JPS5922652B2 - Method for lining metal pipes with flanges - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for lining a metal tube having a flange, and more particularly to a method for lining the inner surface of a metal tube having a flange and the joint surface of the flange with a resin.

BACKGROUND ART Conventionally, metal pipes (for example, steel pipes) whose inner surfaces are lined with synthetic resin have been used as piping materials for chemical plants, particularly for highly corrosive fluids.

These pipes are connected by appropriately combining straight pipes, elbows, cheese pipes, cross pipes, register user →, etc., and the connections are made by screwing or welding the pipe ends. This is done by tightening the flanges together with bolts and nuts. However, in piping for highly corrosive fluids, if not only the inner surface of the metal tube but also the joint surface of the flange is coated with a corrosion-resistant resin, corrosion will occur from this portion, causing problems. Therefore, various methods have been proposed in the past for lining the metal tube with resin from the inner surface to the joint surface of the flange. One of the typical proposals is to line the inner surface of the tubular part of a flanged metal tube with a synthetic resin tube, and within this lined tube, a short thermoplastic resin tube is protruded outward from the lined tube. There is a method in which the protruding portion is inserted and fitted in such a way as to fit the metal tube, and the protruding portion is flanged back along the flange surface of the end of the metal tube.

However, with this method, there is a risk that the short pipe section that is in close contact with the lined pipe may shrink or deform during the subsequent cooling process or during use when high-temperature fluid is passed through. Fluid may enter and cause corrosion of the metal pipe.

In addition, a metal tube is lined with a resin tube, the vicinity of the end of the resin tube is partially peeled off to expose the metal tube, a short resin tube is inserted to cover this exposed portion, and the flange is returned. In addition to doing this, there is a method of welding the butt part of the lining resin pipe and the short pipe. However, this method requires skill in welding the inside of the resin tube, and even a very small number of unwelded areas can cause corrosion. Various other methods have been proposed, but none are industrially satisfactory, especially those with bent parts such as elbows, cheeses, and cashiers, or with varying inner diameters. For joint pipes, an effective method for lining the inner surface of the pipe, including the flange surface, has not yet been established.

The inventors of the present invention have completed the present invention after extensive research in consideration of the current situation. The purpose of this invention is to provide a method for lining a flanged metal pipe that does not cause corrosion or deformation of the lined pipe, and its gist is to line a metal pipe with a flange with resin. In this method, first, the flange surface and the inner surface of the end of the metal tube are closely covered with a flanged short tube, and then a thermoplastic resin tube having an outer diameter smaller than the inner diameter of the metal tube is covered with the metal of the flanged short tube. The thermoplastic resin tube is inserted into a metal tube while covering the inner part of the tube, and a heating medium is introduced into the thermoplastic resin tube to heat it to a temperature higher than the softening temperature of the thermoplastic resin tube, and the internal pressure of the heating medium is increased to convert the thermoplastic resin tube into a metal tube. The method is characterized in that the method is brought into close contact with a pipe.

Hereinafter, the method of the present invention will be explained in conjunction with the accompanying drawings.

The attached drawings show the first embodiment of the method of the present invention in the order of steps, and FIG. 1 is a schematic vertical cross-sectional view showing a state in which short pipes are inserted into both ends of a flanged elbow, and FIG.
The figure is a schematic vertical cross-sectional view of the jig connected to both ends of the elbow in order to line the hex side of the elbow with a resin pipe. Figure 3 shows the lining operation completed and the jig attached to both ends of the elbow removed. It is a vertical cross-sectional front view schematically showing the state. In the figure, 1 is a metal pipe with a flange (elbow in the figure), V is the flange of elbow 1, and 2 is a thermoplastic resin pipe lining the elbow (in this example, a hard vinyl chloride resin pipe (hereinafter referred to as PVC pipe)). (abbreviation) is also used]. 3 is an intermediate plate, 4 is a bolt or nut for tightening the flange, 5 is a register user, 51 and 5'' are flanges installed at both ends of the register user 5, and 5I is the one with the larger diameter of the register user. A flange at the end, 5I is a flange at the end with a smaller diameter of the register user, 6 is a blank flange, 7 is a pipe through which a heating or cooling medium is conducted,
8 is a flanged short tube, and 9 is a resin tube that protrudes from the end of the elbow after removing the jigs at both ends of the elbow after lining the main body.

First, as shown in Fig. 1, elbow 1 undergoes lining processing.
A short flanged pipe 8 is attached to both ends of the elbow 1 to partially cover the joint surface of the flange V and the inner surface of both ends of the elbow 1. This can be done by inserting a short tube with a flange previously formed into this shape, or by inserting a short resin straight tube into the metal tube and letting a part of the short tube protrude from the metal, and then inserting this straight resin tube into the metal tube. It is also possible to soften the material by heating and press it to spread to cover the joint surface of the flange. In this case, it is best to apply adhesive to the short tube and the elbow to bond them together. This short tube may be made of any thermoplastic resin, or may be made of thermosetting resin if it is previously formed into a flanged short tube and then inserted. Next, as shown in FIG. 2, the lined salt pipe pipe 2 is inserted into the elbow 1.

The PVC pipe 2 used has an outer diameter smaller than the inner diameter of the elbow 1, but when lining a bent pipe such as an elbow, the PVC pipe 2 is bent in advance. Then, the intermediate plate 3 is sandwiched between the register user 5 and the flange V of the elbow 1, and the flange 5' of the register user 5 and the flange V of the elbow 1 are connected by tightening bolts. The protruding portion of the PVC pipe 2 is flanged back at the point. Instead of such operation, attach PVC pipe 2 to elbow 1.
When inserting the holder, it is also possible to form a collar on both ends of the holder in advance. In this case, it is preferable to divide the cash register user 5 (and possibly the intermediate plate 3) into two parts. Next, the PVC pipe 2 is fixed with a blind flange 6.

The diameter of the end of the smaller diameter of cash register user 5 is
It is preferable to make it approximately the same size as the outside diameter of the PVC pipe 2. When the jig is attached to both ends of the elbow pipe 1 as described above and the preparation is completed, a heating medium is introduced from one of the next pipes, the medium is discharged from the pipe 7 at the other end, and the PVC pipe 2 is softened. Heat to a temperature above the point.

The heating medium may be a gaseous body such as water vapor or heated air, or a liquid medium. A liquid medium is preferably used in order to automate the heating operation. The liquid medium may be oily, but water-soluble ones such as ethylene glycol and glycerin are advantageous because they are easy to wash afterwards. When the PVC pipe 2 reaches a softening temperature or higher, the internal pressure of the heating medium to be introduced is increased, the diameter of the PVC pipe 2 is expanded, and the PVC pipe 2 is brought into close contact with the inner surface of the elbow 1.

Further, a heat-expandable resin pipe may be used as the PVC pipe 2 (although in this case as well, it is preferable to increase the internal pressure inside the resin pipe in terms of lining adhesion). The intermediate plate 3 has a thickness of, for example, 30Wt1n, and has a large number of through holes with a diameter of 1Wr1n drilled from the inside to the outside. It is useful for expelling.

After increasing the internal pressure of the heating medium and bringing the PVC pipe 2 into close contact with the inner surface of the elbow 1, it is preferable to heat-treat the PVC pipe at a temperature higher than the previous temperature.

This heat treatment prevents the PVC pipe from shrinking during the subsequent cooling process or from deforming during transport of high-temperature fluid during use as a product. This heat treatment can be easily performed by introducing a liquid medium at a higher temperature than the previously introduced high-temperature liquid medium into the PVC pipe, and at this time, the pressure inside the pipe can be maintained at a pressurized state. That's preferable.
Cooling is performed after the Gai treatment process, but in this case as well, it is operationally convenient to conduct a low-temperature liquid medium, and at this time, it is preferable to maintain the pressure inside the resin pipe at a pressurized level.O Each of the above steps The temperature conditions for the lining of a hard pinyl chloride resin pipe are shown below as an example.

Elbow...Outer diameter 216Tfrfn1 Wall thickness 5.8
Tn1 was pre-pickled with 10% sulfuric acid.

PVC pipe...Outer diameter 114TVn1 Inner diameter 94tm First softening of PVC pipe...100-120℃ (for example, 20 minutes at 110℃) Pressurization...Approx. 15mm /
? Heat treatment for 1 minute at 140-160℃, e.g. 150℃ for 1 minute, cooling at 15kf/i...
... 20°C or lower, for example, 15°C for 20 minutes, 15 parts/piece retention or more is when using a hard PVC pipe, but in the method of the present invention, other resins such as polyethylene, polypropylene, vinyl chloride copolymer resin, etc. A tube made of thermoplastic resin can also be used, and conditions such as heating temperature are appropriately selected depending on each resin.

That is, the basic idea is that the first heating temperature is based on the softening temperature of the resin, and the subsequent heat treatment is performed at a higher temperature in order to eliminate internal strain remaining in the molded resin tube. For example, in the case of polyethylene, the first heating is 12
0 to 140℃, second heat treatment is about 50℃
It is best to choose from a range of high temperatures (170 to 190°C). When the above operations are completed and the jigs attached to both ends of the elbow 1 are removed, what is shown in FIG. 3 is obtained, and by cutting and removing the excess protruding resin tube 9, the desired object is obtained.

If necessary, the boundary between this cut point and the short flanged pipe 8 can be closed with a welding rod and finished with a grinder to completely prevent the possibility of highly corrosive liquid entering from the outside. , and since the addition points are on the outside, the operation is easy. The method of the present invention includes flanged straight pipes, cheese,
It can be easily applied to any shape such as an elbow or a cash register user.

The above explanations are only representative examples, and the method of the present invention is not limited to these explanations, and other changes and modifications can be made within the scope of the claims. .

Next, the effects achieved by the method of the present invention will be listed. (
1) The inner surface of the flanged metal tube and the flange joint surface are completely covered with a resin layer.

It is especially easy to line linings that are difficult to coat, such as elbows, bent pipes such as register users, and joint pipes with varying inner diameters. (support) Does not require particularly complex or expensive equipment.

(3) Since the end of the flanged short tube that is inserted into the metal tube is covered with a resin pipe, there is no risk of liquid or gas entering from there. (4) If a thermoplastic resin tube is used as the flanged short tube, it will undergo treatment under the same conditions as the heat treatment and cooling treatment of the thermoplastic resin tube lining the inside of the metal tube body, causing shrinkage and peeling and deformation after the product is finished. The fear of is gone.

[Brief explanation of drawings]

The accompanying drawings illustrate an embodiment of the method of the present invention, and FIG. 1 is a longitudinal cross-sectional front view schematically showing a state in which a short flanged tube is inserted into the end of a metal tube to be lined, and FIG. Figure 3 is a schematic longitudinal cross-sectional view of the metal pipe with jigs for lining the resin pipe attached to both ends of the metal pipe, and Figure 3 is a longitudinal cross-sectional view of the metal pipe with the jigs at both ends of the metal pipe removed after lining the pipe. It is a schematic front view. In the figure, 1 is a metal tube (elbow) to be lined, V is a flange of metal tube 1, 2 is a thermoplastic resin tube, 3 is an intermediate plate, 5
6 is a cash register user, 6 is a blind flange, 7 is a tube for conducting a heating or cooling medium, and 8 is a short tube with a flange.

Claims (1)

[Claims] 1. In a method of lining a metal tube with a flange with resin, first the flange surface and the inner surface of the end of the metal tube are closely covered with a short flanged tube, and then a thermoplastic resin tube having an outer diameter smaller than the inner diameter of the metal tube is coated. is inserted into the metal tube while also covering the inner portion of the metal tube of the flanged short tube, and a heating medium is introduced into the thermoplastic resin tube to heat it to a temperature equal to or higher than the softening temperature of the thermoplastic resin tube, and the internal pressure of the heating medium is lowered. A method characterized by raising the temperature and bringing the thermoplastic resin pipe into close contact with the metal pipe.