13.1 Parameter Verification and Coverage Review

Level II thermographers often review and sign work performed by Level I personnel. That is not a courtesy stamp. QA/QC means you verify that quantitative images were collected under valid radiometric assumptions, that the route was actually covered, and that incomplete work is labeled honestly. This section is the first gate: parameters and coverage. Severity reclassification and formal sign-off follow in 12.2 and 12.3.

Why Parameter QA Is Non-Negotiable

A Level I thermographer can capture a sharp image with good focus and still deliver wrong temperature if emissivity (ε), reflected apparent temperature (RAT), atmospheric temperature, relative humidity (RH), object distance, or window transmittance (τ) are wrong. Severity bands in Chapter 8 (NETA-style ΔT, absolute limits, ISO zones, ASHRAE envelope rules) inherit those numbers. If Level II accepts a Priority 1 finding built on ε = 0.95 on bare aluminum, the organization may de-energize for a reflection artifact—or, worse, accept a mild label on a truly hot joint measured with ε far too high.

Exam mindset: Level II does not assume the camera “knew” the truth. Metadata in the radiometric file (or documented field notes) is evidence. Missing notes = incomplete record.

Emissivity Checks on Level I Images

Open the image (or report table) and ask:

1. What is the actual surface? Painted enclosure, oxidized bus, shiny lug, ceramic insulator, steam-pipe lagging, wet roof membrane?
2. What ε did Level I enter? Does it match tables and Chapter 5 practice (high-ε nonmetals ~0.85–0.98; oxidized metals often mid-range; polished metals very low)?
3. Was a reference emitter used? Tape, paint, or high-ε sticker on the measurement point makes Level I ε choices defensible.
4. Is the spot on the intended material? A cursor on a shiny bolt head with ε set for painted steel is a dual error.

Worked idea: Level I reports a lug at 92 °C with ε = 0.95 on bright copper. After Level II applies reference-tape method (ε ≈ 0.95 on tape, then adjust metal ε / measure on tape), true surface temperature may drop substantially if the original reading was reflection-driven—or may rise if emissivity was set too high on a low-ε surface while RAT was mismanaged. Either way, priority cannot be finalized until ε and RAT are correct.

RAT and Atmosphere / Distance

RAT is the radiometric stand-in for energy reflected from the surroundings into the camera. Level II looks for:

• Documented RAT measurement (reflector method) near the work area
• Consistency: outdoor sun-loaded yards vs indoor MCC rooms need different RAT thinking
• Correlation with shiny targets: large RAT errors dominate low-ε surfaces

Atmospheric temperature, RH, and distance matter most for long paths, outdoor HV yards, and precision work through air columns. Short indoor shots at a few meters are less sensitive—but still require honest distance for IFOV/spot-size confidence (Chapter 6). Level II rejects “distance = 1.0 m” metadata when the photo clearly shows a camera at the aisle end of a 10 m lineup.

IR Window Transmittance (τ)

Many Level I electrical surveys use IR windows. Default τ = 1.00 through a window that is actually τ ≈ 0.5–0.9 (model-, dirt-, and age-dependent) understates true temperature rise on the far side when the camera is not corrected. Level II checks:

• Window ID / manufacturer data used for τ
• Cleanliness and inspection of the window itself
• Whether the report claims quantitative severity through a window without τ correction
• Whether a note says “qualitative only” when τ is unknown—acceptable if honest; unacceptable if Priority numbers pretend full accuracy

Coverage Review: Was the Route Actually Done?

Parameter perfection on half a plant is still a failed full survey if the scope promised complete coverage.

What to compare

Incomplete survey patterns

Critical language: Absence of a saved anomaly image is not proof the asset was inspected. QA requires a positive record (image, checklist tick with time, or documented N/A with reason—e.g., locked room, out of service).

Incomplete Surveys: How Level II Labels Them

When coverage or parameters fail QA:

1. Do not convert limited work into a clean bill of health for the full plant.
2. Issue a limited-scope or exception statement: what was done, what was skipped, why, and residual risk.
3. List open items with responsible party and target date for re-inspection.
4. Hold final severity on suspect images until parameters are corrected or re-shot.
5. Feed coaching notes to Level I (section 12.3) so the next route is complete.

Practical Parameter + Coverage Checklist (Level II)

Use this as a mental or paper checklist on every Level I package:

1. Spot-check ε on metals vs nonmetals and any tape references
2. Spot-check RAT method and value reasonableness
3. Confirm distance vs photo geometry; atmosphere for long paths
4. Confirm window τ when viewports used
5. Match image count and IDs to route list
6. Confirm load and ambient notes for quantitative electrical/mechanical calls
7. Flag any “all clear” without evidence of coverage
8. Document QA findings even when no thermal fault exists—process defects are still defects

Worked Review Scenarios

Scenario A — Default ε. Level I images a silver bus bar at ε = 0.95, RAT default, reports 18 °C ΔT Priority 3. Level II measures RAT with foil, applies proper ε / tape. Corrected ΔT may leave the Priority band or exit it. Hold Priority until corrected.

Scenario B — Window τ. Level I through IR window, τ left at 1.0, reports Priority 4 (8 °C). With manufacturer τ applied, ΔT becomes 22 °C → Priority 2 under this guide. Upgrade after parameter correction (12.2).

Scenario C — Missing gear. Scope: all MCC-1 through MCC-4. Package contains only MCC-1 and MCC-2. Level II signs only for completed MCCs and lists MCC-3/4 as not inspected.

Scenario D — Phantom completeness. Eighty panels claimed; fourteen IR files. Level II rejects “survey complete,” requires completion or written partial acceptance by the client.

Common Traps

Summary for Recall

Level II parameter QA verifies ε, RAT, atmosphere, RH, distance, and window τ against real surfaces and paths before trusting any Priority. Coverage QA compares scope + asset list + evidence set and refuses to treat missing equipment as healthy. Incomplete or uncorrectable work becomes limited scope with open items, not a silent pass. Only after this gate does reclassification (12.2) and supervisory sign-off (12.3) make professional sense.