Ball joint for connecting a riser subjected to high tensile and angular loads to a pipe connector on a floating unit
A ball joint includes a suspension house comprising an inner side, a house neck and upper flange, wherein a bearing ring, having a liner fastened to its inner surface, and an upper mating surface fastened to the corresponding mating surface on the lower side of the house; a suspension ball, complementary to the inner side of the house, comprising a ball neck and lower flange, the ball having a recess on the inside of the ball, the recess comprising an inner seal ring positioned on a bias ring in the recess; the seal ring providing a seal contacting the inside of the house and a piston seal contacting the inner surface of the recess wherein the bias ring biases the seal ring parallel to the axis of the neck and away from the bias ring.
1. A ball joint for connecting a riser subjected to high tensile and angular loads to a pipe connector on a floating unit, the ball joint comprising:
a suspension house comprising a spherical inner side, a suspension house neck and an upper flange, wherein a toroidal bearing ring, having an inner surface and a bearing liner fastened to the inner surface, and an upper mating surface fastened to a corresponding mating surface on a lower side of the suspension house;
a spherical suspension ball, which is complementary to the spherical inner side of the suspension house, the spherical suspension ball comprising a suspension ball neck and a lower flange,
wherein the suspension ball comprises a recessed portion provided on an inside of a top portion of the suspension ball, the recessed portion comprising an inner tangential/cylindrical surface and a transverse circular plane surface; and a seal ring positioned on top of a bias ring in the recessed portion;
wherein the seal ring provides at least one spherical seal in sealing contact with the spherical inner side of the suspension house and at least one piston seal in sealing contact with the inner tangential/cylindrical surface of the recessed portion and wherein the bias ring provides biasing means biasing the seal ring in a direction parallel to an axis of the suspension ball neck and away from the bias ring.
2. The ball joint according to claim 1 wherein the seal ring comprises:
a circular downward and outward directed recess comprising an outward facing cylindrical vertical surface, being convexly curved with a radius R 1 , and an upper horizontal circular surface;
a spherical scraper ring mounted near a top of a spherical surface of the seal ring which is in close contact with the corresponding spherical inner side of the suspension house;
the at least one spherical seal positioned under the spherical scraper ring on the spherical surface of the seal ring;
a piston scraper ring mounted on the outwardly facing cylindrical vertical surface in close contact with the bias ring;
the at least one piston seal mounted on an outer cylindrical surface of the seal ring in sealing contact with the inner tangential/cylindrical surface of the suspension ball; and
the outer cylindrical surface of the seal ring being convexly curved in the vertical direction with a radius R 2 ;
and wherein the bias ring comprises:
a toroidal body with a rectangular cross-section comprising an inner cylindrical surface in close contact with the outwardly facing cylindrical vertical surface of the seal ring, an outer cylindrical surface with a radius slightly smaller than a radius of the inner tangential/cylindrical surface of the recessed portion, and a mating surface at a lower side of the bias ring corresponding to the transverse circular plane surface of the suspension ball; and
biasing means to bias the seal ring in a direction parallel to the axis of the suspension ball neck and away from the bias ring.
3. The ball joint according to claim 2 , wherein the biasing means are disc or blade springs.
4. The ball joint according to claim 2 , wherein the suspension ball comprises a circular negative load bearing near the top portion of the suspension ball.
5. The ball joint according to claim 2 , wherein the toroidal bearing ring is fastened to the suspension house with bolts.
6. The ball joint according to claim 2 , wherein the bias ring is fixed to or is an integral part of the suspension ball.
7. The ball joint according to claim 1 wherein the seal ring comprises:
a circular downward directed groove comprising an inner cylindrical vertical surface, being convexly curved in the vertical direction with a radius R 1 , an upper horizontal circular surface, and an outer cylindrical surface;
a spherical scraper ring mounted near a top of the spherical surface of the seal ring which is in close contact with the spherical inner side of the suspension house;
the at least one spherical seal positioned under the spherical scraper ring;
a circular scraper ring mounted on the inner surface of the seal ring in close contact with the bias ring;
the at least one piston seal mounted on an outer cylindrical surface of the seal ring in sealing contact with the inner tangential/cylindrical surface of the suspension ball; and
the outer cylindrical surface of the seal ring being convexly curved with a radius R 2 in the vertical direction;
and wherein the bias ring comprises:
a toroidal body with a rectangular cross-section comprising an inner cylindrical surface in mating contact with the outwardly facing cylindrical vertical surface of the seal ring, an outer cylindrical surface with a radius smaller than a radius of the outer cylindrical surface of the circular downward directed groove, and a mating surface at a lower side of the bias ring corresponding to the circular transverse plane surface of the suspension ball; and
biasing means to bias the seal ring in a direction parallel to the axis of the suspension ball neck and away from the bias ring.
8. The ball joint according to claim 7 wherein the biasing means are provided by a sealed chamber between the seal ring and the bias ring wherein the chamber is pressurized by a gas or liquid being supplied through a channel inside the suspension ball and the suspension ball neck.
9. The ball joint according to claim 7 , wherein the biasing means are disc or blade springs.
10. The ball joint according to claim 7 , wherein the suspension ball comprises a circular negative load bearing near the top portion of the suspension ball.
11. The ball joint according to claim 7 , wherein the toroidal bearing ring is fastened to the suspension house with bolts.
12. The ball joint according to claim 7 , wherein the bias ring is fixed to or is an integral part of the suspension ball.
13. The ball joint according to claim 1 wherein the biasing means are a plurality of helical springs evenly distributed around the seal ring and the bias ring, said plurality of helical springs being recessed in corresponding cylindrical recesses in both the seal ring and the bias ring, and wherein one or more mating protruding and recessed portions are provided on the upper horizontal circular surface of the seal ring and the top surface of the bias ring, said one or more mating protruding and recessed portions being adapted to prevent relative circular movement.
14. The ball joint according to claim 13 wherein the recesses in both the seal ring and the bias ring are coned toward their respective top surfaces.
15. The ball joint according to claim 1 , wherein the biasing means are disc or blade springs.
16. The ball joint according to claim 1 , wherein the suspension ball comprises a circular negative load bearing near the top portion of the suspension ball.
17. The ball joint according to claim 1 , wherein the toroidal bearing ring is fastened to the suspension house with bolts.
18. The ball joint according to claim 1 , wherein the bias ring is fixed to or is an integral part of the suspension ball.