24" Remote Tecno Plug, Dunlin Alpha Platform, North Sea, UK

Tool - Remote Tecno Plug Isolation Tool
Location - North Sea - UK
North Sea - UK location on a map
Operating Environment - Offshore Topsides
Pipeline Medium - Oil
Activity - Valve Repair / Replacement
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Tecno Plug IWTT Dunlin

Fairfield Energy Ltd had a requirement to replace the two launcher valves on the 24” oil export line from Dunlin Alpha to Cormorant Alpha. In order to undertake this operation safely and efficiently STATS proposed the use of a remotely operated Tecno Plug. The Remote Tecno Plug provides double block and bleed isolation and eliminates the need for communication tethers or specially modified pig trap doors. This allows the old valves to be removed without the requirement for tether management. 

Remote Tecno Plug Holds for 72 Days on Dunlin Alpha

When Fairfield Energy Ltd needed to replace the two launcher valves on the 24" oil export line running from Dunlin Alpha to Cormorant Alpha, the central challenge was straightforward to state and demanding to solve: keep the pipeline isolated and verifiably safe for as long as the workscope required, without communication tethers or specially modified pig trap doors complicating the operation.

With a shutdown window of up to 80 days and the Remote Tecno Plug serving as the primary isolation on the export pipeline, the requirement was not just for effective isolation - it was for isolation that could hold, monitored and verified, for the full duration.

The Challenge: Two Launcher Valves, a Live Export Line, and an 80-Day Window

Fairfield Energy's requirement was to replace both launcher valves on the 24" oil export line from Dunlin Alpha to Cormorant Alpha. The isolation needed to be double block and bleed, providing a fully verified safe worksite for the duration of the valve changeout and any subsequent maintenance activities.

Because the Remote Tecno Plug would be the primary isolation on the export pipeline, it needed to be rated and proven capable of holding for the full scheduled shutdown - up to 80 days. That requirement shaped how the tool was configured and how it was qualified before mobilisation.

Highlights

  • 72 days of continuous, monitored isolation - the longest remote pipeline isolation in STATS history at the time of the project.
  • Three-module Remote Tecno Plug configuration, with a dedicated contingency battery module, purpose-built for an up-to-80-day shutdown window.
  • Client-witnessed Factory Acceptance Test in a purpose-built onshore fixture replicating the Dunlin Alpha offshore pipeline configuration.
  • Bespoke 24" In-Line Weld Test Tool with extended body and lock module - designed for the specific bore differential of the newly installed valves.
  • ELF (Extremely Low Frequency) radio tracking used to position and monitor the plug throughout the full 72-day isolation.
24in Remote Tecno Plug Remote Tecno Plug 3D render

Qualifying the Solution: Piggability Study and a Client-Witnessed FAT

Following a site survey, STATS carried out a piggability study on the oil export line to confirm the pipeline geometry and verify that the Remote Tecno Plug could be reliably deployed to the required isolation location. The study informed the tool configuration for this specific pipeline.

The Remote Tecno Plug was configured in a three-module train. The additional module housed a contingency battery unit - designed to support the full 80-day shutdown duration. Before mobilisation, STATS carried out a full Factory Acceptance Test onshore, with a Fairfield Energy representative present. The FAT was conducted in a purpose-built test fixture created specifically to replicate the offshore pipeline configuration at Dunlin Alpha.

Setting the Plug: ELF Tracking and Isolation Certificate

Onsite, the Remote Tecno Plug was function-checked and loaded into the launcher. It was then pigged to the isolation location using a mixture of water and nitrogen. Positioning was achieved using STATS' through-wall ELF (Extremely Low Frequency) radio control system, which allowed the plug to be accurately tracked and placed without tethers or modifications to the pig trap doors.

Once the plug was set and its position confirmed, the ELF system continued to monitor the isolation throughout the workscope. On issue of the Isolation Certificate, valve changeout and maintenance activities commenced.

Holding for 72 Days: A New Benchmark

The Remote Tecno Plug remained set in the pipeline for 72 days while the valve replacement and associated maintenance work was completed. Throughout that period the plug was continuously monitored and remained stable at its set location.

At the time of the project, 72 days was the longest duration remote isolation in STATS history.

This successful workscope has marked a new milestone for STATS, our Remote Tecno Plug was constantly monitored and remained stable and in location for seventy-two days while maintenance operations were completed, this is now the longest duration remote isolation in STATS history.

dvernon
Dave Vernon
Technical Advisor
STATS Group

Testing the New Valves: A Bespoke In-Line Weld Test Tool

Once the new valves were installed, STATS provided a bespoke 24" In-Line Weld Test Tool with an extended body and an additional locking module to pressure-test the newly made-up flange joints. The extended body was designed to straddle both flanges of the new valves simultaneously.

A standard In-Line Weld Test Tool would have presented a problem here: the new valves had different internal bores, meaning that with test pressure applied, a standard tool would have moved due to differential pressure across its face areas. The lock module addressed this directly - set prior to each test, it prevented the tool from creeping under pressure.

The tool was positioned using a modular stem bar arrangement, allowing it to be placed precisely in each of three test locations and retrieved cleanly between them. As part of the planned maintenance scope, the operator also replaced a 1.5" pig signaller, which STATS pressure-tested using a separate 1.5" Flanged Weld Test Tool.

On successful testing of all valves and flanges, the Remote Tecno Plug was unset and reverse-pigged back to the launcher for demobilisation.

We have developed a good relationship with Fairfield Energy Ltd and are currently discussing the use of STATS isolation technology for future maintenance activities.

dvernon
Dave Vernon
Technical Advisor
STATS Group

A Demonstration of Duration and Reliability

The Dunlin Alpha project established a new benchmark for remote pipeline isolation. The ability to configure the Remote Tecno Plug for an extended-duration workscope - with a contingency battery module, a client-witnessed FAT, and ELF monitoring throughout - gave Fairfield Energy the verified isolation they needed to carry out the valve replacement safely, on schedule, and without tether management constraints.

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