Cavitaton damage on Crank Pin

[0208DAC]

Hi,

Since two years ago we experienced, on different V18 diesel engines in our company, pin hole damages on the crank pin of the engines. It is suspected that the lube oil pressure drop to the point that cavitation occur always at the same place. These damages in the engines occur every time at the same place on the crank pin but in different cylinders. The cavitation occur at the lube oil hole in the big end bearing which guide the lube oil into the lube oil channel which guide the lube oil to the piston crown area.

Besides the pin hole damages on the crank pin, the big end bearing also experience scratches in the center of the bearing.

Did anyone experience anything like this before? what could be causing this phenomenon?

Any comment is appreciated.

Thanks in advance

 

[MikeHalloran]

Do the engines sit idle at any time?
Does the lube oil get hot enough to boil off any water in it?


Mike Halloran
Pembroke Pines, FL, USA

 

[0208DAC]

@ MikeHalloran

No, the engines are supposed to run continuous but depending on the power demand (at lower demand) they are turned off and as soon as the power demand increases they are turned on.
The lube oil is cooled and the maximum allowable temperature is 65 degree Celsius.

 

[MikeHalloran]

A while back, I did a pair of NG engines for GOM. They had oil heaters, which ISTR were set to a minimum of 105C.

You might want to talk to the engine manufacturer about oil temperatures.


Mike Halloran
Pembroke Pines, FL, USA

 

[Tmoose]

I'd be interested in pictures of the damage.
Nice extreme closeups of the "pin holes" in the crankshaft especially, and an indication of the pitting angular location relative to the crank rod journal oil hole would be good.

Is the damage noticed during a routine inspection?
or, were the engined disassembled to accomplish signficnat repairs or overrhaul?
Are there records of previous overhauls, specifically if the crankshafts showing pin holes were weld repaired and re-ground?

RE: cavitation damage
No experience.
Standard bearing (insert) damage evaluation documentation does not seem to mention cavitation.

http://www.remotech.info/uploads/clevite_lagerschade_tech_info.pdf

RE: scratches in bearing insert
"the big end bearing also experience scratches in the center of the bearing."
Do the scratches in the bearing insert align more or less with the pits?
Are the scratches inline with the oil hole?

It is pretty common for inserts (and even the crankshaft) to show a little light scratching even on freshly assembled and carefully cleaned new and rebuilt engines with quality oil filters.
This ( "race engine" ) bearing insert scratching is more severe than i'd expect from a carefully assembled, well maintained engine, but if it was from a 100kmile plus street engine a lot can happen.

This crank scratching is pretty severe, but confined pretty well to the area swept by the oil hole, which is where circulating particles would join the party.

http://i754.photobucket.com/albums/...p 1986 4x4 Peppy/22RE_crank_rod_journal_4.jpg

Is there debris embedded in the inserts of rod journals with "pin holes?"

If the "pin holes" are indeed cavitation or some other phenomenon creating wear debris then it is generated in a good place to proceed directly into the oil wedge film.

 

[0208DAC]

Hi,

The engines are V18 with 320 mm pistons. So they are big engines with 720 rpm. Do the lube oil viscosity, flow, temperature or pressure have a direct impact on the cavitation on crank pin.

Did anyone experienced anything like this?

Thanks in advance.

 

[JJPellin]

In one of our hydrogen recycle compressors, we found damage in the groove of the crank pin bearing that had the appearance of cavitation. We have never seen this damage on the crankshaft. Our machine is a 4000 HP, three stage, four cylinder double acting reciprocating compressor running at 330 rpm. We were never able to determine the cause of this damage.

Johnny Pellin

 

[0208DAC]

Hi,

@JJPellin thanks for sharing you experience.

What was the action taken regarding your case?

 

[Tmoose]

King Bearings have a very good reputation in some sectors of the high performance automotive world.

This is what they have to say regarding cavitation damage to bearing inserts, and how to prevent it.
pages 7 and 8.

http://kingbearings.com/files/Engine_Bearing_Failures_and_How_to_Avoid_Them.pdf

 

[0208DAC]

Hi,

@Tmoose. Thank you for the informations.

 

[JJPellin]

We were not able to find a cause for our damage and took no action to prevent it in the future. We would normally only get a chance to inspect these bearings once every 6 to 10 years. So, it will be some time before we get to see if the problem persists.

Johnny Pellin

 

[Tmoose]

Hi 0208DAC,

Was there any damage to your bearing inserts resembling the King Bearing Engine bearing failure guide ?

 

[0208DAC]

HI Tmoose,

The cavitation damage noticed on the journal bearing was the known "half moon" scratches an some other scratches. The remarkable and obvious cavitation pin hole damages was noticed on the crank pin of the engine.