DUQ1-008E Cracks on Piston skirts RTA58 -68 - 76 - 84

It was ascertained that on some RTA "8" series engines in service piston skirts have been cracked at the flange clamped between a piston head and a piston rod, when they were overhauled. On this problem, the licensees in Japan have been examining and investigating earnestly in cooperation with each other as well as the licenser, Sulzer, and then we reached a conclusion that the piston skirts can be employed continuously without any problem though they get cracks.

Condition of cracks
The cracks were found on the piston skirt flange clamped between the piston head and the piston rod. (See sketch 1.) We have experienced the cracks of max. 240 on one of our
engines, with 17000 running hours.
These crack conditions are characterized by the following two points:
a) Cracks have occurred on the telescopic pipe side half.
b) Origins of the cracks are located on some points in circumferential direction, not just one point.
Some cracks exist respectively and some join to be observed as long cracks.