Seal system
A sealed bearing system has a pressure-retaining seal separating two lubricating chambers, one pressure balanced to the outside and the other pressure balanced to the inside. The pressure retaining seal may be a non pumping seal. Radial bearings may be mounted near either axial side of the seal to prevent deflection. The pressure-retaining seal may include a flange and the flange may be axially compressed between a seal carrier and a portion of an outer tubular to fix the seal to the outer tubular. The seal and seal carrier may be installed using a mandrel on which they are temporarily positioned in order to insert and install them into the outer tubular.
1. A sealed bearing system rotatably connecting tubulars comprising:
an outer tubular and an inner tubular, the sealed bearing system sealing between and rotatably connecting the outer tubular and the inner tubular telescopically received in the outer tubular, the inner and outer tubulars defining an interior bore extending axially within the tubulars, a lubricant chamber between the outer tubular and the inner tubular, and an outer volume exterior to the inner and outer tubulars;
thrust bearings within the lubricant chamber for transferring axial loads between the tubulars;
a non-pumping seal arranged as a pressure retaining seal within the lubricant chamber to separate the lubricant chamber into a first pressure portion and a second pressure portion; the non-pumping seal being fixed between a seal carrier and a portion of the outer tubular;
radial bearings within the lubricant chamber for axially aligning the tubulars for coaxial relative rotation, the radial bearings including a first radial bearing connecting the seal carrier to the inner tubular, and a second radial bearing connecting the inner tubular to the outer tubular, the first radial bearing and the second radial bearing being arranged in opposite axial directions from the non-pumping seal;
a first pressure equalizing element arranged to provide pressure balancing between a pressure in the first pressure portion and a pressure in the outer volume;
a first end seal sealing between the first pressure portion and the outer volume and defining a first end of the lubricant chamber;
a second pressure equalizing element arranged to provide pressure balancing between a pressure in the second pressure portion and a pressure in the interior bore; and
a second end seal sealing between the second pressure portion and the interior bore and defining a second end of the lubricant chamber.
2. The sealed bearing system of claim 1 in which the radial bearings comprise bushings.
3. The sealed bearing system of claim 1 in which the second radial bearing is separated from the non-pumping seal by an axial distance less than an axial length of the second radial bearing.
4. The sealed bearing system of claim 1 in which the first end seal comprises a first pumping seal and the second end seal comprises a second pumping seal.
5. The sealed bearing system of claim 1 in which the first end seal comprises a first wiper seal and a first pumping seal, and the second end seal comprises a second wiper seal and a second pumping seal.
6. The sealed bearing system of claim 1 in which the first pressure equalizing element comprises a first piston separating the first pressure portion from a first chamber fluidly connected to the outer volume and the second pressure equalizing element comprises a second piston separating the second pressure portion from a second chamber fluidly connected to the interior bore.
7. The sealed bearing system of claim 6 in which the first end seal is mounted on the first piston and the second end seal is mounted on the second piston.
8. The sealed bearing system of claim 1 in which the non-pumping seal is configured to extend circumferentially around the inner tubular member and has a cross section comprising a C-shaped portion having first and second branches extending from a root portion, the first branch of the C-shaped portion having a contact surface facing an outward radial direction and adapted to stationary contact with the outer tubular member, and the second branch of the C-shaped portion including a sealing surface on a side away from the second branch, the sealing surface facing in an inward radial direction and adapted to moving contact with the inner tubular member, the seal adapted to have the root portion of the C-shaped portion facing an expected direction of relatively lower pressure in use; the seal further comprising a spring between the first and second branches biasing the first and second branches apart.
9. The sealed bearing system of claim 8 in which the non-pumping seal further comprises a flange extending radially outward from the root portion; the flange adapted to be compressed by the seal carrier against an axially facing surface of the outer tubular to fix the seal with respect to the outer tubular.