Unfired pressure vessels - Part 3: Design; German and English version EN 13445-3:2014/prA15:2019 / Note: Date of issue 2019-04-05*Intended as an amendment to DIN EN 13445-3 (2018-12).
1Key Takeaways
This document is a draft amendment to European Standard EN 13445-3:2014/prA15:2019, concerning unfired pressure vessels, Part 3: Design. This draft amendment was prepared by CEN/TC 54 Technical Committee "Unfired Pressure Vessels," whose secretariat is managed by BSI (UK). The document is currently under public consult…
2Expert Interpretation
This article provides an in-depth analysis of the significant revisions to the draft EN 13445-3/A15 standard for the design of welds for unfired pressure vessels. The article focuses on the design specifications for welded joints, the limitations of the DBA-DR method, and the requirements for lamellar tearing protection. Detailed implementation guidance and a technical comparison table are also provided.
Background and Technical Evolution of the EN 13445-3/A15 Standard Revision
The draft EN 13445-3/A15 standard, released in April 2019, is a major supplementary revision to EN 13445-3:2014, primarily focusing on comprehensive updates to the welding design specifications for unfired pressure vessels. The draft was developed by Technical Committee CEN/TC 54, with the British Standards Institution (BSI) serving as the secretariat and the German Standards Committee for Chemical Plant Construction (FNCA) responsible for national standardization.
In-depth Analysis of Core Revisions
Section 9.4.7: Design Specifications for Shell-Connected Nozzles
The new standard includes a significant revision to the reinforcement design for welded nozzles: As long as the weld dimensions meet the requirements of Annex A, the nozzle cross-sectional area can always be used for opening reinforcement calculations. This revision eliminates uncertainty in the original standard and provides clearer guidance for engineering design.
| Design elements | Requirements before revision | Requirements after revision | Technical impact |
|---|---|---|---|
| Welding nozzle reinforcement | Conditionally permitted | Unconditionally permitted (in accordance with Appendix A) | Simplify the design process |
| Welding dimension requirements | Scattered in various chapters | Unified in Appendix A | Improve the consistency of standards |
Chapter 11.4.4: Technical requirements for flange manufacturing
The standard clearly distinguishes between two flange structures: clear hole flange with the flange aperture consistent with the shell aperture and step hole flange with fillet weld at the shell end. This distinction puts forward more precise requirements for the flange design and manufacture of pressure vessels.
Appendix A: Major updates to the design requirements for pressure welded joints
Classification and limitations of welded joints
The new version of Appendix A systematically specifies the design limitations of various types of welded joints through 9 detailed tables:
| Table number | Scope of application | Main limitations | Fatigue level |
|---|---|---|---|
| A.1 | Cylinder cone longitudinal weld | DBA-DR and creep design prohibition | Determined according to geometric shape |
| A.2 | Cylinder circumferential weld | Refer to Table 18-4 for specific requirements. | Class 40-63 |
| A.3 | Flat Head Welding | Lamellar Tearing Risk Control | Class 2.1-2.3 |
Application Limitations of the DBA-DR Method
The standard clearly defines the applicability limitations of the Direct Design Method (DBA-DR) for various welded joints, particularly for creep design conditions. These limitations are based on extensive engineering practice and failure case analysis to ensure design safety.
Technical requirements for lamellar tearing protection
The revised standard places special emphasis on the protective measures against lamellar tearing:
- Angle control: When the angle is less than 15°, there is a risk of lamellar tearing
- Material requirements: For key components such as tube sheets, forgings with Z quality grade are required
- Test verification: Tensile tests are required on samples taken from actual components
Technical implementation recommendations and engineering applications
Precautions in the design phase
During the design of pressure vessels, engineers need to:
- Strictly select the type of welded joint according to the table in Appendix A
- Fully consider the applicable limitations of the DBA-DR method
- Take preventive measures for joints with a risk of lamellar tearing
Manufacturing and inspection requirements
Based on the requirements of the new standard, the manufacturing process requires:
| Manufacturing process | New requirements | Quality control points |
|---|---|---|
| Material preparation | Z quality forgings | Material certification document review |
| Welding process | Comply with EN 1708-1 | Welding procedure qualification |
| Non-destructive testing | Internal visual inspection | Test coverage |
Standard evolution trends and future prospects
EN The revision of 13445-3/A15 reflects several important trends in the development of pressure vessel standards:
- International Harmonization: Maintaining consistency with the essential requirements of EU directives
- Technical Refinement: More detailed and clear classification of welded joints
- Safety Orientation: Strengthening the risk-assessment-based design approach
The release of this draft standard provides the pressure vessel industry with the latest technical specifications and is expected to have a profound impact on the design, manufacture, and inspection of related equipment. Engineering technicians need to stay abreast of these changes to ensure the correct application of the new technical requirements in design practice.