ISO 6623:2004
(Main)Internal combustion engines — Piston rings — Scraper rings made of cast iron
Internal combustion engines — Piston rings — Scraper rings made of cast iron
ISO 6623:2004 specifies the essential dimensional features of scraper rings made of cast iron, types N, NM, E and EM, having diameters of from 30 mm up to and including 200 mm, used in reciprocating internal combustion engines. It is also applicable to piston rings of compressors working under similar conditions.
Moteurs à combustion interne — Segments de piston — Segments racleurs mixtes en fonte moulée
General Information
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 6623
Second edition
2004-02-01
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 6623:2004(E)
©
ISO 2004
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ISO 6623:2004(E)
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ii © ISO 2004 – All rights reserved
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ISO 6623:2004(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references. 1
3 Overview. 1
4 Ring types and designation examples. 2
4.1 Types N, NM, E and EM Scraper rings — General features. 2
4.2 Type N. 3
4.2.1 Napier ring (undercut step). 3
4.2.2 Designation. 3
4.3 Type NM. 4
4.3.1 Napier ring (undercut step) taper faced. 4
4.3.2 Designation. 4
4.4 Type E. 5
4.4.1 Scraper ring (stepped). 5
4.4.2 Designation. 5
4.5 Type EM. 6
4.5.1 Scraper ring (stepped) taper faced . 6
4.5.2 Designation. 6
5 Common features. 7
5.1 Type N, NM, E and EM rings — Inside chamfered edges KI. 7
5.2 Type NM and EM rings with a partly cylindrical machined (LM) or lapped (LP) peripheral
surface at the bottom running edge. 8
5.3 Type N, NM, E and EM rings chromium plated/spray coated. 9
5.3.1 Chromium plated NM and EM rings . 9
5.3.2 Spray coated (inlaid design) N, NM, E and EM rings. 9
6 Force factors. 10
7 Dimensions. 12
Bibliography . 28
© ISO 2004 – All rights reserved iii
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ISO 6623:2004(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 6623 was prepared by Technical Committee ISO/TC 22, Road vehicles.
This second edition cancels and replaces the first edition (ISO 6623:1986), which has been technically revised.
iv © ISO 2004 – All rights reserved
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ISO 6623:2004(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]
ISO 6625 , ISO 6626 and ISO 6627 (see Bibliography for details).
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 selection.
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INTERNATIONAL STANDARD ISO 6623:2004(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 of from 30 mm up to and including 200 mm, used in reciprocating
internal combustion engines. It is also applicable to piston rings of compressors working under similar
conditions.
2 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 6621-4, 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 two radial wall thicknesses:
radial wall thickness “regular”;
radial wall thickness “D/22”.
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ISO 6623:2004(E)
4 Ring types and designation examples
4.1 Types N, NM, E and EM Scraper rings — General features
The general features of type N, NM, E and EM scraper rings are shown in Figure 1.
NOTE See Tables 8 and 9 for dimensions and forces.
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
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ISO 6623:2004(E)
4.2 Type N
4.2.1 Napier ring (undercut step)
The general features of type N Napier rings with undercut step shall be in accordance with Figures 1 and 2,
except for rings h < 1,5 mm.
1
Key
1 reference plane
2 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)
Table 1 — r dimensions
2
Dimensions in millimetres
r
2
d
1
max.
30 u d < 175 0,3
1
175 u d u 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 straight faced peripheral surface (N), of nominal diameter d = 90 mm (90), of radial wall thickness “regular”, of
1
nominal ring width h = 25 mm (2,5), made of non-heat-treated grey cast iron subclass 12 (MC12), with chamfered internal
1
edges (KI):
Piston ring ISO 6623 N - 90 ×××× 2,5 - MC 12/K I
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ISO 6623:2004(E)
4.3 Type NM
4.3.1 Napier ring (undercut step) taper faced
The general features of type NM Napier rings with 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 mark
a
See Table 1.
Figure 3 — Type NM (Detail X of Figure 1)
Table 2 — Taper
Dimensions in minutes
Uncoated rings and chromium plated or spray coated rings
Code with peripheral surface ground
a
Taper Tolerance
M2 30
M3 60 +60
M4 90 0
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 “regular”, of
1
ring width h = 2,5 mm (2,5), made of heat-treated grey cast iron, subclass 21 (MC21), phosphated on all sides (PO):
1
Piston ring ISO 6623 NM4 - 90 ×××× 2,5 - MC21/PO
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ISO 6623:2004(E)
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 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)
4.4.2 Designation
EXAMPLE Designation of a piston ring complying with the requirements of ISO 6623, being a cast iron scraper ring
with straight faced peripheral surface (E), of nominal diameter d = 90 mm (90), of nominal ring width h = 2,5 mm (2,5),
1 1
radial wall thickness “regular”, made of non-heat-treated grey cast iron, subclass 12 (MC12), 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
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ISO 6623:2004(E)
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 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 h = 2,5 mm
1 1
(2,5), of radial wall thickness “regular”, made of heat-treated grey cast iron, subclass 22 (MC22), with inside chamfered
edges (KI):
Piston ring ISO 6623 EM2 - 90 ×××× 2,5 - MC22/KI
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ISO 6623:2004(E)
5 Common features
5.1 Type N, NM, E and EM rings — Inside chamfered edges KI
Dimensions in millimetres
a) For nominal KI WWWW 0,3
b) For nominal KI << 0,3
<<
Key
1 mark
Figure 6 — Inside chamfered edges KI
Table 3 — KI dimensions
Dimensions in millimetres
d
KI
1
30 u d < 50 0,2 max.
1
a
50 u d < 125 0,3 ± 0,15
1
125 u d < 175 0,4 ± 0,15
1
175 u d u 200 0,6 ± 0,15
1
a
KI = 0,2 max for rings h < 1,5 and 50 < d < 60.
1 1
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ISO 6623:2004(E)
5.2 Type NM and EM rings with a partly cylindrical machined (LM) or lapped (LP) peripheral
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 30º 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 u h u 4
1,1 1,8
1
a
Partly cylindrical peripheral surface shall be visible.
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ISO 6623:2004(E)
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
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
Chromium plating Spray coating min.
CRF — 0,005
CR1 SC1F 0,05
CR2 SC2F 0,1
— SC3F 0,15
— SC4F 0,2
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ISO 6623:2004(E)
6 Force factors
The tangential and diametral forces given in Tables 8 and 9 shall be corrected when additional features and/or
2
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 of Table 7 have been calculated with mean coating thickness.
Table 6 — Force correction factors for N, NM, E and EM rings with feature KI
d
1
Factor
mm
30 u d < 50 1
1
50 u d u 200 0,97
1
Tableau 7 — Force correction factors for N, NM, E and EM rings chromium plated (fully faced type)
and spray coated (inlaid type)
d
Factor
1
mm CRF CR1 CR2 SC1F SC2F SC3F SC4F
30 u d < 50 1 0,84 0,77 0,89 0,85 — —
1
50 u d < 75 1 0,91 0,85 0,92 0,90 0,87 0,86
1
75 u d < 100 1 0,94 0,92 0,94 0,92 0,90 0,87
1
100 u d < 125 1 0,97 0,94 0,94 0,93 0,91 0,89
1
125 u d < 150 1 0,98 0,96 0,95 0,93 0,91 0,90
1
150 u d u 200 1 1 0,97 0,95 0,94 0,93 0,91
1
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ISO 6623:2004(E)
(Blank page)
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ISO 6623:2004(E)
7 Dimensions
Table 8 — Dimensions for Type N, NM, E and EM scraper rings (radial wall thickness “regular”)
Radial wall
Nominal
thickness Ring width Closed gap Axial width of step
diameter
“regular”
d a h s h
1 1 1 1 2
mm mm mm mm mm
(Tolerance ± 0,15)
Tolerance Column Tolerance Tolerance for h shown in Column
1
1 2 3 4 5 1 2 3 4 5
30 1,25
31 1,3
32 1,35
33 1,4
34 1,4
35 1,45
36 1,5
37 1,55
38 1,6
39 1,65
40 1,65
41 1,7
42 1,75
−0,01
−0,03
43 1,8
For
± 0,15 0,15
44 1,85
phos-
Within a 1,2 1,5 1,75 2 2,5 + 0,2 0,35 0,4 0,45 0,5 0,6
phated PO
45 1,9 ring: u 0,15 0
surface:
46 1,9 −0,005
−0,03
47 1,95
48 2
49 2,05
50 2,1
51 2,15
52 2,15
53 2,2
54 2,25
55 2,3
56 2,35
57 2,4
58 2,4
59 2,45
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ISO 6623:2004(E)
Table 8 (continued)
Radial depth of step Tangential force Diametral force
a F F
2 t d
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
0,3 0,3 0,3 0,3 0,3 ± 0,15 — — — — —
5,8 7,3 8,6 9,9 12,3
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
F < 10 N F < 21,5 N
t d
± 20 % if ± 20 % if
8,2 10,1 12,0 13,8 17,4
F W 10 N F W 21,5 N
t d
7,7 9,7 11,4 13,1 16,6
0,45 0,45 0,45 0,45 0,45 ± 0,15 — — — — — 8,0 10,1 11,8 13,8 17,2
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 9,9 12,5 14,6 16,8 21,3
0,55 0,55 0,55 0,55 0,55 ± 0,15
4,8 6,0 7,0 8,1 10,2 10,3 12,9 15,1 17,4 21,9
4,6 5,8 6,8 7,8 9,8 9,9 12,5 14,6 16,8 21,1
4,7 5,9 7,0 8,0 10,1 10,1 12,7 15,1 17,2 21,7
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ISO 6623:2004(E)
Table 8 (continued)
Radial wall
Nominal
thickness Ring width Closed gap Axial width of step
diameter
“regular”
d a h s h
1 1 1 1 2
mm mm mm mm mm
(Tolerance ± 0,15)
Tolerance Column Tolerance Tolerance for h shown in Column
1
1 2 3 4 5 1 2 3 4 5
60 2,5
61 2,55
62 2,6
63 2,65
64 2,65
65 2,7
66 2,75
0,2
+ 0,2
67 2,8
0
68 2,85
2,9
70 2,9
71 2,95
72 3,00
73 3,05
74 3,1
1,2 1,5 1,75 2 2,5 0,35 0,4 0,45 0,5 0,6
− 0,01
75 3,15
− 0,03
76 3,15 For
± 0,15
phos-
Within a
77 3,2
phated PO
ring: u 0,15
surface:
78 3,25
− 0,005
79 3,3
− 0,03
80 3,35
81 3,4
0,25
+ 0,25
82 3,4
0
83 3,45
84 3,5
85 3,55
86 3,6
87 3,65
88 3,65
89 3,7
90 3,75
91 3,8
0,3
92 3,85 1,5 1,75 2 2,5 3 + 0,25 0,4 0,45 0,5 0,6 0,75
0
93 3,9
94 3,9
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ISO 6623:2004(E)
Table 8 (continued)
Radial depth of step Tangential force Diametral force
a F F
2 t d
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
4,8 5,8 6,9 8,0 10,1 10,3 12,5 14,8 17,1 21,7
5,0 6,0 7,1 8,2 10,4 10,8 12,9 15,3 17,6 22,4
5,1 6,2 7,3 8,4 10,7 11,0 13,3 15,7 18,1 23,0
5,2 6,4 7,5 8,7 11,0 11,2 13,8 16,1 18,7 23,7
5,1 6,2 7,3 8,4 10,6 11,0 13,3 15,7 18,1 22,8
5,2 6,3 7,5 8,6 10,9 11,2 13,5 16,1 18,5 23,4
5,4 6,5 7,7 8,9 11,2 11,6 14,0 16,6 19,1 24,1
0,6 0,7 0,7 0,7 0,7 ± 0,15
5,5 6,7 7,9 9,1 11,5 11,8 14,4 17,0 19,6 24,7
5,6 6,9 8,1 9,4 11,8 12,0 14,8 17,4 20,2 25,4
5,8 7,1 8,3 9,6 12,1 12,5 15,3 17,8 20,6 26,0
5,6 6,8 8
...
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