Fault Phenomenon: Zoomlion ZR360 rotary drilling rig rotary head speed cannot be adjusted, fixed at high or low speed.

Troubleshooting Process:
– Checked actuator: swashplate actuating piston stuck.
– Checked control oil: insufficient pilot pressure.
– Checked spring: return spring broken.
– Checked oil quality: severely contaminated fluid.

Root Cause: The swashplate actuator of the rotary head variable piston pump is stuck due to oil contamination, unable to adjust displacement based on load.

Required Parts: Hydraulic pump overhaul kit or replace pump.