ASME B16.5 · Standard reference
ASME B16.5-2025: what changed from the 2020 edition
ASME B16.5-2025 is the current edition of the American pipe-flange and flanged-fitting standard, covering NPS ½ through NPS 24 in Classes 150 to 1500 (Class 2500 runs to NPS 12). It is a revision of ASME B16.5-2020: the B16 Standards Committee and ASME approved it, ANSI approved it as an American National Standard on 10 April 2025, and it was issued on 30 May 2025. The next edition is scheduled for publication in 2028.
The 2025 edition is not a reprint with a new cover. Its Summary of Changes records revised pressure–temperature ratings across the rating tables, additions to the material and bolting specification lists, a revised bore ('B') dimension and a revised minimum-hub-height method in the flange dimension tables, new threaded-flange figures, a new nonmandatory appendix on minimum temperature limits, and new definitions of may, shall and should. A drawing, datasheet or certificate that quotes 2017 or 2020 values therefore needs checking rather than assuming.
This page summarises those changes from the 2025 edition's own front matter — the Foreword, the Summary of Changes and the List of Changes in Record Number Order. The revised tables themselves are not reproduced here, so no 2025 rating, material or dimension values are asserted; read the current edition for those.
- Edition
- ASME B16.5-2025
- Supersedes
- ASME B16.5-2020
- Approved by ANSI
- 10 April 2025
- Date of issuance
- 30 May 2025
- Next edition
- 2028 (scheduled)
- Clauses and tables revised
- §1, §2, §5–§8; App. A, App. II, App. G
Summary of Changes: what the 2025 edition changed
The headline is that the 2025 edition makes technical changes, not just editorial ones. The pressure–temperature ratings were recalculated after the rating ceilings in Nonmandatory Appendix A changed; the material and bolting specification lists grew; the bore ('B') dimension and the minimum-hub-height rule in the dimension tables were revised; and the threaded-flange figures changed. Around those sit new definitions, new guidance, a new appendix and updated references.
The committee's margin note ([25]) flags every changed location, and each entry carries an ASME record number. The table below regroups the page-by-page entries into the subjects a buyer actually works with, keeping the record numbers so each line can be traced to the List of Changes in Record Number Order (printed p. xix). 'C' tables are the U.S. Customary companions of the SI tables.
B16.5 · ASME B16.5-2025
| Area | Section / table | What changed | Practical impact |
|---|---|---|---|
| Pressure–temperature ratings | Tables 2‑1.1 to 2‑3.19 (SI) and their C (U.S. Customary) companions | All rating tables revised (records 21‑1888, 22‑564, 23‑2509) | Allowable pressures were re-issued, not just re-typeset. Read 2025 values before reusing a 2020 or 2017 rating on a drawing or datasheet. |
| Pressure–temperature ratings | Nonmandatory Appendix A — Tables A‑1 and A‑2 (rating ceiling pressures) | Ceiling pressures revised (record 22‑2110); tables also revised under 21‑1888 | The ceilings the p/T tables are built on changed. This is the mechanism behind the Foreword's statement that ratings were revised after adopting new ceiling values. |
| Pressure–temperature ratings | Table 2‑2.13 and Table 2‑2.13C (new) | Added for Material Group 2.13, duplex materials (records 21‑1888, 23‑2509) | Duplex stainless flanges now have a dedicated rating table. Check the grade against Group 2.13 rather than an adjacent group. |
| Pressure–temperature ratings | Tables 2‑2.10C and 2‑2.12C | At 1 000 °F, working pressure for Classes 400–2500 revised; Note (2) added (records 21‑1888, 23‑2509) | The 1 000 °F entries in those U.S. Customary tables moved. Hot-service designs that sit close to a limit need re-checking. |
| Pressure–temperature ratings | C rating tables generally — temperature columns and notes | First temperature entry under 'Temp., °F' revised in many C tables; metric temperatures in notes rounded to the nearest degree; notes revised and reordered (records 21‑1888, 22‑564, 23‑2509) | Do not assume the first row or the notes of a C table are identical to the 2020 printing. |
| Materials | Table 1.1‑1 — List of Material Specifications | Revised (records 16‑1229, 21‑1888, 23‑2509) | The master material list changed. Confirm the ASTM specification named on the purchase order is still listed for the intended material group. |
| Materials | Table 1.1‑1 — nickel-alloy Groups 3.1, 3.6 and 3.12 | Specifications for Groups 3.1 (35Ni‑35Fe‑20Cr‑Cb) and 3.12 (46Fe‑24Ni‑21Cr‑6Mo‑Cu‑N) corrected, and a second forging/plate specification added for Group 3.6 (33Ni‑42Fe‑21Cr), all by errata (record 21‑1145) | Some nickel-alloy entries were wrong or incomplete in the previous printing — re-check certificates and material test reports against the 2025 list. |
| Materials | Tables 1.1‑1, 2‑3.7, 2‑3.8 and 2‑3.12 to 2‑3.14, with their C companions | ASTM B462 and ASTM B564 forging specification materials added (record 16‑1229) | Two more nickel-alloy forging specifications are recognised in the material and rating tables, widening the supply options for nickel-alloy flanges. |
| Materials — bolting | Table 1.1‑2 — List of Bolting Specifications | ASTM A320 L7M added under intermediate-strength bolting; ASTM B511 (N08830), B572 (N06230) and B637 (N07740, N07718) added under nickel and special alloy (record 22‑651); notes revised, reordered and clarified (records 21‑1888, 21‑2211, 22‑651) | New bolt grades are now inside the standard, including low-temperature L7M and nickel-alloy grades. Re-read the notes before pairing bolts with a flange material. |
| Materials — bolting | Table 1.1‑2, Notes (6) and (11) | Wording of 'corresponding material' clarified (record 21‑2211) | Removes an ambiguity about which bolt material may be used with which flange material when the bolting is bought separately. |
| Dimensions — hub geometry | Figures 7 and 8; Tables 8, 11, 14, 16, 18, 20 and 22 (and their C companions) | Hub height H and a new Note (1) added to Figures 7 and 8; method for the minimum hub height revised (record 22‑2183) | Hub geometry was re-ruled, not just redrawn. Read hub and length-through-hub values from the 2025 edition rather than a 2020 drawing. |
| Dimensions — bore | Tables 8, 11, 14, 16, 18, 20 and 22 (and their C companions) | The 'B' dimension (the bore shown in the flange figures) revised for slip-on, socket-welding, welding-neck and lapped flanges (record 21‑579) | The inside diameter is a dimensioned value, not a note. Compare the 2025 table with any 2020 or 2017 bore dimension before accepting a part. |
| Dimensions — threaded flanges | Table 8 / 8C (Class 150) and Table 11 / 11C (Class 300) figures | Class 150 threaded figure now shows threads continuing to the flange face; Class 300 threaded figures now include a counterbore (record 23‑628) | Threaded-flange geometry changed — relevant when machining, gauging or inspecting threaded flanges. |
| Dimensions — errata corrections | Table 7 (Class 150 drilling templates) and Table 8 / 8C (Class 150 flanges) | NPS 20 outside diameter O corrected from 693 to 698; NPS 14 outside diameter O corrected from 553 to 533 (records 21‑1134, 21‑1133) | Two outside diameters printed in the 2020 edition were wrong. The 2025 figures (698 mm and 533 mm) are the ones to use. |
| Dimensions — errata corrections | Table 5 and Table 5C (ring-joint groove details) | Class 2500 NPS 2½ groove depth E corrected from 9.522 to 9.53; a dimensionless row under NPS 24 in Table 5C deleted and alignment corrected (records 21‑1372, 22‑1148) | Groove depth affects ring-joint gasket seating — verify the groove against the 2025 table. |
| Figures and editorial | Figures 1, 2 and 12 | General Note (b) revised in Figures 1 and 2 (record 22‑567); U.S. Customary values added to Figure 12 (record 21‑1122) | Clarifications rather than new requirements, but worth a fresh look if drawings or specifications quote those figures. |
| Definitions and wording | Clause 1.11 (new); Clauses 2.2, 5.3.5(a) and 6.1.1 | Definitions of may, shall and should added; 'must' changed to 'shall' and related sentences revised to match (record 22‑2279) | The clauses were reworded to match the new definitions rather than to change a value. Contract or specification wording that quotes the clause may differ. |
| Definitions and guidance | Clauses 2.4, 2.5.3, 5.1.2 and 5.3.4 | Guidance added; the last sentence of Clause 5.3.4 deleted (record 21‑1888) | Part of the same change record that added the General Notes in the rating and material tables and Nonmandatory Appendix G — read them together. |
| Testing | Clauses 2.6 and 8.1 | Requirements for system hydrostatic testing revised (record 21‑1849) | Check hydrostatic test pressures and procedures in inspection and test plans against the new wording. |
| Appendices | Nonmandatory Appendix G — Low Temperature Applications (new) | Added for determining minimum temperature limits for materials (record 21‑1888) | A new nonmandatory method for determining minimum design temperature, with a table of example minimum use temperatures. The appendix is not reproduced here; read it in the current edition. |
| Appendices | Mandatory Appendix II — References | References updated (record 23‑2265) | The reference standards cited by B16.5 moved on; update any reference list in a specification or QA system that tracks them. |
| Editorial | Titles of complementary SI / U.S. Customary table pairs; Clause 7.3 | Titles revised to state the applicable system of units (Summary of Changes introduction, printed p. xiv); Clause 7.3 editorially revised | Easier to tell SI from U.S. Customary tables. No technical effect. |
Grouped summary of the committee's change list, not a verbatim copy. Record numbers are ASME change-record numbers. Values of the revised tables are not reproduced here because the revised rating, material and dimension tables are not reproduced here.
The Foreword's own summary of the 2025 revision
The Foreword ends with the committee's own short list of what the 2025 edition added. The Foreword (p. 11) records that various ASTM materials, a new appendix for determining minimum temperature limits, and definitions for may, shall and should were added; that the pressure–temperature ratings were revised after revised ceiling values were adopted in Nonmandatory Appendix A, Tables A‑1 and A‑2; and that various other revisions to variables were made. The same page states that ANSI approved ASME B16.5-2025 on 10 April 2025.
Read against the record-number list, that short paragraph resolves into the following:
- Materials: 'various ASTM materials' added. The record list names ASTM B462 and B564 forgings (16‑1229), and bolting specifications A320 L7M, B511, B572 and B637 (22‑651).
- Minimum temperature: a new appendix — Nonmandatory Appendix G, Low Temperature Applications — added for determining minimum temperature limits, with supporting guidance in the temperature and materials clauses (21‑1888).
- Definitions: may, shall and should defined in new Clause 1.11, with Clauses 2.2, 5.3.5(a) and 6.1.1 aligned to the definitions (22‑2279).
- Ratings: the pressure–temperature ratings revised after the ceiling pressures in Nonmandatory Appendix A, Tables A‑1 and A‑2 were revised (22‑2110), followed through into every rating table (23‑2509 and others). This is the headline change for buyers.
- Variables: 'various revisions to variables' is the Foreword's catch-all and is not itemised there; the Summary of Changes and the record-number list are the detail behind it.
- Dates: ANSI approval 10 April 2025; date of issuance 30 May 2025; next edition scheduled for 2028 (pp. 3 and 11).
What this means for a 2017 or 2020 drawing or datasheet
Not every line in the Summary of Changes affects what is bought. But several do, and they are worth a deliberate check rather than a quick glance at the cover.
- Ratings: re-read the allowable pressure for each size, class, material group and design temperature from the 2025 tables. Do not carry over 2017 or 2020 numbers.
- Materials and bolting: confirm that the ASTM specification named on the certificate appears in the 2025 Table 1.1‑1 or 1.1‑2 — especially nickel-alloy Groups 3.1, 3.6 and 3.12, and the newly added L7M and nickel-alloy bolts.
- Geometry: re-check the B (bore) dimension, hub dimensions and minimum hub height in Tables 8 to 22, plus the threaded-flange figures, before machining or inspecting.
- Installed equipment: the 2025 edition's §1.3 continues to recognise earlier-edition ratings for components already installed in accordance with them, except where a code or regulation governs. The edition named on the purchase order remains the reference an inspector will use.
- Paperwork: update datasheets, ITPs and reference lists to 'ASME B16.5-2025'. On a purchase order, state the year — '2025' — not 'current edition'.
What this page covers, and what it does not
This page is based on the 2025 edition's front matter: the cover and title pages, the copyright page and contents (PDF pp. 1–4), the Foreword (PDF pp. 9–11), the committee roster and correspondence (PDF pp. 12–13), the Summary of Changes (PDF pp. 15–19), the List of Changes in Record Number Order (PDF p. 20) and printed page 1 of the standard text (PDF p. 22). Printed page 1 of the standard is PDF page 22, so printed and PDF page numbers differ from that point onward.
It does not contain the revised pressure–temperature tables, the material and bolting tables, the dimension tables and figures, or Nonmandatory Appendix G. This page therefore describes what changed and why it matters, but reproduces no 2025 rating, material or dimensional value. For those, use the purchased ASME B16.5-2025 edition; where a purchase specification names an edition, that edition governs.
Where the committee's own text leaves a point open — for example the 'various revisions to variables' in the Foreword — we say so rather than guess.
ASME B16.5 edition changes — questions
Do I need to re-check ratings when moving from B16.5-2020 to B16.5-2025?
Yes. The 2025 edition revised the pressure–temperature ratings in Tables 2‑1.1 through 2‑3.19 (and the C tables) after the rating ceilings in Nonmandatory Appendix A, Tables A‑1 and A‑2 changed. Any allowable pressure taken from a 2020 or 2017 table should be re-read from the 2025 edition before it is used in a design, datasheet or quotation. The revised tables are not reproduced here, so this page does not list the new values.
Did the flange dimensions change in 2025?
Yes, in places. The Summary of Changes records a revised 'B' (bore) dimension for slip-on, socket-welding, welding-neck and lapped flanges, a revised minimum-hub-height method with hub height H added to Figures 7 and 8, new threaded-flange figures (threads to the face on Class 150; a counterbore on Class 300), and errata corrections to individual values — NPS 14 outside diameter 553 to 533, NPS 20 outside diameter 693 to 698, and the Class 2500 NPS 2½ ring-joint groove depth 9.522 to 9.53. The 2025 edition should not be treated as purely editorial; the revised tables are needed for the new values.
What are the new minimum-temperature limits?
The 2025 edition adds a nonmandatory appendix for determining minimum temperature limits — Nonmandatory Appendix G, Low Temperature Applications — and adds guidance in Clauses 2.4, 2.5.3, 5.1.2 and 5.3.4. The Foreword and the record list describe it as a determination method, and the contents also list a table of example minimum use temperatures. Neither the appendix nor that table is reproduced here, so we cannot quote limits here; use the current edition to establish the minimum temperature for the specific material and grade.
Which materials were added or removed?
The Summary of Changes records additions and errata corrections, but no material removals. Added: ASTM B462 and ASTM B564 forging specifications; bolting specifications ASTM A320 L7M, ASTM B511 (N08830), ASTM B572 (N06230) and ASTM B637 (N07740 and N07718); and a new rating table (2‑2.13 / 2‑2.13C) for Material Group 2.13 duplex materials. Some nickel-alloy specification entries were also corrected by errata. The full lists are in the current edition.