Fault Phenomenon: UpRight SL20 scissor lift aerial work platform in an emergency, the manual emergency descent valve cannot be opened, the platform cannot descend.

Troubleshooting Process:
– Checked valve stem: stem corroded and seized.
– Checked tool: tool mismatch.
– Checked spool: spool seized.
– Checked operation: incorrect operation direction.

Root Cause: The emergency descent valve was not maintained for a long time, causing the valve stem to corrode and seize.

Required Parts: Emergency descent valve assembly.