What Is SF6 Optical Gas Imaging?
SF6 optical gas imaging (OGI) is a survey technique that makes an invisible gas visible. Sulphur hexafluoride — SF6 — is the insulating and arc-quenching medium sealed inside high-voltage gas-insulated switchgear (GIS), circuit breakers and gas-insulated lines. It is colourless, odourless and impossible to see when it escapes, which is exactly what makes a slow leak so difficult to locate by conventional means. An OGI survey solves that by using a specialised infrared camera tuned to the narrow wavelength that SF6 absorbs, turning an escaping plume into a clearly visible cloud on the operator's screen.
In practice, our operator scans each vulnerable point of the equipment — flanges, bolted joints, density gauges, valves, bushing seals and gas-insulated line connections — while watching the live infrared feed. Where gas is escaping, it appears as a moving, smoke-like plume drifting away from the leak source. Every finding is recorded on video with its location and an estimate of relative severity, so the maintenance team receives not just an alarm but a precise picture of which component is leaking and how badly. This is a specialist survey within our broader industrial drone inspection and substation inspection work.
Why SF6 Leaks Matter
SF6 is prized in electrical engineering because of its exceptional dielectric strength and its ability to quench the arc that forms when a high-voltage breaker opens. Those same properties make it the gas of choice for compact, reliable switchgear in dense urban networks like Singapore's. But SF6 carries a serious downside: it is the most potent greenhouse gas known, with a global warming potential in the region of 23,500 times that of carbon dioxide and an atmospheric lifetime measured in thousands of years. A small, persistent leak that would be trivial for most substances becomes an outsized environmental liability for SF6.
The cost of a leak is threefold. First, the gas itself is expensive and increasingly hard to source as global supply tightens, so every top-up to restore pressure is a direct financial hit. Second, falling gas density erodes the dielectric strength that keeps the switchgear operating safely; left unchecked, a leak can push a compartment towards a low-gas alarm or, ultimately, a dielectric failure. Third, the escaped gas is a reportable emission. Regulators, network operators and asset owners are under growing pressure to measure and cut SF6 emissions as part of a global phase-down of the gas, so an untraced leak is also a compliance and reputational exposure.
The traditional alternative to OGI is point sniffing — walking a handheld gas detector across every joint and waiting for a reading. It works, but it is slow, it only samples where the probe is held, and it struggles to locate the exact source on a large GIS lineup. OGI inverts that: instead of sampling point by point, it lets the operator see the whole plume at once and follow it straight back to the leaking component, dramatically shortening the time from "we are losing gas" to "here is the flange to repair".
How OGI Leak Detection Works
The physics is straightforward. SF6 absorbs infrared energy strongly at a specific wavelength. An OGI camera pairs a cooled infrared detector with a spectral filter matched to that absorption band, so escaping gas intercepts part of the background infrared radiation and renders as a distinct moving cloud on the display — light or dark against the scene depending on the thermal contrast. The gas remains completely invisible to the naked eye, yet the camera resolves it clearly enough to trace a wisp back to the millimetre-scale gap it is leaking through.
A survey is methodical. The operator works across the equipment holding a steady standoff and viewing angle, scanning the components where SF6 most commonly escapes and adjusting position to use the background and any air movement to reveal faint plumes. Each confirmed leak is captured on video, annotated with its location on the asset, and given a relative severity so repairs can be prioritised. OGI is a locating tool rather than a metering tool, so it complements — rather than replaces — the SF6 density gauges that monitor each compartment and any quantitative sniffer measurement used to size a confirmed leak. Together they answer the two questions that matter: where is it leaking, and how much.
Where Drones Add Reach
It is worth being clear about how drones fit in, because much SF6 leak detection is, and should be, done handheld at ground level. For accessible GIS bays, breaker enclosures and switchroom equipment, a technician on foot with the OGI camera gives the best control over angle, standoff and background — there is no reason to fly. The honest value of a drone is reach: it extends the same OGI survey to components that are otherwise out of practical reach.
That matters most in outdoor switchyards and on tall structures. Elevated GIS terminations, air-insulated bushings high on a gantry, and flanges on gas-insulated lines routed overhead are slow and hazardous to reach with scaffolding or elevated work platforms, and often require an outage to access safely. Flying the OGI payload lets us scan those components from the air, in service, without work-at-height exposure for the inspector. Our approach is to use drone reach only where it genuinely adds value and survey everything reachable from the ground, so the data quality on each component is as high as the access allows.
- Ground-level handheld — accessible GIS bays, breaker enclosures and switchroom gear, scanned on foot for maximum control.
- Drone-assisted — elevated terminations, outdoor bushings and overhead gas-insulated lines reached from the air, in service.
- No shutdown to locate — the survey finds leaks while equipment stays energised, so repairs can be planned rather than forced.
- Video-documented — every leak is recorded with location and relative severity for a clear repair-priority record.
What We Survey
SF6 escapes from a predictable set of interfaces on gas-insulated equipment. Our survey concentrates on these, scanning each one deliberately rather than sweeping past.
GIS Flanges & Joints
The bolted flanges and compartment joints of gas-insulated switchgear are the most common leak paths as seals age and gaskets take a set. We scan the full run of interfaces across the GIS lineup.
Breaker & Bushing Seals
Circuit breaker enclosures and bushing seals see mechanical operation and thermal cycling that work their seals over time. Both are prime OGI targets, including elevated bushings reached by drone.
Density Gauges & Valves
Fill valves, service ports and the density gauges that monitor each compartment are small fittings that leak disproportionately often. We image every fitting and connection point.
Gas-Insulated Lines
Gas-insulated lines and their connection assemblies, frequently routed overhead, are scanned along their length and at every joint — the parts a drone reaches most usefully.
The Value of an OGI Survey
The payback from finding SF6 leaks quickly is tangible. Every leak located and repaired is gas that no longer has to be topped up, cutting both the direct cost of replacement gas and the labour of repeated recharging. Restoring and holding compartment density also protects the dielectric margin that keeps the switchgear safe, reducing the risk of a low-gas alarm or an unplanned outage. And because the escaped gas is a potent greenhouse emission, every leak closed is a measurable reduction in the asset's environmental footprint.
Just as important is the record the survey leaves behind. A dated OGI dataset showing which components leak, and by how much, feeds directly into environmental reporting and emission estimates, and demonstrates that leaks are being actively identified and rectified rather than tolerated. It also sharpens maintenance planning: instead of a blanket top-up schedule, the asset owner gets a ranked list of the specific flanges, valves and seals that need attention. This dovetails with our related LDAR fugitive-emission surveys and partial discharge inspection for a fuller picture of switchgear health.
Standards & the SF6 Phase-Down
SF6 handling sits within a well-established framework. IEC 60376 sets the quality specification for SF6 used in electrical equipment, and IEC 62271 governs high-voltage switchgear and controlgear, including gas-handling and monitoring requirements. CIGRE has published extensive guidance on SF6 management — from gas handling and re-use to leak minimisation — that the industry treats as the practical reference for keeping emissions low. Our OGI surveys are designed to support these obligations by providing the leak-location evidence that any credible gas-management programme depends on.
The wider context is a global push to phase down SF6 and to report the emissions that remain, reflected in tightening regulation across many networks. In Singapore, the electricity network operates under EMA regulation, and asset owners are increasingly expected to account for their SF6 inventory and losses. We cite these standards as the backdrop to our work; we do not issue equipment certification or gas-quality certificates, and we do not invent compliance claims. What we deliver is accurate, documented leak-detection data that your engineers and gas-handling specialists can act on and report against.
Why Choose SG Drone Inspections
We are a specialist drone and industrial inspection provider in Singapore, and SF6 OGI is a focused capability within that work rather than an afterthought bolted onto a generic thermal service.
SF6-Specific OGI
We survey with an optical gas imaging camera tuned to the SF6 absorption band, so leaks show as visible plumes — not the generic thermal hotspots a standard IR camera would miss.
Elevated & Outdoor Reach
Handheld where access is good, drone-assisted where it is not. Elevated terminations, outdoor bushings and overhead lines are covered without scaffolding or a shutdown.
Video-Documented Leaks
Every confirmed leak is recorded on video with its location and relative severity, giving you traceable evidence rather than a verbal report.
Repair-Priority Report
Findings are compiled into a ranked, component-by-component report so your team can plan repairs by severity and feed the data straight into emission records.
Frequently Asked Questions
Book an SF6 Leak Detection Survey
Tell us your site, the switchgear type and whether components are indoor GIS or outdoor switchyard. We reply with a scope and quote within 24 hours — no obligation.