![]() ![]() This allows metallic components to contact during operation. Other simple non-unitized labyrinth designs, assembled with O-rings between the stator and rotor, do not provide the required axial control of the rotor as unitized designs. The unitized labyrinth design can account for radial and axial shaft movement, preventing unwanted contact between the stator and rotor. The unitized assembly, incorporating a low-friction polytetrafluoroethylene (PTFE) connection component, allows free rotor rotation even when misalignments and vibrations exist. When using a bearing isolator seal that is assembled with a unitized connection between the stator and rotor, misalignments and associated vibrations can be tolerated through designed labyrinth clearances within the seal assembly. Vibrations and misalignment can create an offset or localized pressure on the contact lip of the seal, resulting in lip abrasion, shaft surface wear and eventually lubrication loss. Most commercial lip seals can tolerate only a small amount of misalignment without affecting the contact of the seal lip and its ability to retain lubrication. If the misalignment is severe enough, this can exacerbate wear of an oil seal. Shaft misalignments (radial and axial) will typically result in a similar offset of the shaft, relative to the seal bore location. A misalignment of machine shafts between driving and driven components can result in driveline vibrations. While many variables can impact the performance and service life of a seal, equipment vibration and shaft misalignment can have a drastic impact. This can result in a maintenance-free seal assembly, reduced operating costs and cleaner operating conditions for rotating equipment. The manufacturer-recommended lubrication levels can be followed, as the bearing isolator does not require lubrication contact during operation, and the external labyrinth will prevent contamination from entering the bearing. This configuration allows the seal to operate in a dry condition, without the need for lubrication or additional maintenance schedules or the use of equipment such as automatic grease systems. These problems typically result in a user addressing the problem as mentioned above to prevent a bearing failure and avoid a shutdown.īearing isolators are a noncontact design, meaning there is no contact between a static surface of the seal assembly with the rotating shaft. Starving an oil seal of lubrication can lead to several issues, including accelerated wear of the contact lip, added friction and heat in the equipment and shaft wear. This issue can be mitigated with a bearing isolator, which provides a bidirectional sealing capability, both retaining lubrication and preventing ingress of contaminants into the system Seal lubrication requirementsĪn oil seal requires constant contact with bearing lubrication to prevent a dryrunning condition of the seal lip. In some industries, oil or grease leaking outside of a system can also result in regulatory fines from. In both scenarios, excessive lubrication can create other problems, not limited to increased costs from wasted lubrication, increased operating temperatures, and reduced efficiency due to the bearings rotating through increased volumes of grease or oil. In a grease lubricated bearing, the practice of overgreasing (grease purge) is a common method used to purge contaminants from the oil seal lip. To overcome these issues, a user may overfill the bearing unit with oil to ensure the bearing is being lubricated if a failed seal allows oil to leak. This will eventually abrade the lip, allowing lubrication to leak and shaft wear and grooving. If a seal has leaked, the presence of oil or grease on the shaft will further contribute to a buildup of contamination under the seal lip. When a lip seal is used in a dusty or dirty operating environment, residue and debris can eventually embed under the seal lip. Equipment Operating Conditions Aggressive and challenging conditions. The good news is that the MTBF of rotating equipment can be improved and unscheduled shutdowns can be minimized with the use of a bearing isolator, potentially lasting the life of the equipment. A relatively clean application that meets or exceeds recommended operating parameters for the seal will likely allow for longer service life, compared to applications with harsh environments and increased misalignments, operating temperatures and shaft speeds. The average life of a commercial oil seal can be around 1,500 hours depending on application variables. Initially, an oil seal can provide adequate sealing characteristics, but over time operating conditions, configuration and condition of the machine can contribute to wear-and eventual failure-of the seal. However, there can be limitations in performance and reliability. ![]() Contact lip oil seals are a simple solution to retain lubrication in rotating machinery. ![]()
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