Tube-bundle for high temperatures and aggressive fluids
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-04-03
- Publication Date
- 2026-08-13
Smart Images
Figure IB2026053319_13082026_PF_FP_ABST
Abstract
Description
[0001] MNNOIOWO Giovanni Manenti
[0002] TUBE-BUNDLE FOR HIGH TEMPERATURES AND AGGRESSIVE FLUIDS DESCRIPTION
[0003] Scope
[0004] The present invention is suitable for heat exchangers, of shell-and-tube type, used for the indirect heat exchange between a tube-side fluid and a shell-side fluid, where the tube-side fluid is at high temperature and chemically aggressive and / or erosive .
[0005] In particular, this invention is suitable for quenchers installed downstream of hydrocarbon steam cracking furnaces, or for process boilers installed downstream of hydrocarbon partial oxidation reactors , operating with hot process gas on tube-side and boiling water at high pressure, as a cooling fluid, on shellside .
[0006] Technical problem to be solved
[0007] Process gases discharged from hydrocarbons steam cracking furnaces , for the production of olefins, are at 760-860 °C and are erosive due to the coke particles formed during the cracking . The cracked gases must be rapidly cooled to avoid recombination reactions, and then high-pressure boiling water ( 5-13MPa) is used as the cooling fluid .
[0008] Process gases synthesized in hydrocarbons gasification or partial oxidation reactors are at 900-1300°C and 2-8MPa, are chemically aggressive towards carbon and low-alloy steels due to the high content of H2 and CO and can be erosive due to the coke particles formed in the reactor . Synthesis gases must be abundantly cooled, so boiling water at high pressure ( 5-13 MPa) is used as the cooling fluid.
[0009] The heat exchangers for cooling the cracked gases (quenchers ) and the synthesis gases (process boilers ) with indirect heat exchange are often of shell-and-tube type, with hot gas flowing on tube-side and boiling water flowing on shell-side . The serviceMNNOIOWO Giovanni Manenti
[0010] of these heat exchangers is very demanding as the pressure parts, specifically the gas inlet tube-sheet, the first portion of the exchanging tubes and the related tube to tube-sheet welds , are subj ect to strong thermal gradients , high heat fluxes and thermomechanical stresses ; moreover, these pressure parts are subj ect to corrosive phenomena, on gas-side and on water-side, and erosive phenomena on gas-side . The quenchers are also subj ected to frequent mechanical cleaning operations or to superheated steam / air cleaning operations (decoking) on tube-side, so they are subj ect to a strong wear and tear .
[0011] To protect these heavy-duty heat exchangers from rapid wearing out or damages , robust, reliable and relatively cost-effective technological solutions must be adopted for the gas inlet tubesheet, for the first portion of heat exchanging tubes and for the related tube to tube-sheet welds . These solutions must reduce the thermo-mechanical stresses , ensure good cooling by water, and prevent corrosion and / or erosion on tube-side inlet surfaces .
[0012] Purpose of the invention
[0013] The purpose of this invention is to provide for a tube-bundle suitable for cracked gas quenchers and for syngas process boilers of shell-and-tube type .
[0014] The tube-bundle here described can mitigate and / or eliminate wear and damages to the tube-sheet, the exchanging tubes and the related tube to tube-sheet welds in correspondence with the gas inlet zone, characterized by harsh thermo-mechanical and operating conditions .
[0015] The purpose of the invention is also to provide a tube-bundle requiring a relatively cost-effective construction and a relatively practical site maintenance .
[0016] Brief description of the invention
[0017] The tube-bundle object of the present invention comprises :MNNOIOWO Giovanni Manenti
[0018] heat exchanging tubes made of carbon steel or low alloy steel, having the tube-side fluid inlet end welded to a tube-stub or ring made of material resistant to high temperatures , corrosion and erosion;
[0019] the tube-side fluid inlet tube-sheet having at least the tube-side surface of material resistant to high temperatures , corrosion and erosion;
[0020] a full-thickness, full-penetration groove weld executed, at least partially, by welding filler material resistant to high temperatures, corrosion and erosion.
[0021] The tube-stub is inserted into the tube-sheet bore and can protrude from the shell-side surface of the tube-sheet . The tubestub does not protrude from the tube-side surface of the tubesheet .
[0022] The tube-sheet is made of high-strength material for all thickness; alternatively, the tube-sheet has a tube-side surface layer of high-strength material ( such as a weld deposit or weld overlay) .
[0023] The tube-sheet is preferably thin, to increase cooling by water and to make it more flexible relative to thermo-mechanical stresses .
[0024] The welding groove between the tube-stub and the tube-sheet, or between the tube-stub, the exchanging tube and the tube-sheet, is of the "J" type and has a fairly large groove; the welding torch is placed on tube-side, in the groove and on the outside of the tube-stube . At least the last welding pass is made of high-strength filler material .
[0025] The high-strength material, mentioned in the present invention, is a metal alloy with a high nickel content .
[0026] The tube-bundle obj ect of the present invention is therefore characterized by the fact that :MNNOIOWO Giovanni Manenti
[0027] the main metallic parts relating to the tube-side fluid inlet zone and in contact with the tube-side fluid are made of high-strength material;
[0028] the weld between the tube-stub and the tube-sheet, or between the tube-stub, the exchanging tube and the tubesheet, is free of residual interstices ;
[0029] the welds between the exchanging tube and the tube-stub and between tube-stub and the tube-sheet are practical and characterized by high resistance to mechanical stress; a damaged heat exchanging tube can be replaced with a new tube by restoring the original tube to tube-sheet welds . Consequently, the tube-bundle described by the present invention is suitable for heavy-duty services characterized by high temperatures and pressures, high heat fluxes , shell-side boiler water laden of salts and impurities, and corrosive and / or erosive tube-side process gases .
[0030] State of the art
[0031] Several technological solutions for heavy-duty shell-and-tube heat exchangers , and specifically for cracked and synthesis gases, are available in the literature .
[0032] Patent doc . No . EP 1331465 describes a shell-and-tube quencher for cracked gas where the gas inlet tube-sheet has a protective layer, on the tube-side, of high-strength material and a shellside neck, machined from the tube-sheet itself, for each exchanging tube . The heat exchanging tube is butt-welded to the neck . Thus , the tube-side surface of the tube-sheet is advantageously protected, and the tube to tube-sheet weld is advantageously immersed in the water and well cooled. However, the portion of the tube-sheet related to the tube-sheet bore is partially exposed to hot gas . In addition, in case of a tube replacement, the tube to tube-sheet weld likely requires that the damaged tube is removed along with a portion of the tube-sheet; this would involve a critical site maintenance as the tube-sheetMNNOIOWO Giovanni Manenti
[0033] should be modified . Moreover, the tube to tube-sheet weld appears laborious as the welding torch, likely, must be inserted into the tube-sheet bore .
[0034] Patent doc . No . WO 2016 / 170486 describes a shell-and-tube quencher for cracked gas where the tube-sheet [ Fig . 2 ] is connected to the exchanging tube by means of a nickel alloy connecting element . The connecting element is butt-welded [ IBW] at both ends; one end is welded to the exchanging tube and the other to a neck machined from the tube-sheet on shell-side . According to this solution, the possible replacement of a damaged exchanging tube appears critical as the removal of the tube would require cutting and modifying the tube-sheet . In addition, the IBW welding appears laborious as the welding torch, likely, must be inserted into the tube-sheet bore .
[0035] Patent doc . No . WO 2022 / 049029 describes a method of replacing an exchanging tube butt-welded ( IBW welding) to a shell-side neck of the tube-sheet . The new tube, at one end, is butt-welded to a connecting element equipped with a flange that radially extends to the outside . The flange corresponds to a portion of the tubesheet and works as a weld chamfer . The resulting welding groove of the tube-sheet is of the "U" type and is quite large . This solution likely requires a significant amount of welding filler material, likely resulting in significant welding work; therefore, this solution appears adequate for the repair of a few exchanging tubes .
[0036] Patent doc . No . WO 2006 / 093907 describes a method of repairing a coil connected to a manifold and included in a heat recovery exchanger . The exchanging tube [Fig . 2D] is connected to the manifold by means of a tube-stub . The tube-stub is butt-welded at one end and fillet welded at the other end. The stub does not penetrate the manifold bore .
[0037] Patent doc . No . CN 105269122 describes a method of repair for a coiled pipe connected to a manifold by means of a tube-stub .MNNOIOWO Giovanni Manenti
[0038] The stub is butt-welded to the pipe by inserting the welding torch inside the stub . On the opposite side, the stub protrudes from the surface of the manifold.
[0039] Patent doc . No . JP S5469542 [Fig . 5 and Fig . 6] shows a "J" type welding groove between the exchanging tube and the tube-sheet, where the centring tooth at the groove bottom is not fused after welding (and therefore a gap remains between the tube and the tube-sheet ) . The same document shows [ Fig . 9] the fusion of the centring tooth by the use of a filler element and a weld executed on shell-side .
[0040] Finally, patent doc . No . US 2006 / 073086 describes a shell-and-tube chemical reactor where a corrosive fluid flows on shell-side . The tube-sheet is formed by two portions : the first portion is made of corrosion high-resistant material and is placed on the shell-side, whereas the second portion is made of corrosion low-resistance material and is placed on tube-side . The heat exchanging tubes, made of a material with high resistance to corrosion, are welded to the first portion of the tube-sheet without penetrating the tube-sheet bore .
[0041] Brief description of the figures
[0042] To support the detailed description that follows, the following figures are attached :
[0043] Fig . l, where the tube-side inlet portion of a generic heat exchanger having the tube-bundle obj ect of the present invention is schematically shown in longitudinal section; Figs . 2-5 , where tube-side inlet portions of the tube-bundle in accordance with preferential configurations of the present invention are schematically shown in longitudinal section;
[0044] Figs . 6a and 6b, where a tube-side inlet portion of the tubebundle according to a preferential configuration of the present invention is schematically shown in longitudinal section .MNNO I OWO Giovanni Manenti
[0045] Detailed description of the invention
[0046] Fig . l schematically shows , in section, the longitudinal view of the tube-side inlet portion of a heat exchanger ( HE ) equipped with a tube-bundle as per the present invention . The heat exchanger ( HE ) is of shell-and-tube type , with a substantially cylindrical geometry with a longitudinal axis ( Z ) . The exchanger ( HE ) comprises at least one tube-sheet ( 1 ) , a bundle of exchanging tubes ( 2 ) , a shell ( 3 ) enveloping the bundle , a tube-side distribution channel ( 4 ) placed at the tube-sheet ( 1 ) on the opposite side of the shell ( 3 ) , at least one tube-side inlet connection ( Tl ) placed on the channel ( 4 ) for the inlet of the tube-side fluid (G) and at least one shell-side inlet connection ( SI ) placed on the shell ( 3 ) for the inlet of the shell-side fluid ( BW) . The tube-sheet ( 1 ) is provided with bores to receive the exchanging tubes and for the passage of the tube-side fluid ( G) ; the exchanging tubes ( 2 ) are j oined to the tube-sheet ( 1 ) and are positioned parallel to each other and to the longitudinal axis ( Z ) of the exchanger ( HE ) . The heat exchanging tubes ( 2 ) and the distribution channel ( 4 ) are in fluid communication with each other; the distribution channel ( 4 ) and the exchanging tubes ( 2 ) form the tube-side (TS ) . The shell ( 3 ) , on the outside of the heat exchanging tubes ( 2 ) , forms the shell-side ( SS ) .
[0047] According to Fig . l , a tube-side fluid (G) , at high temperature and potentially corrosive and / or erosive for carbon steels and low alloy steels , enters the distribution channel ( 4 ) from the inlet tube-side connection ( Tl ) , is distributed in the exchanging tubes ( 2 ) and flows along the tubes , indirectly transferring heat to the shell-side fluid ( BW) . The shell-side fluid ( BW) , preferably boiling water , enters from the shell-side inlet connection ( SI ) into the shell ( 3 ) , and circulates outside the tubes , cooling the tubes and the tube-sheet .
[0048] Consequently, according to Fig . l , the tube-sheet ( 1 ) corresponds to the tube-side inlet tube-sheet and the firstMNNO I OWO Giovanni Manenti
[0049] portion of exchanging tubes ( 2 ) in correspondence with the tube-sheet ( 1 ) is the tube-side inlet portion of the tubes .
[0050] The exchanger ( HE ) shown in Fi . 1 is generic and several details are purely indicative . For example , the distribution channel ( 4 ) can be connected to the tube-sheet ( 1 ) by welding or flange ; the shell ( 3 ) can be welded or flanged to the tube-sheet ( 1 ) . The shape of the inlet channel ( 4 ) can be any; the channel ( 4 ) can have a spherical , elliptical or conical head, and be provided with a manhole . Tube-side ( TI ) and shell side ( SI ) connections can be welded or flanged type . Other connections may be present for operating the exchanger ( HE ) . The heat exchanger ( HE ) can be installed vertically or horizontally . Typically, quenchers for cracked gases are vertical , with the gas inlet tubesheet at the bottom and the cracked gas flowing into the tubes from bottom to top .
[0051] Fig . 2 schematically shows , in section, the longitudinal view of a portion of the tube-side inlet of the tube-bundle according to a preferential configuration of the present invention . Fig . 2 corresponds to the highlighted detail ( DET ) relating to Fig . 1 . For descriptive simplicity, Fig . 2 shows only one exchanging tube . Fig . 2 indicates , by means of a dotted line ( OTL ) , the circle that envelops the outermost tubes of the tube-bundle . This enveloping circle is characterized by an enveloping diameter ( called "Outside-Tube-Limit ",) . In this description, the enveloping circle or the Outside-Tube-Limit are indicated by the abbreviation "OTL" .
[0052] According to Fig . 2 , the shell ( 3 ) and the channel ( 4 ) are connected to the tube-sheet ( 1 ) by welds (W2 , W3 ) ; the shell and / or the channel can alternatively be connected to the tube-sheet by means of a flange . In accordance with a preferential configuration of the present invention, the channel ( 4 ) is connected to the tube-sheet ( 1 ) in a zone of the tube-sheet placed radially outside the OTL . The tube-sheet ( 1 ) has a shell-side surface ( 5 ) , i . e . a surface facing the shell , and a tube-side surface ( 6 ) , i . e . a surface facing the channel . The first end ( 8 ) of the exchangingMNNO I OWO Giovanni Manenti
[0053] tube ( 2 ) is welded to the first end ( 9 ) of a tube-stub ( 7 ) by means of a first butt-weld (Wl ) ; the exchanging tube and the tubestub have the same longitudinal axis . The heat exchanging tube ( 2 ) is bound to the tube-sheet ( 1 ) through the tube-stub ( 7 ) .
[0054] According to Fig . 2 , the tube-stub ( 7 ) is inserted into the tube-sheet bore along the entire length of the bore ; the second end of the tube-stub ( 10 ) is placed at the tube-side surface ( 6 ) of the tube-sheet in such a way that the second end ( 10 ) is substantially flush with the tube-side surface ( 6 ) . The tube-stub ( 7 ) does not protrude from the tube-side surface of the tube-sheet ( 6 ) . The tube-stub ( 7 ) is so long that the first end thereof ( 9 ) protrudes from the shell-side surface ( 5 ) of the tube-sheet ; in other words , the first butt-weld (Wl ) is positioned on the shellside ( SS ) and the exchanging tube ( 2 ) is not inserted in the tubesheet bore . As a result , the tube-sheet bore is fully engaged, and it is engaged by the tube-stub ( 7 ) only . The tube-stub ( 7 ) is welded to the tube-sheet ( 1 ) by means of a "J" type groove weld (W2 ) that extends along the entire length of the tube-sheet bore ; in other words , the groove weld (W2 ) extends from the tube-side surface ( 6 ) to the shell-side surface ( 5 ) of the tube-sheet . The groove weld (W2 ) is executed so that there is no residual gap between the tube-stub ( 7 ) and the tube-sheet ( 1 ) . The groove weld (W2 ) is executed between the tube-sheet bore and the external surface of the tube-stub, with the welding torch placed on tubeside ( TS ) ; as a result , the welding torch is not positioned inside the tube-stub ( 7 ) .
[0055] According to Fig . 2 , the first butt-weld (Wl ) between the exchanging tube ( 2 ) and the tube-stub ( 7 ) is executed from the outside , i . e . with a welding torch placed outside the tube-stub and the exchanging tube . The first butt-weld (Wl ) is of full penetration type , extending thru the entire thickness of the tube and the welding bead is preferably smoothed on the external surface . The first butt-weld (Wl ) is preferably executed before inserting the heat exchanging tube ( 2 ) into the shell ( 3 ) .MNNO I OWO Giovanni Manenti
[0056] With reference to Fig . 2 , the construction material of the tubestub ( 7 ) and the tube-sheet ( 1 ) is a metal alloy with a high nickel content , i . e . with a nickel content of at least 20% , and more preferably with a nickel content of at least 40% . For example , the construction material for the tube-stub ( 7 ) and / or tube-sheet ( 1 ) may correspond to , or be similar to , one of the following materials according to the German DIN standard : 1 . 4876 , 1 . 4958 , 1 . 4959 , 2 . 4816 , 2 . 4851 , 2 . 4856 , 2 . 4663 , 2 . 4668 and 2 . 4858 .
[0057] With reference to Fig . 2 , the tube-sheet ( 1 ) is formed by a single block or monolith . The tube-sheet is preferably a forged product , then machined, for example to obtain the hubs / flanges for welding the shell and channel and to obtain the bores for the exchanging tubes . The tube-stub ( 7 ) can be a drawn or extruded product ; alternatively, the tube-stub ( 7 ) can be a forged product , possibly machined . Preferentially, the tube-stub ( 7 ) is obtained from a tube .
[0058] It should be noted that the tube-stub ( 7 ) relating to this invention has a cylindrical external surface , substantially smooth . Therefore , the tube-stub ( 7 ) described here has a substantially different structural shape than the connecting element described in the prior-art doc . No . WO 2022 / 049029 .
[0059] With reference to Fig . 2 , the groove weld (W2 ) requires welding filler material ; preferentially, the first butt-weld (Wl ) also requires welding filler material . The welding filler material for the first butt-weld (Wl ) and for the groove weld (W2 ) is a metal alloy with a high nickel content , i . e . with a nickel content of at least 20% , and more preferably with a nickel content of at least 40% . For example , the welding filler material may correspond to , or be similar to , one of the following materials according to the German DIN standard : 2 . 4663 , 2 . 4806 , 2 . 4816 and 2 . 4856 .
[0060] With reference to Fig . 2 , the construction material of the heat exchanging tubes ( 2 ) , the channel ( 4 ) and the shell ( 3 ) is preferably carbon steel or low alloy steel , where the alloyingMNNO I OWO Giovanni Manenti
[0061] elements are preferably Mn, Mo , Ni , Cr , taken as single elements or as a combination of elements .
[0062] Fig . 3 schematically shows , in section, the longitudinal view of a portion of the tube-side inlet of the tube-bundle in accordance with another preferential configuration of the present invention . Fig . 3 corresponds to the highlighted detail ( DET ) relating to Fig . l . For descriptive simplicity, Fig . 3 shows only one heat exchanging tube . Fig . 3 is similar to Fig . 2 and therefore the description of the elements and details equivalent to those of Fig . 2 is omitted, referring to Fig . 2 for the same .
[0063] According to Fig . 3 , the tube-sheet is partially made of high-strength material . The tube-sheet is formed by two axial-symmetrical and concentric pieces : a central disc ( 1A) made of high-strength material and a peripheral ring ( IB ) . The central disc ( 1A) occupies the area where the exchanging tubes ( 2 ) are present and radially extends beyond the OTL . The central disc ( 1A) has a shell-side surface ( 5 ) and a tube-side surface ( 6 ) . The central disc ( 1A) is provided with bores for the heat exchanging tubes ; the tube-stub ( 7 ) is then welded to the central disc ( 1A) . The peripheral ring ( IB ) is connected to the channel ( 4 ) and the shell ( 3 ) . The two concentric pieces ( 1A, IB ) are j oined together by means of an intermediate butt-weld (W5 ) .
[0064] The construction materials in Fig . 3 are substantially equivalent to those of Fig . 2 , with the difference that , for the tube-sheet in Fig . 3 , the central disc ( 1A) is made of metal alloy with a nickel content of at least 20% , and more preferably at least 40% , as for the tube-sheet in Fig . 2 , whereas the peripheral ring ( IB ) is made of carbon or low alloy steel . The central disc ( 1A) is therefore made of high-strength material over its entire thickness . The central disc ( 1A) is preferably obtained by rolling or forging, the peripheral ring ( IB ) is preferably obtained by forging; the two pieces ( 1A, 1B ) are then machined . The welding material for the intermediate weld (W5 ) is equivalent to the material for the groove weld (W2 ) already described in Fig . 2 .MNNO I OWO Giovanni Manenti
[0065] Fig . 4 schematically shows , in section, the longitudinal view of a portion of the tube-side inlet of the tube-bundle in accordance with another preferential configuration of the present invention . Fig . 4 corresponds to the highlighted detail ( DET ) relating to Fig . l . For descriptive simplicity, Fig . 4 shows only one exchanging tube . Fig . 4 is similar to Fig . 2 and therefore the description of the elements and details equivalent to those of Fig . 2 is omitted, referring to Fig . 2 for the same .
[0066] According to Fig . 4 , the tube-sheet ( 1 ) is partially made of high-strength material ; the tube-sheet has a portion made of high-strength material and a portion made of material that is similar from a metallurgical point of view to that of the exchanging tubes . Specifically, the tube-sheet ( 1 ) , on the tube-side ( TS ) , is provided with a protective layer ( 11 ) of high-strength material . The protective layer ( 11 ) extends , at least partially, on the tube-side face ( 6 ) of the tube-sheet . The protective layer ( 11 ) occupies the area where the tube-stubs ( 7 ) are present and radially extends beyond the OTL . The protective layer ( 11 ) , from mechanical design point of view, may be considered an integral part of the tube-sheet ( 1 ) ; in any case , according to the present invention, the protective layer corresponds to a portion of the tube-sheet . The tube-stub ( 7 ) is therefore also welded to the protective layer ( 11 ) . The thickness of the protective layer ( 11 ) is preferably homogeneous and of at least 3mm, more preferably of at least 4mm and even more preferably of at least 6mm. The protective layer ( 11 ) is less thick than the total thickness of the tube-sheet . The protective layer ( 11 ) is preferably obtained by welding overlay, which is executed before drilling the tubesheet .
[0067] The construction materials of Fig . 4 are substantially equivalent to those of Fig . 2 . The protective layer ( 11 ) of the tube-sheet of Fig . 4 is made of metal alloy with a nickel content of at least 20% , preferably at least 40% ; the remaining portion of the tube-sheet is made of carbon steel or low alloy steel . MoreMNNO I OWO Giovanni Manenti
[0068] precisely, the protective layer ( 11 ) is a welding material equivalent to the material related to the groove weld (W2 ) of Fig . 2 . Thus , the tube-side surface of the tube-sheet ( 6 ) is , at least partially, made of high-strength material , while the shellside surface ( 5 ) of the tube-sheet is made of carbon or low-alloy steel .
[0069] It should be noted that , according to a preferential and alternative configuration of the present invention not shown in the figures , the tube-sheet ( 1 ) of Fig . 4 can be formed by two axial-symmetrical and concentric pieces , welded together, as already described for Fig . 3 . In other words , according to a preferential and alternative configuration of the present invention, the tube-side fluid inlet tube-sheet ( 1 ) can be provided, on tube-side ( TS ) , with a protective layer ( 11 ) of high-strength material and the tube-sheet can be formed by two axial-symmetrical and concentric pieces ( 1A, 1B ) j oined together by buttweld ( 5 ) .
[0070] Fig . 5 schematically shows , in section, the longitudinal view of a portion of the tube-side inlet of the tube-bundle in accordance with another preferential configuration of the present invention . Fig . 5 corresponds to the highlighted detail ( DET ) relating to Fig . l . For descriptive simplicity, Fig . 5 shows only one heat exchanging tube . Fig . 5 is similar to Figs . 2 and 4 and therefore the description of the elements and details equivalent to those of Figs . 2 and 4 is omitted, referring to Figs . 2 and 4 for the same .
[0071] According to Fig . 5 , the first end ( 9 ) of the tube-stub ( 7 ) and the first butt-weld (Wl ) do not protrude from the shell-side surface ( 5 ) of the tube-sheet ; in other words , the first end ( 9 ) of the tube-stub ( 7 ) and the first butt-weld (Wl ) are inserted into the tube-sheet bore . The first end ( 8 ) of the heat exchanging tube is also inserted into the tube-sheet bore . As a result , the tube-sheet bore is completely engaged and is engaged by both the tube-stub ( 7 ) and the exchanging tube ( 2 ) . The groove weld (W2 )MNNOIOWO Giovanni Manenti
[0072] of Fig . 5 corresponds to the groove weld (W2 ) of Fig . 2 except that, according to Fig . 5 , the groove weld (W2 ) overlaps the first buttweld (Wl ) and includes a welded joint between the tube-stub and the tube-sheet and a welded j oint between the exchanging tube and the tube-sheet .
[0073] With reference to the preferred configuration of Fi . 5 , the filler material for the groove weld (W2 ) is a metal alloy with a high nickel content, as described for Fig . 2 ; alternatively, a portion of the filler material is high-nickel metal alloy, and another portion is carbon or low-alloy steel . According to a preferential configuration of Fig . 5 , the filler material of the last welding pass, or of the last welding passes , is a metal alloy with a high nickel content; in other words, the filler material for the groove weld (W2 ) in contact with the tube-side fluid is a high-strength material .
[0074] It should be emphasized that the preferential configuration of Fig . 5 , wherein the first end ( 8 ) of the exchanging tube is inserted into the tube-sheet bore, is also applicable to the tube-sheet configuration relative to Figs . 2 and 3. In other words , according to alternative configurations of the present invention, the first end ( 8 ) of the exchanging tube, butt-welded to the tube-stub (7 ) , is inserted into the tube-sheet bore and the tube-sheet has a configuration as described in Figs . 2 or 3.
[0075] According to an alternative configuration of the present invention, not shown in the figures, the first butt-weld (Wl ) is partially inserted into the tube-sheet bore .
[0076] According to the configurations related to this invention, when the first butt-weld (Wl ) is inserted, or partially inserted, into the tube-sheet bore, the tube-stub (7 ) has a relatively small longitudinal extension and possibly less than its external diameter . Therefore, it is underlined that, as per the present invention, when the tube-stub (7 ) has a longitudinal extensionMNNO I OWO Giovanni Manenti
[0077] comparable to or less than its external diameter, it structurally corresponds to a ring .
[0078] Fig . 6a and Fig . 6b schematically show, in section, the longitudinal view of a portion of the tube-side inlet of the tubebundle according to a preferential configuration of the present invention, respectively before and after the groove weld (W2 ) . For descriptive simplicity, Figs . 6a and 6b show only one heat exchanging tube . Fig . 6a and Fig . 6b show the first butt-weld (Wl ) outside the tube-sheet bore , located on shell-side ( SS ) , as for above Figs . 2 , 3 and 4 .
[0079] Fig . 6a shows a portion of the tube-sheet ( 1 ) equivalent to that of Fig . 2 or Fig . 3 or Fig . 4 , the tube-stub ( 7 ) and a portion of the exchanging tube ( 2 ) . The groove weld (W2 ) is absent ; Fig . 6a therefore shows a preferential configuration of the welding groove ( 13 ) relative to the groove weld (W2 ) .
[0080] According to Fig . 6a, the tube-stub ( 7 ) is inserted into the groove ( 13 ) for the entire tube-sheet bore so that the second end ( 10 ) is substantially flush with the tube-side surface of the tube-sheet ( 6 ) ; the tube-stub ( 7 ) does not protrude beyond the tube-side surface ( 6 ) . The welding groove ( 13 ) has a "J" shape and forms a small centring tooth ( 12 ) in correspondence with the shell-side surface ( 5 ) of the tube-sheet . The centring tooth ( 12 ) has a shape comparable to that of a ring and forms the minimum circumferential interstice (LI ) with the external surface of the tube-stub ( 7 ) ; the centring tooth ( 12 ) has the purpose to centre the stub ( 7 ) and holding it in position during welding (W2 ) . The welding groove ( 13 ) has a bevelled bottom or root ( 15 ) , having a chamfering radius ( Rl ) ; the groove ( 13 ) has an inlet ( 14 ) at the tube-side surface ( 6 ) of the tube-sheet . The straight profile of the groove , or the straight part of the "J" shape , is converging towards the tube-stub ( 7 ) ; in other words , the straight profile forms an angle of incidence ( R2 ) with the longitudinal axis (Y ) of the exchanging tube ( 2 ) . According to a preferential configuration relative to Fig . 6a, the straight profile of theMNNO I OWO Giovanni Manenti
[0081] welding groove forms an angle of incidence ( R2 ) , relative to the longitudinal axis (Y ) , between 3 ° and 7 ° . The groove ( 13 ) is designed to facilitate the positioning and entry of the welding torch up to the centring tooth ( 12 ) and to ensure a complete filling of the groove ( 13 ) .
[0082] According to a preferential configuration of the present invention and relative to Fig . 6a , the protrusion ( L3 ) of the tubestub ( 7 ) from the shell-side surface ( 5 ) of the tube-sheet is between 25mm and 150mm, more preferably between 50mm and 100mm .
[0083] It is underlined that , with reference to all the configurations of the present invention, the tube-sheet bore is completely engaged by the tube-stub ( 7 ) or by the tube-stub and the exchanging tube ( 7 , 2 ) . In other words , the tube-stub ( 7 ) is inserted into the tube-sheet bore up to tube-side surface of the tube-sheet ( 6 ) , without protruding from it .
[0084] Fig . 6b is equivalent to Fig . 6a with the difference that the groove weld (W2 ) is present . The groove weld (W2 ) is of fullthickness type , i . e . the weld extends from the shell-side face ( 5 ) to tube-side face ( 6 ) of the tube-sheet ( 1 ) . The groove weld (W2 ) is of full-penetration type , i . e . the weld fills the entire groove ( 13 ) and fuses , at least partially, the centring tooth ( 12 ) ; in other words , the groove weld (W2 ) leaves no residual gap between the tube-sheet ( 1 ) and the tube-stub ( 7 ) . The groove weld (W2 ) is preferentially executed by multiple welding passes . It should be emphasized that the first welding pass , executed with the torch inserted in the groove on tube-side ( TS ) , is executed so to fuse at least partially the centring tooth ( 12 ) and to fill the gap between the centring tooth ( 12 ) and the tube-stub ( 7 ) . The first pass is , preferentially, without addition of welding filler material . The first pass is , preferentially, TIG ( or GTAW ) type . The thickness of the centring tooth ( L2 ) is sized to ensure an adequate fusion . The subsequent welding passes are made with addition of welding material and are aimed at filling the groove ( 13 ) .MNNOIOWO Giovanni Manenti
[0085] According to the preferential configurations of the present invention, and in relation to Fig . 6b, the outer end ( 17 ) ( i . e . the tube-side end of the groove weld W2 ) is substantially flush with the tube-side surface ( 6) of the tube-sheet .
[0086] According to the preferred configurations of the present invention, and in relation to Fig . 6b, the inner end ( 16 ) ( i . e . the shell-side end of the groove weld W2 ) is substantially flush with the shell-side surface (5 ) of the tube-sheet .
[0087] It should be noted that the features and the inventive concepts described for Figs . 6a and 6b are also valid in case the first butt-weld (Wl ) is inserted, or partially inserted, into the tubesheet bore, as described above for Fig . 5 . Consequently, the shape of the welding groove ( 13 ) and the execution of the groove weld (W2 ) as described for Figs . 6a and 6b also apply to the configuration relative to Fig . 5 .
[0088] As already described, the groove weld (W2 ) relative to Fig . 6b can be performed with different welding filler materials . For the configurations of Figs . 2 , 3 and 4 , preferentially, the filler material is a metal alloy with a high nickel content, i . e . with at least 20% nickel, and more preferably with at least 40% nickel . For the configuration of Fig . 5 , preferentially, the filler material deposited at the bottom of the groove ( 15 ) is equivalent to the material of the exchanging tube ( 2 ) and therefore the filler material is equivalent to carbon steel or low alloy steel; the filler material for the subsequent passes is preferably a metal alloy with a high nickel content .
[0089] According to an alternative and preferential configuration of the present invention, the filler material for a portion of the groove weld (W2 ) is made of carbon or low-alloy steel; preferentially, filler material in carbon or low alloy steel is used to weld a portion of tube-sheet in carbon or low alloy steel to the heat exchanging tube in carbon or low alloy steel . According to a preferential configuration of the present invention, theMNNOIOWO Giovanni Manenti
[0090] filler material for welding a first part in carbon or low-alloy steel to a second part in a high-nickel alloy corresponds to an alloy with a high nickel content . For all configurations relating to the present invention, the filler material relating to the last welding pass of the groove weld (W2 ) , i . e . the welding filler material in direct contact with the tube-side fluid, is a metal alloy with a high nickel content, with a minimum of 20% nickel, and more preferably with a minimum of 40% nickel .
[0091] As per the present invention, it is pointed out that carbon or low-alloy steel parts, to be welded to high-nickel alloy parts , may be previously buttered or coated with a high-nickel welding deposit ("buttering" ) . For example, the first end of the exchanging tube ( 8 ) , made of carbon or low alloy steel, can be previously buttered with a high nickel alloy and then be butt-welded (Wl ) to the tube-stub (7 ) , made of a high nickel alloy. Then, the resulting butt-weld (Wl ) takes place between two welding edges with similar metallurgy. This technique is advantageous as, sometime, allows eliminating the subsequent weld heat treatment . Consequently, in accordance with a preferential configuration of the present invention, the parts in carbon or low alloy steel, to be welded to the parts in high-strength material with a high nickel content, can be provided with "buttering" before their welding .
[0092] According to a preferential configuration of the present invention, the tube-stub (7 ) has the same internal diameter as the exchanging tube (2 ) . According to a preferential configuration of the present invention, the tube-stub (7 ) has the same external diameter as the exchanging tube (2 ) . The internal and / or external diameter of the tube-stub ( 7 ) , as per the present invention, can be different from the internal and / or external diameter of the exchanging tube (2 ) ; in such a case, the tube-stub ( 7 ) is preferably tapered in correspondence with the first end ( 8 ) of the exchanging tube .MNNOIOWO Giovanni Manenti
[0093] According to a preferential configuration of the present invention, the second end ( 10 ) of the tube-stub, which is flush with the tube-side surface ( 6 ) of the tube-sheet, is bevelled on the inner surface . As per a preferential configuration, the inner surface of the tube-stub ( 7 ) has a converging profile towards the shell-side .
[0094] According to a preferential configuration of the present invention, the tube-sheet, in the zone delimited by the OTL, has a total thickness between 16mm and 40mm and, more preferably, between 16mm and 30mm. Total thickness means the tube-sheet thickness between the tube-side surface ( 6) and the shell-side surface ( 5 ) .
[0095] According to a preferential configuration of the present invention, the exchanging tubes ( 2 ) have an external diameter between 38 .1mm and 88. 9mm.
[0096] According to a preferential configuration of the present invention, the pitch of the exchanging tubes ( 2 ) has a value between 120% and 160% of the external diameter of the tube-stub (7 ) or of the exchanging tube ( 2 ) .
[0097] It is underlined that the tube-bundle obj ect of the present invention is preferably equipped with straight tubes, tied at the ends to two separate tube-sheets, which at least one of the ends is welded to the tube-stub as described in this invention . However, it is also underlined that a heat exchanger (HE) , according to the present invention, may alternatively have a tubebundle where both ends of the exchanging tubes are welded to a tube-stub, and where the tube-stubs of both ends of the tubes are welded to the tube-sheet as described in this invention . As a result, the present invention provides a solution for heavy-duty tube-bundles with straight tubes applicable to both the tube-side fluid inlet tube-sheet and the tube-side fluid outlet tube-sheet .
[0098] It should be emphasized that the first butt-weld (Wl ) and the groove weld (W2 ) described here are mechanically very resistant .MNNOIOWO Giovanni Manenti
[0099] The groove weld (W2 ) extends over the entire thickness of the tube-sheet bore and therefore the j oining area between the tubestub and the tube-sheet, or between the tube-stub, the exchanging tube and the tube-sheet, is large . Such welds withstand strong tensile loads .
[0100] The tube-bundle obj ect of the present invention, in accordance with the aforementioned characteristics, offers the following advantages :
[0101] 1 ) the groove weld (W2 ) has no residual gaps between the tubestub and the tube-sheet, or between the tube-stub, the exchanging tube and the tube-sheet, and is therefore suitable for pressurized boiling water, flowing on shellside, and for high heat fluxes . As well known, pressurized boiling water and high heat fluxes can deposit salts and impurities in the interstices , causing crevice corrosion. The groove weld (W2 ) obj ect of the present invention eliminates the risk of crevice corrosion from boiling water .
[0102] 2 ) the groove weld (W2 ) is suitable for heat exchanging tubes and tube-sheets subjected to high stresses due to pressure and temperatures, such as tensile stresses caused by the shell-side water pressure acting on the tube-sheet .
[0103] 3 ) the groove weld (W2 ) is practical as the welding torch is not inserted in the tube-stub, unlike for IBW type welding, and the relevant groove ( 13 ) has generous dimensions .
[0104] 4 ) the groove weld (W2 ) allows practical site maintenance as a damaged exchanging tube can be removed and replaced without changing the original design of the tube-sheet . 5 ) the groove weld (W2 ) eliminates the need to mandrel the tube-stub and / or exchanging tube against the tube-sheet .
[0105] 6) The angle of incidence relative to the groove ( 13 ) facilitate the positioning of the welding torch.
[0106] 7 ) The butt-weld (Wl ) between the exchanging tube and the tubestub, when placed on the shell-side, is immersed in theMNNOIOWO Giovanni Manenti
[0107] cooling shell-side fluid and is therefore effectively cooled .
[0108] 8 ) The main pressure parts in contact with the hot tube-side fluid, at exchanger inlet, are made of high-strength material . Therefore, the highest metal temperatures are borne by the high-strength material . Any local overheating or damages on tube-side ( such as corrosion and metallurgical alterations ) are mitigated. In addition, tube-side erosion phenomena are significantly reduced or eliminated as the tube-side fluid, at the inlet, impacts directly on the high-strength material . It is highlighted that the tube-stub allows to avoid the typical erosive phenomena (due to high turbulence) at the entrance of the exchanging tube .
[0109] 9) the welds between high-nickel alloy parts may not require heat treatment .
[0110] The tube-stub (7 ) , based on the invention here disclosed, is positioned flush with the tube-side surface ( 6) of the tube-sheet; this is advantageous as it eliminates a possible point of local turbulence or coke build-up at the inlet of the tubes . In addition, this configuration can facilitate the installation of a possible refractory layer on the tube-side of the tube-sheet .
[0111] It is underlined that the preferential configuration of Fig . 5 allows using a reduced amount of high-strength material for the tube-sheet, and therefore it allows limiting the costs for the construction materials .
[0112] The tube-bundle here disclosed can be assembled as per relatively practical and cost-effective operations , as briefly described below:
[0113] The tube-side fluid inlet tube-sheet is manufactured as shown in Fig . 2 , Fig . 3 or Fig . 4 described above;MNNOIOWO Giovanni Manenti
[0114] The mechanical processing of the tube-sheet is executed to prepare the groove for welding (W2 ) as shown in Fig . 6a above;
[0115] Butt-welds (Wl ) between the tube-stub and the exchanging tube are executed at ground, followed by related nondestructive examinations ;
[0116] The exchanging tubes are inserted into the shell and the tube-stub is positioned in the welding groove;
[0117] the groove weld (W2 ) is executed, followed by related nondestructive examinations .
[0118] The first butt-welding (Wl ) between the exchanging tube and the tube-stub, according to the present invention, can alternatively be executed from inside the tube-stub, i . e . by positioning the welding torch inside the tube-stub .
[0119] A damaged heat exchanging tube belonging to the tube-bundle object of the present invention can be removed and replaced with relatively practical and cost-effective operations , as briefly described below referring to the tube-side fluid inlet tube-sheet only :
[0120] The damaged tube is freed from the tube-sheet, for example by using a cup wheel and by grinding the groove weld (W2 ) ; The damaged tube is removed and the new tube provided with the tube-stub, already butt-welded (Wl ) to the tube, is inserted in the bundle;
[0121] The welding groove of the tube-sheet is cleaned from the old welding material and, if necessary, the original groove is restored, without changing the original design;
[0122] The groove weld is executed between the tube-sheet and the new tube-stub, or between the tube-sheet, the new tube-stub and the new tube, followed by relevant non-destructive examinations .
[0123] A damaged tube belonging to the tube-bundle here disclosed can also be plugged. The plugging is practical and rapid as a suitableMNNOIOWO Giovanni Manenti
[0124] plug of high-strength material is directly welded to the tubestub and / or tube-sheet of same high-strength material; advantageously, the heat treatment is likely not necessary.
[0125] The tube-bundle disclosed here has the advantage that the welds made between high nickel alloy parts , often, do not require heat treatment, whereas this is normally required for carbon and low alloy steel . This is an important potential advantage for site maintenance .
[0126] The tube-bundle obj ect of the present invention is therefore particularly advantageous for cracked gas quenchers or syngas process boilers .
[0127] The tube-bundle object of the present invention is particularly advantageous as it allows a practical and relatively cost-effective manufacturing and maintenance .
[0128] The tube-bundle object of the present invention may be subject to further modifications and variants, all attributable to the same inventive concept, as well as to include details different from those described above without changing the essence of the invention .
[0129] The scope of protection of the present invention is described in the attached claims .
Claims
MNNO I OWO Giovanni ManentiCLAIMS1 . Tube-bundle , part of a heat exchanger ( HE ) of shell-and-tube type essentially cylindrical in shape developed along a longitudinal axis ( Z ) and apt to indirect heat exchange between a tube-side fluid (G ) and a shell-side fluid ( BW ) , where said exchanger ( HE ) comprises at least one tube-sheet ( 1 ) having a shell-side surface ( 5 ) and a tube-side surface ( 6 ) and provided with bores , exchanging tubes ( 2 ) forming said tube-bundle and enveloped by the shell ( 3 ) , at least one distribution channel ( 4 ) placed at said at least one tube-sheet ( 1 ) on the opposite side relative to the shell ( 3 ) and inlet / outlet connections ( T1 , S1 ) for tube-side and shell-side fluids , where said exchanging tubes ( 2 ) have at least a first end ( 8 ) j oined by means of a first butt-weld (Wl ) to a first end ( 9 ) of a tubestub ( 7 ) inserted into the tube-sheet bore so that the exchanging tubes ( 2 ) are in fluid communication with said channel ( 4 ) and so that the second end ( 10 ) of the tube-stub ( 7 ) is substantially flush with said tube-side surface ( 6 ) , where said tube-stub ( 7 ) or said tube-stub and exchanging tube ( 7 , 2 ) are j oined to said tube-sheet ( 1 ) by means of a groove weld (W2 ) having a groove ( 13 ) of "J" shape , said tube-bundle being characterized in that said groove weld (W2 ) extends from the shell-side surface ( 5 ) to the tube-side surface ( 6 ) of the tube-sheet without leaving any residual gap between the tubesheet ( 1 ) and the tube-stub ( 7 ) or between the tube-sheet ( 1 ) and the tube-stub and exchanging tube ( 7 , 2 ) , and in that the material of said exchanging tubes ( 2 ) is carbon steel or low alloy steel , and the material of said tube-stub ( 7 ) , at least a portion of said groove weld (W2 ) and at least a portion of said tube-sheet ( 1 , 1A, 11 ) , where said at least a portion of tube-sheet ( 1 , 1A, 11 ) radially extends at least over the entire area delimited by the enveloping circle (OTL ) of the tubebundle , is a metal alloy with a nickel content of at least 20% .2 . Tube-bundle as per claim 1 , wherein said metal alloy has a nickel content of at least 40% .MNNO I OWO Giovanni Manenti3 . Tube-bundle as per claim 1 or 2 , wherein said first butt-weld (Wl ) is placed on shell-side ( SS ) outside the tube-sheet bore .4 . Tube-bundle as per claim 1 or 2 , wherein said first butt-weld (Wl ) is placed inside , or partially inside , the tube-sheet bore .5 . Tube-bundle as per any claim 1 to 4 , wherein said at least a portion of tube-sheet ( 11 ) corresponds to a protective layer placed at said tube-side surface ( 6 ) , having a thickness of at least 3mm and less than the total thickness of the tube-sheet , and obtained by weld overlay .6 . Tube-bundle as per any claim 1 to 4 , wherein said at least a portion of tube-sheet ( 1 ) has a thickness equivalent to the total thickness of the tube-sheet .7 . Tube-bundle as per any previous claim, wherein said tube-sheet is formed by a central disc ( 1A) , radially extending at least for the entire area delimited by the enveloping circle ( OTL ) of the tube-bundle , and by a peripheral ring ( IB ) , wherein said central disc ( 1A) and said peripheral ring ( IB ) are each other concentrically arranged, with the ring ( IB ) radially externally placed relative to the disc ( 1A) , and j oined by an intermediate butt-weld (W5 ) .8 . Tube-bundle as per any previous claim, wherein said groove ( 13 ) has a root ( 15 ) with a chamfer radius ( Rl ) and has a straight profile forming an angle of incidence ( R2 ) relative to the longitudinal axis ( Y ) of the exchanging tube ( 2 ) , and wherein said groove ( 13 ) forms a centring tooth ( 12 ) , at said shellside surface ( 5 ) , forming a minimum circumferential gap with the tube-stub ( 7 ) or the exchanging tube ( 2 ) .9 . Tube-bundle as per claim 8 , wherein said angle of incidence is between 3 ° and 7 ° .10 . Tube-bundle as per any previous claim, wherein the tube-sheet ( 1 ) in the area delimited by the enveloping circle (OTL ) of the tube-bundle has a total thickness between 16mm and 40mm.11 . Tube-bundle as per any previous claim, wherein said centring tooth ( 12 ) is at least partially fused during the first weldingMNNOIOWO Giovanni Manentipass relating to said groove weld (W2 ) , with the welding torch placed on tube-side (TS ) and outside the tube-stub ( 7 ) .12 . Tube-bundle as per any previous claim, wherein said groove weld (W2 ) is executed by one or more welding passes with filler material, with the welding torch placed on tube-side (TS ) and outside the tube-stub ( 7 ) .13 . Tube-bundle as per any previous claim, wherein the filler material of the last welding pass relating to said groove weld (W2 ) , in direct contact with the tube-side fluid (G) , is made of said metal alloy.