Using a Common Gas Source for Defining DG-ICDA Regions: A Case Study

Defining the boundaries of DG-ICDA regions is a critical aspect of conducting Dry Gas Internal Corrosion Direct Assessment (DG-ICDA).  Gas transmission pipeline operators with multiple laterals which originate from a common trunk line could conceivably consider each lateral or purchase point off the trunk line as individual DG-ICDA regions.  This methodology can result in significantly increased numbers of digs and project reporting needs, ultimately increasing project costs.  In cases where inline inspection was used as the integrity assessment addressing internal corrosion on the trunk line, multiple laterals which tap off the same trunk line can be combined into one ICDA region.  This paper shares a case study in conducting DG-ICDA by combining multiple laterals with take-off points from a common gas source into one ICDA Region, as well as elaborates on the interpretation of the gas hold-up equation, and introduces a practice for considering the impact of flow rate variability on direct examination site selection.