Bearing isolator seal with tapered static shutoff O-ring interface
A bearing isolator seal having a shut off O-ring is tolerant of axial rotor-stator misalignment and provides an enhanced static seal while minimizing rotational wear. A tapered section of the stator is overlapped by the shut off O-ring. When the rotor is static there is no axial misalignment, and the shut off O-ring is pressed against the tapered section, forming an enhanced seal. During rotor rotation, increased axial misalignment moves the O-ring away from the tapered section, reducing rotational wear. The stator can extend horizontally beyond the tapered section and below the O-ring, so that if the rotor moves beyond a maximum misalignment, there is a “line on line” fit between the stator and rotor. The bearing isolator seal can include labyrinth technology, and the tapered section can include a contour that allows the shutoff O-ring to drag along the surface of the tapered section with no hang-ups or binding.
1. A bearing isolator seal comprising:
a rotor surrounding and rotationally fixed to a rotatable shaft, said rotor having an inward-facing surface spaced radially outward from said rotatable shaft, a rotor gap being formed therebetween, said rotatable shaft being configured to rotate about a rotation axis;
an O-ring retention groove formed in the inward-facing surface of the rotor;
a shut off O-ring expandably located within the O-ring retention groove and configured to rotate with the rotor, the shut off O-ring forming a seal with sides of the O-ring retention groove, and having an inner diameter that extends inwardly beyond the inward facing surface of the rotor when the rotor is at rest;
a stator surrounding the rotatable shaft and configured to remain stationary when the rotor is rotating, the rotor and stator being configured to allow the rotor to shift axially relative to the stator from a neutral, axially aligned position when at rest to an axially misaligned position further removed from the stator while rotating;
a stator extension, the stator extension being an extension of the stator that extends axially into the rotor gap between the rotor inward-facing surface and the rotatable shaft and is overlapped by the shut off O-ring, so that the inner diameter of the shut off O-ring is elastically pressed against the stator extension and makes a seal with the stator extension when the rotor is at rest, but is expanded away from the stator extension by centripetal force when the rotor is rotating; and
a tapered section included in the stator extension, the tapered section being a section of the stator extension that is at least partly overlapped by the shut off O-ring when the rotor is in the neutral position, the tapered section having a surface that is tapered such that a diameter of the stator extension directly beneath the O-ring is reduced when the rotor is in the axially misaligned position, as compared to when the O-ring is in the neutral position.
2. The bearing isolator seal of claim 1 , further comprising a labyrinth passage between the rotor and the stator, the labyrinth passage being configured to expel fluid in the passage away from the shut off O-ring by centrifugal force when the rotor is rotating.
3. The bearing isolator seal of claim 1 , wherein interference between the tapered section and the shut off O-ring declines linearly as the rotor moves away from the stator, until a maximum axial displacement is reached.
4. The bearing isolator seal of claim 3 , further comprising a horizontal section of the stator that extends under the shut off O-ring beyond the tapered section, the horizontal section being configured to form a line-on-line fit with the shut off O-ring when the rotor moves beyond the maximum axial displacement.
5. The bearing isolator seal of claim 3 , wherein the maximum axial displacement is at least 0.020 inches (0.51 mm).
6. The bearing isolator seal of claim 1 , wherein the tapered section is circumferentially consistent around the rotatable shaft.
7. The bearing isolator seal of claim 1 , wherein the tapered section of the stator includes a contour that allows the shutoff O-ring to drag along a surface of the tapered section without hanging up or binding.
8. The bearing isolator seal of claim 1 , wherein the tapered section is tapered at an angle of between two degrees and thirty degrees from the rotation axis.
9. The bearing isolator seal of claim 1 , wherein edges of the O-ring retention groove are located below a horizontal centerline of the O-ring and in close clearance to the surface of the tapered section when the rotor is at rest.