In assessing the wear of the segment, it should be noted that the wear of the bore is measured at the diameter while that of the segment is measured at the cut (S1) and therefore in developed length.
For a wear of 0.05 mm at the cylinder diameter, the cutting clearance will increase by 0.05 mm x n = 0.157 mm. Also, it is estimated that for the removal of the same volume of material on the cylinder and segment, the segment will be 40 times more worn than the cylinder. For 0.06 mm wear at the cylinder bore, there will be a 2.40 mm increase in play at the cut.
As the above precautions are taken in the assessment of wear, wear may be the result of poor segmentation choices or poor operating conditions.
Reminder: in order to ensure proper functioning of the segment and apart from the appropriate choice of dimensions and shapes, it is necessary to ensure that the segment retains its freedom of radial movement when mounted in the piston groove.
Some premature wear factors of the segment
- the specific pressure of the segment on the cylinder bore is too high
- too high radial thickness (deformation at mounting, too high tangential force....)
- radial thickness too low (too sensitive the segment to the additive pressure of the fluid at the back of the throat)
- inappropriate form of cross-section (M, L. B and IF or IW variants)
- too large external muzzle reducing reach height
- leakage at the cut (if) or by the play of the flat faces (roughness not suitable) allowing a strong pressure of fluid at the bottom of the throat
- the lubrication is insufficient: poor quality of the oil film on the top of the cylinder, near the explosion chamber, oil fluidity too great due to the high temperature, failure of the oil film due to a high specific pressure.
Mechanical Stress:
- not suitable cylinder bore material
- incorrect cylinder geometry
- roughness of the cylinder which does not conform to the requirements; slack at cutting (S1) which is too tight, causing the slats to be bent
- parallelism and squareness of the grooves which do not conform, causing the segment to catch in its lateral play
- insufficient throat depth or excessive throat-bottom radius causing the segment to catch
- lining of the back of the throat causing the segment to catch...
