Problem:

How AutoPIPE Vessel handles of Clause 9.7.2.4 (EN 13445-3:2021) for Nozzles Near De/10 in Dished Ends?

When a nozzle is located in the central region of a dished head (within De/10 from the edge as per Figure 9.5-4 of EN 13445-3), AutoPIPE Vessel limits the reinforcement calculation length ls to the De/10 boundary. AutoPIPE Vessel does not apply the second part of clause 9.7.2.4 that allows the use of the full value of ls, even when the limited reinforcement is insufficient.

This behaviour is by design and aligns with the software’s interpretation of the code requirements.

Solution:

Background:

Clause 9.7.2.4 of EN 13445-3:2021 Issue 1 states:

“In case the value of w limited as above is not sufficient to reinforce the opening, it is allowed to calculate the reinforcement taking into account the full value of ls, provided the thickness of the end complies with 7.7, considering the opening as encroaching into the knuckle region.”

Users may expect AutoPIPE Vessel to:

1. 1. 1. First calculate reinforcement using w limited by De/10
    2. Then, if reinforcement is insufficient, automatically recalculate using the full value of ls, provided clause 7.7 is satisfied

However, this is not how AutoPIPE Vessel currently operates.

AutoPIPE Vessel Procedure:

1. 1. Nozzle located within the central region (≤ De/10)
    - AutoPIPE Vessel applies clause 9.7.2.4 with:
      - wmin = 0
      - ls limited to the De/10 boundary
    - If reinforcement is insufficient, AutoPIPE Vessel does not switch to using the full value of ls.
  2. Effect of Other Nozzles on the Head (Bk factor)
    - If the nozzle is the only opening on the head, Bk = 1, and the head thickness is not increased.
    - If additional nozzles are present outside the central region, Bk ≠ 1, and the head thickness may increase accordingly.
  3. Clause 7.7 Thickness Check
    - Paragraph 7.7 applies to openings outside the central zone.
    - When an opening lies fully within the central area (radius 0.4De), the head thickness is not recalculated under 7.7.
    - Therefore, AutoPIPE Vessel cannot verify the prerequisite of clause 9.7.2.4 (“provided the thickness of the end complies with 7.7”).

Key Clarification from Bentley Development Team:

- - AutoPIPE Vessel always limits ls to the De/10 boundary for openings located in the central area of the head.
  - The software does not treat a centrally located opening as encroaching into the knuckle region, even if reinforcement with limited w is insufficient.
  - Using the full value of ls without a verified 7.7 thickness check could lead to non-conservative results.
  - The head thickness calculation cannot depend on the outcome of the opening reinforcement calculation.
  - As paragraph 7.7 only considers openings outside the central zone, AutoPIPE Vessel does not implement the second part of clause 9.7.2.4 for centrally located nozzles.

This behaviour is intentional and compliant with AutoPIPE Vessel’s code implementation logic.

Answer to Common User Question:

Question: Is there a way to “force” AutoPIPE Vessel to consider a centrally located nozzle as being in the knuckle region?

Answer: No. AutoPIPE Vessel does not provide a feature or option to force a nozzle located within the central area of the head to be treated as encroaching into the knuckle region. The software strictly determines nozzle location based on geometric position relative to De/10 and applies reinforcement rules accordingly.

EN 13445-3 Clause 9.7.2.4 – Use of ls When w Is Limited by De/10

Problem:

Solution: