Thermal imaging (infrared thermography) detects faults by making heat visible. Most developing failures (a loose electrical connection, an overloaded circuit, a failing bearing, a blocked cooling path), produce abnormal heat before they break. A thermal camera shows that heat as a coloured image, so a technician can find and fix the problem during a planned inspection instead of after an unplanned breakdown. It is the core tool of condition-based and predictive maintenance.
In Singapore's own environment, thermal imaging pulls double duty: the standard predictive maintenance role above, plus a genuinely useful check for building envelope issues (insulation gaps, roof leaks, moisture ingress) that show up quickly in a climate where humidity and heavy rainfall are constants. A facilities team already carrying a thermal camera for electrical rounds often finds it worth including a quick building-envelope pass on the same visit.
What thermal imaging finds
- Electrical: loose or corroded connections, overloaded phases, unbalanced loads, failing breakers and fuses, hot spots in switchgear.
- Mechanical: overheating motors and bearings, misaligned couplings, belt and pulley friction, gearbox problems.
- Process / building: blocked heat exchangers, insulation gaps, refractory damage, steam-trap faults, moisture and roof leaks.
The specs that matter
| Spec | What it controls |
|---|---|
| Resolution (detector pixels) | How much fine detail you can see. More pixels means clearer images and the ability to inspect from a safe distance. |
| Thermal sensitivity (NETD) | The smallest temperature difference the camera can distinguish. Lower (e.g. ≤ 60 mK) reveals subtle problems. |
| Temperature range | Must cover the equipment you inspect, from cold rooms to hot process equipment. |
| Focus | An out-of-focus thermal image gives a wrong temperature. Autofocus or good manual focus matters. |
How to read the results: comparison, not absolute numbers
The most reliable method is comparative thermography. Compare a component to an identical one under the same load (for example, the three phases of a circuit). A phase running much hotter than its neighbours is the problem, regardless of the absolute temperature. This avoids the errors that come from emissivity and reflected temperature, which affect absolute readings.
Get the measurement right
- Inspect under normal or near-full load. Faults often disappear at low load.
- Set emissivity correctly; shiny metal reflects and reads falsely cool.
- Keep a safe distance from energised equipment and follow your electrical safety procedures.
- Document the hot spot, the load at the time, and a reference image for trending.
Understanding emissivity: why shiny surfaces lie
Every surface has an emissivity value, a number between 0 and 1 describing how efficiently it radiates thermal energy compared to a perfect black body. Painted metal, PVC cable insulation and most switchgear surfaces have a high emissivity (roughly 0.9 to 0.95), which is why a thermal camera's default settings work well on them. Bare or polished metal (unpainted busbars, stainless steel, aluminium) has low emissivity, often below 0.3, and reflects the surrounding thermal environment more than it radiates its own heat. Point a camera at a shiny bus bar next to a hot motor and it can appear to show the motor's heat reflected in the bus bar rather than the bus bar's actual temperature, a false reading that looks alarming or reassuring for entirely the wrong reason. The practical fix used in the field is to apply a small patch of high-emissivity tape or matte paint to a representative spot on the low-emissivity surface, let it stabilise, and use that patch as the reference point for temperature readings on that component.
Worked example: an electrical panel inspection finding
During a routine quarterly scan of a distribution panel under normal load, a technician images each of the three incoming phase connections side by side. Two of the three phase terminations show a similar, unremarkable thermal signature. The third reads noticeably hotter than its neighbours, well above what load alone would explain given all three phases are carrying a similar current. Because this is a comparative finding (one phase deviating from two otherwise-identical phases under the same load), rather than a judgement based on the absolute temperature alone, it points strongly toward a developing high-resistance connection: a loosening terminal screw, a lightly corroded lug, or a connector that was never fully torqued during the last outage. The recommended next step is not to touch the live terminal, but to schedule the connection for tightening or replacement at the next planned outage, and to re-scan immediately afterward to confirm the fix worked. Left unaddressed, a high-resistance connection like this tends to get hotter over time as the resistance itself increases with heat, a feedback loop that can end in a burnt terminal or an arc fault.
Choosing the right camera for the job
Not every application needs the same camera. A facilities team doing general electrical and mechanical rounds is usually well served by a mid-range handheld camera with adequate resolution and a reasonable temperature range. A predictive maintenance specialist scanning large switchgear rooms or inspecting from a safe distance on high-voltage equipment benefits from a higher-resolution model with a narrower lens option, which resolves smaller targets without having to get physically closer to energised equipment. For continuous, unattended monitoring of a genuinely critical asset (a key transformer, a server room, a process line that cannot tolerate unplanned downtime), a fixed-mount thermal camera feeding continuous readings into a monitoring system is worth the extra investment over periodic handheld scans. Thermographic inspection programmes are also commonly referenced against ISO 18434-1 (condition monitoring and diagnostics of machines, thermography) and sit naturally within a broader ISO 55000 asset management approach, both useful reference points when building a business case for a scanning programme.
Build it into a programme
One-off scans find problems; a routine thermal inspection programme prevents them. Establish baselines, inspect critical assets on a schedule, and trend the results so you can see a connection slowly degrading. Unitest Instruments supplies Fluke thermal cameras for every level (from handheld troubleshooting to high-resolution expert models), and can also carry out the inspection for you as a service.