Pressure Compensating Bellows Valve

Abstract

Bellows-sealed valves include a pressurization port that can be used to apply a compensating pressure to the "atmospheric" side of the bellows, i.e., the side of the bellows opposite the process fluid. The atmospheric side can be internal or external to the bellows. The compensating pressure can be greater than the process fluid pressure to ensure that the process fluid does not leak into the environment when a leak occurs from the pressurized fluid to the process fluid or environment. By monitoring the pressure or flow rate of the pressurized fluid, it is possible to detect leaks in the bellows and packings. Providing a pressurized fluid outlet port allows pressurized fluid to circulate through the valve, thereby mitigating the temperature of the bellows under conditions of extreme process fluid temperature.

Description

Statement of Government Interest

[0001] Portions of this invention were made with government funding under contract number DE-NA0003525 and the government may have certain rights.

[0002] This application claims the benefit of U.S. Patent Application No. 17 / 485,663, filed September 27, 2021, the disclosure of which is incorporated herein by reference in its entirety for all purposes. [Technical Field]

[0003] The present invention relates to valves, and more particularly to bellows sealed valves. [Background technology]

[0004] In critical valve applications where even the smallest amount of external valve leakage cannot be tolerated, bellows-sealed valves are typically used.

[0005] Referring to the cross-sectional view of Figure 1, the bellows-sealed valve includes an accordion-shaped bellows 100. One end 102 of the bellows 100 is welded or otherwise attached to a valve stem 104. The other end 106 of the bellows 100 is welded to a fitting 108 that may be clamped or otherwise attached to a valve bonnet 109. When the valve is operated, the valve stem 104 is moved in a linear valve stroke to control the position of a valve plug 110 relative to a valve seat 112. During the valve stroke, the bellows 100 compresses or expands with the linear movement of the sliding valve stem 104.

[0006] Bellows 100 has static seals at each end 102, 106, and because bellows 100 surrounds valve stem 104, a metal barrier is provided between the process fluid inside the valve and the outside atmosphere, eliminating leakage at valve stem 104. In the example of Figure 1, the process fluid is outside bellows 100 and the atmosphere is inside bellows 100. In other bellows valves, the process fluid is inside bellows 100 and the atmosphere is outside bellows 100.

[0007] Metal bellows 100 flexes as valve stem 104 moves, causing bellows 100 to eventually crack and fail over time. To prevent leakage due to bellows failure, a set of packings 114 is placed over bellows 100 to provide a secondary seal.

[0008] 1 leak from the outside surface of the bellows 100 through the leak path into the interior region of the bellows 100. The valve fluid is then sealed from the external environment only by the valve stem packing 114 in the valve's gland region 116. If the valve stem packing 114 leaks, the process fluid will leak to the external atmosphere. Because the valve stem packing 114 typically allows a higher level of leakage than the bellows 100, if a leak path occurs in the bellows 100, it is likely that at least some of the process fluid will leak through the bellows 100 and the valve stem packing 114 into the external environment.

[0009] Therefore, to avoid the possibility of process fluid leaking into the environment, it is important to periodically replace bellows valves, or at least replace the valve's bellows 100. However, these replacements can be inconvenient and expensive.

[0010] Therefore, there is a need for a bellows valve design that provides an extended cycle life while reducing the likelihood of process fluid being released into the environment if a leak path occurs through the bellows. Summary of the Invention

[0011] The present invention is a bellows valve design that provides an extended cycle life while reducing the likelihood of process fluid being released into the environment if a leak path occurs through the bellows.

[0012] One of the key factors affecting the cycle life of a bellows-sealed valve is the pressure difference between the outer and inner surfaces of the bellows caused by process fluid pressures higher than ambient pressure. Higher pressure differences result in higher stresses in the bellows convolutions, and these higher stresses tend to shorten the cycle life of the bellows.

[0013] In accordance with the present invention, a bellows valve includes a bellows pressurization port that can be used to pressurize the "atmosphere" side of the bellows to offset the pressure exerted by the process fluid on the "process fluid" side of the bellows, thereby reducing or eliminating the pressure differential exerted on the bellows. Much of the following description assumes that the process fluid exerts pressure on the outside of the bellows, and that the interior of the bellows is pressurized. However, those skilled in the art will readily be able to adapt the principles of the present invention to bellows valves in which the process fluid occupies the interior of the bellows and the outside of the bellows is pressurized. Therefore, all references herein to pressurizing the interior of the bellows should be understood to generally refer to pressurizing the "atmosphere" side of the bellows, which may be inside or outside the bellows.

[0014] Pressurizing the bellows with a pressurized fluid, such as nitrogen, to reduce the pressure differential offers several advantages over prior art approaches: First, the cycle life of the bellows valve is extended by reducing the stress placed on the bellows by the pressure differential.

[0015] Second, by reducing the forces experienced by the bellows, thinner bellows and / or bellows with fewer plies can be used, thereby reducing the cost of the valve.

[0016] Third, by applying pressurized fluid at a pressure slightly higher than the process fluid pressure, the present invention ensures that if a bellows leak occurs, the resulting leak will be pressurized fluid that slowly leaks into the process fluid and / or the environment, thereby substantially eliminating the possibility of process fluid leaking into the environment.

[0017] Additionally, by monitoring the pressure and / or flow rate of the pressurized fluid, leaks through the bellows and / or packing are easily detected.

[0018] In some embodiments where the process fluid may reach very high or very low temperatures, the present invention further includes a pressurized fluid outlet port, which allows pressurized fluid to circulate from the bellows pressurization port to the pressurized fluid outlet port. The pressurized fluid can then be used as a heating or cooling medium to prevent the bellows from being subjected to the extreme temperatures of the process fluid. Furthermore, if the process fluid solidifies due to extreme cold, heating and circulating the pressurized fluid can assist in freeze recovery of the valve.

[0019] One general aspect of the invention is a bellows valve system including a bellows valve including a valve seat, a valve plug configured to control flow of a process fluid through the bellows valve in response to separation between the valve plug and the valve seat, a valve stem in mechanical communication with the valve plug such that linear actuation of the valve stem controls the separation between the valve plug and the valve seat, a bellows housing surrounding a bellows portion of the valve stem, a bellows surrounding the bellows portion of the valve stem within the bellows housing, a proximal end of the bellows secured and sealed to the bellows housing and a distal end of the bellows secured and sealed to the valve stem such that the bellows is compressed and expanded upon actuation of the valve stem, the bellows configured such that process fluid contacts a first surface of the bellows but is prevented by the bellows from reaching a second surface of the bellows, and a bellows pressurization port configured to allow bellows pressurization fluid to enter the bellows valve and apply a compensation pressure to the second surface of the bellows.

[0020] In an embodiment, the first surface of the bellows is an outer surface of the bellows and the second surface of the bellows is an inner surface of the bellows.

[0021] Any of the above embodiments may further include a pressurized fluid source, a pressurized fluid pressure regulator, and a pressurized fluid line providing fluid communication between the pressurized fluid source and the bellows pressurization port of the bellows valve. Some of these embodiments may further include a pressure measurement device configured to measure the pressure of the pressurized fluid as it enters the bellows valve. Any of these embodiments may further include a flow measurement device configured to measure the flow rate of the pressurized fluid as it enters the bellows valve.

[0022] In any of the above embodiments, the bellows valve may further include a pressurized fluid outlet port configured to allow pressurized fluid to circulate from the bellows pressure port to the pressurized fluid outlet port.

[0023] Another general aspect of the invention is a method for increasing the cycle life of a bellows valve, the method including providing a bellows valve system according to the first general aspect, estimating a process pressure exerted by a process fluid on a first surface of the bellows valve, and applying pressurized fluid to a pressure port such that the pressurized fluid is applied to a second surface of the bellows, thereby reducing the differential pressure exerted on the bellows.

[0024] In an embodiment, pressurized fluid is applied to the pressure port at a pressure greater than the estimated process pressure.

[0025] Any of the above embodiments may further include monitoring at least one of the pressure of the pressurized fluid and the flow rate of the pressurized fluid.

[0026] In any of the above embodiments, if the monitored pressure or monitored flow rate changes by more than a specified amount, the method may further include determining that a leak has occurred in the bellows valve and taking steps to eliminate the leak.

[0027] In any of the above embodiments, the bellows valve can further include a pressurized fluid outlet port within the bellows valve in fluid communication with the bellows pressure port. In some of these embodiments, the method further includes circulating pressurized fluid through the bellows valve from the bellows pressure port to the pressurized fluid outlet port. And in some of these embodiments, the method further includes heating or cooling the pressurized fluid before it enters the pressurized fluid port.

[0028] And, in any of the above embodiments, the pressurized fluid may be nitrogen gas.

[0029] The features and advantages described herein are not all-inclusive, and in particular, many additional features and advantages will become apparent to those skilled in the art upon consideration of the drawings, specification, and claims. Furthermore, it should be noted that the language used herein has been chosen primarily for purposes of readability and instruction, and not to limit the scope of the inventive subject matter. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is a cross-sectional view of a prior art bellows valve.

[0031] [Figure 2] FIG. 2 is an isometric cross-sectional view of one embodiment of the present invention.

[0032] [Figure 3] 3 is an enlarged, isometric cross-sectional view of a portion of the valve of FIG. 2 showing the path of pressurized fluid as it circulates from the pressurized port to the pressurized fluid outlet port.

[0033] [Figure 4] FIG. 4 is a cross-sectional side view of the valve of FIG. 3 connected to a pressurized fluid circulation system including a pump, a flow meter, and a heater.

[0034] [Figure 5] FIG. 5 is a flow diagram illustrating an embodiment of the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] The present invention is a bellows valve design that provides an extended cycle life while reducing the likelihood of process fluid being released into the environment if a leak path occurs through the bellows.

[0036] 2, the bellows valve of the present invention includes a bellows pressurization port 200 that can be used to pressurize the "atmosphere" side of the bellows to approximate the pressure exerted on the bellows by the process fluid on the "process fluid" side of the bellows, thereby minimizing or eliminating the pressure differential exerted on the bellows 100.

[0037] 2, the process fluid applies pressure to the outside of the bellows, while the interior of the bellows is pressurized through pressurization port 200. However, one skilled in the art can readily adapt the principles of the present invention to bellows valves in which the process fluid occupies the interior of the bellows and the outside of the bellows is pressurized. Thus, it should be understood that all references herein to pressurizing the interior of the bellows generally refer to pressurizing the "atmospheric" side of the bellows, which may be internal or external.

[0038] 3, only a small gap exists between the valve stem 104, which moves up and down as the valve operates, and the surrounding bellows 100 and other structures. Nevertheless, this gap is sufficient to allow a pressurized fluid, such as nitrogen gas, to enter through the pressurization port 200 and proceed to the interior (atmospheric) side of the bellows 100, thereby minimizing the pressure difference between the inner and outer walls of the bellows 100.

[0039] Pressurizing the bellows with a pressurized fluid to reduce the pressure differential provides several advantages over prior art approaches: First, the cycle life of the bellows valve is extended by reducing the stresses placed on the bellows 100 by the pressure differential.

[0040] Second, reducing the forces experienced by the bellows 100 allows for the use of thinner bellows 100 or bellows 100 with fewer plies, thereby reducing the cost of the valve.

[0041] Third, by applying pressurized fluid at a pressure slightly higher than the process fluid pressure, the present invention ensures that if a bellows leak occurs, the resulting leak will be pressurized fluid that slowly leaks into the process fluid or the environment, thereby substantially eliminating the possibility of process fluid leaking into the environment.

[0042] Additionally, by monitoring the pressure and / or flow rate of the pressurized fluid, leaks through the bellows and / or packing can be easily detected.

[0043] The embodiment further comprises a pressurized fluid outlet port 202. Referring to Figure 3, this allows pressurized fluid to be circulated 300 from the bellows pressurized port 200 to the pressurized fluid outlet port 202.

[0044] In the embodiment of FIG. 4 , pressurized fluid is circulated by pump 402 through pressure line 400 from bellows pressurized input port 200 to pressurized fluid outlet port 202. Flow meter 404 is used to monitor the flow rate of the pressurized fluid, and pressure meter 405 is used to monitor the pressure of the pressurized fluid entering bellows pressurized port 200. Pressurized fluid can be introduced into the system, and replenished as needed, by adding additional pressurized fluid to pressurized fluid inlet 410 and opening normally closed (NC) valve 412. Assuming pump 402 maintains the pressurized fluid at a constant pressure as it enters the valve, the flow rate should remain constant. Therefore, an increase in flow rate and / or a decrease in pressure indicates the presence of a leak path (either through bellows 100 or packing 114). Although the mechanical flow meter 404 and mechanical pressure meter 405 are shown symbolically in FIG. 4 , in other embodiments, one or both of the flow meter 404 and pressure meter 405 are electronic meters that report the measured flow rate or pressure of the bellows pressurized fluid to a controller and / or alarm system that is configured to alert support personnel if the flow rate increases above specified limits and / or if the pressure decreases below specified limits.

[0045] For example, circulating pressurized fluid through the valve may be useful when the valve is used to control a process fluid that may reach very high and / or very low temperatures. In the embodiment of FIG. 4 , for example, the pressurized fluid circulation system further includes a heater 406 that can be used to heat the pressurized fluid, thereby maintaining bellows 100 at a moderate temperature even if the process fluid drops to a very low temperature. In extreme cases, if the process fluid solidifies due to extremely low temperatures, heating and circulating pressurized fluid 300 can assist in freeze recovery of the valve. Similarly, the pressurized fluid can be used as a cooling medium to moderate the temperature of bellows 100 even if the process fluid reaches extremely high temperatures. Depending on the embodiment, the pressurized fluid can simply be circulated at ambient temperature, or a chiller can be used in place of heater 406 in FIG. 4 .

[0046] Referring to FIG. 5, one embodiment of a method of the present invention includes providing a bellows seal valve as described above and operating it to control the flow of a process fluid 500. The method further includes estimating the pressure of the process fluid applied to the process fluid side of the bellows 502 and applying pressurized fluid to the bellows pressurization port 504, preferably at a pressure slightly higher than the process fluid pressure. The method further includes monitoring 506 whether there is a leak through the bellows and / or a leak through the packing by monitoring the pressure and / or flow rate of the pressurized fluid while the bellows seal valve continues to be operated. If a leak is detected by a change in pressure or flow rate beyond a specified amount, the method further includes taking steps to eliminate the leak, such as replacing the bellows seal valve or installing a new bellows in the bellows seal valve 508.

[0047] The foregoing description of embodiments of the present invention has been presented for purposes of illustration and description. Every page of this submission, and all of its contents, however characterized, identified, or numbered, regardless of format or arrangement within the application, is deemed to be a substantial part of this application for all purposes. This specification is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of this disclosure.

[0048] Although the present application is presented in a limited number of forms, the scope of the present invention is not limited to these forms and various modifications and alterations are possible. The disclosure presented herein does not explicitly disclose all possible combinations of features that fall within the scope of the present invention. Features disclosed herein with respect to various embodiments are generally interchangeable and can be combined in any combination that is not self-contradictory without departing from the scope of the present invention. In particular, limitations presented in the following dependent claims can be combined with their corresponding independent claims in any number and in any order, as long as the dependent claims are not logically incompatible with each other, without departing from the scope of the present disclosure.

Claims

1. A bellows valve system comprising a bellows valve, the bellows valve comprising: A valve seat; a valve plug configured to control flow of process fluid through the bellows valve in response to separation between the valve plug and the valve seat; a valve stem in mechanical communication with the valve plug, the linear actuation of the valve stem configured to control the separation between the valve plug and the valve seat; a bellows housing surrounding a bellows portion of the valve stem; a bellows surrounding the bellows portion of the valve stem within the bellows housing, a proximal end of the bellows fixed and sealed to the bellows housing and a distal end of the bellows fixed and sealed to the valve stem, such that the bellows is compressed and expanded upon actuation of the valve stem, the bellows configured such that the process fluid contacts a first surface of the bellows but is prevented by the bellows from reaching a second surface of the bellows; a bellows pressure port configured to allow bellows pressurized fluid to enter the bellows valve and apply a compensating pressure to the second surface of the bellows; a source of pressurized fluid; a pressurized fluid pressure regulator; a pressurized fluid line providing fluid communication between the pressurized fluid source and the bellows pressurization port of the bellows valve; The pressurized fluid pressure regulator is configured to maintain a pressure of the pressurized fluid greater than a pressure of the process fluid.

2. 2. The bellows valve system of claim 1, The bellows valve system, wherein the first surface of the bellows is an outer surface of the bellows and the second surface of the bellows is an inner surface of the bellows.

3. 10. The bellows valve system of claim 1, further comprising: A bellows valve system comprising a pressure measuring device configured to measure the pressure of the pressurized fluid as it enters the bellows valve.

4. 10. The bellows valve system of claim 1, further comprising: A bellows valve system comprising a flow measurement device configured to measure the flow rate of the pressurized fluid as it enters the bellows valve.

5. 2. The bellows valve system of claim 1, The bellows valve system, wherein the bellows valve further comprises a pressurized fluid outlet port configured to allow the pressurized fluid to circulate from the bellows pressurization port to the pressurized fluid outlet port.

6. The bellows valve system according to claim 1 further comprises: a valve bonnet sealed to the bellows housing and surrounding the valve stem above the bellows portion of the valve stem, the bellows pressurization port configured to allow the bellows pressurized fluid to flow into the bellows portion of the bellows valve through a gap between the valve stem and the bonnet.

7. 1. A method for increasing the cycle life of a bellows valve, comprising: A bellows valve system according to claim 1 is provided, estimating a process pressure exerted by the process fluid on the first surface of the bellows valve; applying pressurized fluid to the pressure port to apply the pressurized fluid to the second surface of the bellows, thereby reducing the pressure differential applied to the bellows; Equipped with The method wherein the pressurized fluid is applied to the pressure port at a pressure greater than the estimated process pressure.

8. 8. The method of claim 7, further comprising: monitoring at least one of a pressure of the pressurized fluid and a flow rate of the pressurized fluid.

9. 9. The method of claim 8, If the monitored pressure or the monitored flow rate changes by more than a specified amount, the method further comprises determining that a leak has occurred in the bellows valve and taking steps to eliminate the leak.

10. 8. The method of claim 7, The method, wherein the bellows valve further comprises a pressurized fluid outlet port within the bellows valve in fluid communication with the bellows pressurization port.

11. 11. The method of claim 10, further comprising: circulating the pressurized fluid through the bellows valve from the bellows pressurization port to the pressurized fluid outlet port.

12. 12. The method of claim 11 further comprising: The method comprising heating or cooling the pressurized fluid before it enters the pressurized port.

13. 8. The method of claim 7, The method wherein the pressurized fluid is nitrogen gas.

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