sw007;
It depends on the specific application and governing Codes or Standards for the application. For example, if you have nothing to fall back on for casting quality (I would check API), the acceptance criteria for cast valve bodies are in ASME B16.34, as Annex D. If you do not have a copy of this standard;

Liquid PT Acceptance Criteria for Castings

Linear indications;
o.3" in length for materials up to 0.5" in thickness
0.5" in length for materials over 0.5" to 1" in thickness
0.75" in length for materials over 1" in thickness

for rounded indications
0.3" in diameter for materials up to 0.5" in thickness
0.5" in diameter for materials over 0.5" in thickness




 

sw007

API 610/ISO 13709, 7.2.2. states that "NDE shall be performed as required by the material specification. If additional...liquid penetrant examination...is specified by the Purchaser...shall be in accordance with Table 13 - Materials Inspection Standards."

In which case, Table 13 gives ASME V Articles 6 and 24 for the Liquid Penetrant Method with ASME VIII Div 1 Appendix 7 as the acceptance standard for castings. Appendix 7 is a comprehensive document - just hope that no additional contractual examination has been specified so that its all down to the relevant material specification.

Hope this helps.

Nigel Armstrong
Lloyds Register
Independent Verification Body Surveyor
 

In addition to what others have noted, I think there are basic definitions and procedures etc. in multiple ASTM standards discussing liquid penetrant testing/inspection (and also of course specific directions from component vendors for same etc.)    

sw007--One item I would be concerned about is if your castings have been cleaned by shot blasting. If so, this would tend to close up any discontinuities that penetrant inspection would be expected to find.

I have the same concerns as swall. Extending the argument ,in the machined  iron casting,flake graphite might get removed and provide cavities. How is the interpretation done in that case?

Chocolates,men,coffee: are somethings liked better rich!!
(noticed in a coffee shop)

In my opinion, subject to the limitation associated with surface examination NDT techniques, if machining revealed or produced discontinuities, these would be rejectable if they exceeded the acceptance criteria.

Surface preparation for the casting is normally defined in the procedure used for the NDT method. If there is a concern with casting integrity, volumetric NDT in conjnction with surface NDT would be selected by the user.