Will fractures propagate in a leaking CO_2 pipeline?

摘要

AHYPOTHETICAL CONCERN has been raised that leaks in a CO_2 pipeline could escalate to a propagating fracture.This is due to the potentially large temperature drop associated with the expansion of either gaseous or dense-phase CO_2 to ambient conditions. It is suggested this local cooling would lower the pipe wall temperature to an extent that a brittle fracture would initiate followed by a transition to a propagating fracture. Although such a mechanism could theoretically occur in natural gas pipelines, there is increased concern for CO_2 transport because of the different thermodynamic behaviour of the contents, particularly for dense-phase transport. This paper critically reviews the literature associated with this postulated failure mechanism and other studies on the cooling of cracks and holes by escaping fluid. It is concluded that pipelines constructed to modern standards are not at risk. Limited crack extension may occur when the leak is through a 'tight' crack in a material of low toughness. However, the crack will arrest as it enters warmer material remote from the leak. Escalation to a propagating fracture can be controlled using methods which are widely used and understood in the pipeline industry.