Flow-stop tooling is regularly used for major projects and emergency works across the LTS and NTS gas networks. A pipe loop is being constructed in Spadeadam to assess the suitability of materials, procedures, and equipment with 100% hydrogen gas streams. The opportunity has presented itself to integrate testing (at Spadeadam) on the BISEP® tool delivering technical assurance prior to Grantham to Grangemouth live field trial on the LTS Future project. When successfully completed, a proven double block and bleed leak tight line stopping technology suitable for 100% hydrogen will be available to the UK Gas Networks and the earning gained from this project can be applied to Network Licensees and their operations to facilitate a safe transition to hydrogen from natural gas.
Benefits
The project will provide unique and referenceable information for Network licensees and wider gas Industry on flow-stop tooling. The tool provides a fail-safe double block and bleed isolation deployed through a single full bore hot tap intervention, without the need for additional hot tapped bleed or vent ports. It offers significant safety advantages over traditional line stop technologies, with the hydraulically activated dual seals providing leak-tight isolation of live, pressurised pipelines.
Should the 2024 field trials be successful, sufficient evidence will have been gathered to determine that a safe method of flow stopping across the high-pressure transmission network will be available to the UK gas network in time for the potential transition to a decarbonised energy network.
Learnings
Outcomes
The BISEP tool successfully completed the first phase of testing in the STATS HQ, where it was deployed and hydraulically activated in 100% inert gas as part of the Factory acceptance test (FAT). Each seal was tested independently with full pipeline pressure in the direction of the expected pressure differential, proving both the seals of the double block isolation were leak tight. Following the successful seal proving, the vented annulus void was closed and monitored, confirming isolation integrity throughout the isolation period. Primary and secondary seal tests were performed successfully in water and helinite gas.
Over the course of the testing at Spadeadam, the BISEP tool was confirmed to be functional by proving safe operational compatibility with 100% hydrogen, due to operational constraints, the tool was left fully energised with hydrogen at pressure over night, thus successfully proving the body and ancillary equipment can maintain integrity with 100% hydrogen.
The deployment of the tool was deployed as per procedure, however the ability to seal in line was unsuccessful. This triggered a methodical fault-finding exercise which found a low level of damage on the seal face of the tool, caused by cutting debris in the pipeline. This debris hadn’t been removed from the cutting location, despite the flow conditions or magnets that had been put in place for this purpose. It was determined that due to the horizontal orientation of the tool deployment, normal sweeping of the sealing area with the tool head could not be achieved in comparison to a normal vertical deployment.
Whilst the BISEP did not successfully provide a seal in the test loop, the operational compatibility of operations in 100% hydrogen were proved, as well as proving a successful seal within the unit where debris was present. It is understood that STATS are keen to further support SGN and there is a desire to undertake further developments of the tool to enable removal of the in-pipe debris during the hot tap process. Such a collaborative approach would appear to be beneficial for both SGN and STATS
Key messages from this work are:
· The tool deploys successfully under normal operation; however modifications need to be made in field tests to determine the correct procedure to collect and clear debris from within the pipe cutting site.
· Further work should examine the efficiency of debris removal methods, as well as provide a deeper understanding of the level of damage to the seal that would impact successful sealing in 100% hydrogen environment. This will involve assessing the damage to the seals, as well as providing guidelines for debris removal and sealing capacity.
· It is anticipated that for more common vertical deployment, the issue of swarf affecting the seal performance should be less due to the position of the swarf in relation to deployment action. This could be an additional outcome of later projects.
Lessons Learnt
The aim of the project was to successfully demonstrate the suitability of the BISEP tool in hydrogen operations.
The most significant discovery of the project is that the existence of swarf will make the sealing operation impossible. This demonstrates a need for the development of suitable methods of swarf removal to ensure a relatively clear sealing area. These will form part of the deployment process and will be included in further FAT tests, especially for horizontal deployment. There should also be a criterion of cleanliness established in all hydrogen media operations. It is however noted that horizontal deployment is not common for normal flow stop operations and was a defined requirement for the LTS Futures field trial
