Gasket splitter determination
Supporting body
When shafts are rotating, the sealing lip of a pressurized radial shaft seal is twisted, resulting in high shear stresses in the elastomers. These shear stresses are a function of the pressure, the circumferential speed, the coefficient of friction and the annular gap (distance ds – see Figure 2). If the distance ds is too large, this can lead to material burns and shearing of the sealing lips during operation. The distance ds is therefore a decisive and influential factor in whether a seal holds under the specified pressure and the specified circumferential speed or is destroyed.
VR RWDR are offered with different dimensions D3(or D4) of the support bodies. The purpose is to take different pressure ranges into account (see chapter Column extrusion).
BOB design
In the VR sealing system, this distance ds is taken into account by the supporting body bore dimensions D3 or D4. As standard, the D4 dimension of the punched metal parts is D1 + 0.5 mm and the D3 dimension is D1 + 1.0 mm. Higher and dynamic pressures require smaller distances ds.
Note: ds = (D3 – D1) / 2 or ds = (D4 – D1) / 2
Area 1 Support body with D3 dimension
Area 2 Supporting body with D4 dimension
Range 3 support bodies with ds dimension adapted to your application.
Remark:
- Support bodies are available in steel and stainless steel (1.4301) or special materials. Please contact us if you have applications in area III.
- For distances ds < 0.15, gunmetal (RG7) is recommended as a support body material to prevent damage to the axle.
- For higher pressure loads on seals, it is necessary to keep the gap extrusion as small as possible. For this purpose, it is necessary to switch from stamped metal parts to the one-piece, turned support body design (SOA design).
- Please coordinate your design for high-pressure applications with us at an early stage.
SOA design and its pressure/ds diagram
The SOA support body design allows very small ds distances to be achieved. These in turn are a measure of the maximum pressure load on the seal.
Support body material turned parts are available in:
- Gunmetal (RG7)
- Aluminum
- Stainless steel 1.4301
- Steel 1.0570
The support body dimension Ø D3 should be specified in orders, otherwise the standard dimension is used for production: D3 = shaft Ø + 0.10 + 0.05 – 0.00
for example: Shaft Ø 30 -> D3 = 30.10 + 0.05 – 0.00
If you have any questions, please contact our technical department.
Selection diagrams Speed-pressure ratio
FKM
HNBR
NBR
Permissible speed/pressure ratio
Determined values.
Lubricated sealing lip without additional cooling.
Pressure data for quasi-static condition.
The pressure values must be reduced for impact pressure loads.
Selection diagrams Speed-pressure ratio
Tangential frictional force
ζ(N/m) per meter circumference
P = dπζv / 2000
d = shaft diameter (mm)
v = circumferential speed (m/s)
ζ = tangential frictional force (N/m)
P = Power loss (W)
Friction power
Example:
d = 100 mm, v = 3000 min-1, oil pressure in 0 MPa (unpressurized), HNBR compound, tangential
Read off the friction force in the diagram: approx. 60 N/m
> P = 100 x π x 60 x 15.7 / 2000
> P = 148 W 1
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