SCC Direct Assessment on 16 gas line in Ahwaz region and considering the coa ng def ect as pr i ma r y factor to det er mi ne SCC

The National Iranian South Oil Company (NISOC) and TWI Persia Company carry out a pipeline integrity Direct Assessment (D.A) mythology. The assessment covers approximately 7.700 km of gas line as named E-Branch in Ahwaz region with 16 pipe diameter, pipe material 5L-X65, pipe wall thickness 19.05 mm, design pressure 250 BAR and Design temperature 60°C. The pipeline was constructed and commissioned in 1978 and was externally coated with PVC cold wrapping. The pipeline is not piggable, and located downstream of compressor station. In this study it was supposed that for thick coatings, disbondment is in conjunction with coating defect [6]. So, coating defects, that detectable with DCVG, wassupposed to primary factor in determining the SCC susceptible sites.Approximately, in 80% of locations with coating defects of category 1, SCC has been found. Same percentage of SCC was found for locations with category 2. Excavations and inspections for coating defects with category 3 weren’t adequate to extend the results. So, when the main problem of the pipeline is SCC, all categories of the coating defects can be considerable

Keywords:

SCCDA , disbondment , DCVG , intergranular SCC , transgranular SCC