.
So if it end up a gear problem? I had a similar problem on a Mitsubishi last year in 1 unit on a brand new set of dieselgens for a hospital and I could estimate what gear that was the problem as it was not that bad so I got FFT data to look at.
Final it was the old test to have a look at the oil, we just pulled the dipstick and took a look at a clean cloth and it was no argument, real disaster metal particles all over and relative large. You can also listen to it with a screwdriver to your ear protector, it should sound like a disaster......

Ans: Gear problem in FFT not significant and gear mesh amplitudes are not considerable. 5Hz/300 rpm  most probably resonance is the issue due to various reasons.

As you see the cleanliness of DG areas and the operation doesn't show any serious problems and engines are running satisfactory.

Marine Engineers are capable of handling normal issues, being myself Ex marine Engineer and Technical superintendent, physically not in a position to justify any problem with this AXIAL vibration.

Lube oil, No doubt an issue, however, marine engineers normally take care of Lube oil issues.

I did not see serious issue during operation, however, alarming is the Axial vibration, Thrust bearing issues, Crankshaft deflections, Main bearing issues, coupling issues and alignment issues.

Out of 3 Diesel generators one DG is serious, No2 DG is above IACS limits and No3 DG is satisfactory.

Looking all above, I asked the Company managers to have extensive search about thrust bearings, Gear train, Shaft deflections, Main and Connecting rod bearings, Piston cooling issues to verify and looking forward hearing from them.

regards

Chary Tatta

+6597558166

1. Yes but if feet are deteriorated just in one end it may get a waggling movement. So yes that is to make sure no tilting axial resonance is the problem. yes it is a abnormal nice looking vessel. However not all oil problems are showing external in this case from last year it was parts of a broken gear that showed up in the oil. It that case nobody did look at the oil, they just swapped filters and oil so it happens.

So next is if you did look at the coupling but normally it also should get some indications in the generator but there are exceptions. Some generators have a axial bearing in the free end so the generator shaft expands in to the gearbox or diesel when getting warm and OEM claim it is supposed to be like that and it require larger axial play in the coupling to take care of that or you get axial problems in the gearbox/diesel.

So yes in the end it may be a cylinder unbalance maybe, just to check the obvious I take a vibration reading at all injectors to sort out if there are any that is different then it is worth to check them.

Great Mr. Oli, Pleased to see your quick reply for my messages-

1. Yes but if feet are deteriorated just in one end it may get a waggling movement. So yes that is to make sure no tilting axial resonance is the problem.

Ans: Very correct. But radial vibrations and Alternator end Axial vibrations are in satisfactory levels.

2. yes it is a abnormal nice looking vessel. However not all oil problems are showing external in this case from last year it was parts of a broken gear that showed up in the oil. It that case nobody did look at the oil, they just swapped filters and oil so it happens.

So next is if you did look at the coupling but normally it also should get some indications in the generator but there are exceptions. Some generators have a axial bearing in the free end so the generator shaft expands in to the gearbox or diesel when getting warm and OEM claim it is supposed to be like that and it require larger axial play in the coupling to take care of that or you get axial problems in the gearbox/diesel.

Ans: At next opportunity we will explore those issues. Normally Lube oil is the major issue and now present engines are running with VLSHFO (very Low Sulphur Heavy Fuel oil) and This company normally take care of such issues regularly. However, we should get an opportunity to identify the engine performance too.

3. So yes in the end it may be a cylinder unbalance maybe, just to check the obvious I take a vibration reading at all injectors to sort out if there are any that is different then it is worth to check them.

Ans: We should study something more on this issue, this is not only the company but many YANMAR diesel generators are exposed to this type of Axial Vibration problem.

We will appreciate if you also can explore from your end to trace the real issues.

Kind regards

Chary Tatta

The waveforms look very high amplitude and odd pattern (or lack thereof) and the analyzer/meter indicates overload. There are no high frequencies in the spectra, so the overload would have to be from much higher frequencies;  from impacts. This is consistent with the fact that about 12" away the amplitude is much less; suggesting high frequency. The generator drive bevel gear is suspect for producing axial vibrations and worthy of a visual inspection.

The low frequency at 5 Hz is perhaps from propeller blade rate (if underway) or another machine or general resonance on the mounts. At 5 Hz the entire engine-generator should have about the same axial vibrations at both ends.

Nice clean engine room to work in!

Walt

Greetings Mr.Walt,

1. The waveforms look very high amplitude and odd pattern (or lack thereof) and the analyzer/meter indicates overload. There are no high frequencies in the spectra, so the overload would have to be from much higher frequencies;  from impacts. This is consistent with the fact that about 12" away the amplitude is much less; suggesting high frequency. The generator drive bevel gear is suspect for producing axial vibrations and worthy of a visual inspection.

ANS: Thanks for your assessment Mr. Walt Strong, Yes the gear train end is the issue, however, in a similar engine, other vessel, we requested for Gear train Inspection with makers service Engineers and reported that No gear train deficiencies found. Thrust bearing is another to check, Crank shaft deflections another important parameter.

At the alternator end the vibrations are found normal only Engine side Axial is high. here also we have requested Ship managers to check the gear train, shaft deflections, thrust bearings, Engine Resilient pads. Once the vessel come out with all details we will put the details here for case study observations.

2. The low frequency at 5 Hz is perhaps from propeller blade rate (if underway) or another machine or general resonance on the mounts. At 5 Hz the entire engine-generator should have about the same axial vibrations at both ends.

Ans: 5Hz I am finding many DG vibrations list. The point of 5Hz values at both ends to be verified. These engines are connected Alternators and no propeller issue other than alternator cooling fan.



Once again thanks for your professional interests and responding to this case studies. If you feel any additional data is required, I will try to workout at next vessel.

Nice clean engine room to work in!



Thanks and regards

Chary

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