JP7185602B2 - Molten metal plating solution pumping device and pumping method - Google Patents

Description

The present invention relates to a molten metal plating solution pumping-out apparatus for pumping a plating solution from a plating pot and pouring it into another place for component adjustment and switching of the plating solution in hot-dip metal plating, and a melting using the apparatus. The present invention relates to a method for pumping out a metal plating solution.

One of the plating methods for metal plating such as zinc plating and zinc-aluminum alloy plating on a steel strip is a plating solution in which a desired metal is melted (also called plating bath or molten metal solution, hereinafter referred to as " There is a hot-dip metal plating method in which a steel strip is immersed in a plating solution.

As a plating apparatus for general hot-dip metal plating, there is a plating pot (also referred to as a plating tank or simply a pot, but hereinafter referred to as a "plating pot") for holding the plating solution. In , a sink roll is placed, the steel strip enters the plating solution from diagonally above, the steel strip is turned vertically by the sink roll, and is supported by a support roll placed below the surface of the plating solution above the sink roll. The plating solution is led upwards to produce a plated steel strip.

In the plating method using such a hot-dip metal plating solution, it is common to change the composition of the plating solution according to the type of plating, the type of steel strip to be coated, the purpose of use of the steel strip, etc. . Therefore, when finely adjusting the components of the plating solution, it is necessary to withdraw a small amount of the plating solution or replace it.

However, the conventional method of pumping out the plating solution to adjust the composition of the plating solution is to prepare a spare plating pot next to the plating pot, connect the plating pots with piping, and pump the plating solution. was common. For example, in Patent Documents 1 and 2, a preparation tank (or a sub-pot) separate from the plating pot is provided in order to adjust or change the components of the plating solution. Disclosed is a method for causing

Another method of pumping out the plating solution is to prepare a bucket (container) for pumping out the plating solution, put the bucket in the plating pot to scoop out the plating solution, move it and pour it to another storage place. I know how to put it in.

Japanese Patent Application Laid-Open No. 2002-206154 JP-A-3-120345

However, the methods disclosed in the aforementioned Patent Document 1 or Patent Document 2 require large-scale installation of piping and pumps, and the work of inflowing and outflowing the plating solution and the preparation work itself are time-consuming and laborious. In addition, the piping and pump equipment must be heated and insulated, which entails equipment-related risks such as failure and damage to these equipment, as well as work safety risks. In the case of large-scale plating solution replacement work, for example, when removing the entire amount of plating solution for repair work of a plating tank, even if it is a large-scale facility, the removal work itself is inefficient. However, in the case of pumping out a small amount of plating solution for fine adjustment of components, transfer work by piping is inefficient and inefficient.

Further, in the above-described method of pumping out the plating solution using the bucket, there is a problem that it is difficult to finely adjust the amount of the plating solution when pumping and pouring out the plating solution. For example, when pouring out a large amount of plating solution from the bucket at once, it is difficult to adjust the amount of solution poured out. There was a problem that it was difficult to adjust the amount.

In order to solve the above-described problems, the present inventors diligently studied a plating solution pumping-out apparatus and method thereof. As a result, a small bath containing the plating solution was used, and the bath was immersed in the plating pot. At that time, the plating solution was allowed to flow in from the bottom of the bath. Then I realized that it would be more efficient to lift the bath containing the plating solution and transport it to another location. Based on this knowledge, the present inventors have completed the present invention through further studies.

That is, the gist of the present invention is as follows.
(1) A hot-dip metal plating solution pumping device for pumping a plating solution from a plating pot and pouring it to another place,
The pumping-out device comprises a bath for pumping out the plating solution and a bath-tub hanger which is fixed to the upper part of the bath and holds the bath in a fixed manner,
The bath has an opening at the bottom and an overflow detection means for the plating solution at the top,
The bathtub hanger comprises a hanging piece that is lifted by a crane, a rod that reaches the opening of the bathtub, and a rod driving means that drives the rod up and down,
The rod has a plug that opens and closes the opening at the lower tip,
An apparatus for pumping out a molten metal plating solution, characterized by:
(2) The apparatus for pumping out a molten metal plating solution according to (1), wherein the overflow detecting means is a plurality of holes provided in the upper part of the side plate of the bath.
(3) In (1) or (2), the rod driving means is an air cylinder.
(4) A method of pumping out a molten metal plating solution by pumping out a plating solution from a plating pot using the device for pumping out a molten metal plating solution according to any one of (1) to (3) and pouring it into another place. There is
a moving step of lifting the pumping-out device by a crane and moving it to a position above the plating pot;
a plating solution inflow step of lowering the crane to submerge the bath into the plating pot with the opening at the bottom of the pumping-out device open, and causing the plating solution to flow into the pumping-out device through the opening;
an inflow stopping step of stopping the descent of the pumping-out device in the plating solution inflow step, driving the rod downward to close the opening with the plug, and stopping the inflow of the plating solution;
a retraction step of lifting the pumping device with the opening closed and retracting the pumping device to a position above the plating pot;
After moving the pumping device from the upper position of the plating pot to another location, the rod is driven upward to remove the plug from the opening, allowing the plating solution to flow out from the opening to the other location. A plating solution outflow step of pouring into
A method for pumping out a molten metal plating solution, comprising:
(5) The method for pumping out a molten metal plating solution according to (4), further comprising a plating solution overflow detection step between the plating solution inflow step and the inflow stop step.
(6) In (5), the overflow detection step is a step of monitoring overflow of the plating solution that has flowed into the bath from a plurality of holes provided in the upper part of the side plate of the bath. A method for pumping out a metal plating solution.
(7) In any one of items (4) to (6), the method of driving the rod downward in the inflow stop step is a method of pushing down the rod using an air cylinder. A method for pumping out a metal plating solution.

According to the present invention, the pumping work can be carried out efficiently, and the work of adjusting the minute components of the plating solution can be facilitated. As a result, it is possible to provide a pumping-out device and a pumping-out method that are suitable for replacing the plating solution, especially in small-scale plating equipment, which eliminates the need for large-scale equipment, improves work efficiency, and improves safety. can.

It is an appearance perspective view showing one embodiment of a pumping-out device of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a front view (sectional view) which shows one Embodiment of the pumping-out apparatus of this invention. FIG. 11 is an illustration showing one embodiment of a plug at the tip of the rod; FIG. 4 is an explanatory diagram showing one embodiment of a rod driving state; BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows typically the outline of the work process which shows one Embodiment of the pumping-out method of this invention.

An embodiment of the pumping device of the present invention will be described below with reference to FIGS. 1 and 2. FIG.

The pumping-out apparatus 1 of the present invention comprises a bathtub 3 for pumping out and storing the plating solution 2, and a bathtub hanger 4 which is fixed to the upper part of the bathtub 3 and holds the bathtub 3 in a fixed manner.

First, the bath 3 is not particularly limited as long as it has a shape that allows it to be submerged in the plating pot 12 used for actual operation, but one embodiment will be described below. The bath 3 is a box-shaped container for inflowing and storing the plating solution 2. Its structure is a cubic container composed of a bottom plate 3a, a top plate 3b, and four side plates 3c. It has a manufactured structure. A heat-resistant material that can withstand about 600° C., which is the state in which molten metal (for example, molten zinc) is melted, is suitable for the material, and for example, SUS316 made of stainless steel is preferable. The internal dimensions of the bathtub 3 are preferably, for example, a cube with one side of 50 to 70 cm. When molten metal flows into the bathtub 3, the suspended weight will be 0.7 to 1.2 tons, so the welding strength must be sufficient to withstand such a weight. For example, it is preferable to appropriately arrange reinforcing members such as reinforcing ribs, appropriately prepare grooves at the welding points, and provide scallops (notches) so that there is no cross in the weld line. Furthermore, it is preferable to apply a release agent to the outer wall of the bath 3 so that the plating solution 2 is less likely to adhere. Release agents include ceramic-based release agents and the like.

An opening 5 is provided in the center of the bottom plate 3 a of the bathtub 3 . The opening 5 serves as a spout (also referred to as a sprue) through which the plating solution 2 flows in and out. The shape of the opening 5 is not particularly limited, but a circular shape is preferable. The diameter of the circle is preferably 60 to 90 mm in inner diameter, but the diameter is not fixed, and by changing the diameter, the inflow and outflow of the plating solution can be adjusted. The opening 5 can be formed by making an appropriate hole in the center of the bottom plate 3a of the bathtub 3 and installing a cylindrical fitting member in the hole. If a cylindrical fitting member with a different inner diameter is prepared as appropriate, it will have an inner diameter suitable for the shape of the outflow destination when the shape and structure of the outflow destination of the plating solution 2, that is, the container to be poured out, is different. By replacing with the fitting member, the outflow amount from the bathtub 3 can be changed, and the outflow operation suitable for the shape of the outflow destination can be efficiently performed.

Next, in the upper portion of the side plate 3c of the bath 3, a plurality of overflow holes 6, which are an embodiment of means for detecting overflow of the plating solution 2, are provided at a constant height level. As the bath 3 is lowered into the plating solution 2 and immersed therein, the plating solution 2 flows from the opening 5 and the bath 3 is filled with the plating solution 2 . Since the plating solution 2 overflows from the overflow hole 6 before the plating solution 2 reaches the top plate 3b of the bath 3, the plating solution 2 functions as a detection means to prevent the plating solution 2 from overflowing from the bath 3. I am in charge. The structure of the overflow hole 6 is provided in the upper part of the side plate 3c of the bathtub 3. For example, at a position 60 to 70 mm below the top plate 3b of the bathtub 3, there are 4 circular holes with an inner diameter of 40 to 60 mmφ per side. They are provided at regular intervals. The shape and number of holes are not particularly limited, and are appropriately determined according to the shape and structure of the bathtub 3 .

Furthermore, the means for detecting overflow is not limited to the above-described overflow hole 6. For example, means for observing, measuring, or detecting the surface of the plating solution 2 flowing therein may be used. Means using an optical sensor, a load sensor, a temperature sensor, a position sensor, etc. provided inside or outside can be mentioned.

A bathtub hanger 4 for lifting and holding the bathtub 3 is placed on the upper part of the bathtub 3 . Since the bathtub hanger 4 is fixed to the bathtub 3, it can move together with the bathtub 3, that is, as the pumping device 1. - 特許庁The structure and material of the bathtub hanger 4 are not particularly limited as long as it is fixed to the bathtub 3 and can hold the bathtub 3 . In one embodiment, the frame 4c is a steel frame assembled using a general steel material such as rolled steel SS400, and has a structure manufactured by welding. The bathtub hanger 4 is manufactured by attaching the bottom plate 4a to the lower side of the frame 4c and the top plate 4b to the upper side by welding. The material of the bottom plate 4a and the top plate 4b is preferably the same as that of the frame 4c. By fixing the bottom plate 4a of the bathtub hanger 4 and the top plate 3b of the bathtub 3, the pumping-out device 1 has an integrated structure. As a fixing method, a method by bolting is preferable. Since the total weight of the plating solution 2 and the bathtub 3 (approximately 2 tons) is applied to the bathtub hanger 4, the welding work is performed by appropriately preparing a groove, etc., in the same manner as the bathtub 3, to ensure sufficient weld joint strength. need to keep.

A hanging piece 7 for hanging with a crane is provided on the top plate 4b of the bathtub hanger 4. - 特許庁As one embodiment of the suspension piece 7, suspension seats 7a are provided at four positions 60 to 80 mm inside from the four corners of the top plate 4b, and donut-shaped jigs for hooking crane hooks are fixed thereon. It has a set configuration.

Further, guides 8a and 8b are provided at the center of the bottom plate 4a and the top plate 4b of the bathtub hanger 4 for passing a rod-shaped rod 8 reaching the opening 5 of the bathtub 3. As shown in FIG. The guide 8a has a cylindrical shape in which a hole having a diameter larger than the outer diameter of the rod 8 is provided in the center of the bottom plate 4a of the bathtub hanger 4, and the rod 8 is placed in the hole so that the rod 8 can move freely up and down. It is a guide jig for The guide 8b is a guide jig placed in a hole provided in the center of the top plate 4b of the bathtub hanger 4, like the guide 8a. The rod 8 is a straight bar extending from the guide 8b to the guide 8a and reaching the opening 5 at the bottom of the bathtub 3. At least the portion to be immersed in the plating solution 2 is made of heat-resistant material such as SUS316. It is preferable to use the material of

A plug 10 for opening and closing the opening 5 is provided at the lower tip of the rod 8 . Like the rod 8, the material of the plug 10 is a heat-resistant material. One embodiment of plug 10 is shown in FIG. The shape of the plug 10 is not particularly limited, but a tapered inverted conical shape whose outer diameter tapers toward the bottom is used so that the circular opening 5 can be gradually closed. preferable.

Further, the bathtub hanger 4 is provided with rod driving means for driving the rod 8 up and down. The rod driving means is not particularly limited as long as it is a mechanism capable of driving the rod 8 in the vertical direction. In addition to the air cylinder using air pressure, there is no particular limitation as long as the rod 8 can be driven by a hydraulic system or a manual drive system.

FIG. 4 shows one embodiment of the driving state of the rod 8. As shown in FIG. The air cylinder 9 is installed on the frame 4c of the bathtub hanger 4, and pushes out the piston rod 9a with air pressure. A piston rod receiver 9b attached to the rod 8 is provided below the downward piston rod 9a, and the piston rod receiver 9b and the tip portion of the piston rod 9a are fixed. Therefore, when the piston rod 9a of the air cylinder 9 is extended, the piston rod receiver 9b fixed to the tip of the piston rod 9a is pushed down, and the rod 8 as a whole moves downward. As the rod 8 descends, the plug 10 at the bottom tip of the rod 8 gradually closes the opening 5 of the bathtub 3, and finally the opening 5 can be closed. When opening the opening 5, the piston rod 9a of the air cylinder 9 is contracted to raise the rod 8 together with the piston rod receiver 9b fixed to the piston rod 9a, thereby opening the opening 5 and removing the plating in the bathtub 3. Liquid 2 can flow out.

Next, with regard to the embodiment of the pumping method of the present invention, the details of each step will be described with reference to FIG. 5 which shows the steps of the pumping method.

The first step is the movement step of FIG. 5(A). By means of a crane, an overhead crane 11, which is one embodiment in FIG.

Next, in the plating solution inflow process of FIG. 5(B), first, with the opening 5 at the bottom of the bathtub 3 opened, that is, with the plug 10 at the tip of the rod 8 removed from the opening 5, the crane 11 The pumping device 1 is lowered. As the pumping device 1 is submerged in the plating pot 12 , the plating solution 2 flows into the bath 3 through the opening 5 .

Subsequently, in the inflow stop step of FIG. 5C, the bath 3 stops descending while the bath 3 is being filled with the plating solution 2 in the previous plating solution inflow step. At that time, an air cylinder 9, which is an embodiment of the rod driving means provided in the bathtub hanger 4, is used to drive the rod 8 downward so that the plug 10 at the lower end of the rod 8 closes the opening 5. , to stop the flow of the plating solution 2 into the bath 3 .

It is preferable to stop the inflow of the plating solution 2 while detecting the overflow state of the plating solution 2 by overflow detection means provided in the bath 3 . As one embodiment of the overflow detection process (overflow detection process), a method using the overflow hole 6 will be described. Since a plurality of overflow holes 6 are provided at a constant height level in the upper position of the side plate 3c of the bath 3, when the bath 3 is descended into the plating solution 2, the plating solution 2 is pushed onto the top plate of the bath 3. It overflows from the overflow hole 6 before reaching 3b. By monitoring the state of overflow from the overflow hole 6, the opening 5 can be closed to stop the inflow of the plating solution 2 at an appropriate timing, for example, at the time of overflow. The flow of the plating solution 2 may be stopped at an appropriate time before the overflow is detected without providing the overflow detection step. In that case, the timing of stopping may be set individually according to the purpose and situation of pumping out the plating solution.

5D, the drawing device 1 is lifted by the crane 11 with the opening 5 closed, and the drawing device 1 is withdrawn from the plating pot 12. As shown in FIG. In the subsequent plating solution outflow process (not shown in FIG. 5), the pumping device 1 is moved to a position above another location (outflow destination), and when it reaches above the outflow destination, the piston of the air cylinder 9 By retracting the rod 9a and driving the rod 8 upward, the plug 10 is removed from the opening 5, and the plating solution 2 is allowed to flow out to the outflow destination.

The advantages of the pumping-out apparatus and the pumping-out method of the present invention are, as described above, that the preparation (set-up) work for adjusting the components of the plating solution is simple, a bath for pumping out the plating solution is prepared, All that is left to do is to use a crane to pump out the plating solution, and then use a crane to load ingots of the specific metal (or alloy) required for component adjustment, making it easy to adjust the composition of the plating solution. There is something we can do.

In addition, the plating pot is usually provided with two to four inductor devices, but the life of the inductor device is about 1 to 10 years, and replacement work for the inductor device is regularly required. When the plating solution is put into the plating pot after replacing the consumable inductor device, in the conventional technology, the plating solution is put in using a pump and piping. However, when the pump is damaged and the plating solution cannot be supplied by the pump, by using the pumping-out apparatus of the present invention as an alternative method, the pump can be replaced without repairing or replacing the pump. There is the advantage that the pumping device of the invention can be used for backup purposes.

Further, another advantage of the pumping device of the present invention is that the opening 5 of the bathtub 3 allows fine adjustment of the flow rate. As explained in the above-mentioned problems to be solved by the invention, in the method of pumping out the plating solution using a bucket, a large amount of plating solution may be poured at once when pouring out from the bucket. Since it is difficult to adjust the amount to be poured out, it was difficult to adjust the amount when pouring into a small plating pot or directly to a piping port. However, in the pumping-out device of the present invention, it is possible to adjust the amount of water to be poured out simply by changing the diameter of the opening 5 of the bathtub 3, and it has an excellent effect that even a small amount can be easily carried out. be. For example, in the above-mentioned inductor device replacement work, it is desirable to adjust the preparatory work (test run) for operating the inductor device after replacement for each inductor device. Preparatory work must be done by pouring the plating solution only on the part. Therefore, in such a case, it is necessary to connect a pipe to the inductor device and pour a small amount of the plating solution directly into the pipe port connected to the inductor device. is very easy to perform and has excellent effects. By changing the diameter of the opening of the pumping device of the present invention, the outflow rate can be easily adjusted. Further, by changing the volume of the bathtub portion of the pumping device, the overall outflow rate can be increased. can also be adjusted.

The present invention will be further described below based on examples.

Using the pumping apparatus 1 according to the present invention shown in FIGS. 1 and 2, a molten Al--Zn alloy plating solution having an Al concentration of 54 wt% and a Zn concentration of 46 wt% is prepared into a molten Al--Zn alloy plating solution having an Al concentration of 55 wt% and a Zn concentration of 45 wt%. Work was performed to adjust the components of the Zn alloy plating solution. (Hereinafter, % notation means wt%.)
As the bathtub 3 of the pumping-out device 1, a box-shaped container with a length of 60 cm and a height of 50 cm was prepared. The internal volume is about 0.17 m ³ , and when the plating solution is almost completely filled, the weight is about 620 kg when the specific gravity of the plating solution is converted to 3700 kg/m ³ .

This pumping-out device 1 was lifted by an overhead crane 11 and moved to a position near the center of a plating pot 12 (capacity: 100 tons) containing the plating solution of Al 54%-Zn 46%. Subsequently, the pumping device 1 was lowered by the crane 11 and immersed in the plating solution 2 . At this point, since the opening 5 at the bottom of the bath 3 is open, the plating solution 2 flows into the bath 3 . The bath 3 is filled with the plating solution 2, and four circular holes with an inner diameter of 50 mm are formed at a certain position above the bath 3 (at a position about 65 mm below the top plate 3b of the bath 3) at equal intervals. ), the piston rod 9a of the air cylinder 9, which is rod driving means, is moved downward to move the rod 8 provided in the bathtub hanger 4 at the timing when the plating solution 2 overflows from the overflow hole 6 provided in the It was pushed down to close the opening 5 and stop the inflow of the plating solution 2 . In this state, the pumping device 1 is lifted by the crane 11, evacuated from the plating pot 12, and moved to another pot where the plating solution 2 pumped out by the crane 11 is stored. The rod 8 in 1 was removed from the opening 5, and the plating solution 2 in the bath 3 was poured out into another pot.

600 kg of the plating solution 2 was pumped out in one step, and 2.4 tons of the plating solution 2 was pumped out by repeating this series of steps four times. Therefore, the capacity of the plating solution (54% Al-46% Zn) of 100 tons at the beginning of the plating pot 12 is reduced by 2.4 tons, and the remaining capacity is 97.6 tons.

Subsequently, 1 ton of separately prepared Al ingots were charged twice into the plating pot 12 using a crane. As a result, the weight of Al is 97.6 t × 54% + 2 t = 54.7 t, and the weight of Zn is 97.6 t × 46% = 44.9 t. The concentration (weight ratio) is Al = 54.7 / (54.7 + 44.9) = 54.9%, Zn = 44.9 / (54.7 + 44.9) = 45.1%, Al 55% -The composition of the plating solution could be adjusted to 45% Zn.

In the above work, the time required for one process was 3 minutes, 4 repetitions required 12 minutes, and two ingot charging required 120 minutes, totaling about 135 minutes. .

When this component adjustment is carried out by the conventional method of transferring the plating solution by operating the pipes and pumps between the plating pot and the sub-pot, it takes only about 95 minutes to complete the transfer work. Preparation work for sub-pots, pipes, and pumps, as well as heating and keeping warm during transfer, takes time and effort as a pre-work setup, so it takes more than 6 hours to complete the overall adjustment. I needed it.

As described above, if the pumping device of the present invention is used, large-scale equipment is not required, the work time can be shortened, and the pumping work can be carried out safely. The pumping amount can be freely adjusted by changing the position of the overflow hole, etc., so it is very easy to adjust to the target composition in combination with the amount of input ingot, which is an excellent effect. It has

1 Pumping device 2 Plating solution 3 Bathtub 3a Bathtub bottom plate 3b Bathtub top plate 3c Bathtub side plate 4 Bathtub hanger 4a Bathtub hanger bottom plate 4b Bathtub hanger top plate 4c Bathtub hanger frame 5 Opening 6 Overflow hole 7 Hanging piece 7a Hanging seat 8 rods 8a, 8b guide 9 air cylinder 9a piston rod 9b piston rod receiver 10 plug 11 crane 12 plating pot

Claims (7)

A hot-dip metal plating solution pumping device for pumping a plating solution from a plating pot and pouring it elsewhere,
The pumping-out device comprises a bath for pumping out the plating solution and a bath-tub hanger which is fixed to the upper part of the bath and holds the bath in a fixed manner,
The bath has an opening at the bottom and an overflow detection means for the plating solution at the top,
The bathtub hanger comprises a hanging piece that is lifted by a crane, a rod that reaches the opening of the bathtub, and a rod driving means that drives the rod up and down,
The rod has a plug that opens and closes the opening at the lower tip,
An apparatus for pumping out a molten metal plating solution, characterized by: 2. An apparatus for pumping out a molten metal plating solution according to claim 1, wherein said overflow detection means is a plurality of holes provided in the upper part of the side plate of said bath. 3. An apparatus for pumping out a molten metal plating solution according to claim 1, wherein said rod driving means is an air cylinder. A method for pumping out a molten metal plating solution for pumping out a plating solution from a plating pot using the apparatus for pumping out a molten metal plating solution according to any one of claims 1 to 3 and pouring it into another place,
a moving step of lifting the pumping-out device by a crane and moving it to a position above the plating pot;
a plating solution inflow step of lowering the crane to submerge the bath into the plating pot with the opening at the bottom of the pumping-out device open, and causing the plating solution to flow into the pumping-out device through the opening;
an inflow stopping step of stopping the descent of the pumping-out device in the plating solution inflow step, driving the rod downward to close the opening with the plug, and stopping the inflow of the plating solution;
a retraction step of lifting the pumping device with the opening closed and retracting the pumping device to a position above the plating pot;
After moving the pumping device from the upper position of the plating pot to another location, the rod is driven upward to remove the plug from the opening, allowing the plating solution to flow out from the opening to the other location. A plating solution outflow step of pouring into
A method for pumping out a molten metal plating solution, comprising: 5. The method for pumping out a molten metal plating solution according to claim 4, further comprising a plating solution overflow detection step between said plating solution inflow step and said inflow stopping step. 6. The hot dip metal plating according to claim 5, wherein the overflow detection step is a step of monitoring overflow of the plating solution that has flowed into the bath from a plurality of holes provided in the upper part of the side plate of the bath. Liquid pumping method. The hot dip metal plating solution according to any one of claims 4 to 6, characterized in that, in the inflow stop step, the method of driving the rod downward is a method of pushing down the rod using an air cylinder. pumping method.

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