Fault Phenomenon: Kobelco crawler crane when the upper structure rotates, the lower travel action is simultaneously slow, and oil leakage is found at the center rotary joint.

Troubleshooting Process:
– Checked rotary joint seals: O-rings aged and cracked.
– Checked oil passages: passages cross-communicating.
– Disassembled and replaced all seals.

Root Cause: The center rotary joint seals aged and failed, causing cross-communication or external leakage between high and low-pressure oil circuits.

Required Parts: Center rotary joint seal repair kit.