Valves and valve actuation – Reciprocating valve – Gate
Reexamination Certificate
2000-01-04
2001-07-17
Lee, Kevin (Department: 3753)
Valves and valve actuation
Reciprocating valve
Gate
C251S359000
Reexamination Certificate
active
06260822
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to gate valves and, more particularly, to apparatus and methods for a preferably telescoping seat assembly having an axially moveable seal element therebetween.
2. Description of the Background
Gate valves with telescoping seat assemblies have been in use for some time and have unique advantages. One advantage of this type of seat assembly in particular is the ability to provide a force on the seats that varies due to pressure differentials encountered. In this way, one is assured of a good seal with a wide range of pressure differentials. Another advantage is that friction due to movement of the gate may be kept at a minimum because the seat force applied to the gate may adjust as necessary to maintain the seal.
An exemplary type of telescoping valve seat assembly gate valve is shown in U.S. Pat. No. 4,878,651, issued Nov. 7, 1989, to F. W. Meyer, Jr., which is incorporated herein by reference, as a through conduit gate valve apparatus with a valve seat assembly that is field maintainable and which prevents the occurrence of pressure lock. Each valve seat assembly includes a retainer ring fixed in the valve body and a pressure responsive seat ring that seals with the gate member. The seat ring is responsive to fluid pressure in the valve flow passageways for maintaining and enhancing the face seal with the gate and to fluid pressure in the valve chamber for automatically venting the valve chamber to present occurrence of a pressure lock condition.
Another telescoping valve seat assembly gate valve is shown in U.S. Pat. No. 5,201,872, issued Apr. 13, 1993, to M. L. Dyer, that discloses a gate valve wherein bore pressure in the body cavity of the valve is isolated in the open and closed position. In the closed position, a double metal sealing barrier is provided across the gate. In the open position, the pressure is isolated from the stem packing and bonnet gasket by the seats on either side of the gate. Formation of hydrates in the body cavity is eliminated, and better retention of body grease is achieved during flow through the valves. Metal-to-metal seal surfaces are developed, thereby eliminating wear on the non-metal components and reducing torque requirements.
In some cases, it would be desirable to provide for another method of venting excess pressure in the bonnet. As well, it would be desirable to provide for increased or wider range of temperature operating conditions for a gate valve. In another application, it would be desirable if the downstream seat assembly provided a backup seal if the upstream seat assembly were to fail. Those skilled in the art have long sought and will appreciate the present invention which addresses these and other problems.
SUMMARY OF THE INVENTION
The present invention provides for a sealing assembly adapted for positioning between the body and the gate of a gate valve. The body defines a flow path therethrough and pockets in which the sealing assembly is positioned. The sealing assemblies on each side of the gate valve are preferably mirror images of each other so that only one is described herein and includes a substantially circular first seat element. As well, a substantially circular second seat element is provided. In one embodiment, the second seat element is telescopingly received with respect to the first seat element such that the first seat element and second seat element are each moveable in an axial direction with respect to the flow path. A sloping surface is provided for at least one of the first seat element or the second seat element. A substantially circular seal element is disposed between the first seat element and the second seat element adjacent to the sloping surface. A biasing spring is provided for biasing the circular seal toward the one axial direction with respect to the flow path for producing an initial seal between the sloping surface and the seal ring. In one embodiment, the circular seal element consists of metal and in another embodiment the circular seal element comprises metal and a coating of material that is non-permeable material substantially without memory that is, in other words, substantially inelastic. The coating is flexible or sufficiently malleable so as to form a seal with the sloping surfaces. If the seal ring consists of metal, then the seal ring is preferably of a different and preferably a softer metal than the sloping surfaces so as to be shaped somewhat for improving the seal therebetween. The seal is mounted for movement in an opposite axial direction in response to a pressure differential across the seal large enough to overcome the force of the biasing spring such that a reverse pressure differential produces flow between the sloping surface(s) and the seal element.
It is an object of the present invention to provide an improved seat assembly for a gate valve.
It is another object of the present invention to provide a seat assembly that includes a unidirectional seal element.
It is yet another object of the present invention to provide a seat assembly that operates at higher temperatures and pressures.
It is yet another object of the present invention to provide a seating assembly that will provide a backup downstream seal in case the primary upstream seal fails.
A feature of the present invention is an axially moveable sealing element that engages sloping surfaces between two seat elements.
Any listed objects, features, and advantages are not intended to limit the invention or claims in any conceivable manner but are intended merely to be informative of some of the objects, features, and advantages of the present invention. In fact, these and yet other objects, features, and advantages of the present invention will become apparent to those skilled in the art from the drawings, the descriptions given herein, and the appended claims.
REFERENCES:
patent: 4741509 (1988-05-01), Bunch
patent: 4878651 (1989-11-01), Meyer
patent: 5029812 (1991-07-01), Haynes
patent: 5201872 (1993-04-01), Dyer
patent: 5341835 (1994-08-01), Lanning, II
Lee Kevin
Nash Kenneth L.
Worldwide Oilfield Machine, Inc
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