Standards, Specifications, and Procedures
Hierarchy
Understand the document chain: codes and standards (broad requirements, e.g., consensus standards) → specifications (detailed requirements for a particular product or contract) → procedures (how a specific organization will perform the test) → techniques/instructions (step-by-step for a specific job). A procedure must be qualified and often approved by a Level III; a technique is derived from the procedure.
What procedures contain
Scope, references, personnel requirements, equipment and calibration, surface preparation, test parameters (e.g., magnetization method, penetrant dwell, transducer frequency/angle, kV/mA/exposure), acceptance criteria reference, documentation and reporting, and safety.
Key distinctions
- Standard vs. specification: a standard tells you how to do something generally; a specification states requirements a product must meet.
- Procedure vs. technique: procedure is the general written method; technique is the specific application (geometry, parameters).
- Acceptance criteria belong in the specification or code, not invented by the technician.
Traps
- Questions that ask whether a technician may deviate from a procedure - generally no, without documented approval.
- Confusing calibration requirements with verification requirements.
- Assuming any published standard applies automatically; contract invocation matters.
Rule of thumb
If a question asks "where would you find the acceptance criteria," the answer is the specification or code, not the procedure.
Worked example
A technician wants to change penetrant dwell time to speed production. Correct action: do not deviate; the procedure governs, and changes require Level III approval and revision.
Materials, Fabrication, and Product Technology
Why it matters
Discontinuity types are predictable from material and process. Knowing how a part was made tells you what to look for and where.
Material classes
- Ferrous: carbon/low-alloy steels (MT applicable), stainless steels (austenitic grades are often nonmagnetic and coarse-grained, complicating MT and UT).
- Nonferrous: aluminum, titanium, copper alloys (ET applicable; MT not).
- Nonmetals: composites, ceramics, polymers (PT, UT, RT, IRT; not MT or ET).
Fabrication processes and typical discontinuities
- Casting: porosity, shrinkage, hot tears, inclusions.
- Welding: porosity, slag, lack of fusion, lack of penetration, undercut, cracks (hydrogen, solidification).
- Forging: laps, seams, bursts, forging cracks.
- Rolling: laminations, seams.
- Machining: cracks, tears, grinding burns.
- Composites: delamination, voids, fiber breakage, disbonds (UT, tap testing, IRT).
Traps
- Assuming all stainless steel is magnetic - austenitic grades generally are not.
- Forgetting that coarse grain in austenitic welds causes UT attenuation and noise.
- Confusing casting shrinkage with porosity in origin and shape.
Rule of thumb
Ask "how was this made?" to predict likely flaws: castings → volumetric; welds → planar and volumetric; forgings → surface and near-surface planar; composites → planar delamination.
Worked example
An austenitic stainless weld is difficult to inspect with UT due to grain scattering. Options include lower frequency, dual-element or focused transducers, or alternative methods such as RT. Best answer: account for grain structure and adjust technique.