Coatings for valve components to prevent erosion

Abstract

The closure member is configured for use in a valve. These configurations can have a coating or conformal layer that can cover most, if not all, of the underlying material. This layer can include pre-propagated cracks that form through thermal cycling prior to use. These pre-propagated cracks act as stress relief to accommodate thermal stresses that may arise due to different thermal expansion rates between the underlying closure member and the coating. In one implementation, the layer can include a crack profile designed to direct the formation of pre-propagated cracks and to prevent crack initiation to a certain depth in order to maintain at least some integral layer of material above the underlying plug (118). This feature can extend the useful life of the plug, especially in aggressive process fluids, such as particulate-laden fluids common in hydrocracking and refining operations.

Description

[Technical Field]

[0001] Flow control devices are found in many industrial facilities. For example, power plants and industrial processing facilities use different types of flow control devices to manage the flow of materials, typically fluids, throughout vast networks of pipes, tanks, generators, and other equipment. Control valves are useful for precisely regulating flow rates to meet process parameters. In the oil and gas industry, operators may deploy control valves to control the flow of debris-laden fluids in hydrocracking or related processes.

[0002] Fluids in these processes are known to be highly aggressive. Materials can rapidly degrade valve components directly exposed to the flow. The presence of entrained solids, such as slurry, sand, coke, coal fines, and catalysts, within the process fluid can inhibit valve throttling, reducing total flow capacity and potentially causing valve clogging. The large pressure drop across this complex fluid can cause gas release when solids, liquids, and vapors coexist simultaneously in three-phase flow. The pressure drop and resulting fluid expansion phase change can increase the velocity of solid particles within the fluid. These particles can act as high-intensity "sandblasters" that erode any surfaces within the flow path. Process parameters can increase damage from these particles, as temperatures, typically in the 400°C range, tend to make materials more aggressive as well.

[0003] Other demanding process conditions may be present as well. These conditions include vibration, mechanical cycling (continuous throttling), and valve lift positions. Thermal cycling may cause alternating expansion and contraction loads. For parts with base and cured coating materials that have different expansion rates, thermal cycling may cause the coating or "overlay" to fracture, spall, or generally separate from the base, exposing the base to highly corrosive flows. Summary of the Invention

[0004] The subject matter of this disclosure relates to improvements that can extend the service life of components exposed to highly corrosive or aggressive environments. Of particular interest are embodiments of components having a coating or "skin" that exhibits a predetermined crack profile. The skin can employ a material that is highly resistant to erosion from the sustained flow of a highly corrosive working fluid. In the case of a valve plug or "closure member," embodiments can incorporate a material layer onto the "core" component. The crack profile can direct or localize surface cracks using known methods. The component can undergo a preliminary thermal cycle to induce these directed cracks within the crack profile before shipping to a customer. This feature can act as a stress relief, for example, to avoid additional cracks resulting from thermal expansion of the core and material layers at different rates. The component may also use or incorporate an appropriate bonding material to bond a protective skin to the core component. This feature can ensure that pieces of the skin do not peel or fall off from the underlying structure, exposing it to direct contact with the working fluid. [Brief explanation of the drawings]

[0005] This specification makes reference to the following drawings: [Figure 1] 1 shows a schematic diagram of an exemplary embodiment of a closure member. [Figure 2] 2 shows a plan view of an example of a coating used on the closure element of FIG. 1; [Figure 3] 2 shows an elevational view of a cross section of an example coating used in the closure element of FIG. 1. [Figure 4] 2 shows a plan view of an example of a coating used on the closure element of FIG. 1; [Figure 5] 2 shows a plan view of an example of a coating used on the closure element of FIG. 1; [Figure 6] 1 shows an elevational view of a section of a flow control device.

[0006] These drawings and any descriptions herein represent examples that may disclose or describe the invention. These examples, including the best mode, enable one skilled in the art to practice the invention, including making and using any device or system and performing any incorporated methods. The drawings are not to scale unless otherwise noted in the discussion. Elements in the examples may appear in more than one of the figures or in combinations of the figures. The figures may use like reference numerals to indicate identical or corresponding elements. Methods are merely illustrative and may be modified, for example, by reordering, adding, removing, and / or changing individual steps or stages. Although such stages, as well as any parts, components, elements, or functions, may be identified in the singular using the word "a" or "an," this does not exclude a plural form of such designation unless the specification expressly lists or describes such exclusion. Similarly, any reference to "one embodiment" or "an implementation" does not exclude the existence of additional embodiments or implementations that also incorporate the recited features. DETAILED DESCRIPTION OF THE INVENTION

[0007] The discussion now turns to features of the examples shown in the figures above that prevent thermal stress cracking of conformal coatings covering plugs or similar closure members found on valves. Other embodiments are within the scope of this disclosure.

[0008] 1 shows an example of a closure member 100, typically found in a distribution network 102 designed to transport a material 104 throughout a network of conduits 106. The network 102 may include a flow control device 108 having a valve body 110 connected in series with the conduits 106. A valve stem 112 may couple the closure member 100 to an actuator 114. This arrangement may govern the position of the closure member 100 relative to a seat 116. In one implementation, the closure member 100 may form a plug 118 having a coating 120.

[0009] Generally, the closure member 100 may be configured to better withstand harsh working fluid or similar operating conditions. These configurations may embody components that use different materials in different (often strategic) locations, particularly those present in the working fluid flow. The components may serve to regulate flow through the valve, although the concepts herein may be applied to other functions within these types of devices.

[0010] Distribution systems 102 may be configured to deliver or move resources. These configurations may embody vast infrastructures. Materials 104 may include gases, liquids, solids, or even mixtures. Conduits 106 often include pipes or pipelines that connect to pumps, compressors, vessels, boilers, etc. Pipes may also connect to tanks or reservoirs. In many facilities, this equipment forms a complex network.

[0011] Flow control devices 108 can be configured to regulate the flow of material 104 through conduits 106 in these complex networks. These configurations can include control valves and similar devices. The valve body 110 is often made of cast or machined metal. This structure can form flanges at openings I and O. Adjacent pipes 106 can connect to these flanges. The valve stem 112 can form an elongated cylinder or rod that directs a load from an actuator 114 to the closure member 100. The load can be generated by compressed air in conjunction with a piston, spring, or flexible diaphragm. This feature helps position the closure member 100 at a desired position relative to the seat 116. This desired position, or "set point," can correspond to flow parameters for the material 104 to meet process requirements or parameters. The plug 118 can move relative to the seat 116 to meet or achieve the set point. Movement is generally along the axis of the seat 116, or "up" or "down" for valves oriented perpendicular to the process line. As noted above, the position of the plug 118 may directly correspond to the flow rate of natural gas (or other resource) flowing through (or from upstream to downstream of) the seat 116.

[0012] The coating 120 can be configured to protect the plug 118. These configurations can include layers that are unlikely to break down or erode over time during use. The layers can include structures to regulate or self-regulate crack propagation, such as stress reliefs that direct crack formation in specific areas or under specific conditions. The reliefs can respond to thermal fluctuations or thermal cycles that the part may encounter during use. Additive manufacturing techniques can deposit the layers to ensure a strong bond with the material underlying the plug 118. These techniques can also help integrate any stress reliefs or other crack profiles (or geometries) as part of the deposited layer. For example, the layer can be thinned at or along the stress reliefs. The part can be subjected to preemptive thermal cycling to allow or "force" cracks to form along these thinned sections before use in the field. This pre-cracking strategy can extend the life of the protective layer (and thus the underlying plug 118) because the crack can accommodate additional thermal expansion of the part that occurs in the field, preventing additional crack formation and eventual delamination of the protective layer.

[0013] FIG. 2 shows a plan view of an example coating 120. This example forms a thin layer 122 (or multiple "layers 122") that covers all or most of the underlying plug 118. The thin layer 122 may comprise a harder material than the plug 118. This characteristic is important for protecting the plug 118 from damage that may occur during use. Crack "lines" 124 may exist in at least a portion of the thin layer 122. The lines 124, by design, can cause the thin layer 122 to fail before other portions of the thin layer 122. For example, the lines 124 may correspond to sections or regions of the thin layer 122 that are thinner than adjacent sections. These thinner portions may succumb to thermal cycling more easily or sooner than thicker portions. Other features or anomalies may also serve to promote crack propagation; for example, the lines 124 may comprise a different material than the rest of the thin layer 122, or the lines 124 may have dimensions or cross-sections that make them prone to cracking under thermal cycling or other stresses.

[0014] FIG. 3 shows an elevational view of a cross section of the coating 120 of FIG. 2. The configuration of the line 124 can inhibit crack formation up to a maximum depth D. This configuration can stop cracks before they penetrate the thickness T of the layer 122. This feature can improve protection because it prevents cracking throughout the protective layer. The remaining thickness (TD) can maintain a conformal coating of the layer 124 over the underlying plug 118. This remaining conformal layer is less susceptible to cracking because it acts as a stress relief that can accommodate any additional thermal deviations the part will experience in the field should any existing cracks develop in the line 124 prior to use. In one implementation, the layer 122 can include a material (generally identified as L1) that helps inhibit crack initiation simply by not allowing the crack to propagate further toward the plug 118. Material L1 can eliminate the need to precisely design the line 124 to consistently achieve the appropriate depth D, thus preventing any surface of the plug 118 from being exposed to the highly aggressive working fluid.

[0015] 4 and 5 show plan views of an example coating 120. The lines 124 can form a crack profile 126 that defines a pattern 128. An example pattern can be, for example, a grid where the lines 124 intersect with each other to form a square or rectangle. The present disclosure contemplates that the design can form other shapes (e.g., triangles, diamonds, etc.), as well as combinations thereof. As best shown in FIG. 5, the grid may form a hexagon. After thermal cycling, this design can cause pre-cracks that exhibit an "alligator skin" appearance. This appearance is useful because it can alert a manufacturer or operator that the part is ready for field use.

[0016] The pattern 128 may include a collection of individual tiles 130. A space or gap 132 may separate adjacent tiles 130 from one another. In one implementation, the dimensions of the gap 132 may allow contact between the printed tiles 130, for example, during manufacturing. This arrangement, similar to the uniform conformal coating with a predetermined crack structure contemplated herein, may keep the working fluid away from the underlying plug 118 because the working fluid cannot penetrate or penetrate the “net zero” space between adjacent tiles 130. However, the separation between the tiles 130 may provide expansion relief, as adjacent tiles 130 may move relative to one another to account for thermal expansion between the components 118 and 120.

[0017] FIG. 6 shows a cross-sectional elevation view of the structure of the flow control device 108. The valve body 110 may include an upper member 134 secured to a lower member or "flange" 136. Fasteners F, such as nuts and bolts, may serve this purpose. The seat 116 may include a seat ring 138. A venturi housing 140 may reside below the seat ring 138 within the flange 136. In one implementation, the valve stem 112 may extend through a packing 142 in the member 134 to position the plug 118 adjacent to the seat ring 138. The packing 142 is useful for allowing movement of the valve stem 112 but preventing the flow control device 108 from venting fugitive emissions.

[0018] In light of the above, the improvements herein provide a new approach for constructing valve components, such as plugs or closure members, that reside in the flow of highly corrosive working fluids. This approach addresses operator concerns regarding the lifespan of certain components on process lines. These concerns prevent the use of certain materials because their inherent properties do not contribute to the working fluid. For example, hardened martensitic stainless steels lack the corrosion resistance to withstand harsh or corrosive working fluids. While standard-level austenitic stainless steels have the necessary corrosion resistance, these materials are inherently too soft for the mechanical loads encountered in flow control devices found in many process lines. On the other hand, high-performance alloys or ceramics, such as Inconel or solid tungsten carbide, appear to meet the corrosion, hardness, or strength requirements. However, many types of these materials are too brittle or, like other steels, become too brittle as their hardness increases to withstand the pressures of harsh or corrosive working fluids. This weakness can lead to failure under asymmetric mechanical loads, which can occur when particles or debris entrained in the working fluid become trapped between moving parts. Furthermore, brittle materials often fail in response to vibration. These conditions can arise in high-pressure systems from a combination of pressure drops along the system and changes in direction of high-velocity flow of the working fluid.

[0019] The following examples include specific elements or clauses to describe embodiments contemplated within the scope of this specification. These elements may be combined with other elements and clauses to similarly describe embodiments. This specification may include and contemplate other examples that occur to those skilled in the art. These other examples fall within the scope of the claims, for example, if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements that differ insignificantly from the literal language of the claims.

Claims

1. A valve, A valve comprising a movable plug having a coating disposed thereon, the coating forming adjacent tile-like shapes arranged in a predetermined pattern.

2. The valve of claim 1 , wherein a gap separates adjacent tile-like shapes.

3. 10. The valve of claim 1, wherein gaps having a depth less than a thickness of the coating separate adjacent tile-like features.

4. 10. The valve of claim 1, wherein gaps through the coating separate adjacent tile-like shapes.

5. The valve of claim 1 , wherein a gap surrounds the adjacent tile-like shapes.

6. 10. The valve of claim 1, wherein a gap having a depth less than a thickness of the coating surrounds the adjacent tile-like shapes.

7. The valve of claim 1 , wherein gaps through the coating surround the adjacent tile-like shapes.

8. 10. The valve of claim 1, wherein the coating has a thickness between adjacent tiled features, the thickness being less than a thickness at the adjacent tiled features.

9. 10. The valve of claim 1, wherein the material of the coating is different from the material of the plug.

10. The valve of claim 1 , wherein the predetermined pattern defines the adjacent tiled shapes as hexagons.

11. 1. A method comprising: A method comprising disposing a coating on a valve plug, the coating having a crack profile that responds to thermal cycling by forcing cracks to form in a predetermined pattern.

12. The method of claim 11 , further comprising thermally cycling the valve plug to initiate crack propagation.

13. The method of claim 11 , wherein the crack profile defines an area in the coating where the coating is thinner than adjacent areas.

14. The method of claim 11 , wherein the crack profile defines a line in the coating where the coating is thinner than adjacent areas.

15. The method of claim 11 , wherein the cracks have a depth that does not penetrate through the coating.

16. The method of claim 11 , wherein the cracks have a depth that penetrates the coating.

17. The method of claim 11 , wherein the coating conformally coats the valve plug.

18. The method of claim 11 , wherein the coating has a different material composition than the valve plug.

19. The method of claim 11 , wherein the predetermined pattern defines a uniform shape.

20. The method of claim 11 , wherein the predetermined pattern defines adjacent hexagons.

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