STATS Group hot taps a solution
STATS Group recently completed a complex project for Takreer at Abu Dhabi International Airport, utilising the hot tapping and plugging method to replace 500 m of 10-inch jet fuel pipeline without interrupting production.
STATS Group was contracted by the Abu Dhabi oil refining company, Takreer, to replace a 500 m section of a 10-inch jet fuel pipeline while it remained in production at an operating pressure of 21 bar. Takreer had identified defects in a section of the pipeline, which transports jet fuel from Mussafah to Abu Dhabi International Airport. The defective section was close to a gas pipeline corridor, meaning that no work could take place within the exclusion zone.
STATS Group identified a redundant 10-inch pipeline, which ran parallel to the jet fuel line, as a suitable replacement and developed a rehabilitation proposal that allowed the existing jet fuel line to be re-routed at either side of the gas corridor and tied into the redundant pipeline. This method prevented the pipeline operator from needing to lay a new line through the excluded area.
The project began by first excavating both pipelines – the defective jet fuel line and the unused 10-inch pipeline – at either side of the gas corridor and preparing the 500 m section of redundant pipeline to be used as the replacement section. A cold cutting machine was used to remove short sections of pipe spools and gain access to the redundant pipeline.
Following this, STATS Group placed a temporary pig launcher and receiver, attaching one to each bare end of redundant pipe with mechanical connectors. A pre-installed gauging pig in the launcher ran through the redundant pipeline to the pig receiver on the opposite side of the gas corridor.
The line was then hydro-tested to confirm its integrity, before the temporary launcher and receiver were used to run a number of bi-directional and foam pigs to clean, dewater and dry the pipeline.
To complete the next stage of the rehabilitation project STATS Group employed the hot tapping and plugging method. Hot tapping and plugging is a technique used to provide temporary isolation for sections of pressurised pipelines. The method is routinely employed to bypass segments of pipe to facilitate repair, modification or tie-in activities.
Ahead of hot tapping, two split-tee fittings were welded onto the existing jet fuel line – one at either side of the gas corridor. This provided access points to hot tap and deploy STATS Group’s branch installed self-energised plugs (BISEPTM) into the pipeline.
STATS Group developed the patented BISEP technology in response to increasing demand from clients. The company says that the BISEP reduces the number of hot taps and fittings required by incorporating a bypass facility in the BISEP unit’s housing. This enables the BISEP to provide additional isolation and bypass capabilities through a single hot tap fitting.
The development allows the BISEPs to be deployed into the pipeline and set, isolating short sections of pipeline on each side of the corridor and allowing production to continue flowing through the bypass between the BISEPs. The pipe section between the BISEPs can then be drained through a 2-inch hot tap and purged allowing the pipe to be cut and removed.
To allow for production to continue during the tie-in and re-routing procedures, two mechanically installed clamps were installed inboard of the welded split-tees. These provided two further access points for the BISEPs to be deployed into the jet fuel line. Mechanical fittings were used at this location as they could be recovered after work was completed. This allowed STATS Group to avoid using sacrificial welded fittings.
With four hot tap fittings installed onto the jet fuel line, slab valves were attached to the fittings and pressure tests were conducted. The hot tap machine was then attached to each fitting in turn. After each successful hot tap operation and recovery of the pipe coupon, STATS Group deployed a swarf removal tool engineered to collect the metal debris created during the hot tapping operations.
A short stop in production was required while the four hot taps were conducted. This prevented the swarf from travelling through the pipeline allowing successful recovery of the swarf from the line preventing contaminating the jet fuel. With access points created for two BISEPs on either side of the gas corridor, the four BISEPs were attached to the fittings and an 8-inch bypass was installed between the BISEPs on each side of the gas corridor.
With full bore access to the jet fuel line created, long radius bends were welded behind the outboard BISEPs and tied into the empty pipeline. The newly re-routed pipeline was then nitrogen purged and filled with jet fuel. A flanged port on the BISEP housing was tied into a 2-inch offtake on the installed pipe section allowing fuel to flow into the pipeline.
The outboard BISEPs were then unset and recovered into the launcher and the slab valves closed allowing the jet fuel to flow through the re-routed line. The temporary launcher and the receiver were then attached to the pipe behind the inboard BISEPs.
The BISEPs were unset and recovered, and a bi-directional pig was launched with nitrogen through the defective pipe section, displacing the remaining jet fuel from the pipeline to the receiver. A 2-inch port on the receiver was tied into the re-routed pipeline which allowed the trapped jet fuel to be recovered, minimising the loss of fuel and avoiding the requirement to dispose of any fuel.
Additional pig runs were completed on the defective section of pipeline to ensure it was clean prior to abandoning and capping the line. The BISEPs and bypass pipework was then removed from the pipeline and the hot tap machine was used to install 10-inch completion plugs into the flanges of the two welded fittings which remained on the re-routed pipeline.
The complex project was successfully completed with minimal disruption to production and safely executed ahead of the planned schedule. Prior to the deployment of equipment to the worksite, STATS Group conducted a factory acceptance test at its operational base in Musaffah, Abu Dhabi.
Looking at the successful use of the BISEPs on the project, STATS Group Regional Director Angus Bowie said “The advancements made to the BISEP technology allows production to be maintained through a single hot tap fitting while still maintaining double-block-and-bleed isolation. This offers the market significant safety advantages over traditional line stop technology while ensuring production continues uninterrupted, resulting in less fittings, hot tapping and associated services, providing operators with significant efficiencies and cost savings.”
For more information visit the STATS Group website.
This article was featured in the March edition of Pipelines International. To view the magazine on your PC, Mac, tablet, or mobile device, click here.
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