变更摘要：2025 版改了什么
要点是：2025 版作了技术性修改，不只是编辑性修改。非强制性附录 A 中的额定值上限改变后，压力-温度额定值重新计算；材料与紧固件规范清单扩充；尺寸表中的内径（B）尺寸和最小轮毂高度规则修订；螺纹法兰图也有变化。此外还有新定义、新指南、新附录和更新的引用文件。
委员会的页边注（[25]）标出每一处改动，每个条目都带 ASME 记录编号。下表按买方实际工作的主题重新归类逐页条目，并保留记录编号，使每行都能追溯到按记录编号排列的变更清单（印刷页 xix）。带 C 的表是 SI 表的美制对应表。
| 领域 | 条款／表 | 变更内容 | 实际影响 |
|---|---|---|---|
| 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. |
委员会变更清单的分组概述，不是逐字照录。记录编号为 ASME 的变更记录号。本页不重复修订后的额定值、材料与尺寸表，因此也不给出其数值。