Fault Phenomenon: SANY SR360 rotary drilling rig main winch lifting speed is significantly reduced when lifting heavy loads.

Troubleshooting Process:
– Checked main pump: main pump output flow insufficient.
– Checked motor: winch motor internal leakage.
– Checked brake: brake not fully releasing.
– Checked wire rope: excessive layers of wire rope on drum.

Root Cause: The main hydraulic pump variable mechanism is stuck in the small displacement position, unable to provide sufficient flow.

Required Parts: Clean or replace main pump regulator assembly.