GN 012.29 - Ductile Fracture of Stainless Steel Stiffener Butt Weld in Cryogenic Vessel
- Details
- Category: Use & In-Service Inspection
| APEK - AICIP GUIDANCE NOTE |
SIGNS OR INDICATIONS IN IN-SERVICE DUCTILE FRACTURE OF STAINLESS STEEL STIFFENER BUTT WELD IN CRYOGENIC VESSEL |
APEK GN 012.29 Rev 0 |
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1 Figure |
 |
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2 PE involved |
Cold stretched cryogenic stainless steel (304) vessel. |
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3 Sign(s) |
Crack – full length in butt weld. |
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4 Location of Signs |
Circumferential stainless steel stiffener (100mm high). |
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5 When & Where occurred |
In 1990s in Australia, during cold stretching hydro test Pt = 3MPa; T = 20oC. |
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6 Detection & Investigation |
Suspect noise, shake and external shape (not circular). |
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7 Failure mode(s) (damage mechanisms) |
Overload rupture. Ductile tearing and fracture. |
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8 Most probable causes |
Defective weld: lack of centreline weld penetration; incomplete weld at stress raiser (drain hole); and at stress above proof strength (Rp) Manufacturers tend to treat attachments as minor. |
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9 Outcome |
Delayed and costly fabrication; loss of reputation. |
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10 Most Possible Prevention |
Change practice with such welds; RT quality weld; dressed and PT weld end especially with cold stretched vessels. |
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11 Comment |
Shows valve of VT in ____ after pressure test to defect internal damage – especially with new designs, procedures and manufacturers. |
SAA