BS ISO 6621-5-2020 pdf free download.Internal combustion engines — Piston rings Part 5: Quality requirements
This document specifies quality aspects that can be defined but that are not normally found on a drawing specification.
It covers the following:
— single-piece piston rings of grey cast iron or steel;
— multi-piece piston rings (oil control rings) consisting of cast iron parts and spring components; and — single-piece and multi-piece oil control rings of steel, i.e. oil control rings in the form of strip steel components or steel segments (rails) with spring expander components.
In addition to specifying some of the limits of acceptance relating to inspection measuring principles (covered by ISO 6621-2), this document also covers those features for which no recognized quantitative measurement procedures exist and which are only checked visually with normal eyesight (glasses if worn normally) and without magnification. Such features (superficial defects) are additional to the standard tolerances of ring width, radial wall thickness and closed gap.
This document does not establish acceptable quality levels (AQL), it being left to manufacturer and customer to decide the appropriate levels jointly. In this case, the recommendations of ISO 2859-1 are followed.
This document specifies the quality requirements of piston rings for reciprocating internal combustion engines for road vehicles and other applications. It is applicable to all such rings of a nominal diameter from 30 mm up to and including 200 mm.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 6621-1, Internal combustion engines — Piston rings — Part 1: Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 6621-1 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Visible defects
4.1 General
Visible defects are divided into two principle classes as described in 4.2 to 4.5.
The first class covers those defects frequently found in castings and includes such defects as porosity,sand inclusions, cavities, etc.
The second class of defect covers mechanical abrasions which may occur during forming, machining or handling of the rings, and includes scratches, dents, chipping, burrs and cracks.
Inspection of piston rings for such defects is generally carried out visually, without magnification, by inspectors having normal eyesight, corrected if necessary.
It is not intended that every ring be rigorously inspected for size and distribution of defects, but rather that the values given in the tables and text be used as a general guide. However, in case of doubt, the values given should be used as the means of judging the quality of the rings.
4.2 Pores, cavities and sand inclusions
Such defects are permissible on uncoated surfaces and edges provided that the values given in Table 1 for size, number and spacing are not exceeded.
4.3 Scratches, indentations, depressions and cracks
4.3.1 Scratches
Isolated scratches are permissible provided that:
— no burrs are produced exceeding the permissible values given in 4.4.1.1;
— on turned peripheral surfaces, they are not deeper than the tool marks;
— on non-turned peripheral surfaces, they are not deeper than 0,004 mm;
— on the side faces, they are not deeper than 0,01 mm; and
— on other surfaces, they are not deeper than 0,06 mm.
4.3.2 Indentations, depressions
Indentations and depressions are permissible provided that:
— the values given in Table 1 for number and spacing of defects are met;
— no burrs are produced exceeding the permissible values given in 4.4.1.1; and
— they do not exceed the values for size and depth given in Table 2.
Rings of a plated/coated/nitrided type shall not have indentations or depressions on the periphery.
NOTE Indentations arising from hardness measurements on the side faces are acceptable provided that they do not exceed the limits given in Tables 2 and 11.
4.3.3 Cracks
No cracks are permissible in the base material.
See also 4.5.4 for chromium-plated peripheral surfaces and 4.5.6 for nitrided surfaces.
4.4 Edges
4.4.1? Edge? configuration
All edges of the piston ring shall be sharp; ideally, they should be free from burrs and from ragged edges,whether arising from crumbling of material or from deburring. Such conditions are almost impossible to achieve regularly in volume production and hence both burrs and removal of edge material is permitted up to the maximum sizes given in 4.4.1.1 and 4.4.1.2.
4.4.1.1 Burrs
Burrs are permitted up to the maximum values given in Table 3. The orientation and direction of burrs shall relate to the functional surfaces of the piston ring; any burr present should point in the direction of sliding motion of the ring and not normal to the direction of sliding.
Any burrs remaining on the edges of rings should be firmly attached, forming an integral part of the edge.BS ISO 6621-5 pdf download.