Rawwater provides leak and defect sealing solutions using low melting point alloys called M3. Rawwater’s proprietary technology includes M3Spray in which molten alloy is sprayed directly against a flowing liquid leak to stem it.
Building on the leak sealing feasibility work carried out previously, the project will focus on the testing of Rawwater’s M3Spray for sealing realistic transformer leak scenarios, including on decommissioned transformer parts. Deployability of the solution including access nozzle development for manual application and semi-autonomous robotic integration for controlled deployment will be tested. Alloy containment to ensure that metal particulates are contained and controlled will also be tested.
This work will culminate in a pilot deployment on a transformer (TRL7) on the NGET estate. Following an initial period of 3 months, there is the option to extend the project to include further robotic integration and further scenarios to a wider range of leaks.
Benefits
National Grid procures an increasing amount of mineral oil for top up purposes every year. Fixing the oil leaks will not only reduce the oil requirement but beneficial for overall asset lifecycle health. Fixing the leaks will reduce the mineral oil top up requirements, maintain health, reduce travel to substations (Scope 1 emissions), and maximise the network capacity by reducing the maintenance outages on transformers and other assets. Transformer replacements in RIIO-T2 period is budgeted at over £240M. Savings made due to spend in T1 on asset life extension is £97M. If more transformers can operate longer than currently planned, significant savings can be made, orders of magnitude above the spend of this project, and the end solution.
Learnings
Outcomes
Phase 1: Rawwater’s M3Spray was confirmed as a viable technique for future adoption for transformer oil leak sealing during Phase 1. Phase 2 work initiated to further develop the application of M3Spray to address a wider range of scenarios.
Phase 2: Alloy was safely deployed to the agreed demonstration candidates. Alloy was successfully directed, contained and deposited only on the agreed desired locations. By agreement with NGET, 3 M3Spray seals were left in place for future observation.
TRL 7 achieved. Outstanding aspects of TRL 8 discussed during project close out.
Lessons Learnt
Phase 1: Pilot candidate identification and selection was challenging within project timescales. Selection of a pilot asset within an enclosed space provided operational access challenges. Prioritising a successful pilot narrowed the wider applicability of the Phase 1 approach. Learnings were gained on the level of manual intervention required for the robotic deployment. The gap to a fully remote system proved to be larger than anticipated for a confined space, but significantly dependent on the transformer deployment type and access restrictions. The criticality of spray positioning for repeatability favoured a robotic placement over manual. The collaborative approach meant that, as and when changes occurred, or issues were identified/resolved, or site constraints arose, they could be openly discussed and a plan agreed in line with overall project aims.
Phase 2: Targeting remained the most crucial factor for sealing leaking flanges; targeting the correct area allows the alloy to seal within the defect causing the leak. The spray can be deployed at height with little diminishing effect to leak seal mitigation meaning maximum flexibility for site operations.
A couple of outstanding questions need to be answered by future research and development. For surfaces with oil, paint, and/or dust, the M3 spray had adhesion problems. An adhesive spray was used to ensure the spray sticks to the surface and seals the leak. The project could not confirm if spray penetration inside the transformer could occur and therefore cause oil contamination. As a part of the research, some oil tests were conducted but no pattern was observed to validate the hypothesis that the oil does not penetrate inside the transformer and does not contaminate the oil.
