Precision Pipeline Intervention Enables Seamless Gas Segregation

STATS Group was contracted to perform hot tapping and line stopping operations for OQ Gas Networks (OQGN) on their 48” gas pipeline in Sur, Sultanate of Oman. 

Gas flow was maintained continuously through an integrated bypass operating at 75 bar, the operation eliminated the need to shutdown and purge the entire 65km pipeline, significantly reducing greenhouse gas emissions by preventing large-scale venting and flaring.

The integration of the extended gas supply station into the existing 48” pipeline was successfully completed without disrupting service to OQGN customers. By isolating the pipeline section and employing advanced hot tap and BISEP isolation technologies, the project team enabled safe, controlled modifications on a live system—ensuring uninterrupted gas supply and maintaining consistent pressure throughout the operation.

To support the project, STATS provided two 48” BISEPs each with a slab valve, split tee fitting and completion plug, rated to class 600. In addition, STATS supplied SureTap® hot tap machines and personnel for 48” and 2” tapping operations. 

The work scope began with the excavation of a 150-meter straight pipe section on the 48” pipeline, parallel to the new extension of Sur gas supply station. Once the excavation was completed, two split tee fittings were welded onto the 48” pipeline, one at each tie-in location and hydrotested to verify the integrity of the welded joints. Following successful testing of the fittings, STATS 48” slab valves and SureTap hot tap machine were installed. Hot tapping was performed at each location and the pipe coupon recovered, allowing the hot tap machine to be removed providing full bore access for the BISEP isolation tool. With access points created the 48” BISEPs were installed to the slab valves and a 50-meter temporary bypass line was constructed and attached to the BISEP deployment launcher, ensuring continued gas flow once the BISEPs were deployed into the flowing pipeline. 

The BISEPs were hydraulically deployed into the pipeline and activated, each plugging head features dual elastomer seals that are compressed to radially expand against the inside of the pipe wall.  Hydraulic activation allows for high integrity sealing, even in pipelines with internal corrosion, pitting or ovality issues. 

The BISEP offers significant safety advantages over lip seal technologies, with the hydraulically activated dual seals providing leak-tight isolation of pressurised pipelines. Once deployed each BISEP is subject to a test regime to independently test both the primary and secondary seals with full pipeline pressure (80 bar). Each seal is tested in the correct direction and the pressure between the seals is vented, creating a zero-energy zone. The zero-energy zone between the seals is monitored throughout the workscope, confirming the isolation integrity with zero leakage, a crucial factor in the energy industry where any compromise in integrity can have severe consequences. In addition, the line pressure acting against the BISEP pressure head offers a fail-safe feature by providing actuation independent of the hydraulic system. Once the test regime was complete, an Isolation Certificate was issued to notify all parties of the safe isolation of the 50-meter pipe section.

To enable the isolated section to be vented and purged, STATS supplied a mechanical strap clamp with a 2” branched off-take. Once installed to the 48” pipeline, a hot tap machine and valve were installed and the pipeline drilled to provide a vent point. The isolated pipeline section was then safely flared, and nitrogen-purged to eliminate any residual gas. Once gas-free conditions were confirmed, a cold cutting machine was used to remove short sections of pipe spools, and the redundant pipeline section was safely removed. A tie-in pipeline bend spool was precisely positioned and welded into place to provide connection to the Sur gas supply station.

Upon completing the tie-in at both locations and commissioning the extension of Sur gas supply station by introducing gas, the isolation certificate was withdrawn. The BISEPs were then gradually unset and retracted into the deployment launcher, and the slab valves were closed, allowing recovery of the BISEPs and temporary bypass. The hot tap machine was then reinstalled onto the slab valves and used to install 48” completion plugs into the flanges of the welded split tee fittings, ensuring secure and permanent blinding of the system.