In February 2026, suppliers linked to the Strait of Hormuz provided 59.1% of Malaysia’s crude imports. Between March and July that share fell to 32.3%, while African suppliers rose to 35.6% from 19.6% (The Star, citing Phillip Capital Research). In Indonesia, meanwhile, Pertamina inaugurated its upgraded Balikpapan refinery in January and lifted capacity from 260,000 to 360,000 barrels per day (Hydrocarbon Engineering).
Engineers classified, sized and tested the piping in refineries like these against assumptions they fixed years earlier. ASME B31.3 governs how they make those decisions. However, it does not say when the assumptions expire, and that gap, more than any calculation error, decides process piping integrity. Owners who keep that link current are best placed for what comes next, from tighter inspection regimes to new feedstocks.
What Is ASME B31.3? ASME B31.3 is the ASME Process Piping Code. It sets requirements for materials and components, design, fabrication, assembly, erection, examination, inspection and testing of piping in petroleum refineries, chemical, pharmaceutical, hydrogen, power generation and cryogenic plants, and related processing plants and terminals (ASME). At present, ASME lists the 2024 edition as current. |
Key Takeaways
|
ASME B31.3 at a Glance
| Applies to | Piping for process fluids in refineries, chemical, hydrogen, power generation, cryogenic and related plants and terminals (ASME). |
| Lifecycle covered | Materials and components, design, fabrication, assembly, erection, examination, inspection and testing. |
| Fluid service | Normal by default, Category D for lower hazard, Category M for very hazardous service. The owner makes the selection (Peng Engineering). High-pressure piping has its own chapter (Becht). |
| Current edition | ASME issued B31.3-2024 in December 2024 (Becht; ASME). |
| Revision cycle | Biennial since the 2004 edition (CSA Group). |
| Outside its scope | In-service inspection, rating and repair, which fall to separate standards such as API 570 and, in Indonesia, to Permen ESDM 32/2021 (ESDM). |
| Related training: B31.3 sits alongside other design codes in a plant. For pressure vessels and gas transmission pipelines, see EnergyEdge’s ASME BPVC Section VIII, Division 1 course (30 November–2 December 2026) and Gas Transmission Pipeline Engineering course (2–4 December 2026), both in Kuala Lumpur. |
Fluid Service and the Owner’s Role
The code leaves its most consequential early decision to the owner. The code treats all fluid services as Normal unless the owner designates Category D, for lower hazard, or Category M, which covers extremely hazardous services (Peng Engineering). That choice drives examination extent, joint selection and the test regime. The same commentary also notes that many hazardous services still sit under Normal. Owners may apply more stringent requirements voluntarily, as many do for hydrofluoric acid.
In practice, teams write the decision into piping classes and specifications, so the quality of those documents largely determines outcomes. ASME frames careful application of the B31 series as a way to help users comply with local regulation, not a substitute for it (ASME).
| Illustrative scenario, not a specific incident. Designers specify a crude transfer line for a lighter, low-acidity crude with a 3 mm corrosion allowance and classify it as Normal Fluid Service. Years later, the refinery moves to a heavier, more corrosive cargo mix. The drawings do not change, and the line still complies with the code as built. However, the first sign that the allowance no longer holds is a thickness reading, not a revision to the design basis. |
ASME B31.3 Design Rules: Where Judgement Concentrates
Pressure design is arithmetic. The judgement lies in the inputs. Required thickness adds mechanical, corrosion and erosion allowances to the pressure design thickness, but the allowance is the designer’s assumption about future service, and the code cannot verify it. When feed composition, throughput or temperature shifts, the assumption erodes quietly while the drawing still shows a compliant line.
Flexibility is a second concentration point. The code lets designers set formal analysis aside for systems that duplicate proven service or that engineers can judge adequate by inspection. Those provisions suit stable duties, yet they invite over-reliance when tie-ins, added loads or revised operating cases alter a system without triggering fresh review.
Vibration is the third. B31.3 requires designers to arrange and support piping to avoid harmful vibration but offers no screening method. For that reason, the Energy Institute’s guidelines on vibration-induced fatigue in process pipework serve as the working reference for small-bore connections and lines near compressors. Failures of this kind often sit outside static stress reports, because those reports do not model the excitation source.
| Related training: for the calculations behind these decisions, including pressure loss, thickness, flexibility, nozzle loads and support selection, see EnergyEdge’s ASME B31.3 Process Piping Systems in Industrial Plants course (intermediate level, 3 days, 16–18 December 2026, Kuala Lumpur). |
What Changed in the 2024 Edition, and What It Asks of Owners
Construction generates the records on which every later inspection decision depends. Weld examination, material verification and leak test results define what crews actually built, and they become the reference for judging thickness readings for decades. The 2024 edition adjusts this phase. First, owners may now disassemble and reassemble mechanical joints that passed a leak test without a further leak test, which extends a concession that previously covered only flanged joints and certain threaded and tubing connections. Second, the edition removes the requirement to examine branch connection fitting-to-header welds by radiography or ultrasonics in Category M service. Third, default sustained stress indices now refer to ASME B31J (Becht).
Each change is defensible on engineering grounds, yet each shifts verification onto owner procedures: the first assumes disciplined bolting control, the second more weight on supplementary examination, the third on stress methods that keep evolving. As a result, the code text alone no longer settles what “compliant” means on a given site.
Handover is where good records pay off. B31.3 is a design and construction code, and in-service programmes work best when they start from construction data rather than assumptions. For example, a 2017 release on a North Sea platform shows why interfaces deserve clear ownership: a temporary carbon steel spool due for removal in 2010 stayed in service for seven years, then failed, releasing 200kg of gas and 1,550kg of crude oil. The operator received a £560,000 fine in November 2025, and HSE pointed duty holders to management of change for temporary spools and their removal (HSE).
| Related training: because the 2024 changes place more weight on owner procedures, teams can arrange programmes around their own piping classes and specifications. EnergyEdge offers in-house and customised training for energy-sector teams. |
Indonesia: Inspection Rules Now Depend on Construction Records
Balikpapan shows the scale at which owners apply the code: the upgrade raised the refinery’s complexity index from 3.7 to 8 (Petromindo), and the piping it contains becomes a baseline for a tightening regulatory regime.
Ministerial Regulation 32/2021 consolidates earlier inspection and pipeline safety rules and covers design review, technical inspection, risk analysis, reverse engineering and residual life assessment (Ministry of Energy and Mineral Resources). The Directorate General also states that new, existing and beyond-design-life installations all require inspection (Ditjen Migas), and in May 2026 it reviewed progress on operating-fitness approvals (Persetujuan Layak Operasi) under the regulation (Ditjen Migas). Reverse engineering and life assessment are only as credible as the design basis behind them, so gaps in B31.3 records become a regulatory question, not only an engineering one.
| Related training: for teams working on inspection planning, residual life assessment and life extension, see EnergyEdge’s Asset Integrity and Life Extension course, which covers risk-based inspection and fitness-for-service methodologies (5 days, 7–11 December 2026, Kuala Lumpur). |
Malaysia: A Crude Slate That Changed Within Months
The shift in import sources described at the start means Malaysian refiners have been processing a different mix of crudes within months. The wider region also faced the same adjustment, as refiners managed changes in yields, fouling, crude compatibility and contaminants such as mercury in condensates (Becht).
No piping failure is implied. The point is structural: corrosion allowances, materials and inspection intervals that engineers chose for one crude slate may now face another, and no clause in B31.3 triggers a review when the slate moves. Therefore, that trigger has to sit in owner specifications and management-of-change procedures. On the statutory side, public descriptions of DOSH requirements centre on boilers and unfired pressure vessels (LRQA), so owners should confirm with DOSH or an approved inspection body whether the requirements apply to process piping.
| Related training: for current public course dates and venues across EnergyEdge’s technical programmes, see the EnergyEdge training calendar. |
Where B31.3 Projects Most Often Go Off Course, and How Teams Stay on Track
| Common pitfall | Why it happens | Typical consequence | What good practice looks like |
|---|---|---|---|
| One-time fluid service classification | Teams treat classification as a project deliverable, not a living decision. | Examination and test levels drift from the duty. | Revisit classification at management of change and when service conditions shift. |
| Fixed corrosion allowance | Engineers size it against the original feed envelope and rarely retest it against new streams. | Wall loss can outrun the inspection plan. | Test allowances against new streams and feed results into inspection intervals. |
| Flexibility exemption after modification | “Proven service” logic survives tie-ins and added loads. | Displacement stresses and nozzle loads go unchecked. | Re-run the check whenever tie-ins, loads or operating cases change. |
| Temporary or interface piping without a clear owner | It sits outside normal management of change and inspection scope. | Exposure concentrates where responsibility is unclear. | Assign a named owner and a tracked removal date. |
| Construction records missing from the inspection baseline | Teams archive handover packages instead of building them into inspection plans. | Life assessment starts from assumptions, not data. | Build handover data into the inspection baseline from day one. |
What to Expect Next
Edition control and design-basis traceability will matter more than the interpretation of any single clause, particularly as ASME B31J and later code changes reach owner specifications. Meanwhile, Indonesian reverse engineering and residual life requirements will expose gaps in legacy records, so owners with older piping should expect to reconstruct design bases.
Feedstock diversification is likely to persist while energy security stays high on regional policy agendas, making corrosion allowance review a routine operating decision. In addition, new services, including hydrogen, which falls within B31.3’s stated scope, will test fluid service decisions further.
Overall, compliance with B31.3 is the starting point. Teams that keep design assumptions current, owned and recorded are likely to be best placed for tighter inspection regimes, changing feedstocks and new services, and that discipline is what turns a compliant asset into a dependable one.
Turning the Discipline into Routine Practice
Keeping assumptions current is less a technology question than a capability one. It depends on design engineers, project teams and integrity engineers sharing a working view of how design basis, construction records and inspection decisions connect, and teams usually build that view through a mix of site experience and structured learning.
EnergyEdge supports this through public courses on its training calendar and in-house programmes that fit a team’s own piping classes and specifications. The courses below cover the topics discussed in this article.
Courses Covering These Topics
7–11 DEC 2026 · KUALA LUMPUR Asset Integrity and Life Extension Risk-based inspection and fitness-for-service methodologies. |
16–18 DEC 2026 · KUALA LUMPUR ASME B31.3 Process Piping Systems in Industrial Plants Thickness calculation, flexibility and stress fundamentals, supports and piping layout. |
30 NOV–2 DEC 2026 · KUALA LUMPUR ASME BPVC Section VIII, Division 1: Pressure Vessels Design and Construction Design rules and compliance for pressure vessels. |
2–4 DEC 2026 · KUALA LUMPUR Gas Transmission Pipeline Engineering Design excellence and operational safety for gas transmission systems. |
See current course dates and venues on the EnergyEdge training calendar.
ASME B31.3 FAQs
ASME B31.3 is the ASME Process Piping Code. It sets requirements for piping in petroleum refineries, chemical, pharmaceutical, hydrogen, power generation and cryogenic plants. It also covers related processing plants and terminals. Specifically, the code addresses materials, design, fabrication, assembly, erection, examination, inspection and testing.
The code treats fluid service as Normal unless the owner designates otherwise. However, owners can select Category D for lower-hazard service or Category M for extremely hazardous service. Category M adds further requirements. Separately, the code covers high-pressure piping in its own chapter. Ultimately, the owner’s choice of category drives examination, joint selection and testing requirements.
The 2024 edition made several notable changes. First, default sustained stress indices now refer to ASME B31J. Second, the code relaxes re-testing for leak-tested mechanical joints that crews disassemble and reassemble. Third, it removes the radiography or ultrasonic examination requirement for certain Category M branch connection welds. In addition, the edition adds press-connect fittings and API 623 globe valves to the listed components.
ASME has published the code on a biennial cycle since the 2004 edition. Currently, ASME lists the 2024 edition as current. Therefore, confirm the latest edition with ASME before you issue or update specifications.
ASME describes B31.3 as a companion to B31.1. B31.1 covers power piping, whereas B31.3 covers process piping in refineries, chemical plants and related facilities. In short, the two codes serve different types of facilities.
No. B31.3 is a design and construction code. Instead, separate standards such as API 570 and local regulation typically govern in-service inspection. For example, Permen ESDM 32/2021 sets technical inspection requirements for oil and gas installations in Indonesia. In Malaysia, confirm with DOSH or an approved inspection body whether statutory requirements apply to process piping.
Yes. EnergyEdge runs the ASME B31.3 Process Piping Systems in Industrial Plants course. This 3-day intermediate programme covers pressure loss, thickness calculation, flexibility, nozzle loads and support selection. Additionally, EnergyEdge can arrange in-house programmes for company teams.
