Catastrophic rupture of dead-leg pipe-work
Issue Date: 20.08.2019
Target Audience:
- Operators of Process Plant (and associated inspection bodies) which may have pipe-work dead-legs on toxic, flammable, dangerous to the environment or other critical services.
- Oil and gas (onshore / offshore)
- Chemical processing and production
- Nuclear
- Pharmaceutical
- Power production
Key Issues:
This safety alert highlights the increased risks of primary containment loss associated with dead-legs that may be present on process pipe-work. Dead-legs are lines containing process fluids under stagnant, no or low flow conditions.
In a recent incident, there was a significant leak of hot hydrocarbon under pressure when a dead-leg failed catastrophically, leading to a full-bore rupture of the pipe. This resulted in the loss of an estimated 75 tonnes of boiling hydrocarbon to the atmosphere, but a major catastrophe was avoided as the resulting vapor cloud did not ignite. The investigation found that significant pipework wall loss had taken place in the failed dead-leg, but that this was highly localized and had been missed by the pipework examination regime; various thickness checks were routinely being made, but these were either side of the locally corroded area. This incident has highlighted the risks of dead-leg corrosion, and that existing integrity management regimes may be inadequate to manage the threat of highly localized internal degradation, particularly when a thermal gradient, liquid interface or other feature may be present along the dead-leg.
The purpose of this safety alert is to highlight the risks of corrosion in dead-legs and where they can’t be eliminated, remind operators of the guidance on how to inspect these areas to avoid loss of containment.