EN 13445 code is the European standard for the design and construction of unfired pressure vessels, ensuring safety and performance through rigorous material selection, design calculations, and testing procedures. While the code provides a comprehensive framework for choosing materials that meet specific safety criteria, there are instances dictated by pressure vessel design requirements, when ASME materials are used in conjunction with this code – specifically under the Particular Material Appraisal (PMA) process.
How Using ASME Materials in EN 13445 is Possible (via PMA)
The Particular Material Appraisal (PMA) process is a key mechanism within EN 13445 that allows materials not explicitly covered by the standard to be used in static equipment design. This process is essential when a material doesn’t have a direct European equivalent or when its properties are not fully specified in EN 13445.
Materials specified under ASME codes (American Society of Mechanical Engineers) can be incorporated into the EN 13445 design through PMA by performing a thorough appraisal of their mechanical properties, such as yield strength, tensile strength, elongation, impact toughness, and fatigue resistance. The material’s suitability is then verified against the design requirements specified in the EN 13445 code, including safety factors and allowable stresses.
The PMA process includes:
• Reviewing Material Properties: The properties of the ASME material (e.g., those specified under ASME II-D) are evaluated, including yield strength, tensile strength, and other mechanical characteristics.
• Adjusting for Safety: The material’s allowable stresses and safety factors are assessed, ensuring the material can withstand the intended pressure, temperature, and environmental conditions.
• Confirmation of Compliance: The material is then appraised to ensure it complies with the relevant design requirements of EN 13445, ensuring the overall integrity of the pressure vessel.
Reasons Why Using ASME Materials Under PMA is Common
• Material Availability: ASME materials are widely available across the globe, especially in industries such as petrochemicals, oil and gas, and power generation. In many cases, these materials are already in use in existing designs, and their properties are well-documented. If a specific ASME material is not covered in EN 13445, it is often quicker and easier to perform a PMA rather than sourcing a material with an EN certification.
• Global Standards: ASME codes and materials are globally recognized, and pressure vessels designed using ASME materials often need to be evaluated according to EN 13445 to meet European market or regulatory requirements. The PMA process provides a structured means to incorporate globally available materials into European designs.
• Conservative Safety Margins: ASME materials are often more conservative in their allowable stress values and other design parameters. This is particularly beneficial in high-risk applications, where additional safety margins may be needed. For example, ASME materials may offer conservative values for yield strength, which increases the overall reliability of the pressure vessel.
• Lack of European Equivalent: Some materials that are commonly used in industries outside of Europe might not have an equivalent listed in EN 13445. In such cases, ASME materials are often chosen due to their broad usage and well-established material properties. The PMA process makes it possible to use these materials by evaluating their suitability and compliance with EN 13445’s safety requirements.
Challenges with Incorporating Non-ASME Materials in EN 13445
While ASME materials can be incorporated into EN 13445 through the PMA process, the incorporation of non-ASME materials presents significant challenges. Here are some of the main difficulties:
• Limited Documentation and Testing: Non-ASME materials may not come with the same level of detailed testing or documentation, particularly in terms of mechanical properties such as impact toughness, fatigue resistance, and long-term performance. This lack of documentation makes it difficult to confidently assess their suitability for pressure vessel applications under EN 13445.
• Difficulty in Verification and Certification: The certification processes for non-ASME materials may not be as widely recognized or accepted in Europe. As a result, additional verification, independent testing, or certification may be necessary, which can add time and cost to the project.
• Lack of Familiarity: Engineers and designers working with European codes may not be familiar with the specific properties of non-ASME materials, particularly those from lesser-known standards. This lack of familiarity can lead to challenges in performing the necessary design calculations, such as determining the allowable stress, fatigue limits, or other critical factors.
Use of Software to Incorporate ASME Materials into EN 13445 Design
One of the challenges engineers face when working with ASME materials under EN 13445 is the need for precise and accurate calculations. Fortunately, pressure vessel analysis software has evolved to help simplify this process. One such software is VCLAVIS.com, which supports the use of ASME materials in EN 13445 code calculations.
Conclusion
Incorporating ASME materials into EN 13445 pressure equipment designs under the PMA process is a practical and effective approach when materials are not explicitly listed in the EN 13445 code. This process is typically driven by factors such as material availability, global standards, and the conservative safety margins provided by ASME materials. On the other hand, using non-ASME materials presents significant challenges, including limited documentation, inconsistent material properties, and difficulty in certification.
Today, there are modern software that make the process of using ASME materials in EN 13445 designs more accessible by enabling engineers to access material property data from ASME II-D tables, applying these properties to obtain the necessary allowable stresses for compliant and safe designs.
