JP2006150394A - Plasma cutting apparatus for half cutting of small diameter piping used in nuclear power plant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain the sticking of dross, fumes, etc. inside piping to the utmost in the case of cutting the piping by means of a plasma torch, and further to suppress the thermal deformation of the piping caused by heat generated in the case of half-cutting the piping to the utmost. <P>SOLUTION: A plasma cutting apparatus is composed of fixing devices 20 for fixing the piping 10 at a cutting position, the plasma torch 30 for cutting the piping, a plasma torch moving device 40 for moving the plasma torch in the direction parallel with the piping, a plasma torch pressing device 50 for pressing the plasma torch against the piping under constant pressure, and a compressed air pipe 60 for cooling a plasma arc, the dross, the fumes, etc. jetted into the piping and for discharging them outside the piping by the pressure of the compressed air. The dross, fumes, etc. generated in cutting the piping are discharged outside the piping by simultaneously moving the compressed air pipe so as to follow cutting motion by means of the plasma torch. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In nuclear power plants and facilities using radioisotopes, piping is generated where the inside and outside are contaminated by the radioactivity used in the facility. Such pipes are cut to an arbitrary length from the viewpoint of reducing radioactive waste, and are halved to decontaminate the outer surface and the melted portion, and then surface contamination inspection is performed. Contaminated piping will be stored and managed in the management building on the site until the inspection level is enforced by the national government.

  The present invention relates to a plasma cutting apparatus used for halving a pipe that is contaminated with a radioactive substance having an outer diameter of 48.6 mm or less of the pipe or is intended to be taken out from a management area.

  For example, it is known that plasma cutting is used for cutting a pressed part in an automobile body production line or the like (see Patent Document 1).

  In plasma cutting, if a dross generated during the cutting process, that is, an unnecessary object such as a metal oxide generated by melting of the base material at the time of plasma cutting adheres to a part on the product side of the base material, the product is defective. Become. For this reason, conventionally, a plasma cutting method in which dross does not adhere to the product side of the base material has been taken.

  Conventionally, as one method for preventing dross from adhering to the product side of the base material, plasma cutting is performed with the torch tilted in a direction opposite to the cutting direction by a predetermined angle θ (torch angle) from the direction perpendicular to the base material ( Cutting by advancing angle) has been performed (see Patent Document 1).

  Dross is generated or scattered in the forward direction of the torch. For this reason, since the dross generated by the cutting by the advance angle is melted sequentially with the movement of the torch, the dross does not remain in the part after cutting according to the above cutting method, and the cutting surface is excellent. Plasma cutting can be performed.

  On the other hand, when cutting with a torch when cutting a three-dimensional shaped press part, etc., when the torch cuts with a receding angle with respect to the base material, the torch is tilted toward the product panel side of the base material and the cutting process is performed It is also known that dross adheres to the waste material side of the base material and does not adhere to the product panel side (see Patent Document 1).

  Now, with a plasma cutting device, it is possible to cut a half of a single pipe pipe for scaffolding having an outer dimension of φ48.6 mm and a condenser heat exchange tube having an outer dimension of about φ28 mm. However, dross and fume adhere to the inside and cannot be processed well by the above-described method, so a new processing method is required to remove this. In addition, the U-shaped tube heat exchange tube in the stainless steel water heater with an outer dimension of about φ15.8mm has a cutting trajectory that is not straight due to thermal deformation caused by heat generated during cutting. The amount of adhering dross and fume is much larger than the amount adhering when cutting the single pipe pipe for a scaffold or condenser heat exchange tube, and it cannot be removed even by blasting performed after cutting.

Dross, fume, etc. adhering to the inside of the pipe not only interfere with decontamination but also cause the measurement accuracy of the surface contamination inspection to deteriorate. In the case of contamination that generates α-rays, the transmission power is very weak and is blocked by a thin sheet of paper. In addition, in the case of contamination that generates β-rays, it is shielded by a single thin metal, although the transmission power is stronger than α-rays. For this reason, if dross, fume, etc. are attached to the contaminated part of the α-rays and β-rays inside the pipe, the contamination cannot be detected by the measuring instrument for measuring the surface contamination. There is a risk of occurrence.
JP-A-6-142935

  Inside the pipe to be cut that is half-cut with plasma from the outside (hereinafter simply referred to as piping), the cut portion by the plasma torch always follows the plasma torch at the same interval, and a compressed air discharge port is provided. By discharging compressed air, plasma arc, dross, fume, etc. are discharged outside the pipe by wind pressure when cutting the plasma half, so that it can be suppressed as much as possible so that dross, fume, etc. do not adhere inside the pipe. In addition, it is possible to minimize the deformation caused by heat generated when cutting a pipe half, and it is possible to decontaminate and inspect contamination of the inner and outer surfaces of small-diameter pipes. Therefore, it is an object to make it possible to reduce the amount of waste generated in the management area.

A pipe, a fixing device for fixing the pipe at a cutting position, a plasma torch for cutting the pipe, a plasma torch moving device for moving the plasma torch in parallel with the pipe, and a constant force on the pipe. A small-diameter pipe used in a nuclear power generation facility with a plasma torch pressing device that is pressed with a compressed air pipe that cools a plasma arc, dross, or fume that is jetted into the pipe and discharges it outside the pipe with wind pressure A plasma cutting device for half cutting
The plasma torch is provided on both sides of the pipe at an angle of 45 ° to 60 ° in the forward direction with respect to the axial center of the pipe, and simultaneously with the cutting by the plasma torch, the compressed air pipe is caused to follow the inside of the pipe. The dross, fume, etc. generated during cutting are cooled before adhering to the inside of the pipe, and discharged outside the pipe by wind pressure.
The plasma torch moving device for moving the plasma torch in parallel with the pipe is composed of a pair of parallel moving guide rods, a driving device such as a ball screw, and a moving motor connected to the driving device. In addition to controlling the moving speed of the plasma torch, the plasma torch can always be moved parallel to the piping.
The plasma torch pressing device that presses the plasma torch against the pipe with a constant force includes a slide device that moves the plasma torch in a direction orthogonal to the pipe, a torch fixing device that fixes the plasma torch to the plasma torch pressing device, A pair of guide wheels that always keep the plasma torch at a fixed distance from the pipe, and a guide wheel, a plasma torch pressing device, and an air cylinder that generates a constant pressing force to always press the plasma torch fixing device against the piping.

1) By installing a compressed air pipe that always follows the cut part at the same interval inside the pipe that is half cut with plasma from the outside, and discharging the compressed air from this compressed air pipe, The plasma arc, dross, fumes, etc. are cooled and discharged to the outside of the pipe by wind pressure while being cut. Deformation can be suppressed as much as possible. As a result, plasma cutting of small-diameter piping is possible, decontamination and contamination inspection of the inner and outer surfaces of the piping are facilitated, and waste generated in the management area can be reduced.
2) By pressing the plasma torch against the pipe, the plasma torch can be held at a constant interval against the deformed pipe and the pipe where the deformation has occurred, enabling stable plasma generation and high accuracy. Half cutting can be performed.

  As shown in FIG. 1, the structure of the plasma cutting apparatus of the present invention is a plasma fixing device 20 for fixing a pipe 10, a plasma torch 30, and a plasma torch for moving the plasma torch 30 relative to the pipe 10 in parallel therewith. The moving device 40, the plasma torch pressing device 50 that presses the plasma torch 30 against the pipe 10 with a constant force, and the plasma arc, dross, or fumes sprayed inside the pipe 10 are cooled and discharged outside the pipe 10 by wind pressure. And a compressed air pipe 60.

  As shown in FIG. 2, the pipe 10 is fixed by sandwiching the pipe 10 from above and below by a lower fixing device 21 and an upper fixing device 22. The lower fixing device 21 is used in a fixed state, and the upper fixing device 22 can be moved up and down by an air cylinder 23 and the like for vertical movement. The pipe 10 is set automatically or manually at the half-cut position, and is fixed at a predetermined position by the vertical movement operation of the upper fixing device 22.

  The plasma torch moving device 40 that moves the plasma torch 30 in parallel to the pipe 10 is located between the pair of parallel movement guide rods 41 provided in parallel to the pipe 10 and the pair of parallel movement guide rods 41. A driving device 42 such as a ball screw and a driving motor 43 are used to control the moving speed of the plasma torch 30 and to always move the plasma torch 30 relative to the pipe 10 in parallel with the pipe 10. The moving speed of the plasma torch 30 at the time of plasma cutting is set at about 80 mm / min to 120 mm / min.

  The plasma torch pressing device 50 that presses the plasma torch 30 against the pipe 10 with a constant force is fixed to the slide device 51 that can move the plasma torch 30 in a direction orthogonal to the pipe 10 and the plasma torch pressing device 50. The torch fixing device 52, the two guide wheels 53 that always keep the plasma torch 30 and the pipe 10 at a constant distance (1 mm to 2 mm), and the guide wheel 53 via the plasma torch pressing device 50 and the plasma torch fixing device 52. The air cylinder 54 generates a constant pressing force so as to be always pressed against the pipe 10. The air cylinder 54 generates a pressing force in a range where the pipe 10 hits the guide wheel 53 and can be expanded and contracted to a position away from the pipe 10. In the cutting start, the guide wheel 53 on the front side of the pair of guide wheels 53 is pressed at the rear end portion of the pipe 10, and then the plasma generator 70 is switched on to generate plasma.

  The plasma generator 70 uses a device with a pilot arc. When the plasma torch 30 approaches the ground object, that is, the pipe 10 from a state where the pipe 10 and the plasma torch 30 are separated from each other, plasma is automatically generated. ing. When the plasma torch 30 is moved in parallel with the plasma torch 30 pressed against the pipe 10, plasma is generated and the pipe 10 is cut with the pipe 10 and the plasma torch 30 reaching a predetermined position. When the pipe 10 is detached from the plasma torch 30, the plasma generation is automatically stopped. In this state, the rear wheel 53 of the guide wheel is pressed against the end of the pipe 10. At this time, the pressing of the plasma torch pressing device 50 to the pipe 10 is finished.

  At the time of cutting, plasma arc, dross, fume and the like are cooled by compressed air ejected from the compressed air pipe 60 to the inside of the pipe 10, and are exhausted to the outside through the pipe 10 by wind pressure. The compressed air tube 60 is fixed to the plasma torch moving device 40 by a fixed arm 61. The tip of the compressed air tube 60 is always spaced from the plasma torch 30 by about 10 mm (see FIG. 1B), and moves in the pipe 10 as the plasma torch moving device 40 moves. A tube 62 is connected to the compressed air pipe 60 and is controlled by a control valve (not shown) so that compressed air is ejected when the plasma is cut. The compressed air has a pressure of 0.6 Mpa to 0.7 Mpa, and the compressed air pipe 60 has an outer diameter of 6 mm or more. The air flow rate should be 0.5 m3 / min or more in the standard state.

  In FIGS. 1 and 2, the plasma torch 30 is shown only on one side of the pipe 10, but is actually installed on both sides of the pipe. Therefore, it is possible to perform a half-cutting process by cutting the both sides of the pipe and dividing it into upper and lower parts without moving the pipe fixing device 20 and releasing the fixing of the pipe 10. Although two plasma torches 30 are attached to both sides of the pipe 10, two compressed air pipes 60 that move inside the pipe 10 do not enter because the pipe 10 has a small diameter. Further, the two plasma torches 30 on both sides of the pipe 10 cannot be moved simultaneously due to the characteristics of plasma cutting. Therefore, in order to use one compressed air pipe 60 for the two plasma torches 30 on both sides of the pipe 10, the plasma torch located on the rear side in the traveling direction moves and starts cutting at the same time. At the same time as the plasma torch 30 located on the rear side returns, the compressed air tube 60 also returns to its original position. Thereafter, when the front torch moves and cuts, the same compressed air pipe 60 moves. Thus, the single compressed air tube 60 can be used when cutting with the plasma torches on the left and right sides.

(A) is a top view of a plasma cutting device, (b) is a figure which shows the relationship between a plasma torch and a guide wheel. The perspective view which shows the state at the time of the cutting | disconnection of a plasma torch.

Explanation of symbols

10 Pipe to be cut (pipe) 20 Pipe fixing device
21 Lower fixing device 22 Upper fixing device
23 Air cylinder 30 Plasma torch
40 Plasma torch moving device 41 Parallel moving guide rod
42 Drive unit (ball screw, etc.) 43 Motor for movement
50 Plasma torch pressing device 51 Slide device
52 Torch fixing device 53 Guide wheel
54 Air cylinder 60 Compressed air pipe
70 Plasma generator

Claims (3)

A pipe to be cut, a fixing device for fixing the pipe to be cut at a cutting position, a plasma torch for cutting the pipe to be cut, a plasma torch moving device for moving the plasma torch in parallel with the pipe to be cut, and plasma A pressing device that presses the torch against the pipe to be cut with a certain force, and a compressed air pipe that cools the plasma arc, dross, or fumes that are jetted into the pipe to be cut and discharges it to the outside of the pipe by wind pressure. A plasma cutting device for half cutting of small-diameter pipes used in a nuclear power generation facility comprising:
The plasma torch is provided on both sides of the pipe to be cut at an angle of 45 ° to 60 ° in the forward direction with respect to the axis of the pipe to be cut, and simultaneously with the cutting by the plasma torch, the compressed air pipe is caused to follow. A nuclear power generation facility that moves the inside of the pipe to be cut, cools the dross, fumes, etc. generated at the time of cutting before adhering to the inside of the pipe to be cut and discharges them outside the pipe to be cut by wind pressure. The half-cutting device for small-diameter pipes used.   A plasma torch moving device that moves a plasma torch in parallel with the pipe to be cut comprises a pair of parallel guide rods, a driving device such as a ball screw, and a moving motor connected to the driving device. The plasma cutting device for half-cutting a small-diameter pipe used in a nuclear facility according to claim 1, wherein the moving speed of the plasma torch is controlled by means of the plasma torch and the plasma torch can always be moved in parallel with the pipe to be cut. . The pressing device that presses the plasma torch against the cutting target pipe with a constant force includes a slide device that moves the plasma torch in a direction orthogonal to the cutting target pipe, a torch fixing device that fixes the plasma torch to the plasma torch pressing device, Consists of a pair of guide wheels that keep the plasma torch at a constant distance from the pipe to be cut, and an air cylinder that generates a constant pressing force so that the guide wheels, plasma torch pressing device, and plasma torch fixing device are always pressed against the pipe to be cut A plasma cutting apparatus for half-cutting a small-diameter pipe used in the nuclear facility according to claim 1.

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