Carbon and Graphite
Material for Specialty Seals
This information is based on our present state of knowledge and is intended to provide general notes on our
products and their uses. It should not
therefore be construed as guaranteeing
specific properties of the products
described or their suitability for a particular application. Any existing industrial property rights must be observed.
The quality of our products is guaranteed under our General Conditions of
Sale.
02 02/3E Printed in Germany
Graphite Specialties
Business Unit
SGL CARBON GmbH
Werk Ringsdorff
Drachenburgstraße 1
D-53170 Bonn
Phone: +49 (228) 841-394
Fax:
+49 (228) 841-456
Internet: www.sglcarbon.com
Specialty Graphites from SGL CARBON
Piston and Guide Rings
S
S
U
U
S
H 10
Ring – Ø
The inner diameter of the bearing
ring depends on the thermal expansion of the piston groove diameter
°
45
S
W
a
Tol.
e7…f8
Notch – Ø
Ring – Ø
f7…f8
Ring – Ø
H7
Cylinder – Ø
b -0.1
-0.2
with mechanical play
between the segment contacts h 7 … h 8
h7
Guide Rings
segmented with
butt joints *)
Piston Ring
segmental with scarf, overlapping
and lapped tenon joints
without mechanical play
between the segment contacts h7... h8
h
f7…f8
W
h
H7 … H8
B
H7 … H8
Ring – Ø
A
Sp
Radial Seals and Packings
Dimensioning
Radial seals are classified as
contact seals and as contact free,
grooved split seals. Contact seals
are multi-segmented sealrings
used for rotating shafts or linear
motion pistons. The sealing
effect is obtained with springs
that press the carbon segments
to the sealed surface. Contact
seals continuously rub against a
counterface material and as such
are always subject to mechanical
wear. Grooved seals are designed
as single part or multi-segment
rings which require a precisely
defined clearance to the sealed
shaft.
The use of multiple stacked
packings, creates a labyrintheffected which can result in
additional sealing functionality.
Frequently the initial run-in
wear, removes most of the mechanical play between the segment contacts. In these cases
packings can obtain the characteristics of a contact free grooved
seal with minimal loss of sealing
effect.
segmented with
butt joints
segmented with
lapped joints
Packings
The number of segments is
dependant on the diameter of
the shaft. There is no limit to
the number of segments.
Turbine seals provide water as
a lubrication medium and are
subject to very low wear rates
at very high rubbing speeds.
2
Typical applications are multisegmented packings to seal
shafts on ventilators, ship-propellers and water turbines.
segmented with
lapped tenon joints
Technical Information:
The optimal contact pressure
is 0.01 – 0.015 N/mm2 .(PSI). The
surface roughness of the cylinder wall should be Rt < 0.8 µm
inches. The maximum speed is
V = 4 m/s. Determining the
number of rings: z ≈ (sp x 0.2) x
1.5 sp compressed air [bar]
Cylinder
Ø
Piston Ring
h
w
b
Lapped
Segments
U
Guide Ring
h
w
Segments
A
Backing Ring
a*
bis 24
b
Piston
Clearance
Sp
0.2
6
5
6
6
10
6
10
25 - 30
6
0.3
0.6
31 - 40
7
7
6
0.4
7
12
8
12
7
41 - 50
0.5
8
51 - 60
0.6
8
8
8
61 -- 80
3
14 10 14
10
2
81 - 100
0.8
0.9
1
10 10 10
12
18 12 18
10
101 - 120
1.25
121 - 150
1.5
12 12 12
14
20 15 20
1.2
12
151 - 200
2
201 - 250 14 18 14
16
24 18 24
251 - 300 16 20 16
18
26 20 26
3
35 23 35
4
2.5
14
3
16
4
18
5
20
1.5
301 - 350 18 22 18
20
351 - 400
4
2
24
20
401 - 450
25
451 - 500 22
22
5
22
26
40
5
40
22
2.5
6
501 - 550
28
24 28 24
6
24
551 - 600
6
25
601 - 700 25 30 25
7
8
30
3
25
* The dimensious listed apply to backing rings of spring bronze SnBz 6 HV 160 / DIN 1780. When using other spring materials,
dimensious should give a maximum pressure between piston ring and cylinder wall of p = 0.01– 0.015N/mm2 .
3
For horizontal machines + 0.5 mm
Radial Seals
Piston and guide rings used in oilfree compressors are an ideal application for carbon-graphite or
graphite materials. The material is
effective on a wide temperature
range. Wear rates increase progressively once temperatures fall below
-20°F. The sealing effect is obtained by pressing the pistonring-segments against the cylinder wall with a leaf-spring located in the piston groove. The
springs are necessary because
unlike metals, graphite cannot
be manufactured with tensile
spring effect. Guide rings locate
the piston centrally. The guide
rings make contact with the
groove and the cylinder wall.
Specialty Graphites from SGL CARBON
Pistonrod Seals and
Labyrinth Seals
Pistonrod seals
Labyrinth seals
Pistonrod seals are used to
seal the linear movement of
the pistonrods. Segment rings
are used in pairs to achieve
additional axial sealing. The
segments have overlapping
shoulders. Pins or springs
secure the rings in position.
The shaft surface roughness
should be Rt ≤ 1 µm. We have
the ability to supply springs or
pins based on your requirements along with the seals.
Labyrinth seals made with
SGL CARBON self lubricating materials, have the advantage over metals in that short
periods of contact during startup due to differences in the
coefficients of thermal expansion do not cause damage. As a
result the labyrinth gaps can be
smaller in size on a carbongraphite seal as compared to a
metal seal. Consequently, given
the same performance requirements a carbon-graphite seal
can be shorter than a metal seal.
Metal Sleeved Rings and other Seals/
Ball Valve Seals
Metal sleeved rings
One piece carbon rings are used
as metal sleeved seals in compressors, when the carbon has been
heat shrunk into a metal casing.
The compressed carbon seal
enables designs using very small
tolerances on the seal gap. The
gap remains constant under
varying operating temperatures.
The design of the metal casing
has to be closely toleranced for
dimension and form stability
since any undesirable deformations will tend to transfer onto
the seal surface of the carbon
even if the carbon is machined
after the heat shrinking operation. The wall thickness of the
metal casing should be approximately 3 % of the seal outer
diameter and should be a minimum of 2 mm. The shrinkfit
between carbon seal and metal
casing is dependent on the
operating temperature and can
be between H7/x8 and H7/zb8.
We will supply the metal casing
based on your requirements.
Other seals/
Ball valve seals
Ball valve seals made of carbongraphite are used to seal hot
gases and steam in chemical
process. Other materials fail
in these environments due to
the high temperature. Carbongraphite ball valve seals are
used in the petrol-chemical
industry, refineries and on oil
tankers where in the case of
on-board fire, the seal must
maintain it is functionality.
Designs with metal casings
can be produced based on
your particular needs.
Forms
4
5
Specialty Graphites from SGL CARBON
Steam Joints,
Motion Control Rings and Segments
Material References
Carbon-Graphite
not
resin-
Graphite
antimony-
impregnated impregnated impregnated
not
resin-
antimony-
impregnated
impregnated
impregnated
EK 40
EK 203
1. Packings for
• Hydro-power
EK 24
EK 2243
• Ventilators
EK 40
• Propeller
EK 40
EK 305
shafts
Steam joints
Motion control rings
and segments
• Turbo
compressors
Steam joints are sealing components between a steam pipe and
a rotation assembly such as a
shaft, cylinder or roller. The
joint seals water, steam and oils.
Further it neutralises swing,
pendular and tumbling motion.
This functionality is normally
achieved with a concave or
convex seal ring surface which is
pressed against the sealing surface with a spring. Certain configurations also have a cylindrical
wearing surface. Steam joints are
exposed to all known lubrication
conditions including wet, mixed
and dry running.
Motion control rings and segments regulate automated production processes. Applications
include cigarette production
equipment and packaging machines. The use of graphite, eliminates oil based lubrication, an
important advantage as the
intermittent swivelling motion
usually precludes the use of a
hydrodynamic lubrication system.
2. Piston- and guide-rings
Piston rod seals
• Piston compressors
EK 2240
EK 3245
3. Labyrinth seals
EK 40
4. Metal sleeve rings
EK 40
EK 201
EK 305
EK 201
EK 305
EK 305
EK 305
5. Ball value seals
6. Steam joint rings
6
EK 305
EK 40
EK 20
EK 2200
EK 3205
7