Pipeline coating refurbishment of 475 km was completed under Phase-I of project for rehabilitation of 1157 km long cross-country crude oil pipeline laid during 1960-63 with a goal to enhance its operable life by another thirty years. Complex geographic terrain through riverine valleys, high ground water levels, infrastructure developments beside and across the pipeline right-of-way over the decades, shorter dry work season available for pipeline coating works, multiple parallel pipelines etc. posed unique challenges during execution of construction works at field. As a prioritization strategy, 40-50% of pipeline segments from cathodic current injecting stations were newly coated under Phase-I project.
While 3-ply/2-ply cold applied tape coatings were satisfactorily and productively used for coating refurbishment, Visco-elastic coatings were found to be very effective in hindrance conditions of limited access for pipeline surface preparation, higher humidity and dealing with slightly pitted pipeline surfaces. Petrolatum tape coating systems were effectively used for encapsulating pipeline in marshy and muddy areas where pipeline cannot be opened up for coating for more than a few meters due to unstable soil conditions. Use of heavy-duty HDPE composite mats eased excavation of trench in slushy areas. In addition to coating refurbishment, repairing of cased crossing, re-coating of block valves, installation of monolithic insulating joints, revamping of cathodic protection system were also carried out under the pipeline rehabilitation strategy.
Result of the pipeline rehabilitation is observed in the form of improved cathodic protection level to comply NACE-SP0169 requirements captured through CIPL survey for the newly coated sections and improved attenuation of CP current to balance pipeline portions. During direct assessment of pipeline before re-coating, many pipeline anomalies could be traced and rectified.
Learning from Phase-I project is guiding project management strategy for rehabilitation of balance portion of the pipeline and in adopting a comprehensive pipeline integrity management solution.