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newSchoolWorks.com › VoTechWorks › Manufacturing & Marine › Industrial Maintenance › Predictive Maintenance Technologies for Industrial and Marine Systems › Lesson 5
MFG-INDU16-07 · Lesson 5 · 15 clock hours · demo

Infrared Thermography: Principles, Equipment, and Electrical Applications

Objective. Students will operate a thermal imaging camera, adjust emissivity settings for common industrial surfaces, and identify at least three types of electrical anomalies (loose connection, load imbalance, failing component) from thermal images.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed engineer or certified journey-level tradesperson or by a certification or approval body. It is a study draft and may contain errors. Do not use it as instructions for work on a job site or on live equipment. Always follow your instructor, your supervising professional, and current official references and regulations.

VoTechWorks program approval and accreditation are still in progress. Credentials are issued only by the certifying bodies named in each program, after their own exams.

What Infrared Thermography Does

Every object above absolute zero emits infrared (IR) radiation. A thermal imaging camera detects that radiation and converts it into a color- or grayscale-coded image called a thermogram. Hotter areas appear as lighter tones or warm colors (red, orange, yellow); cooler areas appear darker or blue. In industrial maintenance, this lets a technician see heat that would otherwise be invisible — loose electrical connections, overloaded breakers, failing bearings, and dozens of other fault conditions — without touching the equipment.

Thermal cameras used in industrial work are radiometric, meaning every pixel stores an actual temperature value, not just a color. That lets you measure a specific spot, draw a region of interest, and calculate the temperature difference (delta-T) between a suspected fault and a known-good reference.

Emissivity: Why It Matters

The camera calculates temperature from the amount of IR energy it receives. That calculation depends on a material property called emissivity (ε) — the ratio of IR energy a surface actually emits compared with a perfect emitter (a blackbody, ε = 1.0). Polished bare metal has low emissivity (often 0.1–0.3), meaning it reflects IR from surrounding objects and looks misleadingly cool or hot. Painted surfaces, rubber insulation, and oxidized metal have high emissivity (0.85–0.95) and give much more accurate readings.

If you aim the camera at a shiny copper busbar and leave emissivity at 0.95, the displayed temperature will be wrong — possibly by tens of degrees. Always set the camera's emissivity to match the surface you are measuring. When in doubt, apply a small patch of matte black tape (ε ≈ 0.95) and compare it with the bare surface beside it to expose the error.

Electrical Anomalies and Temperature-Rise Criteria

Three fault types are the focus of this lesson:

Loose connection — Resistance increases at the contact point. Resistance heating (P = I²R) concentrates heat at the lug or terminal. The hot spot is usually small and sharply defined. On a three-phase panel, compare the suspect lug with the same lug on the other two phases; a significant temperature rise on one is a strong indicator.

Load imbalance — When one phase carries substantially more current than the others, its conductors, breakers, and neutral connections all run warmer across their entire length. The thermogram shows one phase consistently brighter than the others, without a single sharp hot spot.

Failing component (motor starter or breaker) — Internal deterioration — worn contacts, degraded insulation, failing bimetal strip — raises resistance inside the device. The entire component body may be elevated in temperature relative to identical components on adjacent poles or circuits.

NETA MTS temperature-rise guideline (referenced as a general framework — always consult the current edition of the ANSI/NETA MTS standard for exact values):

Delta-T is measured between the suspect component and a reference — either an identical component at similar load on an adjacent phase, or the component's ambient background.

Safety Before the Camera Is Ever Raised

Infrared inspection of energized electrical equipment is performed on live equipment. That means arc-flash hazard exists. Before the inspection:

1. Confirm the incident energy level for the panel. The arc-flash hazard analysis (or label on the panel) tells you the required arc-flash PPE category.

2. Wear the full arc-flash PPE set for that category: arc-rated face shield or arc flash hood, arc-rated gloves, FR clothing, and safety glasses beneath the face shield.

3. Inspect through an infrared inspection window or with the panel door held at the correct angle — never remove covers with the equipment energized unless your facility's electrical safe work procedure specifically permits it and you have the proper training and PPE.

4. Keep a second qualified person present.

5. Never reach inside the panel. The camera is held outside; the lens does the work.

Lockout/tagout (LOTO) applies whenever you induce faults in a training panel for practice or perform any physical work inside the panel. In this lesson's training scenario, the panel is de-energized and locked out while faults are set up, then re-energized under controlled conditions for the thermal scan — following your facility's energized electrical work permit process.

Camera Operation Workflow

1. Allow the camera to warm up (stabilize) per the manufacturer's specification.

2. Set emissivity for the primary surface you will measure.

3. Set distance, humidity, and reflected ambient temperature if the camera supports those compensation fields.

4. Establish a reference point — an identical component at similar load.

5. Capture a radiometric image. Save it with the camera's location, equipment ID, date, time, and load conditions.

6. Calculate delta-T between the anomaly and the reference.

7. Use the NETA MTS guideline to assign a priority rating.

8. Write a work-order description that includes: equipment ID, location, fault type, measured temperature of anomaly, reference temperature, delta-T, load at time of scan, and recommended action.

Clear, complete work-order entries are what allow maintenance planners to schedule corrections before a fault becomes a failure.

Key terms9

Emissivity (ε)A dimensionless value from 0 to 1 expressing how efficiently a surface emits infrared radiation compared to a perfect blackbody (ε = 1.0); must be set correctly on the camera for an accurate temperature reading.
Radiometric cameraA thermal imaging camera that stores a calibrated temperature value for every pixel, allowing measurement and delta-T calculations rather than just producing a color picture.
Delta-T (ΔT)The temperature difference between a suspect component and a reference component or background; the primary number used to assess fault severity under temperature-rise guidelines.
NETA MTSANSI/NETA MTS — Maintenance Testing Specifications published by the InterNational Electrical Testing Association; provides industry-standard temperature-rise criteria for classifying thermal anomalies in electrical equipment.
ThermogramThe false-color or grayscale image produced by a thermal camera, in which color or brightness represents relative infrared emission (and therefore surface temperature).
Arc-flash PPEPersonal protective equipment — including arc-rated face shield or hood, FR clothing, and arc-rated gloves — required when working on or near energized electrical equipment that presents an arc-flash hazard.
Load imbalanceA condition in which the current is unequally distributed among the phases of a three-phase system, causing one or more phases to run at elevated temperature across the entire conductor run.
Infrared inspection windowA permanently installed, rated viewport in an electrical enclosure that allows a thermal camera to see inside without opening the panel door, reducing arc-flash exposure risk.
Reference temperatureThe temperature of a known-good, similarly loaded component used as the baseline for calculating delta-T when evaluating a thermal anomaly.

Worked examples4

1. A thermal scan of a three-phase motor control center shows Phase A lug at 52 °C, Phase B lug at 51 °C, and Phase C lug at 89 °C, all at similar load. What is the delta-T for Phase C, and what priority does the NETA MTS guideline assign?
  1. Step 1 — Identify the reference temperature. Phases A and B are similar to each other: average reference = (52 + 51) / 2 = 51.5 °C.
  2. Step 2 — Calculate delta-T: ΔT = 89 °C − 51.5 °C = 37.5 °C.
  3. Step 3 — Compare to NETA MTS ranges. A ΔT of 37.5 °C falls in the 21–40 °C band.
  4. Step 4 — Assign priority: 'Investigate immediately; repair at next opportunity.'
Answer: Delta-T = 37.5 °C. NETA MTS classification: investigate immediately, repair at next opportunity.
2. A technician sets emissivity to 0.95 and measures a shiny aluminum busbar at 43 °C. A matte black tape patch on the same busbar reads 61 °C. Which reading is more accurate and why?
  1. Step 1 — Recognize that the camera calculates temperature from IR energy received, scaled by the emissivity setting.
  2. Step 2 — Matte black tape has emissivity ≈ 0.95, which matches the camera setting of 0.95. The tape reading (61 °C) represents the actual surface temperature accurately.
  3. Step 3 — Polished aluminum has emissivity roughly 0.05–0.15. With the camera set to 0.95, it interprets the low IR emission as a cool surface, producing a large underestimate (43 °C).
  4. Step 4 — Conclusion: the tape patch reading of 61 °C is accurate. The bare aluminum reading (43 °C) underestimates actual temperature by approximately 18 °C due to emissivity mismatch.
Answer: The matte tape reading (61 °C) is accurate. The bare aluminum reading (43 °C) underestimates by ~18 °C because low emissivity of polished aluminum was not matched in the camera setting.
3. A circuit breaker body reads 74 °C. An identical adjacent breaker at the same load reads 38 °C. Calculate delta-T and state whether this requires immediate action per the NETA MTS guideline.
  1. Step 1 — Delta-T = 74 °C − 38 °C = 36 °C.
  2. Step 2 — Locate 36 °C in NETA MTS ranges: 21–40 °C band.
  3. Step 3 — Action per guideline: investigate immediately; repair at next opportunity. This is a serious finding that should not wait for a routine maintenance window.
Answer: Delta-T = 36 °C. Action required: investigate immediately; repair at next opportunity.
4. A work-order entry must record a loose lug fault. The lug temperature is 105 °C; the reference lug on Phase B is 62 °C; load at scan time was approximately 80% of rated. Write the essential data fields for the CMMS entry.
  1. Step 1 — Equipment ID and location: enter panel tag number, bus section, and physical location.
  2. Step 2 — Fault type: 'Loose lug connection — Phase A terminal.'
  3. Step 3 — Measured temperature of anomaly: 105 °C.
  4. Step 4 — Reference temperature: 62 °C (Phase B lug, same load).
  5. Step 5 — Delta-T: 105 − 62 = 43 °C.
  6. Step 6 — Load condition at time of scan: approximately 80% of rated load.
  7. Step 7 — Priority per NETA MTS: ΔT > 40 °C — serious; remove from service or repair immediately.
  8. Step 8 — Recommended action: 'De-energize under LOTO; re-torque lug to manufacturer spec; re-inspect thermally after repair.'
Answer: CMMS entry includes: equipment ID, location, fault type (loose lug Phase A), anomaly temp 105 °C, reference temp 62 °C, ΔT = 43 °C, load ~80%, NETA priority = serious/repair immediately, recommended action = LOTO and re-torque.

The math in this lesson1

Learners compute delta-T between phases and against reference components to set repair priority.
N-Q.3
Brush up in the math halls at newSchoolWorks.com:
In class: Instructor demonstrates thermal camera operation on a live demonstration electrical panel (with appropriate arc-flash PPE and inspection window open); students observe how the image changes when emissivity is adjusted from 0.5 to 0.95 on a painted versus bare-metal surface, and record observations. · Students rotate through a demonstration station where three faults have been induced in a de-energized (then re-energized under controlled conditions) training panel — a deliberately loose lug, an overloaded circuit breaker, and a failing motor starter — using the thermal camera to capture images and classify each fault using the NETA MTS temperature-rise criteria (referenced as a guideline). · Students analyze five printed or projected thermal images from real industrial surveys, identify the anomaly in each, note the approximate delta-T above reference, and write a brief work-order description suitable for entry into a CMMS.
Materials: Thermal imaging camera (radiometric, with adjustable emissivity); demonstration electrical training panel with induced faults; arc-flash PPE (arc-rated face shield, gloves, FR clothing, safety glasses) sized for the panel's available fault current; NETA MTS temperature-rise guideline handout; printed thermal image sets; CMMS work-order form
Check: Students correctly classify all three faults on the training panel using the thermal camera and justify their classification in writing using the temperature-rise guideline; pass mark: all three faults correctly identified and documented.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

NCCER Industrial Maintenance — Predictive Maintenance
1. A thermal camera is aimed at a polished stainless steel surface with emissivity set to 0.95. Compared to the actual surface temperature, the displayed temperature will most likely be:
NCCER Industrial Maintenance — Electrical Safety
2. When performing a thermal inspection of a live motor control center, which action BEST reduces the technician's arc-flash exposure risk?
NCCER Industrial Maintenance — Predictive Maintenance
3. Phase A of a three-phase bus reads 95 °C; Phases B and C read 54 °C and 56 °C at similar load. Using the NETA MTS temperature-rise guideline, what is the correct delta-T and priority classification?
MSSC CPT — Maintenance Awareness
4. Which thermal pattern BEST indicates a loose lug connection rather than a load imbalance?
NCCER Industrial Maintenance — Electrical Safety / LOTO
5. Before setting up induced faults in a training panel, the correct electrical safety procedure is to:
MSSC CPT — Quality and Maintenance Documentation
6. A CMMS work-order description for a thermal anomaly should always include which of the following data?
NCCER Industrial Maintenance — Predictive Maintenance
7. A motor starter body reads 10 °C above an identical adjacent starter at the same load. Using NETA MTS guidelines, the appropriate response is to:
MSSC CPT — Maintenance Awareness
8. Why is it important to record load conditions at the time of a thermal scan?
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