AutoPIPE - Can AutoPIPE Vessel calculate and report allowable nozzle loads?

Question:

AutoPIPE Vessel Does Not Generate Comprehensive Allowable Nozzle Load Tables

Can AutoPIPE Vessel calculate and report allowable nozzle loads for a nozzle connection based on its geometry, material, reinforcement, and design code?

Overview:

Users may expect AutoPIPE Vessel to generate allowable nozzle load tables (Fx, Fy, Fz, FR, Mx, My, Mz, Mr) for inclusion in vessel fabrication drawings, datasheets, or documents issued to piping stress engineers. This article explains the current capabilities of AutoPIPE Vessel and the recommended workflow for nozzle load qualification.

Answer:

AutoPIPE Vessel is primarily designed to verify the nozzle load, not to calculate an allowable nozzle loads.

The software evaluates user-defined external loads and verifies whether the resulting local stresses satisfy the requirements of the selected design code (EN 13445, PD 5500, WRC 107/537, and others).

The analysis process is:

Applied Loads → Calculated Stresses → Code Compliance Verification

AutoPIPE Vessel performs local stress calculations and code compliance checks for the applied loads but does not automatically generate a comprehensive allowable nozzle load table suitable for fabrication drawings or mechanical datasheets.

Why Are Allowable Nozzle Loads Not Reported Directly?

Most nozzle design methodologies are based on the interaction of forces and moments rather than independent evaluation of individual load components.

As a result:

- - Nozzle capacity depends on the combined loading condition.
  - There is generally no unique allowable value for each individual force or moment component that is valid for all loading cases.
  - Acceptance is determined through code-defined interaction equations.

EN 13445-3 Example

For nozzle local load assessment according to EN 13445-3 Clause 16.5.5, AutoPIPE Vessel calculates individual allowable load parameters used in the code equations, such as:

- - Maximum allowable axial force (Fz,max)
  - Maximum allowable moment (Mx,max)
  - Maximum allowable moment (My,max)

These values represent individual load limits only and are not intended to be applied simultaneously.

Therefore, compliance is based on the combination of applied loads rather than any single allowable force or moment value.

PD 5500 Annex G

PD 5500 Annex G follows the same fundamental methodology as EN 13445 and evaluates nozzle qualification using interaction relationships between forces and moments. Published allowable values generally correspond to cases where other interacting loads are assumed to be zero.

Recommended Workflow

Bentley recommends the following approach:

1. 1. Obtain actual nozzle loads from the project specification / piping stress analysis.
  2. Apply the complete load combination in AutoPIPE Vessel.
  3. Perform the local nozzle load evaluation using the applicable design code.
  4. Review the calculated stresses and code compliance results.
  5. Assess the complete force and moment interaction as required by the design code.

Conclusion

AutoPIPE Vessel verifies nozzle loading conditions against code requirements but does not generate a comprehensive allowable nozzle load table for direct use on vessel drawings or datasheets.

While certain methods such as EN 13445 calculate individual allowable load parameters internally, the governing acceptance criteria are based on load interaction equations. Therefore, the recommended engineering practice is to evaluate the actual combined nozzle loads and verify compliance with the applicable design code.