What this is
What is a thermographic survey?
What is a thermographic survey?
A thermographic survey records infrared images of electrical connections, motors and bearings, comparing each point's measured temperature against a reference point to classify a temperature difference, or delta-T, into a severity band. The image is retained so the same point can be compared survey to survey.
Who should carry out a thermographic survey?
A certified thermographer, working under conditions representative of normal load. A trainee's image should be recorded as supervised rather than treated with the same confidence as a certified thermographer's classification.
How is a finding judged severe?
By the delta-T against a comparable reference, banded from monitor through to immediate, with any finding carrying a high safety risk treated as immediate regardless of which band the temperature difference alone would suggest.
Scope
When is a thermographic survey required?
Thermography is one condition-monitoring technique run against the same asset base, answering a specific question: is something running hotter than it should relative to a comparable point. Using it where a different technique is correct produces a record that misses the fault it wasn't built to see.
Use this template when
- Electrical panels, connections, motors or bearings are due their scheduled survey, run yearly or more often on critical assets
- New or repaired equipment needs a baseline image and reading before it enters the regular survey cycle
- A previous survey raised a Watch or Alert and a diagnostic follow-up image is needed on that point
- Post-repair verification is needed to confirm a previously hot connection has actually returned to normal
- A change in load pattern or duty means an earlier reading needs re-checking under the new condition
Do not use it for
- Vibration Analysis Record, which measures velocity and frequency signatures on rotating equipment rather than surface temperature
- Oil Analysis Record, which records laboratory analysis of lubricating oil, wear metals and contamination
- Ultrasonic Inspection Record, which detects leaks, electrical discharge and early bearing friction through ultrasound
- Asset Condition Inspection, which assesses general visual condition rather than a thermal signature
- A component with no accessible line of sight for the camera, where emissivity and reflection make the reading unreliable regardless of temperature shown
Compliance mapping
Which NFPA 70B requirements does this satisfy?
NFPA 70B and ISO 18434-1 govern thermographic inspection practice rather than setting numbered clauses, so the fit is to the guidance and the section it governs.
| Clause | Requirement | Where it lands |
|---|---|---|
| NFPA 70B | Periodic infrared inspection of electrical equipment as a recommended predictive maintenance practice | Header |
| NFPA 70B | Inspection performed under load representative of normal operation for a valid diagnosis | Header |
| ISO 18434-1 | General procedures for thermographic condition monitoring, including ambient temperature and emissivity setting | Header |
| ISO 18434-1 | Classification against a comparable reference temperature, delta-T, rather than an absolute value | Thermal anomalies |
| NFPA 70B | Temperature rise classified into bands determining whether repair is monitored, planned or immediate | Thermal anomalies |
| NFPA 70B | A finding presenting an immediate safety risk requires immediate corrective action rather than scheduled repair | Thermal anomalies |
| ISO 18434-1 | Retention of image evidence so the same point can be compared at the next survey | Thermal anomalies |
What it does not cover
- Vibration analysis, which needs an accelerometer reading and frequency spectrum, not an infrared image.
- Oil analysis, which needs a laboratory sample and result against wear-metal and contamination limits.
- Ultrasonic inspection, which needs an ultrasonic detector reading, not a thermal image.
- General condition inspection, which records visual and physical condition rather than a thermal signature.
- The repair itself, which belongs in the linked work order, not in the survey that found the need for it.
Global
Thermographic Survey requirements by country
NFPA 70B is a US recommended practice, not a statutory requirement, so no jurisdiction mandates this survey by name. What differs is how strongly a documented programme is expected as evidence of maintained equipment.
NFPA 70B recommended practice; insurer and NETA maintenance testing conditions
No OSHA standard mandates thermography specifically, but NFPA 70B is the referenced predictive-maintenance practice, and insurers commonly condition cover on it.
A survey history with delta-T trends and retained images is the evidence an insurer or auditor expects; its absence after an electrical fire is itself a finding.
Electricity at Work Regulations 1989, reg.4(2)
Duty to maintain electrical systems so far as reasonably practicable to prevent danger.
Thermography is accepted evidence of a maintenance regime satisfying the duty; the regulation does not name the technique, so defensibility rests on it being carried out at representative load and acted on.
ISO 18434-1; ISO 55001 asset management
Condition monitoring schemes expect thermographic evidence for critical electrical and mechanical assets.
Auditors look for a defined methodology, comparable readings and a survey interval actually followed, not just a template that exists.
How to complete it
How to complete a thermographic survey, step by step
Most surveys are walked to schedule with a temperature recorded per point. Whether the finding is real, and how urgent, sits outside what the template prompts for.
A connection surveyed at low load reads cooler than at full duty, whatever is developing inside it. Record load at time of survey and treat below-threshold readings as indicative, not comparable to a full-load baseline.
The same absolute temperature can be normal on one component and a developing failure on another. Comparing against a similar reference point, or its own history, is what makes the classification meaningful rather than arbitrary.
A very hot current-carrying connection is a fire and arc-flash precursor. A high safety-risk classification should trigger immediate action, not a place in the queue for the next planned outage, regardless of the delta-T band.
Retaining the thermal image, and ideally a visible-light image, at each point is what makes next year's comparison possible. A delta-T figure alone cannot be re-examined if the classification is queried later or the point needs re-locating.
What auditors find
Most common thermographic survey findings
The camera is usually pointed and a temperature recorded. The findings concern what is missing around it.
| Finding | Clause | What fixes it |
|---|---|---|
| Survey performed below representative load, with no flag against comparability. | NFPA 70B | Record load at time of survey and mark below-threshold readings as indicative, not comparable to baseline. |
| Severity classified from measured temperature alone, with no reference or delta-T recorded. | ISO 18434-1 | Always record a comparable reference temperature and classify from the delta-T, not the absolute reading. |
| High safety-risk finding logged without immediate action taken or escalation. | NFPA 70B | Treat a High safety-risk classification as immediate; record the action taken at the point of finding, not at the next review. |
| No thermal image attached to a required finding. | ISO 18434-1 | Attach the thermal image, and a visible-light image where practical, at the point the finding is recorded. |
| Trainee-supervised image recorded with the same confidence as a certified thermographer's classification. | Analyst competence | Flag trainee-supervised readings and have the certified thermographer co-sign before it is acted on. |
| Recurring hotspot at the same point across surveys, with no trend comparison against its own history. | ISO 18434-1 | Compare each point against its own prior readings, not only the current survey's reference temperature. |
Case in point
Case in point: the joint that read mild at the wrong load
A busbar joint was surveyed during a partial production run, load reduced for an unrelated changeover. The measured temperature was only slightly above the reference point, classified under 10 degrees, monitor. The survey was signed off on schedule and the next inspection set for a year out.
Three weeks later the joint failed at full production load, tripping the section and causing an unplanned outage. The investigation found the connection's resistance had been rising for two consecutive surveys, but both had coincided with reduced load, so the readings stayed mild even as the fault worsened. The fix was procedural: load at time of survey is now recorded against every point, and any below-threshold reading is flagged and scheduled for a repeat at full load rather than carried forward as clean.
The template
The template, field by field
The form exactly as it installs. Every field, option, score and conditional rule is editable, and the links to other templates come with it.
3 sections
- Reference
- MNT-033
- Archetype
- Record
- Record ID
- THERM-2026-000
- Scoring
- Severity band
- Direction
- High is bad
- Singleton
- No
- Basis
- NFPA 70B
- Links
- Links Asset; feeds Work Order
- Tags
- Maintenance, Condition monitoring
- Sections
- 3
- Fields
- 47
- Follow up fields
- 4
- Repeating sections
- 1
- Links out
- 4
Header
19 fieldsRecord ID*
Auto sequence. Format THERM-2026-000.
The record's own ID. Other templates point at this value.
Status*
Drives who this goes to next.
- Planned2 pts
- In progress2 pts
- Complete3 pts
- Deferred0 pts
- Open0 pts
- Closed3 pts
- Overdue0 pts
Date and Time*
Raised By*
Site*
Site ID*
Format SITE-000.
Links to FDN-001 Site ID
Area
The area within the site.
Exact Location
Drop a pin for anything hard to find.
Asset*
Asset ID*
Format AST-0000.
Links to FDN-002 Asset ID
Survey Type*
Routine route, baseline, diagnostic follow up or post repair verification.
Analyst*
Analyst Certified*
- Yes3 pts
- Trainee supervised1 pt
- No0 pts
Equipment Running Normally*
Readings taken under abnormal load or speed are not comparable with the baseline.
- Yes3 pts
- Partly1 pt
- No0 pts
Load Condition
Baseline Available*
- Yes3 pts
- No0 pts
Ambient Temperature C
Emissivity Setting
Load At Time Of Survey*
Electrical thermography under light load misses faults. Survey at 40 percent load or better.
- Above 40 percent3 pts
- Below 40 percent0 pts
Thermal anomalies
Repeats11 fieldsLocation*
Component*
Measured Temperature C*
Reference Temperature C
Delta T*
Severity Classification*
Delta T above 40 degrees on a similar component is usually immediate action.
- Under 10 degrees, monitor3 pts
- 10 to 20 degrees, plan repair2 pts
- 20 to 40 degrees, repair soon1 pt
- Over 40 degrees, immediate0 pts
Thermal Image*
Visible Light Image
Probable Cause
Loose connection, overload, imbalance, corrosion or failing component.
Safety Risk*
- None4 pts
- Low3 pts
- Medium1 pt
- High0 pts
Immediate Action Taken
Assessment
17 fieldsOverall Severity*
- Normal4 pts
- Watch3 pts
- Alert1 pt
- Alarm0 pts
Trend Versus Baseline*
- Stable3 pts
- Slight increase2 pts
- Clear increase0 pts
Rate Of Change*
A high but stable reading is different from a moderate reading climbing fast.
- Stable3 pts
- Slow2 pts
- Rapid0 pts
Estimated Time To Failure
- Over 12 months4 pts
- 6 to 12 months3 pts
- 1 to 6 months1 pt
- Under a month0 pts
Recommended Action*
- Continue monitoring3 pts
- Increase monitoring frequency2 pts
- Plan corrective work1 pt
- Immediate action0 pts
Recommended By Date
Work Order Raised*
- Yes3 pts
- Not needed3 pts
- No0 pts
Work Order ID
Links to MNT-002 Work Order ID
Next Survey Due*
Action Required*
Raise the action record, then enter its reference here.
- No2 pts
- Yes0 pts
Priority
- High0 pts
- Medium1 pt
- Low3 pts
CAPA ID
Format CAPA-2026-00000.
Links to FDN-014 CAPA ID
Action Owner
Thermographer*
Signature*
Reliability*
Second Signature*
MNT-033 · record IDs look like THERM-2026-000 · Links Asset; feeds Work Order
Open in KnowellaRun it with agents
From a document you fill in to a programme that runs itself
The image is easy. What fails is the surrounding judgement: the load nobody recorded, the safety-risk finding that waited for the next review, and the point never compared against its own history.
Holds the survey library against the asset register, flags surveys missing a load record, and routes each finding to its owner with the linked work order.
Connects thermographer certification to the images taken, so a trainee-supervised finding is visibly distinct from a certified classification.
Escalates a High safety-risk finding into the safety workflow immediately, rather than letting it wait behind the delta-T band it sits in.
Rolls survey completion, overdue points and open findings into one view, and holds every write for approval before it touches a record.
This template lives in KnowMaintain — asset maintenance. Work orders, planned maintenance, calibration, reliability and shutdowns.
Meet KnowMaintain→Glossary
Thermographic Survey definitions and key terms
- Delta T
- The temperature difference between a measured point and a comparable reference, used to classify severity rather than absolute temperature.
- Emissivity
- A surface property affecting how accurately an infrared camera reads temperature; must be set correctly for the material surveyed rather than left at a default.
- Load at time of survey
- The current or output level the equipment carried during the survey; below-threshold readings understate a developing fault.
- Thermographer
- The person taking and interpreting infrared images, typically certified to a defined competency level for the equipment surveyed.
- Thermal anomaly
- A point reading materially hotter than a comparable reference or its own history, the finding unit the survey records.
FAQ
Frequently asked questions about thermographic survey
Why compare delta-T instead of an absolute temperature?+
The same absolute reading can be normal on one component and a developing failure on another, depending on ambient conditions, load and the component's own baseline. Delta-T against a comparable reference is what makes the classification meaningful.
Why does load matter to a thermographic reading?+
Heating at a connection or motor rises with the current it carries, so a survey done at low load understates a fault that would show clearly at full duty. Surveys below roughly 40 percent load should be flagged rather than trended as comparable.
How urgent is a high delta-T finding?+
Anything over 40 degrees on a similar component is usually immediate. A high safety-risk finding, typically a hot current-carrying connection, should be escalated as immediate regardless of the delta-T band, because it is a fire and arc-flash precursor.
Who is qualified to carry out a thermographic survey?+
A certified thermographer, working under representative load. A trainee's image should be recorded as supervised rather than given the same confidence as a certified classification.
How often should thermography be carried out?+
Yearly as a baseline interval, and more often on critical assets or where a previous survey raised a Watch or Alert. A change in load pattern or duty is also a reason to re-check a point sooner than scheduled.
Why keep the thermal image rather than just the number?+
A delta-T figure alone cannot be re-examined if the classification is queried later, or the point needs re-locating on site. The image, and ideally a matching visible-light image, is what makes a genuine year-on-year comparison possible.
Keep going
Related templates and programmes
Industries this is written for
Programmes this belongs to
Used together in Asset Inspection and Statutory Examination
Asset Condition Inspection
Assesses the general condition of an asset against defined criteria
Vibration Analysis Record
Records vibration readings taken from rotating equipment
Oil Analysis Record
Records laboratory analysis of lubricating oil, covering wear metals, contamination and additive condition
Ultrasonic Inspection Record
Records ultrasonic readings used to find air leaks, electrical discharge and early bearing wear
Pressure Vessel Inspection
Checks pressure vessels and their safety devices for corrosion, damage and correct operation
Crane and Hoist Inspection
Checks cranes, hoists and their controls for wear, function and load rating
More in Asset Inspections
Asset Condition Inspection
Assesses the general condition of an asset against defined criteria
Vibration Analysis Record
Records vibration readings taken from rotating equipment
Oil Analysis Record
Records laboratory analysis of lubricating oil, covering wear metals, contamination and additive condition
Ultrasonic Inspection Record
Records ultrasonic readings used to find air leaks, electrical discharge and early bearing wear
Pressure Vessel Inspection
Checks pressure vessels and their safety devices for corrosion, damage and correct operation
Crane and Hoist Inspection
Checks cranes, hoists and their controls for wear, function and load rating
Written and reviewed by
Siddarth Singh
Founder & Chief Executive Officer, Knowella
Certified Safety Professional and industrial and systems engineer with more than a decade inside food supply chain, freight and manufacturing operations. This page was written against the current text of the standards it cites, not against secondary summaries of them.
- Certified Safety Professional (CSP), Board of Certified Safety Professionals
- MBA, University of Chicago Booth School of Business
- MS and BS, The Ohio State University, Industrial and Systems Engineering
- Six Sigma Black Belt
Sources and last review. Reviewed 16 August 2026 against:
- NFPA 70B, Recommended Practice for Electrical Equipment Maintenance
- NFPA 70E, Standard for Electrical Safety in the Workplace, arc-flash precautions for live surveying
- ISO 18434-1, condition monitoring and diagnostics of machines — thermography, general procedures
- ISO 55001, asset management systems — requirements
This page is general guidance, not legal advice. Confirm requirements with your jurisdiction’s regulator.