Cylinder liner laquering

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Rum Baron
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Cylinder liner laquering

Postby Rum Baron » Fri Apr 04, 2014 3:36 pm

Good day! I was wondering if anyone has experienced an increase in cylinder liner lacquering over the past few years? I'm referring to the yellow gummy varnish that accumulates in liner walls and bakes to a hard shiny finish (you may call it something else?). Here in New Zealand I have inspected several engines that suffer from heavy lacquering; the worst cases seem to occur on medium speed engines operating around the 750rpm zone. High speed and low speed engines do not seem to suffer as much. We have one engine in particular that suffers extremely heavy lacquering which in a short period of time leads to heavy wear of liners and requires constant honing/replacement.It has been attributed to the use of ultra low sulfur diesel but in my experience there are always other factors such as light loading or incorrect running temps.

I just wanted to gauge how much of an issue this is around the world? Also what engines have you seen this on and what (if anything) have you done to reduce its effects?
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JollyJack
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Re: Cylinder liner laquering

Postby JollyJack » Fri Apr 04, 2014 4:48 pm

I've never seen this yellow gummy stuff before, but I doubt very much if it can be attributed to low sulphur fuel. Diesel nowadays has a sulphur content of 0.05% and all fuels must comply with ECA (Emissions Control Area) limits of 1%. This will be decreased to 0.1% by 2020. Normal wear will, of course, polish the liner to a high gloss and actually reduce lubricity. That's why it's better to hone the cylinder, so the scratches retain lub oil.
Last edited by JollyJack on Fri Apr 04, 2014 5:04 pm, edited 1 time in total.
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JK
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Re: Cylinder liner laquering

Postby JK » Fri Apr 04, 2014 4:50 pm

welcome to Diesel Duck. We're always happy to see new posters.
I can't comment on your questions, a bit too far away from the operational side these days, but one of the active Chiefs will probably see this and give you their thoughts.

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The Dieselduck
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Re: Cylinder liner laquering

Postby The Dieselduck » Fri Apr 04, 2014 7:18 pm

What size engine are you talking about here? 2000 kW or less? Bigger? What is your oil sampling telling you? I would suspect engine oil or fuel quality. I have seen some pretty horrendous things due to inappropriate oil type, but manifesting in the top end mostly.

Just found this... http://www.google.com/patents/US6070558 would suggest a fuel quality problem. Also, this is interesting http://www.diva-portal.org/smash/get/di ... TEXT01.pdf
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Rum Baron
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Re: Cylinder liner laquering

Postby Rum Baron » Fri Apr 04, 2014 11:53 pm

Thanks for the replies and the interesting links. Engines that seem to suffer the worst (in my experience) are medium speed, around the 4000 - 5000 kw power range and 750 rpm. The popular belief is that the change to Ultra Low Sulfur fuel (less than 10 ppm) in 2009 has led to lacquering becoming a big issue. There may be some truth in this but I have always believed it is more related to incorrect loading, overcooling and/or improper combustion (poor atomisation, timing or calibration of pumps).

I have worked on engines that have been switched to different lub oils to try and combat lacquering. Generally these anti-lacquer oils have a lower TBN to account for the lower sulfur content. In my experience this has not helped. There are also additives than can be added to the fuel which are supposed to prevent lacquer build-up and remove deposits, however I have no experience of whether they work or not.

In all my cases of engines with high lacquering, the oil consumption steadily increases as the honed surface gets 'filled in' by the lacquer. Often this leads to high crankcase pressure and an increase of soot production in the lub oil. The ships often pick this up as high viscosity during their tests. I even know of ships that only bunker in ports that supply high sulfur diesel (outside of NZ) in an effort to try and prevent lacquering!

I just wondered if this was a common issue around the world or just isolated to a few ships here?
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D Winsor
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Re: Cylinder liner laquering

Postby D Winsor » Tue Apr 08, 2014 6:12 pm

I'd be curious as to what the engine manufacturer say about the problem.
Has anyone checked to see if the piston rings more particularly the oil control rings being used are the correct rings for use with very low sulphur fuels? If the original oil control rings were designed deposit a set amount of oil on the cylinder wall to resist the effects of sulphur and other components of combustion gasses on the compression rings and liners. It is possible that too much oil is now being deposited on the cylinder walls leaving an excessive amount of unburned residue on the cylinder walls and possibly causing the laquering
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Rum Baron
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Re: Cylinder liner laquering

Postby Rum Baron » Thu Apr 17, 2014 10:33 pm

The problem is visible on quite a few different engines including some that are less than 5 years old with low running hours so I don't think it is due to any incorrect components. The Manufacturer of one of the engines (MAN) that suffers from lacquering has developed fuel injectors with a narrower spray pattern which is designed to keep un-burnt fuel off the liner walls. The difference is only 3 deg or so and hasn't yet been trialled but that may be where we are headed.
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Big Pete
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Re: Cylinder liner laquering

Postby Big Pete » Sat Apr 19, 2014 10:53 pm

Hi Rum Baron,
I have never come across a Yellow deposit like you are talking about, so at first I wasn't going to reply, but I suppose even Negative Feed Back tells you how rare this problem is.
Are you using any Bio Fuel down in Kiwi?
Have you been able to scrape off a large enough sample of this deposit to have it analysed by one of the L.O. Companies?
Good Luck.

BP
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