Valves and valve actuation – With means to increase head and seat contact pressure – Seat pressed to valve
Reexamination Certificate
2000-12-15
2004-03-02
Mancene, Gene (Department: 3754)
Valves and valve actuation
With means to increase head and seat contact pressure
Seat pressed to valve
Reexamination Certificate
active
06698715
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to valves used in controlling the flow of fluids in a fluidic system and, more particularly, to a valve and components thereof suitable for use in high temperature, corrosive, abrasive, and other hostile environments.
BACKGROUND OF THE INVENTION
Valves are commonly employed as flow control devices in all types of fluidic systems. These valves may have many different configurations, depending on the particular application, such as a ball valve, a gate valve, a globe valve, a slide valve, a check valve and the like. Such valves typically comprise a housing having a fluid inlet and a fluid outlet, a flow-control element disposed within the housing between the inlet and the outlet, seals engaging the flow-control element to prevent the fluid from flowing between the housing and the flow-control element and/or out of the housing, and an actuating device for moving the flow-control element between an open position, where flow of the fluid between the inlet and the outlet is permitted, and a closed position in which the fluid is not able to flow between the inlet and the outlet. These components of a typical valve are generally comprised of materials appropriate for the particular application. For example, many components for a low pressure cold water valve can be comprised of a polymer material, whereas a higher pressure steam valve may be comprised predominantly of metallic components. However, common valves generally become unsuitable as the temperature and the hostility of the environment increases. For instance, where corrosive and/or abrasive-containing fluids are being handled, commonplace valves may be easily damaged unless special measures are taken in the design of the valve and/or the remainder of the fluidic system to protect the valves. Without costly measures to allow the use of commonplace valves in hostile environments, a serious safety hazard or reliability problem may be created. As a further example, high temperature fluidic processes typically require hot process fluids to be cooled before being pumped or piped to a subsequent location where the fluid may again have to be restored to the proper operating temperature for the process, thereby reducing the efficiency and raising the cost of such an operation. Thus, there exists a need for a valve capable of operating safely, reliably, and economically in high temperature or other hostile environments, such as in fluidic systems where corrosive and/or abrasive-containing fluids are present.
Still further concerns exist with common valves in emergency situations where the temperatures of the fluids to which the valves are exposed are not controllable. For example, in the event of a fire at a petrochemical refinery, excessive temperatures may cause common valves to fail, thereby allowing storage tanks to deleteriously feed the fire with catastrophic results. At excessively high temperatures, seals internal to the valve may fail, the seat and/or the flow-control element may warp, and/or any springs present within the valve may lose their spring constants and thereby allow separation of the components biased by the spring. Thus, the endeavor to develop a valve suitable for use at excessively high temperatures has led to the proposal that ceramic materials could be used for valve fabrication. See, for example, U.S. Pat. No. 4,372,531 to Rollins et al.
Ceramics are generally recognized as a class of refractory materials suitable for use in high temperature applications and in corrosive or abrasive environments. However, most ceramics are typically deficient in their ability to withstand tensile stresses without failure. Therefore, where components are fabricated from ceramic materials, these components are configured and utilized such that they are exposed mainly to compressive stresses and little or no tensile stresses. However, many components of a valve may experience significant tensile stresses due, at least in part, to shear stresses imparted by the fluid and possibly the configuration and utilization of the component. Thus, where ceramic has been utilized in the fabrication of valve components, additional measures must often be taken to assure that the valve functions as intended without the ceramic components failing. Generally, these additional measures comprise supplemental components fabricated of a material more appropriate for withstanding tensile stresses, but typically not as able to withstand excessively high temperatures as the ceramic material. For instance, a TEFLON® seal may be placed between the flow-control element and the seat. This results in a valve where the critical and/or fluid-contacting components are not entirely able to withstand excessively high temperature or other hostile environments to which the valve may be exposed. Thus, there exists a further need for a valve capable of withstanding high temperature or other hostile environments, wherein the critical and/or fluid-contacting components are fabricated of refractory materials such as a ceramic, preferably with as few seams as possible therebetween.
Thus, a continued need exists for a practical valve capable of withstanding excessively high temperatures or other hostile environments, wherein the valve is relatively simple to produce, reliable, and cost effective.
SUMMARY OF THE INVENTION
The invention comprises a flow-controlling device for controlling the flow of a fluid, a valve, capable of withstanding extreme temperatures of over 400 degrees Centigrade and also capable of withstanding abrasive and corrosive environments. All of the urging and sealing components in the valve, including the flow-control element, the seat sealingly engaging the flow-control element, and the means for urging the seat into sealing contact with the flow-control element, are prepared from highly stable refractory and/or toughened ceramic materials that are capable of withstanding abrasives, corrosives, and extreme temperatures. No resilient materials including metal, rubber and rubber-like polymers, TEFLON®, or o-rings are included in the valve. The valve components are simple in design and can be retrofitted into an existing standard valve design, including, but not limited to, poppet and ball valves. These valves can withstand process fluids at over 500 degrees Centigrade, at over 640 degrees Centigrade, and at red hot conditions of 1000 degrees Centigrade or more over extended periods of time comparable to similar designs at current practical limits of about 200 to 400 degrees Centigrade.
Certain refractory and/or toughened ceramics materials, commonly referred to as advanced ceramics, exhibit useful resistance to tensile stress when the material is heat treated in a certain manner. More particularly, a yttria-stabilized zirconia or other comparable ceramic material that is fully annealed so that porosity in the material is minimized and so that the material is substantially homogenous, is capable of substantial elongation and compression without failure. This flexible ceramic allows the fabrication of fluid-contacting, sealing, or other members from the same heat and wear-resistant materials.
The above and other needs are met by the invention which, in one embodiment, provides a flow-controlling device for controlling the flow of a fluid prepared in accordance with the invention. The device comprises a housing, a flow-control element disposed within the housing, at least one seat operably engaging the flow-control element, and a biasing device operably engaging each seat for urging the seat into sealing engagement with the flow-control element. Each of the flow-control element, the seat, and the biasing device are comprised of refractory and/or toughened materials including, for example, an advanced ceramic. More specifically, the seat, the flow-control element, the biasing device, or other components may be advantageously fabricated of a flexible ceramic material. In some embodiments, the seat and the biasing device, including a spring, are prepared as a unitary structure from a toughened ceramic, including,
Ellis David Todd
Ellis George O.
Smith, Jr. James Edwin
Alston & Bird LLP
Keasel Eric
Mancene Gene
University of Alabama
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