Global pipeline solutions provider T.D. Williamson (TDW) reports on a trunkline repair project in unusual circumstances.
A beach in a highly populated tourist area is hardly an ideal work site. But when a 42 in. gas pipeline laid parallel to the seashore shifted and became exposed on the beach near Ubhrat, India, crews had to overcome several unique challenges posed by the surrounding landscape and notable environmental forces to ensure a safe intervention. Rough seas due to monsoon, cyclonic storm, high tides, and sour gas notwithstanding, the urgency of the repair left little room for error.
This particular trunkline was completed in 1996. By 2015, the pipeline had shifted approximately 25 m (82 ft.) from its original position and could be seen moving considerably with the tide. In addition, the rising sea level exposed the pipeline in the beach area. This caused a very tense situation around the beach and within the surrounding community, as the authorities immediately put the beach under constant observation over the threat of rupture and possible explosion – and kept it safe until a new pipeline could be commissioned.
In order to carry out the remediation while limiting the amount of downtime and protecting the environment, the pipeline operator, its engineering consultant, and the main contractor worked TDW to develop a safe remediation.
To accommodate for the unique nature of the work site conditions, the TDW team created a customised solution that included hot tapping and then isolating the line using double block and bleed methodology, including the STOPPLE® II plugging system. The solution used a double STOPPLE isolation unit at one end and single unit at the other. According to George Easo, TDW Project Manager, this enabled the repair work to be carried out quickly. As a result, production from the pipeline was shut down for only 21 days, allowing the operator to maintain its reputation for safe operation in the community.
The remediation also helped prevent a potential environmental incident. As predicted, the weakest portion of the line – the insulation joint (IJ) that isolates the offshore and onshore sections – inevitably ruptured in the midst of the hot tapping process.
“We already had our double block and bleed isolation system installed and pressure-tested, on the upstream location,” Easo recalls. “This helped the operator isolate the leaking section at short notice to facilitate the venting, cold cutting, welding of new section, charging, and commissioning.”
Under tight deadlines and harsh environmental conditions, the TDW crew began the challenging task of welding. This involved preheating the fittings at an elevated temperature before welding, in preparation for tie-in of a new section of pipeline. TDW facilitated the replacement of a 1.2 km (0.75 mi) section of pipe on the beach using application-specific hot tapping and line isolation systems, including 42 in. NACE-qualified STOPPLE fittings.
The section replacement was complete 31 July 2015, the line was purged, and gas was charged into the new section. Once the operator verified the safety and integrity of the pipeline, the well was made operational that same day.
“The timeline for completion of the job set by the operator was critical due to the health of the damaged section,” notes Easo. “T.D. Williamson worked closely with the engineering consultant, contractor, and the operator to successfully complete the project on the planned date.”
Edited from source by Elizabeth Corner
Read the article online at: https://www.worldpipelines.com/project-news/03122015/tdw-reports-on-pipeline-repair-during-a-monsoon/