The Bureau of Safety and Environmental Enforcement (BSEE) draws lessons learned from an incident where the fatigue cracking of a ¾-inch pipe nipple led to offshore gas release.
BSEE has investigated a recent offshore gas release incident resulting from the failure of a ¾-inch pipe nipple connected to a compressor suction scrubber.
The failure led to an immediate platform shut-in and a full muster of personnel onboard. The released gas posed a significant safety risk, particularly due to its proximity—within 10 feet—to hot compressor surfaces, increasing the potential for fire or explosion.
Fortunately, there were no injuries or significant equipment damage; however, the event highlights how minor component failures can escalate into serious safety threats under slightly altered conditions.
Incident findings:
Post-incident inspection revealed that the threaded ¾-inch pipe nipple failed due to fatigue cracking, which had likely developed progressively over time. The fatigue cracking was consistent with long-term exposure to mechanical stress and cyclical loading in a high-vibration environment. Threaded connections of this size are especially vulnerable to fatigue when installed on vibrating equipment such as compressors.
Contributing factors:
- Over-tightening: Excessive torque during installation may have introduced stress concentrations, weakening the pipe.
- Vibration: Continuous vibration from compressor operations likely accelerated fatigue.
- Unsupported Weight: The nipple also supported a sight glass level bridle, potentially adding stress to the connection.
- Component Loosening: Vibration may have contributed to the loosening of the connection over time, compounding mechanical stress.
Lessons learned:
- Add structural support for sight glass level bridles attached to compressor suction scrubbers to reduce weight and vibration loads on small-diameter pipe nipples.
- Apply proper tightening techniques to avoid over-stressing threaded connections during installation.
- Regularly inspect critical components—including pipe nipples, fittings, and supports—for signs of fatigue, corrosion, wear, or loosening. Initiate timely corrective actions as needed.
- Implement vibration monitoring on compressor packages to detect and manage vibration levels that may affect connected piping and equipment.
- Ensure vibration dampers are properly installed and maintained to reduce the transmission of vibration from compressor units to piping components.
