(Refer: UW-51: Sub Para b (Page 148 and 149) and Mandatory Appendix 4 (Page 400 and Page 403) of ASME BPVC Section VIII Div 1, 2017 Edition.)
Following terminologies have been used to explain the acceptance/rejection criteria for Radiography Test (RT);
Linear Indication: Any indication with a length greater than three times the width. Linear indications are mainly cracks, lack of penetration, lack of fusion, and elongated slag inclusions.
Rounded Indication: Any indication with a length equal to or less than three times the width. A rounded indication may be circular, elliptical, conical, or irregular in shape and may have tails too. While determining the size of an indication, the tail shall also be included. Rounded indications may appear on radiographs from any imperfection in the weld, such as porosity, slag, or tungsten.
Acceptance criteria for Linear Indication (UW – 51):
1. Any crack, lack of penetration, and lack of fusion shall not be accepted
2. Any other elongated indication shall be considered unacceptable, which has a length greater than;
- 6 mm (1/4 in.) for T up to 19 mm (3/4 in.)
- T/3 for T greater than or equal to 19 mm (3/4 in.) and less than or equal to 57 mm (2-1/4 in.) i.e. 19 mm ≤ T ≤ 57 mm.
- 19 mm (3/4 in.) for T greater than 57 mm (2-1/4 in.)
(Where, ‘T’ – Thickness of the weld metal excluding any allowable reinforcement).
3. Any group of indications (inline) with an aggregate length of more than T (within a length of 12T) shall be considered unacceptable except when the distance between the successive discontinuities exceeds 6L.
(where ‘L’ is the length of the longest imperfection in the group).
Acceptance criteria for Rounded Indication (Mandatory Appendix 4):
According to this appendix, those rounded indications which exceed the following dimensions shall be considered relevant.
- T/10 for T less than 3 mm (1/8 in.)
- 0.5 mm (1/64 in.) for T from 3 mm to 6 mm (1/8 in. to 1/4 in.), inclusive
- 1.0 mm (1/32 in.) for T greater than 6 mm to 50 mm (1/4 in. to 2 in.), inclusive
- 1.5 mm (1/16 in.) for T greater than 50 mm (2 in.)
Apart from the above conditions, Mandatory Appendix 4 also contains some tables, charts, and figures as a reference for acceptance/rejection criteria.
Please watch the video (given below) for more clarity on acceptance criteria for the Radiography testing