JPH029479A - Inner surface coating of long pipe - Google Patents

Abstract

PURPOSE:To spray paint uniformly over the peripheral surface of coating equipment and coat the inner surface of pipe uniformly using the equipment by inserting paint and coating equipment through long pipe and moving the pipe in a longitudinal direction while supporting the rotating coating equipment at a specified position, by the magnetic force given from outside the pipe. CONSTITUTION:After injecting paint 5 into a pipe 1, a shaft-like coating equipment 2 with a slightly smaller diameter than the internal diameter of the pipe 1 is introduced. A magnetic material 20 is embedded in a part of the periphery of the coating equipment 2, and at the same time, a doughnut-like rotary element 3 with a magnet 31 is arranged on the periphery of the pipe which corresponds to a region where the coating equipment 2 is introduced. The coating equipment 2 introduced in the pipe is attracted in the revolving direction of the magnet 3 by allowing the rotary element 3 to rotate, and then is supported, in a rotating state, at a specified insertion position. At that time, if the pipe 1 is moved in a longitudinal direction, the paint 5 flows and spreads uniformly over the inner circumference surface of the pipe 1 by rotation of the coating equipment 2. Thus it is possible to perform the inner surface coating free from harding while the treatment is underway which is the typical disadvantage of the conventional reduction method and without affecting the bending property of the pipe.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a method for coating the inner surface of long metal pipes used for various types of piping, and more particularly relates to a method for coating the inner surface of long metal pipes used in various types of piping. This relates to a method of painting the inner surface of a tube while moving it in the direction.

For example, steel pipes are widely used as various piping materials due to their poor corrosion resistance, processability, and workability. This can cause problems with discoloration of sanitary utensils, etc., so to prevent this, the inner surface of the pipe is coated.

``Conventional technology'' Methods for coating the inner surface of tubes include the inner surface plating method, the welded tube method in which coating material is cradled on the inner surface of the tube, and the inner surface spraying method, but all of these methods are not suitable for coating the inner surface of long tubes. has problems, so recently, for example, JP-A-62-19
The drawing method disclosed in Japanese Patent No. 1077 is employed.

As shown in FIG. 9, the coating method disclosed in the above publication involves supplying a paint 5 made of, for example, a polymeric material into a tube 1, and inserting a floating plug 6 into the tube 1 to accommodate a flow hole 60 for the paint 5. Then, when the tube 1 is passed through the diameter reducing die 7 and drawn out, the paint 5 in the unreduced diameter side 11 of the tube 1 is caused to flow through the flow hole 60 to the already reduced diameter side 12 of the tube 1 as the tube 1 is drawn out. The coating agent 61 in the already reduced diameter side 12 connected to the floating plug 6 disperses and coats the paint 5 on the inner surface of the already reduced diameter (1112) of the pipe 1 to form fills I continuously. .

``Problems to be Solved by the Invention'' Although the painting method using drawing described above is more suitable for painting the inner surface of long pipes than other methods, the pipes undergo work hardening due to the diameter reduction process, which is not required for piping. There is a problem in that the lack of softness significantly reduces workability such as bending, and if an attempt is made to dry this by, for example, annealing, the coating film will be destroyed.

An object of the present invention is to provide a method for coating the inner surface of a long pipe, which is suitable for coating the inner surface of a long pipe and which does not cause work hardening as described above.

"Means for Solving the Problems" In order to achieve the above-mentioned object, the method of the present invention involves inserting a coating tool whose outer diameter is smaller than the inner diameter of the tube into the tube, and applying a magnetic force applied from outside the tube to the coating tool. holding the paint at a certain position inside the tube while rotating it around the tube axis, moving only the tube in a certain direction along the longitudinal direction, and applying paint that has been previously supplied from the painting tool to the rear in the moving direction inside the tube; A method was adopted in which the coating material was caused to flow in the direction of a coating tool, and the coating material was applied to the inner surface of the tube by the coating tool.

In order to rotate and hold the painting tool at a fixed position inside the pipe by a magnetic force acting from outside the pipe, for example, the entire painting tool or a part of the outer periphery is made of a magnetic material such as iron, and at the insertion position of the painting tool, One or all magnets (preferably electromagnets) close to the outer circumference of the tube are revolved around the tube. With this configuration, the painting tool is drawn in the direction of revolution of the electromagnet in a floating state (the peripheral surface of the painting tool is close to the inner peripheral surface of the pipe) at a certain position within the pipe, and the speed of the painting is adjusted to the revolution speed. Rotate together.

Alternatively, a coating tool whose part of the outer circumference facing the inner surface of the tube is made of a magnetic material such as iron is inserted into the tube, and at this insertion position, a large number of T4 magnets are placed close to the outer circumference of the tube. When the magnetic field of each electromagnet is successively changed in a fixed direction, the coating tool rotates in the direction in which the magnetic field changes within the tube.

Before inserting the paint tool into the pipe, inject enough paint into the pipe in advance to cover the entire length of the inner surface of the pipe.Depending on the viscosity of the paint, it is necessary to It is desirable that a suitable dam material be inserted into the pipe prior to this step to prevent the paint from flowing freely between the dam material and the painting tool.

"Operation" According to the method of the present invention, the paint and the m-apparatus are sequentially inserted into the tube,
The paint tool is rotated and held at the insertion position by a magnetic force applied from outside the tube, and when the tube is moved from the side with the paint to the side without the paint with the paint tool as the center, the paint will be in the direction of the paint tool. Pressure is applied to the paint, and the paint gradually enters the gap between the rotating paint tool and the inner surface of the tube. It is more evenly distributed in the direction of , and is applied to the inner surface of the tube with no paint sag and fewer uneven coatings.

According to this method, the diameter of the tube is not reduced when painting the inner surface, so there is no work hardening, and the softness of the tube before painting is maintained almost as it is, without deteriorating workability such as bending.

The thickness of the paint applied to the inner circumferential surface of the tube, that is, the average thickness of the coating film formed on the inner surface of the tube, depends on the moving speed of the tube, the gap between the inner circumferential surface of the tube and the circumferential surface of the painting tool, the viscosity of the paint, and the coating. By appropriately setting the rotation speed of the ingredients, a! If the gap between the inner circumferential surface of the pipe and the coating tool, the viscosity of the paint, and the rotation speed of the coating tool are constant, the faster the moving speed of the tube, the greater the average thickness of the coating film formed on the inner circumferential surface of the tube. Become thin.

“Example” A preferred example of the method of the present invention will be described below with reference to FIGS. 1 and 2.

Insert the paint dam 4 from one end into a pipe (copper pipe) with an outer diameter of 12.7 m and a wall thickness of 0.43 mm, and apply a sufficient amount of silicone resin, etc., to coat the entire length of the inner surface of the pipe 1. After injecting the paint 5 consisting of the following, a shaft-shaped paint tool 2 (made of iron) having an outer diameter smaller than the inner diameter of the tube 1 by about 0.31 is inserted into the tube 1. It is preferable that the coating tool 2 is made of a magnetic material 20 such as a piece of iron with a part of its outer periphery embedded, and the other part is made of a non-magnetic material such as resin.

At the insertion site of the coating tool 2, a donut-shaped rotating body 3 is provided with its inner circumferential surface close to the outer circumferential surface of the tube 1.
As shown in FIG. 2, this rotating body 3 is configured such that a magnet (electromagnet) 31 occupies approximately a quarter of the cross section, and a non-magnetic material 32 occupies the other part. Rotate clockwise in the figure at a rate of 6a times/min.

When the electromagnet 31 revolves around the tube 1 due to the rotation of the rotating body 3, the part of the magnetic material 20 of the coating tool 2 moves toward the electromagnet 3.
While being pulled in the direction of revolution of 1 and rotating at the insertion site,
A gap is maintained between the tube and the inner surface of the tube.

In this state, move the tube 1 to the right in Figure 1 at a speed of 50 m/min, and move the tube 1 to a position (
(right side in FIG. 1) to produce an inner-coated tube a with an average thickness of the inner coating film 51 of about 75 microns and a maximum variation in coating film thickness of 10 microns.

As the tube 1 moves, pressure is applied to the paint 5 on the left side of the coating tool 2 in Figure 1, and the rotation of the coating tool 2 causes the paint 5 to flow and disperse more uniformly toward the inner circumference of the tube 1, resulting in coating. The coating is applied almost uniformly to the inner circumferential surface of the tube by the circumferential surface of tool 2. Therefore, it was possible to continuously form the coating 11!51 on the inner surface of the tube 1 without any trace of paint dripping or uneven coating.

The softness of the manufactured inner-coated tube a was almost the same as that of the unpainted tube 1, and no deterioration in workability such as bending was observed as in conventional tubes whose inner surfaces were painted while being drawn.

The damming material 4 is not essential and can be used selectively depending on the viscosity of the paint 5.

A conical or truncated conical paint diffusion portion 21 may be formed at the tip of the coating tool 2 as shown in FIG.

The coating tool 2 may have a ball shape or other shapes in addition to the ring shape described above, as long as the peripheral surface is uniformly close to the inner peripheral surface of the tube 1 and can rotate within the tube 1 as described above. However, it can be implemented.

The electromagnets 31 in the rotating body 3 can be implemented by, for example, providing a plurality of electromagnets at regular angular intervals as shown in FIG. 4 to rotate the tube 1, or as shown in FIGS. ,
It is also possible to construct the rotating body 3 by attaching a plurality of electromagnets 31 between the donut-shaped rotating plates 33 and 33.

Furthermore, as shown in FIG. 8, a coating tool 2 made of a non-magnetic material with a magnetic material 20 such as an iron piece embedded so as to face the outer periphery.
is inserted into the tube 1, and at this insertion position, a large number of Mt magnets 31 are arranged close to the outer periphery of the tube 1 at equal angular intervals, each electromagnet 31 is supported by a support plate 34, and the magnetic field of each electromagnet 31 is For example, it can be implemented by sequentially changing in the direction of arrow A in the I'8ff diagram.

That is, in FIG. 8, when the magnetic field of each electromagnet 31 is sequentially changed in the direction of rotation as shown by arrow A, 'j
4 Magnetic material 2 of paint tool 2 in the direction of change of magnetic field of magnet 31
0 is pulled, and the coating tool 2 is rotated in that direction but held in the state shown.

"Effects of the Invention" Unlike the conventional inner surface painting method using drawing, the inner surface coating method according to the present invention does not use a floating plug to perform inner surface coating at the same time as the diameter reduction process, but simply moves the pipe in a fixed direction. Since the inner surface can be coated while the pipe is being coated, the inner surface can be coated without work hardening of the pipe and without deteriorating workability such as one bending process.

In addition, in conventional inner surface painting by drawing, if paint breaks inside the pipe during painting, the lubrication between the plug and the inner surface of the pipe may be lost and the pipe may break, but the coating method of the present invention prevents paint breaks. Even if this happens, there is no risk of the pipe breaking.

[Brief explanation of the drawing]

1 [:l is a sectional view showing an example of an apparatus for carrying out the method of the present invention, 9s2 is a longitudinal sectional view taken along the arrow A-A line in Fig. 1, and Fig. 3 is a sectional view showing a modified example of the coating tool. 4 and 5 are longitudinal cross-sectional views showing other examples of the apparatus for carrying out the method of the present invention, Section 6 is a cross-sectional view taken along the arrow B-H in FIG. 5, and FIG. 7 and FIG. FIG. 8 is a longitudinal cross-sectional view showing another example of an apparatus for carrying out the method of the present invention, and FIG. 9 is a cross-sectional view for explaining a conventional painting method. In the figure, the main symbol l is a tube, 2 is a paint tool, 20 is a magnetic material, 3 is a rotating body, 3
1 is an electromagnet, 32 is a non-magnetic material, and 33 is a rotating plate. 34 is a support plate, 4 is a dam, 5 is a paint, and 51 is a coating.

Claims (1)

[Claims] A painting tool whose outer diameter is smaller than the inside diameter of the tube is inserted into the tube, and the painting tool is held at a certain position inside the tube while rotating around the tube axis by a magnetic force applied from outside the tube, and only the tube is painted. While moving in a fixed direction along the longitudinal direction, paint previously supplied from the painting tool toward the rear in the direction of movement within the pipe is caused to flow toward the painting tool, and this paint is applied to the inner surface of the pipe by the painting tool. A method for painting the inner surface of a long pipe, characterized by: