JPH0751231B2 - Resin coating method on inner surface of tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a method of coating a resin on the inner surface of a pipe by a fluid immersion coating method.

<Prior Art> Metal pipes, such as steel pipes, may be internally coated to impart chemical resistance and corrosion resistance to transport liquids, and powder coating may be used as one of the coating methods. . That is, the metal tube is heated, the coating gun is reciprocated in the heated metal tube, and the nozzle at the tip of the gun is rotated. It may adhere evenly.

<Problems to be solved> By the way, it is not suitable to apply the powder coating method of the nozzle method to a short pipe such as a bend pipe or a straight short pipe used for connecting a metal pipe, and the same powder is used. It is appropriate to use the fluid immersion coating method which belongs to the body coating method.

However, in order to coat the resin only on the inner surface of the bend pipe, the short pipe or the like by the fluid immersion coating method, it is necessary to mask the outer surface of the bend pipe. However, in the fluid immersion coating method, it is necessary to heat the object to be coated to a temperature equal to or higher than the resin melting temperature and then to immerse the object to be heated in a powder resin fluid tank, which is heated to a high temperature. In contrast, the use of adhesives is practically impossible. Therefore, there are restrictions on masking, and masking is extremely difficult. Even if masking is possible, when heating the masking tube (usually by a heating furnace), the air layer between the masking and the tube causes adiabatic action and reduces the heating efficiency of the bend tube. Further, a leak of expanded air occurs, and the powder resin easily intrudes from this leak point during dip coating.

An object of the present invention is to provide a resin coating method on the inner surface of a metal short tube by a fluid immersion coating method, which can be applied with good metal tube heating efficiency and simple masking or covering work. To provide.

<Means for Solving the Problems> The resin coating method for the inner surface of the pipe according to the present invention is a method in which a guide tube is attached to one end of a heated inner surface coated pipe body, and the inner diameter and the length of the coated pipe body are The tip of the tubular cover, which is larger than the outside diameter and the length, is attached to the other end of the tubular body to be coated, and the guide tube is brought out from the rear end of the tubular cover. The configuration is characterized in that the rear end of the cylindrical cover is held in a state of being raised above the powder resin flow surface in the fluid tank, and the powder resin is attached to the inner surface of the pipe.

<Description of Embodiments> Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The drawing shows a fluid resin coating device used in the present invention.

In the figure, reference numeral 1 indicates an inner surface coated metal pipe body (elbow joint).
And has flanges at both ends. Reference numeral 2 denotes a guide pipe, which is attached to one end of the pipe body 1 to be coated. Reference numeral 3 denotes a tubular cover, the inner diameter of which is larger than the outer diameter of the pipe body 1 to be coated and the length of which is longer than the length of the pipe body 1 to be coated. The tubular cover 3 is attached to the other end of the pipe body 1 to be coated at its tip. 4 is a hanger attached to the guide tube 2, 5 is a regulating valve provided on the guide tube 2, 6 is a cyclone,
7 is an exhaust pump. 8 is a fluidized tank.

To coat the resin on the inner surface of the tube according to the present invention, first,
The metal tube 1 is heated, the tip of the guide tube 2 is attached to one end of the heated metal tube 1, and then the tubular cover 3 is attached to the other end of the tube 1.

In this manner, the guide tube 2 and the tubular cover 3 are attached to the tube body 1.
Then, the assembly is dipped into the powder coating fluid tank 8 by the operation of the hanger 4, and the rear end 30 of the tubular cover 3 is exposed above the powder resin fluid surface A. Keep it. As a result of this immersion, the powdered resin in the floating fluid state in the tank 8 is
The air inside the pipe body 1 is exhausted through the guide pipe 2. In this case, since the joint portion B between the pipe body 1 and the guide pipe 2 is located below the powder resin flow surface A, the powder resin exceeds the upper end in the pipe body 1 and Powdered resin can be attached to the inner surface. On the other hand, since the upper end 30 of the tubular cover 3 is exposed above the powder resin flow surface A and the upper end of the tubular body 1 is guided to the outside of the tubular cover 3 by the guide tube 2, No infiltration of the powder resin into the tube can occur, and no resin adheres to the outer surface of the tube. Therefore, the resin can be coated only on the inner surface of the tubular body 1.

In the above, the guide pipe 2 is driven by driving the exhaust pump 7.
It is also possible to suck the inside and cause the powdered resin in the tube body 1 to flow in the tube axis direction. In this case, it is desirable to collect the powder resin by, for example, a cyclone 6.

In the above, the preheating temperature of the metal tube 1 varies depending on the melting point of the powder resin, but in the case of nylon resin, for example, 250 ° C
Is. The immersion time in the fluid tank 8 varies depending on the size of the pipe body, but is about 5 to 10 seconds in the case of a metal pipe having an inner diameter of 50 mm and a length of 500 mm. When sucking the inside of the tube 1, the degree of pressure reduction is about −
It is 200 mmHg. After taking out the resin-coated tube 1 from the dipping tank 8, it is effective to lightly blow the inside of the tube 1 and reheat the tube 1 to make the thickness of the adhered resin uniform. .

In the above, after preheating the metal tube 1, it is important to prevent the heat radiation, and it is important for the preheated metal tube to be immersed in the fluid tank 8 as short as possible. It is desirable to attach the tube 2 and the tubular cover 3 to the metal tube body 1 with one touch. For example, a magnet is used for the flange of the guide tube and the end plate at the tip of the tubular cover. The metal tube end flange can be magnetically coupled. In order to prevent the heat of the heated metal pipe body from radiating through the guide pipe or the tubular cover, use a heat insulator for the guide pipe body or the tubular cover body, or between the flanges or between the flange and the end plate. It is preferable to interpose a sheet-shaped heat insulator.

<Effects of the Invention> As described above, according to the resin coating method for the inner surface of the tube according to the present invention, the tube is heated, the tubular cover and the guide tube are attached to the heating tube, and then these It is possible to coat the resin on the inner surface of the tubular body simply by immersing the combined body in the fluid tank, and the tubular body is heated by the tubular body alone, so the tubular body can be efficiently heated. The attachment of the tubular cover to the heating tube and the attachment of the guide tube to the heating tube are easier and easier than the task of masking the entire outer surface of the heating tube with a heat-resistant sheet. Because it is obtained, workability is also excellent.

[Brief description of drawings]

The drawings are explanatory views showing a resin coating device used in the present invention. 1 ... Tube, 2 ... Guide tube 3 ... Cylindrical cover, 8 ... Powder resin fluid tank A ... Powder resin fluid surface

Claims (1)

[Claims] 1. A guide tube is attached to one end of a heated inner pipe to be coated, and the tip of a tubular cover having an inner diameter and a length larger than the outer diameter and length of the pipe to be coated is to be coated. The guide tube is attached to the other end of the body and the guide tube is pulled out from the rear end of the tubular cover, the tubular body with the tubular cover is placed in the powder resin flow tank, and the rear end of the tubular cover is attached to the powder resin flow surface. A method for coating a resin on the inner surface of the pipe, characterized in that the powder resin is attached to the inner surface of the pipe while being held in a state of being raised above.