ISO 6622-1:2021

Overview

ISO 6622-1:2021 - Internal combustion engines - Piston rings - Part 1: Rectangular rings made of cast iron - specifies the essential dimensional features for rectangular cast‑iron piston rings (Types R, B, BA, and M) with nominal diameters up to and including 200 mm. The standard applies to reciprocating internal‑combustion engine pistons and to compressors operating under similar conditions. This third edition (2021) updates the 2003 edition with clarified figures, added taper option (M6) and editorial improvements.

Key topics and technical requirements

• Ring types and geometry: Defines straight‑faced (R), barrel‑faced (B), asymmetrical barrel‑faced (BA) and taper‑faced (M) ring shapes with reference figures and dimension tables.
• Dimensional tables and figures: Provides detailed tables for gauge widths, barrel/taper dimensions, radial wall thickness options and ring forces (see Tables 1–14 and Figures 1–13 in the document).
• Face coatings and inlays: Describes face coating types (uncoated, fully faced, semi‑inlaid, inlaid) and minimum plating/coating thickness requirements for peripheral faces.
• Twist and chamfer features: Specifies permissible twist values, positive/negative twist types (IF, IW, IFV, etc.), chamfer and edge dimensions and manufacturer discretion where standard twist is invoked.
• Designation conventions: Examples show how to designate rings by type, nominal diameter and width, material subclass (e.g., MC12, MC51), and coating (e.g., CR3, SC2F).
• Force factors and performance data: Includes force factor tables and specific ring force/dimension relationships for standard and thicker radial wall designs.
• Normative references: Uses terms and definitions from ISO 6621-1 and refers to ISO 6621-4 for general specifications.

Applications and who uses it

ISO 6622-1:2021 is intended for:

• Engine designers and OEMs specifying piston rings for reciprocating internal combustion engines.
• Piston‑ring manufacturers and foundries producing cast‑iron rectangular rings.
• Compressor manufacturers selecting compatible rings for compressor pistons.
• Quality, procurement and testing teams ensuring correct ring geometry, coatings and designation compliance.
• Aftermarket and remanufacturing suppliers matching replacement rings to original specifications.

Practical benefits include consistent interchangeability, predictable sealing/force behaviour, clearer coating and twist requirements and reduced design ambiguity.

Related Standards (if applicable)

• ISO 6621-1: Vocabulary for piston rings (normative reference)
• ISO 6621-4: General specifications for piston rings (normative reference)
• Other parts in the ISO 6622 series and related ISO 662x standards covering different ring materials and shapes.

For selection, designers should consult the dimensional tables and force factors in ISO 6622-1 and cross‑reference ISO 6621‑4 requirements before finalizing piston‑ring choice.