JPH0341266B2 - - Google Patents

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field) The present invention is applicable to, for example, a nuclear power plant,
The present invention relates to an arc saw cutting device used to cut steel materials such as nuclear reactor pressure vessels underwater.

(Prior Art) For example, in a nuclear power plant, equipment such as a reactor pressure vessel reaches the end of its life after long-term use.
In that case, it is necessary to completely dismantle and remove equipment such as the reactor pressure vessel. At this time, it is necessary to cut the structure underwater, and the following cutting methods are available for such work. Namely, there are gas cutting methods, methods combining gas cutting methods and gouging methods, electrode type water jet cutting methods, plasma cutting methods, electrical discharge machining methods, and the like. However, with this method, there is a problem in cutting underwater steel materials such as thick plates and pipes that have been activated in a nuclear reactor. For example, in the case of the gas cutting method described above, if there is a cladding of austenitic stainless steel, it becomes impossible to cut. In addition, a method that combines gas cutting and gouging has not yet been put to practical use, and even if it were, the cutting speed would be slow and there would be a lot of by-products during cutting. It is not suitable for cutting radioactive materials.

Based on this actual situation, a cutting method called arc saw cutting has been considered. The outline will be explained below with reference to FIGS. 2 to 4. Reference numeral 1 in FIG. 2 indicates a rotating electrode, and this rotating electrode 1 is connected to the casing 2.
It is fixed to a shaft 3 which is rotatably installed inside the shaft. As shown in FIG. 3, slits 1A are formed at equal intervals in the circumferential direction on the outer peripheral edge of the rotating electrode 1, and the slits 1A scrape out and eliminate molten material (molten slag) generated during cutting.
This shaft 3 is connected to a hydraulic motor 4 installed outside the casing 2, and by driving this hydraulic motor 4, the rotating electrode 1 is rotated. A copper brush 5 is installed inside the casing 2 and around the outer periphery of the shaft 3, and this copper brush 5 is connected to one pole (-pole) of a DC power source 7 via a cable 6. . On the other hand, the object to be cut 9 is connected to the other pole (+pole) of this DC power supply 7 via a cable 8 .

The casing 2 is connected to a piston 11 of a hydraulic cylinder mechanism 10, and as the piston 11 slides, the casing 2 slides toward and away from the object 9 to be cut. The hydraulic cylinder mechanism 10 is controlled by a servo system 12. That is, the rotating electrode 1 is connected to the object 9 to be cut.
The cutting current when cutting is performed close to the cable 6 is detected by an ammeter 13 inserted in the cable 6, and the detection signal is input to a current comparator 14. In addition to the detection signal described above, a control signal set in advance from a control panel 15 is input to the current comparator 14. The current comparator 14 compares these detection signals and control signals and outputs the difference therebetween to the servo system 12 as a difference signal. The servo system 12 controls the hydraulic cylinder mechanism 10 based on this difference signal to maintain the cutting current constant. Note that reference numeral 16 in the figure indicates an air inlet, and compressed air is injected into the casing 2 as a shielding gas through this air inlet 16, and the rotating electrode 1 is
shields the power supply to the

According to the above configuration, when cutting the object 9 to be cut, first the hydraulic motor 4 is driven and the rotating electrode 1 is cut.
While rotating, the hydraulic cylinder mechanism 10 is driven to move the piston 11 downward in the figure,
The rotating electrode 1 is brought close to the object 9 to be cut. When the rotating electrode 1 is located at a distance of about 0.1 to 0.2 mm from the object to be cut, arc discharge is performed to generate a DC low voltage and high current (voltage approximately 50V, current approximately
The cutting operation is carried out by melting the object 9 with electric energy of 4000 A to 20000 A and removing melting slag through the slit 1A.

Next, the configuration of the head portion of the arc saw cutting device will be explained in detail with reference to FIG. FIG. 4 is a cross-sectional view of the head portion, and the rotating electrode 1 is held between a pair of flanges 31, 31, and in this state is fixed to the shaft 3 via a collar 32 with a screw 33. Reference numeral 34 in the figure indicates a bolt fixing the flanges 31, 31. The shaft 3 is pivotally supported at both ends by rolling bearings 36, 36 via insulators 35, 35, respectively. These rolling bearings 36, 36 are installed in bearing chambers 37, 37 formed in the casing 2, and the portion where the brush 5 is installed is a brush chamber 38. Note that a collector ring 39 is installed between the brush 5 and the shaft 3. The brush 5 is composed of a plurality of divided brushes 5A, and each divided brush 5A is biased toward the collector ring 39 by a spring 40, respectively. Further, the biasing force of these brushes 5A is adjusted as appropriate by adjusting screws 41. The above shaft 3 and hydraulic motor 4
A spline 42 is interposed between them. A tacho line 43 is attached to the outer periphery of this spline 42. Further, reference numerals 44 and 45 in the figure indicate the inlet and outlet flanges of the hydraulic motor 4, respectively;
Reference numeral 6 indicates a bolt fixing the hydraulic motor 4 to the casing 2, reference numeral 47 indicates a stop pin, and reference numeral 48 indicates a cover.

In the above configuration, for example, during cutting work, phenomena such as an abnormal decrease in rotational speed, seizure due to an abnormal temperature rise of the bearing 23, or a crack in a portion of the casing 2 may occur. These problems are due to the fact that by supplying a large current to the rotating electrode 1, Joule heat is generated in the shaft 3, and the heat is stored without being cooled, resulting in an abnormally high temperature. The decrease in rotational speed as described above not only reduces the ability to discharge molten slag during cutting, but also causes seizure of the bearing 36, which has the lowest allowable limit for temperature rise, and damage to the casing 2, making it impossible to continue operation. If such a situation were to occur, workers would have to disassemble and replace parts contaminated with radioactivity, reducing the risk of worker exposure. There were concerns about this, and improvements were required.

(Problems to be Solved by the Invention) As described above, in the conventional configuration, there is a problem that the function deteriorates due to a decrease in rotational speed, etc.
The present invention has been made based on the above points, and its purpose is to eliminate situations where the cutting ability is reduced or continuous operation is impossible due to various adverse effects caused by the generation of shaft heat, and It is an object of the present invention to provide an arc saw cutting device capable of cutting even steel materials at high speed and at the same time reducing the radiation exposure of workers.

(Means for solving the problem) That is, the arc saw cutting device according to the present invention has the following features:
A casing, a shaft rotatably housed in the casing and having both ends supported by bearings installed in a bearing chamber, a rotating electrode fixed to the tip of the shaft, and a control mechanism for sliding the casing. In the arc saw cutting device, a cooling water inlet is formed at the rear end of the shaft, and a flow path through which the cooling water supplied from the cooling water inlet flows is formed in the shaft in the axial direction of the shaft. A drain port is formed along the shaft, and a drain port for discharging the cooling water is formed at the tip of the shaft.

(Function) In other words, the shaft is cooled by forming a flow path through which cooling water flows through the shaft, and injecting cooling water from a cooling water inlet formed in the casing to flow through the flow path. It is.

(Example) An example of the present invention will be described below with reference to FIG. FIG. 1 is a sectional view of the head portion of the arc saw cutting device according to the present embodiment. Note that parts that are the same as those in the prior art are denoted by the same reference numerals, and their explanations will be omitted. A cooling water passage 101 is formed in the collector ring 39 in the axial direction, and cooling water passages 102 are connected to both ends of the cooling water passage 101, respectively.
and 103 are formed on the shaft 3. These cooling water passages 102 and 103 communicate with a cooling water passage 101 formed in the collector ring 39 via cooling water passages 104 and 105. The cooling water passage 102 communicates with a cooling water inlet 106 formed in the casing 2 via a passage 107. Further, a drain port 108 is connected to the cooling water flow path 103, and this drain port 108
The tip of the rotary electrode 1 is directed toward the portion where the rotating electrode 1 is fixed to the shaft 3. That is, the cooling water inlet 1
06 from a cooling water supply device (not shown), and the cooling water is supplied to the cooling water channels 107 and 10.
2, 104, 101, 105, and 103 are made to flow in sequence and drained onto the rotating electrode 1 through the drain port 108.
In this way, the shaft 3 is cooled and the rotating electrode 1 is also cooled.

Here, the amount of heat generated during actual operation will be calculated by taking heat generated by contact between the brush 5 and the collector ring 39 as an example. First, if the amount of heat generated by the contact between the brush 5 and the collector ring 39 is _Q1 , then _Q1 is expressed by the following equation.

Q ₁ = 9.81×P×A×N×v×u …() However, P: Brush pressure 200g/cm ² A: Brush area 40cm ² N: Number of brushes 8 v: Contact speed 4.7m/sec u: Friction Coefficient 0.2 Therefore, the amount of heat generated Q ₁ is as follows.

Q ₁ = 9.81 x 200 x 40 x 8 x 4.7 x 0.2 = 590 (w) Next, if the amount of heat generated by the electric resistance of the brush portion is Q ₂ , Q ₂ is expressed by the following formula.

Q ₂ = ΔV × I … () However, ΔV: Voltage drop 0.3V I: Average current 20000A Therefore, the amount of heat generated Q ₂ is as follows.

Q ₂ = 0.3 x 20000 = 6000 (w) Next, calculate the amount of heat generated by the electrical resistance of shaft 3 as Q ₃
Then, Q ₃ is expressed by the following formula.

Q ₃ = R×I ² …() However, R: Shaft resistance 0.05mΩ I: Average current 20000A Therefore, the amount of heat generated Q ₃ is as follows.

Q ₃ =0.05×10 ^-3 ×20000 ² =20000 (w) From the above, the total generated heat amount Q is as follows.

Q=Q ₁ +Q ₂ +Q ₃ =0.59+6+20=26.6 (kw) As described above, the effects of such generated heat on the machine are the expansion of the shaft 3 in the axial direction and the temperature rise of the shaft 3. This expansion of the inner shaft 3 can be solved by selecting an appropriate bearing (for example, a circular roller bearing on one side). Since the oil seals and the like disposed in the shaft 3 have a small tolerance range for temperature rise, they may be easily damaged by the temperature rise of the shaft 3. In this embodiment, the temperature rise of the shaft 3 is effectively suppressed by circulating cooling water through the cooling water flow path formed in the collector ring 39 and the shaft 3.
The aim is to eliminate various adverse effects caused by temperature rise.

According to the above configuration, the rotating electrode 1 rotates due to the rotation of the shaft 3, and approaches the object to be cut 9 as the casing 2 moves. When the object approaches a predetermined distance, arc discharge is performed to cut the object 9 and cut the slit 1A of the rotating electrode 1.
This will remove melting slag. During this cutting operation, the cooling water injected from the cooling water inlet 106 flows through the following path. That is, the cooling water injected from the cooling water inlet 106 flows through the flow path 1.
07 into the flow path 102, and further flows into the flow path 103 through the flow paths 104, 101 and 105.
flow inside. At this time, the shaft 3 is cooled to effectively suppress the generation and accumulation of heat in the shaft 3. The water is then drained onto the rotating electrode 1 through the drain port 108. This also cools the rotating electrode 1. Thereafter, cooling water is continuously supplied through the same route.

According to the arc saw cutting device according to the present embodiment, the cooling water channels 101, 102, 103, 10 formed in the shaft 3 and the collector ring 39
4, 105 and 107 by circulating cooling water,
Since the shaft 3 is cooled, the generation and accumulation of heat in the shaft 3 is suppressed, and various adverse effects caused by the generation and accumulation of heat in the shaft 3 are prevented, such as expansion of the shaft 3, temperature rise of the bearing 36, and seizure and rotation due to the expansion of the shaft 3. It is possible to prevent a decrease in speed, occurrence of cracks in the casing 2, etc. Further, in the case of this embodiment, the tip of the drain port 108 communicating with the cooling water flow path 103 is directed toward the portion of the rotating electrode 1 fixed to the shaft 3, so that the waste water is drained onto the rotating electrode 1. , the rotating electrode 1 can also be effectively cooled. Shaft 3 like this
Since not only the rotary electrode 1 is cooled effectively, but also the rotating electrode 1 is effectively cooled, it is possible to cut thick steel materials at high speed, and the frequency of damage to the bearing 36 etc. is greatly reduced, so replacement work etc. It is extremely effective in reducing radiation exposure of workers.

[Effects of the Invention] As detailed above, the arc saw cutting device according to the present invention includes a casing, a shaft rotatably housed in the casing, and having both ends pivotally supported by bearings installed in a bearing chamber. In an arc saw cutting device equipped with a rotating electrode fixed to the tip of the shaft and a control mechanism for sliding the casing, a cooling water inlet is formed at the rear end of the shaft, and the cooling water flow is formed in the shaft. A flow path through which cooling water supplied from the inlet flows is formed along the axial direction of the shaft, and a drain port for discharging the cooling water is formed at the tip of the shaft.

Therefore, the cooling water that flows into the shaft from the cooling water inlet flows through the flow path formed in the shaft and flows out from the drain hole formed at the tip of the shaft, which causes the temperature of the shaft to rise due to Joule heat. , it is possible to prevent the temperature rise of the rotating electrode and the bearing. Therefore, it is possible to prevent a decrease in cutting ability or an inability to perform continuous operation, and it is possible to provide a highly reliable arc saw cutting device.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the head portion of an arc saw cutting device showing an embodiment of the present invention, Figs. 2 to 4 are views showing a conventional example, and Fig. 2 is a diagram showing a schematic configuration of the arc saw cutting device. 3 is a plan view of the rotating electrode, and FIG. 4 is a sectional view of the head portion of the arc saw cutting device. DESCRIPTION OF SYMBOLS 1...Rotating electrode, 2...Casing, 3...Shaft, 9...Object to be cut, 10...Cylinder mechanism, 36...Bearing, 37...Bearing chamber, 101,1
02, 103, 104, 105, 107...Cooling water flow path, 106...Cooling water inlet, 108...Drain port.

Claims (1)

[Claims] 1. A casing, a shaft that is rotatably housed in the casing and whose both ends are supported by bearings installed in a bearing chamber, a rotating electrode fixed to the tip of the shaft, and a control for sliding the casing. In the arc saw cutting device, a cooling water inlet is formed at the rear end of the shaft, and a flow path through which cooling water supplied from the cooling water inlet flows into the shaft is arranged in the axial direction of the shaft. An arc saw cutting device characterized in that a drain port is formed along the shaft, and a drain port for discharging the cooling water is formed at the tip of the shaft.