JP2016175051A - Pipe washing apparatus and pipe washing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To have an excellent washing effect by using no washing liquid of strong acidity.SOLUTION: A pipe washing apparatus 100 includes tanks 11 and 12 that store a washing liquid, a circulation pump 13 and a suction pump 14 for circulating the washing liquid stored in the tanks through a washing object pipe R (cooling pipe for a die cast mold), a compressor 15 that feeds compressed air into the washing liquid, an air mixer 17 that mixes the compressed air with the washing liquid, connection pipes 31 to 39 that return the washing liquid into the tank 11 from the tank 11 by way of the circulation pump 13 and the washing object pipe R, and an electrode part that keeps a contact with the washing liquid. The electrode part comprises a first electrode, a second electrode, and a ground electrode to decrease the oxidation reduction potential of the washing liquid, the first electrode and the second electrode being connected to an AC current generation part so that AC current may be impressed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pipe cleaning apparatus and a pipe cleaning method.

  When cooling water is circulated through a cooling pipe such as a die-casting die, scale and oil stains such as rust, calcium and magnesium adhere to the inner wall of the cooling pipe. If rust adheres to the inner wall of the cooling pipe, clean the inner wall of the cooling pipe using a pipe cleaning device. For example, the pipe cleaning apparatus circulates a cleaning liquid through a cooling pipe to clean the inner wall thereof.

  In order to improve the cleaning effect of the piping, various devices such as a piping cleaning device that circulates the cleaning liquid strengthened with flowing water with a powerful pump through the piping and cleans the inside of the piping, and a piping cleaning device that warms the cleaning liquid by installing a heater Pipe cleaning devices have been proposed.

  Further, the pipe cleaning device disclosed in Patent Document 1 changes the flow of the cleaning liquid to be circulated (to make the flow in a pulsating state) to enhance the cleaning effect. Moreover, in order to further improve the cleaning effect, a cleaning liquid containing a phosphoric acid-based rust remover is used.

JP 2004-298996 A

  However, even the pipe cleaning device of Patent Document 1 does not have a sufficient cleaning effect, and it is required to further improve the cleaning effect. Moreover, since the phosphoric acid type rust remover is strongly acidic, it is harmful to the human body and the like and needs to be handled with care. For this reason, there is a need for a pipe cleaning apparatus that can provide a high cleaning effect without using a strongly acidic cleaning liquid.

  Then, this invention is made | formed in view of the above situations, and it aims at providing the piping cleaning apparatus and piping cleaning method which have the outstanding washing | cleaning effect, without using a strong acidic washing | cleaning liquid.

In order to achieve the object of the present invention, a pipe cleaning apparatus according to the first aspect of the present invention comprises:
A tank for storing the cleaning liquid;
An electrode portion including a first electrode, a second electrode, and a ground electrode in contact with the cleaning liquid;
An alternating current generator for applying an alternating current between the first electrode and the second electrode;
A circulation pump for circulating the cleaning liquid through the pipe to be cleaned;
A connection pipe for returning the cleaning liquid from the tank to the tank via the circulation pump and the pipe to be cleaned;
It is characterized by providing.

  For example, the pipe cleaning apparatus may include an air mixing unit that feeds compressed air into the cleaning liquid and includes air bubbles.

  For example, the pipe cleaning device is configured to circulate the cleaning liquid in a forward direction from one end to the other end of the pipe to be cleaned and to circulate the cleaning liquid in a reverse direction from the other end to the one end of the pipe to be cleaned. You may carry out alternately.

Furthermore, in order to achieve the object of the present invention, a pipe cleaning method according to the second aspect of the present invention includes:
Disposing the first electrode, the second electrode and the ground electrode so as to contact the cleaning liquid;
An alternating current application step of applying an alternating current between the first electrode and the second electrode;
A circulation step of circulating the cleaning liquid to the pipe to be cleaned;
Comprising
It is characterized by that.

  The pipe cleaning apparatus and pipe cleaning method of the present invention have an excellent cleaning effect without using a strongly acidic cleaning liquid.

It is a figure which shows the piping cleaning apparatus which concerns on embodiment of this invention. It is a figure which shows the tank of the piping cleaning apparatus which concerns on embodiment of this invention. It is a figure which shows the voltage which the alternating current generation part which concerns on embodiment of this invention generate | occur | produces. It is a figure which shows operation | movement of the piping washing apparatus which concerns on embodiment of this invention. It is a figure which shows operation | movement of the piping washing apparatus which concerns on embodiment of this invention. It is a figure which shows the flowchart of the piping washing process concerning embodiment of this invention. (A) is sectional drawing of piping at the time of circulating a washing | cleaning liquid to a piping in the forward direction and a reverse direction using the piping cleaning apparatus which concerns on embodiment of this invention, (B) It is sectional drawing of piping at the time of circulating a washing | cleaning liquid only to a direction.

  Hereinafter, a pipe cleaning apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

  The pipe cleaning device 100 according to the embodiment is for cleaning the inside of the pipe R to be cleaned by circulating the cleaning liquids WK and WA (cleaning liquid W) in the pipe R to be cleaned (the pipe for cooling the die casting mold). 1, tanks 11 and 12 for storing the cleaning liquid W, a circulation pump 13 and a suction pump 14 for circulating the cleaning liquid W stored in the tank to the pipe R to be cleaned, and compressed air to the cleaning liquid W , An air mixer 17 for mixing the compressed air and the cleaning liquid W, and connection pipes 31 to 39 for returning the cleaning liquid W from the tank 11 to the tank through the circulation pump 13 and the pipe R to be cleaned. As shown in FIG. 2, the tank 11 includes an electrode portion including a first electrode 42, a second electrode 43, and a ground electrode 44 in order to reduce the oxidation-reduction potential of the cleaning liquid W. The second electrode 43 is electrically connected to the alternating current generator 41.

  The tank 11 is a tank into which the acidic cleaning liquid WK is placed. One end of the connection pipe 31 is connected to the lower part of the tank, and the other end is connected to the circulation pump 13. The connection pipe 31 is a pipe for sending the cleaning liquid WK from the tank 11 to the circulation pump 13, and includes a valve 21 in the middle. The acidic cleaning liquid WA is a weakly acidic solution for cleaning the pipe R to be cleaned, and is not particularly limited as long as it can clean the pipe R to be cleaned, and is, for example, an aqueous solution containing citric acid.

  The tank 12 is a tank into which the alkaline cleaning liquid WA is placed. One end of the connection pipe 32 is connected to the lower part of the tank, and the other end is connected to the circulation pump 13. The connection pipe 32 is a pipe for feeding the cleaning liquid WA from the tank 12 to the circulation pump 13 and includes a valve 22 in the middle. The alkaline cleaning liquid WA is a weakly alkaline aqueous solution for neutralizing the pipe to be cleaned R after the pipe to be cleaned R is washed with the acidic cleaning liquid WK, and is, for example, an aqueous sodium hydrogen carbonate solution.

  The circulation pump 13 is a pump that sends the cleaning liquid W from the tank 11 or 12 to the pipe R to be cleaned. One end of the connection pipe 33 is connected to the circulation pump 13, and the other end is connected to the air mixer 17. The connection pipe 33 is a pipe for sending the cleaning liquid W from the circulation pump 13 to the air mixer 17 and includes a valve 23 in the middle.

  The air mixer 17 is a device that mixes the cleaning liquid W sent from the tank 21 or 22 and the compressed air sent from the compressor 15 and includes air bubbles in the cleaning liquid W. The air mixer 17 is connected to the compressor 15 via a connection pipe 34. The connection pipe 34 is a pipe that sends compressed air from the compressor 15 to the air mixer 17, and includes a check valve 16 so that the cleaning liquid W does not flow into the compressor 15 from the air mixer 17.

  The connection pipe 35 is a pipe for sending the cleaning liquid W from the air mixer 17 to the first coupler 18. One end of the connection pipe 35 is connected to the air mixer 17 and the other end is connected to the first coupler 18. ing. The first coupler 18 is an instrument that connects the connection pipe 35 to one end of the pipe R to be cleaned.

  The connection pipe 36 is a pipe for sending the cleaning liquid W from the second coupler 19 to the suction pump 14. One end of the connection pipe 36 is connected to the second coupler 19 and the other end is connected to the suction pump 14. . The second coupler 19 is an instrument that connects the connection pipe 36 to the other end of the pipe R to be cleaned.

  The connection pipe 37 is a pipe for sending the cleaning liquid W from the air mixer 17 to the second coupler 19, one end is connected between the air mixer 17 of the connection pipe 35 and the valve 24, and the other end is a connection pipe. 36 is connected between the second coupler 19 and the valve 25, and the valve 26 is provided on the way.

  The connection pipe 38 is a pipe that sends the cleaning liquid W from the first coupler 18 to the suction pump 14. One end of the connection pipe 38 is connected between the first coupler 18 of the pipe 35 and the valve 24, and the other end of the connection pipe 36. It is connected between the valve 25 and the suction pump 14 and includes a valve 27 in the middle.

  The connection pipe 39a is a pipe for sending the cleaning liquid W from the suction pump 14 to the tank 11. One end is connected to the suction pump 14, the other end is inserted from the upper opening of the tank 11, and the valve 28 is provided in the middle. . The connection pipe 39b is a pipe for sending the cleaning liquid W from the suction pump 14 to the tank 12, and one end is connected to the suction pump 14, the other end is inserted from the upper opening of the tank 12, and the valve 29 is provided in the middle. .

  The electrode portion including the first electrode 42, the second electrode 43, and the ground electrode 44 shown in FIG. 2 is an electrode used for lowering the oxidation-reduction potential of the cleaning liquid W. The first electrode 42, the second electrode 43, and the ground electrode 44 are electrodes in which platinum is plated on titanium, and are provided below the water surface of the cleaning liquid W in the tank 11. The first electrode 42 and the second electrode 43 are electrically connected to the alternating current generator 41 so that an alternating current flows between the first electrode 42 and the second electrode 43. The alternating current generator 41 generates a sawtooth wave alternating current and applies the alternating current between the first electrode 42 and the second electrode 43. The ground electrode 44 is an electrode that is electrically grounded. The ground electrode 44 is connected to the ground with an electric wire, and a switch 45 is provided in the middle of the electric wire.

  Next, the operation of the pipe cleaning apparatus 100 configured as described above will be described. First, an operation for lowering the oxidation-reduction potential of the cleaning liquid W will be described. The alternating current generator 41 applies a sawtooth wave alternating voltage shown in FIG. 3 having a voltage of 10 V to 50 V and a frequency of 30 kHz to 50 kHz between the first electrode 42 and the second electrode 43. The switch 45 is turned on and the ground electrode 44 is grounded.

  As described above, when an AC voltage is applied to the first electrode 42 and the second electrode 43, a DC current is alternately transferred from the first electrode 42 to the ground electrode 44 and from the second electrode 43 to the ground electrode 44. Flowing. As a result, the oxidation-reduction potential of the cleaning liquid W in the tank 11 decreases, the surface tension of the cleaning liquid W decreases, and the permeability increases. As the permeability of the cleaning liquid W increases, the cleaning power of the cleaning liquid W increases. Details of the oxidation-reduction potential of the cleaning liquid W are described in JP-A-5-228475.

  Next, a case where the acidic cleaning liquid WK is circulated from one end of the pipe to be cleaned R to the other end for cleaning will be described with reference to FIG. The direction flowing from one end to the other is the forward direction.

  The valve 21 is opened so that the acidic cleaning liquid WK contained in the tank 11 can be sent to the pump. The valve 23 is opened so that the cleaning liquid WK can be sent from the circulation pump 13 to the air mixer 17. The valves 24 and 25 are opened so that the cleaning liquid WK is circulated from one end of the pipe to be cleaned R to the other end. The valve 28 is opened so that the cleaning liquid WK can be sent from the suction pump 14 to the tank 11. The other valves 22, 26, 27 and 29 are closed.

  When the circulation pump 13 and the suction pump 14 are operated in this state, the cleaning liquid WK flows from the tank 11 to the circulation pump 13 as indicated by an arrow. The cleaning liquid WK flowing to the circulation pump 13 is sent out from the circulation pump 13 to the air mixer 17. When the compressor 15 is operated, compressed air is sent into the air mixer 17 and air bubbles are included in the cleaning liquid WK. The cleaning liquid WK containing air bubbles is sent from the air mixer 17 to the pipe R to be cleaned through the first coupler 18. The cleaning liquid WK sent to the pipe to be cleaned R circulates while cleaning the pipe to be cleaned R, and is sent from the pipe to be cleaned R to the second coupler 19. The cleaning liquid WK sent to the second coupler 19 is sucked by the suction pump 14 and returned to the tank 11. Further, when the cleaning liquid WK in the pipe R to be cleaned is neutralized with the alkaline cleaning liquid WA, the valves 21 and 28 are closed and the valves 22 and 29 are opened from the state in which the cleaning liquid WK is circulated in the forward direction.

  Next, the case where the acidic cleaning liquid WK is circulated from one end to the other end of the pipe R to be cleaned for cleaning will be described with reference to FIG. The direction flowing from the other end to the one end is the reverse direction.

  The valve 21 is opened so that the acidic cleaning liquid WK contained in the tank 11 flows to the pump. The valve 23 is opened so that the cleaning liquid WK flows from the circulation pump 13 to the air mixer 17. The valves 26 and 27 are opened so that the cleaning liquid WK is circulated from the other end of the pipe R to be cleaned to one end. The valve 28 is opened so that the cleaning liquid WK flows from the suction pump 14 into the tank 11. The other valves 22, 24, 25 and 29 are closed.

  When the circulation pump 13 and the pump 14 are operated in this state, the cleaning liquid WK flows from the tank 11 to the circulation pump 13 as indicated by an arrow. The cleaning liquid WK flowing to the circulation pump 13 is sent out from the circulation pump 13 to the air mixer 17. When the compressor 15 is operated, the compressed air is sent to the air mixer 17 and the compressed air is contained in the cleaning liquid WK. The cleaning liquid WK containing compressed air is sent from the air mixer 17 to the other end of the pipe R to be cleaned through the second coupler 19. The cleaning liquid WK sent to the other end of the pipe to be cleaned R passes through the pipe to be cleaned R, and is sent from one end of the pipe to be cleaned R to the first coupler 18. The cleaning liquid WK sent to the first coupler 18 is sucked by the suction pump 14 and returned to the tank 11.

  Next, a pipe cleaning process for cleaning the pipe R to be cleaned using the pipe cleaning apparatus 100 configured as described above will be described with reference to FIG.

  First, the first coupler 18 is connected to one end of the pipe R to be cleaned, and the second coupler 19 is connected to the other end of the pipe R to be cleaned. Next, the pipe cleaning apparatus 100 starts an operation for lowering the oxidation-reduction potential (step S101). The switch 45 is turned on, the ground electrode 44 is grounded, and the alternating current generator 41 is a sawtooth having a voltage between 10 V and 50 V and a frequency between 30 kHz and 50 kHz between the first electrode 42 and the second electrode 43. Apply an AC voltage in the shape of a wave. Thereby, the oxidation-reduction potential of the cleaning liquid WK decreases, and the cleaning effect of the cleaning liquid WK is improved.

  Next, the cleaning liquid WK is circulated in the forward direction (step S102). The valves 21, 23, 24, 25, and 28 are opened and the valves 22, 27, 26, and 29 are closed so that the cleaning liquid WK circulates in the forward direction. When the circulation pump 13 and the suction pump 14 are operated in this state, the cleaning liquid WK flows in the forward direction through the pipe R to be cleaned as shown in FIG. Next, the compressor 15 is operated, compressed air is sent to the air mixer 17, and air bubbles are included in the cleaning liquid WK. When air bubbles are contained in the cleaning liquid WK, a water hammer action is caused in the pipe R to be cleaned, and the scale S and the like adhering to the inner peripheral surface of the pipe R to be cleaned is efficiently removed.

  Next, the cleaning liquid WK is circulated in the reverse direction (step S103). When the valves 24 and 25 are closed and the valves 26 and 27 are opened so as to circulate the cleaning liquid WK in the reverse direction, the cleaning liquid WK circulates in the reverse direction in the pipe R to be cleaned as shown in FIG. When the cleaning liquid WK is circulated in the reverse direction, an air valve is included in the cleaning liquid WK as in the case of circulating in the forward direction. Next, after a predetermined time has elapsed, it is determined whether step S102 and step S103 have been executed a predetermined number of times (step S104). If the predetermined number of times has not been executed (step S104; No), the process returns to step S102 and the cleaning liquid WK is circulated in the forward direction again. In this way, step S102 and step S103 are repeated until a predetermined number of times are executed.

  By circulating the cleaning liquid WK in the forward direction and the reverse direction, as shown in FIG. 7A, the scale S is effectively removed even if there is a bent portion in the pipe R to be cleaned. On the other hand, when the cleaning liquid is circulated only in the forward direction, if there is a bent portion of the pipe R to be cleaned as shown in FIG. 7B, the scale S remains without being removed at a place where the flow of the cleaning liquid W is stagnant. . By alternately circulating the cleaning liquid WK through the pipe R to be cleaned in the forward direction and the reverse direction, the scale S that is not cleaned when the cleaning liquid WK is circulated only in the forward direction or only in the reverse direction is effectively removed. Can do.

  Returning to FIG. 6, when step S102 and step S103 are executed a predetermined number of times (step S104; Yes), the compressor 15 is stopped and the cleaning with the acidic cleaning liquid WK is terminated.

  After completion of cleaning of the pipe R to be cleaned with the acidic cleaning liquid WK, the operation for lowering the oxidation-reduction potential is stopped (step S105). Next, the alkaline cleaning liquid WA is circulated in the forward direction (step S106). Specifically, the valves 21, 26, 27 and 28 are closed, the valves 22, 23, 24, 25 and 29 are opened, and the cleaning liquid WA is circulated. Next, the alkaline cleaning liquid WA is circulated in the reverse direction (step S107). Specifically, the valves 21, 24, 25 and 28 are closed, and the valves 22, 23, 26, 27 and 29 are opened to circulate the cleaning liquid WA. In this way, when the alkaline cleaning liquid WA is circulated in the forward direction and the reverse direction, the cleaning liquid WK remaining in the pipe R to be cleaned is neutralized.

  Next, it is determined whether step S106 and step S107 have been executed a predetermined number of times (step S108). If the predetermined number of times has not been executed (step S108; No), the process returns to step S106, and the cleaning liquid WA is circulated in the forward direction again. In this way, step S106 and step 107 are repeated until a predetermined number of times are executed.

  After step S106 and step S107 are executed a predetermined number of times (step S108; Yes), the cleaning liquid W in the pipe is removed with compressed air (step S109). In order to remove the cleaning liquid W in the pipe R to be cleaned with compressed air, the circulation pump 13 and the suction pump 14 are stopped, and the valves 22 and 23 are closed. When the compressor is operated in this state, compressed air is sent into the pipe R to be cleaned. At this time, the suction pump 14 may be operated. The cleaning liquid W passes through the connection pipe by compressed air from the pipe R to be cleaned and is pushed out to the tank 12 so that the cleaning liquid W can be removed from the pipe R to be cleaned. When removal of the cleaning liquid W is completed with compressed air, the pipe cleaning process ends.

  The pipe cleaning device 100 lowers the oxidation-reduction potential of the cleaning liquid W and decreases the surface tension of the cleaning liquid W. When the surface tension of the cleaning liquid W decreases, the permeability increases and the cleaning power of the cleaning liquid W increases. The air mixer 17 has a function of sending compressed air into the cleaning liquid W and including air bubbles in the cleaning liquid W. When air bubbles are contained in the cleaning liquid W, a water hammer action is caused in the pipe R to be cleaned, and the scale S and the like adhering to the inner peripheral surface of the pipe R to be cleaned is efficiently removed. The pipe cleaning device 100 has a function of circulating the cleaning liquid W through the pipe R to be cleaned in the forward direction and the reverse direction. This effectively removes dirt even if there is a bent portion in the pipe R to be cleaned. The pipe cleaning apparatus 100 has a function of cleaning the pipe R to be cleaned with the acidic cleaning liquid WK and then cleaning with the alkaline cleaning liquid WA. For this reason, since an acidic liquid does not remain in the to-be-cleaned pipe R after cleaning, it is difficult to rust.

  In the pipe cleaning apparatus 100 according to the present embodiment, the connection pipes 35 and 36 are connected to the pipe R to be cleaned using the first coupler 18 and the second coupler 19, but the first coupler 18 and the second coupler are connected. The connecting pipes 35 and 36 may be connected to the pipe R to be cleaned without using 19. For example, the flanges of the connection pipes 35 and 36 may be connected to the flange of the pipe R to be cleaned by screws.

  Moreover, although the air mixer 17 is mixing the compressed air sent from the compressor 15 with which the piping washing apparatus 100 is provided with the washing | cleaning liquid W, you may mix the compressed air supplied from the outside with the washing | cleaning liquid W. Further, a venturi tube may be used as the air mixer 17 without using compressed air.

  The pipe cleaning device 100 includes the suction pump 14, but may not include the suction pump 14. In this case, the circulation amount of the cleaning liquid W may be prevented from decreasing by increasing the capacity of the circulation pump 13 or the like.

  In addition, the pipe cleaning apparatus 100 may mix and discharge the acidic cleaning liquid WK and the alkaline cleaning liquid WA after completing the pipe cleaning process. By doing so, the cleaning liquid W can be neutralized and discharged.

  Various embodiments and modifications can be made to the present invention without departing from the broad spirit and scope of the present invention. The above-described embodiments are for explaining the present invention and do not limit the scope of the present invention.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

  An embodiment in which the cooling pipe (φ8 × 10 system) of the die casting die for manufacturing an automobile mission case is cleaned using the pipe cleaning apparatus 100 will be described.

  Using the pipe cleaning apparatus 100, the cooling pipe of the die casting mold was cleaned for 4 hours. As the cleaning liquid WK, 0.5% by mass of citric acid was used. The amount of compressed air introduced is 2.0 l / min. Moreover, the voltage of the alternating voltage applied to the 1st electrode and the 2nd electrode is 30V, and the frequency is 30 kHz.

  The total altitude and calcium hardness contained in the cleaning liquid WK, which is used to clean the cooling pipe of the die casting die using the pipe cleaning device 100, before cleaning, after cleaning for 1 hour, after cleaning for 2 hours, after cleaning for 3 hours, and after cleaning for 4 hours. The iron ion concentration and normal hexane concentration were measured. The results are shown in Table 1.

  As shown in Table 1, total hardness, calcium, iron, and normal hexane that were not contained before cleaning were detected in the cleaning liquid WK after cleaning. In these components, calcium, iron, and normal hexane adhering to the inner wall of the cooling pipe are eluted in the cleaning liquid WK. For this reason, it turns out that these components were removed from the inner wall of piping for cooling. The iron contained in the cleaning liquid WK after cleaning is one in which rust is eluted in the cleaning liquid WK. Further, the calcium contained in the cleaning liquid WK after cleaning is the calcium that is contained in the cooling water adheres to the inner wall of the cooling pipe, and the calcium is eluted in the cleaning liquid WK.

DESCRIPTION OF SYMBOLS 100 Piping washing apparatus 11, 12 Tank 13 Circulation pump 14 Suction pump 15 Compressor 16 Check valve 17 Air mixer 18 1st coupler 19 2nd coupler 21-29 Valves 31-38, 39a, 39b Connection piping 41 AC current generation part 42 1st electrode 43 2nd electrode 44 Ground electrode 45 Switch

Claims (4)

A tank for storing the cleaning liquid;
An electrode portion including a first electrode, a second electrode, and a ground electrode in contact with the cleaning liquid;
An alternating current generator for applying an alternating current between the first electrode and the second electrode;
A circulation pump for circulating the cleaning liquid through the pipe to be cleaned;
A connection pipe for returning the cleaning liquid from the tank to the tank via the circulation pump and the pipe to be cleaned;
A pipe cleaning apparatus comprising: An air mixing section for sending compressed air into the cleaning liquid and including air bubbles;
The pipe cleaning apparatus according to claim 1, wherein the pipe cleaning apparatus is provided. The forward circulation of the cleaning liquid from one end to the other end of the pipe to be cleaned and the reverse circulation of the cleaning liquid from the other end to the one end of the pipe to be cleaned are alternately performed.
The pipe cleaning apparatus according to claim 1 or 2, wherein Disposing the first electrode, the second electrode and the ground electrode so as to contact the cleaning liquid;
An alternating current application step of applying an alternating current between the first electrode and the second electrode;
A circulation step of circulating the cleaning liquid to the pipe to be cleaned;
Comprising
A piping cleaning method characterized by that.

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