Delivering Safe In-Line Isolation for Critical Valve Replacement, North Sea

When an Emergency Shutdown Valve begins to pass - losing the seal integrity it exists to provide - it has to be replaced. That is not negotiable. What is negotiable is how you create a safe isolation upstream of it, particularly when the line has no pig launcher or receiver through which to introduce an isolation plug.

This was the situation on a 14" offshore gas export line in the North Sea. The valve was passing. The line needed isolating. And there was no conventional means of getting the isolation tool in.

The ESDV on the 14" gas export line was failing to hold. With a passing valve, breaking containment for the change-out without a verified, monitored isolation in place was not an acceptable risk.

Standard Remote Tecno Plug deployment uses a pig launcher to introduce the tool into the pressurised line. This line had no launcher or receiver installed - ruling out the conventional approach from the start.

A full assessment of the pipeline routing, bend radii, and internal bore transitions identified a single viable isolation location: a short straight section immediately downstream of the ESDV, directly before a 90-degree topside bend. That was the available geometry. Any solution had to work within it.

STATS' scope covered two interdependent elements: the 14" Remote Tecno Plug isolation and a temporary certified pig launcher, engineered specifically for this pipeline. The launcher incorporated the necessary bends and a specially fabricated end connection designed to integrate directly with the existing No.1500 hub on the pipeline system - creating the access point the line lacked.

The restricted straight length at the isolation location required an unconventional plug configuration. With insufficient space to position the full tool string in a single straight run, the Remote Tecno Plug's remote modules were positioned within the adjacent 90-degree bend, ahead of the isolation module - allowing the isolation module itself to be set within the available straight section.

Once set, the dual seal configuration provided an annulus void between the two seals for continuous monitoring. Each seal was independently pressure tested before any pipeline intervention began, confirming a fully certified double block and monitor isolation.

The project was delivered through close collaboration between three specialist teams. STATS Group led the pipeline isolation and temporary launcher scope. Prism Energy managed the overall project coordination. Valvetight provided the DBB-SAVER solution for safe installation and reinstatement of the temporary launcher package.

The integration of three specialist scopes - isolation engineering, project management, and launcher installation - required precise sequencing and clear communication at every stage. The result was a controlled, safe working environment in which the ESDV change-out could proceed with confidence.

The ESDV change-out was completed with a fully certified, double block and monitor pipeline isolation providing the safe working environment throughout. No unplanned product release. No compromise on isolation integrity in a demanding offshore environment.

For North Sea operators managing infrastructure where the means of intervention were never part of the original design, this project demonstrates that a reliable, certified isolation is achievable - even where the pipeline itself offers no obvious route to one.