Dear Mr. Elavarasan,
Plate to Pipe Qualification: A welder qualified on a plate is qualified to weld on pipe, but there are diameter and position restrictions
Pipes of OD 24 and 26 inches, are well above 73 mm, so diameter is not a restricting factor for your case.
For your 25 mm plate: The qual. range is 12.5 to 50 mm for production welds (with impact testing).
24-inch pipe (9.5 mm wall): Not qualified, as the wall thickness is less than the minimum qualified thickness of 12.5 mm.
26-inch pipe (14 mm wall) : Qualified, as the wall thickness is within the qualified range.
8 mm wall thickness pipe: Not qualified, as it is below the minimum qualified thickness.
Welder Qualification (WQT): The same thickness rules apply to the welder as to the procedure, unless the welder was qualified
on pipe directly, in which case the thickness and diameter ranges may differ.
If you need to weld pipes with wall thickness less than 12.5 mm (such as 8 mm or 9.5 mm), you must
requalify the procedure and welder for that thickness range.
Conclusion:
You cannot use the current plate WPS and WQT to weld a 24-inch pipe with 9.5 mm wall thickness or any pipe with 8 mm wall thickness.
You can use them for a 26-inch pipe with 14 mm wall thickness.
To weld thinner pipes (8 mm, 9.5 mm), you must qualify a new WPS and WQT for those thicknesses.
Both 9.5 mm and 14 mm pipes generally require impact testing (as per ASTM A333/A333M-15 and other standards, especially
if impact properties are specified in the material grade or project specifications specify impact toughness as a mandatory property.
References:
ASME Section IX, Table QW-451.1 and QW-452
Welder qualification diameter and thickness ranges.
Hope it is clear.
rgds,
C Sridhar.
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