12.3 RT Procedures, Codes, and Viewing Practice

Topics 4 and 5 tell you what a dark mark can be and how not to irradiate the night shift. This section is how a procedure turns that knowledge into a radiograph someone else can defend. The ASNT NDT Level II specific exam (General Industry or Pressure Equipment) spends codes, applications, and techniques items here: can you read a technique sheet, view the image the way the document requires, and know whether you are allowed to interpret yet? The general paper assumes the same discipline. A beautiful indication on an illegal film is not an examination.

A procedure is the controlling work instruction for a product family. A technique sheet (or technique card, reader sheet setup, or exposure chart line) is the filled-in instance for this thickness, this source, this geometry. ASTM practices, ASME Section V, Article 2, and a construction code can all be invoked. They are not interchangeable, and none of them is an ASNT-published accept/reject table for every weld.

Essential variables on the technique sheet

An essential variable is a setting that, if changed beyond the allowed range, can change detectability or make the image non-comparable to the qualified technique. Industry RT procedures and the ASME Section V technique article treat at least the following as locked. Learn the list; the specific exam prints a subset and asks what you may not freelance.

Related locks the procedure may also treat as essential: geometric-unsharpness limit, collimator use, intensifying-screen type, processing chemistry or scanner settings, and the viewing setup. If the document lists it as essential, the Level II does not “improve” it on the pad. Changing source family, kV band, detector system, SFD, or IQI placement outside the allowed range is a different examination. That change belongs to the Level III or the owner who approves revisions.

If a stem prints 220 kV, 36 in SFD, and a source-side IQI, those printed numbers win for that item. Shop habit (“we always put the IQI on the cassette”) loses.

Marking, identification, and location markers

A radiograph is evidence. Evidence needs a name and a map.

Identification that industry procedures and ASME Section V-style articles expect in the image (lead figures, flash cards, or digital annotation the procedure allows) typically includes a unique job or weld number, the date, the manufacturer or contractor identity, and enough of the part identity that the film cannot be swapped with a neighbor. Identification written only on a paper jacket or a folder tab is not in the radiograph. If the image is the record, the image must carry the ID.

Location markers (lead arrows, numbered belts, clock-position markers) tie a density change to a place on the part. Pipe and vessel work uses a marker system so a slag line at “marker 4” can be found with a tape. A double-wall exposure needs markers that still make the reader’s clock unambiguous. Missing markers are not a paperwork nuisance. They are a coverage and traceability failure.

Image-quality indicators sit on the source side when the procedure requires source-side placement, unless a documented film-side exception applies (limited access). The required hole or wire must be visible in the area of interest at the required density. A beautiful IQI on a shim next to the weld, when the procedure wanted it on the weld, is the wrong demonstration.

Other marks that belong in the image when the procedure says so: a thickness or IQI shim identity, “R” for a repair radiograph, and shooter's letters that do not hide the area of interest. Markers that cover the fusion zone are a reshoot, not a creative composition.

Viewing film: illuminator and a subdued room

Interpretation does not happen under a skylight with a phone flashlight. Film viewing conditions are part of the examination.

Subdued room lighting cuts glare and stops the eye from adapting to a bright wall instead of the film. ASME Section V and the invoked procedure require viewing facilities that let you see the required density range. A viewer that is fine for density 1.8 and collapses at density 3.5 is not adequate for the high end of the window.

Illuminator intensity must be enough to transmit light through the area of interest at the actual density. High-density film needs a high-intensity viewer. Mask the film so stray light does not flood around the edges. Industry technique articles (ASME Section V, Article 2 is the usual ASME citation) also require a densitometer check of the IQI body and the area of interest against the allowed window. A commonly taught ASME Section V single-film window is 1.8–4.0 for X-ray and 2.0–4.0 for gamma — attribute those numbers to ASME Section V, Article 2, not to ASNT. If the stem prints a different window, the stem wins.

Viewing practice the exam expects:

• Let your eyes adapt in the subdued room before you call a faint linear mark “nothing.”
• View the area of interest, not only the IQI corner.
• Use magnification if the procedure allows it for fine linear indications.
• Do not interpret wet film as final unless the procedure has a documented wet-view step and a dry confirmation.
• A scratch, a static tree, a processing streak, or a light leak that interferes with the area of interest is an artifact problem, not a weld discontinuity. Chapter 11 owns artifact names; this section owns the decision: can I interpret, or must I reshoot?

Digital viewing: window and level

Computed radiography and digital detector arrays do not have a single “film density” you hold up to a bulb. They have a recorded pixel-value range and a display you can move. Window is the span of values you spread across the gray scale (contrast). Level is the center of that span (brightness). Together they are the digital equivalent of choosing how hard to stare through a film — with a dangerous extra power: you can clip data out of the display.

Correct digital viewing:

• Confirm the examination quality first (IQI, required SNR or contrast sensitivity, coverage, identification) using the procedure's digital criteria, not using a pretty monitor preset.
• Adjust window and level to inspect the area of interest, including the root, the cap, and the fusion faces the shot was meant to see.
• Look at more than one window if a single setting hides either a light tungsten speck or a dark pore cluster.
• Do not window a weld into a uniform mid-gray that erases porosity and then report “no indications.”
• Do not treat window/level as a substitute for a reshoot when the detector saturated, the plate was under-exposed, or the IQI is absent.

Monitor cleanliness, ambient light, and a calibrated grayscale matter the same way a dirty illuminator matters. A sunlit trailer and a glossy laptop are not a viewing room.

ASME Section V versus the construction code

Mixing these jobs is the expensive codes mistake on both papers.

ASME Section V is a referenced technique section. The referencing construction code (for pressure equipment, often Section VIII or a B31 book) says when Section V applies and which discontinuities of which length fail. AWS D1.1 and API 1104 bring their own RT acceptance. A Level II who rejects a pore because “Section V doesn’t like porosity” has cited the wrong book. A Level II who accepts a crack because “the film density was 2.2, so Section V is happy” has confused technique compliance with acceptance.

The Level II applies the approved procedure and the named acceptance standard. The Level III or the owner writes or approves those documents. The specific exam is a procedure-reading test: apply the printed paragraph.

When to reshoot versus when to interpret

Interpretation is the last act, not the first. Use this gate. If the image fails the technique, you do not then “see what the weld looks like anyway.”

Reshoot (or otherwise obtain a valid image — a documented additional exposure, a different wall, a repaired cassette) when any of these is true:

• Required identification is missing from the image or is unreadable.
• Location markers do not establish coverage or clock position.
• IQI type, placement, or essential hole/wire fails.
• Density (film) or SNR / contrast sensitivity (digital) is outside the procedure window in the area of interest.
• Geometric unsharpness or motion blur exceeds the limit.
• Coverage is incomplete — a root, a bevel face, or a required overlap is off the detector.
• An artifact (processing streak, light leak, crimp, dirty plate, damaged detector line) interferes with the area of interest.
• The wrong technique was used (wrong isotope, wrong wall shot, film-side IQI when source-side was required and no exception applies).

Interpret only after the image is a valid examination. Then classify what you see using topic 3 and 4 language (discontinuity versus geometry versus artifact), measure as the acceptance standard requires, and apply the construction code or specification named in the procedure. A valid film with a slag line is not a reshoot because you dislike slag. A valid film with a crack-like line is not a reshoot because you hope a second shot will smear it.

Borderline cases the exam likes:

• Density is in range and the IQI is visible, but a processing streak crosses the fusion zone → reshoot that view; do not interpret through the streak.
• Density is in range, markers and IQI are good, and you see clustered porosity → interpret against the rounded-indication table. Do not reshoot hoping the pores will migrate.
• Digital image meets SNR, but a single aggressive window hides the root → re-window and view; that is viewing practice, not a reshoot, unless the recorded data themselves are clipped.
• Film-side IQI was used because the source side was inaccessible and the procedure allows the exception with a documented sensitivity demonstration → interpret if that demonstration is on the image. If the procedure did not allow the exception → reshoot or obtain a Level III disposition before you call the weld.

What the Level II actually reports

A complete RT report, as procedures typically require, records the procedure and technique identity, source and detector data, IQI and density/SNR results, identification, views, discontinuities located against markers, sizes in the code's language (rounded, linear, elongated), and disposition (accept, reject, or repair as the referencing document uses those words). Sketches or digital frames go with the report when the procedure asks. “Looks OK” is not a disposition.

The general exam will ask whether you know which book does which job and whether a listed essential variable is yours to change. The specific exam will hand you a paragraph and a weld and ask you to do what the paragraph says. In both cases the order is the same: run the sheet, mark the image, view it under the required conditions, reshoot what is invalid, and only then apply acceptance.

A Level II who interprets first and checks the IQI later is not faster. That Level II is signing a technique that may not have happened.