Infrared thermography: finding problems before they shut down your plant

A medium-voltage fuse (24 kV) running 5°C above its same-phase counterparts has 2 to 6 months of service life left before catastrophic failure. A €600 thermographic inspection finds it in 30 minutes. The shutdown from an electrical fire costs between €50,000 and €500,000, before counting human risk. That's the base economics of industrial thermography — but most programmes fail not on the technology, but on interpretation.

This article covers what an IR camera sees and what it doesn't, the four main industrial applications, the certification that actually matters (ITC), reasonable inspection frequency, and the typical mistakes that produce worthless reports.

What thermography sees and what it doesn't

Thermography measures surface temperature through infrared radiation emitted by a body. It does not see through walls, metal covers, or closed equipment — only what has direct line of sight to the sensor. This is the main limitation many people overlook.

What it detects well:

• Hot spots in electrical cabinets: loose connections, overload, phase imbalance, harmonic heating, aging contactors
• Mechanical friction: dry bearings, wear, lubrication issues, severe misalignment
• Building insulation defects and process insulation degradation
• Refractory degradation in furnaces
• Fluid system leaks: steam traps, passing valves, compressed air leaks in hot components
• Process anomalies in heat exchangers, reactors, boilers

What it does NOT detect:

• Internal failures of solid components without surface thermal manifestation
• Mechanical defects that don't generate heat (vibration, looseness)
• Electrical noise, partial discharges (better with ultrasound)
• Process chemistry issues

There is a critical distinction between thermal imaging (qualitative, "looks hotter") and quantitative thermography (with emissivity, ambient, and distance corrections, performed by certified analyst). The former works for general findings; the latter is what you sign in a report for an insurer.

The 4 main industrial applications

1. Electrical inspection (60-70% of industrial thermography).

Main switchgear, MCCs, distribution panels, motor terminals, transformer connections. NETA reference thresholds (American electrical testing association, basis for most European criteria):

• Difference <10°C above reference equipment → monitor
• 10-25°C above → repair within 30 days
• More than 25°C above → repair immediately

Frequency: annual minimum, semi-annual on critical switchgear, before and after major maintenance. Hard ROI: prevents electrical fires (€50,000-500,000 events) and unplanned outages. In the EU, electrical inspection regulations (RGIE in Belgium, NF C 15-100 in France) require periodic inspections that thermography complements but does not replace.

2. Mechanical inspection.

Bearings, couplings, drives, gearboxes, motor housings. Detects lubrication failure, bearing degradation, friction, alignment issues. Complements vibration analysis: vibration detects earlier (early stages), thermography confirms once heat begins to manifest (more advanced stages). On critical assets both are done in the same monthly route.

3. Building envelope and process insulation.

Refractory furnaces (hot spots on walls = lining failure), steam piping insulation (cold zones = thermal bridges = energy loss), cold rooms (food/pharma), building envelope (thermal bridges in HVAC = inefficiency). In energy audits, thermography is the primary tool to locate thermal losses.

4. Process control.

Heat exchangers (cold zones = fouling, hot zones = internal bypass), temperature distribution in reactors, steam trap operation (stuck or open traps detected by their thermal signature), thermal distribution in tunnel furnaces.

ITC certification: who's qualified to inspect

The de-facto standard in industrial thermography is the Infrared Training Center (ITC) certification. Three levels:

Level I (32 hours of training): can operate the camera and take measurements, but not sign analyses or interpret.

Level II (80 hours + experience): can analyze, write reports, and make technical decisions in most situations. This is the minimum level Belgian and French insurers (FED, AIB-Vinçotte, Bureau Veritas) accept in official reports.

Level III (200+ hours + years of experience): leads programmes, writes procedures, trains Levels I/II, and signs complex analyses.

National accreditations: BNAT in Belgium, COFRAC in France. For reports going to insurance, Level II ITC is the minimum required. Level I-signed reports are not valid in most claim procedures.

Reasonable inspection frequency

• Critical electrical (main switchgear, transformers, primary MCC): semi-annual + after major events (overcurrent, lightning, significant load alteration)
• Standard electrical (sub-panels, secondary MCCs): annual
• Critical mechanical (large rotating equipment): quarterly, combined with vibration in the same route
• Process equipment (heat exchangers, furnaces): semi-annual
• Building envelope: every 2-3 years or after renovation

Reference cost in Belgium: €1,500-4,000 per day for a Level II analyst with a calibrated camera. A medium plant with 50-100 critical points typically takes 1-2 days.

How to read a thermal image correctly

Emissivity changes everything. Polished aluminium (ε=0.05) vs painted steel (ε=0.95) shows radically different apparent temperatures for the same actual temperature. Without emissivity correction, a real hot spot can read cold and vice versa. Any report without documented emissivity per point is suspect.

Reference comparison, not absolute values. In three-phase electrical installations, you compare the three phases against each other — not absolute temperature against a fixed threshold. One phase 15°C above the other two is a problem, even if all three are "cool" in absolute terms.

Distance and angle matter. The camera's D:S ratio (distance-to-spot) limits the minimum detectable feature. A camera with D:S 100:1 at 1 m distance detects 10 mm spots; at 5 m, 50 mm. An angle greater than 30° from perpendicular distorts the reading.

Reflections. Shiny surfaces reflect the environment (including your body, lamps, other hot equipment). In cabinets with polished metal surfaces you must orient to avoid reflections.

Atmospheric attenuation. Water vapor and CO2 absorb IR. Shots beyond 10 metres in high humidity lose accuracy. That's why inspections are made as close to the target as possible.

Mandatory documentation per point: ambient temperature, load condition, distance, angle, emissivity used, time of day. Without this, the report is a collection of pictures with no evidentiary value.

Mistakes that produce useless reports

Inspecting at low load. A hot spot only manifests under load. An inspection done during scheduled maintenance, with the plant at 30% load, doesn't detect faults that show up at 100%.

Wrong emissivity setting. Using 0.95 (default) on surfaces that require 0.3 produces 50°C+ temperature errors.

Inspecting through glass or polycarbonate. These materials are IR-opaque. What you see is not the component on the other side — it's the glass face.

Comparing readings between different conditions. A winter shot vs a summer shot, morning vs afternoon, without normalising for ambient, is not comparable.

No baseline thermal signature. Without a history of how the installation looks when working well, you can't detect drift.

Pictures without context. A single thermal image is worthless; it needs equipment ID, load condition, time, analyst data.

Closing

Infrared thermography is probably the predictive maintenance technique with the best initial ROI: a calibrated camera and a Level II certified analyst find more faults in a week than a vibration programme does in a month — but only during the route. Vibration monitors 24/7; thermography is periodic.

The reasonable strategy: minimum annual electrical thermography across the whole installation, semi-annual on critical, quarterly on critical mechanical combined with vibration. Level II ITC analyst. Rigorous documentation per point. Without those four elements, you'll have nice pictures and no actionable findings.

If you want a free thermographic audit on your installation's critical points + recommendation of a periodic plan, reach out. You can also see our predictive maintenance offer, which combines thermography with vibration and oil analysis.