Trunnion ball valve with controlled ball-seat engagement and disengagement
A trunnion ball valve provides a reliable seal when closed, while minimizing or eliminating frictional resistance during rotation of the ball. A pressurization chamber behind the upstream valve seat can be interconnected by one or more pressurization valves with either the upstream or the downstream process fluid. The interconnection can be via a single 3-way valve. When the valve is closed and the ball is fixed in orientation, the pressurization chamber is automatically connected to the upstream process fluid, thereby pressing the seat against the ball and ensuring a reliable seal. While the ball is being rotated, the pressurization chamber is automatically connected to the downstream process fluid, thereby substantially eliminating valve seat friction. Connection to the downstream process fluid can include connection to a small space in front of the upstream seat. An electronic controller can control both valve stem rotation and the pressurization valves.
1. A trunnion ball valve, comprising:
a valve housing having a top, a bottom, a valve inlet, and a valve outlet;
a valve stem extending through the top of the valve housing;
a ball within a body cavity of the valve housing that is fixed on an upper end thereof to the valve stem and is translationally fixed at a lower end thereof to the bottom of the housing via a lower trunnion, such that the ball is able to rotate with the valve stem but is otherwise fixed in location, the ball being penetrated by at least one central passage;
an upstream valve seat that is laterally displaceable within the valve housing inlet so as to be pressed against the ball or displaced away from the ball;
a pressurization chamber that abuts an upstream facing surface of the upstream valve seat;
a small space that abuts a downstream-facing surface of the upstream valve seat, the small space being in fluid communication with process fluid downstream of the valve outlet;
at least one pressurization valve, wherein the at least one pressurization valve can be transitioned between a pressurizing state and a depressurizing state, the at least one pressurization valve being configured to place the pressurization chamber in fluid communication with process fluid upstream of the valve inlet when the at least one pressurization valve is/are in the pressurizing state, and to place the pressurization chamber in fluid communication with process fluid downstream of the valve inlet, thereby substantially equalizing pressures at the upstream facing and downstream facing surfaces of the upstream valve seat, when the at least one pressurization valve is/are in the depressurizing state, the pressurization chamber being otherwise isolated from the process fluid both upstream and downstream of the trunnion ball valve.
2. The trunnion ball valve of claim 1 , wherein the at least one pressurization valve is a single valve.
3. The trunnion ball valve of claim 2 , wherein the single valve is a 3-way valve.
4. The trunnion ball valve of claim 1 , wherein when the at least one pressurization valve is/are in the depressurizing state, the pressurization chamber is in fluid communication with the small space that abuts the downstream-facing surface of the upstream valve seat.
5. The trunnion ball valve of claim 4 , wherein the upstream facing surface of the upstream valve seat is smaller in area than the downstream-facing surface of the upstream valve seat, such that when the at least one pressurization valve is/are in the depressurizing state, there is a net pressing of the upstream valve seat away from the ball.
6. The trunnion ball valve of claim 1 , wherein the at least one pressurization valve is/are configured to be automatically transitioned to the depressurized state while the ball is being rotated, and to the pressurizing state when the trunnion ball valve is closed and the ball is fixed in orientation.
7. The trunnion ball valve of claim 6 , wherein the at least one pressurization valve is/are configured to be automatically transitioned to the depressurizing state before the ball is rotated, and to the pressurizing state after the trunnion ball valve is closed and the ball is fixed in orientation.
8. The trunnion ball valve of claim 6 , further comprising an electronic valve controller that is configured to place the at least one pressurization valve in the depressurizing state when the ball and the valve stem are being rotated, and to place the at least one pressurizing valve in the pressurizing state when the trunnion ball valve is closed and the ball is fixed in orientation.
9. The trunnion ball valve of claim 8 , wherein the electronic controller is configured to control rotation of the valve stem as well as reconfiguration of the at least one pressurization valve.
10. The trunnion ball valve of claim 1 wherein the ball is fixed in lateral position at an upper end thereof to the top of the housing via an upper trunnion.