Lessons learned: Overhaul ball crashes to deck resulting in high … – SAFETY4SEA

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BSEE (United States Bureau of Safety and Environmental Enforcement) informs of an incident where, a 700-pound crane headache ball fell 24 feet, while conducting crane operations during a decommissioning/well abandonment activity.
The incident 
A crane was moving a 400-pound well cap from one well access panel to an adjacent panel when a wedge socket on the auxiliary line snagged on the flange of a C-channel located at the edge of the platform’s rig deck.
The lift required running the crane’s auxiliary line within inches of the edge of the platform rig structure. the wedge socket above the headache ball snagging on the C-channel flange that ran across the length of the edge of the deck. This snag temporarily held all the weight of the load and rigging, resulting in a false reading on the auxiliary winch. The load cell sending a weight signal to the operator was located below the snagged wedge socket. The crane operator did not detect that the auxiliary winch was no longer holding the weight of the load.
The rigger did not realize that the line had snagged on the C-channel and continued giving directions to keep lowering the well cap. As the load cell (which
work by converting a specific type of mechanical force — typically tension, torque, compression, or pressure — into an output signal. This output signal is then transmitted via a load cable to the scale’s indicator where the precise weight can be measured and read by the crane operator) was positioned below the snag, there was no change in the load signal, even though the weight of the load was now being supported by the C-channel and not the auxiliary winch.
The rigger, not seeing any movement, repeated a request to lower the load. Because the crane operator could not see the winch drum behind the crane cab,
he did not see that the load was not moving and responded that he was still lowering the load. As the crane operator continued to unwind the auxiliary line at the winch drum, the wedge socket slipped off the flange of the C-channel, releasing the snag. The 700-pound headache ball fell 24 feet, striking the deck less than two feet from one of the riggers guiding the load.
After the incident, a third party inspected the crane, replaced a small three-inch pin for the hook latch, and the crane was placed back in service.
What went wrong?
Lessons learned
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© 2021 SAFETY4SEA

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