APEK - GN 012.53 - Weld Root Reinforcement and Overlap

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GN 012.53 - Weld Root Reinforcement and Overlap

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GN 012.53 - Weld Root Reinforcement and Overlap

Details: Category: Use & In-Service Inspection

APEK - AICIP
GUIDANCE NOTE

SIGNS OR INDICATIONS IN IN-SERVICE
INSPECTION OF PE

WELD ROOT REINFORCEMENT AND OVERLAP

APEK GN 012.53
Case 53

Rev 1
Issued: 03/07/2015

1 Figure
2 PE involved	New vertical oil separator – Carbon steel, Class 3 pressure vessel 9mm thick, 500mm OD. Imported ASME VIII-1 ŋ=70% ie no NDT.
3 Sign(s)	Root penetration (2.5mm continuous); overlap (2mm – continuous, both sides); minor spatter from circumferential weld.
4 Location of Signs	Inside vessel on vertical weld.
5 When & Where occurred	Overseas; 2014.
6 Detection & Investigation	During commissioning inspection in Australia by VT using endoscope via 50mm nozzle. Various standards reviewed. A joggled joint with the equivalent of overlap is permitted for circumferential joints.
7 Failure mode(s) (damage mechanisms)	Failure to comply with AS 4037 ie Weld overlap is DNC (to AS4037). Overlap not referenced in ASME VIII-1 – inspector accepted. Reinforcement - ok.
8 Most probable causes	Poor fitting backing bar (eg Copper) for small diameter vessel.
9 Outcome	Investigation was required. Put into service without removal on basis: a) Complied with ASME b) For this application – corrosion is negligible c) Fatigue very unlikely – low cycles, low stress; and “crack” parallel to stress d) Urgently needed (Note 1 & 2)
10 Fix	No correction was required.
11 Possible Prevention	Better shaped backing bar, edge bending, or clamping.
12 Frequency	Rare (most inspectors did not recognise).
13 Lesson	.1 Although it may be DNC, consider if fit for service and the risk for the owner/user. .2 Different standards have different acceptance criteria.

Notes:

Overlap would not be acceptable for severe corrosion service or where hygiene is critical as for food or medical use.
Defect criteria may differ from the original code provided it is assessed, shown to be fit for the particular service, is documented and acceptable to the owner/user.

SA