ASME B31.3 acceptance criteria

  • ASME B31.3 acceptance criteria

    Posted by navi on 20/08/2021 at 8:02 pm

    ASME B31.3 acceptance criteria for Ultrasonic/ PAUT testing refers to 244.6.2 and is as follows:

    341.3.2 Acceptance Criteria. Acceptance criteria shall be as stated in the engineering design and shall at least meet the applicable requirements stated below.

    (a) Welds

    (1) For radiography and visual, see Table 341.3.2.

    (2) For magnetic particle, see para. 344.3.2.

    (3) For liquid penetrant, see para. 344.4.2.

    (4) For ultrasonic, see para. 344.6.2.

    (b) Castings. Acceptance criteria for castings are specified in para. 302.3.3.


    344.6.2 Acceptance Criteria. A linear-type discontinuity
    is unacceptable if the amplitude of the indication
    exceeds the reference level and its length exceeds
    (a) 6 mm (1⁄4 in.) for Tw ≤ 19 mm (3⁄4 in.)

    (b) Tw/3 for 19 mm < Tw ≤ 57 mm (21⁄4 in.)

    (c) 19 mm for Tw > 57 mm

    Where does it say that lack of fusion, lack of root fusion/ penetration or cracks are acceptable or not?

    I understand that these are serious flaws and they are linear type indications but I am sure they cannot be classed and sized as per ASME b31.3 244.6.2

    Client that I am working for has additional requirements stating that these defects are not acceptable regardless of length. What other linear-type defects exist apart from these 4 critical defects mentioned above? As I am aware, all other type defects are volumetric therefore again this UT acceptance criteria does not apply.

    If we look at Table 341.3.2 Acceptance Criteria for Welds — Visual and Radiographic Examination, LOF is not acceptable. Why it would be acceptable in UT/ PAUT examination?

    If you are testing weld with UT/PAUT method and were given ASME B31.3 as a acceptance criteria, what would you do?

    I do understand that this acceptance criteria is a minimum requirements but I still find it hard to believe that liner type defect can be accepted based on length 1/3 of thickness is acceptable length.

    Where does it separate acceptance criteria for normal service, Severe cyclic service and fluid service? Its clear in Radiography (RT) in Table 341.3.2 but not in UT.

    Sizing: Signal from indication shall be at reference level or above reference… If we are inspecting 60mm wall thickness pipe, if we refer to B31.3 only, we are allowed 5.9mm lack of side wall fusion in height and up to 19.9mm in length… Calibration block used will have lets say 10% (ASME V article 4 piping calibration block 8-11% wall thickness) of wall thickness notch and that is 6mm in this case therefore 6mm notch will be set on 80% screen height as a reference.

    Of course, no client will accept this acceptance criteria but I believe that ASME should have been more clear in this case.

    Other point that is somewhat not related to this or it is, If acceptance criteria specify following: no linear defects acceptable regardless of length, your evaluation is set that all indications greater than 20% of your reference level shell be investigated. What do you do if you have 1mm indication that is 20.4% of your reference? If you size it with 6dB drop, length will be 6mm for example but highest signal is on only 1mm section and its .4% above evaluation level.

    Doug replied 10 months, 4 weeks ago 2 Members · 1 Reply
  • 1 Reply
  • Codes and Standards


    22/09/2021 at 12:23 pm
    35 Points

    I do agree. We had similar cases too.

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