ISO 6626-3:2019

Internal combustion engines — Piston rings — Part 3: Coil-spring-loaded oil control rings made of steel

This document specifies the essential dimensions of coil-spring-loaded oil control rings made of steel, of piston ring types SOR (with R-shaped groove) and SOV (with V-shaped groove). This document applies to coil-spring-loaded oil control rings made of steel with a diameter from 60 mm up to and including 160 mm for reciprocating internal combustion engines. It can also be used for piston rings in compressors working under analogous conditions.

Moteurs à combustion interne — Segments de piston — Partie 3: Segments racleurs régulateurs d'huile, en acier, mis en charge par ressort hélicoïdal

General Information

• Status: Published
• Publication Date: 21-Sep-2019
• ICS: 43.060.10 - Engine block and internal components
• Technical Committee: ISO/TC 22/SC 34 - Propulsion, powertrain and powertrain fluids
• Drafting Committee: ISO/TC 22/SC 34/WG 4 - Piston rings
• Current Stage: 9020 - International Standard under periodical review
• Start Date: 15-Jul-2024
• Completion Date: 15-Jul-2024

Relations

• Consolidated By: ISO 23402-1:2020 - Dentistry — Portable dental equipment for use in non‐permanent healthcare environment — Part 1: General requirements
• Effective Date: 06-Jun-2022
• Revises: ISO 6626-3:2008 - Internal combustion engines — Piston rings — Part 3: Coil-spring-loaded oil control rings made of steel
• Effective Date: 05-Nov-2015

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 6626-3
Second edition
2019-09
Internal combustion engines —
Piston rings —
Part 3:
Coil-spring-loaded oil control rings
made of steel
Moteurs à combustion interne — Segments de piston —
Partie 3: Segments racleurs régulateurs d'huile, en acier, mis en
charge par ressort hélicoïdal
Reference number
©
ISO 2019
© ISO 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 1
3.1 Symbols . 1
4 Piston ring types and designation examples . 2
4.1 Type SOR — Steel oil control rings with R-shaped groove . 2
4.1.1 General features and dimensions . 2
4.1.2 Designation . 3
4.2 Type SOV — Steel oil control rings with V-shaped groove. 3
4.2.1 General features and dimensions . 3
4.2.2 Designation . 4
5 Common features . 4
5.1 Ring width h and radial wall thickness a . 4
1 1
5.2 Land width h . 5
5.3 Land angle α, β . 5
5.4 Land spacing B . 5
5.5 Slot sizes . 6
5.6 Nitrided surface. 6
5.7 PVD coating thickness of peripheral surface . 7
5.8 Nominal contact pressure and tangential force . 7
5.8.1 Nominal contact pressure . 7
5.8.2 Actual tangential force, F , and tolerance . 8
t
5.8.3 Normalized tangential force, F .
N 8
5.9 Tolerance of tangential force F . 8
t
6 Coil springs . 8
6.1 Types of coil spring . 8
6.2 Coil-spring excursion (extended gap) .10
6.3 Position of coil spring gap and fixing .11
6.4 Material .11
7 Type SOR .11
8 Type SOV .11
9 Dimensions .12
Bibliography .26
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso
.org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 34,
Propulsion, powertrain and powertrain fluids.
This second edition cancels and replaces the first edition (ISO 6266-3:2008), which has been technically
revised. The main changes compared to the previous edition are as follows:
— added subclause 5.8.2, Actual tangential force, F and tolerance;
t
— added subclause 5.8.3, Normalized tangential force, F ;
N
— added Table 9, Normalized tangential forces, F ;
N
— raised table numbers by one from Table 9 onward;
— made editorial changes to Table 16.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2019 – All rights reserved

Introduction
ISO 6626 (all parts) is one of a series of International Standards dealing with piston rings for
reciprocating internal combustion engines. Others are ISO 6621 (all parts), ISO 6622 (all parts),
ISO 6623, ISO 6624 (all parts), ISO 6625 and ISO 6627 (see Clause 2 and Bibliography).
The common features and dimensional tables presented in this document constitute a broad range of
variables and, in selecting a particular ring type, the designer will bear in mind the conditions under
which it will be required to operate.
INTERNATIONAL STANDARD ISO 6626-3:2019(E)
Internal combustion engines — Piston rings —
Part 3:
Coil-spring-loaded oil control rings made of steel
1 Scope
This document specifies the essential dimensions of coil-spring-loaded oil control rings made of steel,
of piston ring types SOR (with R-shaped groove) and SOV (with V-shaped groove).
This document applies to coil-spring-loaded oil control rings made of steel with a diameter from 60 mm
up to and including 160 mm for reciprocating internal combustion engines. It can also be used for piston
rings in compressors working under analogous conditions.
2 Normative references
There are no normative references in this document.
3 Terms, definitions and symbols
No terms and definitions are listed in this document.
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/
3.1 Symbols
a radial wall thickness
a groove depth
a radial thickness over coil spring
a groove depth and bridge
a external land depth
B land spacing
c slot width
d nominal diameter (nominal bore diameter)
d coil-spring diameter
d coil-spring groove diameter for type SOR
f coil-spring excursion
F tangential force
t
h ring width
h land width
p contact pressure
s closed gap
w slot length
w slot spacing
α land angle inside
β land angle outside
θ groove angle for type SOV
NOTE These symbols (including associated indices) are in accordance with the symbols used in
ISO 6621 (all parts), ISO 6622 (all parts), ISO 6623, ISO 6624 (all parts), ISO 6625, ISO 6627 and other parts of the
ISO 6626 series.
4 Piston ring types and designation examples
4.1 Type SOR — Steel oil control rings with R-shaped groove
4.1.1 General features and dimensions
Figure 1 shows the general features and dimensions of piston ring type SOR.
2 © ISO 2019 – All rights reserved

Dimensions in millimetres
Key
1 reference plane
NOTE 1  For definitions of symbols, see Clause 3.
NOTE 2  For dimensions, see Tables 1, 2, 3, 4, 5, 11, 12, 14, 15, 16, 17, 18 and 19.
Figure 1 — General features and dimensions of piston ring type SOR
4.1.2 Designation
EXAMPLE A coil-spring-loaded oil control ring with R-shaped groove (SOR), a radial wall thickness
class = small (S), of nominal diameter d = 100 mm (100), a nominal ring width h = 3 mm (3), a land width
1 1
h = 0,20 mm (0,20), made of steel MC65 (MC65), a nitrided depth of 0,030 mm min. (NT030), coil spring with
reduced heat set (WF), and variable pitch with coil diameter d ground (CSE), medium nominal contact pressure
p = 1,5 MPa (PN1,5):
Piston ring ISO 6626-3 SOR-S - 100 × 3 × 0,20 – MC65/NT030 WF CSE PN1,5
4.2 Type SOV — Steel oil control rings with V-shaped groove
4.2.1 General features and dimensions
Figure 2 shows the general features and dimensions of piston ring type SOV.
Dimensions in millimetres
Key
1 reference plane
NOTE 1  For definitions of symbols, see Clause 3.
NOTE 2  For
...

Deleted: /PRF
ISO TC 22/SC34/WG 4
Secretariat: DIN
Internal combustion engines — Piston rings — Part 3: Coil-spring-loaded oil control
rings made of steel
© ISO 2019
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or
utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be
requested from either ISO at the address below or ISO's member body in the country of the
requester.
ISO copyright office
Case postale 56 • CH‐1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E‐mail [e-mail]
Web www.iso.org
Published in Switzerland.
© ISO 2019 – All rights reserved 3

ISO 6626-3:2016(E)
Contents
Foreword . 7
Introduction. 8
1  Scope . 9
2  Normative references . 9
3  Terms, definitions and symbols . 9
3.1  Symbols . 9
4  Piston ring types and designation examples . 10
4.1  Type SOR — Steel oil control rings with R‐shaped groove . 10
4.1.1  General features and dimensions . 10
Figure 1 — General features and dimensions of piston ring type SOR . 10
4.1.2  Designation . 10
4.2  Type SOV — Steel oil control rings with V‐shaped groove . 11
4.2.1  General features and dimensions . 11
Figure 2 — General features and dimensions of piston ring type SOV . 11
4.2.2  Designation . 11
5  Common features . 11
5.1  Ring width h and radial wall thickness a . 11
1 1
Table 1 — Ring width h and radial wall thickness a . 11
1 1
5.2  Land width h . 12
Table 2 — Land width h . 12
5.3  Land angle α, β . 12
Table 3 — Land angle α, β . 12
5.4  Land spacing B . 12
Table 4 — Land spacing B . 12
5.5  Slot sizes . 13
Table 5 — Standard slot sizes . 13
Figure 3 — Arrangement of slots . 13
5.6  Nitrided surface . 13
Table 6 — Nitrided case depth of peripheral surface and sideface . 13
5.7  PVD coating thickness of peripheral surface . 14
4 © ISO 2019 – All rights reserved

Table 7 — PVD coating thickness of peripheral surface. 14
5.8  Nominal contact pressure and tangential force . 14
5.8.1  Nominal contact pressure . 14
Table 8 — Nominal contact pressure classes . 14
5.8.2  Actual tangential force, Ft, and tolerance . 14
5.8.3  Normalized tangential force, F . 14
N
5.9  Tolerance of tangential force Ft . 15
Table 10 — Tolerance of tangential force F . 15
t
6  Coil springs . 15
6.1  Types of coil spring . 15
Figure 4 — Type CSN coil spring . 15
Figure 5 — Type CSG coil spring . 16
Figure 6 — Type CSE coil spring . 16
Figure 7 — Position of area with small pitch . 17
6.2  Coil‐spring excursion (extended gap) . 17
Figure 8 — Coil-spring excursion. 17
Table 11 — Coil-spring excursion . 17
6.3  Position of coil spring gap and fixing . 18
6.4  Material . 18
7  Type SOR . 18
Table 12 — Tolerance and calculation criteria on a4, a13, a17, d14, d7 and a12 for type SOR . 18
8  Type SOV . 18
Table 13 — Tolerance and calculation criteria on a , a , a , d and a for type SOV . 18
4 13 17 7 12
9  Dimensions . 19
Table 14 — Index of Tables 15 to 22 . 19
Table 15 — Recommended nominal tangential force of ring type SOR-S (h = 1,5 mm) . 19
Table 16 — Recommended nominal tangential force of ring type SOR-S (h = 2,0 mm and
h = 2,5 mm) . 20
Table 17 — Recommended nominal tangential force of ring type SOR-S and SOR-L
(h = 3,0 mm) . 22
Table 18 — Recommended nominal tangential force of ring type SOR-S and SOR-L
(h = 4,0 mm; nominal diameters d < 125 mm) . 24
1 1
© ISO 2019 – All rights reserved 5

ISO 6626-3:2016(E)
Table 19 — Recommended nominal tangential force of ring type SOR-S and SOR-L
(h = 4,0 mm; nominal diameters d ≥ 125 mm) . 26
1 1
Table 20 — Recommended nominal tangential force of ring type SOV-S and SOV-L
(h = 3,0 mm) . 28
Table 21 — Recommended nominal tangential force of ring type SOV-S and SOV-L
(h = 4,0 mm; nominal diameters d < 125 mm) . 29
1 1
Table 22 — Recommended nominal tangential force of ring type SOV-S and SOV-L
(h = 4,0 mm; nominal diameters d ≥ 125 mm) . 31
1 1
Bibliography . 33
6 © ISO 2019 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national
standards bodies (ISO member bodies). The work of preparing International Standards is normally
carried out through ISO technical committees. Each member body interested in a subject for which a
technical committee has been established has the right to be represented on that committee.
International organizations, governmental and non‐governmental, in liaison with ISO, also take part in
the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all
matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT)
see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 34,
Propulsion, powertrain and powertrain fluids.
This second edition cancels and replaces the first edition (ISO 6266‐3:2008), which has been technically
revised. The main changes compared to the previous edition are as follows:
— added subclause 5.8.2, Actual tangential force, .F and tolerance;
t
— added subclause 5.8.3, Normalized tangential force, FN;
— added Table 9, Normalized tangential forces, F;
N
— raised table numbers by one from Table 9 onward;
— made editorial changes to Table 16.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
© ISO 2019 – All rights reserved 7

ISO 6626-3:2016(E)
Introduction
ISO 6626 (all parts) is one of a series of International Standards dealing with piston rings for
reciprocating internal combustion engines. Others are ISO 6621 (all parts), ISO 6622 (all parts),
ISO 6623, ISO
...