KR910004613B1 - Method of cleaning the inner surfaces of metal pipes of ring or coil form - Google Patents

Abstract

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Description

Cleaning method of inner surface of annular metal pipe

The present invention relates to a method of washing the inner surface of an annular metal tube with a liquid detergent or a special container solvent, and when the detergent flows through the entire length of the tube, the detergent is attached to the tube wall, so that the attached detergent is evaporated. It relates to a method of washing by.

It is already known that corrosion of copper tubes used in the sanitary field is in most cases caused by carbon adhering to the inner surface of the tubes. The carbon film thus attached is caused by, for example, pyrolysis of a drawing agent added when the tube is drawn. Soft pipes that are annealed after the final drawing process produce pyrolysates as quickly as the soft anneal process. However, even in an unflammed hard tube, such a harmful carbon film is produced even when the tubes are heated to bend each other by brazing or to bend easily.

When grease of 0.1 mg / dm ² or less was present on the inner surface of the tube, it was found that the carbon film formed during heating was almost harmless.

In order to remove the retaining film attached to the inner surface of the tube, a degreasing agent such as perchlorethylene or trichlorethylene is circulated in the tube, and then the inside of the tube is dried by purifying hot air to evaporate the remaining degreasing agent. Known. This method can guarantee very good degreasing but is too costly because the time is too long and the normal tube manufacturing process is interrupted.

A method of introducing water vapor into a tube and adding a predetermined amount of degreasing agent to the tube once or several times has also been proposed. However, in this treatment method, not only has it been found that the holding film can be reduced to the desired degree but only when the treatment process is repeated many times, and it is also obvious that this method is uneconomical.

Accordingly, it is an object of the present invention to provide a method for cleaning the inner surface of a metal tube such that the holding film is 0.1 mg / dm 2 or less in an economical way to solve the above-mentioned disadvantages of the prior art.

The object is the first step of introducing a predetermined amount of detergent into the tube from one end of the tube according to the present invention; Inserting a plug occupying the cross sectional area of the tube at the end of the tube and pressing the plug to move over the entire length of the tube, thereby pushing the detergent in front of the tube; It is achieved by a method of washing the inner surface of a metal tube comprising the step of allowing the pressure inside the tube to be reduced. The detergent is preferably an organic solvent such as, for example, perchlorethylene or trichlorethylene.

Using the method according to the invention it is possible to clean the tube with only a small amount of solvent, for example 3 to 5 liters of solvent. Here, the speed of the plug moving through the tube must be fast enough that the detergent contacts the entire surface of the tube. After the plug has passed through the pipe, the connection between the pipe and the pressure generator is interrupted and the pressure already generated is slowly reduced. For example, in the case of using a solvent such as perchlorethylene or trichlorethylene, in order to prevent harm to the health, it is preferable to remove by sucking the pressure medium containing the solvent vapor flowing out from the tube end. The pressure medium is advantageously nitrogen.

Detergents are transported along the wall of the tube on a highway, creating a toy that degreases it by removing grease even in the smallest grooves on the tube surface. In addition, the film of detergent remaining behind the plug in the perfusion direction becomes very thin, and after the detergent is evaporated, the remaining film of fat or oil (dissolved in the detergent film) becomes thinner than 0.1 mg / dm 2 on the tube surface. In carrying out the present invention in order to obtain such an extremely thin membrane, it is preferable to use a plug made of a porous material, preferably a felt plug, and the diameter of the plug is preferably slightly larger than the inner diameter of the tube. When the plug comes into contact with the detergent, the plug absorbs the detergent and, because of its larger diameter than the tube, strongly cleans the inner surface of the tube, leaving the film of detergent remaining as thin as desired. The ratio of the diameter length to the diameter of the felt plug is preferably 1.1 to 2.0.

The above washing conditions can be achieved even if the method according to the invention is used only once. This method may be used repeatedly if the remaining amount of these requirements is lower. If the dry felt plug is inserted into the tube immediately after the detergent and the plug are removed from the tube, the oil adhered to the inner surface of the tube is 0.1 mg. It can be / dm <2> or less. The detergent film attached to the wall of the tube is removed by dry felt plugs.

Another advantage of the method according to the invention is that the copper pangle formed as a result of the drawing process is also removed from the inner surface of the tube.

Hereinafter, the present invention will be described in detail through examples.

First, 5 liters of clean trichlorethylene is introduced into a metal tube, especially a copper tube, wound in an annular bundle shape having an outer diameter of 15 mm, a wall thickness of 1 mm, and a total length of about 1000 m. A felt plug having an outer diameter of 14 mm is pressed into the tube from the inlet end of the tube, and the tube end is connected to a pressure generator, preferably a high pressure nitrogen containing vessel. The pressure in the nitrogen containing vessel is about 20 bar. As soon as the valve of the nitrogen container is opened, the felt plug moves the tube in a threaded manner at a speed of 6-7m per second. As the plug is transported, the felt plug pushes the detergent forward so that the detergent cleans the entire inner surface of the tube. When the solvent and plug are removed from the tube, the connection between the nitrogen container and the tube is blocked. Nitrogen containing solvent flows out from both ends of the tube. Once pressure equilibrates (this process lasts about 2 minutes). The tube is completely dried. The tube is then cut straight to a suitable length through a straightening process.

Before the tube was treated in the same manner as described above, the holding content of the inner surface of the tube was 5 mg / dm 2, and after the treatment, the holding content was reduced to 0.06 mg / dm 2. This extremely low retention is uniform over almost the entire length of the tube.

In the embodiment described above, nitrogen was used as the pressure medium. However, other mediums of high pressure may be used, for example compressed meat, in which case such care should be taken to ensure that the medium is free of oil.

Claims (3)

In the cleaning method of the inner surface of the cyclic metal tube, a liquid detergent or an organic solvent passes through the entire length of the tube and then evaporates the detergent attached to the inner wall of the cyclic metal tube. Inflow into the; Inserting a plug occupying the cross sectional area of the tube at the end of the tube and pressing the plug to move over the entire length of the tube, thereby pushing the detergent in front of the tube; Washing the inner surface of the annular metal tube, characterized in that it comprises the step of reducing the pressure in the tube. The method of claim 1, wherein the plug is made of a porous material, the diameter of which is slightly larger than the inner diameter of the tube. 3. The method of claim 1 or 2, wherein the plug has a length and a weaving ratio of 1.1 to 2.0.