CONVENIENT LUBRICATION OF ROLLERS AND TIRES RACEWAYS

Selection of the right medium to lubricate the surfaces of rolling elements is one of the significant problems encountered in the operation of objects such as rotary drums. Oil-based lubricants or sometimes even the use of water cause unfavorable phenomena in the surface layers of the rolling raceways. On the tire - visible in the photo below - the effect of the pitting phenomenonwas shown, consisting in the chipping of fragments of material subject to variable pressure in the presence of an incompressible fluid.
Microcracks present on the surface of the tire (and/or the support roller) are filled by the liquid (oil, water) and this, compressed under the influence of very high contact pressures, causes further crack propagation, ultimately resulting in extensive chipping of the material.
It is easy to imagine a wet (oily) surface in a dusty en vironment. The combination of dust and by-products of the production process with water and/or oil on the surface of the support roller raceway not only causes its unfavorable appearance, but also makes it difficult to operate and maintain a proper and stable distribu tion of forces in the drum support system.
An alternative to oil or water is graphite.
This particular form of carbon, as a substance with a lamellar, hexagonal crystal structure and anisot ropic properties, shows easy displacement of crystal layers under the influence of even a small shear stress. This property (called compressibility) is the basis for its use as a lubricant or as one of the basic components of lubricants.
The use of graphite, which is a dry lubricant, primarily increases the cleanliness of the lubricated sur faces and ensures a stable value of the friction coef ficient. The economic aspect and ecological factors are also important.
In addition to graphite, many other chemical com pounds with similar properties are known. Therefore, boron nitride, borax, mica, molybdenum diselenide, molybdenum disulfide, and tungsten disul fide are also widely used as lubricant additives. These compounds, although having similar proper ties, differ in selected parameters, the most important of which is the sliding friction coefficient.
Graphite also has many additional features that determine or exclude its use in specific conditions. Therefore, an important issue is the proper selection of its parameters.

Graphite lubrication system

SOLUTIONS TAILORED TO INDIVIDUAL NEEDS

When selecting the appropriate lubricant there should be considered:

• drum inclination angle,
• its rotational speed,
• unit pressures at the contact between the tire and the rollers,
• environmental conditions (temperature, dust, etc.),
• type of drive used.

Knowing the parameters of the object and the specific conditions of its operation, we can determine the type of lubricant - the most optimal for use. In case of graphite based solution or similar medium indication – we will also design the appropriate construction for product application.
To complement the entire implementation process, we offer the production and assembly of complete sets.

Attention:

changing / introducing a new lubricant for the race ways changes the friction coefficient between the tir es and rollers. This situation requires the calculation of new, target values of the skews of the support roll ers in order to compensate for the change in axial forces resulting from the change in the above mentioned sliding friction coefficient. In the case of objects systematically audited by us, calculations are made based on data obtained from the last inspection. In the case of objects with undefined geometry of the support system, a necessary com plement to the service is a detailed measurement of the drum in order to determine the actual skews of the support rollers and the axial distribution of forces. In both cases, we provide appropriate assistance - supervision over the implementation of the adjustments of the support rollers in order to achieve the desired final effect.

ADVANTAGES OF GRAPHITE LUBRICATION

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