Cylinder liner reconditioning

Wärtsilä NSD Nederland B.V. Engine type W26 Chapter 2.5 Subject

Issue date Engine block/Cylinder liner June '00

Cylinder liner reconditioning

1 Material ; Material: GG 30 (Centrifugally cast)

2 Honing quality criteria; 2.1 Uniformity of the honing appearance The overall appearance of the cylinder wall should be clear, uniform and clean. 2.2 Formation of honing scores. Cut edges clean and sharp, with scores uniform. 2.3 Orientation of honing scores Uniform cutting during the upward and downward strokes. 2.4 Honing profile Sharply cut, edges not turned down and smeared over, see fig 3.

3 Hone machining:

Whenever new piston rings are mounted, the cylinder liner must be honed by means of “ plateau honing “

- If the machining is done in the engine block, honing debris / coolant must be prevented from falling into the sump. - Use a fair amount of clean gas oil as coolant, and to flush away the grains. - During honing the stones should not leave the liner surface for more than max. 2 - 3 cm length. - Clean hone stones regularly ( every 2 - 3 minutes ) by rubbing another hone stone over the running surface of the hone stone to prevent smearing of the honing profile. - The up- and down speed in combination with the rotation speed of the honing machine determines the honing groove cross angle. - The coarseness of the stone in combination with the contact pressure against the liner wall and the duration of hone machining determines the amount of material that is removed and the roughness of the hone groove created. - Use ceramic hones with a coarseness of 100 to roughen the surface. (in case of scoring marks, removal of ovulate etc. diamond stones can be used - for pre-machining ) .When roughening, try to remove as little material as possible.

Therefore a “divergent shaped” liner is allowed ( see no-go sizes ). In the upper region of the liner extra machining has to be carried out, as the liner is mainly worn in this region.

Therefore hone after each full stroke alternately, the top part of the liner bore (over a height of approx. 20 cm)

Wärtsilä NSD Nederland B.V. Engine type W26 Chapter 2.5 Subject

Issue date Engine block/Cylinder liner June '00

- Check the honing groove cross angle during honing and stop to hone as soon as the liner

surface is machined clean.

The overall appearance of the cylinder wall should be clear and uniform. - Use ceramic hones with a coarseness of 400 to finish the surface.

The sharp tops will be removed from the coarse grooves made before and the so called

“plateau honing ” will be created.

Note : The longer you machine the smoother the liner surface becomes. Check the roughness of the upper part of the liner ( on different places ) by means of a perthometer and check also the honing groove cross angle during honing regularly.

Stop the finishing as soon the honing profile is within specification ( see fig. 3 ).

- Make a cyl. liner measurement protocol and attach the measured roughness profile. Compare the liner measurements with no-go dimensions.

Note :

- After honing is completed, clean the bore carefully with e.g. gas oil by using a suitable brush, then dry the liner with e.g. a cloth.

Lubricate the liner bore with engine oil for corrosion prevention.