Improved safety valve for use at very high temperatures

Abstract

This invention provides a safety valve configured for use at temperatures equal to or higher than 760°C (1400℉). The safety valve includes a closure assembly capable of forming a self-tightening metal-to-metal seal. In one embodiment, the closure assembly includes a disc with arcuate fingers that surround an axis of a seat through which fluid flows. The arcuate fingers can extend inward toward the axis and downward toward the seat. This geometry allows the fingers to flex in response to pressure from fluid impacting a downstream side of the disc, such flexing causing a first sealing surface on the disc to more forcefully contact a second sealing surface on the seat.

Description

Background Technology

[0001] Flow control is used in a wide range of applications. Pressure reducing valves, or "safety" valves, are a type of flow control that prevents a rapid increase in the pressure of a flowing fluid. These devices are often necessary to avoid overpressure conditions in superheated steam flowing through hot water power plants (and similar facilities). Failure to tolerate overpressure can lead to extensive or even catastrophic damage to equipment or facility components. However, despite the need for safety valves, improvements in output efficiency designed for plants have led to operating conditions exceeding even the most robust designs, including advanced ultra-supercritical (AUSC) steam frequently exceeding 760°C (1400℉). Summary of the Invention

[0002] The subject of this disclosure relates to improvements in equipping devices with safety valves to meet these new requirements. Of particular interest is an implementation employing a unique disc / seat interface capable of maintaining a tight seal at pressures exceeding 1400℉ and up to 4200psi. This interface combines overlapping geometries on both the disc and seat, thereby maximizing contact stress at the device's set pressure. Attached Figure Description

[0003] Now, please briefly refer to the attached diagram, in which:

[0004] Figure 1 An exemplary embodiment of a closing assembly for a safety valve is shown;

[0005] Figure 2 It shows the use of Figure 1 Examples of disks and seats for closed components;

[0006] Figure 3 It shows Figure 2 Example of a disk;

[0007] Figure 4 This is shown as part of an exemplary safety valve. Figure 2 Examples of plates and bases; and

[0008] Figure 5 It shows Figure 4 An example safety valve.

[0009] Where applicable, similar reference numerals denote the same or corresponding parts and units in all the views, and these views are not drawn to scale unless otherwise stated. The embodiments disclosed herein may include elements appearing in one or more views or in a combination of views. Furthermore, the methods are merely exemplary and can be modified by, for example, reordering, adding, deleting, and / or changing the individual stages.

[0010] The accompanying drawings and any description herein are used to disclose the invention by way of example. These examples represent the best mode and also enable any person skilled in the art to practice the invention, including making and using any apparatus or system and performing any combination of methods. Elements or functions described in the singular and beginning with the words “a” or “an” should be understood to not exclude a plurality of said elements or functions unless such exclusion is expressly stated. References to “one embodiment” or “one specific embodiment” should not be construed as excluding the existence of other embodiments or specific embodiments also incorporating the said features. Detailed Implementation

[0011] The discussion now turns to describing the features of the embodiments shown in the above figures. These embodiments perform better under extreme conditions because of their unique geometry at the sealing interface. This geometry incorporates features that can flex or bend under pressure. These features form a stronger seal that maintains its integrity very close to the operation or set pressure of the safety valve. Other embodiments are within the scope of this disclosure.

[0012] Figure 1 A schematic diagram of an example of a closure assembly 100 is shown. This example is part of a safety valve 102 having a valve mechanism 104 for adjusting the closure assembly 100. The valve mechanism 104 may include a preloading unit 106 located in place to generate a load L on the closure assembly 100. The preloading unit 106 may include a biasing component 108, typically a wound compression spring 110. Also as shown, the closure assembly 100 may be located in a base 112, which may be connected to a conduit C for releasing overpressured fluid F, such as ultra-high temperature steam in a power plant.

[0013] In a broader sense, the closure assembly 100 can be configured to suit extreme operating conditions. These configurations may include components forming a metal-to-metal seal to prevent fluid F from flowing through the device during a “non-release” state. These components are arranged such that the seal is “self-tightening” to maintain tightness at the set pressure of the safety valve. This feature prevents leakage that can occur when the inlet pressure approaches the load that forms (and maintains) the seal between the components of the device. As an added benefit, the proposed design does not compromise the tightness of the seal after a load causes the valve to close abruptly (e.g., after a rapid overpressure event).

[0014] Safety valve 102 can be configured to prevent these overpressure conditions. This configuration can be used in hot water power plants that allow high-pressure steam flow. However, this disclosure does contemplate that the concepts herein can be applied to other applications, including those handling fluids with high pressure and high temperature. In one specific embodiment, valve mechanism 104 adjusts the movement of closing assembly 100 between a closed position and an open position.

[0015] The preload unit 106 can be configured to maintain a metal-to-metal seal even under high pressure upstream of the closure assembly 100. These configurations may include mechanisms for the preload biasing member 108. These mechanisms compress the compression spring 110 by an amount that generates the spring force necessary to achieve the load L, holding the safety valve 100 in its closed position and preventing fluid F from flowing through the closure assembly 100. Pressure upstream of the closure assembly 100 exceeding the load L can compress the compression spring 110, causing the safety valve 102 to move to its open position. In this open position, fluid F will flow through the closure assembly 100. In one embodiment, the closure assembly 100 will remain open until the upstream pressure drops below the load L, allowing the compression spring 110 to return to its previous deflection position (as associated with the closed position of the closure assembly 100).

[0016] Figure 2 A front view of a cross-section of an example of a closure assembly 100 is shown. This example has a contact interface 114 including a seat 116 with an aperture 118 having a central axis 120. The aperture 118 may have an inner surface 122 of radius R1. The inner surface 122 may terminate at a corner 124, preferably a rounded corner, that terminates itself at a plane or flat seating surface 126. A disc 128 is adjacent to the seat 116 and has an outer surface 130 with a plane or flat contact shoulder 132 adjacent to the rounded corner 134. An undercut 136 in the disc 128 may form an arcuate finger 138 curving inward toward the central axis 120. The arcuate finger 138 may have a radius R2 that closely matches the radius R1 of the inner surface 122. In the closed position, the outer surface 132 of the arcuate finger 138 contacts the inner surface 124 of the seat 116 to form a seal preventing fluid F from flowing through the device (unless the pressure increases to overcome a load L as discussed herein). The undercut 136 allows fluid F to impinge on the arcuate finger 138. The resulting pressure can cause the arcuate finger 138 to bend or flex outward and downward (towards the inner surface 122 of the seat 116). These "self-tightening" characteristics increase the effectiveness of the seal under extreme temperature and pressure conditions. In one embodiment, the outer surface 132 of the arcuate finger 138 may include a series of concentric recesses 140 that form a "serrated" or "recessed" portion 142 near the rounded end 144. The recessed portion 142 can help increase the contact stress at the contact interface 114, thereby further improving the seal.

[0017] Figure 3A front view of a cross-section of an example disc 128 used in the closure assembly 100 is shown. This example has a generally cylindrical shape with ends 146, 148. The outer surface 132 may have a stepped profile corresponding to a variation in the outer diameter OD of the cylinder. This stepped profile can support a percentage of elastic load to reduce pressure within the bow-shaped fingers 138. In one embodiment, the variation may include an increase in the outer diameter OD to form a pair of concentric portions 150, 152. A shoulder 154 separates the two portions 150, 152. At one end 146 of the disc 128, a recess 156 may penetrate into the material. The recess 156 may have a varying inner diameter ID. Preferably, the recess 156 may have a threaded portion P. The other end 148 may have a tapered protrusion 158 with a blunt end 160. The tapered protrusion 158 may terminate at the undercut portion 136 forming the bow-shaped fingers 138.

[0018] Figure 4 and Figure 5 It shows Figure 1 Example of safety valve 102. Figure 4 An enlarged view of the cross-section is shown. The seat 116 may form part of an inlet neck bushing 162 having a through-hole 164 extending to an orifice 118. The inlet neck bushing 162 may have a generally cylindrical bottom portion 166. The top portion 168 of the inlet neck bushing 162 may have a necking section 170 that can be inserted into the features of the base 112, shown here as one of a pair of orthogonal orifice sections 172, 174 terminating at openings 176, 178. Orifice sections 164, 174 form a flow path for fluid F to pass through the safety valve 102. The base 112 may be connected to a conduit C, for example, through a flange or welded end at openings 176, 178. In the closed position, a tapered protrusion 158 of the disc 128 may extend into the orifice 118 of the seat 116. A recess 156 on the disc 128 may receive one end of a spindle 180. The other end of the spindle 180 can be coupled to a clamping screw 182, which can be connected to the cap assembly 184. The assembly may also include a lever 186, which is rotatable (R) to move the cap assembly 184 along a vertical axis V. A compression spring 110 may be located between a pair of spring washers 188, 190. Figure 5 As best shown, the safety valve 102 may include a yoke 192 disposed on opposite sides of a compression spring 110. A support 192 is inserted into an ear 194 on a base 112 and a yoke 196 near a yoke cap assembly 184. Fasteners F may be attached to opposite ends of the support 192 to secure the assembly of the safety valve 102.

[0019] In light of the foregoing, the improvements described herein incorporate safety valves to operate under extreme conditions. These improvements employ a unique geometry to form a metal-to-metal seal, maintaining its integrity under the high pressure and temperature conditions of conditions such as ultra-high-temperature steam in power plants. This geometry may include flexible, finger-like protrusions from the disc. These protrusions tend to flex outward under downstream pressure to better engage with the seat at the metal-to-metal seal.

[0020] The examples appearing below include certain elements or clauses, one or more of which may be combined with other elements and clauses, describing embodiments contemplated within the scope and substance of this disclosure. This scope may include and contemplate other examples that would occur to a person skilled in the art. Such other examples are intended to fall within the scope of the claims if they have structural elements that are indistinguishable from the literal language of the claims, or if they include equivalent structural elements that are indistinguishable from the literal language of the claims.

Claims

1. A safety valve, comprising: Base; A seat disposed in the base has an opening having a longitudinal axis; A disc, movable relative to the base, having an end with arcuate fingers that curve inward toward the longitudinal axis and downward toward the base. The disc in the bow-shaped finger includes a plurality of recesses surrounding the longitudinal axis.

2. The safety valve of claim 1, wherein the disc has a tapered portion extending from one end and terminating near the blunt end of the seat.

3. The safety valve according to claim 1, wherein the bow-shaped fingers have an outer surface that contacts the seat in the closed position.

4. The safety valve according to claim 1, wherein the disc includes a recess at the end opposite to the conical protrusion.

5. The safety valve of claim 1, wherein the seat has an arcuate surface surrounding the longitudinal axis.

6. The safety valve according to claim 5, wherein the arcuate surface has a radius matching the radius of the arcuate fingers.

7. The safety valve according to claim 1, wherein the seat has an arcuate surface surrounding the longitudinal axis on the inner surface of the orifice.

8. The safety valve according to claim 1, further comprising: A spindle is connected to the disc at the end opposite to the bow-shaped fingers.

9. The safety valve according to claim 1, further comprising: A compression spring that is at least partially deflected to apply a load to the disk.

10. A safety valve, comprising: The base includes a perforated section that forms a flow path between a pair of openings; as well as A closure assembly disposed in the base, the closure assembly comprising a disc and a seat, the disc being arranged to form a self-tightening seal with the seat in response to fluid pressure acting on the disc. The self-tightening seal includes a surface on the disc, in which concentric recesses are provided.

11. The safety valve of claim 10, wherein the self-tightening seal comprises the flexible portion of the disc.

12. The safety valve of claim 10, wherein the self-tightening seal comprises a flexible portion of the disc that flexes outward toward the seat.

13. The safety valve of claim 10, wherein the disc and the seat form an arcuate contact surface that contacts each other to form the self-tightening seal.

14. A safety valve, comprising: The base forms a flow path for fluid to pass through between a pair of openings; A closure assembly disposed in the base and inserted between the pair of openings, the closure assembly comprising two parts, each part having an arcuate contact surface that contacts each other to form a metal-to-metal seal. One of the arcuate contact surfaces is movable relative to the other arcuate contact surface independently of the movement of the component.

15. The safety valve of claim 14, wherein one of the arcuate contact surfaces is flexible under fluid pressure.

16. The safety valve of claim 14, wherein one of the arcuate contact surfaces flexes outward and downward under fluid pressure.

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