Understanding Thermography (Infrared Analysis)

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Portable balancer & Vibration analyzer Balanset-1A

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Vibration sensor

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Optical Sensor (Laser Tachometer)

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Balanset-4

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Magnetic Stand Insize-60-kgf

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Reflective tape

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Dynamic balancer “Balanset-1A” OEM

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Thermography, or infrared (IR) analysis, is a non-contact, non-destructive technology that detects and visualises the thermal energy (heat) radiating from an object. A specialised infrared camera captures that energy and converts it into a visual image — a thermogram — in which different colours represent different temperatures, letting a trained thermographer instantly see hot spots and cold spots invisible to the naked eye. In maintenance and reliability work it is used to catch temperature anomalies that are often the very first sign of a developing fault, which makes it a cornerstone of any condition-based maintenance (CBM) program and a natural partner to vibration analysis and oil analysis.

1. Definition: What is Thermography?

Every object above absolute zero radiates energy in the infrared band, and the hotter it is, the more it radiates. Thermography exploits this physical fact to make temperature visible. Because the camera never touches the equipment, surveys can be carried out on live, energised, running plant from a safe distance — a decisive advantage when the alternative is shutting a machine down or opening an electrical panel. Within a broader condition monitoring strategy, thermography is one of the fastest ways to screen a large amount of equipment for trouble in a single walkthrough.

2. How Does It Work?

An infrared camera carries a detector sensitive to infrared radiation. It focuses the incoming infrared energy onto that detector, which builds up a detailed temperature pattern — the thermogram. The crucial subtlety is that a thermogram maps emitted thermal energy, not temperature directly. To turn that energy map into accurate temperatures, the thermographer must account for two properties of the surface being viewed:

• Emissivity: a measure of how effectively a surface emits thermal energy. A dull, black surface has high emissivity (near 1.0); a shiny, reflective metal surface has low emissivity (near 0.0) and will under-report its true temperature if the camera is not corrected.
• Reflectivity: a shiny surface emits its own heat but also reflects heat from surrounding objects — including the thermographer’s own body — which can masquerade as a hot spot on the target.

A skilled thermographer knows how to set the camera’s emissivity value and how to position themselves to avoid stray reflections, so that the data is both accurate and meaningful. Interpreting the numbers against recognised acceptance criteria is easier with a reference such as our Thermography Temperature Limits calculator (ISO 18434), which relates a measured temperature rise to severity categories.

3. Applications in Electrical Systems

This is one of the most common and valuable uses of thermography, because overheating is almost always the first symptom of an electrical problem.

• Finding loose connections: a loose or corroded connection in a motor control centre (MCC), breaker panel, or switchgear has higher resistance and heats up under load, showing as a distinct hot spot in the thermogram.
• Detecting overloaded circuits: an overloaded breaker or cable runs warmer than its correctly loaded neighbours, making the comparison itself the diagnostic.
• Identifying unbalanced loads: in a three-phase system, a marked temperature difference between phases points to an unbalanced load — a thermal counterpart to the electrical faults that vibration analysis detects on motors.

4. Applications in Mechanical Systems

On rotating and driven equipment, abnormal heat is a reliable marker of friction, wear, or lubrication trouble:

• Bearings: an overheating bearing signals improper lubrication (too much or too little) or advanced wear. Thermography frequently confirms a suspected bearing defect first picked up by vibration analysis, and ties directly to bearing lubrication condition.
• Couplings: a misaligned coupling generates significant heat through friction and cyclic stress, so a hot coupling is a strong alignment clue.
• Gearboxes and pumps: abnormal temperatures point to incorrect oil levels, internal friction, or flow blockages.
• Belts and sheaves: a misaligned belt or one with improper tension makes the sheave run hot, complementing the diagnosis of belt drive defects.

5. Other Applications

Thermography reaches well beyond rotating machinery into plant-wide energy and integrity surveys:

• Steam systems: detecting failed steam traps that are blowing through and wasting energy.
• Refractory and insulation: finding areas where furnace refractory lining or pipe insulation has degraded, showing as a hot patch on the outer surface.
• Tank levels: the liquid level in a large tank can often be “seen” from the temperature difference between the liquid and the vapour space above it.

6. Thermography Within a Multi-Technology Program

Thermography is at its most powerful as one layer in a broader predictive maintenance strategy rather than a standalone tool. As a form of non-destructive testing, it answers the question “is something getting hot?“, but it rarely tells you the root mechanical cause on its own. That is where it pairs so well with vibration. A telling example is unbalance: a thermal survey may reveal a hot bearing, but it cannot say whether the heat comes from a lubrication fault or from excess dynamic load driven by an out-of-balance rotor. To separate the two you need to measure the vibration directly — and where the cause is unbalance, a portable two-channel analyser such as the Balanset-1A can confirm it by measuring 1× amplitude and phase and then correct it by field balancing the rotor in its own bearings, removing the dynamic load that was overheating the bearing in the first place. Used this way — infrared to find the symptom, vibration to find and fix the cause — thermography becomes a fast, safe, and highly effective front line for plant reliability.

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