KR20220136738A - Appartus for eliminating water or powder in wet type waste gas cleaning unit - Google Patents

Abstract

The present invention relates to an apparatus for removing moisture or dust particles in a wet cleaning unit, in which moisture or dust particles included in waste gas are effectively collected and removed in the wet cleaning unit like a wet cleaner of a wet scrubber or a hybrid scrubber by the centrifugal force generated in accordance with the rotation of a rotary brush to prevent exhaust duct blockage in advance. The apparatus for removing moisture or dust particles in a wet cleaning unit according to one embodiment of the present invention comprises: a lower shaft support installed in the lower portion inside the wet cleaning unit for wet-cleaning waste gas; an upper shaft support installed in the upper portion inside the wet cleaning unit; a rotary brush which is installed across the lower shaft support and the upper shaft support so that the central shaft thereof can rotate vertically, and which has a plurality of brush bristles on the outer circumferential surface; a driving actuator provided on one side of the wet cleaning unit; and an electric module which electrically connects the central shaft of the rotary brush and the driving actuator to rotate the central shaft of the rotary brush.

Description

Moisture or dust removal device for wet cleaning unit {APPARTUS FOR ELIMINATING WATER OR POWDER IN WET TYPE WASTE GAS CLEANING UNIT}

The disclosed content relates to a moisture or dust removal device of a wet cleaning unit installed in a wet cleaning unit that purifies and discharges waste gas used in a semiconductor or display manufacturing process below an appropriate reference value to remove moisture or dust.

Unless otherwise indicated herein, the material described in this section is not prior art to the claims of this application, and inclusion in this section is not an admission that it is prior art.

Although there are significant differences depending on the type of semiconductor such as DRAM, SD RAM, flash memory, and silicon semiconductor, semiconductor manufacturing usually includes wafer manufacturing process, circuit design and mask manufacturing process, oxidation, photosensitization, exposure, and development. , a wafer processing process including etching, ashing, chemical vapor deposition (CVD), and the like, and a package process. For example, the above-described semiconductor manufacturing process is also applied to the manufacture of displays such as FPD.

In the case of semiconductor manufacturing process, high-purity H ₂ , SiH ₄ (monosilane) or SiHCl ₃ (silicon trichloride) process gas is used, and for chemical vapor deposition, high-purity SiH ₄ , SiH ₂ Cl ₂ , SiHCl ₃ , SiCl ₄ , GeH ₄ , B ₂ H ₆ , BBr ₃ , BCl ₃ , AsH ₃ , PH ₃ , TeH _{2 ,} SnCl ₄ , GeCl ₄ , WF ₆ , NH ₃ , CH ₄ , Cl ₂ , MoF ₆ and other special process gases High purity hydrogen (H ₂ ) and nitrogen (N ₂ ) are used as carrier gas. In addition, process gases such as SiF ₄ , CF ₄ , C ₃ F ₈ , C ₂ F ₆ , CHF ₃ , CClF ₃ , O ₂ are used for plasma etching, and C ₃ F ₈ , CHF ₃ , CClF ₃ , CF is used for ion beam etching. A special process gas such as ₄ is used.

On the other hand, the process gas used in semiconductor manufacturing has strong characteristics such as toxicity, flammability and corrosion, and contains harmful components such as volatile organic compounds (VOC _S ). Here, volatile organic compounds are a generic term for liquid or gaseous organic compounds that are easily evaporated into the atmosphere due to their high vapor pressure. It is known not only as a cause of air pollution but also as a carcinogen.

Only a part of the process gas participates in the reaction within the manufacturing facility, and the remaining 90% of the process gas is discharged from the manufacturing facility in an unreacted state. If the process gas (hereinafter referred to as 'waste process gas') discharged in this way is released into the atmosphere without a separate purification process, it causes damage to surrounding manufacturing facilities, serious environmental pollution and safety accidents for workers. A scrubber for decomposing or purifying waste gas below a standard value is installed on the gas discharge line connected to the duct.

Such a scrubber decomposes or purifies waste gas using the characteristics of the waste gas, that is, the property of explosive reaction upon contact with air, the property of combustion, the property of reacting with a gas treatment agent, and the property of dissolving in water. It is largely divided into dry scrubbers and wet scrubbers, and mixed scrubbers that combine dry and wet scrubbers.

The dry scrubber has a structure in which the waste gas is directly burned or oxidized by passing it into the flame or plasma of the burner, or pyrolyzed by passing the waste gas into a high-temperature chamber formed by a heat source such as a heater, for example. Such a dry scrubber has an excellent effect in treating flammable (flammable) waste gas, but is inappropriate for treating waste gas that does not burn well, such as water-soluble gas.

The wet scrubber has a relatively simple configuration of cleaning and cooling after collecting waste gas using water spray, and has the advantage of being easy to manufacture and capable of increasing the capacity. However, it is impossible to treat the water-insoluble waste gas, and in particular, it is inappropriate for the treatment of waste gas containing highly flammable hydrogen groups.

The mixed scrubber has a structure in which waste gas is first combusted in a reactor to remove flammable gas and explosive gas, and then water-soluble and toxic waste gas is dissolved in water through water injection. Model Registration No. 20-0405303 (published on Jan. 10, 2006), Korean Patent Publication No. 10-2010-0021135 (published on Feb. 24, 2010), Korean Patent Registration No. 10-1431452 (published on Aug. 12, 2014), Republic of Korea It is disclosed in Patent Registration No. 10-1568804 (2015.11.12. Announcement) and the like.

Looking at the process of waste gas being treated by the above-described mixed scrubber, waste gas generated in the process chamber of a semiconductor manufacturing facility is introduced into the dry reaction unit (Reactor) and then burned/oxidized primarily by the flame of the burner or high-temperature plasma Or, the waste gas that has undergone primary pyrolysis and primary purification treatment by a heater is moved to the wet zone having a water spray structure, and the water-soluble toxic components contained in the waste gas are dissolved and dust is collected at the same time. Then, it goes through secondary cleaning in which it falls into the lower water tank and is collected, and the cleaned process gas is finally discharged into the atmosphere through a filter (water removal, etc.) and an exhaust duct.

However, when moisture and dust are not properly collected and removed in wet cleaning units such as wet scrubbers and wet cleaning units of wet scrubbers and mixed scrubbers, there is a problem in that the exhaust duct is blocked by condensation of moisture and adhesion of dust.

As an example of a method for solving this problem, a palling is installed in the wet cleaning unit as in Republic of Korea Utility Model Registration No. 20-0405303 (announced on January 10, 2006), or Republic of Korea Patent Registration No. 10-1312414 (October 14, 2013). An electric precipitator using corona discharge is also installed in the wet cleaning unit as shown in the notice).

However, in the former case, it is easy to treat water-soluble toxic components, but the inflow of moisture and dust into the exhaust duct cannot be prevented. There is this.

1. Republic of Korea Utility Model Registration No. 20-0405303 (2006.01.10. Announcement) 2. Republic of Korea Patent Publication No. 10-2010-0021135 (published on February 24, 2010) 3. Republic of Korea Patent Registration No. 10-1431452 (2014.08.12. Announcement) 4. Republic of Korea Patent Registration No. 10-1568804 (2015.11.12. Announcement) 5. Republic of Korea Patent Registration No. 10-1312414 (2013.10.14. Announcement)

In the wet cleaning unit such as the wet cleaning unit of the wet scrubber and the mixed type scrubber, the water or dust contained in the waste gas is effectively captured and removed by the centrifugal force according to the rotational driving of the rotary brush, so that the blockage of the exhaust duct can be prevented in advance. An object of the present invention is to provide a moisture or dust removal device for a wet cleaning unit.

In addition, it is not limited to the technical problems as described above, and it is obvious that another technical problem may be derived from the following description.

The disclosed contents include a lower shaft support installed on the inner lower side of a wet cleaning unit for wet cleaning of waste gas, an upper shaft support installed on an inner upper side of the wet cleaning unit, and a central shaft across the lower shaft support and the upper shaft support The rotating brush installed rotatably vertically and provided with a plurality of brush bristles on the outer circumferential surface, a driving actuator provided on one side of the wet cleaning unit, and a central axis of the driving actuator and the rotating brush are electrically connected to form the rotating brush. An apparatus for removing moisture or dust of a wet cleaning unit including an electric module for rotating a central shaft is presented as an embodiment.

According to a preferred feature of the disclosure, one end is fixed to the lower shaft support and the upper shaft support, is spaced apart from the central axis of the rotary brush, extends vertically, and is collected by the brush bristles of the rotary brush when the rotary brush is rotated. It further includes a brushing bar to shake off moisture or dust.

According to a preferred feature of the disclosed subject matter, the brush bristles are formed to be divided into a lower brush bristle part and an upper brush bristle part based on the longitudinal central part of the central axis of the rotating brush.

According to a preferred feature of the disclosure, the driving actuator is a driving motor, and the electric module includes a driving sprocket installed on an output shaft of the driving actuator, an electric sprocket installed on a central shaft of the rotating brush, the driving sprocket and the It includes a rolling chain for electrically connecting the electric sprocket, a side projecting frame is installed in communication with one side of the wet cleaning unit, and the driving actuator is installed so that the output shaft protrudes into the side projecting frame.

According to a preferred feature of the disclosure, the driving actuator is a cylinder mechanism, and the electric module includes a rack gear formed on a piston rod of the driving actuator, and a pinion gear provided on a central shaft of the rotating brush and meshed with the rack gear. It includes, wherein the driving actuator is installed in the wet cleaning unit so that the piston rod penetrates into the wet cleaning unit.

According to the apparatus for removing moisture or dust of a wet cleaning unit according to the disclosed embodiment, moisture contained in waste gas by centrifugal force according to rotational driving of a rotary brush in a wet cleaning unit such as a wet cleaning unit of a wet scrubber and a mixed type scrubber Alternatively, there is an advantage that the blockage of the exhaust duct can be prevented in advance as the dust is effectively collected and removed.

According to the apparatus for removing moisture or dust of the wet cleaning unit according to the disclosed embodiment, as the brushing bar is fixedly installed on the lower shaft support and the upper shaft support, the brush bristles of the rotary brush collide with the brushing bar when the rotary brush rotates. Moisture or dust collected on the brush bristles of the rotating brush can be removed by shaking off, and there is an advantage that the bristles of the rotating brush can be automatically cleaned.

The effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

1 is a schematic installation structure diagram of an apparatus for removing moisture or dust of a wet cleaning unit according to an embodiment of the present disclosure;
Figure 2 is a partially cut-away perspective view of the moisture or dust removal device of the wet cleaning unit according to an embodiment of the disclosed subject matter.
3 is a cross-sectional view of an apparatus for removing moisture or dust of a wet cleaning unit according to an embodiment of the present disclosure;
4 is a structural diagram of an embodiment of an electric module other than a driving actuator in the apparatus for removing moisture or dust of a wet cleaning unit according to an embodiment of the present disclosure;
5 is a structural diagram of another embodiment of an electric module other than a driving actuator in the apparatus for removing moisture or dust of a wet cleaning unit according to an embodiment of the present disclosure;

Hereinafter, with reference to the accompanying drawings, the configuration and effect of the preferred embodiment will be described. For reference, in the following drawings, each component is omitted or schematically illustrated for convenience and clarity, and the size of each component does not reflect the actual size. In addition, the same reference numerals refer to the same components throughout the specification, and reference numerals for the same components in individual drawings will be omitted.

As shown in FIG. 1 , the moisture or dust removal apparatus 1 of a wet cleaning unit according to an embodiment of the disclosed subject matter is a wet scrubber or mixed type for wet cleaning, for example, waste gas used in a semiconductor manufacturing process or a display manufacturing process. It is installed in the wet cleaning unit 3 such as the wet cleaning unit of the scrubber and serves to improve the effect of collecting and removing moisture or dust contained in the waste gas.

Due to the installation of the moisture or dust removal device 1 of the wet cleaning unit according to the embodiment of the disclosure, the exhaust duct 5 connected to the wet cleaning unit 3 such as the wet scrubber or the wet cleaning unit of the mixed scrubber It is possible to prevent moisture or dust from reaching, and the phenomenon that the exhaust duct 5 is blocked due to adsorption of moisture or dust can be prevented in advance.

FIG. 2 is a detailed structural diagram of an apparatus for removing moisture or dust of a wet cleaning unit according to an embodiment of the disclosed subject matter, and FIG. 3 is a cross-sectional view of an apparatus for removing moisture or dust of a wet cleaning unit according to an embodiment of the disclosed subject matter.

As shown in FIGS. 2 and 3 , the moisture or dust removal device 1 of the wet cleaning unit according to the embodiment of the disclosure is a lower shaft installed inside the wet cleaning unit 3 for wet cleaning waste gas. The support 10, the upper shaft support 20 installed on the inner upper side of the wet cleaning unit 3, and the central shaft 31 are vertically rotated across the lower shaft support 10 and the upper shaft support 20 A rotating brush 30 provided on the outer circumferential surface and provided with a plurality of brush bristles 33, a driving actuator 40 provided on one side of the wet cleaning unit 3, a driving actuator 40 and a rotating brush ( 30) by electrically connecting the central shaft 31 to include an electric module 50 for rotationally driving the central shaft 31 of the rotary brush 30.

Here, the lower shaft support 10 is to rotatably support the lower end of the central shaft 31 of the rotary brush 30 to be described later, and is fixedly installed on the inner lower side of the wet cleaning unit 3 .

The lower shaft support 10 has a horizontal bar shape extending across the inner lower center of the wet cleaning unit 3, and the lower end of the central shaft 31 of the rotary brush 30 is located in the center of its upper surface, for example. It is rotatably installed through a bearing. Waste gas can flow through the space between both sides of the lower shaft support 10 and the inner lower edge of the wet cleaning unit 3 .

The upper shaft support 20 rotatably supports the upper end of the central shaft 31 of the rotary brush 30 to be described later, and is fixedly installed on the inner upper side of the wet cleaning unit 3 .

The upper shaft support 20 has a horizontal bar shape extending across the inner upper center of the wet cleaning unit 3, and the upper end of the central shaft 31 of the rotary brush 30 is located at the center of its lower surface, for example, a shaft It is installed rotatably through a bearing. Waste gas can flow through the space between both sides of the upper shaft support 20 and the inner upper edge of the wet cleaning unit 3 .

The above-described lower shaft support 10 and the upper shaft support 20 can be integrally installed in the flange connection portion of the wet cleaning unit (3).

Inside the wet cleaning unit 3, the rotary brush 30 is rotatably installed over the lower shaft support 10 and the upper shaft support 20 described above. The rotary brush 30 is rotationally driven in the wet cleaning unit 3 and collects untreated water or dust despite the wet cleaning of the wet cleaning unit 3, and at the same time, through the centrifugal force generated by the rotation, moisture or It serves to double the wet cleaning effect by colliding the dust with the inner wall of the wet cleaning unit (3).

The rotating brush 30 has a structure in which a central shaft 31 is vertically rotatably installed and a plurality of brush bristles 33 are provided on an outer circumferential surface of the central shaft 31, and the brush bristles 33 are the rotating brushes. It is preferable to be formed to be partitioned into the lower brush cap 35 and the upper brush cap 37 based on the longitudinal central part of the central axis 31 of (30).

The brush bristles 33 may extend radially and horizontally with respect to the central axis 31 , but may also extend radially downwardly inclined with respect to the central axis 31 .

In this case, the wet cleaning unit 3 is provided on the lower side of the lower shaft support 10 and includes a first wet cleaning nozzle 7 for spraying water downward, the lower shaft support 10 and the upper shaft support 20 . It is preferable to include a second wet cleaning nozzle (9) provided between and spraying water onto the lower brush cap (35).

Among the brush bristles 33 of the rotary brush 30, the lower brush bristles 35 remove the untreated aqueous gas from the waste gas through the first wet washing nozzle 7 through the second wet washing nozzle ( 9), the second wet cleaning is carried out through water sprayed from The second wet cleaning effect is doubled by causing moisture or dust to collide with the inner wall of the wet cleaning unit 3 and move downward through the centrifugal force generated according to the rotation.

In addition, the upper brush bristles 37 among the brush bristles 33 of the rotary brush 30 are primary wet cleaning by the first wet cleaning nozzle 7 in the waste gas and the secondary wet cleaning by the second wet cleaning nozzle 9 in the waste gas. Exhaust duct by collecting moisture or dust that has not been treated despite cleaning and at the same time collides moisture or dust with the inner wall of the wet cleaning unit 3 through centrifugal force generated according to the rotation of the rotary brush 30 to move downward. (5) It plays a role of removing just before exhaust to the furnace.

The above-mentioned rotary brush 30 is preferably made of a synthetic resin material having a certain level of rigidity and chemical resistance as a whole, but according to an embodiment, only the upper and lower ends of the central shaft 31 are made of a high-strength metal material. It may be integrally coupled to the shaft 31,

A driving actuator 40 is provided on one side of the wet cleaning unit 3 described above. The driving actuator 40 serves to generate a driving force for rotationally driving the central shaft 31 of the rotating brush 30, for example, a rotational actuator that generates rotational motion such as a driving motor or, for example, a cylinder mechanism. A linear actuator that generates a linear reciprocating motion is applicable.

The above-described driving actuator 40 and the central shaft 31 of the rotary brush 30 are electrically connected by the electric module 50 . The electric module 50 transfers the driving force of the driving actuator 40 to the central shaft 31 of the rotating brush 30 and serves to rotate the rotating brush 30, for example, an electric chain mechanism, electric It can be formed with a belt mechanism, an electric gear set, etc.

4 is a structural diagram of an embodiment of an electric module other than a driving actuator in the apparatus for removing moisture or dust of a wet cleaning unit according to an embodiment of the present disclosure;

4, the driving actuator 40 may be a driving motor, and the electric module 50 may be formed of a electric chain mechanism.

In this case, for the installation of the driving actuator 40 formed of a driving motor, a side protrusion frame 3a is installed on one side of the wet cleaning unit 3 to communicate with each other, and the driving actuator 40 has an output shaft protruding from the side in the vertical direction. It may be installed to protrude into the frame (3a). The driving actuator 40 formed of a driving motor is preferably provided with a reduction gear unit integrally.

The electric module 50 formed of a electric chain mechanism includes a driving sprocket 51 installed on the output shaft of the driving actuator 40, and an electric sprocket 53 installed on the central shaft 31 of the rotating brush 30, It may include a transmission chain 55 for electrically connecting the driving sprocket 51 and the electric sprocket 53 .

Although not shown, the electric module 50 may also be formed as an electric belt mechanism. In this case, the electric module 50 includes a driving pulley installed on the output shaft of the driving actuator 40 and the center of the rotating brush 30 . It may include an electric pulley installed on the shaft 31, and an electric belt for electrically connecting the driving pulley and the electric pulley.

5 is a structural diagram of another embodiment of an electric module other than a driving actuator in the apparatus for removing moisture or dust of a wet cleaning unit according to an embodiment of the present disclosure;

As shown in FIG. 5 , the driving actuator 40 may be a cylinder mechanism, and the electric module 50 may be an electric gear set including a rack gear 57 and a pinion gear 59 .

The actuator 40 driven by a pneumatic or hydraulic cylinder mechanism is preferably installed on the side of the wet cleaning unit 3 so that the piston rod horizontally penetrates into the vertically arranged wet cleaning unit 3 .

The electric module 50 formed as an electric gear set is provided on the rack gear 57 formed on the piston rod of the driving actuator 40 and the central shaft 31 of the rotary brush 30 and is connected to the rack gear 57 . It may include a pinion gear 59 that meshes.

In addition, the brush bristles 33 of the above-described rotary brush 30 may be contaminated by adsorption of moisture or dust contained in the waste gas. In order to prevent contamination of the brush bristles 33 , the lower shaft support 10 and the upper shaft support 20 have a brushing bar 60 to shake off moisture or dust adsorbed on the brush bristles 33 . Can be fixedly installed.

As the brush bristles 33 of the rotating brush 30 collide when the rotating brush 30 rotates, the brushing bar 60 shakes off moisture or dust collected in the brush bristles 33 of the rotating brush 30 . To be removable, one end is fixed to the lower shaft support 10 or the upper shaft support 20 and is spaced apart from the central shaft 31 of the rotary brush 30 and extends vertically.

The brushing bar 60 is for automatic cleaning of the brush bristles 33 of the rotary brush 30 that may be contaminated by the adsorption of moisture or dust, and is formed of a metal rod or pipe having a certain level of rigidity and chemical resistance or Alternatively, it can be formed of a synthetic resin rod or pipe having a certain level of rigidity and chemical resistance.

As described above, in the apparatus 1 for removing moisture or dust of the wet cleaning unit according to the disclosed embodiment, the rotary brush 30 is provided in the wet cleaning unit 3 such as the wet cleaning unit of the wet scrubber and the mixed scrubber. As it is formed in a rotationally driven structure, moisture or dust contained in the waste gas is collected by the rotational brush 30 by the centrifugal force according to the rotational driving of the rotational brush 30 and is generated by the rotation of the rotational brush 30 at the same time Due to the centrifugal force, it collides with the inner wall of the wet cleaning unit 3, moves downward and is removed, thereby preventing blockage of the exhaust duct in advance.

According to the apparatus for removing moisture or dust of the wet cleaning unit according to the disclosed embodiment, as the brushing bar 60 is fixed to the lower shaft support 10 and the upper shaft support 20, when the rotary brush 30 rotates As the brush bristles 33 of the rotating brush 30 collide with the brushing bar 60, the moisture or dust collected in the brush bristles 33 of the rotating brush 30 may be shaken off and removed, and the rotating brush 30 ) of the brush bristles 33 are automatically cleaned.

Although the wet cleaning unit 3 in which the moisture or dust removal device of the wet cleaning unit according to the disclosed embodiment is installed is illustrated as being arranged in a vertical direction, it may be arranged in a horizontal direction according to an embodiment. In this case, terms indicating a positional relationship such as lower and upper can be replaced with one side and the other side.

Although the preferred embodiment of the present invention has been described with reference to the accompanying drawings, the embodiments described in the present specification and the configuration shown in the drawings are only the most preferred embodiment of the present invention and represent all of the technical spirit of the present invention. Therefore, it should be understood that there may be various equivalents and modifications that can be substituted for them at the time of filing the present application. Therefore, the embodiments described above are to be understood as illustrative and not restrictive in all respects, and the scope of the present invention is indicated by the following claims rather than the detailed description, and the meaning and scope of the claims and their All changes or modifications derived from the concept of equivalents should be construed as being included in the scope of the present invention.

1: Moisture or dust removal device of wet cleaning unit
3: Wet cleaning unit
3a: side projecting frame
5: exhaust duct
7: first wet cleaning nozzle
9: 2nd wet cleaning nozzle
10: lower shaft support
20: upper shaft support
30: rotating brush
31: central axis
33: brush bristles
35: lower brush parent part
37: upper brush part
40: drive actuator
50: electric module
51: drive sprocket
53: electric sprocket
55: electric chain
57: rack gear
59: pinion gear
60: brushing bar

Claims (5)

a lower shaft support installed on the lower side of the wet cleaning unit for wet cleaning of waste gas;
an upper shaft support installed on the inner upper side of the wet cleaning unit;
a rotating brush having a central axis vertically rotatable across the lower shaft support and the upper shaft support and having a plurality of brush bristles on an outer peripheral surface;
a driving actuator provided on one side of the wet cleaning unit; and
Moisture or dust removal apparatus of the wet cleaning unit including an electric module for electrically connecting the driving actuator and the central axis of the rotating brush to rotationally drive the central axis of the rotating brush. The method according to claim 1,
A brushing bar having one end fixed to the lower shaft support and the upper shaft support, spaced apart from the central axis of the rotary brush, extending vertically, and brushing off moisture or dust collected in the brush bristles of the rotary brush when the rotary brush is rotated. Moisture or dust removal device of the wet cleaning unit, characterized in that it further comprises a. The method according to claim 1,
The brush bristles are water or dust removal device of the wet cleaning unit, characterized in that it is formed to be divided into a lower brush bristles and an upper brush bristles based on the longitudinal central part of the central axis of the rotating brush. The method according to claim 1,
The driving actuator is a driving motor,
The electric module includes a driving sprocket installed on the output shaft of the driving actuator, an electric sprocket installed on the central axis of the rotating brush, and a transmission chain electrically connecting the driving sprocket and the electric sprocket,
A side protrusion frame is installed in communication with one side of the wet cleaning unit, and the drive actuator is installed so that the output shaft protrudes into the side protrusion frame. The method according to claim 1,
The drive actuator is a cylinder mechanism,
The electric module includes a rack gear formed on a piston rod of the driving actuator, and a pinion gear provided on a central axis of the rotating brush and meshed with the rack gear,
The driving actuator is a moisture or dust removal device for the wet cleaning unit, characterized in that it is installed in the wet cleaning unit so that the piston rod passes into the wet cleaning unit.

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