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Varilip
®
-PTFEshaftseal
VARILIP
R
- BUSAK+SHAMBAN PTFE SHAFT SEALS
Description
Standard radial shaft seals have only a limited application
range with respect to pressure, temperature and media
loads due to their elastomer sealing lip. Furthermore they
only have a limited suitability for applications with
inadequate lubrication.
Varilip
R
shaft seals from Busak+Shamban extend this
application range by using modern Turcon
R
materials
developed specially for rotational applications.
Varilip
R
,typeA
Type A is a one-lip seal suitable for use in standard
industrial applications up to p
max
=0.5MPawherea
radial shaft seal would be unable to withstand the
temperature, friction, medium or poor lubrication. Type A
allows high- speed shafts with peripheral speeds of up to
40 m/s to be sealed.
They are characterised in particular by the low friction and
their stick-slip-free running, thus reducing the heat
development and permitting higher peripheral speeds.
The Varilip
R
shaft seal fits into grooves according to
ISO/DIS 16589 and is dimensionally interchangeable
with the shaft seals to DIN 3760 and ISO 6194/1.
The minimal groove size required for Varilip
R
allows its
use as a pressurised seal where the installation of a
mechanical shaft seal would not be possible due to
constructional reasons.
In contrast to the conventional shaft seals, the Varilip
R
seal requires no metallic energising spring.
Metal casing
Elastomer gasket
Sealing lip
Figure 84 Type A
As can be seen fromFigure 84, dynamic sealing is effected
by the radial load of the sealing lip against the shaft. Static
sealing is effected on the one hand by a press fit of the
metallic casing in the housing bore and, on the other, by
an elastomeric flat gasket between metallic housing and
Tur con
R
sealing lip.
Varilip
R
,typeB
Type B is the preferred choice for applications in which a
high sealability is demanded or where contaminated
media are to be sealed. This two-lip type offers greater
safety than the Type A.
Metal casing
Elastomer gasket
Sealing lip
Figure 85 Type B
175
Varilip
®
-PTFEshaftseal
Varilip
R
,typeC
This table is intended to allow the designer a quick
preselection of the most favourable seal type and the
optimum material for his specific application.
The Varilip
R
Type C can be used for applications involving
higher pressures for which a simple elastomer radial shaft
seal can no longer to be considered. Due to a
reinforcement of the sealing lip, pressures of up to 2 MPa
are possible, e.g. as pump, shaft or rotor seals.
Advantages
-
Low friction seal material
-
Stick-slip free running
-
Low and high temperature range (-60 to +200 ºC)
Metal casing
-
High pressure capability (2 MPa)
-
High speed ability (40 m/s)
-
Wide media compatibility
-
Not affected by chemicals
Elastomer gasket
-
Fits standard oil seal installation groove
Sealing lip
Technical data
Coaxiality tolerance
In order to achieve a uniform radial load of the sealing lip
on the surface of the shaft, the best possible coaxiality
should exist between shaft and housing bore.
Figure 86 Type C
Varilip
R
,typeD
The maximum permissible coaxial deviation as a function
of shaft diameter is shown in Figure 88.
Whilst Types A to C can be used to seal against pressures
from only one side, Type D can be subjected to pressure
from both sides. Pressures of up to 0.1 MPa are
permissible. The separation of two different media using
a single seal is possible. The second lip can also take on
the function of a wiper or dust lip.
0.15
0.10
0.05
0
Metal casing
0 0 0 0 0
100 120
120
120 140
0
Shaft diameter-
mm
Elastomer gasket
Figure 88 Coaxiality tolerance
Sealing lip
Figure 87 Type D
Table I summarises the important technical data and
selection criteria for the different Varilip
R
types.
Furthermore it gives an overview of the most significant
applications in which the various Varilip
R
types have
already proven themselves in practice.
176
Varilip
®
-PTFEshaftseal
Shaftrunouttolerance
In order to maintain the sealing function, the shaft
eccentricity as a function of the speed must be limited as
shown in Figure 89.
Torque
Figure 91 shows the torque as a function of the operating
pressure for various Varilip
R
types and Turcon
R
materials
for a shaft diameter of 50 mm. The torque for other shaft
diameters can be roughly calculated from the formula
2
5
Mx
d
50 mm
M
[Nm]
0.15
0.10
0.05
1.0
0
Ty p e B and C, T25
0
1000
2000
3000 4000
4000
5000
6000
0.8
Speed min
-1
Ty p e A , T78
0.6
Figure 89 Max. shaft runout
0.4
Ty p e A , T25
Power consumption, dry running
Guide values for the frictional power consumption can be
determined from the curve in Figure 90. It is plotted as a
function of surface speed and operating pressure for a
shaft diameter of 50 mm for a Varilip
R
type A and lip
material T25.
0.2
0
0
0.2
0.4
0.6
0.8
Pressure MPa
Guide values for other shaft diameters can be calculated
from the formula
Figure 91 Torque on a 50 mm shaft-
5
px
d
50 mm
[W]
p
600
500
400
300
200
100
0
0
5
10
15
20
Speed m/s
Figure 90 Power consumption on a 50 mm shaft-
177
Varilip
®
-PTFEshaftseal
Application examples
Varilip
R
is preferably used as a single acting seal for
rotating hydraulic and pneumatic equipment in sectors
such as:
-
Pumps
-
Separators
-
Blowers
-
Centrifuges
-
Gearboxes
-
Machine tools
-
Hubs
-
Mixers
-
Bearings
-
Marine
Application Limits
The limits for temperature, pressure and speed given in
this catalogue cannot be fully exploited at the same time.
Furthermore, the lubrication properties, the media, the
heat dissipation and the condition of the shaft surface
affects the application limits.
The following p x v values can be used as general
guidelines:
For shaft diameter from 30 mm to 170 mm:
up to
1.5 (MPa x m/s) with poor lubrication
up to
3.0 (MPa x m/s) with good lubrication
up to
10.0 (MPa x m/s) with very good cooling
For smaller shaft diameters, the values must be reduced.
178
Varilip
®
-PTFEshaftseal
Materials
An important factor for the proper function of rotational
seals is the material. For this reason, Busak+Shamban
has developed a range of specially modified materials for
rotational applications on the basis of the proven Turcon
R
materials. Particular importance was attached to the
optimisation of friction and wear properties, even at high
peripheral speeds.
Figure 92 shows the standard materials used for Varilip
R
seals.
Stainless steel casing
Elastomer gasket
Stainless steel
inner casing
Tur con
R
sealing lip
Figure 92 Materials for Varilip
R
seals
Table LVII Turcon
R
materials for Varilip
R
Material,
Applications,
Properties
Code
Operating temp.
Mating surface
hardness
MPa
C
max.
Turcon
T25
T25
-60 to +200
Min. 55 HRC
2
St
Standard material with exceptional wear and friction characteristics.
For lubricated or dry running.
d d
t
i
l
ith
ti
l
d f i ti
h
t
i ti
At low pressure and
d
For lubricated or dry running.
Glass fiber, lubricant
Colour: Grey
p
speeds up to 4 m/s,
ahardnessof45HRC
t 4
/
Colour: Grey
a hardness of 45 HRC
is acceptable
Turcon
T40
For all lubricating and non lubricating fluids Used for medium hard
T40
-60 to +200
Min. 30 HRC
2
For all lubricating and non-lubricating fluids. Used for medium hard
shafts in applications where there is risk for shaft wear.
C b fib
Carbon fiber
Colour: Grey
Turcon
R
T78
Characterized by particular good running behaviour. This permits use in dry
running applications, applications with poor lubrication and in conjunction
ith
T78
-60 to +200
Min. 170 HB
0.2
with soft shaft surfaces e.g. in applications where stainless steel is standard,
like food stuff, pharmaceutical and chemical industries.
Aromatic polymer
Colour: Tan to dark brown
Other Turcon
ft h ft
f
i
li
ti
h
t i l
t
l i
t d d
R
lip materials are available, simply by using the relevant Turcon
R
material code when ordering.
Highlighted materials are standard.
Table LVIII Casing materials
Table LIX Materials for gasket elastomers
Medium
Material
Material Code
Medium
Temperature
Material
Code
Oils, greases,
air/gases,water,
vapour,solvents,
foodstuffs
Stainless steel
Material No. 1.4301
AISI 304
1
A i r,wa t e r,
oils’greases
Nitrile-Elastomer
- 30 to + 110
NBR
N
C
A i r,wa t e r,
vapour,
foodstuffs,
alcohols
Ethylene-propylene-
elastomer
- 60 to + 150
EPDM
E
Acids,
caustics,
seawater
Acid-resistant stainless steel
Material No. 1.4436
AISI 316
C
2
A i r,wa t e r, o i l s ,
greases,
solvents,acids,
caustics
Fluoroelastomer
- 20 to + 200
FKM
V
Acid-resistant stainless steel
Material No. 1.4571
AISI 316 Ti
C
3
*
)
*
)
Only for type
A
,
C
and
D
up to max. 90 mm outside
diameter.
179
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