ISO/DIS 6626-1

Internal combustion engines -- Piston rings

Moteurs à combustion interne -- Segments de piston

Standards Content (sample)

DRAFT INTERNATIONAL STANDARD
ISO/DIS 6626-1
ISO/TC 22/SC 34 Secretariat: ANSI
Voting begins on: Voting terminates on:
2016-06-06 2016-09-05
Internal combustion engines — Piston rings —
Part 1:
Coil-spring-loaded oil control rings made of cast iron
Moteurs à combustion interne — Segments de piston —

Partie 1: Segments racleurs régulateurs d’huile mis en charge par ressort hélicoïdal

ICS: 43.060.10
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ISO/DIS 6626-1:2016(E)
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ISO 6626-1:2016(E)
Contents

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Foreword................................................................................................................................................................................... 5

Introduction ............................................................................................................................................................................ 5

1 Scope ....................................................................................................................................................................................... 6

1 Normative references .......................................................................................................................................... 6

2 Overview .................................................................................................................................................................... 6

3 Piston ring types and designation .................................................................................................................. 6

3.2 Type DSF-C ─ Coil spring loaded bevelled edge oil control ring, chromium plated and

profile ground ..................................................................................................................... 7

3.2.1 General features and dimensions ......................................................................................... 7

3.2.2 Designation of a Type DSF-C piston ring in accordance with ISO 6626-1 ................................. 8

3.3 Type DSF-CNP ─ Coil spring loaded bevelled edge oil control ring, chromium plated not

profile ground ..................................................................................................................... 8

3.3.1 General features and dimensions ......................................................................................... 8

3.3.2 Designation of a Type DSF-CNP piston ring in accordance with ISO 6626-1............................. 9

3.4 Type SSF ─ Coil spring loaded slotted oil control ring ......................................................... 10

3.4.1 General features and dimensions ....................................................................................... 10

3.4.2 Designation of a Type SSF piston ring in accordance with ISO 6626-1 .................................. 10

3.5 Type GSF ─ Coil spring loaded double bevelled oil control ring............................................ 11

3.5.1 General features and dimensions ....................................................................................... 11

3.5.2 Designation of a Type GSF piston ring in accordance with ISO 6626-1 .................................. 11

3.6 Type DSF ─ Coil spring loaded bevelled edge oil control ring............................................... 12

3.6.1 General features and dimensions ....................................................................................... 12

3.6.2 Designation of a Type DSF piston ring in accordance with ISO 6626-1 .................................. 12

3.7 Type DSF-NG ─ Coil spring loaded bevelled edge oil control ring (face geometry similar

to type DSF-C or type DSF-CNP) ......................................................................................... 13

3.7.1 General features and dimensions ....................................................................................... 13

3.7.2 Designation of a Type DSF-NG piston ring in accordance with ISO 6626-1 ............................ 13

3.8 Type SSF-L ─ Coil spring loaded slotted oil control ring with 0,6 mm nominal land width ...... 14

3.8.1 General features and dimensions ....................................................................................... 14

3.8.2 Designation of a Type SSF-L piston ring in accordance with ISO 6626-1 ............................... 14

4 Common features .................................................................................................................................................14

4.1 Oil drainage by slots or holes ............................................................................................. 15

4.1.1 Arrangement of slots ......................................................................................................... 15

4.1.2 Slot length ........................................................................................................................ 16

4.1.3 Arrangement of holes ........................................................................................................ 16

4.2 Plating thickness — DSF-C and DSF-CNP Coil spring loaded oil control rings....................... 17

4.3 Peripheral edges at gap of chromium plated oil control rings ............................................... 17

4.4 Spring groove offset and land offset ................................................................................... 18

5 Coil springs..............................................................................................................................................................18

5.1 Types of coil spring ........................................................................................................... 18

5.2 Coil spring excursion (extended gap).................................................................................. 20

5.3 Position of coil spring gap and fixing .................................................................................. 20

5.4 Material ............................................................................................................................. 21

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ISO 6626-1:2016(E)

6 Tangential force and nominal contact pressure ....................................................................................21

6.1 Tangential force, Ft ............................................................................................................ 21

6.1.1 Force factors ..................................................................................................................... 21

6.1.2 General tangential force, F................................................................................................. 21

6.1.3 Actual tangential force, F , and tolerance ............................................................................ 22

6.2 Nominal contact pressure, p ............................................................................................. 22

8 Dimensions .............................................................................................................................................................24

4 © ISO 2016 – All rights reserved
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ISO 6626-1:2016(E)
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. 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. 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 on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO's adherence to the WTO principles in the Technical

Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC22/SC34.

This part 1 cancels and replaces the ISO 6626:1989, of which has been technically revised.

ISO 6626 consists of the following parts, under the general title Internal combustion engines — Piston

rings:
• Part 1: Coil -spring- loaded oil control rings made of cast iron

• Part 2: Coil -spring- loaded oil control rings of narrow width made of cast iron

• Part 3: Coil -spring- loaded oil control rings made of steel
Introduction

ISO 6626 is one of a series of International Standards dealing with piston rings for reciprocating

[1], [2] [3] [4] [5] [6]

internal combustion engines. Others are ISO 6621 , ISO 6622 , ISO 6623 , ISO 6624 , ISO 6625

[9]
[7] [8]
ISO 6626 and ISO 6627 .
© ISO 2016 – All rights reserved 5
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ISO 6626-1:2016(E)
Internal combustion engines — Piston rings — Part 1: Coil spring
loaded oil control rings made of cast iron
1 Scope

This part of ISO 6626 specifies the essential dimensional features of coil spring loaded oil control rings made

of cast iron, types DSF-C, DSF-CNP, SSF, GSF, DSF, DSF-NG and SSF-L. It is applicable to piston rings in

sizes from 60 mm up to and including 200 mm for reciprocating internal combustion engines for road vehicles

and other applications.
1 Normative references

The following referenced documents are indispensable for the application 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 6621-3, Internal combustion engines — Piston rings — Part 3: Material specifications

ISO 6621-4, Internal combustion engines — Piston rings — Part 4: General specifications

ISO 6621-5, Internal combustion engines — Piston rings — Part 5: Quality requirements

2 Overview

The coil spring loaded oil control ring types are specified in Figures 1 to 8. Their common features and

the features' dimensions are specified in Tables 1 to 5 and shown in Figures 9 to 11. Essential features

of coil springs are shown in Figures 12 to 16. Table 7 specifies different classes of contact pressure.

Tables 8 to 13 give the dimensions and forces of coil spring loaded oil control rings.

The normal range for axial width of coil spring loaded oil control rings (3 to 8 mm inclusive) is driven

into 0,5 or 1,0 mm steps. In Tables 14 to 19 dimensions are given for coil spring loaded oil control rings

with an axial width of 4,75 mm (i.e. 3/16 inch) for existing applications in inch units.

For the cast iron part the recommended material is Class 10 in accordance with ISO 6621-3. For special

applications, material Classes 20 to 50 may be used.

Variation from these in face design and spring groove may be used, as recommended by individual

manufacturers, in plain or chromed versions.
3 Piston ring types and designation
3.1 Types DSF-C,DSF-CNP, SSF, GSF, DSF, DSF-NG and SSF-L
3.1.1 General features and dimensions
See Figure 1 and Tables 8 to 19
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ISO 6626-1:2016(E)
Figure 1 — Types DSF-C, DSF-CNP, SSF, GSF, DSF, DSF-NG and SSF-L

3.2 Type DSF-C ─ Coil spring loaded bevelled edge oil control ring, chromium plated

and profile ground
3.2.1 General features and dimensions
See Figure 2 and Tables 8 and 14.
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ISO 6626-1:2016(E)
Dimensions in millimetres
Key
1 reference plane
2 see table 3
3 see table 4
4 see table 5
Figure 2 — Type DSF-C
3.2.2 Designation of a Type DSF-C piston ring in accordance with ISO 6626-1

EXAMPLE Coil spring loaded bevelled edge oil control ring, chromium plated and profile ground (DSF-C), of nominal

diameter d = 125 mm (125), nominal ring width h = 3,5 mm (3,5), a land width h =0,25 mm (0,25), made of grey cast

1 1

iron, non-heat treated, material subclass 11 (MC11), having a selected closed gap of 0,20 mm min. (S020), a chromium

layer thickness on the lands of 0,15 mm (CR3), phosphated on all cast iron surfaces to depth of 0,002 mm min. (PO),

reduced slot length (WK), a coil spring with reduced heat set (WF), and a variable pitch with coil diameter d ground

(CSE), with tangential force F in accordance with the nominal contact pressure of 1,5N/mm² (PN1,5) and the ring marked

w ith the manufacturer's mark (MM). Parameters in parenthesis are used in the ISO ring designation:

Piston ring ISO 6626-1 DSF-C - 125 × 3,5 x 0,25 - MC11 / S020 CR3 PO WK WF CSE PN1,5 MM

3.3 Type DSF-CNP ─ Coil spring loaded bevelled edge oil control ring, chromium plated

not profile ground
3.3.1 General features and dimensions
See Figure 3 and Tables 9 and 15.
Dimensions in millimetres
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ISO 6626-1:2016(E)
Key
1 reference plane
2 see table 3
3 see table 4
4 see table 5
Figure 3 — Type DSF-CNP
3.3.2 Designation of a Type DSF-CNP piston ring in accordance with ISO 6626-1

EXAMPLE Coil spring loaded slotted oil control ring (DSF-CNP) of nominal diameter d = 100 mm (100), nominal

ring width h = 4,0 mm (4,0), a land width h =0,40 mm (0,40), made of grey cast iron, non-heat treated, material subclass

in accordance with the nominal contact pressure of
12 (MC12), constant spring pitch (CSN) and tangential force F

1,0N/mm² (PN1,0). Parameters in parenthesis are used in the ISO ring designation:

Piston ring ISO 6626-1 SSF- 100 × 4 x 0,40 - MC12 / CSN PN1,0
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ISO 6626-1:2016(E)
3.4 Type SSF ─ Coil spring loaded slotted oil control ring
3.4.1 General features and dimensions
See Figure 4 and Table 10 and 16.
Dimensions in millimetres
Key
1 reference plane
2 see table 4
3 see table 5
Figure 4 — Type SSF
3.4.2 Designation of a Type SSF piston ring in accordance with ISO 6626-1

EXAMPLE Coil spring loaded slotted oil control ring (SSF) of nominal diameter d = 80 mm (80), nominal ring width

h = 4 mm (4,0), a land width h =0,70 mm (0,70),made of grey cast iron, non-heat treated, material subclass 12 (MC12),

constant spring pitch (CSN) and tangential force F in accordance w ith the nominal contact pressure of 1,0N/mm² (PN1,0).

Parameters in parenthesis are used in the ISO ring designation:
Piston ring ISO 6626-1 SSF- 80 × 4,0 x 0,70 - MC12 / CSN PN1,0
10 © ISO 2016 – All rights reserved
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ISO 6626-1:2016(E)
3.5 Type GSF ─ Coil spring loaded double bevelled oil control ring
3.5.1 General features and dimensions

See Figure 5 and Table 11 and 17. Top-side marking is mandatory in accordance with ISO 6621-4.

Dimensions in millimetres
Key
1 reference plane
2 top side identification mark
3 see table 4
4 see table 5
Figure 5 — Type GSF
3.5.2 Designation of a Type GSF piston ring in accordance with ISO 6626-1

EXAMPLE Coil spring loaded double bevelled oil control ring (GSF) of nominal diameter d = 75 mm (75), nominal

ring width h = 3,5 mm (3,5), a land width h =0,35 mm (0,35), made of grey cast iron, non-heat treated, material subclass

12 (MC12), with constant spring pitch (CSN) and tangential force F in accordance with the nominal contact pressure of

1,0N/mm² (PN1,0). Parameters in parenthesis are used in the ISO ring designation:

Piston ring ISO 6626-1 GSF- 75 × 3,5 x 0,35 - MC12 / CSN PN1,0
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ISO 6626-1:2016(E)
3.6 Type DSF ─ Coil spring loaded bevelled edge oil control ring
3.6.1 General features and dimensions
See Figure 6 and Tables 11 and 17.
Dimensions in millimetres
Key
1 reference plane
2 see table 4
3 see table 5
Figure 6 — Type DSF
3.6.2 Designation of a Type DSF piston ring in accordance with ISO 6626-1

EXAMPLE Coil spring loaded double bevelled oil control ring (DSF) of nominal diameter d = 90 mm (90), nominal

ring width h = 3,5 mm (3,5), a land width h =0,35 mm (0,35), made of grey cast iron, non-heat treated, material subclass

12 (MC12), with constant spring pitch (CSN) and tangential force F in accordance with the nominal contact pressure of

1,0N/mm² (PN1,0). Parameters in parenthesis are used in the ISO ring designation:

Piston ring ISO 6626-1 DSF- 90 × 3,5 x 0,35 - MC12 / CSN PN1,0
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ISO 6626-1:2016(E)

3.7 Type DSF-NG ─ Coil spring loaded bevelled edge oil control ring (face geometry

similar to type DSF-C or type DSF-CNP)
3.7.1 General features and dimensions
See Figure 7 and Tables 12 and 18.
Dimensions in millimetres
Key
1 reference plane
2 see table 4
3 see table 5
Figure 7 — Type DSF-NG
3.7.2 Designation of a Type DSF-NG piston ring in accordance with ISO 6626-1

EXAMPLE Coil spring loaded slotted oil control ring (DSF-NG) of nominal diameter d = 140 mm (140), nominal ring

w idth h = 4,5 mm (4,5), a land width h5=0,40 mm (0,40), made of grey cast iron, non-heat treated, material subclass 12

(MC12), constant spring pitch (CSN) and tangential force F in accordance w ith the nominal contact pressure of 1,0N/mm²

(PN1,0). Parameters in parenthesis are used in the ISO ring designation:
Piston ring ISO 6626-1 DSF-NG - 140 × 4,5 x 0,40 - MC12 / CSN PN1,0
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ISO 6626-1:2016(E)

3.8 Type SSF-L ─ Coil spring loaded slotted oil control ring with 0,6 mm nominal land

width
3.8.1 General features and dimensions
See Figure 8 and Tables 13 and 19.
Dimensions in millimetres
Key
1 reference plane
2 see table 4
3 see table 5
Figure 8 — Type SSF-L
3.8.2 Designation of a Type SSF-L piston ring in accordance with ISO 6626-1

EXAMPLE Coil spring loaded slotted oil control ring (SSF-L) of nominal diameter d = 80 mm (80), nominal ring

= 3,0 mm (3,0), made of grey cast iron, non-heat treated, material subclass 12 (MC12), constant spring pitch

w idth h

(CSN) and tangential force F in accordance with the nominal contact pressure of 1,0N/mm² (PN1,0). Parameters in

parenthesis are used in the ISO ring designation:
Piston ring ISO 6626-1 SSF-L - 80 × 3,0 - MC12 / CSN PN1,0
4 Common features
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ISO 6626-1:2016(E)
4.1 Oil drainage by slots or holes
4.1.1 Arrangement of slots
See Figure 9 and Table 1.
Dimensions in millimetres
b) 10 slots for 80 ≤ d < 115
a) 8 slots for 60 ≤ d < 80 1
d) 14 slots for 150 ≤ d ≤ 200
c) 12 slots for 115 ≤ d < 150 1
Figure 9 — Arrangement of slots
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ISO 6626-1:2016(E)
Table 1 — Cutter diameter
Dimensions in millimetres
Cutter
Nominal
diameter
diameter
max.
60 ≤ d < 150
150 ≤ d ≤ 200
4.1.2 Slot length
4.1.2.1 Standard slot length
Slot length, w , shall be equal to bridge length, w .
1 2
The maximum difference between w and w shall be 4 mm.
1 2
4.1.2.2 Reduced slot length — Code WK

Oil control rings with reduced slot length will retain the same number of slots and the same angular

spacing. The maximum difference between w and w for the standard slot length does not apply.

1 2
See Table 2.
Table 2 — Reduced slot length
Dimensions in millimetres
d w (range of nominal values)
1 1
60 ≤ d < 80
6 ... 11
80 ≤ d < 115
8 ... 13
115 ≤ d < 150
10 ... 15
150 ≤ d ≤ 200
1 12 ... 18
4.1.3 Arrangement of holes

Arrangement of holes is shown in Figure 10. Deviating arrangements shall be agreed between

manufacturer and customer.
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ISO 6626-1:2016(E)
Figure 10 — Arrangement of holes
5.1.4 Diameter and number of holes

The diameter (d ) and number (n) of holes to be agreed between manufacturer and customer.

4.2 Plating thickness — DSF-C and DSF-CNP Coil spring loaded oil control rings
See Figure 11 and Table 3.
Figure 11 — Plating thickness
Table 3 — Plating thickness
Dimensions in millimetres
Code
Thickness
min.
CR1 0,05
CR2 0,10
CR3 0,15
For plating thickness tolerances, see ISO 6621-4.
4.3 Peripheral edges at gap of chromium plated oil control rings
For features and their dimensions, see ISO 6621-4.
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ISO 6626-1:2016(E)
4.4 Spring groove offset and land offset
See Figures 2 - 8 and Tables 4 and 5.
Table 4 — Permitted land offset Table 5 — Permitted spring groove offset
Dimensions in millimetres Dimensions in millimetres
Axial width Axial width
t v
h h
1 1
3 ≤ h < 5 h < 3,5
1 0,015 1 0,3
5 ≤ h ≤ 8 h ≥ 3,5
0,025 0,4
1 1
5 Coil springs
5.1 Types of coil spring

All values in the dimensional tables of Clause 8 are based on cylindrical coil springs made of round wire.

The three designs shown in Figures 12 - 14 are common. The use of different spring designs may be

agreed between manufacturer and customer. Changed spring groove configurations and dimensions

could then be necessary.
Key
1 diameter of w ire
Figure 12 — Type CSN coil spring with constant pitch
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ISO 6626-1:2016(E)
Key
1 diameter of w ire
2 approx. 0,8 × diameter of w ire
Figure 13 — Type CSG coil spring with constant pitch (coil diameter, d , ground)
Key
1 diameter of w ire
2 approx. 0,8 × diameter of w ire
Figure 14 — Type CSE coil spring with variable pitch (coil diameter, d , ground)
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ISO 6626-1:2016(E)
Dimensions in millimetres
Key
1 spring gap
2 area w ith small pitch
Latch pin free length
Latch pin fixed length
Figure 15 — Position of area with small pitch
5.2 Coil spring excursion (extended gap)

Coil spring excursion, f , is the distance between the ends of the ring gap, with unstressed ring,

measured in the middle of the spring groove (see Figure 16). The maximum value of f is given in Table

Figure 16 — Coil spring excursion
5.3 Position of coil spring gap and fixing

The spring gap shall be approx. 180° from the gap and the spring gap ends fixed with a connecting or

latch pin.
Table 6 — Coil spring excursion
Dimensions in millimetres
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ISO 6626-1:2016(E)
Nominal diameter f
max.
60 ≤ d < 125 0,13 x d
1 1
125 ≤ d ≤ 200 0,12 x d
1 1
5.4 Material

Coil springs are made of valve spring wire, oil heat-treated. A suitable material for coil spring expanders

is Subclass 62 in accordance with ISO 6621-3.

Springs are available with two different heat set resistance levels (loss of tangential force under load

and temperature):
 standard heat resistance;
 reduced heat set, code WF.

For test conditions and the permissible loss of tangential forces, see ISO 6621-5.

6 Tangential force and nominal contact pressure
6.1 Tangential force, F

The tangential force, F , of coil spring loaded oil control rings is mainly determined by the force of the

spring. The cast iron part itself has a very small tangential force due to its low radial wall thickness and

the decreased ratio “total free gap/nominal diameter”.

The tangential force measurement only can be used because of the flexible design of the cast iron part of

the coil spring loaded oil control rings.
6.1.1 Force factors

Because of the small contribution of the cast iron part in the tangential force, force factors are not

necessary when additional features, materials or both — other than grey cast iron with modulus of

elasticity of 100 GN/m — are being used.
6.1.2 General tangential force, Ft
The tangential force, F , of a spring loaded oil control ring is determined by
a) nominal diameter, d , in millimetres,
, in millimetres, and
b) land width, h

c) required nominal contact pressure, p , in N/mm², calculated from the equation:

𝐹𝐹 = ∙𝑑𝑑 ∙2∙ℎ ∙𝑝𝑝
𝑡𝑡 1 5 0
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ISO 6626-1:2016(E)

The land width, h , depends on the ring type, nominal diameter and ring width. Recommended values

for land width, h , are mentioned for every ring type in Clause 8. Varying values may be agreed between

customer and manufacturer.
6.1.3 Actual tangential force, F , and tolerance

The actual tangential force of a spring loaded oil control ring can be calculated with the tabulated

normalized tangential force, F /d , given in Table 7, according to the required nominal contact pressure,

t 1
p , from the equation:
𝐹𝐹
𝑡𝑡
𝐹𝐹 =� �∙𝑑𝑑
𝑡𝑡 1
𝑑𝑑1

The tolerance on F is the actual value F ± 20 %. Actual values of tangential force should be rounded up

t t
or down in accordance with ISO 6621-4.
7.1.4 Normalized tangential force, Ft/d1

The normalized tangential forces, F /d for different nominal contact pressure, p , are tabulated in

t 1, 0
Table 7.
Table 7 – Normalized tangential forces, Ft/d1
[mm]
0,2 0,2 0,3 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,1 1,3 1,6
0,2
5 8 0 5 0 0 0 0 0 0 0 0 0
Code
[N/
PN2, 2, 0,5 0,6 0,7 0,7 0,8 1,0 1,2 1,5 1,7 2,0 2,2 2,7 3,2 4,0
5 5 0 3 0 5 8 0 5 0 5 0 5 5 5 0
PN2, 2, 0,4 0,5 0,5 0,6 0,7 0,8 1,0 1,2 1,4 1,6 1,8 2,2 2,6 3,2
0 0 0 0 6 0 0 0 0 0 0 0 0 0 0 0
PN1, 1, 0,3 0,3 0,4 0,4 0,5 0,6 0,7 0,9 1,0 1,2 1,3 1,6 1,9 2,4
5 5 0 8 2 5 3 0 5 0 5 0 5 5 5 0
PN1, 1, 0,2 0,2 0,2 0,3 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,1 1,3 1,6
0 0 0 5 8 0 5 0 0 0 0 0 0 0 0 0
PN0, 0, 0,1 0,1 0,1 0,1 0,1 0,2 0,2 0,3 0,3 0,4 0,4 0,5 0,6 0,8
5 5 0 3 4 5 8 0 5 0 5 0 5 5 5 0
6.2 Nominal contact pressure, p

New contact pressure classes are introduced and have replaced the classes of nominal contact pressure

used in ISO 6626:1989 (1. Ed.), which are shown in Annex A for reference.
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ISO 6626-1:2016(E)

The nominal contact pressure, po, has to be chosen to suit the application and requirements regarding

oil consumption and friction losses. The range of the usual nominal contact pressure, po, is given in

Table 7. Varying values may be agreed between customer and manufacturer.
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ISO 6626-1:2016(E)
8 Dimensions
Table 8 —
...