Description of Driving Event:
A counterbalance cable had become disengaged from the upper support beam pulley during assembly operations. This was caused by the work scaffold (used to access the upper beam area) making contact with the counterweight. The tension in the cable was relieved, allowing it to slip from the pulley groove. When the load was reestablished, tension was reapplied to the counterbalance cable, pulling the weight free and allowing it to fall.
Lesson(s) Learned:
Counterbalance cables on single flange mount pulley systems can be dislodged easily from the pulley by physical contact on the counterweight.
Recommendation(s):
Install pulley assemblies with double flanges to prevent cable from being dislodged during assembly or maintenance operations.
Evidence of Recurrence Control Effectiveness:
N/A
Documents Related to Lesson:
N/A
Mission Directorate(s):
N/A
Additional Key Phrase(s):
- Ground Equipment
- Lifting Devices
Additional Info:
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