1.1 These reference radiographs for heavy-walled steel castings are applicable to nominal section thicknesses of 4 1/2 to 12 in. [114 to 305 mm] and consists of two sets as follows: 1.1.1 2-MV X rays and Cobalt-60This includes cobalt-60 or equivalent isotope radiation and from 2 MV up to 4 MV X rays. Set of 28 plates in 81/2 by 11 in. [216 by 279 mm] ring binders. 1.1.2 4-MV to 30-MV X rays. 1.1.3 Each set consists of three categories of graded discontinuities in increasing severity levels, and three categories of ungraded discontinuities furnished as examples only, as follows: 1.1.3.1 Category A-Gas porosity; severity levels 1 through 5. 1.1.3.2 Category B-Sand and slag inclusions; severity levels 1 through 5. 1.1.3.3. Category C-Shrinkage; 3 types:(1) Type 1-Severity levels 1 through 5.(2) Type 2-Severity levels 1 through 5.(3) Type 3-Severity levels 1 through 5. 1.1.3.4 Category D-Crack; one illustration D5 in pre-1972 documents. 1.1.3.5 Category E-Hot tear; one illustration D3 in pre-1972 documents. 1.1.3.6 Category F-Insert; one illustration EB2 in pre-1972 documents. 1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.