The PolyLube® Glass Tape bearing is a moderate RPM bearing designed for applications with higher surface velocities or when mixed film conditions are desired. The Glass Tape bearing is manufactured by a filament winding process that results in a continuous fiberglass filament backing composition, ensuring excellent mechanical properties (especially fatigue resistance) are attained. The filament wound fiberglass structure uses a high-strength, corrosion-resistant epoxy resin as the matrix material. The high strength backing permits the use of a thin wall bearing which can often reduce the size and weight of the finished bearing assembly. PolyLube Glass Tape bearings will support a dynamic bearing load of 7,000 PSI, while handling high radial and longitudinal stresses with a static bearing capacity of 70,000 PSI. This family of materials exhibits exceptional dimensional stability and performance predictability over wide temperature ranges (±325°F).
The PolyLube Glass Tape lined bearing is similar in backing construction when compared to its sister product, the MRP bearing; the difference in the construction of the liner material drives the variations in performance. The primary performance variation between the Glass Tape and the MRP bearings is the lower coefficient of friction for the Glass Tape bearing, allowing for higher surface velocities.
However, the Glass Tape bearing sacrifices some capabilities with a slightly lower dynamic load capacity. These differences are due to the Glass Tape bearing using a proprietary filled PTFE resin structure as opposed to the continuous PTFE filaments used in the MRP product. Two liner thicknesses are available, with the 0.015″ thick liner being standard and a 0.030″ thick liner being available for unique applications. The 0.030″ thick liner is designed for applications where boring the inner diameter might be required to achieve tighter tolerances to address sizing and minor misalignment conditions.
MECHANICAL AND PHYSICAL PROPERTIES
The PolyLube Glass Tape bearing can withstand static loads of approximately 70,000 PSI and 7,000 PSI under dynamic loading. At these loading levels, minimum distortion will occur. For dry running applications, the maximum speed is approximately 80 surface feet per minute. This bearing’s operating temperature range is ±325°F. Maximum continuous operational surface temperature for the standard formulation is 325°F, depending upon load characteristics. The bearing has been heat stabilized at these temperatures, so that little dimensional change will occur in the bearing during operation. In a free state, the coefficient of thermal expansion of the PolyLube Glass Tape bearing is approximately 4.8 x 10-6 in/in/°F, lower than steel and most metals.
The Glass Tape bearing has the lowest coefficient of friction in the PolyLube bearing line. COF is a function of pressure. Static coefficients of friction have been measured as low as 0.06. The low frictional response coupled with the higher temperature capabilities of the liner allow for the bearing to operate at higher speeds. Less heat is generated during operation and the temperature at the contact surface of the bearing can be allowed to reach higher temperatures. This combination of material properties for the PolyLube Glass Tape bearing allow continuous operation at speeds as high as 80 ft/min.
|Ultimate Compression Strength (PSI)||70,000|
|Unit Load Limit (PSI)||7,000|
|Temperature Range (°F)||± 325|
|Coefficient of Thermal Expansion (in/in/°F)||4.8 x 10-6|
|Thermal Conductivity (BTU*in(hr*ft2*°F))||1.8-2.3|
|Water Absorption (2 Hours)||0.12%|
|Water Absorption (24 Hours)||0.16%|
|Maximum Velocity (SFM)||80|
The PolyLube Glass Tape bearing should be considered when applications require higher speeds or are extremely sensitive to friction. Pneumatic cylinder gland, or guide rod, bearings are typically suited to the Glass Tape liner. The requirement for the minimum air pressure needed to begin actuation as well as the high speeds generated make the PolyLube Glass Tape the liner of choice. Other applications include sheave bearings, leveling mechanisms for aerial work platforms, and stem journal bearings for butterfly valves. Considerations for choosing the PolyLube Glass Tape liner include the presence of contamination as well as the surface finish of the pin. The soft and homogeneous nature of the Glass Tape liner results in superior frictional response as well as abrasion resistance. The trade-off is the inability to work in even moderately contaminated environments. Pin surface finish should be balanced with cycles required for the expected life of the machine. Optimal surface finish is 16 μin. The PolyLube Glass Tape bearing is capable of operating with a pin surface finish as high as 32 μin with a moderate reduction in the wear life. Pin finishes in excess of 32 μin are not recommended for use with the PolyLube Glass Tape bearing.