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
The results from the project so far may be summarised as follows:
· Confirmation that M3Spray is a suitable technology for use for transformer leak sealing (safety and operational aspects tested and reported on).
· A deployable ‘site ready’ solution for two specific scenarios and sealing of those scenarios in a pilot deployment (TRL 7 option).
· Small-scale lab-based tests set up and conducted within a bespoke indoor rig which simulates the conditions within a transformer, to establish optimal spray and deposition parameters, based on site requirements and success criteria.
The testing to date, using untreated cork with a channel leak produced approximately 90% mitigation, which is encouraging at these early stages of testing. The testing indicates that distances of 40mm or 120mm between the nozzle and the sample, plus longer spray times showed the best mitigation in this configuration. This information should be tempered with the knowledge that the greater distance between the nozzle and the sample, plus the longer spray times both give a greater risk of overspray, therefore further testing to identify the optimal set up for both sealing ability and practical application is required.
The used, oil saturated Nebar with multiple leaks across the length has shown a mitigation rate of up to 50%. As expected, the leak rate is significantly lower than the channel leak, showing the importance of having good understanding of the pilot site leak and a representative small-scale rig.
Recommendations for further work
Following an initial period of 3 months, if the transformer seals are performing well, there is the option to extend the project to include further robotic integration, and further scenarios to make the sealing technique applicable to a wider range of leaks (TRL8).
Lessons Learnt
While outside of the scope of this formal proposal, further scope could explore M3Spray automation to prepare for wider pilots and eventual roll out across the network. This would take the form of a robotically controlled elevated work platform and a robot with enhanced automation capabilities, to cover a wider range of access environments. Detail to be agreed upon project confirmation. This would result in TRL 8 level technology.
Dissemination
A poster presentation on the metal alloy leak sealing technology was given to other utilities and innovators attending the Energy Innovation Summit in Liverpool in October 2023. The project was displayed again for other utilities at the Innovation Zero Event in London in May 2024.
