Street Crane ST013: Street Crane Street Crane Overhead Cr...

Symptoms

The upper limit switch fails to stop the hook at the maximum height. The hook block contacts the boom tip, risking structural damage and load loss.

Limit switch mechanical actuator stuck or broken
Limit switch electrical contacts pitted and not conducting
Limit switch position shifted from vibration or impact
Slow-down limit not functioning, causing the motor to approach the upper limit at full speed

Step 1: Test the limit switch by manually actuating it and checking for electrical continuity
Replace if the contacts do not close when the actuator is pressed
Step 2: Verify the limit switch position and adjust per the manual specification
The hook block should stop at the minimum clearance from the boom tip
Step 3: Check the slow-down limit switch, which should reduce speed before the final stop
Adjust the slow-down switch to trigger at the correct height
Step 4: If the limit switch is weight-activated, verify the trip weight on the cable
Adjust the weight position for the correct trip height

Reset: After adjustment or replacement, test the upper limit with a no-load hook to verify correct stopping.

Limit switch: Heavy-duty, IP65, lever-actuated (Match to crane model)
Slow-down limit: Proximity or mechanical type (Adjust to OEM specification)
Limit switch cable: Multi-core, shielded, drag-rated (For weight-activated types)

Q: What is the upper limit switch?
A safety device that stops the hook from traveling above the maximum safe height. There should be a final limit and a slow-down limit for redundant protection.
Q: How do I test the limit switch?
With the hook empty, slowly raise the hook and verify it stops at the correct height. Then test the slow-down limit reduces speed before the final stop.
Q: Can I adjust the limit switch myself?
Only if you are trained and authorized. Incorrect adjustment can cause the hook to strike the boom, causing catastrophic damage. Always test after adjustment.