Your eyes see reflected light. A thermal imaging camera sees radiated heat — the infrared energy every object above absolute zero emits — and turns it into a temperature map. For maintenance, that is a superpower: faults that produce heat become visible long before they produce noise, vibration, or failure.
Electrical connections run hot for weeks before they arc and start a fire. A bearing generates friction heat before it seizes. A steam trap fails open and the downstream pipe glows differently than its neighbours. A motor winding runs ten degrees hotter than its sisters because it is overloaded. All of these are invisible to the eye and the ear, and all of them show up cleanly on a thermal image. This is why thermography is one of the core condition-monitoring technologies, alongside vibration and oil analysis.
What Thermography Detects
The faults fall into a few families.
Electrical — the killer application. Loose, corroded, or oxidised connections have higher resistance, and higher resistance means heat. A loose lug on a motor control centre, a degrading contactor, an unbalanced fuse — each shows up as a hot spot, often tens of degrees above its neighbours. Catch it on inspection, torque or replace the connection, and you have prevented an arc flash, a fire, or an unplanned line shutdown. Electrical thermography under load is the single highest-value inspection a plant can run.
Mechanical friction. A bearing running dry or failing generates heat at the race. A gearbox with low oil or a failing gear runs hotter than its baseline. Couplings out of alignment heat at the interface. These often show up thermally before the vibration signature is clear.
Fluid systems and steam. Steam traps that fail open or closed change the thermal profile of the line — blocked traps run cold downstream, blow-through traps run hot. Blocked or fouled heat exchangers show a reduced temperature differential. Level detection in sealed tanks is possible because the fluid and the gas above it sit at different temperatures.
Refractory and insulation. Furnace and boiler casing hot spots reveal refractory damage or insulation breakdown before the casing fails. Roof and building-envelope surveys find wet insulation and heat loss.
Motors and drives. A motor running hotter than identical sister motors under the same load is being overloaded, has a winding fault, or is losing a bearing. Phase-to-phase temperature imbalance points at electrical asymmetry.
How It Works
Every object radiates infrared energy proportional to its temperature. The camera's detector array measures that radiation across a scene and assigns each pixel a temperature, producing a false-colour image where white and yellow are hot and blue and purple are cold. Two modes matter for maintenance:
- Qualitative (comparative) thermography — the workhorse. Compare similar components under the same load: the three phases of a breaker, two sister motors, the bearings on either end of a shaft. A component running noticeably hotter than its twins is the suspect. This catches most faults without needing accurate absolute temperatures, and it does not require an emissivity expert.
- Quantitative thermography — measuring actual temperatures against thresholds. Harder, because the reading depends on the surface's emissivity, reflected background, distance, and the camera's calibration. Necessary when you are checking against a specification ("do not exceed 90 °C"), but overkill for most comparative inspection.
Doing It Right
The quality of a thermography program lives in the inspection discipline, not the camera.
- Inspect under load. Electrical and mechanical faults only produce heat when current is flowing and machinery is running. A thermography survey done during a shutdown finds nothing.
- Compare like with like. A phase running 15 °C above its two siblings is the finding. An absolute "this breaker is 55 °C" means little without knowing what its identical siblings run at under the same load.
- Mind the emissivity. Shiny metal surfaces — bare copper bus bars, polished stainless — reflect infrared and read falsely cold. Paint them, apply electrical tape, or use a reference standard. This is the single biggest source of wrong thermography readings.
- Be consistent. Same time of day, same load conditions, same route, same camera settings. Trending the same connection across surveys only works if the survey is comparable each time.
- Cadence. Critical electrical distribution annually at minimum; high-criticality or high-cycle equipment semi-annually. Mechanical and steam surveys on a rolling route tied to criticality.
A qualified thermographer — the ISO 18436-7 certification is the recognised standard — pays for themselves fast on a medium-sized electrical infrastructure, because they find faults a non-trained operator misses and they do not produce false positives that waste maintenance effort chasing ghosts.
Where It Sits in the Stack
Thermography complements the other condition-monitoring technologies rather than competing with them. Vibration catches mechanical looseness, imbalance, and bearing fault frequencies — motion problems. Oil analysis catches wear debris, contamination, and lubricant degradation — fluid problems, often earliest. Thermography catches heat — most valuable on electrical systems where the other two do not apply, and a useful cross-check on mechanical assets where a hot spot confirms what the vibration trend is suggesting. A mature program runs the relevant technology per asset class: thermography on the electrical distribution and the high-temperature plant, vibration on the rotating equipment, oil analysis on the gearboxes and hydraulics. (For how these signals combine into a remaining-life estimate and a work-order trigger, see our piece on remaining useful life.)
How OpexMX Handles It
OpexMX schedules thermography routes per asset, stores each inspection's thermal image against the asset record, and trends hotspot temperatures across surveys — so the same lug that ran 8 °C hot last quarter and 18 °C hot this quarter auto-flags before it arcs. Findings from a survey open a corrective work order against the exact component in the image, with the thermal picture attached. The result is thermography that turns into work orders, not a folder of pictures that nobody reviews.
See how OpexMX turns thermography surveys into trend-triggered work orders →