This part of EN 12516 specifies the tabulation method for determining the wall thickness of valve bodies, bonnets and covers with essentially circular cross-section made in forged, cast or fabricated steel. For valve shells with oval, rectangular or non-circular shapes, see 8.6. The range of PN or Class designations for which thicknesses are tabulated is: PN 2,5, PN 6, PN 10, PN 16, PN 25, PN 40, PN 63, PN 100, PN 160, PN 250, PN 320, PN 400, Class 150, Class 300,Class 600, Class 900, Class 1500, Class 2500, Class 4500. Standard and Special pressure temperature ratings are specified for each material group for the above PN and Class designations. The non-destructive examination procedures and acceptance levels that have to be applied to the valve shell components in order for the valve to be used at Special Class pressure temperature ratings are defined. Details are also given for the alternative rules for small bore valves of DN 65 and smaller. This standard does not apply to threaded end valves: DN 80 or larger; or which have pressure ratings greater than Class 2500; or which operate at temperatures greater than 540 °C. Socket welding end valves DN 80 or larger are outside the scope of this standard.