JPS6157920B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for introducing an electrolyte under pressure for forced circulation to a portion of the wall of a metal piping system and for cleaning that wall portion by electropolishing with a moving electrode. It relates to an apparatus for carrying out the invention.

Removal of contaminants from metal surfaces that are difficult to access or reach, such as the inner walls of pipes or other parts of metal piping systems, and in particular the removal of radioactive contaminants in such piping systems, has traditionally been difficult. In some cases, good results were not obtained or implementation was not satisfactory. Therefore, one of the common methods is electrolytic polishing. However, in the past, only tubes that had been disassembled into lengths of several meters could be treated with movable electrodes. This involved immersing the entire tube in electrolyte and filling a chamber within the previously sealed tube (tube section) with electrolyte (RPAIIen and HWA Arrowsmith, “Materials Performance”, VoI.18). No.11.(1979
(see pages 21-26).

One of the disadvantages of this method is that the tube to be cleaned must be disassembled before electropolishing. Furthermore, it is not possible to pass the electrode through bends or cut-off valves.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and apparatus for cleaning metal piping systems without the need for disassembly. Here, by pipe system we mean straight pipes and curved pipes including shutoff devices such as spherical pots, slide valves, etc. The method of the present invention is intended to enable sufficient purification of the ascending or descending piping. The method and apparatus are particularly intended for decontamination of radioactively contaminated piping systems.

This purpose, according to the invention, is achieved by spraying electrolyte at a high pressure of 50 bar or more onto a part of the wall of the pipe system, by means of a high-pressure jet flow through the pipe system, using a high-pressure nozzle with a cap at one end. This is achieved by moving an electrode with an insulating spacer at the other end.

The device according to the invention for carrying out this method comprises an electrolyte outflow opening facing the wall to be purified for forced circulation of the electrolyte and an insulating spacer which is fixedly or movably arranged at least in the electrode area. in an apparatus for cleaning the inner walls of a metal piping system by electrolytic polishing, by means of an electrode that moves in reaction to a high-pressure jet stream of electrolyte that is blown onto a part of the wall of the piping system at a high pressure of 50 bar or more. , high voltage having a metallic stabilizing element acting as an electrical conductor or a metallic strand acting as an electrical conductor and having at one end a plurality of openings oriented radially and at an angle to the internal wall of the piping system. An elastic high-pressure hose provided with a nozzle, an elastic cap provided at the tip of the high-pressure nozzle, and an insulating spacer provided at the opposite end of the electrode in the area of the electrode. It is characterized in that it has an insulating spacer having an area smaller than the cross-sectional area, and a metal elastic electrode arranged around the end piece of the high-pressure hose and connected to a conductor.

The electrode of the device according to the invention is formed as a spiral cathode or as a spiral tape.

The elasticity of the electrodes allows adaptation to curves. The automatic conveyance by the reaction of the high-pressure jet stream eliminates the need for disassembly of the tube to be polished and also allows processing in bends and slide valves as well as in inclined piping. Very good cleaning of the pipe can be achieved by simultaneously utilizing a high pressure jet stream. Automated transport allows the tube to be electropolished remotely, thereby significantly reducing the radiation burden on the workers. The electrolyte to be used is forced to impinge on the inner wall of the tube through a high-pressure jet nozzle at a pressure of about 50 bar to about 600 bar. An automatic forward movement of the electrode within the tube is achieved by the reaction of the electrolyte jet stream directed obliquely to the tube wall. The electrolyte jet flow allows the passage of a continuous and uniformly large current. In most cases, a current of 300 to 400 amperes is sufficient.

Furthermore, since the elastic cap and the insulating spacer form a so-called liquid plug to prevent the electrolyte from flowing out rapidly, there is no possibility that air bubbles harmful to the polishing action will adhere to the inner wall of the piping system.

The present invention will be described in detail below based on embodiments shown in the drawings.

In order to decontaminate the inner wall of the piping system 1 contaminated with radioactive impurities, an elastic high-pressure hose 5 is inserted into this piping system. This high-pressure hose 5 has a high-pressure jet nozzle 9 made of special steel at its tip 7, and an electrode (cathode) 4 made of VA wire with a thickness of 3 mm is wound around the hose 5 over a length of about 30 mm. It has two spacers 11 and 12 made of synthetic resin. A high-pressure jet pump (not shown) with an output of 50 bar pumps the electrolyte at 1200 bar.
/h through a high-pressure hose 5 and a jet nozzle 9 into a piping system with an internal diameter of 150 mm or onto its inner wall 2. In this case, the piping system means a 5 m long pipe with a 90° bend in the middle. The high pressure nozzle 9 has a row of openings 10;
These openings 10 are arranged so that the electrolyte impinges on the inner wall of the pipe 1 at an angle. The feed rate of this device inside the pipe is 5 cm/min. Current flows from a power supply (not shown) in the electrical conductor 6 and further through the cathode 4 arranged around the end piece 8 of the high-pressure hose 5, the electrolyte 3 and the metal inner wall 2 of the tube 1. The strength of the current is approximately 300 amperes. The high-pressure nozzle 9 has an elastic cap 13 at its tip, and this cap 13, together with a spacer 12 arranged at the opposite end of the electrode, prevents the electrolyte 3 spouted through the high-pressure nozzle 9 from rapidly flowing out. It acts like there is no such thing. Insulating spacers 11 and 1
2 is in the shape of a star with three arms in this case and has a central opening so that it can be pushed into the high pressure hose 5. In this case, the spacer 12 has an area twice the cross-sectional area of the spacer 11.

According to the invention, a decontamination factor of 300 is obtained. This decontamination coefficient is increased by 10 times when the inner wall 2 of the pipe is once again sprayed (washed) with hot water and high pressure.
Overall a decontamination factor of 3000 is achieved.

[Brief explanation of the drawing]

The drawings are cross-sectional views showing embodiments of the present invention. 1: Piping, 2: Inner wall, 3: Electrolyte, 4: Electrode (cathode), 5: High pressure hose, 6: Conductor, 7: Tip of high pressure hose, 8: End piece, 9: High pressure nozzle,
10: opening, 11, 12: spacer, 13: cap.

Claims (1)

[Scope of Claims] 1. A method in which an electrolyte is introduced under pressure for forced circulation into a part of a wall of a metal piping system and the wall part is purified by electrolytic polishing with a moving electrode, the wall part being subjected to a pressure of 50 bar. Alternatively, it is possible to spray an electrolytic solution at a higher pressure and move an electrode, which has a high-pressure nozzle with a cap at one end and an insulating spacer at the other end, through the piping system by the reaction of the high-pressure jet flow. A method for purifying the inner walls of metal piping systems using electrolytic polishing. 2. Piping systems with electrolyte outflow openings facing the wall to be purified for forced circulation of the electrolyte and insulating spacers fixedly or movably arranged at least in the area of the electrodes at high pressures of 50 bar or more. A stabilizing element made of metal acting as an electrical conductor 6 in an apparatus for cleaning the internal walls of a metal piping system by electrolytic polishing by means of an electrode moving in reaction to a high-pressure jet stream of electrolyte sprayed onto a section of the wall. Alternatively, a high-pressure nozzle 9 is provided with a metal strand acting as an electrical conductor 6 and having at one end 7 a plurality of openings 10 oriented radially and at an angle to the inner wall 2 of the pipe system 1. A minimum cross-sectional area that is larger than the area of the elastic high-pressure hose 5, the elastic cap 13 provided at the tip of the high-pressure nozzle 9, and the insulating spacer 11 provided at the opposite end of the electrode and located in the electrode area, and that the piping system must pass through. Insulating spacer 1 having a smaller area than
2, and cleaning the inner wall of a metal piping system by electrolytic polishing, characterized in that it has a metal elastic electrode 4 arranged around the end piece 8 of the high-pressure hose 5 and connected to the electrical conductor 6; equipment for. 3. Device according to claim 2, characterized in that the electrode is formed as a spiral cathode 4. 4. Device according to claim 2, characterized in that it is formed as a spiral tape from four electrodes.