09.02.07
Reconditioning of cylinder liners
After extended use, cylinder liners of both 4-stroke, and 2-stroke engines will show signs of wear and tear. This wear is not evenly distributed. Most of the wear occurs between the reversal points of the upper and lower piston rings. Often we find scuffing marks where the upper piston ring changes direction. Also most cylinder liners, especially those of 4-stroke engines, will become slightly oval over time.
Another effect of this wear is increased lubricating oil consumption. When a cylinder liner comes out of the factory, it will have a slight cross-hatch pattern honed into it’s surface. This increased roughness helps the liner surface to retain the lubricating oil needed to provide an evenly distributed oil film between the piston ring reversal points. If the surface becomes too smooth due to wear and/or glazing of the surface, the piston rings will easier break the oil film, causing even more wear. Also any excess oil will no longer be retained by the liner surface, and burn off in stead, causing increased lubricating oil consumption.
If the total amount of wear is still within the rejection criteria as given by the manufacturer, the liners can be reconditioned. When we get them in our workshop, we will first clean and measure them. All measurements go into special protocol sheets. The next step is using a honing machine to make the cylinder bore round again, with a slightly bigger diameter, and restore the surface roughness needed to retain sufficient lube oil. Our honing machine can handle cylinder liners up to a diameter of 1 meter. The machine is made by the Swedish company Chris Marine. Here is a brief description of one of their typical honing machines: honing-machine.pdf
The pictures show a liner of a MAN B&W K80MC (this is a marine 2-stroke engine with a cylinder bore of 800mm). The first as we receive it in our workshop, the second with the liner in the honing pit with the honing machine inserted.
Finally the cylinder liner is measured again. Sometimes the landing surfaces between liner and cylinder cover, or liner and engine frame need to be skimmed on the lathe, to ensure the correct flatness of the sealing surfaces. Diameters, surface roughness, and other critical dimensions are recorded, and if everything is within the right tolerances, the liner is packed and shipped back on board again.
If necessary we can also transport our honing machine on board, and perform the honing in-situ, while the liner is still in the engine.
Anchor Repair | gCaptain.com said,
September 5, 2007 at 0:12 am
[...] Stranded on the Largest Island (he means China… yes we know) has an interesting “How-To” article on anchor repair. Along with detailed descriptions are some very interesting photos, check out the story HERE, then take a look at their article; Reconditioning of Cylinder Liners [...]
Ryan Skinner said,
October 2, 2007 at 15:58 pm
Found some of your observations on Chinese shipbuilding quite interesting. Keep up the good blogging work. It’s important that information comes across from individuals, and not always through trade journals.
Wolfgang CP Gensch said,
December 11, 2008 at 8:29 am
Interesting, but the ovality mentioned can’t be removed by honing, even claimed by the Maker Chris Marine. It is possible to remove ovality up to a certain degree and diameter, but the ovality still remains. You might should consider a wave cutting machine as this machine will restore the normal rough surface to a certain extend and this is mobile machine as well. Any how for big 2-stroke engine it is not advisable to carry out honing at all.
Hope to have shared some of my opinion and view about this matter and remain with best regards.
Stranded Mariner said,
December 11, 2008 at 10:40 am
Thanks for commenting on my post, and for your input.
You are right of course, when you say that the ovality can never be removed completely. But then every repair or reconditioning method is always a trade-off. I used to work for a big engine builder, and even they do not all agree on what is the best method for reconditioning.
Having said that, I will have a closer look into the wave cutting machine you mentioned.
Thanks and best regards!
fabrizio said,
December 18, 2008 at 22:19 pm
Hi,
very interesting blog
if u are interested or ure company is please have a look at http://www.sirmeccanica.com or contact me for any question concerning our engine reconditioning kit
fabrizio
f.gregorace@sirmeccanica.com