JPS597800B2 - Electrolytic composite polishing method for large towers and tanks - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for electrolytic composite polishing of large towers and tanks, which allows the inner or outer surfaces, including vertical surfaces, to be finished to a mirror finish at low cost and in terms of safety and hygiene. Regarding.

Generally, in large towers and tanks such as food and drug plants as well as chemical plants, the occurrence of deposits on the inner surfaces is an important cause of quality deterioration.

In addition, in vinyl chloride polymerization cans, residual vinyl chloride monomer is harmful, and cleaning operations to remove scale are strictly regulated. Due to this situation, stainless steel is used for the inner surface of the towers and tanks, and a thickness of 0.1 μm is used to prevent adhesion.
A mirror finish of Rmax or less is required.

However, conventionally, para-polishing has been used to finish the inner surfaces of these large towers and tanks, but para-polishing has low productivity during polishing work and has a poor working environment with dust and noise. 0.1 μm, which requires a lot of effort and time.
Mirror finishing below Rmax is virtually impossible. Another possibility is to apply commonly used electrolytic polishing (immersion method), but since immersion electrolytic polishing has low polishing smoothness, a sufficient base finish is required, and at the same time, strong acid electrolytic polishing is required. This is not an effective method because maintenance and management of the liquid is required, and a significant increase in polishing costs is inevitable.

This invention takes the above points into consideration, and provides a method for mirror-finishing the inner or outer surfaces, including the vertical surfaces, of large towers and tanks at low cost and in a safe and hygienic manner. The present invention provides a vertical or horizontal electrolytic composite polishing method for repairing or re-polishing the inner surface of towers and tanks in their existing state at the site. Next, this method will be explained in detail with reference to drawings showing examples thereof.

FIG. 1 shows a tool electrode used in the electrolytic composite polishing method of the present invention, and FIG. 2 shows a model of the polishing principle of the present invention.

The rotating tool electrode 1 is provided with a plurality of radially exposed current-carrying electrodes 2 on one side, an electrolyte spout 3 in the center of the one surface, and a plurality of exposed current-carrying electrodes 2 on one side. An insulating abrasive material 4 is provided in other parts.

This abrasive material 4 is, for example, a non-woven abrasive cloth having elasticity and water permeability, and depending on the finish of the polishing, one with abrasive grains bonded or one with no abrasive grains bonded is selected. . That is, when achieving a mirror finish, use an abrasive material 4 to which no abrasive grains are bonded, and mix abrasive grains 6 into the electrolytic solution 5 so that the abrasive grains 6 are semi-fixed by the abrasive material 4. hold it. The electrolytic solution 5 is a neutral salt aqueous solution, and is pumped by a pump (not shown) to the tool electrode 1.
The electrolytic solution is supplied from the electrolytic solution spout 3 to the polishing section via the water-permeable abrasive material 4. Further, the cathode side of the DC power source is connected to the tool electrode 1, and the anode side is connected to the object to be polished 7. When this tool electrode 1 is rotated and pressed against the object to be polished 7 with a constant force and slides on the object to be polished 7, the object to be polished 7 is subjected to electrolysis and polishing by the abrasive material 4 or abrasive grains 6. (Rubbing) effects work alternately.

That is, a passivation film 8 is generated on the uneven portions of the surface to be polished of the object 7 to be polished by electrolytic action, and only the film on the convex portions is forcibly removed by the abrasive force of the abrasive material 4 or the abrasive grains 6. The electrolytic current is concentrated on the convex portions of the uneven portions of the object to be polished 7, and the convex portions are sequentially and preferentially eluted, so that the surface to be polished is smoothed and a mirror surface is obtained. At this time, the electrolytic solution 5 pumped by the pump is held by the water-permeable and elastic abrasive material 4, and at the same time centrifugal force is applied by the rotation of the tool electrode 1, causing the tool electrode 1 and the object to be polished to Evenly distributed in the abrasive gap with 7.

Therefore, even if the attitude of the tool electrode 1 changes downward, vertically, or upward, the polishing phenomenon is hardly affected, and electrolytic composite polishing can be performed in all positions. Next, the experimental results will be explained.

FIG. 3 shows the results of an experiment to determine the polishing characteristics when the tool electrode position was changed to three positions: downward, vertical, and upward. That is, the tool electrode has a diameter of 150 mm and a current-carrying electrode area of 52 c.
40-50k while rotating at 380rpm using It.
Press it against the object to be polished with gf, and use it as an electrolyte at 20 to 30℃.
A 20% NaNO3 aqueous solution of
Polishing area of approximately 400 cAf)SU with base finishing on ax
When S3l6 is subjected to electrolytic composite polishing, the smoothness of the polished surface relative to the polishing time, that is, the roughness of the polished surface is shown. As is clear from the figure, with polishing time of 3 to 4 minutes in the downward, vertical, and upward directions, the base surface of 5 to 6 μMRmax was polished by 0.1 μm.
Can be polished to a mirror surface with MRmax or less.

As described above, according to the electrolytic composite polishing method of the present invention for large towers and vessels, mirror finishing of large areas of the inner or outer surfaces, including vertical surfaces, of large towers and vessels, which was extremely difficult with conventional methods, can be easily achieved. At the same time, since the polishing posture is free, the tool electrode can be positioned and controlled at any position within the tower and tank, making it possible to perform polishing work in the same state at a low cost even on existing large towers and tanks. It is safe and hygienic, and has great industrial and economical effects.

[Brief explanation of the drawing]

The drawings show an embodiment of the electrolytic composite polishing method for large towers and tanks according to the present invention, in which FIG. 1 is a bottom view of a tool electrode, FIG. 2 is a sectional view taken along line S-S' in FIG. 1, and FIG. is a diagram showing the relationship between polishing time and polished surface roughness. DESCRIPTION OF SYMBOLS 1... Tool electrode, 2... Current-carrying electrode, 3... Electrolyte spout, 4... Abrasive material, 5... Electrolyte, 6...
Abrasive grain, 7... object to be polished, 8... passivation film.

Claims (1)

[Claims] 1. A plurality of radially exposed current-carrying electrodes are provided on one surface of the tool electrode, and an electrolytic solution spout is provided in the center of the surface, and other parts of the surface where the exposed current-carrying electrodes are provided have elasticity and conductivity. A water-based abrasive is provided, and the tool electrode is rotated and pressed against the object to be polished, and an electrolytic solution is ejected from the spout to remove the passivation film generated on the surface to be polished by electrolysis. Among them, the film formed on the convex portions of the uneven portion of the surface to be polished is forcibly removed by the abrasive action of the abrasive or abrasive grains, and preferential elution is promoted and improved on the convex portions. An electrolytic composite polishing method for large towers and tanks, which is characterized by finishing the inner or outer surfaces, including the vertical surfaces, of large towers and tanks that are oriented horizontally or vertically.