National Grid targets leaks of most potent greenhouse gas with molten metal

Leaks of a highly potent greenhouse gas from electricity infrastructure could be tackled by metal sprays, according to the National Grid.

The network operator is testing the use of Molten Metal Manipulation (M3) technology from Rawwater at its Deeside Centre for Innovation.

The trials aim to demonstrate the application of M3 technology to stopping leaks of sulphur hexafluoride (SF6) from the grid’s pipework. SF6 is commonly used in electricity infrastructure to prevent short circuits and maintain safety and reliability, but the highly insulating gas is the most potent known greenhouse gas, 23,500-times more potent than carbon dioxide (CO₂).

The M3 process involves the use of either a ‘leak extinguisher’ alloy spray, or an easily deployed ‘CollarCast’, where molten alloy is cast into a custom-made, reusable mould. Both techniques are relatively low temperature and require no curing time, National Grid said, allowing for in-service application to flowing leaks. 

The operator tested the M3 alloy spray in difficult-to-access areas, while the CollarCast process was trialled to heavily mitigate flowing nitrogen leaks – used to simulate SF6 – at pressures of up to 7bar, without the need for a system outage.

The tests also demonstrated the reversibility of M3 with a simple process that involves reheating, showing that equipment can be returned to its original state for access to pipework.

“Even though the phase-out of SF6 is planned around the world and alternative gases exist for gas-insulated switchgear, it will be many years before this highly insulating greenhouse gas is eradicated from electricity supply networks,” said Kat Lennox, managing director of Rawwater. “Until that day, a rapidly deployable solution is required to seal or mitigate SF6 leaks. This successful trial gives us confidence that Rawwater’s M3 Molten Metal Manipulation is part of the answer.”

National Grid and Rawwater will now test the leak-sealing capabilities of the M3 technology against contained SF6 leaks.

The Deeside facility is also hosting trials of Cemfree, a patented cement-free concrete mixture with the potential to reduce carbon footprint by 80% compared to conventional concretes. National Grid is testing two large slabs to identify the differences in performance between Cemfree and a conventional concrete.

The material, which could be used on substations to reduce construction emissions, saved approximately 13 tonnes of CO₂ emissions compared to a Portland 100% cement binder.

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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.