scope:

This part of ISO 6621 specifies those quality aspects that arecapable of definition but not normally found on a drawingspecification. It is applicable to the following: ? single-piecepiston rings of grey cast iron or steel; ? multi-piece piston rings(oil control rings) consisting of cast iron parts and springcomponents; ? single-piece and multi-piece oil control rings ofsteel, i.e. oil control rings in the form of strip steel componentsor steel segments (rails) with spring expander components. Inaddition to specifying certain of the limits of acceptance relatingto inspection measuring principles (covered by ISO 6621-2), thispart of ISO 6621 also covers those features for which no recognizedquantitative measurement procedures exist and which are onlychecked visually with normal eyesight (spectacles if worn normally)and without magnification. Such features (superficial defects) areadditional to the standard tolerances of ring width, radial wallthickness, and closed gap. This part of ISO 6621 does not establishacceptable quality levels (AQL), it being left to manufacturer andclient to decide the appropriate levels jointly. In this case, therecommendations of ISO 2859 are followed. This part of ISO 6621specifies the quality requirements of piston rings forreciprocating internal combustion engines for road vehicles andother applications. It is applicable to all such rings of a nominaldiameter from 30 mm up to and including 200 mm.