BT/CT

Bronze or Carbon filled PTFE rod/piston bearing rings.

- Design -


This range of products is designed for use in hydraulic and pneumatic piston and gland applications to minimise the problems of metal to metal contact by inexpensive means. Produced from wear resistant filled grades of PTFE with its known properties of low friction, these products eliminate 'stiction' between moving parts, reduce 'nibbling' of the seal at high pressures due to radial movement and are easily assembled.

- Materials -


For hydraulic applications we recommend CLARON P.T.F.E. bearing tape with a Bronze filling. Style B...
For pneumatic applications we recommend CLARON P.T.F.E. bearing tape with a Carbon filling. Style CT...
Other materials are available and the table in Appendix 2 should be carefully considered.
Consult CLARON for further advice on alternative materials.

- Operating Range -


Temp. -60°C to 200°C
Velocity 15m/sec
These range parameters are maximum conditional values.
Refer to "Bearing Selection" page E0-1 and "Bearing Materials" in Seal selection Guide.

- How to Order -




- Housing -


For surface finish and recommended lead in chamfers refer the illustration below. For housing dimensions and machining tolerances refer to the table of recommended sizes and Tolerance Tables for value of tolerence symbols



- Bearing Material -




Claron P.T.F.E. Bearing Tape is specifically designed for use with P.T.F.E. Composite Seals. The nature of P.T.F.E. allows for a manufactured size giving a tighter fit than ‘harder’ materials such as Phosphor-Bronze, Meehanite or Polyester Fabric. The resulting reduction in radial clearance gives an improvement to the pressure capability of the seal but, more importantly, protects the seal from contaminant particles within the system. A combination of the design of the bearing and the characteristics of P.T.F.E. allow the particles to become embedded in the P.T.F.E. on the non-working face, thus also protecting the steel counterface from scoring. During use, bearing materials wear, causing debris and contamination of the fluid. Extensive tests have shown that particulate contamination >15µm within the fluid, increases with the use of Phosphor-Bronze or Meehanite, and tends to decrease with the use of P.T.F.E. The harder debris created by these bearings also has a greater effect upon seal performance.Particulate contamination in the fluid surrounding the seal can be over 100 times that in the main system due to the bearing preventing flushing of the seal space. Increased contamination in this area will increase the probability of a large enough particle gaining access to the seal interface, causing damage and leakage.
Claron P.T.F.E. Bearing Tape is designed to allow pressure relief to the seal by use of the expansion gap (k). This avoids the possibility of a pressure lock between the seal and the bearing, as well as eliminating the possibility of Hydrodynamic pressure build-up (shown in Figure 1) causing premature destruction of the seal. This relief also avoids the presence of excess pressure during the return stroke which can prevent the transfer of the fluid film back to the pressure side of the seal, so creating the effect of a leaking seal. Pressure relief should be incorporated within the design of continuous bearings, particularly for fast cycling applications.
The advantages of using Claron P.T.F.E. Bearing Tape are not restricted to Composite Seals but also apply to Nitrile and Polyurethane Seals.

Consideration of Radial Load
The maximum radial load applied to the bearings will determine both the width "W" of the tape and number of bearings to be used. This can be calculated based on the radial force and the maximum permissible load capacity of the material at a given temperature. In the case of either lubricated dynamic, or unlubricated static applications BRONZE filled P.T.F.E. tape should be used and the value of 'P' should be taken from graph 1 shown below. In the case of unlubricated Dynamic applications, friction has a much greater effect on the material which reduces the permissible load capacity of the material as the velocity increases. Therefore to allow for the effect of velocity, the load capacity P taken from graph 1 for CARBON filled P.T.F.E. should be reduced by multiplying it by a factor f taken from graph 2.




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