SL2019-685/KAMO Condition-based overhaulCermet-coated piston rings

This Service Letter defines the overhaul criteria for cermet-coated piston rings, and it provides guidance on how to estimate the remaining lifetime of a cermet-coated piston ring based on the remaining coating thickness. Cermet-coated piston rings were introduced as a scuffing preventive countermeasure.

The cermet-coated piston rings are now standard on most large-bore engines and are recommended for all engines operating on 0.5% S fuel or lower, as described in Service Letter SL2018-659/JAP. The overhaul criteria in this Service Letter apply to all engines fitted with cermet-coated piston rings