Design of Pressure Vessel using COMPRESS – Different Load Cases

A: Yes, COMPRESS can effectively design pressure vessels under external pressure loads. External pressure can cause buckling or collapse, which is different from internal pressure stress considerations. COMPRESS performs stability analysis to ensure that the vessel walls and components have adequate thickness and strength to resist buckling under vacuum or external pressure conditions. It follows the guidelines in ASME Section VIII, Division 2, or AD 2000 depending on user choice. Users input the external pressure conditions, and the software provides safety factors and checks to comply with the relevant codes.

A: Common mistakes include: incorrect input of load magnitudes or directions, neglecting to consider combined load scenarios, not specifying temperature effects properly, overlooking occasional or environmental loads like wind or seismic, and misuse of load case combinations contrary to code requirements. Additionally, not properly defining support conditions or ignoring weight of nozzles and attachments can lead to inaccurate results. To avoid these pitfalls, careful reading of the code and thorough training on COMPRESS software is recommended. Hexagon offers comprehensive tutorials and webinars covering these topics.

A: COMPRESS allows the user to define multiple load cases separately, such as internal pressure, weight loads, wind, seismic, and thermal loads. Each load case is analyzed individually for stresses and deformations. The software then can combine these load cases according to relevant design codes (e.g., ASME Section VIII Div.1 or Div.2) to evaluate the overall stress conditions. This combined stress assessment helps ensure that the vessel design meets safety and regulatory requirements under all possible operating scenarios. More on load combinations can be found at ASME code references and Hexagon's training materials.

A: Typical load cases include: internal pressure, external pressure (vacuum or hydrostatic pressure), weight of the vessel and contents (including supports), wind load, seismic (earthquake) load, thermal expansion or gradients, and occasionally occasional loads such as impact or operational loads like water hammer. Each of these load cases affects the vessel in different ways and must be analyzed either individually or in combination to comply with code requirements. COMPRESS facilitates this by allowing the definition and combination of these loads for a comprehensive structural analysis.

A: In COMPRESS, factors of safety are embedded within the code-based design criteria. Each load case or combination is evaluated against allowable stresses, which inherently include safety margins as specified by the design code (e.g., ASME Section VIII defines permissible stress limits with safety factors incorporated). The software calculates stress intensities and checks if they fall below allowable levels under all load cases and combinations, effectively applying safety factors during validation without manual input from the user. Users can view utilization ratios or margins of safety within COMPRESS reports for confidence in their design.

A: In COMPRESS, thermal loads are input by specifying temperature gradients or uniform temperature changes over the vessel's components. These temperature inputs generate thermal stresses due to expansion or contraction, which are considered alongside mechanical loads like pressure and weight. Typically, you enter the operating and ambient temperatures, or temperature differentials where applicable. The software then calculates the resulting thermal stresses and combines them with other load case stresses during the design verification. For an in-depth tutorial, see: https://hexagonppm.com/resources/webinars/thermal-stress-analysis

A: The first step is to define the geometry of the pressure vessel accurately in COMPRESS. This includes specifying dimensions such as diameter, length, thickness, and any nozzles or openings. After defining the geometry, you input the material properties. Once the vessel is modeled, you then set up different load cases, such as internal pressure, external pressure, wind load, seismic load, and thermal stresses. It is crucial to consider combined loading scenarios to ensure the vessel's integrity under real operating conditions. For detailed guidance, the COMPRESS user manual and Hexagon's official documentation provide step-by-step procedures: https://hexagonppm.com/products/pressure-vessel-design-software/COMPRESS

A: COMPRESS supports multiple widely recognized pressure vessel design codes including ASME Section VIII Division 1 & 2, PD 5500 (British code), EN 13445 (European code), and AD 2000 (German code). These codes govern how load cases should be considered, how stresses are calculated, safety factors, and acceptance criteria for pressure vessels. The software tailors its analysis and reporting according to the selected code to ensure compliance with national and international regulations. For complete details on code support, see: https://hexagonppm.com/products/pressure-vessel-design-software/COMPRESS/codes

A: Load case combinations in COMPRESS are managed using predefined or user-defined combination rules that follow relevant design codes. For pressure vessel design, codes like ASME Section VIII specify how different loads should be combined—for example, combining pressure with occasional loads like wind or seismic events. COMPRESS allows the user to select or create these combination cases, after which the software analyzes the combined stresses to verify the vessel's strength and stability. This ensures that the design is safe under all realistic operational scenarios. The documentation on load combinations is available within the software's help section and Hexagon's learning resources.