JP2007071360A - High temperature hollow member reinforcing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extremely easy method of reinforcing a high temperature hollow member such as a high temperature pipe for offering a sufficient effect of improving creeping durability and basic versatility applicable to all regions. <P>SOLUTION: A flexible long ceramic fiber material which has a thermal expansion coefficient lower than that of a base material for the high temperature hollow member is wound on the high temperature hollow member. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for reinforcing a high-temperature hollow member such as a high-temperature pipe or a pressure vessel used in a thermal power / nuclear power plant, a chemical plant, etc., and particularly a base material of a steam pipe used in a boiler, a turbine, etc. It is effective in increasing the creep durability in

  For example, high-temperature pipes such as boiler steam pipes used in power plants generate creep voids (small gaps of about 1/1000 mm) due to high temperature (usually about 450 ° C or higher) and creep damage due to prolonged use. Further, a crack is generated by the connection of the generated creep voids, and when this crack grows, it finally breaks. Accordingly, it is very important to accurately grasp the creep damage state and to evaluate the remaining life of the member from the viewpoint of preventing the trouble and determining the renewal time of the member.

  For the remaining life evaluation, an evaluation method based on a structure change, a hardness change, and the like has been proposed and put into practical use. However, although these evaluation factors change greatly in the first half of the life consumption rate, there is little change when the second half of the life consumption rate is reached, so the remaining life evaluation accuracy in the second half of the life consumption rate is low. is there. Therefore, paying attention to the creep strain rate, there is an attempt to increase the accuracy of the remaining life evaluation even in the latter half of the life consumption rate (Patent Document 1).

JP 2003-4626 A

  Increasing the accuracy of the remaining life evaluation is an important research theme, but if the life of high temperature pipes can be extended by preventing the progress of creep damage, the number of pipe repairs and replacements should be reduced. In addition to reducing maintenance costs, it is possible to increase productivity by reducing the frequency of plant shutdowns for maintenance, and research in that direction is also beneficial.

  As an example of the technology in this viewpoint, there is one disclosed in Patent Document 2. This uses a regenerator that includes a clamp that restrains the expansion of the creep deteriorated part to be regenerated and a heating means that heats the creep deteriorated part, and uses the internal pressure of the generated thermal expansion to The crack is pressed and repaired to extend the life. Incidentally, a general repairing method is a method of removing a portion having creep voids or cracks and overlay welding the portion.

  Alternatively, there is one disclosed in Patent Document 3. This is to attach to the pipe a stress distribution member that reduces or disperses the stress acting on the pipe due to the pressure received from the steam in the pipe. Specifically, the bar or plate that exhibits resistance to stress is stressed. By using it as a dispersion member, the creep durability is being improved.

JP 2003-253337 A JP 2004-176791 A

  However, in the former case, since heat is applied to the existing piping from the outside, there is a possibility that the material structure may change and there is a possibility that the strength may be reduced, so this is not performed for safety. In addition, setup such as installation of the playback apparatus is extremely complicated. Furthermore, the former does not actively prevent the progress of creep damage, but is used only for the purpose of repair after the fact, and cannot be a permanent measure.

  On the other hand, the latter actively prevents creep damage from progressing by increasing creep durability, and it can be a permanent measure. It is not preferable for safety. In addition, it has to undergo national welding inspection, which is not practical due to labor and cost. In addition, there is a problem that the application location is limited to a bent part (elbow pipe or the like) of a pipe or a butt weld part between pipes.

  Therefore, the present invention has been made in view of the above problems, and is a very simple high-temperature hollow member that has a sufficient effect of increasing creep durability and is versatile enough to be applied basically to the entire region. It is an object of the present invention to provide a reinforcing method.

  The present invention for solving the above-mentioned problems is a method for reinforcing a high-temperature hollow member such as a high-temperature pipe, wherein a long ceramic fiber material having a lower coefficient of thermal expansion and flexibility than a base material of the high-temperature hollow member is replaced with a high-temperature hollow member. It is characterized by being wound around a member.

  According to the present invention, when a high temperature hollow member is heated by supplying a high temperature fluid into a high temperature hollow member wound with a ceramic fiber material, the high temperature hollow member tends to expand due to a difference in thermal expansion coefficient between the ceramic fiber material and the high temperature hollow member. The ceramic fiber material generates a force to compress the high-temperature hollow member in the radial direction against the high-temperature hollow member, and this compressive stress crushes the creep void or suppresses the generation and connection of the creep void. .

  For example, in the case of a high-temperature hollow member having a welded portion along the longitudinal direction, tensile stress is generated in a direction orthogonal to the welded portion due to expansion of the high-temperature hollow member, but the ceramic fiber material reduces this. Or work in the direction of elimination. Creep voids are particularly likely to occur in weld heat affected zones (base metal parts close to the weld zone), but the compressive stress associated with the action of such ceramic fiber material can suitably collapse the creep voids, and generate and connect creep voids. Can be suppressed.

  In addition, if attention is focused only on the welding heat affected zone, the ceramic fiber material is wound around the high temperature hollow member, which means that each ceramic fiber is fixed on the surface of the high temperature hollow member with the welding heat affected zone interposed therebetween. Therefore, it can be said that the reinforcing effect on the weld heat affected zone is extremely high.

  Here, it goes without saying that the ceramic fiber material has a strength that is not broken (cut) even with respect to the elongation in the circumferential direction accompanying the expansion of the high-temperature hollow member. In addition, the ceramic fiber material does not necessarily have to be stretched. In short, if the elongation rate is lower than the elongation in the circumferential direction of the high temperature hollow member accompanying expansion, compressive stress is generated in the high temperature hollow member. It is possible to crush creep voids and to suppress the generation and connection of creep voids.

  In addition, if the facility is operated, a high-temperature fluid such as steam flows in the high-temperature hollow member. Therefore, in carrying out the present invention, it is only necessary to wrap the ceramic fiber material around the high-temperature hollow member. Prior to the operation of the equipment, the high temperature fluid may be spontaneously supplied into the high temperature hollow member.

  Another aspect of the present invention is a reinforcing method for butt-welding high-temperature hollow members such as high-temperature pipes, such that a long reinforcing material straddles a butt-welded portion between high-temperature hollow members and along the longitudinal direction. And a long ceramic fiber material having a lower coefficient of thermal expansion than the base material of the high-temperature hollow member and having flexibility is wound around the reinforcing material.

  In addition to the same effects as the first aspect of the present invention, the present invention can be restrained from bending stress and torsional stress in the high-temperature hollow member by being restrained by the reinforcing material. Therefore, the high-temperature hollow member is effective for use in an environment where bending due to its own weight or mechanical vibration is likely to occur.

  In these inventions, a high-temperature hollow member rounds one plate material into a tubular shape and welds edges to each other so that a high-temperature pipe having one welded portion continuous in the longitudinal direction or a pair of halved shapes It is suitable for a high-temperature pipe having two welded portions that are continuous in the longitudinal direction at opposite positions by welding the end edges in the longitudinal direction by fitting the pipe member into a tubular shape.

  Moreover, these inventions can employ a configuration in which the ceramic fiber material is entirely wound so as to cover the high temperature hollow member, or a configuration in which the ceramic fiber material is wound so that a part of the high temperature hollow member is exposed. In the former case, the reinforcing effect is extremely excellent. In the latter case, since the metal structure of the base material or the welded portion can be observed, the remaining life can be evaluated and the safety and reliability of the equipment can be improved.

  Moreover, these inventions can use any one or two or more types of ceramic fibers of carbon-based, carbide-based, oxide-based, and nitride-based ceramic fiber materials. In that case, the ceramic fiber material is a bundle of a single type of ceramic fibers, a mixture of different types of ceramic fibers or a mixture of different types of ceramic fibers appropriately, Or what weaved ceramic fiber and made into tape shape can be adopted.

  Also, for the purpose of reducing stress concentration at the contact portion between ceramic fibers and high-temperature hollow member or between the ceramic fibers, or for preventing fiber scattering and improving workability when wrapping ceramic fiber material around high-temperature hollow member Alternatively, a composite ceramic fiber material in which a polymer or a malleable metal that does not impair the flexibility of the ceramic fiber material is disposed in the gap between the ceramic fibers may be used.

  As described above, according to the present invention, a ceramic fiber material is wound around a high-temperature hollow member such as a high-temperature pipe, and a high-temperature fluid is supplied to the inside, thereby crushing a creep void or suppressing generation / connection of a creep void. Therefore, the creep durability of the high-temperature hollow member is increased, and the progress of creep damage can be inhibited. As a result, the life of the high-temperature hollow member can be extended. Moreover, since it is only necessary to wrap the ceramic fiber material in a state where a predetermined tension is applied, the construction can be performed very easily and the ceramic fiber material has flexibility, so that it is basically applied to the entire region of the high-temperature hollow member. be able to.

  High-temperature piping used in boilers, turbines, etc. is generally a pipe structure in which a pair of halved pipe members are combined into a tubular shape and the edges are welded in the longitudinal direction (so-called monaca matching structure) One plate material is rounded into a tubular shape and the edges are welded together to form a piping structure (so-called plate bending longitudinal welded structure). Moreover, the ends of these pipes are welded together to construct a piping system. Below, embodiment which concerns on this invention is described for these piping.

  FIG. 1 (a) shows a straight pipe 1 having the above-described so-called plate bending longitudinal weld structure and having one welded portion 1 'continuous along the longitudinal direction. FIG. 2B shows an elbow tube 2 having the above-described monaca matching structure and having two welds 2 'and 2' that are continuous in the longitudinal direction at opposite positions. FIG. 6 (c) shows a continuous butt weld portion 3 ′ that is continuous in the circumferential direction at the connecting portion (the end portion of the straight tubes 1 and 1) by butt welding the straight tubes 1 and 1 to each other. This is a piping structure 3. As an example, each pipe is made of steel having a diameter of 700 mm, a wall thickness of 50 mm, and a material of 2.25Cr-1Mo steel.

  The feature of this embodiment lies in that a ceramic fiber material having a low coefficient of thermal expansion and a low specific gravity as compared with the pipe base material is wound around the pipe and fixed. Due to the difference in coefficient of thermal expansion between the pipe and the ceramic fiber material when the pipe around which the ceramic fiber material is wound rises in temperature, the ceramic fiber material moves the pipe inward in the radial direction with respect to the pipe to be expanded (and expanded in diameter). A force to compress is generated, and this compressive stress crushes creep voids (especially easily generated in the heat-affected zone in the vicinity of the weld), suppresses the generation and connection of creep voids, and increases creep durability. It is possible to inhibit the progress of creep damage.

  Heat input for raising the temperature is given by supplying a high-temperature and high-pressure fluid inside the pipe. Normally, steam (temperature 600 ° C., vapor pressure 4 MPa) is inevitably inside the pipe due to operation of a boiler, a turbine, or the like. It is sufficient because it is fluid.

  A spiral line L illustrated in FIGS. 1A to 1C indicates a procedure (trajectory) for winding a ceramic fiber material. And although the winding thickness (thickness of a ceramic fiber material layer) of a ceramic fiber material changes with the diameter and thickness of piping, since it is preferable that it is about 1-20 mm, as a ceramic fiber material, it is tape-shaped (band shape) The ceramic fiber material is wound while gradually shifting in the longitudinal direction of the pipe so that there is no level difference, and the entire pipe is covered with the ceramic fiber material.

  The ceramic fiber material is wound around the pipe while unwinding what is wound on the roll, but the tension is applied to the ceramic fiber material by separating the roll from the pipe so that a certain amount of tension is applied to the winding. It is preferable that the ceramic fiber material is wound around the pipe while adding a roll.

  In addition, the ceramic fiber material is fixed in a shrink-fitted state due to the difference in thermal expansion from the piping, but just in case, an adhesive is applied over the entire length of the ceramic fiber material or at the terminal and an appropriate place between them. It is also preferable to apply and prevent the ceramic fiber material from loosening with respect to the piping with the adhesive. In this case, the adhesive is preferably a ceramic adhesive because of its affinity with the ceramic fiber material.

  As described above, in this embodiment, the temperature of the pipe around which the ceramic fiber material is wound is increased, and a compressive stress is generated in the pipe (mainly in the hoop direction) using the difference in thermal expansion between the ceramic fiber material and the pipe. is there. By compressing the pipe with hoop stress, void defects such as creep voids in the metal structure of the welded part and base metal caused by aging and manufacturing defects are crushed, and generation and connection of creep voids are suppressed. The As a result, creep durability is improved, and the life of the pipe can be extended.

  In addition, particularly in the case shown in FIG. 1C, since the reinforcing fiber 4 is disposed so as to straddle the welded portion 3 ′ and the ceramic fiber material is wound, the continuous piping structure 3 is caused by its own weight or mechanical vibration. Even if it is going to bend, it can be prevented from being bent or torsionally stressed in the piping by the reinforcing material 4, and therefore, a case different from FIG. Since the welded portion is formed in the circumferential direction of the pipe, the creep durability in the vicinity of the welded portion 3 ′ can be improved even in a case where the directionality of the welded portion and the direction of winding of the ceramic fiber material substantially coincide. it can. In one example, the reinforcing material 4 is a member having a maximum thickness of 20 mm and a maximum length of 10 m (ceramic fiber composite material, or metal such as stainless steel, chromium alloy, nickel alloy, titanium alloy, invar, low alloy steel, etc. Heat-resistant alloy).

  Here, the ceramic fibers can be broadly classified into carbon-based materials such as pitch-based carbon fibers and PAN-based carbon fibers, carbide-based materials such as silicon carbide fibers, oxide-based materials such as alumina fibers, and nitride-based materials such as silicon nitride fibers. Any one of the above-mentioned ceramic fibers, which has a higher breaking strength against the thermal expansion effect of the pipe and can be selected depending on the temperature reached after the pipe is heated, is not consumed due to oxidation or the like.

Specifically, for example, the trade name “Torayca” manufactured by Toray Industries, Inc. can be selected as the carbon system, and as the carbide system, for example, Si—Ti—C—O, Si—Zr—C—O, or Si -Trade name “Tyranno Fiber” (registered trademark) manufactured by Ube Industries, Ltd., which is a fiber made of Al—C—O, and “Nicalon” (trade name, manufactured by Nippon Carbon Co., Ltd., which is a fiber made of Si—C—O. Registered trademark) and trade name "Hynicalon" (registered trademark), SCS series fiber manufactured by Textron, USA, US-made product name "HPZ fiber" manufactured by Dow Corning, USA Inorganic reinforcing fibers substantially consisting of Si, C, O, and B described in Patent Specification No. 5,366,943 can be selected. Examples of the oxide system include, for example, U.S. DuPont, U.S. 3M, Each A made by Sumitomo Chemical Co., Ltd. ₂ O ₃ fibers can be selected, as the nitride, for example, it is possible to select the Si ₃ N ₄ fibers made Tonen Corporation. However, under the maximum compressive stress generated in the pipe, taking into consideration the pipe base material (compressive buckling strength), the temperature range of the pipe, the thermal expansion coefficient, Young's modulus and Poisson's ratio of the pipe base and ceramic fiber However, it is selected so as not to compress and buckle the piping.

  In addition, these fibers are usually marketed by bundling hundreds to thousands of single fibers and wound on a bobbin. However, these fibers are woven into a woven cloth to form a tape (band). Used as ceramic fiber material. Specifically, a plurality of fiber bobbins are set on a weaving machine and woven (by a method such as plain weaving, satin weaving, or braiding) to produce a ceramic fiber material. The merit of folding ceramic fiber is that it can be handled as a woven fabric, so it is easy to handle, and it can be applied to the entire area of the piping because it can be flexibly changed in shape with a three-dimensional curvature. It is. Moreover, even if the fiber bundle is cut, the strength is maintained by the other fibers forming the woven fabric, and the durability as the ceramic fiber material is ensured.

  As piping, it will be a base material whose coefficient of thermal expansion is higher than the above-mentioned ceramic fibers, for example, carbon steel pipe, alloy steel pipe, stainless steel pipe, pressure vessel steel sheet, carbon steel forged steel, Alloy steel forging, carbon steel, nickel chrome steel, nickel chrome molybdenum steel, chrome steel, aluminum chrome molybdenum steel, rolled steel, stainless steel rod, stainless steel plate, heat resistant steel plate, carbon steel cast steel, stainless cast steel Products, cast steel products for high temperature and high pressure, cast iron products, Ni-base heat-resistant alloy materials, etc. can be selected.

Here, the material mechanical support of the pipe reinforcement method according to the present embodiment will be verified.
P ₁ : Internal pressure of piping P ₂ : Internal pressure applied by piping to ceramic fiber material = External pressure applied by ceramic fiber material to piping P ₃ : External pressure applied to ceramic fiber material from outside (= 0)
σ ₁ : Circumferential stress on the outer peripheral surface of the pipe m ₁ : Poisson's ratio of the pipe m ₂ : Poisson's ratio of the ceramic fiber material E ₁ : Young's modulus of the pipe E ₂ : Young's modulus of the ceramic fiber δ: Pipe of the pipe due to thermal expansion Radius increase amount R ₁ : Inner radius of piping R ₂ : Outer radius of piping R ₃ : Winding outer radius of ceramic fiber material The following relationship is established.

That is, when the ceramic fiber material is wound around the pipe, σ ₁ (circumferential stress acting on the outer peripheral surface of the pipe) is reduced by {(R ₁ ² + R ₂ ² ) / (R ₂ ² −R ₁ ² )} P _2. It is done. Accordingly, the creep life of the pipe is increased by reducing the outer σ _1, which is the site where the creep damage is greatest. If 2R ₁ ² P ₁ <(R ₁ ² + R ₂ ² ) P ₂ , σ ₁ becomes negative and compression occurs. This crushes the creep void and restores life.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of this invention.

  For example, as in the above embodiment, the ceramic fiber material may be permanently wound around the pipe, but the treatment (creep void elimination treatment: detoxification treatment) is completed, and the creep durability of the pipe and the like is improved. If so, it may be removed at that time.

  Moreover, in the said embodiment, although the ceramic fiber material which woven the bundle-like ceramic fiber is used, you may make it wind around piping etc. with a bundle-like fiber.

  Further, the ceramic fiber material may be composed of a single type of ceramic fiber, or a mixture of different types of ceramic fibers may be appropriately mixed to form a bundle, or a bundle of different types of ceramic fibers may be mixed together to form a bundle. You may make it wind around piping etc., or you may make it wrap around the piping etc. what weaved the mixed fiber and made it tape-shaped (band | belt shape).

  In order to reduce the stress concentration at the contact portion between ceramic fibers and piping, or between the ceramic fibers, or to prevent fiber scattering and improve workability when wrapping ceramic fiber material around piping, etc. You may use the composite ceramic fiber material which has arrange | positioned the polymer and the malleable metal which do not impair the softness | flexibility of a fiber material in the clearance gap between ceramic fibers.

  Moreover, in the said embodiment, although the ceramic fiber material is wound around the whole area | region of piping, it may be local. In that case, a method of obtaining a location where creep damage is likely to proceed by a mechanical analysis result such as a finite element method and determining the location as a winding location is considered as an example.

  Further, in the above embodiment, the pipe is covered with the ceramic fiber material to such an extent that the surface is invisible. However, as shown in FIG. As shown in (b), the surface of the pipe or the like may be partially exposed by winding the ceramic fiber material at two adjacent positions and forming the non-winding portion 5 between the two positions. In this case, since the metal structure of the base material or the welded portion can be observed, the remaining life can be evaluated together, and the safety and reliability of the equipment can be improved.

  Further, in the above embodiment, the ceramic fiber material is wound directly around the pipe. However, in order to prevent damage to the ceramic fiber or to adjust the contact area with the pipe or the like, coating with boron nitride or the like is performed. The ceramic fiber material may be wound in a state in which a solid lubricating substance that reduces the friction coefficient is applied to the surface of a pipe or the like by spraying or brushing.

  Moreover, in the said embodiment, although the ceramic fiber material is wound around the existing piping, piping etc. which wound the ceramic fiber material from the beginning are prepared, and this can also be used at the time of equipment construction. It is. In this case, since the strength is increased by winding the ceramic fiber material, it is possible to reduce the thickness of the base material or switch to a lower material, thereby enabling cost reduction.

It is explanatory drawing of the reinforcement method of the high temperature piping which concerns on this embodiment. It is explanatory drawing of the reinforcement method of the high temperature piping which concerns on other embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Straight pipe, 1 '... Welded part, 2 ... Elbow pipe, 2' ... Welded part, 3 ... Continuous piping structure, 3 '... Welded part (butt welding part), 4 ... Reinforcement material, 5 ... Unwrapped part, L ... winding line of ceramic fiber material

Claims (9)

  A method for reinforcing a high-temperature hollow member such as a high-temperature pipe, wherein a long ceramic fiber material having a lower coefficient of thermal expansion and flexibility than a base material of the high-temperature hollow member is wound around the high-temperature hollow member. A method for reinforcing a hollow member.   A high-temperature hollow member such as a high-temperature pipe is reinforced by butt welding each other, and a long reinforcing material is disposed so as to straddle the butt-welded portion between the high-temperature hollow members and along the longitudinal direction, and the high-temperature hollow member A method for reinforcing a high-temperature hollow member, characterized in that a long ceramic fiber material having a lower coefficient of thermal expansion and flexibility than the base material is wound around the reinforcing material.   The high-temperature hollow member is a high-temperature pipe having one welded portion continuous in the longitudinal direction, or a pair of halved pipe members, by rounding one plate into a tube and welding the edges together. The reinforcement of the high-temperature hollow member according to claim 1 or 2, wherein the high-temperature hollow member has two welded portions continuous in the longitudinal direction at opposite positions by welding the edges in the longitudinal direction in accordance with the tubular shape. Method.   The method for reinforcing a high-temperature hollow member according to any one of claims 1 to 3, wherein the ceramic fiber material is entirely wound so as to cover the high-temperature hollow member.   The method for reinforcing a high-temperature hollow member according to any one of claims 1 to 3, wherein the ceramic fiber material is wound so that a part of the high-temperature hollow member is exposed.   The high-temperature hollow member according to any one of claims 1 to 5, wherein any one of carbon-based, carbide-based, oxide-based, and nitride-based ceramic fibers or two or more ceramic fibers is used as the ceramic fiber material. Reinforcement method.   The method for reinforcing a high-temperature hollow member according to claim 6, wherein the ceramic fiber material is a bundle of ceramic fibers.   The method for reinforcing a high-temperature hollow member according to claim 6, wherein the ceramic fiber material is formed by weaving ceramic fibers into a tape shape.   The method for reinforcing a high-temperature hollow member according to any one of claims 6 to 8, wherein a polymer or a malleable metal is disposed in a gap between ceramic fibers constituting the ceramic fiber material.

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