7.1 Codes vs Standards vs Specifications

Four Terms, One Hierarchy

A Nondestructive Testing (NDT) Level III is expected to read a contract, trace it to the governing rules, and know which document wins when two disagree. Four terms sit at the center of that skill, and the Basic exam repeatedly tests whether you can keep them distinct. Field personnel use them loosely; a Level III cannot.

• Code — a body of mandatory rules that becomes legally or contractually enforceable once a jurisdiction, purchaser, or contract adopts it. Codes tell you what must be done and often how good the result must be. Examples: the ASME Boiler and Pressure Vessel Code (BPVC), AWS D1.1 Structural Welding Code — Steel, and the American Petroleum Institute (API) inspection codes (API 510 pressure vessels, API 570 piping, API 653 storage tanks, API 1104 pipeline welding).
• Standard — a consensus document that describes an accepted way to perform a method or test. Standards are how-to references and carry no force until a code, specification, or contract invokes them. The ASTM International E-series are the classic NDT standards, such as ASTM E165/E1417 for penetrant testing, E1444/E709 for magnetic particle, E94 for radiography, and E114/E164 for ultrasonics.
• Specification — a document that states the requirements a product, material, or service must meet. A specification is usually narrower than a code and is often written by the purchaser or a manufacturer (an in-house NDT spec, an Aerospace Material Specification (AMS), or a customer purchase-order spec).
• Procedure — the written instruction that tells the technician exactly how to perform the examination in your shop to satisfy the invoked code, standard, and specification.

Who Invokes Whom

These documents nest inside one another. A purchase order (the contract) invokes a construction code; the construction code invokes a method standard; the method standard may reference ASTM documents; and the employer writes a procedure that binds everything to real equipment and parts.

ASME Section V — the Method Book with No Acceptance Criteria

A heavily tested distinction: ASME BPVC Section V, "Nondestructive Examination," tells you HOW to perform each method but does NOT contain accept/reject criteria. Section V is organized into Articles — Article 1 general requirements, Article 2 radiography, Article 4 ultrasonics, Article 6 penetrant, Article 7 magnetic particle, Article 8 eddy current, Article 9 visual, and Article 10 leak testing. The acceptance criteria live in the referencing construction code — Section VIII Division 1 for pressure vessels, B31.1/B31.3 for piping — or in the AWS/API document that owns the scope. If an exam item asks where a rounded indication is judged acceptable, the answer is the construction or referencing code, never Section V by itself.

The Governing-Document Rule

Two rules decide conflicts. First, the document invoked by the job controls. Second, unless the job documents are formally changed, the edition invoked by the job governs — not the newest edition on the shelf and not local shop habit. If a purchase order invokes the 2023 edition of a code while the company manual cites a 2025 edition with different limits, acceptance is judged to the 2023 edition until the contract is revised.

When an internal procedure is broader (more permissive) than the invoked code or customer specification, the Level III applies the controlling stricter requirement and revises the internal procedure to align. A procedure can always be tighter than the code; it can never authorize acceptance the code prohibits.

Common Traps

• Treating a standard (ASTM) as mandatory when nothing has invoked it — it is a how-to until a code or contract calls it out.
• Reading acceptance criteria out of ASME Section V — Section V holds methods, not accept/reject limits.
• Applying the newest code edition because it is "current," when the job documents invoke an older edition.
• Letting shop habit or a company spec override an invoked code when the two conflict.

Standards-Developing Organizations at a Glance

Knowing who owns each document helps you predict what it can and cannot do. ASME and AWS publish construction and welding codes that carry acceptance criteria. ASTM International publishes consensus method standards (the E-series) and a few recommended practices and guides, which use non-mandatory language until invoked. API publishes in-service inspection codes for the oil and gas industry. ASNT publishes personnel-qualification documents (SNT-TC-1A, CP-189, CP-105) — those govern who is qualified, not weld acceptance. A single job routinely touches all four families at once.

Worked Example: Tracing the Chain

A fabricator receives a purchase order for a Section VIII pressure vessel. Follow the chain: the PO (contract) invokes ASME BPVC Section VIII, Division 1 and names an edition. Section VIII requires certain welds be radiographed and sends the method to ASME BPVC Section V, Article 2 for how to shoot the film. Section V, in turn, references ASTM documents for IQIs and film systems. Section VIII — not Section V — states whether the porosity or slag on that film is acceptable. Finally, the shop's written radiographic procedure, approved by the Level III, ties the whole chain to the actual X-ray equipment and technique. Miss any link and you either run the wrong technique or judge acceptance against the wrong document — both are exam-flagged errors.