JPH0423154B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for welding and joining lined steel pipes, which provides a joint that is excellent in strength and exhibits high performance in terms of corrosion resistance and wear resistance.

Initially, lining steel pipes were joined by flange joints as shown in Figure 3, but this method cannot eliminate the risk of leakage and is virtually impossible to apply to underground piping. Therefore, in recent years, joining methods by welding have attracted attention, and various proposals have been made regarding such methods. Some representative examples are as follows.

(i) As shown in Fig. 4, a joining member 11 having a large diameter part and a small diameter part is welded to the outer peripheral surface of each end of the pipes 1, 1' to be joined.
A method of joining by butt welding the large diameter ends of the joining members 11, 11 while facing each other with the lining layers 5, 5 sandwiched between them. It is called a bridge type joint.

(ii) As shown in FIG. 5, an expanded portion is provided at each end of the pipes 1 and 1' to be joined by butt welding with a reducer 12, and the inner cavity of the expanded portion is filled with a heat insulating material 13. A method of lining 5 and butt welding the expanded pipe parts together.

(iii) As shown in Fig. 6, inner lining 5 is applied to the pipes 1 and 1' to be joined, leaving the necessary range at the ends, and after joining these two pipes together by butt welding, the unlined parts are Heating means 14 at 5'
A method of performing repair lining in which resin injected through the through hole 15 is cured in accordance with the above.

(iv) As shown in Fig. 7, the ends of the pipes 1, 1' to be joined are expanded and the inner surfaces of the expanded parts 16, 16 are lined with a rust-proof metal plate 17 (ring-shaped).
18 are brought into contact with each other, the pipe ends are butt welded, and then the gaps 19, 1 between the rust-proof metal plate 17 and the existing inner linings 5, 5 are closed.
9 is painted.

However, all of these conventional methods have their own problems and are not sufficient for practical use. That is, () method (i) shown in FIG.
Since these are fixed to the outer surfaces of the tubes 1 and 1' by so-called fillet welding, there is concern about the strength of the joints. In addition, the joining members 11, 11
Although the welding is performed at a location away from the pipes 1, 1' themselves, there is a risk that the welding spatters may damage the lining parts 5a, 5a, which are folded between the pipe ends at the pipe butting position. If this still occurs and the butt sealing performance of the lining in the same area is impaired, the fluid inside the pipe will leak to the outside, resulting in peeling of the lining from the end of the pipe and corrosion of the pipe itself.

() The method (ii) shown in Fig. 5 has problems in the adhesion between the heat insulating material 13 in the pipe expansion part and the lining 5 inside it, as well as in the butt sealing performance of the lining, and it is difficult to prevent leakage of the fluid in the pipe. do not have.

() Even with method (iii) shown in Figure 6, in reality it is difficult to construct repair lining after pipe joining.
Furthermore, the lining of the repaired area is unreliable in terms of adhesion.

() In method (iv) shown in Fig. 7, painting the inner surface after joining the pipes is time-consuming, and the resulting coating is also unreliable.

<Objective of the invention> The present invention has excellent strength, and there is no deterioration of the inner lining due to the influence of joint welding of pipes.
An inner-lined steel pipe that can stably produce a joint that exhibits performance comparable to the original pipe in terms of corrosion resistance and wear resistance, and is low-cost and does not require troublesome inner-lining repairs. The present invention aims to provide a welding and joining method.

<Structure of the Invention> The gist of the present invention is as follows.

An expanded section is provided at the ends of both tubes to be joined, and a ring body having an inner diameter approximately the same as that of the original tube section is inserted into each of the expanded sections, and one end of the ring body is welded to the inner surface of the inclined section of the expanded section. , in a state where both expanded pipe parts are abutted, the ring bodies face each other at a certain distance at a required distance in the tube axis direction from the abutting position of the expanded pipe parts, and form a predetermined space between them and the inner surface of the expanded pipe parts. Then, a lining is applied to both of the tubes to be welded so as to continuously cover the inner surface of the original tube, the inner surface of the ring body, and the open end thereof, and then the open end of the ring bodies are lined with each other. With the lining layer sandwiched between them, the expanded tube parts are butt-welded and joined together, and then the space between the expanded tube part and the ring body is injected and filled with resin through the injection hole prepared in advance. A method characterized by plugging the injection hole.

In the above method, only one ring body is used, and the ring body is inserted and installed only in the expanded tube part of the pipe to be joined on one side, and the tip of the ring body is placed in correspondence with the inclined part of the expanded tube part on the other side, and both expanded tube parts are This method involves butt welding the pieces together.

In other words, the method of the present invention is an improvement on the so-called bridge type joint method, which uses a connective member 11 in the form of a reducer, as shown in FIG. Instead of fillet welding, we decided to provide an expanded section at the end of the tube and provide a ring body as a separate tube inner surface forming material inside the expanded section. In order to avoid the influence of welding by shifting the ring in the axial direction, we also filled the space with the expanded pipe outside the ring body with resin in order to prevent the fluid inside the pipe from leaking from the joint of the lining. The above are the major improvements.

<Example> Hereinafter, the joining method of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a vertical cross-sectional side view of the upper half showing one of the joining methods of the present invention, and this figure shows a joint portion that has been joined. In the figure, 1, 1' are pipes to be joined, 2,
2' is the expanded tube added to the joint end, and 3, 3' is the original tube part (other than the expanded tube) 4 whose inner diameter is the tube to be joined.
5 is a resin lining,
6 is a filling resin.

That is, in the method of the present invention, pipes are joined as follows.

First, enlarged portions 2, 2' are provided at the ends of the pipes 1, 1' to be joined. As a means for providing a tube expansion section, it is common to set a core metal whose diameter can be expanded or contracted by hydraulic pressure or the like into the tube end and press it to expand. In this case, the expansion rate and length of the expanded part will of course vary depending on the usage conditions and pipe conditions, but the expansion rate is approximately 5 to 15%, and the length of the expanded part (including the inclined part 2a) is 150 to 300 mm. The degree would be appropriate. Note that the present invention may be applied to seamless pipes, electric resistance welded pipes, etc. In the case of electric resistance welded pipes, careful attention must be paid to seam annealing of the electric resistance welded portion, changes in tube length due to tube expansion, thinning, and roundness.

In addition to the tube expansion operation described above, a method using a reducer may be used as a method for providing the tube expansion portion. In the case of this method, the reducer used should have the same inner and outer diameters as the inner and outer diameters of the pipe to be joined, and the reducer should be attached to the pipe end by butt welding. is the important thing. This is an essential condition in terms of joint strength.

Next to such expanded tube portions 2, 2', ring bodies 3, 3' are inserted and fixed. ring body 3,
3', the inner diameter d is the same as or slightly larger than the inner diameter D of the original tube part 4, and the outer peripheral edge of one end 3a is cut diagonally into a chamfer shape, and this surface 3b continues to the expanded tube part and the original tube part. The end face 3c and the inner surface of the inclined portion are fixed by circumferential welding from the inside by abutting against the inner surfaces of the inclined portions 2a and 2a'. The welded portion 7 is finished smooth using a grinder or the like.

Here, it is important that the lengths l and l' of the ring bodies 3 and 3' are not the same but different from each other. That is, in the state where both expanded tube portions 2 and 2' are abutted, the ring bodies 3 and 3' are arranged to face each other at a constant interval at a position deviated from the expanded tube portion abutting position A in the tube axis direction. The spacing between the ring bodies 3 and 3' is such that folded portions 5a and 5a of the lining, which will be described later, are interposed therebetween (specifically, about 3 to 10 mm). In such a structure, the corresponding position B (indicated by the abutting position of the linings) of both ring bodies is moved away from the abutting position A of the tube expansion part, and the linings (folded parts) 5b, 5b near the above B position are welded at the A position. The purpose is to avoid being influenced by Therefore, B
The position is set at a location where spatter caused by welding at the A position can be avoided.

Apart from using a set of ring bodies like this, there is also a method of using only one ring body. An example is shown in FIG. That is, the ring body 3 is attached to only one of the pipes 1 to be welded in the same manner as described above, and the ring body 3 is attached to the inclination of the pipe 1' to be welded on the other side while the expanded pipe parts 2 and 2' are abutting each other. Part 2
lining 5, which will be described later, between them on the inside a′
a and 5 so that they face each other with a gap between them.

In either case of FIG. 1 or FIG. 2, a space M continuous in the circumferential direction is formed between the ring body 3, 3' or 3 and both expanded tube portions 2, 2'.

In addition, the space M
Provide at least two holes 8 communicating with. This is for injecting resin into the space M after the pipes are joined, and in order to securely close the space M after the resin is injected, the tapered thread is cut so that it can be closed with a plug 9. Note that this drilling work may be performed before or after the attachment of the ring body.

The pipe to be joined in this way is then lined. In the case of FIG. 1, the lining 5 is folded outward from the inner surface of the original tube part 4 to the inner surface of the ring body 3, and further outward at the open end 3d (hereinafter referred to as the tip) of any pipe to be joined. It is folded back to the side and is provided so as to continuously cover the tip of the ring. In the case of FIG. 2, the one with the ring body 3 is the same as above, but the other is provided so as to cover the original tube part 4 and the inclined part 2a of the expanded tube part up to the position facing the ring body. A ring-shaped collar 10 may be attached as a stopper for the folded portion 5b on the side of the ring body tip 3d of the lining. Note that any currently known lining resin may be used. Examples include tar epoxy, epoxy, polyurethane elastomer, natural neoprene rubber, polyethylene, vinyl chloride, nylon, and the like.

The above steps are carried out in advance at the factory.

At the site, the expanded tube portions 2, 2' of the pipes 1, 1' to be joined are butt-welded to each other.
During welding, the inner ring bodies 3 and 3' as shown in FIG. 5a, 5a or 5
Position a and 5 so that they correspond.
At this time, the linings are made to have a tendency to come into pressure contact with each other so as to maintain sealing properties between the linings.

Even if such welding is performed, the folded portion 5a of the lining is not affected by any displacement in the tube axis direction with respect to the welding position A.

When the welding is finished, the holes 8, 8 provided in the expanded pipe section are opened by removing the plugs 9, 9.
The resin is injected into the space M through one of the holes to fill it. In this case, it goes without saying that the other hole functions as an air vent. As the resin to be filled, a type that has an injectable viscosity and hardens at room temperature, such as a room temperature curing polyurethane resin, is used.

After resin injection, plug 9, 9 into both holes 8, 8.
Tighten and secure, and the joining is complete.

<Effects of the Invention> According to the method of the present invention as described above, a joint having the following features and advantages can be realized.

(i) It has excellent pressure resistance inherent to a welded structure, and can be buried underground, which is impossible with joints such as flange joints.

(ii) The force in the direction of the tube axis is not received by the fillet welds as in conventional bridge-type joints, and compared to bridge-type joints, it is much stronger against external forces such as bending and tension.

(iii) The inner lining is not affected by pipe joint welding;
In addition, resin is filled around the ring body as the tube inner surface forming member and between the expanded tube section and the tube section, and in terms of corrosion resistance and abrasion resistance, it exhibits performance that is even superior to the original tube section.

(iv) Not only is it cost-effective compared to conventional flanges or victrics, but it is also extremely easy to install on-site, as it only requires resin injection, which requires no special skills other than welding. It is.

(v) It is easy to implement anti-corrosion measures on the external surface of the joint.

Therefore, the present invention greatly contributes to improving the joint performance of internally lined steel pipes, reducing construction costs, etc.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional side view of a joint section showing one embodiment of the joining method of the present invention, FIG. 2 is a vertical cross-sectional side view of the same showing another embodiment of the joining method of the present invention, and FIGS. 3 to 7 shows five types of conventional joint structures for internally lined steel pipes; FIG. 3 shows an example of a flange joining method, and FIGS. 4 to 7 each show an example of a welded joint. In the figure, 1, 1': pipe to be joined, 2, 2': expanded pipe part,
3, 3': Ring body, 4: Original pipe section, 5: Lining, 6: Filled resin, 7: Welding section, 8: Hole, 9: Plug, 10: Collar, 11: Joining member, 12: Regenerator, 13 : heat insulating material, 14: heating means, 1
5: injection hole, 16: tube expansion part, 17: rust-free metal plate, 18: backing plate.

Claims (1)

[Scope of Claims] 1. Expanded portions are provided at the ends of both steel pipes to be joined by expanding the pipe or attaching a reducer by butt welding, and each of the expanded portions has an inner diameter approximately equal to that of the original pipe of the pipe to be joined. An equivalent ring body is inserted and one end of the ring body is welded to the inner surface of the inclined part of the expanded tube part, and when both expanded tube parts are abutted, the ring bodies are fixed at a required distance from each other in the tube axis direction from the abutted position of the expanded tube part. Then, the inner surface of the original tube, the inner surface of the ring body, and the open end thereof are connected to both such tubes to be joined. A lining is applied so as to cover the ring body, and then the open ends of both ring bodies are butt welded and joined together with the lining layer sandwiched between the open ends of the ring bodies, and then the previously provided A method for welding and joining inner-lined steel pipes, which comprises injecting and filling the space between the pipe expansion part and the ring body with resin through the injection hole, and plugging the injection hole. 2. Provide an expanded section at the ends of both steel pipes to be joined by expanding the pipe or attaching a reducer by butt welding, and attach a ring body to one of the expanded sections, the inner diameter of which is approximately the same as the inner diameter of the original pipe of the pipe to be joined. One end is inserted and the inserted end is welded to the inner surface of the sloped part of the tube expansion part, and when both expansion parts are abutted, the ring body is placed on the inner surface of the slope part of the other pipe to be joined at a required distance. and facing each other and forming a predetermined space between the inner surfaces of both expanded tube parts, and then on both tubes to be joined,
The one with the ring body continuously covers the inner surface of the original tube, the inner surface of the ring body, and the open end thereof, and the other one covers the inner surface of the original tube including the part of the slope facing the ring body. As shown in FIG. A method for welding and joining inner-lined steel pipes, characterized by injecting and filling the space between both expanded tube parts and the ring body with resin through the injection hole provided, and plugging the injection hole.