Every GIS substation and SF6 circuit breaker needs leak detection, but the detector itself is chosen from several different technologies, and they are not interchangeable. The right choice depends on what the survey must achieve: finding very small leaks, quantifying routine leaks, or a general-purpose check. This guide explains the main technologies, their strengths and the questions to ask before buying.
The three main technologies
Halogen (heated diode) detectors are the simplest and cheapest class. A heated ceramic diode senses halogen gases, including SF6. They are light and easy to use, but they are not selective – they respond to any halogen gas, including refrigerants and cleaning agents that may be present in the same building – and their sensitivity and stability are limited. They are adequate for a quick presence/absence check but not for quantitative measurement.
Negative ion capture (electron capture) detectors – such as the HUWOR HMJ-9051-SJ – are highly sensitive to SF6 and give a fast response as the probe moves along a joint. The negative ion capture principle is well suited to finding small leaks and to measuring concentrations in the low parts-per-million range. According to the published specification, the HMJ-9051-SJ has a detection range of 0-2000 ppm.
Infrared (NDIR) detectors – such as the HUWOR HMJ-9051-S – measure SF6 by its infrared absorption, using a dual-beam, dual-wavelength design that cancels drift and contamination. They are selective to SF6, stable over long surveys and free of consumable sensing elements, which makes them the best choice for quantitative routine surveys where the readings must be comparable between visits.
Choosing by survey type
| Survey type | Recommended technology | Why |
|---|---|---|
| Find very small leaks, maximum sensitivity | Negative ion capture | Highest sensitivity to trace SF6 |
| Routine quantitative surveys, comparable readings | Infrared NDIR | Stable, selective, no consumables |
| General-purpose presence check, low budget | Halogen | Cheapest, adequate for gross leaks |
| Environmental reporting with quantified leak rates | Infrared or calibrated negative ion | Quantitative output for records |
Questions to ask before buying
- What is the target detection range? A detector specified for 0-2000 ppm covers routine survey concentrations; trace-level work needs higher sensitivity.
- Is the reading quantitative? A meter that only indicates presence cannot prioritise repairs or support environmental reporting.
- How stable is the calibration over a day of surveying? Dual-beam infrared designs resist drift; simple sensors may need frequent re-zeroing.
- Are there interfering gases on site? In a building with refrigerant or solvent use, a selective detector (infrared) avoids false readings.
- Does the probe reach the inspection points? Check the probe length and flexibility for flanges and valve blocks.
- What is the consumable cost? Infrared cells have no consumables; some sensor types have elements that must be replaced periodically.
Building the survey into a programme
A detector is only the measurement layer. The full programme also includes continuous gas pressure monitoring on the compartments (to flag falling trends), a survey schedule, and a repair and refill record. The portable detector fits into this programme as the layer that finds and quantifies the leak once the trend flags the compartment.
Summary
Halogen detectors are the cheap presence check, negative ion capture detectors are the sensitive leak finder, and infrared NDIR detectors are the stable quantitative choice for routine surveys. The HUWOR range covers the two professional classes – the HMJ-9051-SJ (negative ion, 0-2000 ppm) and the HMJ-9051-S (infrared) – with OEM/ODM support. Contact the HUWOR sales team for a comparison based on your survey schedule.