Is fatigue calculation mandatory for a tank?

EN 14015 does not require fatigue verification in every case; when filling is frequent or your client requests it, we calculate it to EN 1993-1-9 and IIW.

We have been building the same design for decades with no failures.

Fatigue acts silently and may take years to appear. Documentary verification also protects the manufacturer against a potential civil liability claim.

Doesn't our inspection body (OCA) cover this?

The inspection body checks execution quality (welds, NDT tests); it does not issue a fatigue calculation report. The dossier provides that document.

Do you work with API 650?

Yes. For projects with clients requiring API 650, we calculate under that standard. The report is signed as a chartered industrial engineer, COIIAR n.º 2653; professional-body endorsement is issued on request.

AIXC-MAT-CS-002

Fatigue of the shell-to-bottom weld of a tank

Demonstration on generic geometry: tank shell-to-bottom joint with weld stress and fatigue with finite elements. (1/2) — Demonstration on generic geometry: tank shell-to-bottom joint with weld stress and fatigue with finite elements.

Demonstration on generic geometry: tank shell-to-bottom joint with weld stress and fatigue with finite elements. (2/2) — Demonstration on generic geometry: tank shell-to-bottom joint with weld stress and fatigue with finite elements.

Demonstration on generic geometry: tank nozzle with hot-spot stress at the weld with finite elements. (1/2) — Demonstration on generic geometry: tank nozzle with hot-spot stress at the weld with finite elements.

Demonstration on generic geometry: tank nozzle with hot-spot stress at the weld with finite elements. (2/2) — Demonstration on generic geometry: tank nozzle with hot-spot stress at the weld with finite elements.

Question: What hot-spot stress and fatigue life does the shell-to-bottom weld have under fill and empty cycles?
Method: Axisymmetric finite elements with finite elements on three meshes; hot-spot stress to IIW [3] and fatigue life with an S-N curve of the EN 1993-1-9 form [4].
Verify: 1.30 % change between the two finest meshes, within the 5 % criterion of the calculation; the shell is also checked against the Timoshenko and Woinowsky-Krieger cylindrical shell solution.
Result: Δσ_hs = 64.9 MPa at the outer shell weld toe; with 365 cycles a year and FAT 90, a characteristic life of 5.59·10⁶ cycles. Every figure is in the sample dossier AIXC-MAT-DS-001.
Limitations: Generic geometry of an S275JR water tank. The dossier is UNSIGNED until the signatory attests it.

Standards we work with

EN 14015We calculate to: vertical cylindrical welded steel tanks for liquids at ambient temperature
API 650We calculate to: storage tanks for projects with Anglo-Saxon or petrochemical clients
EN 1993-1-9 · IIWWe calculate to: fatigue of welded joints
ISO 3834We support your certification: quality requirements for fusion welding

Is fatigue calculation mandatory for a tank?
EN 14015 does not require fatigue verification in every case; when filling is frequent or your client requests it, we calculate it to EN 1993-1-9 and IIW.
We have been building the same design for decades with no failures.
Fatigue acts silently and may take years to appear. Documentary verification also protects the manufacturer against a potential civil liability claim.
Doesn't our inspection body (OCA) cover this?
The inspection body checks execution quality (welds, NDT tests); it does not issue a fatigue calculation report. The dossier provides that document.
Do you work with API 650?
Yes. For projects with clients requiring API 650, we calculate under that standard. The report is signed as a chartered industrial engineer, COIIAR n.º 2653; professional-body endorsement is issued on request.

Propose a case

Describe your materials question in an email: the load of a bulk material, the fatigue of a weld, the wear of a plate or a clay blend. We will tell you whether it can become a case study and with which data.

Write to info@aixcresearch.com