SF6 gas is the insulating and arc-quenching medium in GIS and many high-voltage breakers. Gas loss degrades dielectric and interrupting performance, so finding and repairing leaks promptly is a core maintenance task. A portable quantitative SF6 leak detector gives the field team a ppm reading at the probe tip – enough to distinguish a real leak from background contamination, trace it to its source and verify the repair.
Preparing for the leak survey
- Check instrument readiness – battery, calibration status and a zero/background reading in clean air.
- Collect asset information – which compartments to survey, their gas pressure history and any flagged compartments from density-monitor alarms.
- Plan access – identify joints, flanges, valves, bushing bases and covers to be checked on each bay; confirm access and safety permits for live equipment.
Surveying for leaks
Move the probe slowly along joints and seal lines, holding it close to the surface. Leak points are found by following the concentration gradient: as the probe approaches the leak, the ppm reading rises. Typical leak points in GIS include:
- Flanges and gaskets at compartment joints
- Bushing bases and sealing interfaces
- Valves, filling ports and pressure switches
- Access covers and welds on older equipment
Work in low wind or shielded areas when possible – air movement disperses the gas and makes tracing harder.
Quantifying the leak
Once a leak is located, measure the ppm at a fixed probe distance and position, and record the value with the asset identity, date and environmental conditions. A quantitative record supports:
- Prioritising repairs – large leaks first
- Verifying that a repair actually reduced the leak rate
- Reporting SF6 emissions for environmental accounting
Repair and re-verification
- Repair the leak per the equipment manufacturer’s procedure – re-torque, replace gaskets or apply approved sealant as applicable.
- Re-test the same point with the detector to confirm the reading returns to background.
- Top up gas as needed and check the density monitor reading.
- Record the repair and the before/after readings in the maintenance log.
Instrument considerations
- Quantitative ppm output – distinguishes real leaks from background and supports records.
- Fast response and recovery – lets the operator trace along a joint without long settling delays.
- Rugged design – built for substation work, including high ambient temperatures.
- Calibration routine – repeatable measurements require a defined calibration process.
About HUWOR
Zhuhai Huawang Technology Co., Ltd. (HUWOR) manufactures SF6 quantitative leak detection instruments for GIS and breaker maintenance, supporting utilities and service contractors worldwide with OEM/ODM supply and application guidance. Contact the HUWOR sales team for specifications.