Piston failure Root Cause 1

[manffrogg]

I'm looking for any refernces available concerning Piston failures and seizures on diesel engines piston. Many failures are relativly simple to diagnose but a seizure without any coorelateng cause evidence is difficult. I'm looking for any help I can get.

 

[rob768]

Look at honing pattern. Too smooth may cause problems, since it is meant to keep the oil in place. The wrong type of piston springs, worn springs, worn cilinder wall, wrong type of oil, clearance, combustion...

 

[CoryPad]

"Fatigue on engine pistons – A compendium of case studies", Engineering Failure Analysis Volume 13, Issue 3, Pages 301-526 (April 2006)

available at:

http://www.sciencedirect.com/scienc...serid=10&md5=7bae3457af3a8ce0dd92b87a991da0c9

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[ivymike]

yeah but... a piston siezure is not a fatigue failure

 

[CoryPad]

OK, so my reference doesn't cover everything. It certainly is a good, recent discussion regarding "Piston failures".

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[manffrogg]

I appreciate the responses to my inquiry. This particular failure was to a piston that ran more than 13k hours.
It seized in the top of the liner with indications of swelling in the crown.
There are areas in the rig belt that were not damaged.
There were no real signs of oil starvation as far as I can tell.
I found no problems after testing the injector, the Pop pressure was OK and the spray pattern was alright also I believe that Timing was within spec.
none of the other cylinders were affected with the exception of the oppostite bank matching cylinder of the other bank, which was taken out by the rod when it eventually failed. This is a 16 cyl. 2800 hp engine.

I feel this was a combustion related failure but i cant find any coorelating issues. we have had similar failures on this type of engine.

I'm kinda grasping right now but I know there is an explaination for this failure

I ordered some diagnostic manuals from Caterpillar but havent got these yet.

thanks for the help.

 

[TheBlacksmith]

How about cooling. Was the water passages to/from the head unrestricted? (Assuming individual cylinder heads) Does the rengine have piston cooling oil spray? If so, was in functioning properly?

 

[ivymike]

It certainly is a good, recent discussion regarding "Piston failures".

Have you read it? As someone with quite a bit of piston experience, I have to say that it doesn't sound all that interesting or informative to me (I wouldn't pay to read it).

It seized in the top of the liner with indications of swelling in the crown. There are areas in the ring belt that were not damaged. There were no real signs of oil starvation as far as I can tell. I found no problems after testing the injector, the Pop pressure was OK and the spray pattern was alright also I believe that Timing was within spec

I would say that 30% or more of piston siezures on HD diesels are caused by fuel system problems, and another 20% by improper oil jet aiming or oil jet damage after service. Be very thorough in ruling out timing/pattern/etc problems.

Are you quite sure that piston siezure was the precipitating failure? Is the fracture surface of the rod intact? Does it show relatively slow crack propagation, or rapid propagation?

Was that piston an all-steel design with a closed cooling gallery with spring-plates to close the bottom of the gallery? Were the spring-plates still installed after the failure?

 

[manffrogg]

I'm am pretty sure that the piston seizure lead to the failure. The rod beat the bottom of the piston for quite some time before it let go, then became obliterated and took out the matching rod, this is a Fork and blade assembly.

the piston skirt was pulled right off the piston and the piston was stuck in the top of the liner. it was easy to remove once the head was off. the other piston was really stuck and hard to remove but showed little sign of seizure other than the spots were debris had lodged that caused it to seize. This piston is supplied with cooling oil via the connecting rod and a passage that directs oil to the underside of the piston from the top of the small end. the varnish on the underside of the piston looks similar to unaffected pistons and no bluing in whats left of the the small end of the rod or the pin.

the piston looks like a all aluminum piston with the possibility of a steel ring belt, but I cant tell. I will know when the lab cuts the piston which i think they plan on doing.

I definetly havent ruled out combustion problems in this case, but i need more comparitive data to push me in any direction. I'm down to cooling or combustion at this point.

check out this source:

http://www.msi-motor-service.com/download/kolbenschaeden/e/kos_2005_50003973-02_en_web.pdf

this is the best i have found yet and its a free download Free is always good

 

[CoryPad]

ivymike,

Yes, I read it two months ago. I don't understand your distaste for this reference - are you basing it on the "sound" of its abstract? I think it is interesting and informative, and while $30 may seem like a lot for a technical article, it does seem to be similar in price to articles from other publishers. After further information from manffrogg it may not be directly applicable, but it seemed a likely match with the generic request from the initial post.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[manffrogg]

I'm interested regardless of the applicability to my case. But $30.00 for 12 pages sight unseen. I checked the site, an excerpt and your endorsement might of pushed me over the edged and caused me to purchase, even though I know it dosent apply, it may be useful in other failures. But i have blown twice that amount on a book which if after i got it and reviewed it, I would have not bought it. My funds are limited everybody else makes money off of my work I make little. But i may purchase it any way. Its hard to find good reference on piston failure diagnosis and engine diagnosis. although i'm getting better at it all the time.

 

[CoryPad]

manffrogg,

Are you near a university library? They likely will have a subscription to this journal and you can obtain it for free. That is what I do.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[ivymike]

I don't understand your distaste for this reference - are you basing it on the "sound" of its abstract?

Yep, that and my imagination about what "root cause analysis" via FEA of a smattering of miscellaneous piston failures from disparate production applications might tell someone. Unless there are a bunch of manufacturers running around with _really_ bad piston designs, I have trouble imagining that FEA will tell one anything at all about a particular failure - the pre-production FEA(s) no doubt said "that piston is >1.8x as strong as it needs to be" and the structural validation testing said "yup, that piston is strong enough" (or else the design should never have gone out the door).
Heck, the abstract made it sound as though low-cycle fatigue wasn't even considered in any of the cases.

 

[MikeHalloran]

What did this engine do for a living before it died?



Mike Halloran
Pembroke Pines, FL, USA

 

[CoryPad]

ivymike,

I understand your disdain for root cause analysis and random FEA without context, but this article doesn't perpetuate those problems. It has good examples of actual failed pistons, makes some appropriate conclusions, and is a worthy addition to the literature.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[manffrogg]

This engine is one of two that provide propulsion for a ship

 

[MikeHalloran]

Is the engine exhaust 'wet', i.e. is water injected somewhere?



Mike Halloran
Pembroke Pines, FL, USA

 

[manffrogg]

no its turbocharged with a wet exhaust at about ten ft from the turbo

 

[EddyC]

Does this particular cylinder have a longer path from the coolant pump than the others? Are the coolant passages around this particular cylinder a different configuration than the other cylinders?

 

[MikeHalloran]

Did you find rust or salt in the cylinder or the exhaust?

[ Turbos don't stop water flowing upstream in exhaust passages. ]



Mike Halloran
Pembroke Pines, FL, USA