Al-Grooved Bearings
Inspection / Evaluate
A5.05. 02.03.09.01
M20/M25
en / 24.01.2011 IB023929 1/7
02
See also:
Spare parts list: B1.05.02.2.2601
Time requirement: 0 Pers./ 0,00 h
Personnel qualification: Chief engineer / skilled engine hand
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Operating medium: Heavy fuel and distillate fuel
Criteria for replacement of the grooved
bearings
The running surface of the bearings con-
sists of approx. 75 % electroplated overlay
(Fig. 1/a), approx. 25 % aluminium alloy
ridges (b) and max 5 % nickel dam (c).
First signs of running surface wear appear
of the electroplated running layer (a). The
overlay in the groove (a) is worn down by
a few 0,001 mm.
As wear increases, the difference between
the aluminium alloy ridges (b) and the
overlay (a) remains more or less the sa-
me, approx. 0,005 mm.
Under the magnifying glass, the overlay appears as a dark area, and the aluminium alloy ridge as
a light area.
The most important criteria for assessing the degree of wear of the grooved bearing are
•
the ratio of the aluminium alloy ridge width to the groove width, as well as
•
the size of worn surface
The grooved bearing can still function when the overlay in the grooves has partly worn away. In
actual practice it has been proven that the grooved bearing can continue to function without any ill
effects, even with partially empty grooves.
When assessing the conditions of the grooves, the running surface in the area subject to
the lowest load (condition of groove generally as new) should be used as a point of
comparsion.
The condition of the grooved bearings is assessed according to five different categories:
1. Reuse possible
2. Wear
3. Wear and levelling of the ridges (borderline case)
4. Overlay fatigue ruptures
5. Overlay fatigue ruptures and empty grooves (borderline case)
NOTE
For precise assessment of the degree of wear of the running surface, a
magnifying glass (minimum magnification 5x) is necessary.
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