This post covers the Radiography Testing or RT acceptance criteria for the ASME Section IX (9). If you refer the ASME Section 9 code, the RT acceptance criteria is covered by Clause QW 191.1: Radiographic Examination & briefed in QW-191.1.2.2 Sub-clause.
QW191.1 covers the RT method and further sub-clause covers RT requirements as follow:
QW 191.1.2 RT acceptance criteria.
QW 191.1.2.1 RT defects terminology
QW 191.1.2.2 RT acceptance criteria for Welder Performance Qualification.
Note: This RT acceptance criteria is applicable only for Welder Performance Qualification and not for the actual production welding joints.
For production welding, you have to refer the RT acceptance criteria in the construction code, for example- ASME B31.3 or ASME Section VIII Division 1.
ASME Section IX: RT acceptance criteria is more stringent than the construction codes RT acceptance as Section IX is for performance qualification of welder and require to test the welders skills.
ASME Section IX Code RT (Radiography Testing) Acceptance Criteria
This acceptance criteria is applicable for Welder/ operator qualifications who carry out the test using test coupon welding or production test coupon welding (QW304.1 & 305.1).
RT acceptance criteria for Welder performance qualification is covered and explained in ASME Section 9 (IX) clause QW 191.1.2.2 and applies as follow:
Linear Indications
Welding Defect Type
Acceptance Criteria
Crack
Not acceptable
Incomplete Fusion
Not acceptable
Incomplete penetration
Not acceptable
Slag inclusions
For material thickness (t) up to 3/8 inches (10 mm), maximum slag inclusion of 1/8-inch (3mm) is acceptable. More than 1/8 inch shall be rejected
Slag inclusions
For material thickness (t) > 3/8-inch (10 mm) to 2.25 inches (57 mm), maximum slag inclusion of 1/3t is acceptable.
Slag inclusions
For material thickness (t) >2.25 inches (57 mm), maximum slag inclusion of ¾ inches (19 mm) is acceptable
1/8-inch (3 mm) maximum or 20% of material thickness (t), whichever is smaller.
Rounded indications: For material less than 1/8-inch (3 mm) thickness (t)
Maximum nos. of rounded indications shall not be more than
Table- 2
For an illustrative explanation of Rounded indications acceptance in ASME Section IX, it covered by figure QW-191.1.2.2 (b) (4).
This figure explains the rounded indications (usually welding porosity) distribution based on their quantity and maximum permitted size as estimation guide for different material thicknesses.
Summary of RT Acceptance as per ASME Section IX
A summary of welding defects acceptance based on RT acceptance as per ASME Section IX is given below:
Welding cracks of any type are not permitted.
Incomplete Welding Fusion is not permitted.
Incomplete weld penetration is not permitted.
Slag inclusion permitted within the tolerances given in Table 1.
Welding porosity (any type) is permitted within the tolerance given in Table-2.
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