De pain de pain.. Generator retires. 4

[itsmoked]

Remember the generator/regulator issue you guys assisted me with a couple of weeks ago? Well, once that generator was shipshape they just parked it on a siding and continued using the Head End Power (H.E.P.) from a 250kW generator mounted transversely in the rear of the F unit (a 'covered wagon' style engine). Well, they did until today anyway. LOL.

With the train waiting for passengers to cue-up for loading the generator was heard to go to full throttle for about 1 second then come off all throttle for about 1 second, repeating this four times before automatically shutting down. Before staff could take five steps in its direction, oil and antifreeze began pouring out of the H.E.P. end of the F unit.

Inspection revealed:

[highlight #FCAF3E]The white stuff is fire department anti-hazmat absorbent.[/highlight]

[highlight #FCAF3E]How about that lump![/highlight]

[highlight #FCAF3E]I'm pretty amazed a quarter of the piston was actually able to claw its way out of the block.[/highlight]

How about some speculation on what caused this. I believe the load was about 90kW at failure.

Why exactly would a piston get so pissed off as to leave the party sideways?

I didn't have time to gander long so I failed to get the engine type. I'm thinking it's a Marathon tail-end? Anyone know what make engine that is?

Luckily the power car we all fixed was ready. They detoured to the yard 5 minutes away and picked it up and were back in business about 15 minutes later.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[3DDave]

Professional opinion: That's busted.

Maybe the wrist pin broke on one side so the piston went crooked and bound for a while before seeking freedom from being beaten by the connecting rod. It may have tried to burn uncontrolled oil through an fresh alternative path, hence the extra throttle. Extra-path oil burning is one of the uglier failure modes for diesels as cutting off the fuel supply won't always stop the engine.

I wouldn't suggest repeating this experiment.

 

[itsmoked]

Indeed.. I'm guessing the automatic shutdown was probably "loss of oil pressure" since it was getting puked out on the ground.

"People" said they saw "fire coming out" on the side away from the staff. I could see no signs of any kind of fire in the compartment so I'm thinking maybe flames came out the exhaust. In the daylight I'll have to see where the actual exhaust outlet is.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

Sticky governor linkage.
The load reduces but the linkage sticks and does not reduce the fuel. Hence the engine speeds up.
The linkage releases and the governor regains control.
I saw this on an engine with an electronic governor.
The fuel was controlled by an electric metering valve.
The electronic governor increased the fuel flow by increasing the voltage/current to the valve.
An increased load would call for more fuel but the valve would not respond.
As the increased load pulled the speed of the set down the governor would increase the signal to the control valve.
As the signal was increased, the valve would break loose and free of sticktion would go to the commended position.
This would result in overspeed. The valve would break free of the sticktion and drop to a low fuel position.
Repeat.
If this has a mechanical or hydraulic governor look for signs of binding in the linkage.
Let us know what it looks like come daylight.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

Bill, you're saying the sticky linkage would lead to a piston being chucked out the side of the block? This generator is not paralleled.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LionelHutz]

Engine over speed led to the piston breaking apart or the small end of the rod breaking and then smashing the piston apart. At any rate, the piston ended up broken and one of the chunks broken off fell between the crank and block and got smashed through the side of the block.

 

[waross]

What Lionel said.
The sticky linkage led to overspeed which led to destruction.
Another possible cause is loss of oil pressure.
That would lead to stiction in the governor linkage and failure of the con rod(s).
Take a look at an intact con rod bearing. Lack of oil pressure will be obvious.
The damage may have been caused by overspeed or by lack of lubrication.
The speed surging may have been cause or effect.
I'm betting that the low oil shutoff was inactive.
Another possibility is a dropped valve.
That happened to me driving a dump truck in my "Yondering" days.
The piston looked like that and without the piston, the end of the con rod made a similar hole in the side of the block.
In a diesel, oil may splash into the intake manifold and caused the overspeed.
That reminds me of the word back from the dealer when we sent in an air cooled 15 kW set after a couple of "Lack of oil events"..
"What is your tax situation?
If you can write off the repairs we can fix this for $4400.
If taxes are not an issue we can sell you a new unit for $4000."
Cost of repairs will probably be more than the cost of a new set.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[catserveng]

Overspeed is a good possibility, however there could also be other factors as well. Until you disassemble and take a good look hard to pinpoint.

I had a failure a couple of months ago with a similarly described speed cycle that turned out to be a failed injector nozzle,the speed cycle appeared to be the result of the piston sticking then freeing until finally pulling apart. However to conclude this we had to find enough pieces of the piston that did not have subsequent damage from getting smashed to figure that out.

An overspeed will have indications in other areas of the engine, look for indication of valve float in other cylinders, with possible valve head to piston crown contact.

The "flames" could have been a flash fire from atomized fuel, lube oil and antifreeze, have seen this a few times in containerized units, a report of fire but hard to find evidence of it make that a possibility.

Failure analysis can be a chore to the actual root cause, but I also find it fun, hope you find the guide I sent useful.

MikeL

 

[waross]

I share your pain.
We had a three hour power outage today.
No problem.
I fired up the old diesel generator and it was business as usual for an hour or so.
Then the hub of the pulley on the water pump and cooling fan broke and the set shut down on high temp. (I hope)
Problem.

The good news is that when this broke 6 years ago, we did a red-neck fix and ordered a new pulley.
I just located the replacement pulley in the bottom of a storage closet.
I should be able to install the new part tomorrow.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[LionelHutz]

Bill - at least your fan didn't go through the radiator.

 

[waross]

Yes Lionel Small mercies.
My problems are nowhere as serious as Keith's but I do envy him the California weather.
I will be doing my best to get this fixed today at minus 7 C. Tomorrows forecast is minus 15.
The set gets a few hours a day use at this time of year lighting up the skating rink in the evenings.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

Wasn't an overspeed. All personnel stated it never got faster than it had been running. The excursions were all "down and back". I'm now told there were about 10 and they were pretty quick. No one heard it actually 'break' since they were all standing a bit farther up the same locomotive who's prime mover was running.

I went by last night to see if I could get a picture up inside the engine through the new 'inspection port' to see if maybe the valve head(s) are gone. That would lend some 'points' to Bills dropped valve scenario. However my contact there had just hiked back 200 yards from that locomotive to the afore discussed power car on the other end, where I'm contemplating a solar charger to keep the batteries topped up over the 11 month idle period. I could see on my buddy's face the four back-to-back 112 hour work weeks were really flagging him and opted for doing it another day.

Mike! Thanks for that fascinating forensic manual. MOST interesting. I saw that email and was scratching my head as to how the gawds had sent me such a timely manual until I figured out it was you. LOL

A lot of people have speculated loss of oil pressure, clogged oil filters, etc. but I'm having a problem with that. It appears the unit shut down just about precisely when most of the oil had been ejected out the hole. Hence, the pressure loss didn't occur until after the failure. Hmmm, another point for the dropped valve scenario.

I cannot see this paperclip, glue, and string operation ever repairing this beast. The other, almost identical F unit on the other end of the train, has a big worn area where the exact same style HEP generator used to be installed. Perhaps these particular Cummins check-out this way frequently? I would imagine it would be far cheaper to just install a used 150kW WhisperGen in the same spot.

And Bill we've been shivering here with sub 40F weather for a week or so and now are in a cold storm dumping snow on the nearby hills. But you've still got me with your 19F..

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

It's relative. Working outside today was not that unpleasant. Low humidity and no wind.
I have been pretty miserable in warmer weather. Grin
I like that solar charger.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

Get your Generator back together Bill?

I got back to the local shortline and stuck my camera in the hole in the block to 'see' up into the cylinder. Forgive the quality the train when in motion just after I got down to take the picture.

I'm thinking it maybe wasn't a dropped valve unless that's not what I'm seeing.
The 350HP Cummins was delivering ~ 120HP and had been steadily (+/- 25HP) for the last 3 hours before checking out.



Keith Cress
kcress -

http://www.flaminsystems.com

 

[3DDave]

For a moment I wondered if the injector caused a hydraulic lock. Once the piston was gone, the fuel would have run out, eliminating some of the evidence. That would explain bogging down, and with too much fuel not all would burn, so it would take a bit to refill if it managed to puke any out the exhaust valve. Alternatively a leak of coolant into the cylinder can cause loss of lubrication (I used Google to search for hydrolock of diesels and found that.) Another suggests too much water in the fuel can build up.

 

[waross]

Thanks for the pics.
All those impact areas and the bends in the con rod explain the throttle burps.
Every time the con rod hit something solid the engine would slow enough for the governor to open the throttle.
Mine is going slow. Not difficult just slow.
It seems that I have some damage to the flange on the water pump.
I couldn't repair it in situ.
I now have a replacement pump with all the spacers and a new fan.
We had a few days of colder weather and it's mostly bare finger work.
Today is a hockey tournament.
There's a good chance it will be fixed tomorrow.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[MikeHalloran]

I have seen a $10,000 con rod bent a little worse than that, but it was from a 'crash stop' in a big yacht with a suboptimal exhaust riser.
... i.e., hydraulic lock, which could be caused in any Diesel by a coolant leak into the cylinder, or mechanical lock, as from a valve head separating.
I think I can see two valve heads in their proper location in that last photo.

It's interesting that the piston pin and the small end of the rod appear to have never left the vicinity of the cylinder, suggesting that for whatever reason, maybe just old age, the piston fractured, and was then beaten into a lump, which then eventually found a weak spot in the crankcase, leading to a shutdown for loss of oil.

I have had a piston fracture at the oil ring groove, but the lump in the photo with the rings embedded, suggests that maybe yours fractured at the pin boss.


I don't see proof that the water jacket was breached, and I have seen bailing wire type repairs that worked against all odds, so I can't say it's impossible to return the engine to service; it just depends on how motivated and how stubborn your guys are.



Mike Halloran
Pembroke Pines, FL, USA

 

[catserveng]

Based on your pictures and info this looks like the piston seized in the bore, finally stuck hard enough for the rod to pull the piston apart, the free rod small end and piston pin beat the lower part of the piston and the liner into pieces and when a big enough chunk of the piston or liner got free and came down between the crank and the side of the block it got kicked out.

Have seen a lot of these failures in diesel engines over the years, the causes have been widely varied, usually cooling system problems accounted for most on engines with higher hours, even at low load factors, signs of that was usually corroded and pitted water sides of the liners. Actual "single hole" failures were usually the result of fuel injection nozzles or unit injector problems. When CAT first came out with high pressure unit injectors, we had a fairly large number of failures due to water in the fuel, would cause the injector tip to fail, wash down the cylinder and stick the piston. Had to re-educate may customers who were used to the older type engines that were very fuel tolerant into taking better care of their fuel. About the only time I have seen piston seizure due to lack of lube is on engines that use piston lube oil cooling, I don't think your Cummins engine has that. Generally lack of lube affects the rod bearings, rear main bearing and cam lobes/followers (more heavily loaded surfaces in the engine) before running long enough to seize a piston. Lube oil quality problems causing excessive deposits can lead to seizure, you may find one hole ventilated the block but the other holes weren't far behind in those cases.

A lot of possible causes, if you really want to understand the failure you need to pull the head and pan and look at the adjacent cylinders. This will help determine if a systemic problem, such as lack of lube or coolant was the culprit, of if the event was confined to that hole. Try to gather as many of the pieces as you can, preferably before they all rust up, try to find pieces of the piston skirt with minimal impact damage to get an idea if the surface, same with the liner pieces, and make sure you look on both the cylinder wall and water side of the liner, could help you determine if the problem was related to cooling system issues or problems internal to the cylinder. Cummins published Bulletin (985579) titled "Failure Analysis Pistons and Liners", here is a link describing,

https://books.google.com/books/about/Failure_Analysis_Pistons_and_Liners.html?id=cfHjmwEACAAJ

Caterpillar also published a failure guide for pistons, liners and rings, form number SEBV0553

Here is a nice link from IPD Parts (Makers of aftermarket parts for many heavy duty engines),

http://www.enginebuildermag.com/2002/04/heavy-duty-technology-piston-failure-analysis/

and this,

http://www.hdxperts.dk/index.php/fa...older=&file=Piston Seizure Qick Ref Guide.pdf

Here is a link to a page showing a metal stitch cold weld procedure on a Jenbacher gas engine to area that looks similar to the type damage your engine has.

http://mechanicalcomponentsrepaircompany.blogspot.com/

A lot depends on how much damage was done to the block internally and to the lower liner bore, likely a good used block can be had for less than the cost of an extensive repair. However a repair can be done if you have the time and money, in just about all cases in repairs I have done we have used metal stitching procedures, usually on larger engines and frequently done by a company called InPlace Machining,

http://www.inplace.com/services/metalstitch-metalock/

The unit is in California, right? Maybe you can see if it qualifies for one of the emissions retrofit programs like Carl Moyer instead of dumping money into it?

Hope that helps, MikeL.

 

[waross]

Based on your pictures and info this looks like the piston seized in the bore, finally stuck hard enough for the rod to pull the piston apart, the free rod small end and piston pin beat the lower part of the piston and the liner into pieces and when a big enough chunk of the piston or liner got free and came down between the crank and the side of the block it got kicked out.

I agree 100& Mike. I was about to compose a similar post but you said it better than I could.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

H[/b]]It's interesting that the piston pin and the small end of the rod appear to have never left the vicinity of the cylinder

I was pretty surprised to see that also.

H[/b]]I don't see proof that the water jacket was breached

Would this change your opinion? LOL

L[/b]]when a big enough chunk of the piston or liner got free and came down between the crank and the side of the block it got kicked out

The rod end in the picture above did exactly that. I believe I can see aluminum imbedded in the con rod in the 8MB image.

Thanks Mike for all the links too!

This engine is on a siding in a central California coast town. There really are no "guys". They'd like to fix it but are very low-end-operation people without a lot of $$. It's a shame because the tail end is a monster. It's considerably larger than the 1/2MW unit even though it's only a 350kW generator but it does 432kVA. (seems like a big difference to me).

A stitch or even some sort of red-neck patch could probably seal the crankcase but the damage to the cylinder is probably the hardest hurtle to overcome.

I can see pulling this unit out and replacing it with anything over 200kW (used) that would fit. The hard economic issue is that this is a seasonal-use generator that's used for approximately 200hrs in December - period, so not a lot of daily economic imperative to quickly put it back together as is.

Great point about the CA emissions angle. Love it. It looks very plausible too looking at the program.



Keith Cress
kcress -

http://www.flaminsystems.com