WÄRTSILÄ PAAE051728, Instruction Manual

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11B.4 Piston skirt
11B.4.1 Visual inspection
The running surface of the skirt is coated with a graphite-phosphate
layer. Consequently cleaning with use of emery cloth or other abrasives
is not allowed.
••••
Excessive wear marks and/or scoring/seizure marks on the run-
ning surface may require replacement of the skirt.
11B.4.2 Support surfaces
Assessment of wear of the support surfaces to be made by measurement
of the distance between the inner and outer support surfaces, see
measurement record 3211V025GB.
11B.4.3 Crack detection test
Crack detection test of the entire piston skirt with use of liquid
penetrant must be made. Special attention must in this regard be given
to the upper part of the piston skirt and to the gudgeon pin bore with
its supports to the upper part and to the circumferential part of the
skirt, see Fig 11B-2.
Piston skirt
••••
As piston skirts are cast pieces a crack detection test may also give
indications for surface “defects” which are normal in castings.
Indications exceeding 5 mm in length should be examined more
in detail. If a crack is confirmed, the piston skirt must be replaced
with a new or reconditioned one.
Piston of type 1 Piston of type 2 Piston of type 3
Fig 11B-2
321180200112
32-200138 Piston Overhaul Appendix B
11B - 3