Risk assessment of an urban natural gas polyethylene piping system

The integrity management activities should aim to ensure that all safety requirements are maintained within acceptable levels. A fully comprehensive inspection of all equipment in a unit/facility is not a cost-effective method. Therefore, in recent approaches, the budget and resources are assigned in a way to only fully cover the equipment with a medium-high or high-risk level, while preserving a sufficient effort on lower risk components. In this regard the risk assessment procedure of the underground polyethylene (PE) natural gas piping networks has not been developed yet. Hence, the current study was conducted to (1) identify the credible failure mechanisms in urban natural gas PE piping systems and (2) evaluate the probability of failures and consequences of failures for various failure scenarios. The ultimate goal was to find the critical piping segments. It proposed a methodology to prioritize technical inspection activities for different segments in the urban natural gas piping systems based on their risk levels. The procedure was applied in the piping network of a small city (Ardabil, Iran) to identify the critical segments. Relevant recommendations were made after successfully detecting these segments.