When preparing to install a new liner (slow speed 2 stroke crosshead engine) that is coated in a light layer of wax (dipped at the factory?) Is it critical to clean the inside of the liner? Would’t most of the stuff get scraped down into the underside space when installing the piston. Whatever didn’t get scraped down would get burned up/removed within a short run time.
This is my biggest concern with leaving the wax in the liner. The run in plus the first couple hundred hours seem to be the most critical with the engine. Will the wax burn off quickly, and will it do it without fouling the lower rings or glazing up the liner seems to be the question.
What alleviates my concern is the overall condition of the engine. Many pistons are 5k hours overdue for service. The last one completed the liner was at its max wear limit. She just keeps chugging along. Firing pressures look ok. I feel like a little wax won’t hurt one way or the other.
I’m not an engineer but is there a service manual for this engine that you could reference? Port engineer? I’ve got some phone numbers to some MAN Primeserve guys in Houston who may know (if it’s an MAN engine).
No one wants to be holding the bag for a botched cylinder liner if procedures weren’t followed.
Port Engineer says to clean it… It’s easy for him to say. He’s not the guy with the brillo pad and a diesel bucket.
Maintenance manual says to “clean the new cylinder liner, removing the protecting layer of grease and mount the new seal rings” which seems to be discussing the JW side.
It also says: “The joint surfaces, cylinder liner/cylinder frame must be completely clean”
To be safe and assuage all involved it would be best to clean the inside of the liner. I’m just wondering if anyone has put one in without removing the wax. The engine (MAN) is a well built resilient piece of machinery. I’m 90% sure it would be fine to put in the liner with the inside still coated in wax. However, there is always the tendency from the office to err on the side of caution with this stuff, even if it means more work for the crew.
If you have to use a brillo pad then it definitely isn’t a standard Caterpillar, EMD or DD liner. I cleaned a few a couple of weeks ago & it was the same as usual, a recycled cleaning spray bottle filled with diesel & 1 clean towel per liner. The wax comes off easily from liners, the diesel does most of the work. It seems cleaning heads are more time consuming but still easy depending on how well it gets coated & sets with diesel.
@W.T.Sherman stated the engine is a MAN (large) slow speed 2 stroke crosshead engine.
I agree with @shipengr in that leaving the preservative on negates the liners honing. It will also promote fouling of the piston rings.
If not removed there is a good chance the preservative would become liquid or semi-liquid as the engine is warmed up (jacket water) prior to starting. I wouldn’t think of putting it in without cleaning first.
Edit: Part of the cleaning process is blowing out the lubricator port drillings to ensure they are clear.
This might sound like a snide comment, but if the Manual, Port Engineer, and experienced engineers on this forum recommend cleaning the liner, I’m not sure where your 90% confidence of success in not doing so would come from.
The point of the wax is to preserve the honing during storage. The cross-hatching allows the LO to be retained on the liner surface and maintain proper lubrication with the sliding piston skirt. If the wax remains, the rings might scrape some off but it won’t get it out of the hatching.
Once that becomes a glazed surface you seriously risk uneven lubrication and hot spots. That translates eventually to piston skirt scuffing.
Run that condition long enough and you might see a con-rod come to see you. If that is worth the risk of skipping two hours with a Brillo pad, your decision.
Outside of the liner has been cleaned, including the oring grooves/lubricator holes. I don’t want wax floating around in the JW system.
I’m looking for another opinion from someone familiar with MAN engines. The port engineer isn’t a great resource in that regard…
My confidence comes from seeing the engine that gets run hard with no issues. It’s a slowspeed burning HFO, none of the liners are in great condition. Is a little wax going to ruin the liner? Have a little optimism bias.
Once the engine is heated to 70 C how much will remain? Once combustion starts and the inside of the liner heats up how much will remain then? Will lubrication issues still exist? Can I just crank up the alpha lubricators another notch and let it run?
Most engine parts are coated in cosmoline/wax. It is corrosion protection first and foremost. Isn’t honing done to true up a cylinder liner. Bring it more into round. The ridges/valleys that retain oil are a secondary benefit of honing a liner. The ridges help to wear in new rings and the valleys remain to hold oil (hopefully).
It’s a 2 stroke slow speed… I wouldn’t do this on a trunk type where it would scrape down to the LO sump.
Its also a large time investment. Especially on something large and heavy that is normally bolted down at sea. I don’t like the idea of someone going inside the liner. Looking to avoid that if I can.
What’s the stroke of those engines, I want to guess 2 or 3 meters or so? Do you put a crew member inside the liner to clean with diesel? Isn’t the installation of a new liner usually done by shoreside crew?
Seems like a shoreside crew would have a tool, like a chimney brush to clean the inside.
The stroke – bore ratio of low speed engines varies between 2.5:1 to 4.2:1. Yes, easily 2 or 3 meters as typical bores are 70, 80 or 90 cm. If new the liners are usually cleaned as much as possible before they are inserted. Someone gets inside and stands on a ladder. I have done it both ways, crew only and with shoreside assistance. Really depends on haw much time you have and how well prepared you are.
If your estimate is in the ballpark, the risk / benefit analysis is easy:
0.1 x (cost of pulling piston for ring groove cleaning and liner surface honing) - (cost of cleaning liner prior to installation)
If that works out to a positive number, I’d reach for whatever wax stripping agent you’re comfortable with. In fact that’s what I’d do in any case, because who wants to explain to the owner that he’s looking at downtime because you wanted to save him a few thousand bucks?
On a side note, stress honing and surface honing are done differently and for different reasons. A good gas seal is dependent on the cross hatch pattern, and high speed diesels do fail in a multitude of modes because of this, sometimes spectacularly. Medium speeds seem more resilient, presumably due to the piston circumference to displacement ratio, but I can’t back that up with a decent sample size, and I must assume that blowby erosion is no less destructive in large engines. I have no relevant experience with slow speeds, but again I must assume that principles do apply.
Fair enough, I’ve just always been well served by instilling in my A/E’s a desire to do things the right way every time. It improves reliability in the long run and it often takes less time to do than it does to come up with excuses for not doing it. Added benefit being CYA if there is a subsequent failure.
Maybe I’ve just been lucky having shoreside management who I never had to justify taking the time to do things by the book.
What is the “right way”? Is it always “by the book”? But what about when the book is wrong, or unnecessarily conservative? Procedure and design changes happen all the time to “the book”.
Do you require your A/E’s to use a torque wrench on every single bolt you ever tighten? Would this improve quality and reliability (perhaps it would in some cases, but it may just waste time in other cases).
The shipping industry is, overall, greatly behind the reliability engineering of shore-side industry and aviation. For example, nuclear power plants figure out long ago that merely replacing components (such as bearings) based on manufacturer’s operation hours recommendations lead to lower overall reliability and increased chance of unplanned shutdowns.
Very few things are absolute in the engineering world, and many standards are created via poor statistical analysis and obsessive conservatism (“we’ve always done it this way”). It is tough to prove one way or another whether wax protectant left in cylinder wall will have adverse long term effects. But maybe it provides great friction protection during initial startup on the new liner until the oil gets splashed around to do its job? Without expensive structured tests, one will never know for sure.
With regards to the manual. Look at #26 in the cutaway. That’s an oring that goes under the cylinder cover nut. There weren’t any there last time I pulled a cover, and when re-installing none went back on. I asked about them, and was told that they weren’t necessary.
It does seem crazy that MAN would put them there if “they weren’t necessary” But they seem to be of minor importance.
So when the manual says to clean the liner, I wonder if I really need to clean the inside, or just the specifically mentioned spots. (Which happen to all be on the outside of the liner). The time spent dewaxing the inside of the liner could’ve been better spent cleaning up/prepping the spare piston/cylinder cover.
It seems the inside of the liner needs to be cleaned, even if its only affect is to make el jefe happy.