Brackets play a crucial role in the support of pressure equipment such as heat exchangers, pressure vessels, and piping systems. Their primary function is to maintain stability, distribute loads, and prevent structural failure due to static and dynamic forces. In this article, usage of brackets in pressure vessel design is examined, and particularly the design and verification of brackets in adherence to established engineering standards, including TEMA (Tubular Exchanger Manufacturers Association), AD 2000, EN 13445, and WRC (Welding Research Council) guidelines.
Design Considerations for Brackets
The design of brackets supporting pressure equipment must account for all the above factors:
•Load Conditions: Dead weight, pressure, wind, and seismic forces.
•Material Selection: Compatibility with pressure equipment to withstand temperatures and corrosion.
•Stress Analysis: Ensuring the bracket and the vessel can withstand mechanical stresses
In search of the most suitable procedure in pressure vessel codes and engineering manuals, all of the above factors need to be addressed.
Examine the Verification Methods for Brackets
There are engineering manuals, such as the “Denis R. Moss” manual, that provide guidance on bracket design, as well as codes like PD 5500 that reference bracket verification. However, these resources offer only limited coverage on the subject. The methods that best address bracket verification are the following:
WRC Method
WRC analysis is used to evaluate the local stresses of the bracket-to-shell junction, and it is a commonly acknowledged method. Specifically, WRC Bulletins 107 and 537 provide analytical techniques for assessing localized stresses at attachment points. These methods help determine whether the stresses remain within permissible limits, reducing the risk of fatigue failure. WRC is widely applied in pressure vessel and heat exchanger design to assess stress concentration and potential failure points. However WRC analysis does not verify the bracket ribs and base plate. So WRC needs to be used along another method to fully validate the bracket support.
AD 2000 Approach
AD 2000, a German pressure vessel standard, incorporates the WRC analysis but refines it to suit static equipment applications more effectively. It takes into account various load cases, including internal pressure, external forces, and moments, ensuring a comprehensive verification of bracket integrity (including verification of the ribs, base plates and anchor bolts). This method provides detailed guidelines on stress assessment and load-bearing capacity making it well-suited for industrial applications.
EN 13445 Method
EN 13445, the European standard for unfired pressure vessels, presents a methodology for bracket verification. However, one major drawback is that its formulas do not explicitly include pressure, which is a critical factor in pressure vessel analysis. This omission raises concerns about the accuracy and applicability of EN 13445 for comprehensive bracket verification. Engineers often complement EN 13445 with additional stress analysis methods, such as WRC, to address these limitations.
TEMA Method
TEMA provides specific guidelines for evaluating brackets used in thermal exchangers. It outlines methods for determining the structural integrity of support brackets under operational loads, including thermal expansion and mechanical forces. TEMA standards, when used alongside WRC analysis, offer a robust approach to bracket verification, ensuring that the brackets can withstand various operating conditions without excessive deformation or failure.
Conclusion
Having analyzed all of the methodologies above, the most complete in all aspects of design—including local load verification, bracket verification, and considerations of various load cases—is the AD 2000 method. This approach provides a comprehensive framework for ensuring the structural integrity of brackets in pressure equipment by integrating stress analysis, load case evaluations, and fatigue resistance criteria. Furthermore, new software VCLAVIS.com, has been developed to support the AD 2000 approach, enhancing the efficiency and accuracy of bracket verification in engineering applications.
