ISO 6623:2013

Internal combustion engines — Piston rings — Scraper rings made of cast iron

ISO 6623:2013 specifies the essential dimensional features of scraper rings made of cast iron, types N, NM, E, and EM, having diameters from 30 mm up to and including 200 mm, used in reciprocating internal combustion engines for road vehicles and other applications.

Moteurs à combustion interne — Segments de piston — Segments racleurs mixtes en fonte moulée

General Information

• Status: Published
• Publication Date: 02-Jul-2013
• 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: 9093 - International Standard confirmed
• Completion Date: 21-Oct-2019

Relations

• Revises: ISO 6623:2004 - Internal combustion engines — Piston rings — Scraper rings made of cast iron
• Effective Date: 26-Jul-2010

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 6623
Third edition
2013-07-15
Internal combustion engines — Piston
rings — Scraper rings made of cast iron
Moteurs à combustion interne — Segments de piston — Segments
racleurs mixtes en fonte moulée
Reference number
ISO 6623:2013(E)
©
ISO 2013

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ISO 6623:2013(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2013
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Published in Switzerland
ii © ISO 2013 – All rights reserved

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ISO 6623:2013(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Overview . 1
4 Ring types and designation examples . 1
4.1 Types N, NM, E, and EM scraper rings — General features . 1
4.2 Type N . 2
4.3 Type NM . 3
4.4 Type E . 4
4.5 Type EM . 5
5 Common features . 6
5.1 Type N, NM, E, and EM rings — Inside chamfered edges (KI) . 6
5.2 Type NM and EM rings with a partly cylindrical machined (LM) or lapped (LP) peripheral
surface at the bottom running edge . 7
5.3 Type N, NM, E, and EM rings (chromium plated/spray coated) . 7
5.4 Napier or scraper ring with reduced undercut or step (mini Napier/stepped) [RU] . 8
6 Force factors . 8
7 Dimensions .10
Bibliography .26
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ISO 6623:2013(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.
The committee responsible for this document is ISO/TC 22, Road vehicles.
This third edition cancels and replaces the second edition (ISO 6623:2004), of which it constitutes a
minor revision.
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ISO 6623:2013(E)

Introduction
ISO 6623 is one of a number of series of International Standards dealing with piston rings for reciprocating
[2] [3] [4] [5] [6] [7] [8] [9] [10] [11]
internal combustion engines. Others are ISO 6621, ISO 6622, ISO 6624,
[12] [13] [14] [15] [16]
ISO 6625, ISO 6626, and ISO 6627 (see Bibliography for details).
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INTERNATIONAL STANDARD ISO 6623:2013(E)
Internal combustion engines — Piston rings — Scraper
rings made of cast iron
1 Scope
This International Standard specifies the essential dimensional features of scraper rings made of
cast iron, types N, NM, E, and EM, having diameters from 30 mm up to and including 200 mm, used in
reciprocating internal combustion engines for road vehicles and other applications.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 6621-4, Internal combustion engines — Piston rings — Part 4: General specifications
3 Overview
The scraper ring types are specified in Tables 1 and 2 and Figures 1 to 5. Their common features and
the dimensions of those features are specified in Tables 3 to 5 and Figures 6 to 9. Tables 6 and 7 give
the force factors for the different ring types, while Tables 8 and 9 give the dimensions and forces of the
scraper rings.
Tables 8 and 9, respectively, offer a choice between the following two radial wall thicknesses:
— radial wall thickness “regular”;
— radial wall thickness “D/22”.
The common features and dimensional tables presented in this International Standard constitute a
broad range of variables and the designer, in selecting a particular ring type, shall bear in mind the
conditions under which it will be required to operate.
[4]
It is also essential that the designer refer to the specifications and requirements of ISO 6621-3 and
ISO 6621-4 before completing his/her selection.
4 Ring types and designation examples
4.1 Types N, NM, E, and EM scraper rings — General features
The general features of types N, NM, E, and EM scraper rings are shown in Figure 1.
NOTE See Tables 8 and 9 for dimensions and forces.
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ISO 6623:2013(E)

Key
a See 4.2, 4.3, 4.4, and 4.5 and Figures 2, 3, 4, and 5 for detail X of N, NM, E, and EM, respectively.
Figure 1 — Types N, NM, E, and EM
4.2 Type N
4.2.1 Napier ring (undercut step)
The general features of type N Napier rings with an undercut step shall be in accordance with Figures 1
and 2, except for rings h < 1,5 mm.
1
Key
1 reference plane
2 top side identification mark
a
When the ring is closed, this edge shall be in contact with the cylinder bore.
b
See Table 1.
Figure 2 — Type N (Detail X of Figure 1)
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ISO 6623:2013(E)

Table 1 — r dimensions
2
Dimensions in millimetres
r
2
d
1
max.
30 ≤ d < 175 0,3
1
175 ≤ d ≤ 200 0,7
1
4.2.2 Designation
EXAMPLE Designation of a piston ring complying with the requirements of ISO 6623, being a cast iron Napier
ring with a straight-faced peripheral surface (N), of nominal diameter d = 90 mm (90), of radial wall thickness
1
“regular”, of nominal ring width h = 2,5 mm (2,5), made of non-heat-treated grey cast iron subclass 12 (MC12),
1
and with chamfered internal edges (KI):
   Piston ring ISO 6623 N - 90 × 2,5 - MC12/K I
NOTE Parameters in parentheses are used in the ISO ring designation.
4.3 Type NM
4.3.1 Napier ring (undercut step), taper faced
The general features of type NM Napier rings with an undercut step, taper faced, shall be in accordance
with Figures 1 and 3, except for rings h < 1,5 mm.
1
Key
1 reference plane
2 top side identification mark
a
See Table 1.
Figure 3 — Type NM (Detail X of Figure 1)
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ISO 6623:2013(E)

Table 2 — Taper
Dimensions in minutes
Uncoated rings and chromium-plated or spray-coated rings
with peripheral surface ground
Code
a
Taper Tolerance
M2 30
+60
M3 60
0
M4 90
a
For chromium-plated rings with a tapered peripheral surface that is not ground, the
+70
tolerance shall be increased by 10 (e.g. M3=60 ).
0
4.3.2 Designation
EXAMPLE Designation of a piston ring complying with the requirements of ISO 6623, being a cast iron Napier
ring with a 90′ taper-faced peripheral surface (NM4), of nominal diameter d = 90 mm (90), of radial wall thickness
1
“regular”, of ring width h = 2,5 mm (2,5), made of heat-treated grey cast iron subclass 21 (MC21), and phosphated
1
on all sides (PO):
   Piston ring ISO 6623 NM4 - 90 × 2,5 - MC21/PO
NOTE Parameters in parentheses are used in the ISO ring designation.
4.4 Type E
4.4.1 Scraper ring (stepped)
The general features of type E stepped scraper rings shall be in accordance with Figures 1 and 4.
Key
1 reference plane
2 top side identification mark
a
When the ring is closed, this edge shall be in contact with the cylinder bore.
b
See Table 1.
Figure 4 — Type E (Detail X of Figure 1)
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ISO 6623:2013(E)

4.4.2 Designation
EXAMPLE Designation of a piston ring complying with the requirements of ISO 6623, being a cast iron
scraper ring with a straight-faced peripheral surface (E), of nominal diameter d = 90 mm (90), of nominal ring
1
width h = 2,5 mm (2,5), of radial wall thickness “regular”, made of non-heat-treated grey cast iron subclass 12
1
(MC12), and with an inlaid spray coating on the peripheral surface, and minimum thickness 0,1 mm (SC2F):
   Piston ring ISO 6623 E - 90 × 2,5 - MC12/SC2F
NOTE Parameters in parentheses are used in the ISO ring designation.
4.5 Type EM
4.5.1 Scraper ring (stepped), taper faced
The general features of type EM scraper rings, stepped and taper faced, shall be in accordance with
Figures 1 and 5.
Key
1 reference plane
2 top side identification mark
a
See Table 1.
b
See Table 2.
Figure 5 — Type EM (Detail X of Figure 1)
4.5.2 Designation
EXAMPLE Designation of a piston ring complying with the requirements of ISO 6623, being a cast iron scraper
ring with a 30′ taper-faced peripheral surface (EM2), of nominal diameter d = 90 mm (90), of nominal ring width
1
h = 2,5 mm (2,5), of radial wall thickness “regular”, made of heat-treated grey cast iron subclass 22 (MC22), and
1
with inside chamfered edges (KI):
   Piston ring ISO 6623 EM2 - 90 × 2,5 - MC22/KI
NOTE Parameters in parentheses are used in the ISO ring designation.
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ISO 6623:2013(E)

5 Common features
5.1 Type N, NM, E, and EM rings — Inside chamfered edges (KI)
Dimensions in millimetres
a) For nominal KI ≥ 0,3 b) For nominal KI < 0,3
Key
1 top side identification mark
Figure 6 — Inside chamfered edges (KI)
Table 3 — KI dimensions
Dimensions in millimetres
d KI
1
30 ≤ d < 50 0,2 max.
1
a
50 ≤ d < 125 0,3 ± 0,15
1
125 ≤ d < 175 0,4 ± 0,15
1
175 ≤ d ≤ 200 0,6 ± 0,2
1
a
KI = 0,2 max. for rings 50 < d < 60 and h < 1,5
1 1
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ISO 6623:2013(E)

5.2 Type NM and EM rings with a partly cylindrical machined (LM) or lapped (LP) pe-
ripheral surface at the bottom running edge
a) Feature: machined = Code: LM b) Feature: lapped = Code: LP
Figure 7 — NM and EM rings with partly cylindrical peripheral surface
Table 4 — Axial dimensions of cylindrical part of peripheral surface h
24
Dimensions in millimetres
a a
h h h
1 24 24
max. each side of the gap up to 30° max.
1,2 0,4 0,6
1,5 0,5 0,8
1,75 0,6 1,0
2,0 0,7 1,2
2,5 0,9 1,4
3 ≤ h ≤ 4 1,1 1,8
1
a
Partly cylindrical peripheral surface shall be visible.
5.3 Type N, NM, E, and EM rings (chromium plated/spray coated)
5.3.1 Chromium-plated NM and EM rings
a) NM rings b) EM rings
Figure 8 — Plating thickness
5.3.2 Spray-coated (inlaid design) N, NM, E, and EM rings
NOTE Not recommended for rings h < 1,5 mm.
1
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ISO 6623:2013(E)

a) N rings b) NM rings c) E rings d) EM rings
Figure 9 — Coating thickness
Table 5 — Plating/coating thickness
Dimensions in millimetres
Code
Thickness
min.
Chromium plating Spray coating
CRF — 0,005
CR1 SC1F 0,05
CR2 SC2F 0,1
— SC3F 0,15
— SC4F 0,2
5.4 Napier or scraper ring with reduced undercut or step (mini Napier/stepped) [RU]
A Napier or scraper ring with reduced undercut (mini Napier/stepped) rings [Code RU] has the following
undercut dimensions:
— a and h is 0,5 times the value given in Tables 8 and 9.
2 2
— F and F is 1,085 times the F and F given in Tables 8 and 9.
t d t d
5.4.1 Designation
EXAMPLE Designation of a piston ring complying with the requirements of ISO 6623, being a cast iron scraper
ring with a 30′ taper-faced peripheral surface and a reduced undercut (EM2RU), of nominal diameter d = 90 mm
1
(90), of nominal ring width h = 2,5 mm (2,5), of radial wall thickness “regular”, made of heat-treated grey cast
1
iron subclass 22 (MC22), and with inside chamfered edges (KI):
   Piston ring ISO 6623 EM2RU - 90 × 2,5 - MC22/KI
NOTE Parameters in parentheses are used in the ISO ring designation.
6 Force factors
The tangential and diametral forces given in Tables 8 and 9 shall be corrected when additional features
2
and/or materials other than grey cast iron with a modulus of elasticity of 100 GN/m are being used.
For general features, the multiplier factors given in Tables 6 and 7 and the force correction factors
according to ISO 6621-4 shall be used.
NOTE The factors in Table 7 have been calculated with mean coating thickness.
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ISO 6623:2013(E)

Table 6 — Force correction factors for N, NM, E, and EM rings with feature KI
d
1
Factor
mm
30 ≤ d < 50 1
1
50 ≤ d ≤ 200 0,97
1
Table 7 — Force correction factors for N, NM, E, and EM rings chromium plated (fully faced
type) and spray coated (inlaid type)
Factor
d
1
mm
CRF CR1 CR2 SC1F SC2F SC3F SC4F
30 ≤ d < 50 1 0,84 0,77 0,89 0,85 — —
1
50 ≤ d < 75 1 0,91 0,85 0,92 0,90 0,87 0,86
1
75 ≤ d < 100 1 0,94 0,92 0,94 0,92 0,90 0,87
1
100 ≤ d < 125 1 0,97 0,94 0,94 0,93 0,91 0,89
1
125 ≤ d < 150 1 0,98 0,96 0,95 0,93 0,91 0,90
1
150 ≤ d ≤ 200 1 1 0,97 0,95 0,94 0,93 0,91
1
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ISO 6623:2013(E)

7 Dimensions
Table 8 — Dimensions for Type N, NM, E, and EM scraper rings (radial wall thickness “regular”)
a
Nominal Radial wall Ring width Closed gap Axial width of step
d a h s h
1 1 1 1 2
mm mm mm mm mm
  (Tolerance ± 0,15)
 Tolerance Column Tolerance Tolerance for h1 shown in Column
  1 2 3 4 5  1 2 3 4 5
30 1,25
31 1,30
32 1,35
33 1,40
34 1,40
35 1,45
36 1,50
37 1,55
38 1,60
39 1,65
40 1,65
41 1,70
42 1,75
−0,01
−0,03
43 1,80
For
± 0,15
44 1,85 phosphated
+ 0,2
Within a 1,2 1,5 1,75 2 2,5 0,15 0,35 0,4 0,45 0,5 0,6
PO
0
45 1,90
ring: ≤ 0,15
surface:
46 1,90
−0,005
−0,03
47 1,95
48 2,00
49 2,05
50 2,10
51 2,15
52 2,15
53 2,20
54 2,25
55 2,30
56 2,35
57 2,40
58 2,40
59 2,45
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ISO 6623:2013(E)

Table 8 — (continued)


a2 Ft Fd
mm N N

for h shown in Column Tolerance for h shown in Column Tolerance for h shown in Column Tolerance
1 1 1
1 2 3 4 5 1 2 3 4 5 1 2 3 4 5

5,2 6,5 7,7 8,8 11,0
5,4 6,9 8,2 9,2 11,6
5,8 7,3 8,6 9,9 12,3
0,3 0,3 0,3 0,3 0,3 ± 0,15 — — — — —
6,0 7,7 9,0 10,3 12,9
5,6 7,3 8,4 9,7 12,3
5,8 7,5 8,8 10,1 12,7
6,2 8,0 9,2 10,5 13,3
0,3 0,35 0,35 0,35 0,35 ± 0,15 — — — — — 6,5 8,2 9,7 11,2 14,0
6,9 8,6 10,1 11,6 14,6
7,1 9,0 10,5 12,3 15,3
6,7 8,4 9,9 11,4 14,4
6,9 8,8 10,3 11,8 15,1
0,4 0,4 0,4 0,4 0,4 ± 0,15 — — — — — 7,3 9,2 10,8 12,5 15,7
7,5 9,7 11,2 12,9 16,3
± 30 % if ± 30 % if
8,0 9,9 11,6 13,3 17,0
Ft < 10 N Fd < 21,5 N
± 20 % if ± 20 % if
8,2 10,1 12,0 13,8 17,4
Ft ≥ 10 N Fd ≥ 21,5 N
7,7 9,7 11,4 13,1 16,6
0,4
8,0 10,1 11,8 13,8 17,2
0,45 0,45 0,45 0,45 ± 0,15 — — — — —
5
8,4 10,5 12,3 14,2 17,8
8,6 11,0 12,9 14,6 18,5
4,1 5,2 6,1 7,0 8,8 8,8 11,2 13,1 15,1 18,9
4,3 5,3 6,3 7,2 8,1 9,2 11,4 13,5 15,5 19,6
0,5 0,5 0,5 0,5 0,5 ± 0,15 4,1 5,1 6,0 7,0 8,8 8,8 11,0 12,9 15,1 18,9
4,2 5,3 6,3 7,2 9,1 9,0 11,4 13,5 15,5 19,6
4,4 5,5 6,5 7,4 9,4 9,5 11,8 14,0 15,9 20,2
4,5 5,6 6,6 7,6 9,6 9,7 12,0 14,2 16,3 20,6
4,6 5,8 6,8 7,8 9,9 9
...