Rawwater Engineering Company Ltd / National Grid Trials Rawwater's Novel Greenhouse Gas Sealing Capabilities

National Grid is collaborating with UK-based Rawwater Applied Technology, to trial the SME’s novel M3 Molten Metal Manipulation leak sealing capabilities as a rapid, safe and highly effective way of sealing harmful sulphur hexafluoride (SF6) greenhouse gas leaks from electrical equipment.

Across the global electricity generation and supply industry, SF6 - a synthetic, inert gas - is used to insulate low, medium and high-voltage switchgear installations and act as an arc suppressant to prevent short circuits and fires. The greatest downside to SF6, however, is that it is the most potent greenhouse gas in existence with more than 23,000 times the warming potential of CO₂.

Rawwater’s 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 application techniques are low temperature and require no curing time, allowing for in-service application against flowing leaks. Both techniques were successfully trialled at National Grid’s Deeside Centre for Innovation in September 2021.

For the Deeside trial, Rawwater’s M3 alloy spray was applied in difficult-to-access areas to demonstrate its deployability in restricted environments. The M3 CollarCast was then used to heavily mitigate flowing nitrogen leaks (used to simulate SF6) at pressures of up to 7bar, without the need for a system outage. The reversibility of the M3 process was also demonstrated, to show that equipment can be returned to its original state for decommissioning, with any recovered alloy being retained for reuse. As a result of the Deeside trial, National Grid and Rawwater will now test M3 Molten Metal Manipulation against contained SF6 leaks.

“There are countless SF6 installations in electricity generation and supply globally,” comments Rawwater Applied Technology’s managing director, Kat Lennox. “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. 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.”

“The trial of Rawwater’s M3 leak-sealing capabilities at our Deeside Centre for Innovation was greatly encouraging,” comments National Grid’s Innovation Lead, Gordon Wilson. “Whilst equipment using SF6 as an insulator is intended to be permanently sealed, as it ages, the potential for leaks increases, especially for equipment installed outside where it is exposed to harsh environments over many decades. Investigating new techniques to prevent loss of SF6 to the atmosphere is one of the ways innovation can contribute to National Grid’s commitments to reduce emissions and achieve Net Zero. Rawwater’s M3 Molten Metal Manipulation technique has given us the opportunity to trial an effective, safe and simple means of sealing SF6 leaks, one that I expect to be similarly effective for alternative gases to SF6 in due course.”