Valve with pressure differential seating
A valve for use in oil and gas production or similar applications may include a ball disposed in a cavity of a hollow valve body and a seat comprising a curved surface with a normal component and a normal surface with a surface area larger than a projected normal surface area of the normal component of the curved surface.
1. A valve comprising:
a valve body defining a central longitudinal axis, the valve body comprising:
a first interior bore extending along the central longitudinal axis of the valve body; and
a cavity extending across the first interior bore and the central longitudinal axis;
a ball disposed within the cavity, the ball comprising:
an exterior surface; and
a second interior bore extending through the ball across a central longitudinal axis of the ball, wherein the ball is operable to rotate between an open position in which the second interior bore permits flow across the ball and through the first interior bore and a closed position in which the exterior surface of the ball prevents flow through the first interior bore; and
a seat disposed within said cavity, the seat comprising:
a curved surface to complement a portion of the exterior surface of the ball and configured to seal with the exterior surface of the ball, wherein the curved surface has an axial component parallel to the central longitudinal axis and a normal component normal to the central longitudinal axis;
a normal surface axially spaced apart from the curved surface and normal to the central longitudinal axis, wherein the normal surface comprises a surface area larger than a projected normal surface area of the normal component of the curved surface; and
a seat bushing disposed within said cavity, the seat bushing comprising:
a second normal surface normal to the central longitudinal axis; and
a third normal surface axially spaced apart from the second normal surface and normal to the central longitudinal axis, wherein the third normal surface comprises a surface area larger than the second normal surface.
2. The valve of claim 1 , wherein the seat further comprises a shoulder disposed between the curved surface and the normal surface, and wherein the third normal surface of the seat bushing and the seat define a cavity isolating the shoulder of the seat from the first interior bore and cavity of the valve body.
3. The valve of claim 1 , wherein the second normal surface of the seat bushing is isolated within the cavity.
4. The valve of claim 1 , further comprising a body bushing comprising:
a fourth normal surface normal to the central longitudinal axis; and
a fifth normal surface normal to the central longitudinal axis; wherein
the fourth normal surface is adjacent to the normal surface of the seat, and
the fifth normal surface is adjacent to the third normal surface of the seat bushing.
5. The valve of claim 1 , further comprising a body bushing comprising:
a fourth normal surface normal to the central longitudinal axis;
a fifth normal surface normal to the central longitudinal axis; and
a sixth normal surface normal to the central longitudinal axis; wherein the fourth normal surface is adjacent to the normal surface of the seat,
the fifth normal surface is adjacent to the third normal surface of the seat bushing, and
the sixth normal surface is adjacent to the valve body.
6. The valve of claim 1 , further comprising a biasing member disposed adjacent to the seat bushing and configured such that the seat bushing transmits an axial force to the seat.
7. A valve comprising:
a valve body defining a central longitudinal axis, the valve body comprising:
a first interior bore extending along the central longitudinal axis of the valve body; and
a cavity extending across the first interior bore and the central longitudinal axis;
a ball disposed within the cavity, the ball comprising:
an exterior surface; and
a second interior bore extending through the ball across a central longitudinal axis of the ball, wherein the ball is operable to rotate between an open position in which the second interior bore permits flow across the ball and through the first interior bore and a closed position in which the exterior surface of the ball prevents flow through the first interior bore; and
a seat disposed within said cavity, the seat comprising:
a curved surface to complement a portion of the exterior surface of the ball and configured to seal with the exterior surface of the ball, wherein the curved surface has an axial component parallel to the central longitudinal axis and a normal component normal to the central longitudinal axis; and
a normal surface axially spaced apart from the curved surface and normal to the central longitudinal axis, wherein the curved surface is configured to receive a normal fluid force less than a normal fluid force exerted on the normal surface for a given fluid pressure; and
a seat bushing which comprises:
a nut comprising a normal nut surface normal to the central longitudinal axis;
a bushing comprising a normal bushing surface normal to the central longitudinal axis; and
a biasing member disposed between the nut and the bushing and configured such that the seat bushing transmits an axial force to the seat.
8. A ball valve comprising:
a valve body defining an interior bore;
a ball disposed within the interior bore and configured to control flow through the interior bore;
a valve seat comprising:
a leading profile comprising a curved surface configured to engage with and seal against an exterior surface of the ball; and
a trailing profile comprising a normal surface spaced apart from the leading profile and configured to receive a net trailing fluid force; and
a seat bushing configured to isolate a portion of the leading profile from a leading fluid force, wherein the seat bushing is configured to receive an isolated portion of the leading fluid force and the leading profile is configured to receive a net portion of the leading fluid force, and the net portion of the leading fluid force is less than the net trailing fluid force.
9. The ball valve of claim 8 , wherein the seat bushing comprising a second normal surface and a third normal surface configured to define a bushing cavity with the valve seat, wherein a portion of the leading profile is isolated within the bushing cavity.
10. A method of sealing a seat against a ball valve comprising:
exerting a fluid pressure on a curved surface defined by a leading profile of the seat;
exerting the fluid pressure on a first normal surface of the seat, wherein a second axial force applied by the fluid pressure on the first normal surface is greater than a first axial force applied by the fluid pressure on the curved surface of the seat;
exerting the fluid pressure on a normal surface of a seat bushing to isolate a portion of the leading profile of the seat from a third axial force applied by the fluid pressure on the normal surface of the seat bushing;
urging the curved surface of the seat toward a ball in response to the second axial force being greater than the first axial force; and
engaging the curved surface of the seat with an exterior surface of the ball.
11. The method of claim 10 , further comprising:
transferring the third axial force applied by the fluid pressure on the normal surface of the seat bushing to a body bushing.