Fatigue analysis is performed according to AD 2000-Merkblätter (03-2022) S 1.

Calculation Logic:

• Wall thickness (Se) affects calculations for Fd, 2Sigma*a, Nzul, and fatigue damage ratio under clauses 4.1, 4.2, and 4.4.
• Clause 4.3 provides an alternate formula that does not depend on wall thickness (Se) when Se ≤ 25 mm.
• AutoPIPE Vessel uses clause 4.3 when its conditions are met, so changing thickness within this range does not affect fatigue results.

Code Reference:

Avoidance:

To make thickness affect fatigue calculations:

• • Increase Se > 25 mm so clause 4.3 no longer applies.

Flowchart: Selection of Clause 4.3 for Load Cycle Determination

⬇️Step 1: Identify the component type.

• • Is it a pressure vessel?
    • No → Use general procedure (Clause 4.2).
    • Yes → Continue.

⬇️Step 2: Check if the component is welded.

• • No → Use Clause 4.2 (unwelded).
  • Yes → Continue.

⬇️Step 3: Verify temperature condition.

• • Is the load cycle temperature T* ≤ 100 °C?
    • No → Use Clause 4.2.
    • Yes → Continue.

⬇️Step 4: Check wall thickness (sₑ).

• • Is sₑ ≤ 25 mm?
    • No → Use Clause 4.2 (thickness correction in 4.1.3).
    • Yes → Continue.

⬇️Step 5: Check stress factor (η).

• • Is η ≤ 3.0?
    • No → Use Clause 4.2.
    • Yes → Continue.

⬇️✅ Apply Clause 4.3

Use equations (7) and (8) to determine allowable load cycles:

 

See Also

Bentley AutoPIPE Vessel

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