1. Vibration Control: Squeeze Film Damper Built In, Not Added-On
A self-generating hydrostatic pad support creates a squeeze-film damper arrangement behind each pad. This provides Pioneer’s Fluid Pivot bearing with substantially more damping than mechanically pivoted tilting pad bearings, especially at light load and high speed. A mechanical pivot introduces an undamped connection between the pad and ground which limits the effective bearing stiffness and damping. The Fluid Pivot principle introduces a well damped connection.
2. Superior Ability to Accommodate Dynamic Misalignment
The Fluid Pivot bearing with cylindrically seated pads (our Style JC) has good capability for accommodating misalignment. But our advanced Style JS Fluid Pivot bearing, with spherically-seated pads, extends this capability much further to more than 1 inch in 12 inches, an astonishing 5.0 degrees. This provides our customers unprecedented dynamic alignment, not alignment merely for the limited purpose of installation. Because either style pad is continuously floated by its hydrostatic oil film, the pads have more tolerance for operational misalignment, thermal distortion, load stresses, etc. than conventional, essentially dry, spherical bearing seats.
3. No Pivot Damage, Wear, or Fretting
In service, mechanical pivots are subject to distortion, wear, damage, and fretting. (We see them all the time–just ask our repair departments.) Whether mild or extreme, these mechanisms introduce additional, and generally unknown, clearance into the bearing. Increasing clearance can raise temperatures, de-tune stiffness, and reduce damping. Experience shows no such damage associated with the long term operation of a Fluid Pivot bearing.
4. Cooler Pad Operation: Dual-film Cooling
The individual pads operate with convected oil films on both the hydrodynamic and hydrostatic surfaces. Moreover, the through-the-pad oil port guides the oil through the center of the pad, typically near the hottest portion of the pad. These features result in more uniform oil exit temperatures and avoid the temperature extremes generated by other designs.
5. Increased Overload Capacity
Both the cylindrically-seated and the spherically-seated pads have superior overload capacity compared with mechanically pivoted configurations. Observations show that under overload, the pads can seat against the bearing shell and provide the increased load capacity of a fixed geometry bearing. When the load is reduced, the pad returns to a floating equilibrium. Equally important, bearing load capacity is not limited by contact stress considerations of a mechanical pivot.
6. Retrofit Options: Compact Design
For a given journal size and load capacity, the Fluid Pivot bearing requires a shorter length (no end seals), and an appreciably smaller shell O. D. than conventional, mechanically pivoted tilting pad journal bearings. In new machine designs, this smaller envelope may offer cost and performance benefits. Where existing journal bearings have been unsatisfactory from the standpoint of vibration, misalignment or power loss, the Fluid Pivot bearing can usually be retrofitted without altering the housing bore.