Seeing Heat Before It Becomes a Problem
Infrared thermography detects temperature differences on surfaces. That’s the simple version. The practical version is that it finds loose electrical connections before they arc, identifies overloaded circuits before they trip, spots bearing failures before they seize, and reveals insulation breakdown in motors before they burn out. It does all of this while the equipment stays online and operating.
Every industrial plant has thermal problems waiting to be found. An annual infrared electrical survey typically identifies issues in 5-10% of connections inspected. In older facilities or plants with deferred maintenance, that number can reach 20% or higher.
Electrical Thermography: Where the Biggest Payoff Lives
Electrical failures account for a disproportionate share of industrial fires and unplanned outages. Loose connections, overloaded conductors, and failing components all generate excess heat before they fail. Infrared thermography catches these problems reliably when performed correctly.
What to Inspect
- Switchgear and breaker panels (main and distribution)
- Motor control centers (MCCs)
- Disconnect switches
- Bus duct connections
- Transformers (connections, bushings, tank surfaces)
- Capacitor banks
- Fuse holders and clips
- Cable trays and terminations
Load Requirements
This is non-negotiable: electrical thermography must be performed under load. NFPA 70B recommends a minimum of 40% rated load for meaningful results. Higher load produces clearer thermal signatures. If you’re scanning a panel feeding equipment that only runs on day shift, schedule your survey during day shift production hours.
Document the load conditions at time of inspection. A connection showing a 15°C rise at 60% load will show a 40°C rise at full load. Without load data, your severity assessment is unreliable.
Severity Classification
NETA MTS-2019 provides a widely used classification system based on temperature rise above reference:
- Priority 4 (1-10°C rise) — Possible deficiency. Monitor and schedule repair during next planned outage.
- Priority 3 (11-20°C rise) — Probable deficiency. Repair at next available opportunity.
- Priority 2 (21-40°C rise) — Confirmed deficiency. Repair as soon as possible. Reduce load if feasible.
- Priority 1 (>40°C rise) — Major deficiency. Repair immediately. Continuous monitoring until repaired.
Always compare to similar components under similar load. A three-phase connection where one phase runs 25°C hotter than the other two is a clear problem — even if the absolute temperature seems reasonable.
Mechanical Thermography: Beyond Electrical Panels
Infrared cameras aren’t just for electrical work. Mechanical applications expand the value of your thermal imaging investment significantly.
Bearing Monitoring
A bearing running hotter than adjacent bearings on the same machine — or hotter than the same bearing on an identical machine — indicates a problem. Absolute temperature matters less than relative comparison. A bearing housing at 85°C might be normal for a high-speed blower but would be alarming on a slow-speed conveyor drive.
Thermal trending catches gradual degradation that might be missed between vibration analysis routes. Monthly thermal snapshots of critical bearings supplement your vibration program at almost no additional cost.
Coupling and Alignment Issues
Misaligned couplings generate heat from increased friction and flexing. A coupling guard that’s significantly warmer than ambient suggests alignment problems worth investigating with a laser alignment tool. Flexible element couplings (tire-type, disc, grid) show this pattern more clearly than rigid couplings.
Steam System Surveys
Steam traps are tailor-made for thermographic inspection. A working trap shows a temperature drop across it — steam temperature on the inlet, condensate temperature on the outlet. A failed-open trap passes live steam through at full temperature on both sides. A blocked trap shows condensate backup with reduced inlet temperature. Survey your steam traps annually at minimum. Failed steam traps waste 5-10% of steam generation capacity in many plants.
Refractory and Insulation
Furnaces, kilns, boilers, and insulated piping all benefit from thermal surveys. Hot spots on furnace shells indicate refractory failure. Warm sections on insulated pipe runs reveal missing, damaged, or water-saturated insulation. These findings directly impact energy costs and can prevent safety incidents from hot surface contact.
Getting the Measurement Right: Emissivity and Environment
Infrared cameras measure radiated energy, not temperature directly. Converting that energy to an accurate temperature requires correct emissivity settings and awareness of environmental factors that affect your reading.
Emissivity Settings
Emissivity ranges from 0 (perfect reflector) to 1.0 (perfect emitter). Most painted surfaces, rubber, and plastics have emissivity values above 0.90, making them easy to measure accurately. Bare metals are the problem — polished aluminum at 0.05-0.10 emissivity will give wildly inaccurate temperature readings unless you compensate.
For electrical connections on bare copper or aluminum bus, apply a small patch of electrical tape or high-emissivity paint at your measurement point. This gives you a consistent, known emissivity target. Just make sure your modification doesn’t create a safety hazard or violate any standards.
Environmental Factors
- Reflected apparent temperature — Nearby hot objects (boilers, steam lines, direct sunlight) reflect off your target and corrupt your reading. Note reflective sources and adjust your camera’s reflected temperature setting.
- Wind — Air movement strips heat from surfaces. Outdoor surveys on windy days produce lower-than-actual readings and can mask real problems. Wind speeds above 15 mph make accurate quantitative measurements difficult.
- Distance — Your camera’s spot size grows with distance. At 10 feet, a small hot connection might be smaller than your measurement spot, meaning the reading averages the hot spot with cooler surrounding material. Know your camera’s IFOV (instantaneous field of view) and stay within the measurement distance for your target size.
Building a Thermography Program
Equipment investment starts around $5,000-10,000 for a camera suitable for industrial electrical and mechanical surveys. High-end radiometric cameras with interchangeable lenses run $25,000-60,000. For most plants, a mid-range camera with at least 320×240 resolution and a temperature range to 400°C covers the majority of applications.
Training matters more than camera quality. ASNT SNT-TC-1A defines thermographer certification levels. Level I thermographers can perform surveys following established procedures. Level II thermographers can set up procedures, interpret results, and train others. At minimum, your in-house thermographer should complete Level I training before conducting surveys independently.
Survey frequency depends on equipment criticality. Critical electrical distribution — quarterly. General distribution — semi-annually. Mechanical equipment — monthly thermal rounds for critical machines, quarterly for the rest. Steam traps — annually or semi-annually.
Document everything with both thermal and visual (digital photograph) images. A thermal image without a corresponding visual photo is hard to identify later. Include equipment ID, load conditions, emissivity used, ambient temperature, and any notes about environmental factors. Your report should tell the story clearly enough that someone unfamiliar with the equipment can locate and understand the finding.