WÄRTSILÄ 41508 Instruction Manual page 117

Appendix B
11B.2
11B.3
Piston Overhaul
Pistons
The piston assembly must be dismantled for inspection of mating
surfaces between piston skirt and piston crown and for inspection and
cleaning of cooling oil spaces.
Piston crown
11B.3.1 Visual inspection
The combustion space must be checked for corrosion and/or burning
marks.
If marks deeper than 2 mm are found the piston crown should be
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• •
replaced.
Deposits in the cooling oil space thicker than 0.5 mm is an indication
of contaminated lubricating oil. Such extensive deposit layers can cause
overheating of the piston crown.
11B.3.2 Crack detection test
A crack detection test by use of liquid penetrant or, preferably, mag-
netic particle detection method should be performed, comprising all
surfaces.
No cracks are allowed.
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• •
11B.3.3 Measurements
Piston ring grooves to be measured regarding wear in accordance with
normal practice.
Measurements of the distance between the inner and outer support
surfaces must be made, see piston type specific instructions below.
Please note that a special measuring tool has been designed for this
measurement.
11B.3.4 Reconditioning
Please contact Wärtsilä for reconditioning of piston crowns.
32-200138