Cause & Consequence
- Other
Incident Location
Drilling unit
Incident Activity
Drilling, workover
Lessons Identified
WHAT CAUSED IT:
The operation was stopped during the process of breaking off the stand, rather than waiting until the Driller had the block at the floor for the start of the cycle; The rig operator did not notice that the clutch had not dumped its air when the clutch control was released to neutral;
The clutch control had debris in the control mechanism, thus preventing the air’s release and signaling to the dump valves to dump the air to the clutch;
The Driller noticed the brakes were not acting normal about two stands before the incident took place, but thought that the brakes had merely gotten water on them;
The brake flange was leaking water and the driller thought the sluggishness of the brakes was due to water on the flanges.
Incident Recommendations
CORRECTIVE ACTIONS:
To address this incident, this company did the following:
Instructed Drillers not to hand over control of the rig in the middle of breaking out a stand—set it back and bring the blocks to the floor in order to begin a new cycle in the procedure.
Instructed Drillers to listen for changes; investigate smells; investigate the feel of controls or any changes in vibration.
o Things have a “normal” sound, appearance, smell and feel. The Driller should have investigated the cause when the brake felt sluggish for the two prior stands.
o A change in the sound of the brake or the sound of the air in the clutch dumping a few seconds late are indicators that something is wrong.
o If the brakes become wet the sound changes as they are applied.
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