ASME B31.3 Process Piping

ASME B31.3 is the process piping code covering chemical plants, petroleum refineries, and similar process facilities, defining fluid service categories (Category D, Normal Fluid Service, Category M, High Pressure, Elevated Temperature) each with specific NDT requirements.

Definition

B31.3 is the most widely used piping code in the chemical, petrochemical, and refining industries. NDT extent ranges from visual only (Category D) to 100% RT or UT (Category M and High Pressure).

What this document is

The ASME code for process piping — design, materials, fabrication, examination and testing of piping in refineries, chemical plants and related facilities.

How it is applied

Its fluid-service categories set examination extent: Normal, Category D, Category M and High Pressure each carry different radiography percentages and acceptance criteria. The examination standard is Section V; the acceptance criteria are B31.3's own.

The common misuse

Applying the 100% radiography expectations of severe cyclic service to normal fluid service, or vice versa. Examination extent is a service classification decision made by engineering, not by the inspector at the weld.

Where ASME B31.3 Process Piping fits in an inspection programme

A term is only useful when it connects to a decision. ASME B31.3 Process Piping appears in written procedures, in technique sheets, and in the records an owner or accreditation body reviews afterwards — which means the way it is defined in your documentation has to match the way it is applied on site. Where the two drift apart, audits find it. Atlantis writes and reviews procedures against the governing codes, trains inspection personnel to apply them, and builds the record-keeping that makes the evidence retrievable years later. Procedure development and code consulting · NDT training and certification · Ask us about your programme.

Related terms

ASME B31.1 Power Piping — ASME B31.1 is the power piping code covering design, fabrication, installation, NDT, examination, and testing of piping in electric power generating stations, industrial plants, and central and district heating plants.
ASME B31.4 Liquid Pipelines — ASME B31.4 is the code for transportation of liquids by pipelines, including crude oil, refined petroleum products, liquid alcohols, ammonia, and CO2, defining weld NDT requirements integrated with API 1104.
ASME B31.8 Gas Transmission and Distribution Piping — ASME B31.8 is the code for gas transmission and distribution piping systems, including pipelines and onshore station piping, defining NDT, hydrostatic testing, and integrity management for natural gas service.
API 570 Piping Inspection Code — API 570 is the inspection, repair, alteration, and rerating code for in-service piping systems in refineries and chemical plants, defining inspection intervals based on piping class and corrosion rate, and requiring API 570 inspector certification.

More standard terms

ASME Section V · ASME Section VIII · ASME Section IX · ASME Section XI · API 510 Pressure Vessel Inspection Code · API 571 Damage Mechanisms · API 579-1 / ASME FFS-1 Fitness-for-Service · API 580 Risk-Based Inspection · API 581 Risk-Based Inspection Methodology · API 650 Welded Tanks for Oil Storage

Where this comes up in practice

Terms like this one appear in three places that matter commercially: the written practice that governs how your personnel are qualified, the procedures and technique sheets that define how an examination is actually performed, and the evidence an auditor or client asks for when they want to know why an inspection was accepted. Getting the terminology right is the easy part; being able to produce the qualification record, the calibration traceability and the procedure revision that applied on the day of the inspection is the part that decides audits.

Atlantis NDT provides NDT training and certification against ASNT SNT-TC-1A and ISO 9712, ASNT Level III consulting for written practices and procedure approval, inspection management software that holds qualification, calibration and procedure-revision evidence in recoverable form, and an asset integrity platform that binds inspection results to the asset they describe. Browse the full NDT glossary or ask a Level III directly.