TBCW

Dimensions

Installation drawing

Materials

Metal cage - Spring

The table below shows the materials that we can offer for metal cages and springs.

Rubbers

ACM (Polyacrylate)

Polymers containing ethyl acrylate (or butyl acrylate) have a small amount of monomer, which is necessary for cross-linking; ACM is a material with better heat resistance than NBR. It is often used for automatic gearboxes.

AEM (ethylene acrylate rubber)

As a methyl acrylate and ethylene copolymer, AEM is considered to be more resistant to heat than ACM. Its characteristics make it an intermediary between ACM and FKM.

CR (Polychloroprene)

This CR-based rubber is used in the refrigeration industry and for ventilation systems. This chloroprene was the first synthetic rubber to be developed and marketed.

EPDM (Ethylene Propylene Diene Monomer rubber)

As an Ethylene Propylene Diene Monomer copolymer, EPDM is commonly used for hot water taps, cooling systems, brake systems, dishwashers and washing machines.

FFKM (perfluorinated rubber)

FFKM has the best characteristics for resistance to high temperatures, with an excellent chemical inertia. This FKM-based rubber is very often used for high-temperature hydraulic and pneumatic systems, industrial valves, injection/fuel systems, motor seals and high-vacuum systems.

FKM (fluorinated rubber)

Depending on their structure and fluorine content, the chemical resistance and resistance to the cold in fluororubbers can vary. This FKM-based rubber is very often used for high-temperature hydraulics and pneumatics, for industrial valves, injection/fuel systems, motor seals and high-vacuum systems.

FVMQ (fluorosilicone rubber)

The FVMQ has mechanical and physical properties that are very similar to those of the VMQ. However, the FVMQ offers better resistance to fuels and mineral oils. However, resistance to hot air is not as good as that of the VMQ.

HNBR (Hydrogenated Nitrile Butadiene Rubber)

This HNBR-based rubber is obtained through selective hydrogenation of the NBR's butadiene groups. It is commonly used for power-assisted steering and for air conditioning.

NBR (Nitrile Butadiene Rubber)

Nitrile rubber (NBR) is the general term for acrylonitrile-butadiene copolymer. The ACN content can vary between 18% and 50%. While the acrylonitrile content is important, the resistance to oil and fuel is more so. Conversely, the elasticity and compression set are not as good. The NBR has good mechanical properties and good wear resistance. However, its resistance to atmospheric agents and the ozone is relatively low.

VMQ (silicone rubber: methyl vinyl polysiloxane)

This FVMQ-based rubber is very often used in fuel systems.

The table below gives an overview of the physical, chemical and mechanical characteristics for each of the materials.

1. Excellent properties 2. Good properties 3. Average properties 4. Poor properties

Chemical compatibility

A "Chemical compatibility guide" catalogue can be downloaded from the Documentation section. You can also use our online "Chemical compatibility" tool free of charge.

These two tools give you the option of measuring the behaviour of our materials that come into contact with the majority of existing fluids. The data displayed is the result of rigorous testing of the ambient temperature and in consultation with previous publications. Test results are not fully representative due to the specific features of your application. The tests performed actually do not consider additives and impurities that may exist under the actual conditions of use, nor the potential elevation of temperatures. Other parameters can also alter the behaviour of our materials, such as the hardness, persistence, abrasion, etc. We therefore recommend performing your own tests to verify the compatibility of our materials according to your specific application. Our technical team can provide you with any additional information.

Conditions for use

Speed

The table below indicates the relationships between the linear speed, the rotation speed and the recommended material.

The shaft seals with an additional protective lip are limited to a speed of 8 m/s.

Linear speed calculation:

s (m/s) = [Ø shaft (mm) x speed (rpm) x π] / 60,000

Loss of power

Power loss is due to a set of parameters, such as the design of the seal, choice of material, strength of the spring, speed, temperature, design of the rotating shaft, media and lubrication quality. In general, the table below provides information on power loss in Watts for a SC - SB-type shaft seal (without the anti-pollution sealing lip).

Pressure

The standard shaft seals are generally used in unpressurised environments, or for pressures between 0.02 and 0.05 MPa maximum.

Higher pressures are acceptable, following testing, for standard NBR or FKM shaft seals used on a shaft diameter less than 30 mm. Refer to the graph below:

For higher pressures, we recommend using high-pressure SCHP - TCHP shaft seals which, because of their specific design (shorter sealing lip, thicker rubber membrane, metal cage closer to the shaft), can support pressures of up to 1.0 MPa with speeds reduced to 0.3 m/s.

Temperature

The table below indicates the temperature limits, depending on the materials and fluids used.

The sealing lip of the shaft seal endures a higher temperature due to shaft rotation, and the significant pressure and friction on the mechanical parts. Good lubrication is therefore necessary to allow for a better release of heat and thus limits the temperature rise in the parts subjected to friction.

By definition, the temperature at the edge of the seal is raised when the rotation speed (and thus the linear speed) as well as the shaft diameter increases. The graph below gives an overview of the increase in temperature (in °C) at the point of contact on the sealing lip.

Fluids

Mineral oils

In general, this type of oil has few additives and is therefore perfectly suitable for all of the rubbers used for the rotary shaft seals. The following oils are suitable for rotating applications:

• motor oils
• gearbox oils
• hypoid oils
• ATF oils for automatic gearboxes
• transmission oils

synthetic oils

This type of oil is used to improve different characteristics such as the resistance to ageing, resistance to high temperatures, viscosity, etc. and has a good compatibility with the majority of rubbers used for the shaft seals. Tests may need to be performed beforehand to measure the degree of compatibility of this type of oil with the materials used. Among the synthetic oils are:

• brake fluids
• fluids for automatic gearboxes
• fluids for suspensions
• fluids for steering systems
• fluids for hydraulic transmissions

Hypoid oils

This type of oil contains special components such as EP additives. These enable lubrication and thus limit any seizing at the bearings, for example. When affected by heat, these additives have the tendency to lead to deposits on the sealing lip. That is why we recommend using shaft seals with a sealing lip comprising return pumping leads in order to limit the increase in temperature and above all, to reduce these potential carbon deposits.

Greases

Greases are generally applied to bearings etc. and require specific adaptation to provide favourable operating conditions for the shaft seal. To prevent the lip of the seal from sustaining more significant pressures than planned, we recommend positioning the lip seal on one side of the bearing in such a way so that the lip is not prematurely destroyed. We also recommend reducing the rotation speed by 50% when lubricated, to ensure that less heat escapes during friction.

Aggressive fluids

It is critical to choose the correct material to better resist different aggressive fluids (acids, solvents, chemical products, etc.). For applications in a rotating environment, we recommend using materials such as FKM rather than NBR. For operations that are dry or use very little lubrication, and where the rubbers do not resist certain aggressive fluids, we advise you to use our PTFE shaft seals.

Seal design

Tolerance for the outside diameter of the seal (ØD)

The table below indicates the pre-tightening for shaft seals on the housing diameter according to standard ISO 6194-1.

Tolerance for the inside diameter of the seal (Ød)

Free and without constraint, the inside diameter of the sealing lip is always smaller than the diameter of the shaft. The pre-tightening or interference denotes the difference between these two values. Depending on the shaft diameter, the diameter of the sealing lip is generally considered to be less, between 0.8 and 3.5 mm.

Pumping leads

The sealing lip operates with low lubrication and significant heating at the point of contact with the shaft during higher stresses with elevated temperatures and speeds, and with the seal close to the bearing exercising a considerable pumping effect.

To maintain the lubrication, we recommend integrating diagonal pumping leads on the primary sealing lip, on the air side oriented in the direction of the shaft rotation, which reinforces the pumping effect of the rubber's micro-striations. Below are the types of return pumping leads that can be made:

The graph below sets out the pumping level of the rubber's micro-striations:

Shaft design

Shaft material

Suitable materials are:

• ordinary C35 and C45 steels used in mechanical construction
• 1.4300 and 1.4112 stainless steels for sealing water
• sprayed carbide coatings
• graphite
• malleable cast iron
• materials with a CVD and PVD coating

Not appropriate:

• chrome coatings solidified through non-uniform wear
• plastic materials resulting from low thermal conductivity, which can lead to a disturbance in the transport of heat, an increase in temperature in friction areas with the shaft seal, as well as a potential softening

Shaft hardness

Shaft hardness will depend on the linear speed (in m/s) and the level of pollution.

Surface roughness

The recommendations below must be considered for the quality of the shaft surface area.

Standard conditions:

• Ra = 0.2 to 0.8 µm and 0.1 for demanding applications
• Rz = 1.0 to 4.0 µm
• Rmax ≤ 6.3 µm

For pressurev > 0.1 MPa:

• Ra = 0.2 to 0.4 µm and 0.1 for demanding applications
• Rz = 1.0 to 3.0 µm
• Rmax ≤ 6.3 µm

Shaft tolerance

The shaft must have a tolerance of h11, in line with standard ISO 286-2

Chamfer and radius

You are strongly advised to install a chamfer on the shaft so as not to alter the primary sealing sealing lip of the shaft seal during assembly. Please refer to the table below.

Shaft run out

The shaft run out is a deviation between the current shaft axis and the theoretical rotation axis. It is important to reduce the shaft run out as much as possible by positioning the shaft seal as close as possible to the bearing. The table below sets out the maximum permissible values depending on the rotation speed and the sealing lip material.

Eccentricity

The shaft and housing must be assembled centred on one another in order to remove any unilateral radial load at the sealing lip of the ring.

Shaft machining

Correct shaft machining is essential to the proper operation of the sealing system.

• Plunge grinding: preferred machining method that ensures the absence of striations on the shaft (0 +/- 0.05°)
• Turning: suitable for shafts used with a unidirectional sense of rotation

Machining guidelines for surface adjustments

Housing design

Surface roughness

The recommendations below must be considered for the quality of the housing surface area.

Standard conditions for shaft seals with an apparent metal cage:

• Ra = 0.8 to 3.2 µm
• Rz = 6.3 to 16.0 µm
• Rmax ≤ 16.0 µm

Tolerance of the bore diameter of the housing

The bore diameter of the housing must have a tolerance of H8, in line with standard ISO 286-2

Groove width dimensions

The table below provides information on the width of the groove and the recommended radius.