ASME B31.3 — Process Piping

Process piping code for petroleum, chemical, and pharmaceutical plants — design, materials, fabrication, examination, testing, and inspection requirements.

Scope

ASME B31.3 — Process Piping — is one of the four primary piping codes in the ASME B31 family (B31.1 Power Piping, B31.3 Process Piping, B31.4 Pipeline Transportation of Liquids, B31.8 Gas Transmission). B31.3 is the dominant code for piping in refineries, petrochemical plants, chemical plants, pharmaceutical plants, and similar process industries — encompassing the vast majority of API 570 in-service inspection scope. It covers piping design (allowable stress, wall thickness, support spacing), material selection, fabrication (welding, bending, branch connections), examination (RT, UT, MT, PT, VT), pressure testing, and quality assurance. B31.3 is published roughly every two years (latest editions 2022, 2024) and applies to construction-phase piping. API 570 covers in-service inspection of existing B31.3 piping. The code is structured: Chapter I (Scope, definitions), Chapter II (Design), Chapter III (Materials), Chapter IV (Standards for piping components), Chapter V (Fabrication, assembly, erection), Chapter VI (Examination, inspection, testing), Chapter VII (Nonmetallic piping), Chapter VIII (Severe cyclic conditions), Chapter IX (High-pressure piping), Chapter X (High-purity piping).

NDT methods it governs

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{"label":"Pipeline Integrity Inspection","href":"/blog/ndt-pipeline-integrity-inspection-guide"}
{"label":"Weld Inspection Methods","href":"/blog/weld-inspection-ndt-methods-guide"}
{"label":"Ultrasonic Testing (UT)","href":"/blog/ultrasonic-testing"}
{"label":"Radiographic Testing (RT)","href":"/blog/radiographic-testing"}

Certifications that reference it

{"label":"API 570 Piping Inspector Certification","href":"/api-570-certification"}

Issuing body

ASME

Revision history

2024 —
2022 —
2020 —
2018 —

Related standards

asme-section-v-article-2 · asme-section-v-article-4 · asme-section-v-article-7 · asme-section-v-article-9 · api-570 · api-1104 · aws-d1-1

Applying this in an inspection programme

Code compliance is only demonstrable if the evidence behind it is: the procedure revision in force, the inspector's certification state and the instrument's calibration status at the time of test. Atlantis NDT provides ASNT Level III consulting for procedure and written-practice work against this code, training toward the certifications that reference it, and inspection management software that keeps that evidence recoverable years later. Request a consultation.

How a standard like this is applied in an inspection programme

A standard is only half of the requirement. It defines how an examination is performed and, in some cases, how results are classified — but the acceptance criteria that decide whether a component stays in service normally come from the construction or in-service code governing the item, not from the examination standard itself. Confusing the two is one of the more common findings in a procedure review: a procedure that correctly cites the examination standard but applies acceptance criteria from the wrong code or the wrong edition.

What has to be in place for compliance to be demonstrable

A written procedure qualified against this standard for the specific materials, thickness ranges and geometries in scope — not a generic procedure covering everything
Personnel certified for the method and level under ASNT SNT-TC-1A, ANSI/ASNT CP-189, NAS 410 or ISO 9712, current on the date the examination was performed
Equipment, probes and reference standards in calibration on that date, with traceability to a national standard under ISO 17025
The applicable edition of the standard recorded against the examination, so historical work stays assessed under the edition then in force
Technique sheets under the same revision control as the procedure above them — the most frequently uncontrolled document in an otherwise compliant quality system

Edition changes

When a new edition is issued, new work moves to it from a defined effective date that you set and record; work already performed stays assessed under the edition in force at the time. Retrospectively applying a new edition to historical dispositions invalidates the original acceptance decision and creates a substantially larger problem than the one being solved.

Where this usually goes wrong

Not in the technical content, but in reconstruction. An auditor picks an issued report and asks which procedure revision applied, who performed the work and whether they were qualified on that date, and whether the instrument and reference blocks were in calibration. Programmes that hold only current state can answer none of those. Binding the document revision, the qualification state and the calibration state to each inspection record as it is created turns that from an investigation into a lookup.