Square billet continuous casting secondary spray cooling method and device

Abstract

According to the square billet continuous casting secondary spray cooling method and device, for cooling subareas of one or more arc-shaped sections, in the same cooling subarea, only the spray water amount of the inner arc side of a casting billet can be independently adjusted, and the spray water amount of the inner arc side of the casting billet can be adjusted by adjusting the spray water amount of the inner arc side of the casting billet; the spraying water quantity on the inner arc side of the casting blank is smaller than that on the outer arc side, the left side and the right side of the casting blank. The four faces of the casting blank can be evenly cooled, the implementation cost is low, and the practicability is high.

Description

Technical Field

[0001] The invention belongs to the field of iron and steel metallurgy continuous casting, and in particular relates to a billet continuous casting secondary spray cooling method and device. Background Art

[0002] The continuous casting of square billets generally adopts a full-arc model, and its secondary spray cooling system generally has 4 to 5 cooling zones arranged in sequence. Among them, the first zone is the full roller section, which is located at the exit of the crystallizer, and the other zones are arc sections. Each cooling zone adopts a spraying method to cool the four sides of the billet. Since the cooling intensity requirements of each cooling zone are different, the spray water volume of each cooling zone is independently controlled. However, in each cooling zone, the spray water volume on the four sides of the billet is not independently controlled. Therefore, the spray water volume on the four sides of the billet in each cooling zone is basically the same.

[0003] Although the current secondary spray cooling system can quickly cool the ingot and prevent large bulging of the ingot during production, it cannot achieve uniform cooling of the four sides of the ingot. Therefore, the actual size of the ingot before entering the straightening machine will deviate greatly from the expected size, increasing the difficulty of subsequent straightening in the straightening machine. Summary of the invention

[0004] The purpose of the present invention is to provide a method for secondary spray cooling of continuous casting of square billets, and a device for secondary spray cooling of continuous casting of square billets. The present invention can achieve uniform cooling of four surfaces of the billet, with low cost and strong practicability.

[0005] The technical solution adopted by the present invention is: A method for secondary spray cooling of continuous casting of square billets, which independently adjusts the spray water volume of each cooling zone according to different cooling intensity requirements of each cooling zone; for one or more arc-shaped cooling zones, within the same cooling zone, only the spray water volume on the inner arc side of the billet can be adjusted independently, and by adjusting the spray water volume on the inner arc side of the billet, the spray water volume on the inner arc side of the billet is made smaller than the spray water volume on the outer arc side of the billet, the left side of the billet and the right side of the billet.

[0006] Preferably, the second partition is selected so that only the amount of spray water on the inner arc side of the ingot can be adjusted individually; or, the second and third partitions are selected so that only the amount of spray water on the inner arc side of the ingot can be adjusted individually.

[0007] Preferably, before the continuous casting starts, a test spray is carried out to observe whether the flow indication on the main pipeline of the cooling zone can reach the design value: if it can, it means that the spray water bars in the cooling zone are not blocked; if not, it means that the spray water bars in the cooling zone are blocked, and then the pressure indications on the branch pipelines of the spray water bars corresponding to the four sides of the ingot are further observed. If there is a branch pipeline with a relatively significantly high pressure indication, it is determined that the spray water bars on the branch pipeline are blocked; if the pressure indications on the four branch pipelines are not much different, it is determined that the spray water bars on the four branch pipelines are all blocked.

[0008] Preferably, after the continuous casting machine starts casting, when adjusting the amount of spray water on the inner arc side of the ingot, observe the pressure indications on the branch pipes of the spray water strips corresponding to the four sides of the ingot, and compare the difference between the pressure indications on the branch pipes of the spray water strips corresponding to the inner arc side of the ingot and the pressure indications on the branch pipes of the spray water strips corresponding to the other three sides of the ingot, and make the difference within a certain range through adjustment.

[0009] Preferably, after the continuous casting machine starts casting, the bulging of the left and right sides and the inner and outer arc surfaces of the ingot are measured offline. If the difference between the bulging amount of the left and right sides and the bulging amount of the inner and outer arc surfaces increases, the amount of water sprayed on the inner arc side of the ingot is further reduced until the difference between the bulging amount of the left and right sides and the bulging amount of the inner and outer arc surfaces is within a certain range.

[0010] A square billet continuous casting secondary spray cooling device comprises a plurality of cooling zones arranged in sequence, each cooling zone is equipped with a spray water strip for spray cooling the four sides of the billet, four branch pipes for supplying water to the spray water strips corresponding to the four sides of the billet, a main pipe for supplying water to the four branch pipes, and a main regulating valve arranged on the main pipe, wherein the main regulating valve is used to adjust the overall cooling intensity of the cooling zone; for one or more arc-shaped cooling zones, branch regulating valves are arranged on the branch pipes of the spray water strips corresponding to the inner arc side of the billet, and the branch regulating valves are used to adjust the spray water volume on the inner arc side of the billet, so that the spray water volume on the inner arc side of the billet in the same cooling zone is less than the spray water volume on the outer arc side of the billet, the left side of the billet and the right side of the billet.

[0011] Preferably, a sub-regulating valve is set on the sub-pipeline of the spray water strip corresponding to the inner arc side of the second partition casting billet; or, a sub-regulating valve is set on the sub-pipeline of the spray water strip corresponding to the inner arc side of the second and third partition casting billets.

[0012] Preferably, the main pipeline is also provided with a manual valve, a flow detection component and a pressure detection component, and each branch pipeline is also provided with a pressure detection component.

[0013] Preferably, the sub-regulating valves and pressure detection components on each sub-pipeline are arranged outside the secondary cooling chamber.

[0014] Preferably, the sub-regulating valve is remotely controlled or manually controlled on site.

[0015] The beneficial effects of the present invention are: In the cooling zone of the arc section, the length of the outer arc side of the billet is longer than that of the inner arc side (the thicker the billet, the more obvious it is). Therefore, the cooling area of ​​the inner arc side of the billet is the smallest, and due to gravity, the water sprayed on the inner arc side is easier to reach the surface of the billet and stay on the billet than the water sprayed on the other three sides (the wider the billet, the longer the stay time). Therefore, under the same amount of spray water, the cooling effect of the inner arc side of the billet is the best, and the cooling effects of the other three sides of the billet are almost the same. Furthermore, the present application allows the amount of spray water on the inner arc side of the billet to be independently adjustable and less than the amount of spray water on the other three sides of the billet, so that the cooling intensity of the inner arc side of the billet is equivalent to the cooling intensity of the outer arc side of the billet, the left side of the billet and the right side of the billet, thereby achieving uniform cooling of the four sides of the billet. In addition, the present invention hardly increases the configuration of the continuous casting machine (only needs to add a valve to the original pipeline), so as to achieve low cost, simple operation and strong practicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of a spray water circuit of a cooling zone with a sub-regulating valve in a secondary spray cooling device for continuous casting of a square billet according to an embodiment of the present invention.

[0017] Figure 2 It is a schematic diagram of the 2nd to 5th zones in the secondary spray cooling device for continuous casting of square billets according to an embodiment of the present invention. For ease of observation, only the spray water line of the 2nd zone is shown.

[0018] In the figure: 1-main pipeline; 2-branch pipeline; 3-main regulating valve; 4-branch regulating valve; 5-flow detection component; 6-pressure detection component; 7-manual valve; 8-casting billet; 9-second cooling chamber; 10-water distribution chamber. DETAILED DESCRIPTION

[0019] The present application is further described below in conjunction with the accompanying drawings and embodiments.

[0020] Embodiment 1 The present embodiment discloses a method for secondary spray cooling of continuous casting of square billets: the spray water volume of each cooling zone is independently adjusted according to different cooling intensity requirements of each cooling zone; for one or more arc-shaped cooling zones, within the same cooling zone, only the spray water volume on the inner arc side of the billet can be adjusted separately, and by adjusting the spray water volume on the inner arc side of the billet, the spray water volume on the inner arc side of the billet is made smaller than the spray water volume on the outer arc side of the billet, the left side of the billet and the right side of the billet. In the cooling zone of the arc section, the length of the outer arc side of the billet is longer than that of the inner arc side (the thicker the billet, the more obvious it is). Therefore, the cooling area of ​​the inner arc side of the billet is the smallest, and due to gravity, the water sprayed on the inner arc side is easier to reach the surface of the billet and stay on the billet than the water sprayed on the other three sides (the wider the billet, the longer the stay time). Therefore, under the same amount of spray water, the cooling effect of the inner arc side of the billet is the best, and the cooling effects of the other three sides of the billet are almost the same. Furthermore, in this embodiment, the amount of spray water on the inner arc side of the billet is independently adjustable and less than the amount of spray water on the other three sides of the billet, so that the cooling intensity of the inner arc side of the billet is equivalent to the cooling intensity of the outer arc side of the billet, the left side of the billet and the right side of the billet, thereby achieving uniform cooling of the four sides of the billet, and almost no increase in the configuration of the continuous casting machine (only a valve needs to be added to the original pipeline), achieving low cost, simple operation and strong practicability.

[0021] The second partition is the first arc segment, and its influence on the overall cooling effect is higher than that of other arc segments. Therefore, the second partition is selected so that only the spray water volume on the inner arc side of the ingot can be adjusted separately. In order to further ensure the cooling uniformity, the third partition can be added so that only the spray water volume on the inner arc side of the ingot can be adjusted separately.

[0022] Before continuous casting begins, test spraying is performed to observe whether the flow indication on the cooling partition main pipeline can reach the design value: if it can, it means that the spray water strips in the cooling partition are not blocked; if not, it means that the spray water strips in the cooling partition are blocked. Then further observe the pressure indications on the branch pipelines of the spray water strips corresponding to the four sides of the ingot. If there is a branch pipeline with a relatively significantly higher pressure indication, it is determined that the spray water strips on the branch pipeline are blocked. If the pressure indications on the four branch pipelines are not much different, it is determined that the spray water strips on the four branch pipelines are all blocked. The spray water strips are prone to blockage under long-term work. If they are not discovered in time, insufficient cooling will result. This method determines the blockage of the spray water strips and finds the specific blockage location by observing the flow indication on the main pipeline and the pressure indication on each branch pipeline. The blockage location can be found quickly and conveniently, and can be directly cleaned after finding it.

[0023] After the continuous casting machine starts casting, when adjusting the amount of spray water on the inner arc side of the ingot, observe the pressure indications on the branch pipes of the spray water strips corresponding to the four sides of the ingot, compare the difference between the pressure indications on the branch pipes of the spray water strips corresponding to the inner arc side of the ingot and the pressure indications on the branch pipes of the spray water strips corresponding to the other three sides of the ingot, and adjust the difference so that the difference is within a certain range. This method adjusts the amount of spray water on the inner arc side of the ingot by pressure comparison, so that the difference between the pressure on the branch pipes of the spray water strips corresponding to the inner arc side of the ingot and the pressure on the branch pipes of the spray water strips corresponding to the other three sides of the ingot is within a certain range, which ensures the cooling uniformity and avoids the difference from expanding and affecting the cooling effect.

[0024] After the continuous casting machine starts casting, the bulging of the left and right sides and the inner and outer arc surfaces of the ingot is measured offline. If the difference between the bulging of the left and right sides and the bulging of the inner and outer arc surfaces increases, the amount of spray water on the inner arc side of the ingot is further reduced until the difference between the bulging of the left and right sides and the bulging of the inner and outer arc surfaces is within a certain range. Square billets will bulge during high-speed drawing production. By measuring the size of the ingot before entering the straightening machine, it is found that the bulging of the inner and outer arc surfaces is slightly smaller than that of the left and right sides, indicating that bulging is more likely to occur on the left and right sides of the ingot, and after the straightening machine is pressed down for straightening, the difference between the bulging of the left and right sides and the bulging of the inner and outer arc surfaces will be further aggravated. When this method initially reduces the amount of spray water on the inner arc side of the ingot, the amount of spray water on the other three sides can be increased, so that the total amount of spray water on the left and right sides will be higher than the total amount of spray water on the inner and outer arcs, which relatively improves the cooling intensity on the left and right sides of the ingot. degree, so that a sufficiently thick billet shell can be formed on the left and right sides of the billet to resist bulging deformation, thereby reducing the bulging amount of the left and right sides; when the difference between the bulging amount of the left and right sides and the bulging amount of the inner and outer arc surfaces increases, it means that the cooling intensity of the left and right sides of the billet is insufficient. Therefore, the spraying water amount on the inner arc side of the billet can be further reduced, and the spraying water amount on the other three sides can be further increased. In this way, the total amount of spraying water on the left and right sides will be further higher than the total amount of spraying water on the inner and outer arcs, which further improves the cooling intensity on the left and right sides of the billet and can further reduce the bulging amount of the left and right sides.

[0025] Embodiment 2 This embodiment discloses a billet continuous casting secondary spray cooling device, such as Figure 1 and Figure 2As shown, it includes several cooling zones arranged in sequence, each cooling zone is equipped with a spray water strip for spray cooling the four sides of the ingot 8, four branch pipes 2 for supplying water to the spray water strips corresponding to the four sides of the ingot 8, a main pipe 1 for supplying water to the four branch pipes 2, and a main regulating valve 3 arranged on the main pipe 1, and the main regulating valve 3 is used to adjust the overall cooling intensity of the cooling zone; for the cooling zones with one or more arc segments, a branch regulating valve 4 is arranged on the branch pipe 2 of the spray water strip corresponding to the inner arc side of the ingot 8, and the branch regulating valve 4 is used to adjust the spray water volume on the inner arc side of the ingot 8, so that the spray water volume on the inner arc side of the ingot 8 in the same cooling zone is less than the spray water volume on the outer arc side of the ingot 8, the left side of the ingot 8 and the right side of the ingot 8. In the cooling zone of the arc segment, the length of the outer arc side of the billet 8 is longer than that of the inner arc side (the thicker the billet 8, the more obvious it is). Therefore, the cooling area of ​​the inner arc side of the billet 8 is the smallest, and due to gravity, the spray water on the inner arc side is easier to reach the surface of the billet 8 and stay on the billet 8 than the spray water on the other three sides (the wider the billet 8, the longer the stay time). Therefore, under the same amount of spray water, the cooling effect of the inner arc side of the billet 8 is the best, and the cooling effects of the other three sides of the billet 8 are almost the same. Furthermore, in this embodiment, the amount of spray water on the inner arc side of the billet 8 is independently adjustable and less than the amount of spray water on the other three sides of the billet 8, so that the cooling intensity of the inner arc side of the billet 8 is equivalent to the cooling intensity of the outer arc side of the billet 8, the left side of the billet 8 and the right side of the billet 8, thereby achieving uniform cooling of the four sides of the billet 8, and almost no increase in the configuration of the continuous casting machine (only a valve needs to be added to the original pipeline), so as to achieve low cost, simple operation and strong practicability.

[0026] The sub-regulating valve 4 is selected to be installed on the sub-pipeline 2 of the spray water strip corresponding to the inner arc side of the billet 8 in the second partition; or, the sub-regulating valve 4 is selected to be installed on the sub-pipeline 2 of the spray water strip corresponding to the inner arc side of the billet 8 in the second and third partitions. The second partition is the first arc segment, and its influence on the overall cooling effect is higher than that of other arc segments. Therefore, the second partition is selected to allow only the spray water volume on the inner arc side of the billet 8 to be adjusted separately. In order to further ensure the cooling uniformity, the third partition can also be added to allow only the spray water volume on the inner arc side of the billet 8 to be adjusted separately.

[0027] like Figure 1 and Figure 2As shown: the main pipeline 1 is also provided with a manual valve 7, a flow detection component 5 (such as a flow meter) and a pressure detection component 6 (such as a pressure gauge or a pressure remote transmitter), and each branch pipeline 2 is also provided with a pressure detection component 6 (such as a pressure gauge or a pressure remote transmitter); the main regulating valve 3, manual valve 7, flow detection component 5 (flow meter) and pressure detection component 6 on the main pipeline 1 are located in the water distribution chamber 10, and the branch regulating valve 4 and pressure detection component 6 on each branch pipeline 2 are arranged outside the secondary cooling chamber 9 to avoid high-temperature damage to the ingot 8 and facilitate operation and observation by personnel; the main regulating valve 3 on the main pipeline 1 is controlled in linkage with the flow detection component 5, and the branch regulating valve 4 is remotely controlled or manually controlled on site.

[0028] The working process of the billet continuous casting secondary spray cooling device is: Before continuous casting, test spraying is carried out, and the main regulating valve 3 and the sub-regulating valve 4 are fully opened to observe whether the flow indication on the cooling zone main pipeline 1 can reach the design value: if it can, it means that the spray water strips in the cooling zone are not blocked; if it cannot, it means that the spray water strips in the cooling zone are blocked. Then further observe the pressure indications on the sub-pipes 2 of the spray water strips corresponding to the four sides of the ingot 8. If there is a sub-pipe 2 with a relatively significantly high pressure indication, it is determined that the spray water strips on the sub-pipe 2 are blocked. If the pressure indications on the four sub-pipes 2 are relatively high, it is determined that the spray water strips on the sub-pipe 2 are blocked. If the pressure indications are not much different, it is determined that the spray water strips on the four branch pipes 2 are all blocked, and the blocked spray water strips can be directly cleaned until the spray water strips in each cooling zone are checked to be unblocked and the continuous casting machine is started; the spray water strips are prone to blockage under long-term work. If they are not discovered in time, insufficient cooling will result. This method determines the blockage of the spray water strips and finds the specific blockage location by observing the flow indication on the main pipeline 1 and the pressure indications on each branch pipe 2, and can quickly and conveniently find the blockage location.

[0029] After the continuous casting machine starts casting, the amount of spray water on the inner arc side of the ingot 8 is adjusted by the sub-regulating valve 3, and the pressure indications on the sub-pipelines 2 of the spray water strips corresponding to the four sides of the ingot 8 are observed, and the difference between the pressure indications on the sub-pipelines 2 of the spray water strips corresponding to the inner arc side of the ingot 8 and the pressure indications on the sub-pipelines 2 of the spray water strips corresponding to the other three sides of the ingot 8 are compared, and the sub-regulating valve 3 is adjusted to make the difference within a certain range; the method adjusts the amount of spray water on the inner arc side of the ingot 8 by pressure comparison, so that the difference between the pressure on the sub-pipeline 2 of the spray water strips corresponding to the inner arc side of the ingot 8 and the pressure on the sub-pipeline 2 of the spray water strips corresponding to the other three sides of the ingot 8 is within a certain range, which not only ensures the cooling uniformity, but also avoids the expansion of the difference and affects the cooling effect.

[0030] The bulging of the left and right sides and the inner and outer arc surfaces of the ingot 8 is measured offline. If the difference between the bulging amount of the left and right sides and the bulging amount of the inner and outer arc surfaces increases, the amount of spray water on the inner arc side of the ingot 8 is further reduced through the sub-regulating valve 3 until the difference between the bulging amount of the left and right sides and the bulging amount of the inner and outer arc surfaces is within a certain range; the ingot 8 will bulge during high-speed drawing production. By measuring the size of the ingot 8 before entering the straightening machine, it is found that the bulging amount of the inner and outer arc surfaces is slightly smaller than that of the left and right sides, indicating that bulging is more likely to occur on the left and right sides of the ingot 8, and after the straightening machine is pressed down for straightening, the difference between the bulging amount of the left and right sides and the bulging amount of the inner and outer arc surfaces will be further aggravated. When this method initially reduces the amount of spray water on the inner arc side of the ingot 8, it can increase the amount of spray water on the other three sides. of spraying water, so that the total amount of spraying water on the left and right sides will be higher than the total amount of spraying water on the inner and outer arcs, which will relatively improve the cooling intensity on the left and right sides of the ingot 8, so that the left and right sides of the ingot 8 can form a sufficiently thick ingot shell to resist bulging deformation, thereby reducing the bulging amount of the left and right sides. When the difference between the bulging amount of the left and right sides and the bulging amount of the inner and outer arc surfaces increases, it means that the cooling intensity on the left and right sides of the ingot 8 is insufficient. Therefore, further reducing the spraying water amount on the inner arc side of the ingot 8 can further increase the spraying water amount on the other three sides, so that the total amount of spraying water on the left and right sides will be further higher than the total amount of spraying water on the inner and outer arcs, which will further improve the cooling intensity on the left and right sides of the ingot 8, and can further reduce the bulging amount of the left and right sides.

[0031] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

Claims

1. A method for secondary spray cooling of continuous casting of square billets, which independently adjusts the spray water volume of each cooling zone according to different cooling intensity requirements of each cooling zone; characterized in that: For one or more arc-shaped cooling zones, within the same cooling zone, only the spray water volume on the inner arc side of the billet can be adjusted separately. By adjusting the spray water volume on the inner arc side of the billet, the spray water volume on the inner arc side of the billet is made smaller than the spray water volume on the outer arc side of the billet, the left side of the billet and the right side of the billet.

2. The billet continuous casting secondary spray cooling method according to claim 1, characterized in that: Selecting the 2nd zone allows only the amount of spray water on the inner arc side of the ingot to be adjusted individually; or selecting the 2nd and 3rd zones allows only the amount of spray water on the inner arc side of the ingot to be adjusted individually.

3. The billet continuous casting secondary spray cooling method according to claim 1, characterized in that: Before continuous casting starts, a test spray is carried out to observe whether the flow indication on the main pipeline of the cooling zone can reach the design value: if it can, it means that there is no blockage in the spray water strips in the cooling zone; if not, it means that there is blockage in the spray water strips in the cooling zone. Then, the pressure indications on the branch pipelines of the spray water strips corresponding to the four sides of the ingot are further observed. If there is a branch pipeline with a relatively significantly high pressure indication, it is determined that the spray water strips on the branch pipeline are blocked. If the pressure indications on the four branch pipelines are not much different, it is determined that the spray water strips on the four branch pipelines are all blocked.

4. The method for secondary spray cooling of billet continuous casting according to claim 1, characterized in that: After the continuous casting machine starts casting, when adjusting the amount of spray water on the inner arc side of the ingot, observe the pressure indications on the branch pipes of the spray water strips corresponding to the four sides of the ingot, compare the difference between the pressure indications on the branch pipes of the spray water strips corresponding to the inner arc side of the ingot and the pressure indications on the branch pipes of the spray water strips corresponding to the other three sides of the ingot, and make the difference within a certain range through adjustment.

5. The method for secondary spray cooling of billet continuous casting according to claim 1, characterized in that: After the continuous casting machine starts pouring, the bulging of the left and right sides and the inner and outer arc surfaces of the ingot are measured offline. If the difference between the bulging of the left and right sides and the bulging of the inner and outer arc surfaces increases, the amount of water sprayed on the inner arc side of the ingot is further reduced until the difference between the bulging of the left and right sides and the bulging of the inner and outer arc surfaces is within a certain range.

6. A secondary spray cooling device for continuous casting of square billets, comprising a plurality of cooling zones arranged in sequence, each cooling zone being equipped with a spray water strip for spray cooling the four sides of the billet, four branch pipes for supplying water to the spray water strips corresponding to the four sides of the billet, a main pipe for supplying water to the four branch pipes, and a main regulating valve arranged on the main pipe, the main regulating valve being used to adjust the overall cooling intensity of the cooling zone in which it is located; characterized in that: For one or more of the cooling zones of the arc-shaped segments, a sub-regulating valve is provided on the sub-pipeline of the spray water strip corresponding to the inner arc side of the ingot, and the sub-regulating valve is used to adjust the amount of spray water on the inner arc side of the ingot, so that the amount of spray water on the inner arc side of the ingot in the same cooling zone is less than the amount of spray water on the outer arc side of the ingot, the left side of the ingot and the right side of the ingot.

7. The billet continuous casting secondary spray cooling device according to claim 6, characterized in that: Optionally, a sub-regulating valve may be installed on the sub-pipeline of the spray water strip corresponding to the inner arc side of the second partition casting; or, optionably, a sub-regulating valve may be installed on the sub-pipeline of the spray water strip corresponding to the inner arc side of the second and third partition castings.

8. The billet continuous casting secondary spray cooling device according to claim 6, characterized in that: The main pipeline is also equipped with a manual valve, a flow detection device and a pressure detection device, and each branch pipeline is also equipped with a pressure detection device.

9. The billet continuous casting secondary spray cooling device according to claim 8, characterized in that: The sub-regulating valves and pressure detection components on each sub-pipeline are arranged outside the secondary cooling chamber.

10. The billet continuous casting secondary spray cooling device according to claim 6, characterized in that: The sub-regulating valve is remotely controlled or manually controlled on site.

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