Starting Up a repaird engine
Starting Up a repaird engine
(OP)
Hello everybody:
In a medium speed Diesel engine we have performed a machining job on a connecting rod journal, reducing the diameter in aprox. 5 mm. We are almost ready to start up this engine.
Would anyone in this forum give me any advice regarding with the care we have to take at that moment and during the normal operation? Is there any possibility that the nominal capacity of this engine could be reduced by this reparation?
Thanks
In a medium speed Diesel engine we have performed a machining job on a connecting rod journal, reducing the diameter in aprox. 5 mm. We are almost ready to start up this engine.
Would anyone in this forum give me any advice regarding with the care we have to take at that moment and during the normal operation? Is there any possibility that the nominal capacity of this engine could be reduced by this reparation?
Thanks





RE: Starting Up a repaird engine
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Jason
RE: Starting Up a repaird engine
Regards
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RE: Starting Up a repaird engine
patprimmer, yes it is, the connecting rod journal is 5 mm undersize, in an engine of 17.000 kW (17 Mega watts). Any comment that comes up about this subject, is really appreciated.
RE: Starting Up a repaird engine
Just wondering, could you get a 5 mm undesize con-rod and bearing shells from the manufacturer or did you have to build them?
respectfully
RE: Starting Up a repaird engine
17,000kW is a whole new ball game re my experience, so I have no idea of journal dia nor overlap, but I guess it is a lot more than a few inches.
What is the %age reduction in journal overlap. Have you changed the fillet radius. How was the fillet rad formed originally and on the repair, ie ground or rolled.
Regards
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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Starting Up a repaird engine
RE: Starting Up a repaird engine
Have done this a few times myself although mainly on slow speed engines. Just run it in nice and gently, the same as you would do after a normal major overhaul and in accordance with the OEM running-in schedule. Keep a close eye on the bearing temperature for a while, and, most importantly remember to highlight in your manuals that it has oversize bearings! Otherwise the guys who overhaul it many years in the future will get a surprise!
Given the output I guess it is a Wartsila 18V46? I'm curious - which journal required machining and why? Did you seize a piston or wipe a bearing?
RE: Starting Up a repaird engine
Thanks for your comments.
waross: The manufacturer has achieved this job and, under the circumstances, new especially elaborated con-rod big end bearing shells were provided.
patprimmer: The work we are talking about is the result of a guarantee claim, so, the manufacturer has performed the job at site but has kept in secrecy the technical data. Unfortunately, legally they are not obliged to release these data.
taylorg: the journal is the NÂș 8 of an 18V46 and the failure was a seized piston. How about the load this engine can deliver after the reparation?
RE: Starting Up a repaird engine
If the repair has been carried out under a guatantee claim and you find the engine will not give the same output then you have the right to reject the engine...
Your statement that "the manufacturer has performed the job at site but has kept in secrecy the technical data. Unfortunately, legally they are not obliged to release these data." concerns me as they regularly say this nonsense to their customers when things go wrong.
What exactly caused the failure?? - You have the right to know. What info are they keeping secret? If they are repairing it under guarantee it suggests they accepted liability. Are they checking your other engines for the same fault?
RE: Starting Up a repaird engine
Pre-lube the engine. Pressurize the oiling system with oil just before you start it.
RE: Starting Up a repaird engine
respectfully
RE: Starting Up a repaird engine
This is just to ensure that machining, clearances, installation and lubrication of the bearings are adequate.
By the way, an engine with 17,000 kw seems to be a low speed engine, what is the nominal rpm ?
Regarding power deration, you did mentioned a machining of 5 mm, can you tell us the nominal diameter of the conrod journal ?
Best Regards, WR
RE: Starting Up a repaird engine
We finally resorted to wiping high-moly grease all over the journal and running the engine at 400 RPM/no load for a while. 400 was a safe RPM, and the bearing got close to the shutdown point as we all held our breath. After ~30 min. the temp. started to go down a little. Another 30 min. and it was near normal. We then went up to 600 and had to hold our breaths again. Another 30 min. and the bearing was cooling down well. Same story as we increased load, but today the bearing is fine.
RE: Starting Up a repaird engine
To all once again, thanks for your comments.
wr180561: the nominal speed for this engine is 514 RPM @ 60Hz; the original connecting rod journal was 450 mm in diameter.
RE: Starting Up a repaird engine
RE: Starting Up a repaird engine
taylorg, we are still overhauling this engine and, according to the planning, the start up will be in the next few days. I will be in contact with the Forum and I will share our experience on this subject.
RE: Starting Up a repaird engine
The engine was started up.
Check outs before starting: stop tests (trip tests) of Oil Mist Detector, low lube oil pressure, local and remote emergency stop.
- Cold deflexion of crankshaft.
- The Oil Mist Detector was checked, specially serviced and adjusted to its lower value.
- Starting and stoping the pre lube oil pump for lube oil circulation through all bearings, crankshaft, etc. and to see where this lube oil comes from and goes to.
- Pre heat the engine with the High Temperature water system.
- With the lube oil pump on, pre heater pump on and fuel oil on, rotate the engine with the turning gear during 15 minutes.
- Rotate the engine with starting air blow for around 30 seconds.
Starting up.
- The engine is started up and run idle during 1 minute, then is stopped with the Oil Mist Detector.
Once the engine has stopped, we proceed to open the crank case covers and check the temperature of all the bearings: main bearings, big end and small end bearings. For this activity we use an infrared meter and a thermal camera.
We verify the free axial movement (along the connecting rod journal) of the big end connecting rod.
- Everything was OK. Start and run idle during 5 minutes, then stop with the low lube oil pressure trip setting.
At this moment, we achieve the same controls stated above.
Besides that check outs, we check for leaks of: fuel oil, lube oil, water and starting air.
- Everything is OK. Start and synchronize the unit taking 1.000 kW load and run during 3 minutes. Stop the unit with low lube oil pressure trip setting.
Here we check one more time the temperatures and the free movement of the con rods.
- Everything is OK. Start and synchronize, then run with 3.000 kW during 5 minutes. Stop with the local emergency shutdown.
Check out once again.
- Start and synchronize, then run during 30 minutes with a load of 5.000 kW, then with 6.800 kW, 10.200 kW, 11.900 kW, 13.600 kW, 15.300 kW and finally, with 17.000 kW.
After the 30 minutes with each level of load, the engine was stopped and left run idle for 5 minutes after which, the check outs of temperatures and movement were achieved.
- After the unit ran at the nominal capacity, Hot deflexions of crankshaft were taken.
- After 10 hours of operation at full load, the main bearings A8 and B8 were checked out and the big end bearings A8 and B8 were replaced for new ones.
The crank case covers A8 and B8 were painted in yellow and red in order to warn that a special condition on that side has ocurred. An inscription was properly painted on these covers indicating the modifications and showing the part numbers of the new elements.
RE: Starting Up a repaird engine
Sorry but I forgot to say that, at this moment two days after the latest check outs, the unit is operating at full load under normal conditions.
RE: Starting Up a repaird engine
44 minutes to full load, quick break-in. Detroit Diesel 2-stroke truck/boat engines are no more than about 5-10 minutes checking things, then it's full load and speed. Otherwise the rings never seat right.
Good for you. Thanks for sharing.
RE: Starting Up a repaird engine
This engine has around 360 hours of continuous operation, delivering 17.000 kW under normal conditions. So far, we can say that everything is all right!
RE: Starting Up a repaird engine
Are you still unable to share the cause of failure with us?
I know many plant owners using these engines and it would be of great benefit to share this information with them (as well as personal interest!), especially if they could be at risk of suffering the same problems.
I recall from another thread that you have been experimenting with orimulsion type fuels - did this contribute?
RE: Starting Up a repaird engine
Hi taylorg: This engine is running under the guarantee period.
The problem with this engine was originated by a seized connecting rod big end bearing on the crankshaft journal.
This action provokes a seized piston on the cylinder liner and so on.
That is all that we know and, for the present, the manufacturer has been not able to explain to us the details of the failure.
We are running our plant on Bunker C only and we do not expect to operate it with Orimulsion.