The liquid penetrant testing code refers to ASME Code Section V article 6 for performing the test. This code section provides requirements for liquid penetrant testing Personnel qualification, written procedure requirements, liquid penetrant test techniques and process and its related requirements, penetrant and developer dwell time requirement, liquid penetrant testing equipment calibration requirements and etc. The code section guides how to perform the test and what requirements shall be followed.
ASME Code section V article 6 does not provide the acceptance criteria. For acceptance criteria, you should refer to corresponding manufacturing code.
For example, if you are going to perform a liquid penetrant test on power piping girth weld, the acceptance criteria can be found on the ASME B31.1, or you want to perform a liquid penetrant test on process piping, then you need to refer to the ASME B31.3. Please note, an indication might be considered as a defect by a construction code, but the same indication not considered a defect by another manufacturing code.
The test always shall be performed based on approved procedure. The procedure is typically prepared and approved by an ASNT Level III and conducted by a level II technician.
The other considered as standard and not code. The verbiage of code is used when mandated by a government or authority. For example in the state of California, designing and manufacturing of pressure vessel shall be based on ASME Code. Then automatically, requirements of the ASME Section V article 6 for liquid penetrant testing is a requirement by law (when is applied to pressure vessel)
The other common standard is:
ASTM E 165, Standard Practice for Liquid Penetrant Examination for General Industry
ASTM A903, Standard Specification for Steel Castings, Surface Acceptance Standards, Magnetic Particle and Liquid Penetrant Inspection
ASTM E1208, Standard Practice for Fluorescent Liquid Penetrant Testing Using the Lipophilic Post-Emulsification Process
ASTM E1220, Standard Practice for Visible Penetrant Testing Using Solvent-Removable Process
There are hundreds of other standard and specification in the market for performing and evaluating the result of liquid penetrant testing. Each industry has own codes and standards.
For instance, Society of Automotive Engineers International have SAE AMS 2644 (Inspection Material, Penetrant), SAE AMS 2647B (SAE AS 3071A), SAE AMS 3161A (Oil, Odorless Heavy Solvent), SAE AS 3071A (Acceptance Criteria Fluorescent Penetrant) and SAE J 426 (Liquid Penetrant Test Methods, Information Report)