WÄRTSILÄ RT-flex50-D, Руководство по обслуживанию

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Maintenance
3425−1/A1
RT-flex50-D
Wärtsilä Switzerland Ltd
2/ 4
3. Evaluation of piston ring running surface
3.1 Chrome-Ceramic (CC) coated piston ring
The chrome-ceramic coating is a lifetime coating. However, the actual wear de-
pends on piston running conditions. Wear of CC-coating can be monitored by
means of chrome thickness measurement tool 94356 (see Recommended Spe-
cial Tools 9403−5).
When during a piston underside inspection a piston ring with a partially worn CC-
coating is found, the ring needs not necessarily be changed immediately. If the re-
maining chrome layer is intact, it is still fit for continued service.
PARTIALLY WORN CC-COATING, BUT
SUITABLE FOR CONTINUED SERVICE
B
If the chrome layer is damaged, i.e. pieces of coating broken out or patches of coat-
ing peeling off, the ring should be replaced at the earliest opportunity.
3.2 Running-in coated (RC) piston ring
3.2.1 Ring gap
The current piston ring wear can roughly be determined with the piston in situ by
means of the ring gap.
The piston must be moved until the piston rings appear at the level of the scavenge
ports. In this position measure and record the ring gap (S
1
).
3.2.2 Determining wear of piston ring
In order to determine the piston ring wear, some time or other (approx. 3000 run-
ning hours after the last overhaul) ring gaps (S
2
) are measured and recorded.
The piston ring wear can be determined with the formula
Later regular optical checking of the piston rings through the scavenge ports pro-
vides a reliable judgement of the piston ring condition. The ring gap measured dur-
ing such an inspection also permits a determination of the next piston overhaul.
Should the gap of a piston ring be in an inconvenient position, do not try turning it by
using any sort of tool. In such cases it is recommended to measure the ring gap at a
later opportunity.
2010
Piston: Checking Piston Ring Wear
S
2
− S
1
2 x 3.14
CHECK