Patent Grant
11839906
This application claims the benefits of PCT International Application No. PCT/JP2020/047145 filed on Dec. 17, 2020, which claims priority under 35 U.S.C. § 119(a) to Japanese Patent Application No. 2019-228830 filed on Dec. 12, 2019. The above application is hereby expressly incorporated by reference, in its entirety, into the present application.
The present invention relates to an ultrasonic treatment apparatus.
Generally, in a manufacturing process of various types of metal objects such as steel plates and steel pipes, a cleaning treatment method is widely used to remove dirt and scales on a surface of the metal object by immersing it in a cleaning tank that contains chemicals (for example, alkaline degreasing agents, surface-active agents, sulfuric acid solutions, and the like), rinses, and so on. Examples of cleaning treatment apparatuses performing such cleaning treatment methods include, for example, a treatment apparatus using high-pressure airflow injection nozzles and an ultrasonic treatment apparatus using ultrasonic waves.
Various methods have been conventionally proposed to improve propagation performance and treatment performance of ultrasonic waves in various surface treatments, including the cleaning treatment, for large materials such as steel plates and steel pipes.
For example, the following Patent Document 1 proposes a technology to improve cleaning performance by ultrasonic waves by providing a swing means to rotate an ultrasonic transducer inside a cleaning tank and by swinging the ultrasonic transducer during cleaning of a cleaning object. The following Patent Document 2 proposes a technology to improve cleaning efficiency by rotating a cleaning object and driving an ultrasonic transducer up and down during the cleaning of the cleaning object. The following Patent Document 3 proposes a technology to provide a curved surface member for reflecting ultrasonic waves against a wall surface and/or a bottom surface of a treatment tank.
However, when various drive mechanisms are installed at a portion of the cleaning tank where a cleaning liquid is contained, as in the above-mentioned Patent Documents 1 and 2, it is necessary to select a treatment liquid that will not adversely affect the drive mechanisms. In addition, an internal space of the cleaning tank cannot be used effectively for a volume of the drive mechanisms to be installed, and the number of treatment objects that can be treated at one time is reduced.
Even when using the technologies described in the above Patent Documents 1 to 3, the propagation performance and uniformity of ultrasonic waves may decrease when multiple treatment objects are arranged in the treatment tank, and there was room for further study on how to improve the propagation performance and uniformity of ultrasonic waves.
Thus, there is a need for a technology that can improve the propagation performance and uniformity of ultrasonic waves more easily, even when treating multiple treatment objects.
The present invention was made in view of the above problems, and an object thereof is to provide an ultrasonic treatment apparatus that can more easily improve the propagation performance and uniformity of ultrasonic waves, even when treating multiple treatment objects.
To solve the above problems, the present inventors have studied diligently and found that it is possible to further improve the propagation performance and uniformity of ultrasonic waves by setting a shape of a surface up to a scheduled liquid level height line of a treatment liquid (in other words, a portion in contact with the treatment liquid) of an inner surface of a treatment tank as a concave surface and irradiating ultrasonic waves toward the scheduled liquid level height line of the treatment liquid in the treatment tank.
The summary of the present invention completed based on the above findings is as follows.
(1) An ultrasonic treatment apparatus including: a treatment tank capable of containing a treatment object and a treatment liquid for immersing the treatment object; and an ultrasonic application mechanism that applies ultrasonic waves to the treatment liquid, wherein the treatment tank has a long axis where cross-sectional shapes are substantially identical to each other, and a wall surface up to a scheduled liquid level height line of the treatment liquid is formed by a concave surface, and the ultrasonic application mechanism is installed at a position where an angle θ formed by a normal line of an oscillation surface of ultrasonic waves and the scheduled liquid level line of the treatment liquid is 5° to 80°.
(2) The ultrasonic treatment apparatus according to (1), wherein the ultrasonic application mechanism is installed at a position where the angle θ is 25° to 70°.
(3) The ultrasonic treatment apparatus according to (1) or (2), wherein the ultrasonic application mechanism is not installed at a position where the angle θ is out of the range described in (1) or (2).
(4) The ultrasonic treatment apparatus according to any one of (1) to (3), wherein a cross section of the treatment tank cut in a plane perpendicular to the long axis has a shape where part of an approximate circle or ellipse is cut out.
(5) The ultrasonic treatment apparatus according to any one of (1) to (4), wherein in the cross section of the treatment tank cut in the plane perpendicular to the long axis, a distance between inner walls at the scheduled liquid level height line is 90% or more of a maximum distance M between the inner walls of the treatment tank in the cross section.
(6) The ultrasonic treatment apparatus according to any one of (1) to (5), wherein in the cross section of the treatment tank cut in the plane perpendicular to the long axis, a curvature radius R of the concave surface is 1.0 to 25.0 times a length L of the oscillation surface of the ultrasonic application mechanism in the cross section.
(7) The ultrasonic treatment apparatus according to any one of (1) to (6), wherein the ultrasonic application mechanism is installed to be capable of changing an installation position in the treatment tank in accordance with a treatment amount of the treatment object.
(8) The ultrasonic treatment apparatus according to any one of (1) to (7), wherein the treatment tank is configured to be capable of varying a length in a direction parallel to the long axis of the treatment tank by connecting or detaching treatment tank parts whose cross-sectional shapes in the cross section cut in a direction perpendicular to the long axis are substantially identical to each other.
(9) The ultrasonic treatment apparatus according to any one of (1) to (8), wherein the treatment tank can be attached to and detached from a stand that holds the treatment tank.
(10) The ultrasonic treatment apparatus according to any one of (1) to (9), wherein a portion of the stand holding the treatment tank that is in contact with the treatment tank is made of a material with a specific acoustic impedance of 1×105 to 2×106 kg·m−2·sec−1.
(11) The ultrasonic treatment apparatus according to any one of (1) to (10), wherein an area of the treatment tank at a contact portion with the stand is 40% or less of an area of an outer surface of the treatment tank.
(12) The ultrasonic treatment apparatus according to any one of (1) to (9), wherein the treatment tank is used in a state isolated from the stand.
(13) The ultrasonic treatment apparatus according to any one of (1) to (12), wherein a treatment liquid circulation path for circulating the treatment liquid is installed outside the treatment tank.
As explained above, the present invention makes it possible to improve propagation performance and uniformity of ultrasonic waves more easily, even when treating multiple treatment objects.
Hereinafter, suitable embodiments of the present invention will be described in detail with reference to the drawings. In the specification and the drawings presented below, substantially the same components are denoted by the same reference signs, and a duplicated description thereof will be omitted.
First, a brief description of an overall configuration of an ultrasonic treatment apparatus according to an embodiment of the present invention will be given with reference to
An ultrasonic treatment apparatus 1 of this embodiment is an apparatus that performs the following treatments for a surface of a treatment object (a portion in contact with a treatment liquid) by applying ultrasonic waves from ultrasonic treatment mechanisms 20 to a treatment liquid 3 under a state where the treatment object is immersed in the treatment liquid 3 contained (or filled) in a treatment tank 10. The ultrasonic treatment apparatus 1 can be used when various treatments such as cleaning, for example, are applied to treatment objects such as various types of metal objects represented by steel materials, and various types of non-metal objects represented by plastic resin members. For example, various types of metal objects such as steel pipes, shape steels, bar steels, and steel wire materials, which extend in a predetermined axial direction, can be treated as the treatment objects by using the ultrasonic treatment apparatus 1 of this embodiment to perform a pickling treatment, a degreasing treatment, and a cleaning treatment (after the pickling treatment, or other treatments) on these metal objects.
The pickling treatment is a treatment to remove oxide scales formed by heat treatment, thermal processing, and the like on a surface of the metal object, and the degreasing treatment is a treatment to remove oil such as lubricant or machining oil used in processing or the like. These pickling and degreasing treatments are pretreatments performed before applying surface finishing treatments (metal coating treatment, chemical conversion treatment, paint treatment, and other treatments) to metal objects. The pickling treatment may dissolve a part of base metal. The pickling treatment is also used to dissolve metal objects by etching to improve surface finishing quality. In some cases, the degreasing treatment is provided before the pickling treatment, and degreasing performance in the degreasing treatment may affect the scale removal in the subsequent pickling treatment. Furthermore, the degreasing treatment is also used to improve wettability, which is an indicator of oil content control as a finishing quality of a final product.
Furthermore, the ultrasonic treatment apparatus 1 of this embodiment, which will be described in detail below, can also be used for cleaning used pipes, pipes that require periodic or irregular dirt removal, or the like in addition to the cleaning process in a manufacturing line as described above.
Thus, the ultrasonic treatment apparatus 1 of this embodiment is mainly applicable to various surface treatments of treatment objects, such as long objects extending along a predetermined axial direction. Long objects where surface treatment films (for example, various oxide films, plating films, coating films after surface treatment finishing treatment, and other films) are generated on surfaces can also be used as the treatment objects. Furthermore, the ultrasonic treatment apparatus 1 of this embodiment can also be used to treat long objects to which unintentional surface attachments, such as oxide scale and oil, for example, have adhered in a film form in addition to the various types of intentionally formed films described above.
In the following, a detailed explanation will be given using an example of a case in which there is the treatment tank 10 where a treatment liquid is contained and a plurality of long objects are immersed in the treatment tank 10 as an aggregate. In this case, the aggregate of the plurality of long objects (treatment object) is immersed in the inside of the treatment tank 10 containing (or filled with) the treatment liquid 3 using a crane or other driving mechanism (not illustrated) that is capable of vertical movement. The aggregate of the plurality of long objects may also be immersed in the treatment tank 10 while bundled together by non-illustrated wires, nets, or the like.
For convenience, coordinate systems illustrated in
As illustrated in
For convenience of explanation, the expressions “inner wall” and “outer wall” of the treatment tank 10 are used below, but such expressions are for convenience only and do not mean that the treatment tank 10 has a double structure. In the following description, a surface of the treatment tank 10 that can come into contact with the treatment liquid 3 (inner surface) is referred to as the “inner wall” and a surface opposite the inner wall (outer surface) is referred to as the “outer wall”.
Here, the treatment tank 10 of the ultrasonic treatment apparatus 1 of this embodiment has a long axis (an axis corresponding to the y-axis direction in
As illustrated in the upper row of
As schematically illustrated in
When the angle θ illustrated in
From the above perspective, a size of the angle θ formed by the normal line of the oscillation surface of ultrasonic waves and the scheduled liquid level height line of the treatment liquid 3 is set to 5° to 80°. The angle θ is preferably 15° or more, more preferably 25° or more, and even more preferably 30° or more. Such an angle can further improve the efficiency of the ultrasonic application. On the other hand, when the angle θ exceeds 70°, the improvement of the propagation performance and uniformity of the ultrasonic waves may not be sufficient. The angle θ is preferably 70° or less, more preferably 65° or less, and even more preferably 60° or less. Such an angle can further improve the propagation performance and uniformity of ultrasonic waves.
In the ultrasonic treatment apparatus 1 of this embodiment, it is preferable that the ultrasonic application mechanisms 20 do not exist outside the range of the above angle θ. That is, the ultrasonic application mechanisms 20 are preferably installed only within the range of the above angle θ. By arranging the ultrasonic application mechanisms 20 in this manner, the propagation performance and uniformity of ultrasonic waves can further be improved.
Here, the plurality of ultrasonic application mechanisms 20 may not have the same value of the angle θ in this embodiment. They may have multiple values of the angle θ within the above range. However, by using the same angle θ, an installation cost can be reduced.
The ultrasonic application mechanism 20 of this embodiment may be formed by, for example, an ultrasonic generator 201 and an ultrasonic transducer 203 as illustrated in
The ultrasonic application mechanism 20 of this embodiment may be formed by, for example, the ultrasonic generator 201, and an immersion ultrasonic vibrator 211 as illustrated in
The frequency of ultrasonic waves output from the ultrasonic application mechanism 20 is, for example, preferably 18 kHz to 200 kHz. When the frequency is less than 18 kHz, the waves change to the frequency in the audible range, and propagation in solids results in significant attenuation although propagation in liquids is possible. Furthermore, ultrasonic waves may be perceived as noise, which may lead to deterioration of work environment. In addition, ultrasonic propagation may be inhibited by large-sized bubbles generated from a surface of the treatment object S, which may reduce effectiveness of ultrasonic waves in improving treatment performance. The frequency of ultrasonic waves output from the ultrasonic application mechanism 20 is more preferably 18 kHz or more. On the other hand, when the frequency of ultrasonic waves exceeds 200 kHz, a straight advancing property of ultrasonic waves when treating the treatment object becomes too strong, and the uniformity of treatment may be lowered. The frequency of ultrasonic waves output from the ultrasonic application mechanism 20 is more preferably 150 kHz or less, and even more preferably 100 kHz or less.
The frequency of ultrasonic waves to be applied is preferably selected to an appropriate value within the above range depending on a type of the treatment object, and the like. Depending on the type of the treatment object, ultrasonic waves at two or more frequencies may be applied.
The ultrasonic application mechanism 20 may also have a frequency sweep function, which is capable of applying ultrasonic waves while sweeping the frequency within a predetermined range centered on a certain selected frequency of ultrasonic waves. Such a frequency sweep function enables to achieve the following further effects.
A phenomenon is known that “transmittance of ultrasonic waves transmitting through an irradiation object reaches its maximum when a wavelength of the ultrasonic waves is ¼ of a wavelength corresponding to a thickness of the irradiation object” as a general property of ultrasonic waves. Therefore, it is possible to increase ultrasonic waves transmitted into a tubular body, when, for example, the treatment object has a hollow portion such as the tubular body, by applying ultrasonic waves while sweeping the frequency within an appropriate range. The treatment efficiency of the ultrasonic treatment apparatus 1 of this embodiment can be thereby further improved.
To ensure that ultrasonic waves are reflected at the inner wall 101, the inner wall 101 of the treatment tank 10 is preferably formed of a material capable of reflecting ultrasonic waves. More precisely, the inner wall 101 of the treatment tank 10 is preferably made of a material having a specific acoustic impedance of 1×107 kg·m−2·sec−1 to 2×108 kg·m−2·sec−1. By forming the inner wall 101 using a material whose acoustic impedance is within the above range, the inner wall 101 can reflect ultrasonic waves more reliably. The “material of the inner wall 101 of the treatment tank 10” is the “material of the treatment tank 10” when the treatment tank 10 is made from a single material (rather than a double structure, or other structures). The treatment tank 10 may have the double structure, a three-layer structure, and so on. In this case, the “material of the inner wall 101 of the treatment tank 10” means “the material of the inner wall 101 of the treatment tank 10” as it is described.
Examples of the material having the acoustic impedance of 1×107 kg·m−2·sec−1 to 2×108 kg·m−2·sec−1 or less include various metals or metal oxides and various ceramics including non-oxide ceramic, for example. Concrete examples of such materials include, for example, steel (specific acoustic impedance [unit: kg·m−2·sec−1]: 4.70×107, hereafter, a numeric value in parentheses represents a value of the specific acoustic impedance as well), iron (3.78×107), nickel-chromium steel (3.98×107), stainless steel (SUS, 4.57×107), titanium (2.73×107), zinc (3.00×107), nickel (5.35×107), aluminum (1.73×107), brass (4.06×107), duralumin (1.71×107), tungsten (1.03×108), glass (1.32×107), quartz glass (1.27×107), glass lining (1.67×107), alumina (aluminum oxide, 3.84×107), zirconia (zirconium oxide, 3.91×107), silicon nitride (SiN, 3.15×107), silicon carbide (SiC, 3.92×107), tungsten carbide (WC, 9.18×107), and so on. In the treatment tank 10 of this embodiment, the material used to form the inner wall 101 may be selected as appropriate according to liquid properties of the treatment liquid 3 to be contained, strength required for the treatment tank 10, and other factors, but it is preferable to use various metals or metal oxides having the acoustic impedance as described above.
As schematically illustrated in
The treatment liquid 3 overflowing from the treatment tank 10 flows into the overflow section 301 and is held at a portion located on the treatment tank 10 side of the overflow section 301 until the treatment liquid 3 reaches a height of the partition plate 303. When the treatment liquid 3 reaches the height of the partition plate 303, it flows over the partition plate 303 and flows into a side where the treatment liquid suction port 305 is located. The treatment liquid 3 that has reached a vicinity of the treatment liquid suction port 305 is sucked into the treatment liquid circulation pipe 307 by the treatment liquid circulation mechanism 309 such as a pump and returned to the inside of the treatment tank 10.
A fine bubble supply mechanism (not illustrated) for supplying fine bubbles to the treatment liquid may be provided at a part of the treatment liquid circulation path 30. By providing the fine bubble supply mechanism at the treatment liquid circulation path 30, the treatment performance by the treatment liquid 3 can further be improved.
Hereinabove, a brief description of the overall configuration of the ultrasonic treatment apparatus 1 of this embodiment is given with reference to
Subsequently, the treatment tank 10 and the ultrasonic application mechanism 20 in the ultrasonic treatment apparatus 1 of this embodiment are described in more detail with reference to
In any cross section cut perpendicular to the long axis direction (y-axis direction in
In this embodiment, emphasis is on reflecting ultrasonic waves emitted from the oscillation surface of the ultrasonic application mechanism 20 at the liquid level of the treatment liquid 3, as mentioned above. From this perspective, the longer the length M′ of the liquid level, the larger a reflection area of the ultrasonic waves can be obtained. Here, when the angle θ illustrated in
As a result of diligent study of a lower limit of the length M′ of the liquid level from the above perspective, it became clear that the reflection efficiency of ultrasonic waves at the liquid level can be maintained in a favorable state when the length M′ of the liquid level is 90% or more of the maximum distance M between the inner walls. From this perspective, the length M′ of the liquid level is preferably 90% or more, more preferably 93% or more, and even more preferably 95% or more of the maximum distance M between the inner walls.
At any cross section of the treatment tank 10 cut in the depth direction of the treatment tank 10 (z-axis direction in
Here, when individual ultrasonic transducer 203 as illustrated in
In general, an efficient size of a transducer when emitting ultrasonic waves is determined when the output of the ultrasonic generator 201 is set. When using individual ultrasonic generator 201 as illustrated in
When the size (volume) of the treatment tank 10 is set to a large value, it is preferable to adjust the length of the treatment tank 10 in the long axis direction (y-axis direction in
The treatment tank 10 may be configured such that the length in the long axis direction can be varied by preparing treatment tank parts (not illustrated) having approximately identical cross-sectional shapes in the cross sections cut perpendicular to the long axis direction in the depth direction (z-axis direction) of the treatment tank 10, and connecting or detaching such treatment tank parts. By configuring the treatment tank 10 in such a way that it can be divided, the length of the treatment tank 10 in the long axis direction can be adjusted more easily.
As schematically illustrated in
As schematically illustrated in
A mechanism for changing the installation position of the ultrasonic application mechanism 20 is not limited, and various mechanisms can be employed as appropriate. For example, by providing a rail (not illustrated) or other mechanisms for moving and fixing the ultrasonic application mechanism 20 on the inner wall 101 of the treatment tank 10, the installation position of the ultrasonic application mechanism 20 can be adjusted easily so that the angle θ becomes a desired value. Such a rail mechanism occupies less space in the treatment tank 10, and it is possible to use various types of treatment liquids 3 as needed by applying appropriate surface treatment to the rail.
In
When the ultrasonic application mechanism 20 is installed on the outer wall 103 side of the treatment tank 10, a method of fixing the ultrasonic application mechanism 20 is not limited, as long as it is possible to hold the oscillation surface of ultrasonic waves of the ultrasonic application mechanism 20 in contact with the outer wall 103 of the treatment tank 10.
When the ultrasonic application mechanism 20 is fixed to the outer wall 103 of the treatment tank 10 through an adhesive layer 21 using various types of adhesives, or the like, a thickness of the adhesive layer 21 is preferably set to 1 mm or less so as not to be affected by an adhesive material as much as possible to ensure more reliable propagation of ultrasonic waves to the treatment liquid 3. The ultrasonic transducer portion of the ultrasonic application mechanism 20 and the treatment tank 10 are preferably made of equivalent materials or materials having approximate specific acoustic impedance, and are preferably fixed, bonded, or joined so that there are no gaps and air layers (including air bubbles).
As illustrated in
As schematically illustrated in an upper row of
The ultrasonic treatment apparatus 1 of this embodiment can also be used with the treatment tank 10 held on the stand 40 as illustrated in the lower row of
Furthermore, the stand 40 itself may be formed using wood or plastic resin, for example, such as phenolic resin, as a material. Although wood and plastic resin such as phenolic resin have a slightly larger specific acoustic impedance than the silicone rubber, natural rubber, and polyethylene foam described above, they have a sufficiently small specific acoustic impedance compared to metal. Therefore, the attenuation of ultrasonic waves at the interface between the treatment tank 10 and the stand 40 can be more reliably suppressed.
The more the portion in contact with the stand 40, the more likely it is that ultrasonic waves will be attenuated. From this perspective, an area of the portion of the treatment tank 10 in contact with the stand 40 is preferably 40% or less of a surface area of the treatment tank 10. From the perspective of suppressing the attenuation of ultrasonic waves, the smaller the area of the contact portion in relation to the surface area of the treatment tank 10, the better, and a lower limit value thereof is not specified.
With reference to
As explained above, according to this embodiment, the inner wall 101 of the treatment tank 10 in which the treatment liquid 3 is contained has the concave surface, the ultrasonic application mechanisms 20 are installed toward the liquid level at a predetermined angle, and thereby, it is possible to achieve the ultrasonic treatment apparatus 1 in which ultrasonic waves propagate efficiently from the entire treatment tank 10 to the treatment object S. In the ultrasonic treatment apparatus 1, the reflection of ultrasonic waves from the liquid level and the ultrasonic propagation to the treatment object from various angles on the inner wall 101 of the treatment tank 10 enables efficient treatment.
Hereinabove, the ultrasonic treatment apparatus 1 of this embodiment has been described in detail.
The ultrasonic treatment apparatus according to the present invention will be concretely described below, showing examples and comparative examples. The examples shown below are only one example of the ultrasonic treatment apparatus of the present invention, and the ultrasonic treatment apparatus of the present invention is not limited to the examples shown below.
SUS material with a thickness of 5 mm (specific acoustic impedance: 4.57×107 kg·m−2·sec−1) was used to form the treatment tank 10. In this process, the length of the treatment tank 10 (length in the y-axis direction in
Example 16 below verified the case without the above-mentioned polyethylene foam sheet, Example 17 below verified the case where the area of the contact portion was set to 50%, and Example 18 below verified the case where the area of the contact portion was set to 50% and there was no polyethylene foam sheet. Example 19 below verified the case where the stand 40 made of phenolic resin was used, the area of the contact portion was set to 50%, and there was no polyethylene foam sheet. Example 20 below verified the case where the stand 40 made of wood was used, the area of the contact portion was set to 50%, and there was no polyethylene foam sheet.
Verification was performed while using a used waste oil well pipe, which is 100 mm in outer diameter×2 to 4 m in length, as the treatment object S, by immersing in the treatment tank 10 containing the treatment liquid for three minutes, and then performing a treatment to clean oxide scales remaining in the pipe with water. Clean water with a liquid temperature of 30° C. was used as the treatment liquid. A ratio of the length M′ of the liquid level to the maximum distance M between the inner walls (M′/M) was made to be constant at 85%, 90% or 100%, with a percentage adjusted by the height of the liquid level of the treatment liquid.
The ultrasonic generator of the ultrasonic application mechanism 20 had an output of 1200 W, and eight pieces of ultrasonic transducers were fixed to the inner wall side or outer wall side of the treatment tank 10 at an installation interval of 0.5 m for verification. The ultrasonic transducers of the ultrasonic application mechanism 20 installed on the inner wall side of the treatment tank 10 were the immersion ultrasonic vibrator 211 made of SUS (0.4 m in width×0.3 m in length×0.08 m in thickness) as illustrated in
Three pieces of used waste oil well pipes, the treatment object S, were bundled, immersed while being suspended at a center of the treatment tank 10 by a crane, and then cleaning was performed with the treatment tank 10 itself placed on the stand 40, although it was not welded to the stand 40, and ultrasonic intensity was measured as well as performing cleaning evaluation. In Example 6 below, cleaning was performed under a state where the treatment tank 10 was isolated from the stand 40 by further lifting the treatment tank 10 itself using a crane, and ultrasonic intensity was measured as well as performing cleaning evaluation.
The ultrasonic intensity was measured using an ultrasonic level monitor (19001D, manufactured by KAIJO), and the ultrasonic intensities (mV) at 10 points in two rows in a longitudinal direction at a center of the treatment tank were measured. In the long axis direction (y-axis direction) of the treatment tank 10, 10 measurement points were set at measurement intervals of every 0.4 m along the y-axis direction from an end portion. In a cross section (xz plane) of the treatment tank 10, two measurement points were set 0.2 m apart from a center position of the cross section of the treatment tank 10. A total of 20 measurement points were set in the entire treatment tank 10. The obtained 20 measurement values were averaged and a standard deviation σ was calculated. In this case, relative ultrasonic intensity (a measurement result of Comparative Example 1, namely, relative intensity when the measured ultrasonic intensity in the case where the treatment object S was installed in a square tank, assuming irradiation with the transducers arranged on a side surface of the tank, and the measured ultrasonic intensity was set as 1) and the standard deviation σ were calculated to compare the propagation performance of ultrasonic waves into the treatment object S and the treatment tank.
In this experimental example, an oxide scale removal rate on an inner surface of the pipe was measured, and the measured removal rate was evaluated as water-cleaning performance. In more detail, the oxide scales on the inner surface of the pipe before and after water cleaning were photographed using a fiber scope, and the oxide scale removal rate was calculated using a binarized image. The oxide scale removal rate was defined as a percentage of an oxide scale removal amount under each condition to an oxide scale remaining amount before water-cleaning. Evaluation criteria for the water-cleaning performance in Table 1 below are as follows.
Removal rate of oxide scale remaining film
100% or less to 95% or more: A
Less than 95% to 90% or more: B
Less than 90% to 85% or more: C
Less than 85% to 80% or more: D
Less than 80% to 60% or more: E
Less than 60% to 40% or more: F
Less than 40%: G
Grades A, B, and C mean that the water-cleaning performance was very good, grade D means that the water-cleaning performance was good, grade E means that the water-cleaning performance was somewhat difficult, and grades F and G mean that the water-cleaning performance was poor. Grades A to D were considered acceptable.
Setting conditions of the treatment tank 10 and ultrasonic application mechanism 20, as well as results obtained, were summarized in Table 1 below.
In the “inner wall cross-sectional shape” column of Table 1 below, the description “parallel” means that the bottom surface of the treatment tank 10 is parallel to the liquid level, and the description “inclined” means that the bottom surface of the treatment tank 10 is oblique (but not curved) to the liquid level. In the “angle θ” column, the description “vertical” means that the ultrasonic transducer of the ultrasonic application mechanism 20 is installed at the bottom surface of the treatment tank 10 (square tank) (that is, θ=90°), and the description “parallel” means that the ultrasonic transducer (immersion ultrasonic vibrator 211) of the ultrasonic application mechanism 20 is installed on the side surface of the treatment tank 10 (square tank) (that is, θ=0°).
As it is clear from Table 1 above, in each of the examples corresponding to the comparative examples of the present invention, the relative ultrasonic intensity was a relatively small value, and the cleaning performance failed. On the other hand, in each of the examples corresponding to the examples of the present invention, the relative ultrasonic intensity became a large value and the standard deviation of the ultrasonic intensity became small, and furthermore, excellent cleaning performance was exhibited.
Preferred embodiments of the present invention have been described above in detail with reference to the attached drawings, but the present invention is not limited to the embodiments. It should be understood that various changes and modifications are readily apparent to those skilled in the art who has the common general knowledge in the technical field to which the present invention pertains, within the scope of the technical spirit as set forth in claims, and they should also be covered by the technical scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-228830 | Dec 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/047145 | 12/17/2020 | WO |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2021/125260 | 6/24/2021 | WO | A |
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| Number | Date | Country | |
|---|---|---|---|
| 20230037005 A1 | Feb 2023 | US |
