Method and apparatus for manufacturing coated tubular members

Abstract

A uniform carbon vapor-deposited film with low scale adhesion is formed inside a tubular member. [Solution] The manufacturing apparatus 100a includes two lids 21 and 22, each attached to the open ends 11 and 12 on both sides of the tubular member 1 in the axial direction, and having through holes 23 and 24, respectively; an outlet section 32 for guiding gas from inside the tubular member 1 through the through hole of one of the two lids 21 and 22; an introduction section 31 for introducing raw material gas for amorphous carbon deposition film and plasma forming gas into the tubular member 1 through the through hole of the other lid 21 and 22; an axial electrode 5 disposed inside the tubular member 1 and movable along the tubular direction; and a power supply that applies a voltage between the tubular member 1 and the electrode 5 to generate plasma near the tip of the electrode 5 inside the tubular member 1.

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for manufacturing a coated tubular member, in which an amorphous carbon deposited film is formed on the inner surface of the tubular member.

Background Art

[0002] In geothermal power generation, steam turbine blades are rotated by the thermal energy of high-temperature and high-pressure geothermal steam to generate electric power. At this time, the temperature and pressure of the geothermal steam deprived of energy decrease. When the temperature and pressure of the high-temperature and high-pressure geothermal steam decrease, silica, calcium, iron sulfide and the like dissolved in the steam precipitate and deposit on the surfaces of the turbine blades. As this deposition progresses, the flow path through which the geothermal steam flows is blocked. This is called scaling. Scaling causes unexpected power plant shutdowns, reduces the operating rate of geothermal power plants, and significantly lowers the power generation amount of geothermal power plants. For this reason, attempts have been made to prevent scaling.

[0003] In Patent Document 1, scaling is prevented by forming an amorphous carbon film on the inner surface of a tubular member constituting geothermal power generation equipment. FIG. 5 is a diagram showing a conventional coated tubular member manufacturing apparatus 100 disclosed in Patent Document 1.

[0004] In FIG. 5, the tubular member 1 is a member constituting geothermal power generation equipment, has open ends 11 and 12 on both sides in the tube axis direction, and has a hollow portion penetrating between the open ends 11 and 12. In this manufacturing apparatus 100, an amorphous carbon deposited film is formed on the inner surface of the hollow portion of the tubular member 1.

[0005] A lid body 21 having a through hole 23 opened therein is attached to the open end 11 of the tubular member 1. Further, a lid body 22 having a through hole 24 opened therein is attached to the open end 12 of the tubular member 1. The introduction part 31 is a means for introducing a plasma forming gas and a raw material gas g into the tubular member 1 through the through hole 23. The lead-out part 32 is a means for leading out the gas v from the inside of the tubular member 1 through the through hole 24.

[0006] The covers 21 and 22 also function as electrodes and are each grounded. The tubular member 1 is entirely made of a conductive material, or its outer surface is covered with a conductive material. During the film deposition operation, the tubular member 1 functions as an electrode. Here, the covers 21 and 22 are electrically insulated from the tubular member 1. The outer surface of the tubular member 1 is connected to the negative electrode of the power supply 4. The positive electrode of this power supply 4 is grounded, and during the film deposition operation, it outputs a negative voltage or pulse voltage from the negative electrode to the tubular member 1.

[0007] During the film deposition process, the inside of the tubular member 1 is depressurized. This depressurization can be achieved by releasing the gas v from inside the tubular member 1 through the through-hole 24 of the lid 22. While maintaining this depressurization, the raw material gas for the carbon vapor deposition film is introduced through the through-hole 23 of the lid 21. The raw material gas includes a hydrocarbon gas that serves as a carbon source and optionally a hydrogen source for the carbon vapor deposition film, and a nitrogen gas that serves as an optionally a nitrogen source for the carbon vapor deposition film. Examples of hydrocarbon gases that can be used include methane, ethane, and acetylene. A voltage is then applied to the tubular member 1 to generate plasma p along the entire length of the tubular member 1 in the axial direction. This allows the carbon vapor deposition film to be formed along the entire length of the tubular member 1 in the axial direction. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2024 / 172067 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, in the conventional technology described above, since the film is deposited while gas is flowing, as the gas flows from upstream (lid 21 side) to downstream (lid 22 side), hydrocarbon gases are consumed in the deposition of the carbon vapor-deposited film, resulting in a concentration and pressure distribution in which the concentration and pressure of hydrocarbon gases decrease as they move from the upstream side to the downstream side within the tubular member 1. Since gas concentration and pressure greatly affect the chemical structure of the carbon vapor-deposited film, the conventional technology has the problem of not being able to deposit a uniform film within the tubular member 1. In addition, the low scale adhesion (ability to suppress scale adhesion) of the carbon vapor-deposited film largely depends on its chemical structure. For this reason, the conventional technology has the problem of not being able to obtain low scale adhesion across the entire surface inside the tubular member 1.

[0010] This invention has been made in view of the circumstances described above, and aims to provide a technical means for forming a uniform carbon vapor-deposited film with low scale adhesion inside a tubular member. [Means for solving the problem]

[0011] This invention provides a method for manufacturing a coated tubular member, wherein an amorphous carbon vapor-deposited film is formed on the inner surface of a tubular member, by arranging an electrode movable along the axial direction of the tube inside a hollow tubular member, introducing a raw material gas for an amorphous carbon vapor-deposited film and a plasma-forming gas into the tubular member while guiding a gas out from inside the tubular member, and applying a voltage between the tubular member and the electrode to generate plasma near the tip of the electrode inside the tubular member while moving the electrode in the axial direction of the tube.

[0012] In a preferred embodiment, the electrode has an insulating material covering the tip located inside the tubular member.

[0013] In another preferred embodiment, two lids, each having a through hole, are attached to the open ends on both sides of the tubular member in the axial direction, and gas is discharged through the through hole of one of the two lids, while gas is introduced through the through hole of the other lid.

[0014] In another preferred embodiment, the electrode has an axially extending through hole, through which gas is introduced into the tubular member.

[0015] Furthermore, this invention provides a manufacturing apparatus for a coated tubular member, wherein an amorphous carbon vapor-deposited film is formed on the inner surface of the tubular member, comprising: an outlet for releasing gas from inside the hollow tubular member; an introduction for introducing a raw material gas for an amorphous carbon vapor-deposited film and a plasma-forming gas into the tubular member; an axial electrode disposed inside the tubular member and movable along the axial direction of the tube; and a power supply that applies a voltage between the tubular member and the electrode to generate plasma near the tip of the electrode inside the tubular member.

[0016] In a preferred embodiment, the hollow tubular member has two lids, each with a through hole, which are attached to the open ends on both sides in the axial direction of the tubular member. The discharge section discharges gas from inside the tubular member through the through hole in one of the two lids, and the introduction section introduces gas into the tubular member through the through hole in the other of the two lids.

[0017] In another preferred embodiment, the electrode has an insulating material covering the tip located inside the tubular member.

[0018] In another preferred embodiment, the electrode has an axially extending through hole, and the introduction portion introduces gas through the through hole of the electrode. [Effects of the Invention]

[0019] According to this invention, plasma is generated near the tip of the electrode, and the tip of the electrode moves in the axial direction of the tubular member. This prevents the carbon vapor-deposited film formed on the inner surface of the tubular member from becoming non-uniform along the axial direction, and makes it possible to form a carbon vapor-deposited film with low scale adhesion. [Brief explanation of the drawing]

[0020] [Figure 1] This figure shows the configuration of a manufacturing apparatus for a coated tubular member, which is a first embodiment of this invention. [Figure 2] This is a diagram showing the configuration of an apparatus for manufacturing a coated tubular member that is the second embodiment of the present invention. [Figure 3] This is a diagram showing the configuration of an apparatus for manufacturing a coated tubular member that is the third embodiment of the present invention. [Figure 4] This is a diagram showing the configuration of an apparatus for manufacturing a coated tubular member that is the fourth embodiment of the present invention. [Figure 5] This is a diagram showing the configuration of a conventional apparatus for manufacturing a coated tubular member. [Modes for Carrying Out the Invention]

[0021] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0022] <First Embodiment> Figure 1 is a diagram showing the configuration of an apparatus 100a for manufacturing a coated tubular member that is the first embodiment of the present invention. Note that in Figure 1, parts corresponding to the parts shown in the above-mentioned Figure 5 are assigned common reference numerals.

[0023] Similar to the manufacturing apparatus 100 of Figure 5, the manufacturing apparatus 100a forms an amorphous carbon vapor deposition film on the inner surface of the tubular member 1.

[0024] The tubular member 1 refers to a hollow member composed of any material, of which one end portion and the other end portion in the longitudinal direction are open ends. For example, as long as openings are present at one end and the other end in the longitudinal direction, additional openings may be provided, and the member may be a branched tube, but it is preferably a continuous integral member. The shape and size of the tubular member 1 can be specified by the inner diameter, outer diameter and length. The inner diameter and outer diameter may be constant over the longitudinal direction, or may vary, and when they vary, they may vary stepwise or continuously. In particular, the dimensions and structure of the outer surface of the tubular member 1 are not limited and may be arbitrary. Therefore, a bulky structure may be provided on the outer surface of the tubular member 1. The shape of the cross section perpendicular to the tube axis of the tubular member 1 is preferably circular or elliptical, but may also be rectangular or irregular.

[0025] The inner diameter of the tubular member 1 may be, for example, 12 mm or more and 1 m or less. In the case of a pipe with a changing inner diameter, the range of change is not particularly limited, but may be, for example, 0 to 50% of the maximum diameter. The length of the tubular member is not particularly limited, but this embodiment is advantageous in that it can be applied to long pipes of, for example, 0.5 m or more. The length of the tubular member may be the length of the pipe axis from one open end to the other open end, and can be defined similarly whether the tubular member is a straight pipe or a curved pipe. When the tubular member 1 is a member with a constant inner diameter, it is preferable that the ratio of length to inner diameter is 6 or more.

[0026] The tubular member 1 is not particularly limited and may be, for example, a tubular metal member made of a metal base material, a tubular resin member made of a resin such as an organosilicon compound (silicone resin), or a tubular inorganic member mainly containing inorganic materials such as glass or silicon. The type of metal is not particularly limited and may be iron or an iron alloy. The type of resin is also not particularly limited and any thermoplastic resin, thermosetting resin, fiber-reinforced plastic, etc. can be used. In particular, the material of the main body of the tubular member used in geothermal power generation equipment may be stainless steel, which has excellent corrosion resistance, heat resistance and wear resistance and is commonly used in piping for geothermal power generation equipment, and may include, but is not limited to, carbon steel, low-alloy steel, martensitic stainless steel, austenitic stainless steel, and ferritic stainless steel. Other examples of base materials include duplex stainless steel, precipitation-hardening stainless steel, Ni-based, Ti-based, or Co-based corrosion-resistant alloys, non-ferrous metals (Cu and Cu alloys, Al and Al alloys), polyvinyl chloride, resins such as silicone resins (including transparent resins such as transparent silicone), glass, silicon, and inorganic transparent materials such as transparent ceramics. Transparent refers to a material with a visible light transmittance of at least 80%, preferably 90% or more.

[0027] When the tubular member 1 is a component within a geothermal power generation facility, examples of tubular members may include, but are not limited to, pipes for circulating geothermal water, pipes for heat exchangers, and valves such as ball valves, gate valves, and butterfly valves.

[0028] The inner surface of the tubular member 1 may have the base material of the tubular metal member or the tubular resin member exposed, or it may have a coating such as a hard layer that does not deteriorate under plasma generation. The coating that does not deteriorate under plasma generation may be a ceramic coating or a metal coating, but is not limited to these. In this specification, a member on which an amorphous carbon vapor-deposited film is formed on the inner surface of the tubular member is called a coated tubular member. In this embodiment, the tubular member 1 is a cylindrical tube with a length of 500 mm and an inner diameter of 16 mm, but the shape and dimensions of the tubular member 1 are arbitrary.

[0029] Similar to the manufacturing apparatus 100 in Figure 5, a lid 21 with a through hole 23 is attached to the open end 11 of the tubular member 1, and a lid 22 with a through hole 24 is attached to the open end 12. The lid 21 is configured to conform to the shape of the open end 11 of the tubular member 1 and is attached in a manner that prevents gas leakage between the lid 21 and the tubular member 1. Specifically, the lid 21 can be airtightly attached to the open end 11 of the tubular member 1 via an O-ring made of silicone rubber or fluororubber. The lid 22 can be configured in a generally similar manner. The introduction section 31 is a means for introducing plasma-forming gas and raw material gas g into the tubular member 1 through the through hole 23, and may be a cylinder of plasma-forming gas and raw material gas g equipped with a flow meter and a control valve. The discharge section 32 is a means for dischargeing gas v from the inside of the tubular member 1 through the through hole 24, and consists of an exhaust pump such as a vacuum pump.

[0030] The tubular member 1 has an outer surface that functions as an electrode and is connected to the negative terminal of the power supply 4. The power supply 4 has its positive terminal grounded and outputs a constant voltage or pulsed voltage from the negative terminal to the tubular member 1.

[0031] On the other hand, in this embodiment, a through hole (not shown) is opened in the outlet section 32, and the electrode 5 is inserted through this through hole and the through hole 24 in the cover 22 and placed inside the tubular member 1. This electrode 5 is a means for generating plasma inside the tubular member 1. In this embodiment, the electrode 5 is a cylindrical electrode with a length of 800 mm and a diameter of 8 mm, but the shape and dimensions of the electrode 5 are arbitrary. The inside of the outlet section 32 into which the electrode 5 is inserted is airtight, but the electrode 5 can move inside the tubular member 1 along the tubular axis direction. Here, the tubular axis refers to the axis connecting the center of the cross-sectional shape of the tubular member 1 (or the center of the circle if the cross-sectional shape is a circle) along the longitudinal direction of the tubular member 1. The electrode 5 is also grounded. The electrode 5 protruding from the outlet section 32 is connected to the drive unit 52. This drive unit 52 is a means for moving the electrode 5 along the tubular axis direction of the tubular member 1 and is composed of a motor or the like. In this embodiment, the introduction sections 31 and 32 are grounded. On the other hand, the covers 21 and 22 are made of an insulating material such as glass. This is because if electrical conductivity occurs between the introduction sections 31 and 32 via the tubular member 1, plasma will not be generated between the tubular member 1 and the electrode 5. Therefore, to prevent this, it is necessary to insulate the tubular member 1 from the introduction sections 31 and 32 with the covers 21 and 22.

[0032] Similar to the manufacturing apparatus 100 described above, when forming a film, the inside of the tubular member 1 is depressurized. Depressurization can be achieved by letting out the gas v inside the tubular member 1 through the through hole 24 of the lid 22. In addition, a plasma-forming gas such as argon gas is introduced through the through hole 23 of the lid 21. Furthermore, the raw material gas for the carbon vapor deposition film is introduced through the through hole 23 of the lid 21. The raw material gas includes a hydrocarbon gas that serves as a carbon source to be included in the carbon vapor deposition film and optionally as a hydrogen source, and nitrogen gas that serves as a nitrogen source to be included in the carbon vapor deposition film optionally. As the hydrocarbon gas, methane, ethane, acetylene, etc. can be used. In this embodiment, the power supply 4 applies a constant voltage or pulse voltage between the tubular member 1 and the electrode 5, and the drive unit 52 moves the electrode 5 along the tubular axis direction of the tubular member 1.

[0033] According to this embodiment, as shown in Figure 1, a local plasma P is generated near the tip of the electrode 5 where electric field concentration occurs, and as the tip of the electrode 5 moves, this plasma P also moves in the direction of the tube axis. Then, within the tubular member 1, film deposition occurs at the location where the plasma P is generated, and the hydrocarbon gas is consumed in film deposition, causing a decrease in the concentration or pressure of the hydrocarbon gas. However, because the location where the plasma P is generated moves in the direction of the tube axis, the location where the concentration or pressure of the hydrocarbon gas decreases also moves in the direction of the tube axis. Therefore, when the concentration or pressure of the hydrocarbon gas within the tubular member 1 is averaged over a long period of time, it is possible to avoid changes in the concentration or pressure of the hydrocarbon gas along the direction of the tube axis and to make the carbon vapor-deposited film formed on the inner surface of the tubular member 1 uniform along the direction of the tube axis.

[0034] According to experiments conducted by the inventors of the present invention, when the flow rate of the plasma-forming gas was set to 75 sccm and the flow rate of the raw material gas to 18 sccm, and the tip of the electrode 5 was positioned at the center of the tubular member 1 in the axial direction, and a constant voltage was output from the power supply 4, plasma p was generated inside the tubular member 1. At this time, the pressure at the center in the axial direction was 69 Pa. When the average output voltage of the power supply 4 was 220 to 270 V, plasma p was generated at the center in the axial direction, and film deposition was performed by this plasma p. The duration of plasma p was 2 to 10 minutes. When plasma p stopped being generated, the voltage of the power supply 4 was increased by 5 V increments to perform film deposition. In the range of 220 V to 250 V for the output voltage of the power supply 4, plasma p was generated at the center of the tubular member 1 in the axial direction, but above 255 V, plasma p was generated from the center in the axial direction to the position of the lid 21, and above 270 V, a short circuit occurred between the electrode 5 and the lid 21, and film deposition was completed. In light of these experimental results, in order to achieve stable film deposition, it is preferable to keep the voltage applied between the tubular member 1 and the electrode 5 to an appropriate voltage value (for example, 220V to 250V) so that plasma p is generated near the tip of the electrode 5, and to move the electrode 5 so that the generation of plasma p continues.

[0035] <Second Embodiment> Figure 2 shows the configuration of a manufacturing apparatus 100b for a coated tubular member, which is a second embodiment of the present invention. In Figure 2, parts corresponding to the parts shown in Figure 1 are denoted by the same reference numerals.

[0036] In the first embodiment described above, the voltage applied between the tubular member 1 and the electrode 5 may be increased in order to increase the thickness of the carbon vapor-deposited film formed on the inner surface of the tubular member 1. However, if the applied voltage between the tubular member 1 and the electrode 5 is increased, an arc may be generated that short-circuits between the electrode 5 and the cover 21, causing the cover 21 to burn. In this case, it will interfere with the continuation of the film deposition operation.

[0037] Therefore, in this embodiment, an insulator, specifically a plastic cap 51, is placed over the tip of the electrode 5 located inside the tubular member 1. This plastic cap 51 is a cylindrical cap with a circular upper and lower bottom surface. The lower bottom surface has a cylindrical opening that just fits the tip of the electrode 5, and the upper bottom surface has a through hole 5a with a smaller diameter than this opening. The through hole 5a expels air from inside the plastic cap 51 when it is attached to the tip of the electrode 5, causing the inner surface of the plastic cap 51 to adhere tightly to the outer surface of the tip of the electrode 5. In this embodiment, by covering the electrode 5 with this plastic cap 51, the electric field concentration at the tip of the electrode 5 can be mitigated, and the generation of an arc can be suppressed. According to this embodiment, the same effects as in the first embodiment can be obtained. Furthermore, according to this embodiment, a stable film deposition operation can be continued.

[0038] <Third Embodiment> Figure 3 shows the configuration of a manufacturing apparatus 100c for a coated tubular member, which is a third embodiment of the present invention. In this embodiment, an electrode 5c having an axially extending through hole (not shown) is provided instead of the electrode 5 of the first and second embodiments. In this embodiment, an outlet section 32 is provided on the lid 21 side, and an introduction section 31 is provided on the lid 22 side. In this embodiment, the introduction section 31 introduces plasma forming gas and raw material gas g into the tubular member 1 through the through hole of the electrode 5c.

[0039] According to this embodiment, by having gas present only around the tip of the electrode 5c, the plasma generation range is limited, and unintended widespread plasma generation and arc generation within the tubular member 1 can be prevented.

[0040] <Fourth Embodiment> Figure 4 shows the configuration of a manufacturing apparatus 100d for a coated tubular member, which is a fourth embodiment of the present invention. In this embodiment as well, the same electrode 5c as in the third embodiment is used. However, in this embodiment, a lid 21a without a through hole is provided instead of the lid 21 of the first embodiment. In addition, an introduction section 31 and an outlet section 32 are provided on the lid 22 side. In this embodiment, the introduction section 31 introduces plasma forming gas and raw material gas g into the tubular member 1 through the through hole of the electrode 5c. The gas inside the tubular member 1 is discharged by the outlet section 32 through the through hole 24 of the lid 22. The same effects as in the third embodiment can be obtained in this embodiment as well.

[0041] <Other Embodiments> The first to fourth embodiments of this invention have been described above, but other embodiments of this invention are possible. For example, the following:

[0042] (1) In each of the above embodiments, the tubular member 1 was a straight pipe along its entire length in the longitudinal direction, as shown in Figures 1 and 2. However, the tubular member 1 may be a pipe with a changing diameter or a curved pipe.

[0043] (2) One or more transparent windows may be provided in the wall of the tubular member 1, and the generation status of plasma p inside the tubular member 1 may be monitored by a camera or the like through these windows, and the operation of the manufacturing apparatus 100a or 100b may be controlled based on the monitoring results. For example, if there is an excess of plasma p in order to perform an appropriate film deposition operation, the voltage applied from the power supply 4 may be reduced.

[0044] (3) In each of the above embodiments, the electrode 5 was inserted into the tubular member 1 from the cover 22, but it may also be inserted into the tubular member 1 from the cover 21.

[0045] (4) In each of the above embodiments, the electrode 5 was moved by the drive unit 52, but it may also be moved manually.

[0046] (5) There are four ways to apply the potential difference between the tubular member 1 (the object to be film-deposited) and the electrode 5 or 5c, depending on which one is grounded and whether the tubular member 1 is at a negative or positive potential relative to the electrode 5 or 5c. a. Electrode 5 or 5c is grounded, and a negative potential is applied to the tubular member 1. b. Electrode 5 or 5c is grounded, and a positive potential is applied to the tubular member 1. c. Ground the tubular member 1 and apply a negative potential to electrode 5 or 5c. d. Ground the tubular member 1 and apply a positive potential to electrode 5 or 5c. In the above embodiments, embodiment a was implemented, but embodiments b, c, and d may also be implemented. [Explanation of symbols]

[0047] 100a, 100b, 100c, 100d... Manufacturing equipment, 1... Tubular member, 11, 12... Open end, 21, 22, 21d... Cover, 23, 24, 51a... Through hole, 31... Inlet, 32... Outlet, 4... Power supply, 5, 5c... Electrode, 51... Plastic cap, 52... Drive unit.

Claims

1. An electrode that can move along the axial direction of the tube is placed inside a hollow tubular member. While guiding the gas out from inside the tubular member, the raw material gas for the amorphous carbon vapor deposition film and the plasma forming gas are introduced into the tubular member. A voltage is applied between the tubular member and the electrode to generate plasma near the tip of the electrode inside the tubular member, while moving the electrode in the axial direction of the tube. A method for manufacturing a coated tubular member, wherein an amorphous carbon vapor-deposited film is formed on the inner surface of the tubular member.

2. The electrode has an insulating material covering the tip located inside the tubular member. The manufacturing method according to claim 1.

3. Two lids, each with a through hole, are attached to the open ends on both sides of the tubular member in the axial direction. Gas is discharged through the through hole in one of the two lids, and gas is introduced through the through hole in the other lid. The manufacturing method according to claim 2.

4. The electrode has a through hole extending in the axial direction, Gas is introduced into the tubular member through the through-hole of the electrode. The manufacturing method according to claim 1.

5. An outlet section for releasing gas from inside a hollow tubular member, The tubular member includes an introduction section for introducing a raw material gas for an amorphous carbon vapor deposition film and a plasma forming gas, An axial electrode, which is disposed within the tubular member and movable along the axial direction of the tube, A power supply that applies a voltage between the tubular member and the electrode to generate plasma near the tip of the electrode inside the tubular member, Having, A manufacturing apparatus for coated tubular members, in which an amorphous carbon vapor-deposited film is formed on the inner surface of the tubular member.

6. It has two lids, each with a through hole, which are attached to the open ends on both sides of the tubular member in the axial direction. The discharge section discharges the gas from inside the tubular member through a through-hole in one of the two covers. The introduction section introduces gas into the tubular member through the through-hole of the other of the two covers. The manufacturing apparatus according to claim 5.

7. The electrode has an insulating material covering the tip located inside the tubular member. The manufacturing apparatus according to claim 6.

8. The electrode has a through hole extending in the axial direction, The introduction section introduces gas into the tubular member through the through-hole of the electrode. The manufacturing apparatus according to claim 5.

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