A high-pressure nitrogen cylinder on a drill rig floor ruptured unexpectedly, destroying the cylinder rack and propelling other cylinders up to 15 meters away. The rupture was caused by severe corrosion at the cylinder’s base, which was missed during a visual inspection three months prior. The cylinder was near the end of its 10-year hydro test cycle and was difficult to inspect without disassembling the quad. This incident emphasizes the importance of thorough inspections, proper cylinder storage on free-draining bases, and compliance with industry regulations to prevent similar occurrences, reports IMCA.
What happened
A high-pressure Nitrogen cylinder in a quad of 12 cylinders located on a drill rig floor ruptured without warning. The cylinders were charged to 2,400psi and were not connected to anything else at the time of the incident. The rack was destroyed and the other cylinders in the quad were propelled by the blast up to 15m away.
Why did it happen
The base of the cylinder that ruptured was heavily corroded. Other cylinders in the quad had evidence of similar but less severe corrosion.
The cylinders were 9 years into their 10-year hydro test cycle and had been visually inspected by the supplier by applicable industry guidance, when they were refilled some three months before the incident, before being loaded out to the rig. However, the severe corrosion that caused the rupture was not spotted during this inspection;
The cylinder that ruptured was located in the middle of the quad and therefore not easy to properly inspect without disassembly of the quad.
Calculations showed that the fatal blast zone for a single cylinder of this size pressurized to 2,400psi would be around 1.5 meters. The severity of the blast caused the rack to be destroyed and the other cylinders to be propelled across the deck.
Lessons learned
- Are the cylinders on your facility or vessel certified and in good condition?
- Are you able to see the condition of all cylinders in every rack?
- Are all cylinders located on a free-draining base to minimize corrosion?
- Do you know what level of visual inspection of cylinders/quads is provided by your supplier?
- Are all cylinders in your facility stored and located according to the relevant industry regulations?
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Source: IMCA
