Tubesheet with explosively-clad layer

Abstract

A tubesheet may include a base layer have a first base layer surface and a second base layer surface substantially parallel to the first base layer surface. The tubesheet may further include a first clad layer explosively welded to the first base layer surface, a second clad layer explosively welded to the second base layer surface, a third clad layer explosively welded to the first clad layer opposite the base layer, a fourth clad layer explosively welded to the second clad layer opposite the base layer.

Description

Docket No. NOB015WOTUBESHEET WITH EXPLOSIVELY-CLAD LAYER

[0001] This application claims priority to United States Provisional Patent Application No. 63 / 691,986 filed September 6, 2024, the entire contents of which are incorporated herein by reference.

[0002] Urea is a widely produced nitrogen-based fertilizer, and it is primarily synthesized through the reaction of ammonia (NH3) and carbon dioxide. Industrial production of urea may typically use two main reactions: the formation of ammonium carbamate as an intermediate, and its subsequent dehydration to form urea. These reactions are exothermic and reversible, requiring precise thermal and pressure control to maximize conversion efficiency and minimize formation of byproducts.

[0003] One important issue in industrial urea production is effective management of heat generated and consumed during the various reactions. Accordingly, heat exchangers may play a key role in urea production by facilitating the recovery and redistribution of thermal energy across various stages of the process. For example, heat exchangers may be used to preheat feedstocks, recover heat from reactor effluents, condense process vapors, and / or optimize the thermal integration of the overall system. Efficient heat exchange can improve the energy efficiency of a urea production facility and also enhance yield and stability of the process by maintaining appropriate temperature conditions.

[0004] Shell-and-tube heat exchangers may be used in urea production due to their robustness and ability to withstand the pressures and corrosive components used in urea production. However, the harsh operating environment of urea production may pose challenges in terms of equipment design, maintenance, and durability. For example, tubesheets within the heat exchangers may be exposed to temperatures, pressures, and corrosive reagents that can damage and degrade the tubesheets over time. Efforts have been made to produce tubesheets with protective layers to enhance longevity of the components. For example, US Patent. No. 9,435,589, issued on September 6, 2016 describes in part a tubesheet manufactured from a carbon steel material grade and including protective layers of an austenitic-ferritic duplex stainless steel grade.

[0005] Such protective layers may beapplied using weld overlay techniques, in which the protective layer alloy is deposited onto a face of the base layer. The protective layer is then melted and fused with the base layer, i.e., fusion welded, creating a metallurgical bond betweenDocket No. NOB015WO the protective layer and the base layer. However, weld overlay methods may result in surface imperfections, caused by the heat input created during the weld overlay process, that expose the tubesheet to corrosion.

[0006] Accordingly, it may be desirable to develop more durable, reliable, and efficient solutions for the production of a tubesheet that can be used within heat exchangers in an industrial urea production process.BRIEF SUMMARY

[0007] An exemplary embodiment of a tubesheet may include a base layer have a first base layer surface and a second base layer surface substantially parallel to the first base layer surface. The tubesheet may further include a first clad layer explosively welded to the first base layer surface, a second clad layer explosively welded to the second base layer surface, a third clad layer explosively welded to the first clad layer opposite the base layer, a fourth clad layer explosively welded to the second clad layer opposite the base layer.

[0008] An exemplary method of preparing a tubesheet for use in a heat exchanger may include preparing a base layer having a first base layer surface and a second base layer surface substantially parallel to the first base layer surface, explosively welding a first clad layer to the first base layer surface, explosively welding a second clad layer to the second base layer surface, explosively welding a third clad layer to the first clad layer opposite the base layer, and explosively welding a fourth clad layer to the second clad layer opposite the base layer.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0009] A more particular description will be rendered by reference to exemplary embodiments that are illustrated in the accompanying figures. Understanding that these drawings depict exemplary embodiments and do not limit the scope of this disclosure, the exemplary embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

[0010] FIG. 1 is a cross-section schematic of a horizontally oriented heat exchanger according to an exemplary embodiment;

[0011] FIG. 2 is a cross-section schematic of a vertically oriented heat exchanger according to an exemplary embodiment;

[0012] FIG. 3 is a plan view of a tubesheet according to an exemplary embodiment;Docket No. NOB015WO

[0013] FIG. 4A illustrates formation of a tubesheet according to an exemplary embodiment;

[0014] FIG. 4B is a cross-section view of a manufacturing step of a tubesheet according to an exemplary embodiment;

[0015] FIG. 5 is a cross section view of a tubesheet according to an exemplary embodiment;

[0016] FIG. 6A is a cross section view of a manufacturing step of a tubesheet according to an exemplary embodiment;

[0017] FIG. 6B is a cross section view of a manufacturing step of a tubesheet according to an exemplary embodiment;

[0018] FIG. 6C is a cross section view of a manufacturing step of a tubesheet according to an exemplary embodiment;

[0019] FIG. 6D is a cross section view of a manufacturing step of a tubesheet according to an exemplary embodiment;

[0020] FIG. 6E is a cross section view of a manufacturing step of a tubesheet according to an exemplary embodiment;

[0021] FIG. 6F is a cross section view of a manufacturing step of a tubesheet according to an exemplary embodiment;

[0022] FIG. 6G is a cross section view of a manufacturing step of a tubesheet according to an exemplary embodiment;

[0023] FIG. 7A is a cross section view of a manufacturing step of a tubesheet according to an exemplary embodiment;

[0024] FIG. 7B is a cross section view of a manufacturing step of a tubesheet according to an exemplary embodiment; and

[0025] FIG. 8 is an explanatory schematic diagram showing steps of preparing a cladded article through explosive welding.

[0026] Various features, aspects, and advantages of the exemplary embodiments will become more apparent from the following detailed description, along with the accompanying drawings in which like numerals represent like components throughout the figures and detailed description. The various described features are not necessarily drawn to scale in the drawings but are drawn to aid in understanding the features of the exemplary embodiments.Docket No. NOB015WO

[0027] The headings used herein are for organizational purposes only and are not meant to limit the scope of the disclosure or the claims. To facilitate understanding, reference numerals have been used, where possible, to designate like elements common to the figures.DETAILED DESCRIPTION

[0028] Reference will now be made in detail to various exemplary embodiments. Each example is provided by way of explanation and is not meant as a limitation and does not constitute a definition of all possible embodiments. It is understood that reference to a particular “exemplary embodiment” of, e.g., a structure, assembly, component, configuration, method, etc. includes exemplary embodiments of, e.g., the associated features, subcomponents, method steps, etc. forming a part of the “exemplary embodiment.”

[0029] For purposes of this disclosure, the phrases “devices,” “systems,” and “methods” may be used either individually or in any combination referring without limitation to disclosed components, grouping, arrangements, steps, functions, or processes.

[0030] Shell-and-tube heat exchangers may be oriented horizontally or vertically. Additionally, shell-and-tube heat exchangers may be described in terms of tube-side flow and shell-side flow. Tube-side flow refers to fluids that flow within the tubes of the heat-exchanger and / or compartments in fluid communication with the tubes. Shell-side flow refers to fluids that flow within the shell in a space surrounding the tubes. These concepts will be explained in detail below with reference to FIG. 1 and FIG. 2. A shell-and-tube heat exchanger may be configured for use in at least one step in a urea production process as described below.

[0031] FIG. 1 shows an exemplary embodiment of a horizontally-oriented shell-and-tube heat exchanger 102. The heat exchanger 102 may include a tube-side body 104 and a shell-side body 106, with a tubesheet 108 interposed between the tube-side body 104 and the shell-side body 106.

[0032] The tube-side body 104 and the tubesheet 108 may define a cavity that is divided into a first tube-side chamber 110 and a second tube-side chamber 112 by a divider 114 such that the first tube-side chamber 110 is sealed from direct contact with the second tube-side chamber 112 (fluid communication between the first tube-side chamber 110 and the second tube-side chamber 112 can still occur via tubes tube 118 as described in detail below). The shell-side body 106 and the tubesheet 108 may define a shell-side chamber 1 16. In an exemplary embodiment, the first tube-side chamber 110 may be considered to be a first chamber, the shell-Docket No. NOB015WO side chamber 116 may be considered to be a second chamber adjacent to the first chamber, and the second tube-side chamber 112 may be considered to be a third chamber adjacent to the first chamber and the second chamber. While FIG. 1 shows the tube-side body 104 and the shellside body 106 defining chambers of the heat exchanger, the structure is not limited to this embodiment; for example, the tube-side body 104 may be embodied as tubes or channels connected directly to the tube-sheet.

[0033] The tubesheet 108 may include a plurality of holes 302 extending through the tubesheet 108 in a thickness direction (see FIG. 3). In an exemplary embodiment, the tubesheet 108 may be corrosion resistant and able to withstand temperatures in a range of 50 to 500 degrees Celsius and pressures in a range of 50 to 500 bars. Typical applications may require a tubesheet 108 having a diameter in a range of 500 mm to 6000 mm. However, it will be understood that the disclosure is not limited to this and larger and / or smaller diameters may also be within the scope of this disclosure.

[0034] A plurality of tubes 118 may be provided within the shell-side chamber 116, and ends of the tubes may be inserted into the holes 302 of the tubesheet 108. The plurality of tubes 118 may be sealed to the tubesheet 108 such that there is no fluid communication between the shellside chamber 116 and an interior of the plurality of tubes 118. In an examplary embodiment, the plurality of tubes 118 are formed of a thermally conductive material.

[0035] The heat exchanger 102 may further include a first tube-side chamber inlet 120 connected to the first tube-side chamber 110 to supply and / or remove a fluid such as a liquid or gas to or from the first tube-side chamber 110. A second tube-side chamber inlet 122 may be connected to the second tube-side chamber 1 12 to supply and / or remove a fluid such as a liquid or gas to or from the second tube-side chamber 112. Depending on the configuration and operation of the heat exchanger 102, fluid may flow from the first tube-side chamber 110 to the second tube-side chamber 112 through the plurality of tubes 118 or from the second tube-side chamber 112 to the first tube-side chamber 110 through the plurality of tubes 118. Additional inlets may be provided at either of the first tube-side chamber 110 or the second tube-side chamber 112 to facilitate introduction of additional fluids or removal of additional fluids. The flow of fluid(s) through the first tube-side chamber 110, the plurality of tubes 118, and the second tube-side chamber 112 may be referred to as a tube-side flow.

[0036] In an exemplary embodiment, a first fluid may be introduced either of the first tubeside chamber 110 or the second tube-side chamber 112, travel through the plurality of tubesDocket No. NOB015WO118, and exit through the other of the first tube-side chamber 110 and the second tube-side chamber 112. Alternatively, a first fluid and a second fluid may be supplied to one of first tube-side chamber 1 10 or the second tube-side chamber 1 12 through the first tube-side chamber inlet 120. The first fluid and the second fluid may flow through the tubes 118 and react with each other, with one or more products flowing through the first tube-side chamber 110 and / or the second tube-side chamber 112.

[0037] The heat exchanger 102 may further include a shell-side chamber inlet 124 connected to the shell-side chamber 116 to supply a fluid such as a liquid or gas to the shell-side chamber 116. The second fluid may flow through the shell-side chamber 116 around the tubes 118. The heat exchanger 102 may further include a shell-side chamber outlet 126 connected to the shellside chamber 116 to provide a path for the second fluid to leave the shell-side chamber 116. It will be understood that the shell-side chamber inlet 124 and the shell-side chamber outlet 126 are not limited to the configuration shown in FIG. 1. For example, the shell-side chamber inlet 124 and the shell-side chamber outlet 126 may be swapped in position or provided in different positions on the shell-side body 106. Further, additional inlets and / or outlets may be connected to the shell-side chamber 116 to facilitate introduction and / or removal of additional fluids. The fluid(s) in the shell-side chamber 116 may circulate through the shell-side chamber 116 and exchange heat energy with the fluid(s) passing through the plurality of tubes 118. The circulation of the fluid through the shell-side chamber 116 may be referred to as a shell-side flow.

[0038] FIG. 2 shows an exemplary embodiment of a vertically-oriented shell-and-tube heat exchanger 202. The heat exchanger 202 may include a first tube-side body 204 defining a first tube-side chamber 206, a shell-side body 208 defining a shell-side chamber 210, and a second tube-side body 212 defining a second tube-side chamber 214. The shell-side chamber 210 may be provided between the first tube-side chamber 206 and the second tube-side chamber 214. In other words, the first tube-side chamber 206 may be considered to be a first chamber, the shellside chamber 210 may be considered to be a second chamber, and the second tube-side chamber 214 may be considered to be a third chamber, with the second chamber being provided between the first chamber and the second chamber. While FIG. 2 shows the first tube-side body 204 and the second tube-side body 210 defining chambers of the heat exchanger, the structure is not limited to this embodiment; for example, the first tube-side body 204 and the secondDocket No. NOB015WO tube-side body 210 may be embodied as channels or tubes connected directly to a first tubesheet 216 and / or the second tubesheet 218 of the heat exchanger 202.

[0039] The first tubesheet 216 may be provided between the first tube-side chamber 206 and the shell-side chamber 210, and the second tubesheet 218 may be provided between the shellside chamber 210 and the second tube-side chamber 214. The first tubesheet 216 and the second tubesheet 218 may include a plurality of holes 302 extending through each of the first tubesheet 216 and the second tubesheet 218 in a thickness direction (see FIG. 3). A plurality of tubes 118 may be provided within the shell-side chamber 210. First ends of the plurality of tubes 118 may be inserted into the holes 302 of the first tubesheet 216, and second ends of the plurality of tubes 118 may be inserted into the holes 302 of the second tubesheet 218. The plurality of tubes 118 may be sealed to the first tubesheet 216 and the second tubesheet 218 such that there is no fluid communication between the shell-side chamber 210 and the interior of the tubes 118. The plurality of tubes 118 may be formed of a thermally conductive material.

[0040] The heat exchanger 202 may further include a first tube-side chamber inlet 220 connected to the first tube-side chamber 206 to supply and / or remove a fluid such as a liquid or gas to the first tube-side chamber 206. A second tube-side chamber inlet 222 may be connected to the second tube-side chamber 214 to supply and / or remove a fluid such as a liquid or gas to the second tube-side chamber 214.

[0041] In an exemplary embodiment, a first fluid may be introduced at one of the first tubeside chamber inlet 220 and the second tube-side chamber inlet 222, travel through the plurality of tubes 118, and exit through the other of the first tube-side chamber inlet 220 and the second tube-side chamber inlet 222. Alternatively, a first fluid may be supplied to the first tube-side chamber 206 through the first tube-side chamber inlet 220, and a second fluid may be supplied to the second tube-side chamber 214 through the second tube-side chamber inlet 222. The first fluid and the second fluid may flow through the plurality of tubes 118 and react with each other, with product(s) falling back to the second tube-side chamber 214 and exiting through the second tube-side chamber inlet 222 and / or rising to the first tube-side chamber 206 and exiting through the first tube-side chamber inlet 220. It will be understood that the heat exchanger 202 is not limited to a single first tube-side chamber inlet 220 and / or a single second tube-side chamber inlet 222. Additional inlets may be provided to accommodate additional reagents and / or products being supplied to and / or removed from the heat exchanger 202.Docket No. NOB015WO

[0042] The heat exchanger 202 may further include a shell-side chamber inlet 224 connected to the shell-side chamber 210 and a shell-side chamber outlet 226 connected to the shell-side chamber 210. The shell-side chamber inlet 224 and the shell-side chamber outlet 226 may facilitate the circulation of a shell-side fluid through the shell-side chamber 210 and around the plurality of tubes 118. The shell-side fluid may may circulate through the shell-side chamber 210 and exchange heat energy with one or more tube-side fluids passing through the plurality of tubes 118. It will be understood that the heat exchanger 202 is not limited to a single shellside chamber inlet 224 and / or a single shell-side chamber outlet 226. For example additional inlets and / or outlets may be provided to allow for additional reagents to be supplied to the shell-side chamber 210 and / or additional products to be removed from the shell-side chamber 210.

[0043] FIG. 4A shows an exemplary embodiment of a step in the formation of the tubesheet 108. The tubesheet 108 may include a base layer 404 having a first base layer surface 406. In an exemplary embodiment, the base layer 404 may have a thickness of approximately 200 mm, though it will be understood that the disclosure is not limited to this thickness. For example, in an exemplary embodiment, the base layer 404 may have a thickness in a range of approximately 200 mm to approximately 1000 mm. In a further exemplary embodiment, the base layer 404 may have a thickness in a range of approximately 300 mm to approximately 900 mm. In a further exemplary embodiment, the base layer 404 may have a thickness in a range of approximately 600 mm to approximately 700 mm. Alternatively, in some applications, the base layer 404 may have a thickness in a range of approximately 400 mm to approximately 450 mm.

[0044] The base layer 404 may be formed of a steel or steel alloy. In an exemplary embodiment, the base layer 404 of the tubesheet 108 may include carbon steel. The carbon steel may have a carbon content of 0.20-0.30 % and a manganese content of 0.60-1.35 %. The carbon steel may be an alloy such as SA 266 Gr 2 or SA 266, but it will be understood that the disclosure is not limited to these alloys.

[0045] The tubesheet 108 may further include a first clad layer 408 joined to the first base layer surface 406. In an exemplary embodiment, the first clad layer 408 may be explosively welded (i.e., explosion cladded) to the first base layer surface 406. In an exemplary embodiment, the clad layer 408 consists of one and only one clad layer, i.e., a single clad layer. The first clad layer 408 may be formed of a steel or steel alloy. In an exemplary embodiment the first clad layer 408 may include a nickel-based alloy or a stainless steel. In anDocket No. NOB015WO exemplary embodiment, the first clad layer 408 may include one or more of an austenitic stainless steel, a superaustenitic stainless steel, a duplex stainless steel, or a super-duplex stainless steel. For example, the first clad layer 408 may include Safurex® super-duplex stainless steel provided by Stamicarbon, Uremium29™ super-duplex stainless steel provided by Tubacex / Casale, DMC 2907, 25Cr22Ni2Mo (alloy 25 / 22 / 2), UNS 310MoLN, SAF™ 2906 provided by Alleima, DP28W™ duplex stainless steel provided by Sumitomo Metal Industries and Toyo Engineering Corporation, DMV2907, or Saturn31™ super-duplex stainless steel provided by Tubacex, but it will be understood that the disclosure is not limited to these examples. Alternatively, in an exemplary embodiment, the first clad layer 408 may be formed of a nickel-based alloy, for example alloy 600 (i.e., INCONEL® 600). In an exemplary embodiment, the first clad layer 408 may include an austenitic-ferritic stainless steel comprising approximately 30-70% ferrite by microstructure phase volume, and weight composition of approximately 28-35% chromium, approximately 3-10% nickel, approximately 1-4% molybdenum, approximately 0-0.05% carbon, and approximately 0.2-0.6% nitrogen. In an exemplary embodiment, the first clad layer 408 may include a fully austenitic stainless steel having a weight composition of approximately 45-55% iron, approximately 24-26% chromium, approximately 21-23% nickel, approximately 2-3% molybdenum, approximately 0-0.03% carbon, and approximately 0.1-0.16% nitrogen. In an exemplary embodiment, the first clad layer 408 may be formed of a nickel-based alloy have a weight composition of approximately 72-80% nickel, approximately 14-17% chromium, approximately 6-10% iron, and approximately 0-0.15% carbon. In an exemplary embodiment, the first clad layer 408 may have a thickness in a range of 6 to 25 mm, though it will be understood that the disclosure it not limited to this thickness or these specific materials.

[0046] Once the first clad layer 408 is explosively welded to the base layer 404, the holes 302 may be machined in the tubesheet 108.

[0047] FIG. 4B shows that the first clad layer 416 has been explosively welded to the base layer 410. When prepared, the first clad layer 416 may have a thickness in a range of 6 mm to 25 mm.

[0048] FIG. 5 shows a cross section of an exemplary embodiment of a tubesheet 502. The tubesheet 502 may include a base layer 504. The base layer 504 may include a first base layer surface 506 on a first side and a second base layer surface 508 on a second side. The second base layer surface 508 may be substantially parallel to the first base layer surface 506. The baseDocket No. NOB015WO layer 504 may include one or more of carbon steel, stainless steel, duplex stainless steel, or super duplex stainless steel. In an exemplary embodiment, the base layer 504 may have a thickness in a range of approximately 250 mm to approximately 600 mm. In a further exemplary embodiment, the base layer 504 may have a thickness in a range of approximately 300 mm to approximately 500 mm. In a further exemplary embodiment, the base layer 504 may have a thickness in a range of approximately 400 mm to approximately 450 mm.

[0049] The tubesheet 502 may further include a first clad layer 510 joined to the first base layer surface 506. In an exemplary embodiment, the first clad layer 510 may be explosively welded to the first base layer surface 506 of the base layer 504. The first clad layer 510 may include one or more of a nickel-based alloy, an austenitic stainless steel, a superaustenitic stainless steel, a duplex stainless steel, or a super-duplex steel stainless steel as described above.

[0050] The tubesheet 502 may further include a second clad layer 512 joined to the second base layer surface 508. In an exemplary embodiment, the second clad layer 512 may be explosively welded to the second base layer surface 508 of the base layer 504. The second clad layer 512 may include one or more of a nickel-based alloy, an austenitic stainless steel, a superaustenitic stainless steel, a duplex stainless steel, or a super-duplex steel stainless steel as described above.

[0051] The tubesheet 502 may further include a third clad layer 514 joined to the first clad layer 510 opposite the base layer 504. In an exemplary embodiment, the third clad layer 514 may be explosively welded to the first clad layer 510. The third clad layer 514 may include one or more of stainless steel, duplex stainless steel, or super duplex stainless steel. In an exemplary embodiment, the third clad layer 514 may include one or more of a nickel -based alloy, an austenitic stainless steel, a superaustenitic stainless steel, a duplex stainless steel, or a super-duplex steel stainless steel as described above.

[0052] The tubesheet 502 may further include a fourth clad layer 516 joined to the first second clad layer 512 opposite the base layer 504. In an exemplary embodiment, the fourth clad layer 516 may be explosively welded to the second clad layer 512. The fourth clad layer 516 may include one or more of a nickel-based alloy, an austenitic stainless steel, a superaustenitic stainless steel, a duplex stainless steel, or a super-duplex steel stainless steel as described above.Docket No. NOB015WO

[0053] In an exemplary embodiment, the tubesheet 502 may be corrosion resistant and able to withstand temperatures in a range of 100 to 200 degrees Celsius and pressures reaching or exceeding 16000 kPa. Typical applications may require a tubesheet 502 having a diameter in a range of 500 mm to 6000 mm. However, it will be understood that the disclosure is not limited to this and larger and / or smaller diameters may also be within the scope of this disclosure.

[0054] FIG. 6A through FIG. 6G illustrate an exemplary embodiment of a process for manufacturing a tubesheet 502. As seen in FIG. 6A, the base layer 504 may be prepared as described as above.

[0055] FIG. 6B shows that the first clad layer 510 has been explosively welded to the base layer 504. When prepared, the first clad layer 510 may have a thickness in a range of 10 mm to 25 mm.

[0056] As seen in FIG. 6C, the combined structure of the base layer 504 and the first clad layer 510 is flipped over, and the second clad layer 512 is prepared. In an exemplary embodiment, the second clad layer 512 may have a thickness in a range of 10 mm to 25 mm.

[0057] As seen in FIG. 6D, the second clad layer 512 has been explosively welded to the base layer 504, and the combined structure of the base layer 504, the first clad layer 510, and the second clad layer 512 has been flipped back over. It will be understood that the disclosure does not require the combined structure to be flipped after joining the second clad layer 512.Instead, the second clad layer 512 may remain on top, and the next layer may be joined to the second clad layer 512 instead of the first clad layer 510.

[0058] FIG. 6E shows the third clad layer 514 being prepared for joining to the first clad layer 510. In an exemplary embodiment, the third clad layer 514 may have a thickness in a range of 10 mm to 25 mm.

[0059] FIG. 6F shows that the third clad layer 514 has been explosively welded to the first clad layer 510.

[0060] In FIG. 6G, the combined structure of the base layer 504, the first clad layer 510, the second clad layer 512, and the third clad layer 514 has been flipped over. The fourth clad layer 516 has been prepared and explosively welded to the second clad layer 512. In an exemplary embodiment, the fourth clad layer 516 may have a thickness in a range of 10-25 mm.

[0061] In the embodiment described above with reference to FIG. 6A through FIG. 6G, the tubesheet 502 was formed by flipping the combined structure over between steps before joiningDocket No. NOB015WO the next layer. It will be understood that the disclosure is not limited to this order of fabrication, however, and that the layers may be joined in different orders. For example, in an alternative embodiment, the first clad layer 510 may be joined to the base layer 504, and then the third clad layer 514 may be joined to first clad layer 510. Then the combined structure may be flipped over to join the second clad layer 512 to the base layer 504, and subsequently join the fourth clad layer 516 to the base second clad layer 512.

[0062] FIG. 7A through FIG. 7B show an alternative embodiment of a tubesheet 702. FIG. 7A shows the tubesheet 702 prepared according to the process described above. It will be understood that the drawings of this disclosure are not drawn to scale, and that various dimensions may be exaggerated in order to better show certain features.

[0063] FIG. 7B shows that the tubesheet 702 has been modified through subtractive manufacturing to create a first recess 704 and a second recess 706 at opposite ends of the tubesheet 702. In an exemplary embodiment, the subtractive manufacturing may be performed by one or more of machining, turning, milling, drilling, grinding, cutting, boring, or chemical etching. The subtractive manufacturing process may leave a raised rim 708 or nose around an outer periphery at each end of the tubesheet 702. In other words, a radius of the first recess 704 and a radius of the second recess 706 may be smaller than a radius of the tubesheet 702, such that a distance from the base layer 504 to an end surface of the tubesheet 702 is smaller at a center of the tubesheet 702 than at an outer periphery of the tubesheet 702 at the raised rim 708. The raised rim 708 may help to provide structural stability in certain applications when being incorporated into a heat exchanger.

[0064] It will be understood that the first recess 704 and the second recess 706 are not limited to the specific size and / or shape shown in FIG. 7B. For example, the shape, depth and / or curvature of the first recess 704 and the second recess 706, as well as a radial width of the raised rim 708, may be varied depending on the particular application.

[0065] FIG. 8 shows an exemplary embodiment of a method 802 for explosively welding, i.e., explosion cladding, a base layer 404 with a first clad layer 408 to generate a cladded article 816 used for the preparation of the tubesheets and other products described in various embodiments above. In block 804, the base layer 404 and the first clad layer 408 are separately prepared and inspected. In an exemplary embodiment, the base layer 404 and the first clad layer 408 may be prepared as substantially flat sheets or plates. It will be noted that in explosion cladding, it may be important for the first clad layer 408 to have a substantially uniform thickness,Docket No. NOB015WO otherwise the geometry of forces applied during the explosion cladding may be sub-optimal, resulting in a low-quality weld. In block 806, mating surfaces of the base layer 404 and the first clad layer 408, i.e., a first base layer surface 406 and a first clad layer surface 818, may be ground by a grinder 820. In block 808, the first clad layer 408 may be positioned with the first clad layer surface 818 facing the first base layer surface 406 with a predetermined gap 822 provided therebetween. Explosive material 824 may be layered over the first clad layer 408. In block 810, the explosive material 824 is detonated starting at a first side and progressing to an opposite side as illustrated by arrow 826. The force of the explosion 828 propels the first clad layer 408 against the base layer 404 thereby forming a solid-state welding interface region 830 therebetween. In block 812, rollers 832 may be applied to the cladded article 816 to flatten it if necessary. In block 814, the cladded article typically undergoes quality testing. For example, an ultrasonic probe 834 may be used over an outer surface 836 of the first clad layer 408 to check for high quality bonds between the base layer 404 and the first clad layer 408.

[0066] Explosion cladding or explosion welding may provide a number of advantages over conventional fusion welding used in weld overlay techniques. For example, fusion welding may be inappropriate in circumstances where the melting temperatures of the metals being joined are too different (i.e., dissimilar metals). In this case, the heat used to melt and fuse the components may cause the formation of brittle intermetallic compounds that damage the joint. In contrast, explosion cladding does not require melting of the metals being joined, so dissimilar metals can be joined without the formation of brittle intermetallic compounds. Further, the lack of heat in explosion welding results in a substantially smaller heat-affected zone in the joint, thereby reducing residual stresses, distortion, and alteration of the metals around the joint. Explosion welding also allows for large surface areas to be quickly and uniformly joined together. In contrast, the fusion welding used in weld overlay may result in surface imperfections that increase the risk of corrosion and degradation.

[0067] This disclosure, in various embodiments, configurations and aspects, includes components, methods, processes, systems, and / or apparatuses as depicted and described herein, including various embodiments, sub-combinations, and subsets thereof. This disclosure contemplates, in various embodiments, configurations and aspects, the actual or optional use or inclusion of, e.g., components or processes as may be well-known or understood in the art and consistent with this disclosure though not depicted and / or described herein.Docket No. NOB015WO

[0068] The phrases "at least one", "one or more", and "and / or" are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions "at least one of A, B and C", "at least one of A, B, or C", "one or more of A, B, and C", "one or more of A, B, or C" and "A, B, and / or C" means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together.

[0069] Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term such as "about" or “approximately” is not to be limited to the precise value specified. Such approximating language may refer to the specific value and / or may include a range of values that may have the same impact or effect as understood by persons of ordinary skill in the art field. For example, approximating language may include a range of + / -10%, + / - 5%, or + / -3%. The term “substantially” as used herein is used in the common way understood by persons of skill in the art field with regard to patents, and may in some instances function as approximating language. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value.

[0070] In this specification and the claims that follow, reference will be made to a number of terms that have the following meanings. The terms "a" (or "an") and "the" refer to one or more of that entity, thereby including plural referents unless the context clearly dictates otherwise. As such, the terms "a" (or "an"), "one or more" and "at least one" can be used interchangeably herein. Furthermore, references to "one embodiment", "some embodiments", "an embodiment" and the like are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term such as "about" is not to be limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Terms such as "first," "second," "upper," "lower" etc. are used to identify one element from another, and unless otherwise specified are not meant to refer to a particular order or number of elements.

[0071] As used herein, the terms "may" and "may be" indicate a possibility of an occurrence within a set of circumstances; a possession of a specified property, characteristic or function;Docket No. NOB015WO and / or qualify another verb by expressing one or more of an ability, capability, or possibility associated with the qualified verb. Accordingly, usage of "may" and "may be" indicates that a modified term is apparently appropriate, capable, or suitable for an indicated capacity, function, or usage, while taking into account that in some circumstances the modified term may sometimes not be appropriate, capable, or suitable. For example, in some circumstances an event or capacity can be expected, while in other circumstances the event or capacity cannot occur - this distinction is captured by the terms "may" and "may be."

[0072] As used in the claims, the word "comprises" and its grammatical variants logically also subtend and include phrases of varying and differing extent such as for example, but not limited thereto, "consisting essentially of" and "consisting of." Where necessary, ranges have been supplied, and those ranges are inclusive of all sub-ranges therebetween. It is to be expected that the appended claims should cover variations in the ranges except where this disclosure makes clear the use of a particular range in certain embodiments.

[0073] The terms "determine", "calculate," and "compute," and variations thereof, as used herein, are used interchangeably and include any type of methodology, process, mathematical operation or technique.

[0074] This disclosure is presented for purposes of illustration and description. This disclosure is not limited to the form or forms disclosed herein. In the Detailed Description of this disclosure, for example, various features of some exemplary embodiments are grouped together to representatively describe those and other contemplated embodiments, configurations, and aspects, to the extent that including in this disclosure a description of every potential embodiment, variant, and combination of features is not feasible. Thus, the features of the disclosed embodiments, configurations, and aspects may be combined in alternate embodiments, configurations, and aspects not expressly discussed above. For example, the features recited in the following claims lie in less than all features of a single disclosed embodiment, configuration, or aspect. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of this disclosure.

[0075] Advances in science and technology may provide variations that are not necessarily express in the terminology of this disclosure although the claims would not necessarily exclude these variations.

Claims

Docket No. NOB015WOCLAIMSWhat is claimed is:

1. A tubesheet comprising: a base layer have a first base layer surface and a second base layer surface substantially parallel to the first base layer surface; a first clad layer explosively welded to the first base layer surface; a second clad layer explosively welded to the second base layer surface; a third clad layer explosively welded to the first clad layer opposite the base layer; and a fourth clad layer explosively welded to the second clad layer opposite the base layer.

2. The tubesheet of claim 1, wherein the base layer comprises a stainless steel, a carbon steel, a duplex stainless steel, or a super duplex stainless steel.

3. The tubesheet of claim 1 or 2, wherein each of the first clad layer, the second clad layer, the third clad layer, and the fourth clad layer comprises a stainless steel alloy, an austenitic stainless steel, a superaustenitic stainless steel, a duplex stainless steel, a super-duplex steel stainless steel, or a nickel-based alloy.

4. The tubesheet of any one of claims 1 to 3, wherein each of the first clad layer, the second clad layer, the third clad layer, and the fourth clad layer comprises an austenitic-ferritic stainless steel comprising approximately 30-70% ferrite by microstructure phase volume, and weight composition of approximately 28-35% chromium, approximately 3-10% nickel, approximately 1-4% molybdenum, approximately 0-0.05% carbon, and approximately 0.2-0.6% nitrogen.

5. The tubesheet of any one of claims 1 to 3, wherein each of the first clad layer, the second clad layer, the third clad layer, and the fourth clad layer comprises a fully austenitic stainless steel having a weight composition of approximately 45-55% iron, approximately 24-26% chromium, approximately 21-23% nickel, approximately 2-3% molybdenum, approximately 0- 0.03% carbon, and approximately 0.1-0.16% nitrogen.

6. The tubesheet of any one of claims 1 to 3, wherein each of the first clad layer, the second clad layer, the third clad layer, and the fourth clad layer comprises a nickel-based alloy have aDocket No. NOB015WO weight composition of approximately 72-80% nickel, approximately 14-17% chromium, approximately 6-10% iron, and approximately 0-0.15% carbon.

7. The tubesheet of any one of claims 1 to 6, further comprising: a first recess formed in a first end of the tubesheet.

8. The tubesheet of claim 7, further comprising: a second recess formed in a second end of the tubesheet opposite the first end.

9. The tubesheet of claim 7 or 8, wherein a radius of the first recess is smaller than a radius of the tubesheet.

10. The tubesheet of claim 8 or 9, wherein a radius of the second recess is smaller than a radius of the tubesheet.

11. A method of preparing a tubesheet for use in a heat exchanger, the method comprising: preparing a base layer having a first base layer surface and a second base layer surface substantially parallel to the first base layer surface; explosively welding a first clad layer to the first base layer surface; explosively welding a second clad layer to the second base layer surface; explosively welding a third clad layer to the first clad layer opposite the base layer; and explosively welding a fourth clad layer to the second clad layer opposite the base layer.

12. The method of claim 11, wherein the base layer comprises a stainless steel, a carbon steel, a duplex stainless steel, or a super duplex stainless steel.

13. The method of claim 11 or 12, wherein each of the first clad layer, the second clad layer, the third clad layer, and the fourth clad layer comprises a stainless steel alloy, an austenitic stainless steel, a superaustenitic stainless steel, a duplex stainless steel, a super-duplex steel stainless steel, or a nickel-based alloy.

14. The method of any one of claims 11 to 13, wherein each of the first clad layer, the second clad layer, the third clad layer, and the fourth clad layer comprises an austenitic-ferritic stainless steel comprising approximately 30-70% ferrite by microstructure phase volume, and weight composition of approximately 28-35% chromium, approximately 3-10% nickel,Docket No. NOB015WO approximately 1-4% molybdenum, approximately 0-0.05% carbon, and approximately 0.2-0.6% nitrogen.

15. The method of any one of claims 11 to 13, wherein each of the first clad layer, the second clad layer, the third clad layer, and the fourth clad layer comprises a fully austenitic stainless steel having a weight composition of approximately 45-55% iron, approximately 24-26% chromium, approximately 21-23% nickel, approximately 2-3% molybdenum, approximately 0- 0.03% carbon, and approximately 0.1-0.16% nitrogen.

16. The method of any one of claims 11 to 13, wherein each of the first clad layer, the second clad layer, the third clad layer, and the fourth clad layer comprises a nickel-based alloy have a weight composition of approximately 72-80% nickel, approximately 14-17% chromium, approximately 6-10% iron, and approximately 0-0.15% carbon.

17. The method of any one of claims 11 to 16, further comprising: removing a portion of the tubesheet at a first end of the tubesheet to form a first recess.

18. The method of claim 17, removing a portion of the tubesheet at a second end of the tubesheet opposite the first end to form a second recess.

19. The method of claim 17 or 18, wherein a radius of the first recess is smaller than a radius of the tubesheet.

20. The method of claim 18 or 19, wherein a radius of the second recess is smaller than a radius of the tubesheet.

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