Force balanced rotating pressure control device
View Patent ↗Force balancing adjusts hydraulic fluid pressure in an upper piston area of a Rotating Pressure Control Device (RPCD) that has an inner housing rotatably engaged within an outer housing by an upper bearing and a lower bearing. The hydraulic fluid pressure is adjusted to balance net force in a upper piston area and a lower piston area. The fluid pressure adjustment creates a force differential that balances the total load transmitted through the upper bearing and the lower bearing and thereby extends the life of the sealing element and bearings. Additionally, a wear indicator signals the end of the useful life of the drill pipe sealing element.
1. A rotating pressure control device comprising:
an outer housing;
an inner housing with a sealing element, the inner housing adapted for rotation within the outer housing by an upper bearing and a lower bearing;
wherein a constriction of the sealing element to a drill pipe is controlled by a pressure of a hydraulic fluid;
wherein an upper piston area is created between an upper dynamic rotary seal and a middle dynamic rotary seal;
wherein a lower piston area is created between an outside surface of the drill pipe and an outside diameter of a lower dynamic sealing element;
wherein the pressure of the hydraulic fluid is adjusted to create a downward force in the upper piston area so that a total load transmitted from the inner housing through the upper bearing and the lower bearing to the outer housing is balanced; and
wherein the middle dynamic rotary seal is located between the inner housing and the outer housing and below the sealing element.
2. The rotating pressure control device of claim 1 wherein the upper dynamic rotary seal is located between the inner housing and the outer housing and above the sealing element.
3. The rotating pressure control device of claim 1 wherein a lower dynamic rotary seal is located between the inner housing and the outer housing and below the middle dynamic rotary seal.
4. The rotating pressure control device of claim 3 further comprising:
a vent port in the outer housing;
wherein the vent port is located between the middle dynamic rotary seal and the lower dynamic rotary seal; and
wherein the vent port maintains an atmospheric pressure in a vented area between the middle dynamic rotary seal and the lower dynamic rotary seal.
5. The rotating pressure control device of claim 1 wherein wellbore fluid pressurizes the lower piston to create an upward force on the inner housing.
6. A method of balancing pressure on a rotating pressure control device having an inner housing rotatably engaged with an outer housing by an upper bearing and a lower bearing, and having an upper piston area, comprising the steps of activating a sealing element to constrict a dill pipe outer diameter to form a lower piston area;
locating a middle dynamic rotary seal between the inner housing and the outer housing and below the sealing element; and
responsive to a wellbore fluid pressurizing the lower piston area, adjusting a hydraulic pressure in the upper piston area to balance a plurality of net forces on the inner housing so that a total load transmitted through the upper bearing and the lower bearing to the outer housing is balanced.
7. The method of claim 6 further comprising the step of:
using a vent port in the outer housing, located between a middle dynamic rotary seal and a lower dynamic rotary seal to maintain an atmospheric pressure between the middle dynamic rotary seal and the lower dynamic rotary seal.
8. The method of claim 6 further comprising the step of:
locating an upper dynamic rotary sad between the inner housing and the outer housing and above the sealing element.
9. The method of claim 6 further comprising the step of:
locating a lower dynamic rotary seal between the inner housing and the outer housing and below a middle dynamic rotary seal.