WO2020067227A1 - 金属管の洗浄方法及び洗浄装置 - Google Patents
金属管の洗浄方法及び洗浄装置 Download PDFInfo
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- WO2020067227A1 WO2020067227A1 PCT/JP2019/037730 JP2019037730W WO2020067227A1 WO 2020067227 A1 WO2020067227 A1 WO 2020067227A1 JP 2019037730 W JP2019037730 W JP 2019037730W WO 2020067227 A1 WO2020067227 A1 WO 2020067227A1
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- cleaning
- cleaning liquid
- liquid
- cleaning tank
- tank
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
- B08B3/04—Cleaning involving contact with liquid
- B08B3/10—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration
- B08B3/12—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration by sonic or ultrasonic vibrations
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B9/00—Cleaning hollow articles by methods or apparatus specially adapted thereto
- B08B9/02—Cleaning pipes or tubes or systems of pipes or tubes
- B08B9/023—Cleaning the external surface
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
- B08B3/04—Cleaning involving contact with liquid
- B08B3/10—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration
- B08B3/102—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration with means for agitating the liquid
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B7/00—Cleaning by methods not provided for in a single other subclass or a single group in this subclass
- B08B7/02—Cleaning by methods not provided for in a single other subclass or a single group in this subclass by distortion, beating, or vibration of the surface to be cleaned
- B08B7/026—Using sound waves
- B08B7/028—Using ultrasounds
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B9/00—Cleaning hollow articles by methods or apparatus specially adapted thereto
- B08B9/02—Cleaning pipes or tubes or systems of pipes or tubes
- B08B9/027—Cleaning the internal surfaces; Removal of blockages
- B08B9/032—Cleaning the internal surfaces; Removal of blockages by the mechanical action of a moving fluid, e.g. by flushing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B2209/00—Details of machines or methods for cleaning hollow articles
- B08B2209/005—Use of ultrasonics or cavitation, e.g. as primary or secondary action
Definitions
- the present disclosure relates to a method and an apparatus for cleaning a metal tube.
- an acid washing treatment has been performed to remove scale generated on the surface of the metal tube.
- the metal tube after the pickling treatment is washed with a washing liquid in order to remove scale remaining on the surface (for example, a water washing treatment (rinsing) with water is performed).
- the metal tube after the pickling treatment can be subjected to, for example, ultrasonic cleaning in which cleaning is performed while irradiating the cleaning liquid with ultrasonic waves.
- Patent Document 1 discloses an ultrasonic cleaning apparatus that performs ultrasonic cleaning of an object to be cleaned in the presence of microbubbles.
- the ultrasonic cleaning device includes an ultrasonic generator and a deaerator.
- the ultrasonic generator is provided in a cleaning tank in which a cleaning liquid is stored.
- the deaerator is provided in a circulation path connected to the cleaning tank.
- the cleaning liquid in the cleaning tank is introduced into the deaerator through the circulation path.
- the deaerator separates dissolved air from the cleaning liquid to generate air bubbles, preferably microbubbles. These bubbles (microbubbles) are returned to the cleaning tank via the circulation path together with the cleaning liquid. Thereby, the dissolved air concentration of the cleaning liquid in the cleaning tank gradually decreases.
- the ultrasonic generator irradiates the cleaning liquid with ultrasonic waves.
- Patent Document 1 describes that by setting the dissolved air concentration of the cleaning liquid to a specified value or less, efficient and good ultrasonic cleaning can be performed without lowering the sound pressure of ultrasonic waves.
- the ultrasonic cleaning device of Patent Literature 1 is used for cleaning a metal tube after an acid cleaning process, there is a concern that the cleaning performance may be reduced. That is, in the ultrasonic cleaning of the metal tube, the amount of scale in the cleaning liquid increases with time. This scale attenuates the ultrasonic waves applied to the cleaning liquid and reduces the cleaning performance.
- a method for cleaning a metal tube includes a storage step of storing a cleaning liquid in a cleaning tank, a process for forming fine bubbles by bubbling dissolved gas in the cleaning liquid in the cleaning tank, and an ultra-fine bubble in the cleaning liquid in the cleaning tank.
- a discharging step of discharging an amount of the cleaning liquid corresponding to the height exceeding the reference liquid level from the cleaning tank when the height exceeds the reference liquid level.
- high cleaning performance can be maintained for a long time in cleaning a metal tube.
- FIG. 1 is a plan view of the cleaning device according to the embodiment.
- FIG. 2 is a sectional view taken along line II-II of the cleaning apparatus shown in FIG.
- FIG. 3 is a diagram illustrating a discharge mechanism that can be employed in the cleaning device according to the embodiment.
- FIG. 4 is a diagram illustrating another discharge mechanism that can be employed in the cleaning device according to the embodiment.
- FIG. 5 is a graph showing the relationship between the dissolved oxygen concentration of the cleaning liquid, the sound pressure of the ultrasonic wave, and the cleaning properties of the metal tube.
- FIG. 6 is a graph showing the relationship between the overflow time of the cleaning liquid, the dissolved oxygen concentration of the cleaning liquid, and the supply amount of the cleaning liquid to the cleaning tank.
- FIG. 1 is a plan view of the cleaning device according to the embodiment.
- FIG. 2 is a sectional view taken along line II-II of the cleaning apparatus shown in FIG.
- FIG. 3 is a diagram illustrating a discharge mechanism that can be employed in the cleaning device according
- FIG. 7 is a graph showing a relationship between the scale density of the cleaning liquid, the sound pressure attenuation rate of the ultrasonic wave, and the cleanability of the metal tube.
- FIG. 8 is a graph showing the relationship between the surface area of the metal tube subjected to the cleaning process, the scale density of the cleaning solution, and the supply amount of the cleaning solution to the cleaning tank.
- the method for cleaning a metal tube includes a storing step of storing the cleaning liquid in the cleaning tank, a process of forming dissolved gas in the cleaning liquid in the cleaning tank into bubbles to generate fine bubbles, and an ultra-fine bubble in the cleaning liquid in the cleaning tank.
- the cleaning method according to the first configuration by generating fine bubbles in the cleaning liquid in which the metal tube is immersed, the ultrasonic waves radiated into the cleaning liquid are scattered to improve the cleaning property. Also, by dissolving the dissolved gas in the cleaning liquid into bubbles to generate fine bubbles, the concentration of dissolved oxygen in the cleaning liquid decreases during ultrasonic cleaning. Thereby, good ultrasonic cleaning properties can be ensured.
- the cleaning liquid is supplied to the cleaning tank, or the metal pipe is immersed in the cleaning liquid in the cleaning tank, so that the liquid level of the cleaning liquid in the cleaning tank is increased.
- the cleaning liquid rises above the reference liquid level, the cleaning liquid is discharged from the cleaning tank by the height exceeding the reference liquid level.
- the scale that peels off from the metal tube and disperses and floats in the cleaning liquid is discharged from the cleaning tank together with the cleaning liquid.
- a new cleaning liquid is also supplied. Therefore, the scale density in the cleaning liquid can be reduced in the cleaning tank. Therefore, attenuation of the ultrasonic wave irradiated into the cleaning liquid can be reduced, and high cleaning performance can be maintained for a long period of time.
- the concentration of dissolved oxygen in the cleaning solution in the cleaning tank is preferably 5.2 mg / L or less (second configuration).
- the supply step can be performed simultaneously with the immersion step.
- the supply amount of the cleaning liquid to the cleaning tank per minute is preferably 0.17% or more and 1.25% or less of the stored amount of the cleaning liquid in the cleaning tank (third configuration).
- the increase in the amount of scale in the cleaning liquid can be more reliably suppressed, and the concentration of dissolved oxygen in the cleaning liquid can be maintained in a preferable range.
- the supply amount is more preferably 0.17% or more and 0.83% or less of the storage amount (fourth configuration), and is 0.33% or more and 0.83% or less of the storage amount. More preferable (fifth configuration).
- an increase in the amount of scale in the cleaning liquid can be more reliably suppressed, and the dissolved oxygen concentration in the cleaning liquid can be maintained in a more preferable range.
- the metal pipe may be a steel pipe having a specific chemical composition.
- the chemical composition is, in mass%, C: 0.01 to 0.13%, Si: 0.75% or less, Mn: 2% or less, P: 0.045% or less, S: 0.030% or less, It is preferable that Ni: 7 to 14% and Cr: 16 to 20% are contained, with the balance being Fe and impurities (sixth configuration).
- the chemical composition is such that Nb: 0.2 to 1.1%, Ti: 0.1 to 0.6%, Mo: 0.1 to 3%, by mass%, instead of a part of the remaining Fe.
- the above chemical composition may also contain B: 0.001 to 0.1% and N: 0.02 to 0.12% by mass% in place of a part of the remaining Fe (the eighth embodiment). Constitution).
- the metal pipe cleaning apparatus includes a cleaning tank, a supply mechanism, a discharge mechanism, a fine bubble generation mechanism, and an ultrasonic irradiation mechanism.
- the cleaning liquid is stored in the cleaning tank, and a metal tube is accommodated therein.
- the supply mechanism supplies the cleaning liquid to the cleaning tank.
- the discharge mechanism discharges an amount of the cleaning liquid corresponding to the height exceeding the reference liquid level from the cleaning tank.
- the fine bubble generating mechanism generates fine bubbles by bubbling dissolved gas in the cleaning liquid in the cleaning tank.
- the ultrasonic irradiation mechanism irradiates the cleaning liquid in the cleaning tank with ultrasonic waves (ninth configuration).
- the cleaning device includes a fine bubble generation mechanism.
- the fine bubble generation mechanism generates fine bubbles in the cleaning liquid by bubbling dissolved gas in the cleaning liquid. For this reason, in the ultrasonic cleaning of the metal tube, good cleaning properties can be ensured.
- the discharge mechanism when the liquid level of the cleaning liquid in the cleaning tank exceeds the reference liquid level, the discharge mechanism performs cleaning by an amount corresponding to the height exceeding the reference liquid level. Drain the cleaning liquid from the tank. As a result, the scale that peels off from the metal tube and disperses and floats in the cleaning liquid is discharged from the cleaning tank together with the cleaning liquid.
- the supply mechanism supplies a new cleaning liquid to the cleaning tank. In the cleaning tank, the scale density in the cleaning liquid can be reduced by supplying and discharging the cleaning liquid. For this reason, attenuation of the ultrasonic waves can be reduced, and high cleaning properties can be ensured.
- FIG. 1 is a plan view schematically showing a cleaning device 1 according to the embodiment.
- FIG. 2 is a sectional view taken along the line II-II of the cleaning apparatus 1 shown in FIG.
- cleaning device 1 performs ultrasonic cleaning on metal tube 2 as an object to be cleaned.
- the cleaning device 1 can perform, for example, a water washing process on the metal tube 2 after the acid cleaning process.
- the cleaning apparatus 1 includes the cleaning tank 10, the supply mechanism 20, a plurality of discharge mechanisms 30, a plurality of ultrasonic irradiation mechanisms 40, and a plurality of fine bubble generation mechanisms 50.
- the cleaning device 1 further includes a plurality of buffer members 60.
- the cleaning tank 10 is configured to accommodate the metal tube 2.
- a plurality of metal tubes 2 are usually accommodated in the cleaning tank 10 at the same time.
- the cleaning tank 10 stores the cleaning liquid 3 for cleaning the metal pipe 2.
- the type of the cleaning liquid 3 is not particularly limited, and may be appropriately selected from known cleaning liquids.
- the cleaning liquid 3 is, for example, water (tap water or industrial water).
- the cleaning tank 10 has a rectangular shape in plan view.
- the cleaning tank 10 has an open upper surface.
- the bottom surface of the cleaning tank 10 is, for example, an inclined surface inclined from one end in the longitudinal direction toward the other end. That is, in the cleaning tank 10, the depth of one end in the longitudinal direction (the height of the inner wall surface) is different from the depth of the other end in the longitudinal direction (the height of the inner wall surface).
- the cleaning tank 10 is, for example, a large cleaning tank having a length of about 10 to 25 m, a width of about 1 to 2 m, and a maximum depth of about 0.4 to 1 m.
- the material of the cleaning tank 10 is not particularly limited.
- Examples of the material of the cleaning tank 10 include metal materials such as stainless steel, plastic resins such as fiber reinforced plastic (FRP) and polypropylene (PP), and acid-resistant bricks.
- the supply mechanism 20 supplies the cleaning liquid 3 to the cleaning tank 10.
- the supply mechanism 20 has at least one supply pipe 21.
- the supply mechanism 20 has a plurality of supply pipes 21.
- the cleaning liquid 3 is supplied to the cleaning tank 10 through each supply pipe 21.
- the plurality of supply pipes 21 are arranged at intervals. For this reason, the cleaning liquid 3 is dispersed and supplied to the cleaning tank 10.
- the supply pipes 21 are provided along one of the pair of longitudinal side walls of the cleaning tank 10.
- the position and the number of the supply pipes 21 are not particularly limited.
- One or more supply pipes 21 may be provided on both side walls in the longitudinal direction of the cleaning tank 10. Further, one or more supply pipes 21 may be provided on the short side wall of the cleaning tank 10 in addition to or instead of the long side wall of the cleaning tank 10.
- Each discharge mechanism 30 discharges the cleaning liquid 3 from the cleaning tank 10 when the amount of the cleaning liquid 3 in the cleaning tank 10 exceeds a predetermined amount.
- the plurality of discharge mechanisms 30 are arranged at intervals. Therefore, the cleaning liquid 3 is dispersed and discharged from the cleaning tank 10.
- the discharge mechanism 30 may be one.
- the plurality of discharge mechanisms 30 are provided along a side wall of the cleaning tank 10 opposite to the supply pipe 21 in the pair of side walls in the longitudinal direction.
- the position and number of the discharge mechanism 30 are not particularly limited.
- the discharge mechanism 30 may be provided on the side wall on the supply pipe 21 side of the pair of side walls in the longitudinal direction of the cleaning tank 10. Further, one or more discharge mechanisms 30 may be provided on the short side wall of the cleaning tank 10 in addition to or instead of the long side wall of the cleaning tank 10.
- FIG. 3 illustrates a discharge mechanism 30A that can be used in the cleaning device 1.
- the discharge mechanism 30A includes a discharge port 31 and a discharge pipe 32.
- the discharge port 31 is an opening formed on the side wall of the cleaning tank 10.
- the discharge pipe 32 is provided outside the cleaning tank 10 and is connected to the discharge port 31.
- the cleaning liquid 3 is discharged from the cleaning tank 10 through a discharge port 31 and a discharge pipe 32.
- the reference liquid level S of the cleaning liquid 3 in the cleaning tank 10 is set.
- the cleaning liquid 3 is supplied to the cleaning tank 10 until the liquid level reaches the reference liquid level S.
- the position of the lower end of the outlet 31 substantially coincides with the position of the reference liquid level S.
- the discharge mechanism 30A discharges the cleaning liquid 3 from the cleaning tank 10 when the amount of the cleaning liquid 3 in the cleaning tank 10 exceeds the liquid amount (predetermined amount) corresponding to the reference liquid level S.
- FIG. 4 illustrates another discharge mechanism 30 ⁇ / b> B that can be used in the cleaning device 1.
- the discharge mechanism 30B includes a discharge port 33, a discharge pipe 34, a discharge pump 35, and a liquid level detection unit (not shown).
- a liquid level detecting means a commercially available liquid level sensor or the like can be used.
- the discharge port 33 is an opening formed on the side wall of the cleaning tank 10.
- the discharge port 33 is provided at an arbitrary height lower than the reference liquid level S on the side wall of the cleaning tank 10.
- the discharge pipe 34 is provided outside the cleaning tank 10 and is connected to the discharge port 33.
- the cleaning liquid 3 is discharged from the cleaning tank 10 through the discharge port 33 and the discharge pipe 34.
- the discharge pump 35 is provided in the middle of the discharge pipe 34.
- the discharge pump 35 sucks the cleaning liquid 3 exceeding the reference liquid level S from the cleaning tank 10. Controlled. For example, when the liquid level of the cleaning liquid 3 exceeds the reference liquid level S, the discharge pump 35 is driven according to a signal from the liquid level detecting means arranged in the cleaning tank 10, and the level of the cleaning liquid 3 is raised. When the pressure falls below the height of the reference liquid level S, the control of the discharge pump 35 is stopped.
- the discharge mechanism 30B similarly to the discharge mechanism 30A (FIG. 3), the discharge mechanism 30B also discharges the cleaning liquid 3 from the cleaning tank 10 when the amount of the cleaning liquid 3 in the cleaning tank 10 exceeds a predetermined amount.
- the ultrasonic irradiation mechanism 40 irradiates the cleaning liquid 3 in the cleaning tank 10 with ultrasonic waves.
- the ultrasonic irradiation mechanism 40 a known ultrasonic transducer generally used in ultrasonic cleaning can be used.
- the frequency of the ultrasonic waves emitted by the ultrasonic irradiation mechanism 40 is preferably 20 kHz to 200 kHz.
- the frequency of the ultrasonic wave is more preferably from 20 kHz to 150 kHz, and still more preferably from 25 kHz to 100 kHz.
- the ultrasonic irradiation mechanism 40 preferably has a frequency sweep function.
- the frequency sweeping function is a function of irradiating the cleaning liquid 3 with ultrasonic waves while sweeping the frequency in a range of ⁇ 0.1 kHz to ⁇ 10 kHz around a selected specific frequency.
- At least one ultrasonic irradiation mechanism 40 is provided on the inner surface of each side wall of the cleaning tank 10.
- the position and number of the ultrasonic irradiation mechanism 40 are not particularly limited.
- One or more ultrasonic irradiation mechanisms 40 may be provided on the bottom surface of the cleaning tank 10.
- the ultrasonic irradiation mechanisms 40 When a plurality of ultrasonic irradiation mechanisms 40 are installed in the cleaning tank 10, it is preferable to arrange the ultrasonic irradiation mechanisms 40 such that ultrasonic waves are uniformly transmitted to the entire cleaning tank 10. Thereby, the oscillating load of each ultrasonic irradiation mechanism 40 becomes uniform, so that interference between the generated ultrasonic waves can be prevented.
- the fine bubble generating mechanism 50 generates fine bubbles by bubbling dissolved gas in the cleaning liquid 3 in the cleaning tank 10.
- the fine bubble generating mechanism 50 is arranged outside the cleaning tank 10.
- a plurality of fine bubble generating mechanisms 50 are arranged along one longitudinal side wall of the cleaning tank 10.
- the position and number of the fine bubble generating mechanism 50 are not particularly limited.
- Each fine bubble generating mechanism 50 has piping 51 and 52 and a fine bubble generating device 53.
- the pipes 51 and 52 connect the cleaning tank 10 and the fine bubble generator 53.
- the cleaning liquid from the cleaning tank 10 is introduced into the fine bubble generator 53 via the pipe 51.
- the fine bubble generator 53 generates fine bubbles by using dissolved gas in the cleaning liquid 3.
- the fine bubbles are returned to the cleaning tank 10 via the pipe 52 together with the cleaning liquid 3.
- the fine bubble generator 53 can be appropriately selected from known fine bubble generators.
- a known fine bubble generator for example, fine bubbles are generated by shearing bubbles, passing bubbles through micropores, depressurizing liquid (pressure change), dissolving gas under pressure, ultrasonic waves, electrolysis, or chemical reaction. What causes them to be known.
- the fine bubble generating device 53 is one that can easily control the bubble diameter and concentration of the fine bubbles.
- a known fine bubble generating device that generates fine bubbles by causing a pressure change of a liquid in a liquid circulation path can be employed.
- the fine bubbles are fine bubbles having an average bubble diameter of 100 ⁇ m or less.
- fine bubbles having an average cell diameter of ⁇ m are sometimes referred to as microbubbles
- fine bubbles having an average cell diameter of nm are sometimes referred to as nanobubbles.
- the average bubble diameter is the diameter at which the number of samples is the largest in the number distribution related to the diameter of the fine bubbles.
- Fine bubbles improve the propagation efficiency of ultrasonic waves to an object to be cleaned in ultrasonic cleaning, and improve the cleanability as a core of ultrasonic cavitation.
- the fine bubbles are often negatively charged at the surface potential.
- the object to be cleaned for example, scale, smut, or oil
- the fine bubbles are adsorbed to the metal tube 2 due to a difference in charging property.
- the average bubble diameter of the fine bubbles in the cleaning liquid 3 is preferably 0.01 ⁇ m or more from the viewpoint of preventing the fine bubble generation mechanism 50 from being enlarged and facilitating the control of the bubble diameter.
- the average bubble diameter of the fine bubbles is preferably 100 ⁇ m or less from the viewpoint of increasing the floating speed of the fine bubbles and preventing the propagation of the ultrasonic wave to the metal tube 2. More preferably, the fine bubbles are microbubbles having an average bubble diameter of 1 ⁇ m to 50 ⁇ m.
- the fine bubble generation mechanism 50 preferably generates fine bubbles in the cleaning liquid 3 such that the number of fine bubbles having a bubble diameter equal to or less than the frequency resonance diameter is 70% or more of the total number of fine bubbles.
- Minnaert resonance frequencies The natural frequencies of various bubbles including fine bubbles are also referred to as Minnaert resonance frequencies and are given by the following equation (1).
- f 0 natural frequency of bubble (Minnaert resonance frequency)
- R 0 average radius of bubble
- p ⁇ average pressure of surrounding liquid
- ⁇ liquid density
- the value of 0 R 0 is about 3 kHz ⁇ mm.
- the radius (resonance radius) R0 of the resonating bubble is about 150 ⁇ m.
- the resonance radius R 0 is about 30 ⁇ m, and the frequency resonance diameter 2R 0 is about 60 ⁇ m.
- Bubbles having a radius larger than the resonance radius R 0 are inhibitors. This is because when bubbles including fine bubbles resonate, the bubbles repeat expansion and contraction in a short time and eventually collapse, but when the first sound wave passes through the bubbles, the size of the bubbles becomes frequency resonance. larger than the diameter 2R 0, ultrasound is because diffuses bubbles surface. Conversely, if the frequency resonant diameter 2R 0 or less the size of the bubbles at the time the first acoustic wave passes through the bubble, ultrasound can pass through the bubble without diffusing bubbles surface.
- a number of fine bubbles having a bubble size of less frequency resonant diameter 2R 0 it is preferable that a percentage of the total number of fine bubbles is 70% or more.
- the above ratio is more preferably 80% or more and 98% or less.
- the concentration (density) of the fine bubbles in the cleaning liquid 3 is preferably 10 3 / mL or more from the viewpoint of improving the propagation of ultrasonic waves and securing the number of ultrasonic cavitation nuclei.
- the concentration of fine bubbles to be generated in the cleaning liquid 3, in order to prevent the size and number increase of the fine-bubble generating mechanism 50 is preferably 10 6 cells / mL or less.
- the average bubble diameter and concentration of fine bubbles can be measured by a known device such as a liquid particle counter or a bubble diameter distribution measuring device.
- the buffer member 60 is arranged in the cleaning tank 10.
- the plurality of buffer members 60 are arranged in the longitudinal direction of the cleaning tank 10.
- the cushioning member 60 has a substantially U-shape.
- the metal pipe 2 in the cleaning tank 10 is placed on the buffer member 60.
- the inner surface of the buffer member 60 is located inside the ultrasonic irradiation mechanism 40 in the cleaning tank 10. For this reason, the metal tube 2 does not come into contact with the ultrasonic irradiation mechanism 40, and the ultrasonic irradiation mechanism 40 is protected from the metal tube 2.
- the scale is generated on the surface of the metal tube 2 through hot working or heat treatment.
- the metal tube 2 is subjected to an acid washing treatment.
- the cleaning method according to the present embodiment is a method of cleaning the metal tube 2 after a step of immersing the metal tube 2 in an acid solution for a predetermined time to perform pickling (a known pickling step).
- the metal tube 2 as the object to be cleaned is, for example, a tube made of stainless steel or a tube made of a Ni-based alloy.
- the metal tube 2 is a stainless steel tube
- the metal tube 2 is a steel tube containing 10.5% or more of Cr by mass%.
- C 0.01 to 0.13%
- Si 0.0.75% or less
- Mn 2% or less
- P 0.045% or less
- S 0.030% or less
- Ni: 7 This is a steel pipe containing up to 14% and Cr: 16 to 20%, the balance being Fe and impurities.
- the chemical composition is such that Nb: 0.2 to 1.1%, Ti: 0.1 to 0.6%, Mo: 0.1 to 3%, Cu: 2.5 to 3.5%, any one or more of them may be contained. Further, instead of part of the remaining Fe, B may contain 0.001 to 0.1% by mass and N may contain 0.02 to 0.12% by mass%.
- the metal tube 2 having the above chemical composition has excellent heat resistance, corrosion resistance, and steam oxidation resistance because its steel structure is austenite.
- the metal tube 2 has an excellent tensile strength of, for example, 550 MPa or more. Since such a metal tube 2 is subjected to a heat treatment at a high temperature exceeding 1000 ° C. in the manufacturing process, a large amount of scale is generated on the surface. Therefore, a pickling treatment after the heat treatment and a washing treatment (rinsing treatment) for washing away the scale remaining on the surface after the pickling treatment are required.
- the metal tube 2 is a Ni-based alloy tube, for example, it has the following chemical composition. In mass%, C: 0.05% or less, Si: 0.5% or less, Mn: 1% or less, P: 0.030% or less, S: 0.030% or less, Cr: 19.5 to 24. 0%, Mo: 2.5 to 4.0%, Ti: 1.2% or less, and Fe: 22% or more, and the main balance is Ni (typically, the balance is Ni and impurities Is).
- the chemical composition contains one or more of Cu: 0.5% or less, Nb: 4.5% or less, and Al: 2.0% or less by mass% instead of a part of the remaining Ni. Is also good.
- the method for cleaning the metal pipe 2 includes a step of storing the cleaning liquid 3 in the cleaning tank 10, a step of immersing the metal pipe 2 in the cleaning liquid 3 in the cleaning tank 10, and a step of supplying the cleaning liquid 3 to the cleaning tank 10. And a step of discharging the cleaning liquid 3 from the cleaning tank 10.
- the cleaning liquid 3 is stored in the cleaning tank 10.
- the cleaning liquid 3 is supplied to the cleaning tank 10 by a supply mechanism 20.
- the cleaning liquid 3 may be supplied to the cleaning tank 10 by means other than the supply mechanism 20.
- the cleaning liquid 3 supplied to the cleaning tank 10 preferably has a dissolved oxygen concentration of about 7 mg / L to 11 mg / L, and has a dissolved oxygen concentration of about 8 mg / L to 10 mg / L. Is more preferred.
- the cleaning liquid 3 is typically water (tap water or industrial water).
- the dissolved oxygen concentration of the cleaning liquid 3 is 7 mg / L to 11 mg / L.
- the cleaning liquid 3 is water having a water temperature of 15 to 25 ° C. (tap water or industrial water)
- the dissolved oxygen concentration of the cleaning liquid 3 is 8 mg / L to 10 mg / L.
- the dissolved oxygen concentration is an index of the amount of dissolved gas in the cleaning liquid 3.
- the metal tube 2 is immersed in the cleaning liquid 3 stored in the cleaning tank 10 for a predetermined time.
- the metal pipe 2 can be immersed in the cleaning liquid 3 in the cleaning tank 10 using a crane or the like.
- a plurality of metal tubes 2 are immersed in the cleaning liquid 3 simultaneously, but the metal tubes 2 may be immersed one by one in the cleaning liquid 3.
- this cycle is defined as immersing the metal tube 2 in the cleaning solution 3 in the cleaning tank 10, holding the metal tube 2 in the cleaning solution 3, and lifting the metal tube 2 from the cleaning tank 10 as one cycle. Perform a predetermined number of times.
- the holding time of the metal tube 2 in the cycle and the number of times the cycle is performed can be determined so that the total immersion time of the metal tube 2 in the cleaning liquid 3 is equal to or longer than a predetermined time.
- the total immersion time of the metal tube 2 may be appropriately set according to the amount of scale attached to the metal tube 2 and the like.
- the total immersion time of the metal tube 2 is, for example, preferably 30 seconds or more, and more preferably 1 minute or more.
- a new cleaning liquid 3 is continuously supplied to the cleaning tank 10 by the supply mechanism 20.
- the discharge mechanism 30 continuously discharges the cleaning liquid 3 in an amount corresponding to the height exceeding the reference liquid level S from the cleaning tank 10. That is, in this embodiment, the immersion step, the supply step, and the discharge step are performed simultaneously.
- the supply mechanism 20 stores the cleaning liquid 3 in the cleaning tank 10 per minute (when the cleaning liquid 3 is stored up to the reference liquid level S in the cleaning tank 10 in a state where the metal pipe 2 is not immersed).
- the washing liquid preferably 0.17% or more and 1.25% or less, more preferably 0.17% or more and 0.83% or less, and still more preferably 0.33% or more and 0.83% or less. 3 is supplied to the cleaning tank 10.
- the cleaning liquid 3 in the cleaning tank 10 is irradiated with ultrasonic waves by the ultrasonic irradiation mechanism 40, and fine bubbles are supplied by the fine bubble generation mechanism 50.
- the dissolved gas concentration in the cleaning liquid 3 is reduced by the fine bubble generation mechanism 50 forming the dissolved gas in the cleaning liquid 3 into bubbles.
- the fine bubble generation mechanism 50 lowers the dissolved oxygen concentration of the cleaning liquid 3 in the cleaning tank 10 to 5.2 mg / L or less.
- the fine bubble generation mechanism 50 lowers the dissolved oxygen concentration of the cleaning liquid 3 in the cleaning tank 10 to preferably 4.5 mg / L or less, more preferably 4.2 mg / L or less.
- the supply mechanism 20 supplies the cleaning tank 3 with the cleaning liquid 3 having a dissolved oxygen concentration of about 7 mg / L to 11 mg / L, preferably about 8 mg / L to 10 mg / L.
- the cleaning liquid 3 passes through the fine bubble generator 53 of the fine bubble generation mechanism 50, the dissolved gas in the cleaning liquid 3 is turned into fine bubbles, and the dissolved oxygen concentration of the cleaning liquid 3 decreases.
- the dissolved oxygen concentration of the cleaning liquid 3 in the cleaning tank 10 is 5.2 mg / L or less, more preferably 4.5 mg / L or less. , And more preferably 4.2 mg / L or less.
- the concentration of dissolved oxygen in the cleaning liquid 3 in the cleaning tank 10 may increase.
- the dissolved oxygen concentration of the cleaning liquid 3 becomes high, it is preferable to stop the ultrasonic cleaning of the metal tube 2 until the fine bubble generation mechanism 50 sufficiently reduces the dissolved oxygen concentration.
- the immersion of the metal tube 2 may be restarted when the dissolved oxygen concentration of the cleaning liquid becomes 5.2 mg / L or less, 4.5 mg / L or less, or 4.2 mg / L or less.
- the metal pipe 2 is disposed in the cleaning tank 10 in the immersion step.
- the cleaning liquid 3 can be stored in the cleaning tank 10 after the metal pipe 2 is disposed in the empty cleaning tank 10.
- the metal tube 2 as the object to be cleaned is an austenitic stainless steel tube (Ni: 9% by mass, Cr: 18.5% by mass, Cu: 3% by mass, Nb: 0.5% by mass)
- the cleaning liquid 3 supplied to the cleaning tank 10 is water (industrial water) having a water temperature of about 20 ° C.
- the amount of the cleaning liquid 3 stored in the cleaning tank 10 is about 12000 L.
- FIG. 5 is a graph showing the relationship between the dissolved oxygen concentration of the cleaning liquid 3, the sound pressure of the ultrasonic wave applied to the cleaning liquid 3, and the cleanability of the metal tube 2.
- the cleaning property of the metal tube 2 is improved by changing the dissolved oxygen concentration of the cleaning liquid 3 in the cleaning tank 10 and the sound pressure of the ultrasonic wave applied to the cleaning liquid 3 in the cleaning tank 10. Verified.
- the dissolved oxygen concentration [mg / L] is a value measured by a commercially available dissolved oxygen concentration meter (LAQUA @ OM-71, manufactured by Horiba, Ltd.). This measured value is defined as the dissolved oxygen concentration in the present disclosure.
- the sound pressure [mV] is measured in a measurement mode in which an average measurement value for 5 seconds is measured using a commercially available ultrasonic sound pressure meter (sound pressure monitor # 19001D manufactured by Kaijo Co., Ltd.). Of the cleaning liquid 3 from the liquid surface of the cleaning liquid 3 in 100 mm water. This measured value is used as the sound pressure in the present disclosure.
- the frequency of the ultrasonic wave is 38 kHz.
- ⁇ means that the scale was completely removed from the surface of the metal tube 2 and the cleaning property by the ultrasonic wave was extremely good.
- ⁇ means that although the scale remains on a part of the surface of the metal tube 2, it can be said that the cleaning property by the ultrasonic wave is good.
- X means that the cleaning property by the ultrasonic wave was poor.
- the dissolved oxygen concentration of the cleaning liquid 3 in the cleaning tank 10 is set to 5.2 mg / L or less.
- the dissolved oxygen concentration of the cleaning liquid 3 in the cleaning tank 10 is preferably 4.5 mg / L or less, and more preferably 4.2 mg / L or less.
- the ultrasonic irradiation mechanism 40 outputs the ultrasonic waves so that the sound pressure of the ultrasonic waves in the cleaning liquid 3 becomes 120 mV or more.
- the concentration of dissolved oxygen in the cleaning liquid 3 in the cleaning tank 10 is usually 2.0 mg / L or more. However, the lower limit of the dissolved oxygen concentration of the cleaning liquid 3 in the cleaning tank 10 does not need to be particularly controlled or controlled.
- FIG. 6 is a graph showing the relationship between the overflow time of the cleaning liquid 3, the dissolved oxygen concentration of the cleaning liquid 3, and the supply amount of the cleaning liquid 3 to the cleaning tank 10.
- the cleaning liquid 3 supplied by the supply mechanism 20 is water (industrial water) having a water temperature of about 20 ° C., and is considered to have a dissolved oxygen concentration of about 8 mg / L to 10 mg / L.
- the overflow time is the duration of the overflow of the cleaning liquid 3 in the cleaning tank 10 (the drainage from the discharge mechanism 30), in other words, the time during which the supply mechanism 20 continuously supplies the cleaning liquid 3 to the cleaning tank 10. It is.
- the dissolved oxygen concentration of the cleaning liquid 3 in the cleaning tank 10 was set to 4.5 mg / min when the supply amount of the cleaning liquid 3 to the cleaning tank 10 was 40 L / min, 100 L / min, and 150 L / min. It can be seen that it can be maintained below L.
- the supply amounts are 40 L / min and 100 L / min, the dissolved oxygen concentration of the cleaning liquid 3 in the cleaning tank 10 is maintained at 4.2 mg / L or less.
- the supply amount is less than 40 L / min, the dissolved oxygen concentration of the cleaning liquid 3 in the cleaning tank 10 is expected to further decrease.
- the supply amount is preferably set to 150 L / min or less. , 100 L / min or less.
- the supply amount of the cleaning liquid 3 per minute to the cleaning tank 10 is preferably 1.25 of the stored amount of the cleaning liquid 3 in the cleaning tank 10. % Or less, and more preferably 0.83% or less of the storage amount.
- FIG. 7 is a graph showing the relationship between the scale density of the cleaning liquid 3, the sound pressure attenuation rate of ultrasonic waves (frequency 38 kHz and sound pressure 120 mV) irradiated into the cleaning liquid 3, and the cleanability of the metal tube 2.
- the sound pressure decay rate decreases as the scale density in the cleaning liquid 3 decreases, and the sound pressure decay rate increases as the scale density increases.
- the scale density is 2.5 g / L or less, the scale adhering to the metal tube 2 is completely removed, and the cleanability by ultrasonic waves is extremely good.
- the scale density exceeds 2.5 g / L, a part of the scale remains in the metal tube 2 (remaining after washing). If the scale density exceeds 5.0 g / L, the cleaning properties by ultrasonic waves will be poor. Therefore, the scale density in the cleaning liquid 3 is preferably 2.5 g / L or less.
- FIG. 8 is a graph showing the relationship among the surface area of the metal tube 2 subjected to the cleaning treatment, the scale density of the cleaning liquid 3, and the supply amount of the cleaning liquid 3 to the cleaning tank 10.
- the conditions of the supply amount in FIG. 8 are no supply, 20 L / min, and 40 L / min.
- the cleaning liquid 3 in the cleaning tank 10 was irradiated with ultrasonic waves having a frequency of 38 kHz and a sound pressure of 120 mV.
- the processing surface area is about 4000 m 2 , and the scale density of the cleaning liquid 3 becomes slightly less than 2.0 g / L.
- the scale density reaches 2.5 g / L when the treated surface area becomes about 5000 m 2 .
- the processing surface area becomes about 5000 m 2. It is considered that the cleaning liquid 3 in the cleaning tank 10 needs to be replaced.
- the scale density of the cleaning liquid 3 is 1.0 g / L or less even if the processing surface area reaches 6000 m 2 . Therefore, when the cleaning liquid 3 is supplied to the cleaning tank 10, the replacement interval of the cleaning liquid 3 in the cleaning tank 10 becomes longer than when the cleaning liquid 3 is not supplied to the cleaning tank 10.
- the supply amount of the cleaning liquid 3 to the cleaning tank 10 is 40 L / min
- the rate of increase in the scale density becomes smaller than when the supply amount is 20 L / min, and the cleaning liquid 3 in the cleaning tank 10 is replaced. The interval is longer.
- the supply amount is preferably 20 L / min or more, and more preferably 40 L / min or more. Is more preferred.
- These supply amounts are converted into the ratio to the stored amount (about 12000 L), and the supply amount of the cleaning liquid 3 to the cleaning tank 10 per minute is preferably 0.17 of the stored amount of the cleaning liquid 3 in the cleaning tank 10. % Or more, more preferably 0.33% or more of the storage amount.
- the scale density of the cleaning liquid 3 can be maintained at 2.5 g / L or less. Therefore, the replacement interval of the cleaning liquid 3 in the cleaning tank 10 becomes longer, and the number of replacements of the cleaning liquid 3 can be reduced.
- the supply of the cleaning liquid 3 to the cleaning tank 10 and the discharge of the cleaning liquid 3 from the cleaning tank 10 are continuously performed.
- the scale separated from the metal tube 2 is discharged from the cleaning tank 10 together with the cleaning liquid 3, while a new cleaning liquid 3 is supplied to the cleaning tank 10. Therefore, as described with reference to FIGS. 7 and 8, an increase in the scale density of the cleaning liquid 3 can be suppressed, and attenuation of ultrasonic waves can be reduced. For this reason, in the ultrasonic cleaning of the metal tube 2, high cleanability can be ensured.
- the dissolved oxygen concentration of the cleaning liquid 3 is preferably 4.5 mg / L or less, more preferably 4.2 mg / L or less. Thereby, the ultrasonic cleaning performance can be improved in a wide sound pressure range.
- the supply amount of the cleaning liquid 3 per minute to the cleaning tank 10 is preferably 0.17% or more and 1.25% or less, more preferably 0% or less, with respect to the stored amount of the cleaning liquid 3 in the cleaning tank 10. 0.17% or more and 0.83% or less, more preferably 0.33% or more and 0.83% or less.
- the bottom surface of the cleaning tank 10 is an inclined surface that is inclined from one end in the longitudinal direction toward the other end. Accordingly, the cleaning liquid 3 easily enters the inside of the metal tube 2, and the inner peripheral surface of the metal tube 2 can be reliably cleaned.
- the ultrasonic irradiation mechanism 40 preferably has a frequency sweep function. Thereby, the cleaning efficiency of the metal tube 2 can be improved.
- a force called Bjrknes force acts on the microbubbles, and the microbubbles are applied to the antinodes and nodes of the ultrasonic waves according to their diameters.
- Gravitate Microbubbles having a bubble diameter of less frequency resonant diameter 2R 0 is attracted to the antinodes of the ultrasonic wave, it can contribute to cavitation cleaning.
- the frequency resonant diameter 2R 0 varies in accordance with a change in frequency, microbubbles increases contributing to cavitation cleaning. Therefore, many microbubbles can be used as nuclei for cavitation. Thereby, the cleaning efficiency of the metal tube 2 is improved.
- the ultrasonic wave transmits through the irradiation object. Therefore, by applying the ultrasonic waves while the ultrasonic irradiation mechanism 40 sweeps the frequency within an appropriate range, the ultrasonic waves transmitted through the peripheral wall of the metal tube 2 can be increased. Therefore, the cleaning efficiency of the metal tube 2 is improved.
- the ultrasonic wave is not only vertically incident on the irradiation object, but also propagates while repeating multiple reflections. Therefore, a certain sound field tends to be hardly formed.
- the cleaning liquid 3 is irradiated with ultrasonic waves while the frequency is swept in a range of ⁇ 0.1 kHz to ⁇ 10 kHz around a specific frequency. This satisfies the condition that the wavelength of the ultrasonic wave is 1 / of the wavelength corresponding to the thickness of the metal tube 2 at various positions of the metal tube 2. Therefore, at various positions of the metal tube 2, the ultrasonic waves can be transmitted from the outside to the inside of the metal tube 2.
- the step of dipping the metal tube 2, the step of supplying the cleaning liquid 3 to the cleaning tank 10, and the step of discharging the cleaning liquid 3 from the cleaning tank 10 are performed simultaneously.
- these steps are not necessarily performed simultaneously. No need to be done.
- the supply or discharge of the cleaning liquid 3 in the cleaning tank 10 may not be performed continuously.
- the metal pipe 2 is immersed in the cleaning liquid 3 in a state where the supply of the cleaning liquid 3 to the cleaning tank 10 is stopped, the volume of the metal pipe 2 is increased, and the level of the cleaning liquid 3 in the cleaning tank 10 rises. It may exceed the surface S.
- the cleaning liquid 3 in an amount corresponding to a height exceeding the reference liquid level S is discharged from the cleaning tank 10.
- the cleaning liquid 3 in the cleaning tank 10 is agitated as the metal pipe 2 is taken in and out, and the cleaning liquid 3 is connected between the cleaning tank 10 and the fine bubble generator 53 via the pipes 51 and 52. Due to the circulation of 3, the scale is always uniformly dispersed and suspended. Therefore, the cleaning liquid 3 in which the scale is dispersed and floats is discharged from the cleaning tank 10. If the new cleaning liquid 3 is supplied into the cleaning tank 10 in which the amount of the cleaning liquid 3 has been reduced after the metal tube 2 is pulled up, the scale density of the cleaning liquid 3 in the cleaning tank 10 decreases. As described above, it is possible to suppress an increase in scale density without simultaneously performing the immersion step, the supply step, and the discharge step.
- each metal tube 2 is subjected to a heat treatment after cold drawing and then to an acid pickling treatment.
- Each metal tube 2 has an outer diameter of 38 mm to 95 mm.
- Each metal pipe 2 is an austenitic stainless steel pipe and has the following chemical composition.
- the balance consists of Fe and impurities.
- the cleaning liquid 3 in the cleaning tank 10 was irradiated with ultrasonic waves by the ultrasonic irradiation mechanism 40, and fine bubbles were supplied by the fine bubble generation mechanism 50.
- cleaning conditions in this example will be described.
- Cleaning liquid industrial temperature water at normal temperature
- Storage volume of cleaning tank 12000L
- Ultrasound frequency 38kHz
- Amount of cleaning liquid supplied to the cleaning tank about 40 L / min
- the average sound pressure of ultrasonic waves and the average dissolved oxygen concentration of the cleaning liquid 3 in the cleaning tank 10 were measured every processing day.
- the average sound pressure was measured using a commercially available ultrasonic sound pressure meter (Sound pressure level monitor manufactured by Kaijo Co., Ltd., 19001D type) in a measurement mode in which the average measurement value was measured for 5 seconds. Measurements were taken in water.
- the average dissolved oxygen amount was measured using a commercially available dissolved oxygen concentration meter (LAQUA @ OM-71, manufactured by Horiba, Ltd.). Table 1 shows the weight (processing amount), the measurement result, and the evaluation of the cleaning property of the metal tube 2 after the cleaning treatment.
- the cumulative throughput of the metal tube 2 exceeded 200 tons.
- the average dissolved oxygen concentration of the cleaning liquid 3 in the cleaning tank 10 is 3.55 mg / L, and is maintained at 5.2 mg / L or less.
- the scale density of the cleaning liquid 3 is 0.108 g / L, which does not exceed 2.5 g / L at which the cleaning property starts to decrease. Therefore, the cleaning property was good over 4 days. Therefore, according to the cleaning method and the cleaning apparatus according to the present disclosure, it was confirmed that high ultrasonic cleaning performance can be ensured.
- Cleaning device 2 Metal tube 3: Cleaning liquid 10: Cleaning tank 20: Supply mechanism 30: Drainage mechanism 40: Ultrasonic irradiation mechanism 50: Fine bubble generation mechanism
Abstract
Description
図1は、実施形態に係る洗浄装置1を模式的に示す平面図である。図2は、図1に示す洗浄装置1のII-II断面図である。
洗浄槽10は、金属管2を収容可能に構成されている。超音波洗浄に際し、洗浄槽10内には、通常、複数の金属管2が同時に収容される。
供給機構20は、洗浄槽10に洗浄液3を供給する。供給機構20は、少なくとも1つの供給管21を有する。本実施形態では、供給機構20は、複数の供給管21を有する。洗浄液3は、各供給管21を介して洗浄槽10に供給される。複数の供給管21は、間隔を空けて配置されている。このため、洗浄液3は、洗浄槽10に対して分散して供給される。3つ以上の供給管21が存在する場合、新たな洗浄液3の均一供給の観点から、供給管21の間隔は、概ね均等であることが好ましい。
各排出機構30は、洗浄槽10内の洗浄液3の量が所定量を超えたときに、洗浄槽10から洗浄液3を排出する。複数の排出機構30は、間隔を空けて配置されている。このため、洗浄液3は、洗浄槽10から分散して排出される。3つ以上の排出機構30が存在する場合、排出機構30の間隔は、概ね均等であることが好ましい。なお、排出機構30は1つでもよい。
図1に戻り、超音波照射機構40は、洗浄槽10内の洗浄液3中に超音波を照射する。超音波照射機構40としては、超音波洗浄において一般に採用されている、公知の超音波振動子を用いることができる。
ファインバブル発生機構50は、洗浄槽10内の洗浄液3中の溶存気体を気泡化してファインバブルを発生させる。ファインバブル発生機構50は、洗浄槽10の外側に配置されている。洗浄槽10の長手方向の一側壁に沿って、複数のファインバブル発生機構50が配置されている。ただし、ファインバブル発生機構50の位置及び数は、特に限定されるものではない。
f0:気泡の固有振動数(Minnaert共振周波数)
R0:気泡の平均半径
p∞:周辺液体の平均圧力
γ:断熱比(空気のγ=1.4)
ρ:液体密度
である。
緩衝部材60は、洗浄槽10内に配置されている。複数の緩衝部材60は、洗浄槽10の長手方向に並んでいる。
以下、洗浄装置1を用いた金属管2の洗浄方法について説明する。
図1を再度参照して、金属管2の洗浄に際し、まず、洗浄槽10に洗浄液3を貯留する。洗浄槽10には、供給機構20によって洗浄液3が供給される。ただし、空の洗浄槽10に洗浄液3を供給する貯留工程の段階では、供給機構20以外の手段で洗浄液3を洗浄槽10に供給してもよい。洗浄槽10に供給される洗浄液3は、7mg/L~11mg/L程度の溶存酸素濃度を有していることが好ましく、8mg/L~10mg/L程度の溶存酸素濃度を有していることがより好ましい。洗浄液3は、典型的には水(水道水又は工業用水)である。洗浄液3が水温10~35℃の水(水道水又は工業用水)の場合、洗浄液3の溶存酸素濃度は、7mg/L~11mg/Lとなる。洗浄液3が水温15~25℃の水(水道水又は工業用水)の場合、洗浄液3の溶存酸素濃度は、8mg/L~10mg/Lとなる。溶存酸素濃度は、洗浄液3中の溶存気体量の指標となる。
次に、洗浄槽10に貯留された洗浄液3に、金属管2を所定時間浸漬する。金属管2は、クレーン等を使用して、洗浄槽10内の洗浄液3中に浸漬させることができる。通常、複数の金属管2を同時に洗浄液3中に浸漬させるが、金属管2を1本ずつ洗浄液3中に浸漬させてもよい。
以下、洗浄槽10内の洗浄液3の溶存酸素濃度、及び洗浄槽10に対する洗浄液3の供給量の各数値範囲について、図5から図8を参照しつつ説明する。図5から図8を用いた説明及び検証において、被洗浄物としての金属管2は、オーステナイト系ステンレス鋼管(Ni:9質量%、Cr:18.5質量%、Cu:3質量%、Nb:0.5質量%を含有)、洗浄槽10に供給される洗浄液3は、水温約20℃の水(工業用水)、洗浄槽10における洗浄液3の貯留量(基準液面Sまで貯留したときの量)は、約12000Lである。
図5は、洗浄液3の溶存酸素濃度と、洗浄液3中に照射される超音波の音圧と、金属管2の洗浄性との関係を示すグラフである。図5のグラフの作成に際し、洗浄槽10内の洗浄液3の溶存酸素濃度、及び洗浄槽10内の洗浄液3中に照射される超音波の音圧を変化させて、金属管2の洗浄性を検証した。
図6は、洗浄液3のオーバーフロー時間と、洗浄液3の溶存酸素濃度と、洗浄槽10への洗浄液3の供給量との関係を示すグラフである。図6のグラフの作成に際し、供給量を40L/min、100L/min、150L/minと変化させ、供給量ごとに洗浄液3中の溶存酸素濃度を測定した。供給機構20が供給する洗浄液3は、水温20℃程度の水(工業用水)であり、8mg/L~10mg/L程度の溶存酸素濃度を有すると考えられる。オーバーフロー時間とは、洗浄槽10における洗浄液3のオーバーフロー(排出機構30からの排水)の継続時間であり、換言すれば、供給機構20が洗浄槽10に洗浄液3を継続して供給している時間である。
図7は、洗浄液3のスケール密度と、洗浄液3中に照射される超音波(周波数38kHz及び音圧120mV)の音圧減衰率と、金属管2の洗浄性との関係を示すグラフである。
本実施形態では、金属管2が浸漬される洗浄液3にファインバブルを発生させることにより、洗浄液3中の超音波を散乱させ、3次元的に伝搬させることができる。これにより、金属管2の洗浄性が向上する。また、本実施形態では、洗浄液3中の溶存気体をファインバブル化することで、洗浄液3の溶存酸素濃度が5.2mg/L以下まで低下する。よって、図5を参照して説明したように、良好な超音波洗浄性を確保することができる。
[化学組成]
質量%で、
C:0.07~0.13%、
Si:0.30%以下、
Mn:1.0%以下、
P:0.040%以下、
S:0.010%以下、
Ni:7.5~10.5%、
Cr:17.0~19.0%、
Nb:0.30~0.60%、及び、
Cu:2.5~3.5%
を含有し、
残部がFe及び不純物からなる。
[洗浄条件]
・洗浄液:常温の工業用水
・洗浄槽の貯留量:12000L
・超音波の周波数:38kHz
・洗浄槽への洗浄液の供給量:約40L/min
2:金属管
3:洗浄液
10:洗浄槽
20:供給機構
30:排水機構
40:超音波照射機構
50:ファインバブル発生機構
Claims (9)
- 金属管の洗浄方法であって、
洗浄槽に洗浄液を貯留する貯留工程と、
前記洗浄槽内の前記洗浄液中の溶存気体を気泡化してファインバブルを発生させ、且つ前記洗浄槽内の前記洗浄液中に超音波を照射しながら、前記洗浄槽内の前記洗浄液に前記金属管を浸漬する浸漬工程と、
前記洗浄槽に新たな洗浄液を供給する供給工程と、
前記洗浄槽内において前記洗浄液の液面高さが所定の基準液面高さを超えた場合、当該基準液面高さを超えた高さに相当する量の洗浄液を前記洗浄槽から排出する排出工程と、を備える、洗浄方法。 - 請求項1に記載の洗浄方法であって、
前記浸漬工程において、前記洗浄槽内の前記洗浄液の溶存酸素濃度は、5.2mg/L以下である、洗浄方法。 - 請求項1又は2に記載の洗浄方法であって、
前記供給工程は、前記浸漬工程と同時に実施され、
前記供給工程において、前記洗浄槽への前記洗浄液の1分間当たりの供給量は、前記洗浄槽における前記洗浄液の貯留量の0.17%以上1.25%以下である、洗浄方法。 - 請求項3に記載の洗浄方法であって、
前記供給量は、前記貯留量の0.17%以上0.83%以下である、洗浄方法。 - 請求項4に記載の洗浄方法であって、
前記供給量は、前記貯留量の0.33%以上0.83%以下である、洗浄方法。 - 請求項1から5のいずれか1項に記載の洗浄方法であって、
前記金属管は、
質量%で、
C:0.01~0.13%、
Si:0.75%以下、
Mn:2%以下、
P:0.045%以下、
S:0.030%以下、
Ni:7~14%、及び、
Cr:16~20%、
を含有し、残部がFe及び不純物からなる化学組成を有する鋼管である、洗浄方法。 - 請求項6に記載の洗浄方法であって、
前記化学組成は、残部のFeの一部に換えて、質量%で、Nb:0.2~1.1%、Ti:0.1~0.6%、Mo:0.1~3%、Cu:2.5~3.5%のいずれか1種又は2種以上を含有する、洗浄方法。 - 請求項6又は7に記載の洗浄方法であって、
前記化学組成は、残部のFeの一部に換えて、質量%で、B:0.001~0.1%及びN:0.02~0.12%を含有する、洗浄方法。 - 金属管の洗浄装置であって、
洗浄液が貯留され、前記金属管が収容される洗浄槽と、
前記洗浄槽に洗浄液を供給する供給機構と、
前記洗浄槽内において前記洗浄液の液面高さが所定の基準液面高さを超えた場合、当該基準液面高さを超えた高さに相当する量の洗浄液を前記洗浄槽から排出する排出機構と、
前記洗浄槽内の前記洗浄液中の溶存気体を気泡化してファインバブルを発生させるファインバブル発生機構と、
前記洗浄槽内の前記洗浄液中に超音波を照射する超音波照射機構と、
を備える、洗浄装置。
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KR102623815B1 (ko) * | 2021-07-06 | 2024-01-11 | 가톨릭관동대학교산학협력단 | 초음파를 이용한 온돌파이프 유지관리 방법 |
CN113818022A (zh) * | 2021-10-21 | 2021-12-21 | 西安赛特思迈钛业有限公司 | 一种微孔钛合金管材的清洗方法及系统 |
CN114602900A (zh) * | 2022-02-25 | 2022-06-10 | 湖南云中科技有限公司 | 一种纳米气泡管道清洗装置 |
CN115283372A (zh) * | 2022-10-09 | 2022-11-04 | 启东市瑞禾机械有限公司 | 一种金属管制品专用除油装置 |
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JP7131622B2 (ja) | 2022-09-06 |
JPWO2020067227A1 (ja) | 2021-08-30 |
EP3858501B1 (en) | 2024-04-03 |
CN112739465B (zh) | 2022-09-13 |
CN112739465A (zh) | 2021-04-30 |
EP3858501A1 (en) | 2021-08-04 |
KR102626638B1 (ko) | 2024-01-18 |
EP3858501A4 (en) | 2022-06-08 |
KR20210049914A (ko) | 2021-05-06 |
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