Thermography
Thermography, specifically infrared thermography, is a non-destructive testing (NDT) condition monitoring technique that quantitatively measures radiative heat emissions from objects to detect thermal anomalies before functional failure occurs. It converts invisible infrared radiation into a thermal image where color gradients represent temperature differences, enabling identification of abnormal heat patterns indicative of degradation.
In shop floor maintenance, thermography is applied for electrical inspections by scanning energized panels, transformers, and circuits to locate hot spots from loose connections or overloaded phases without shutdown. For mechanical monitoring, it detects overheating in bearings and motors due to misalignment or friction by comparing thermal gradients against baselines. Integration with CMMS like ServiceGrid allows automatic work orders when temperatures exceed thresholds, enabling trend tracking and data-driven planning. Fixed thermography uses permanently mounted IR sensors for continuous real-time monitoring, while mobile handheld cameras are used for periodic predictive surveys.
- Ignoring ambient baselines: Failing to establish temperature baselines under typical load and ambient conditions leads to false positives where normal operational heat is misidentified as a fault.
- Surface reflection errors: Misinterpreting reflected infrared radiation from shiny surfaces as actual component heat results in incorrect severity assessments and unnecessary repairs.
- Reactive data usage: Using thermography solely to confirm existing faults rather than anticipating failure trends delays intervention and increases repair costs.
What is the physical limit of detection for standard IR cameras in industrial settings?
Standard industrial cameras detect radiation in the long-wave infrared (LWIR) spectrum (3–14 µm); detection sensitivity is often limited by noise equivalent temperature difference (NETD) values as low as 0.03°C, allowing identification of minute thermal gradients on low-emissivity surfaces if emissivity corrections are applied.
How does thermography integrate with vibration analysis in CBM?
When combined with vibration analysis and oil analysis, thermography forms the triad of Condition-Based Maintenance (CBM); it detects thermal stress (e.g., bearing friction) that vibration may not yet detect at low frequencies, creating a comprehensive reliability picture.
Why is emissivity correction critical in thermographic inspection?
Emissivity (the efficiency of a surface to emit IR energy) varies by material; without correcting for emissivity (e.g., using tape or paint on shiny metals), temperature readings can be inaccurate by tens of degrees, leading to catastrophic misjudgments of asset health.