This document specifies a magnetic flux leakage (MFL) testing method and evaluation of results for in-use equipment made of ferromagnetic materials. This document is mainly applicable for the detection of volume defects such as corrosion and mechanical damage on the test surface and the opposite surface of plate and tubular structures.  A coating with a maximum thickness of 6 mm is allowed on the test surface.

This document applies to external MFL testing of in-use ferromagnetic seamless steel pipes and base metal of pressure vessel shells with an outer diameter of not less than 38 mm and a wall thickness of not more than 20 mm. This document is also applicable to MFL testing of base metal of pressure vessels and storage tank bottom plates with a wall thickness of not more than 20 mm.