What is ISO 6621‑5 about?

ISO 6621 is a series of international standards on internal combustion engines of a road vehicle that specifies the quality requirements of piston rings. ISO 6621‑5 is the fifth part of the ISO 6621 series of standards that is applicable to the quality requirements of piston rings. It details best practices for reciprocating internal combustion engines for road vehicles and other applications and is applicable to all such rings of a nominal diameter from 30 mm up to and including 200 mm.

ISO 6621‑5 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
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.

ISO 6621‑5 also covers those features for which no recognized quantitative measurement procedures exist and which are only checked visually with normal eyesight (glasses worn normally) and without magnification. Such features (superficial defects) are additional to the standard tolerances of ring width, radial wall thickness, and closed gap.

NOTE: ISO 6621‑5 does not establish acceptable quality levels (AQL), it is left to the manufacturer and customer to decide the appropriate levels jointly.

Who is ISO 6621‑5 for?

ISO 6621‑5 on piston rings is useful for:

Mechanical engineers
Designers and manufacturers of piston rings
Manufacturers of road vehicle engines

Why should you use ISO 6621‑5?

A piston ring is a metallic split ring that is attached to the outer diameter of a piston in an internal combustion engine or steam engine to seal the gap between the piston and the cylinder wall. In ISO 6621‑5, the commonly encountered aspects of quality in terms of casting defects and other departures from ideal are quantified.

Inspection of piston rings for visible defects such as pores, cavities, sand inclusions, scratches, indentations, depressions, and cracks are generally provided in ISO 6621‑5 without magnification.

With ISO 6621‑5, you get guidance on the edge configuration of piston rings that should be free from burrs and from ragged edges. ISO 6621‑5 provides conditions to measure tangential force loss.

As an ISO 6621-5 user, you will be able to make piston rings that meet the highest quality standards for lubrication and wear protection for road vehicle engines, ensuring businesses with consistent performance with reliability and low cost. In this manner, you would be able to produce high-quality and efficient products.

What’s changed since the last update?

BS ISO 6621‑5:2020 supersedes BS ISO 6621‑5:2013. BS ISO 6621‑5:2020 includes some technical changes with respect to BS ISO 6621‑5:2013. These include:

Changed procedure for counting defects.

BS ISO 6621-5:2020

Internal combustion engines. Piston rings - Quality requirements

Current

Published:

31 Jan 2020