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Equipment Damage
WPH-Q7: While POH with 31/2" DP suing (hook load: 22 t), tile driller applied tile brakes to set the string in the slips. The brake linkage to the drawworks broke and driller lost control over the brakes. This resulted in the uncontrolled descent of tile string with the travelling block hitting tile rig floor. The string was suspended by the elevator and the slips.
The failure of the brake linkage occurred because a threaded connection was welded in position. See slide 3 for scenarios, any threaded connection should not be welded whether its to lock or seal the connection. Do not assume 3rd Party inspectors know your inspection guidelines. Instruct and supervise inspectors. Make drawworks emergency brakes mandatory. Some rig manufacturers do not provide this as a standard item.
Supervision of the inspection process was ineffective and needs strengthening. Emergency brakes were not installed on the hoist. Hoist manufacturer does not install this as standard. The driller tried to slow the traveling block down with the clutch but this was ineffective.


Category:	Safety Alerts	Document Type:	Safety
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