JPS61256087A - Method and device for connecting steel pipe - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to improving the quality of joints and saving labor when a large number of steel pipes, such as water pipes, are connected by welding.

[Prior art] When a large number of steel pipes are connected together and laid underground or exposed for water supply, sewage, power generation, and other water transmission purposes,
Regardless of the diameter, paint is applied to the inner surface or both the inner and outer surfaces of the pipe to improve corrosion resistance.

Traditionally, the inner surface is based on coal tar enamel,
The outside surface is wrapped with glass cloth and coated with coal tar enamel.

This is because, without the presence of these paints, the steel pipe material would gradually corrode and its service life would be significantly shortened.

This coating is applied uniformly and completely using a centrifugal force method at a steel pipe manufacturing factory, but when welding the ends of two or more steel pipes together, the paint around the ends is eroded by the welding heat. Because it burns out, melts off, or cracks and peels off, it must be painted on-site after welding to maintain the desired coating layer.

For this purpose, after welding is completed, it is necessary to thoroughly polish the parts with a grinder to ensure good adhesion of the enamel, and to thoroughly clean the parts to ensure that no moisture or oil remains.

Moreover, such a process after welding is extremely difficult on the inner surface of a small-diameter steel pipe, and even on the outer surface of a large-diameter steel pipe, when the gap between the top wall of the tunnel and the outer periphery of the steel pipe is small when installed in a tunnel. The work is difficult.

In order to solve these problems, there is a ``coated steel pipe'' proposed by the applicant (Japanese Utility Model Publication No. 38-2351).

As shown in Fig. 10, this idea involves applying a prescribed paint to the inner and outer surfaces of the steel pipe 1a, leaving both ends intact to form a coating layer 2a, and forming a lining layer of stainless steel plates near the unpainted inner ends. 30, and both end surfaces are cut obliquely from the inner surface to the outer surface of the steel pipe 1a.

When performing on-site welding, the ends of two adjacent steel pipes are brought together to form a V-shaped groove between the slopes, and the welded part 31 is first applied from the outside using a stainless steel welding rod at the bottom of the groove. The outer end of the steel pipe 1a is welded with a mild steel welding rod to form a welded portion 5a.

After welding, a desired coating 32 is applied to the unpainted outer surface of the end of the steel pipe 1a.
Since the inner surface is already lined with corrosion-resistant stainless steel plate F130TFI9, there is no need to paint it on site.

[Problems to be Solved by the Invention] The above-mentioned prior art certainly avoids painting the inner surface end of the tube, which is difficult to perform on-site.

However, it requires a very high level of technique to completely perform ordinary Uranami welding on stainless steel welded parts without using a backing metal.

Therefore, in the case of normal arc welding, a backing metal must be placed on the inner surface, and if this backing metal cannot be removed after welding and remains in the pipe, it will create resistance in the flow path and cause crevice corrosion. Cheap.

In addition, in order to avoid this, inert gas welding requires special equipment, which creates various bottlenecks such as space, transportation, and skilled personnel.

Furthermore, even if stainless steel welding is completed successfully, it is impossible to completely remove the stress after welding because it is necessary to carry out on-site construction.
In that case, there is a risk of stress corrosion cracking occurring between grains, and electrolytic corrosion due to the formation of local batteries between mild steel and stainless steel in a corrosive atmosphere is also not possible.

Furthermore, this conventional technology targets small-diameter steel pipes and specifies that only the inner surface is not painted on-site, but as mentioned above, it is sometimes difficult to paint the outer surface of the pipe on-site, and this does not solve the problem.

Lining the end of the steel plate with a stainless steel plate itself requires a considerable increase in the process, and it is difficult to weld the steel pipe on-site.
Several problems remain, including quality concerns and the risk of water leakage if defects become apparent during use.

In order to solve the above-mentioned problems, the present invention provides a new connection method that can omit on-site painting of both the inner and outer surfaces when welding a large number of steel pipes on-site, and a connection device used to implement the connection method. The purpose is to

[Means for Solving the Problems] The method for connecting steel pipes according to the present invention involves applying a ceramic coating 3 to the pipe surface near both ends of the steel pipe 1, and applying a predetermined paint 2 to the pipe surface other than those portions. Two ceramic coated tubes forming a predetermined slope 4 on the tube end surfaces are connected with their axes aligned, and a flexible heat-resistant strip 6 is wound around the abutting tube end surfaces. Steps to press the strip 6 to make it adhere tightly to the tube body, weld the gap portions on both end faces formed in a "V" shape by the above-mentioned slope 4.4, and then release the pressure on the band 6 and remove it from the tube body. The above problem was solved by forming a groove.

Briefly, in order to implement the above-mentioned method for connecting steel pipes, the present invention provides a device for tightly adhering a flexible, heat-resistant strip 6 to the bottom of a welding groove by dividing the outer periphery of a cylinder into equal angles. At least three support rods protruding outside the body are attached telescopically, and a curved plate with a curvature slightly smaller than the inner diameter of the steel pipe is fixed to the tip of the support rod in a "T" shape, and the flexible We also proposed a steel pipe connecting device that supports and presses the heat-resistant strip, and completely solved the above problems.

[Function] A method for connecting steel pipes according to the present invention will be explained based on FIGS. 1 and 2 showing examples.

Figure 1 mainly shows large-diameter steel pipes that workers can enter into, but when the steel pipe is laid in a tunnel, the gap between the top wall of the tunnel and the outer circumference of the pipe is too small to paint the outside surface after welding. This is an example.

Furthermore, FIG. 2 mainly shows an example in which a small-diameter steel pipe can be welded and painted from the outside of the pipe, but the inside cannot be painted on the inside after welding because a worker cannot enter the inside of the pipe.

When two steel pipes are connected with their axes aligned, a predetermined slope is cut on the same surface of the pipe ends, so the outer surface of the pipe ends (Fig. 1)
Or, they are abutted on the inner surface (FIG. 2) to form an inverted V-shape or a V-shaped groove.

Next, a flexible heat-resistant strip is wound around the circumferential surface of the abutted steel tubes, and the strip is evenly pressed in the direction of the tube as shown by the arrow in the figure to bring it into close contact with the tube.

Thereafter, this groove is subjected to ordinary resistance welding from the inside (FIG. 1) or the outside (FIG. 2) using a mild steel welding rod to form a welded portion 5.

At this time, the band-shaped body applied to the bottom of the groove (butt part) adheres closely to the pipe body and has heat resistance that does not deteriorate even when subjected to welding heat, so it functions in the same way as a welding backing metal, allowing on-site welding. This makes it extremely easy.

After the welding is completed, the pressure on the tubular body is released, and it is removed from the tubular body and collected.

Ceramic coatings are applied to both the inner and outer surfaces of the welded parts and heat-affected zones of steel pipes, and this coating layer has extremely high heat resistance and will not burn out or crack and peel off due to welding heat, so in principle, it is not required after welding. There is no need to repaint it again and again.

In the method of the present invention, a flexible, heat-resistant strip is prepared as shown in FIG.
As shown in Figure 2, it is essential to crimp and support the welding groove by applying it to the bottom surface, and in this application, we also propose a connecting device for the 1llll pipe used to implement this method, and we will propose a concrete and effective implementation. The purpose was

Details of the apparatus will be described in the next example.

[Example] ' The ceramic coated steel pipe is detailed in the specification for which the applicant submitted the application for utility model registration on the same day (May 1985) (examples are shown).

A ceramic coating layer having a thickness of 0.1 to 1 m was formed on the surface of the steel pipe by spraying alumina powder as a jet stream from a plasma torch.

Next, as a flexible, heat-resistant strip, ceramic fiber (trade name: "Ipiwool" manufactured by Ibiden Co., Ltd.) was used.

Crystal is made from high-purity alumina and silica as main raw materials that are melted in an electric furnace and made into fibers using compressed air.
A multi-fiber aggregate made of a material that can withstand high heat of 1 to 400 degrees Celsius and formed into a strip with a thickness of 1 cm and a width of about 3 cm was used.

Alternatively, a commercially available flexible backing material (manufactured by FRB Kobe M Co., Ltd.) may be used.

If it is difficult to paint after welding as shown in Figure 1, the strip 6 is wound around the outside of the steel pipe and crimped. An example of this is shown in (front sectional view).

Workers who have a small gap between the top wall of the tunnel and the top of the steel pipe cannot perform detailed work in this gap.

As shown in the cross section in Fig. 4, a concave groove is provided on the inner surface of the support band 7 made of canvas or flexible steel, and the band-shaped body 6 is inserted into the groove to form a composite band, and this composite band is attached to the outside of the steel pipe. Two pieces are cut to a length corresponding to half the diameter, and the mounting brackets 8 are tightly attached to both ends of the pieces.

Since this composite band is flexible, a worker who enters the tunnel hooks the mounting bracket 8 at the tip of the operating rod and slides it up along the outer circumference of the steel pipe, and when it crosses the top of the pipe, attaches it from the opposite direction. Hook the metal fitting 8 and slide it down.

On the other hand, the lower bottom part of the steel pipe is wound around and the same composite band is pulled upward, both mounting fittings 8 are connected with pins, and the band-like body 6 is pressed and crimped against the outer surface of the steel pipe.

When connecting small and medium diameter steel pipes as shown in FIG. 2, the strip 6 must be pressed from the inner surface of the pipe, contrary to the case shown in FIG.

The configuration of the device used to carry out this method is as stated in claim 2, but the first embodiment of the device is described in claim 5.
(front sectional view) and FIG. 6 (side sectional view, AA sectional view in FIG. 5).

In both figures, a rotating shaft 10 is inserted horizontally through the axis of the cylindrical body 9A, and a handle 11A for mounting is attached to one end of the rotating shaft (the left end in FIG. 5), and a handle 11A is attached to the other end in a certain range. A male thread 12 is applied across the entire length.

Inside the cylindrical body 9A, a conical body 14 having a female thread 13 in the center hole which is screwed into the male thread 12 of the rotating shaft is attached to the rotating shaft 1.
0.

The body of the cylindrical body 9A is divided into equal parts (six parts in this example), circular holes are provided in several places, and the guide cylinder 15 is made to protrude from the circular holes.
Support rods 16A are inserted into these circular holes and restrained by guide tubes 15.

The support rod 16A inserted into the cylindrical body 9A is surrounded by an elastic body 17.

One end of the support rod 16A contacts the inclined conical surface of the cone body 14, and the other end reaches near the steel pipe 1 and touches the support plate 18A.
Attach it to the T shape.

This support plate is a curved plate having a curvature slightly smaller than the inner diameter of the steel pipe 1, and a concave groove is cut into the surface of the support plate, into which the band-shaped body 6 is inserted.

When all of the support plates 18A are connected, they form a concentric cylindrical body that is slightly smaller than the inner diameter of the steel pipe 1, but they are divided into the same number of circular arcs for each support rod 16A, and as shown in a perspective view in FIG. When the disk is divided into one block using the plate 18A1 and the reinforcing plate 19, and the end faces of each adjacent block are inserted from the left and right into the mounting groove 20 provided on the cylindrical body 9A, and all are connected, a single block is formed. A configuration forming a disk is convenient.

It is preferable to fix four legs 21 to the bottom of the cylindrical body 9A, and attach wheels 22 to the tips of the legs 21 so that the device can move around the inner surface of the barbed steel pipe 1.

Further, it is preferable to interpose a centering device 23 between the handle 11A provided at both ends of the rotating shaft 10 and the cylindrical body 9A for aligning the rotating shaft 10 of the device with the axis of the steel pipe 1.

This centering device 23 has a rotating shaft 10 inserted into a central cylinder, and four extendable centering devices 25 with turnbuckles 24 interposed therebetween projecting from the cylinder at equal angles.

To briefly describe the operation of the embodiment of the apparatus described above, the apparatus is inserted into the inner surface of a welded portion in a steel pipe 1.

Since the device is provided with legs 21 and wheels 22, it can be easily moved along the inner wall of the steel pipe and sent to a predetermined position.At this time, the centering device 23 is placed slightly below the end face of the steel pipe 1, and the handle 11A is The rotating shaft 10 is located outside the steel pipe.
The axial length of is set in advance.

The four centering devices 25 of the centering device 23 are expanded and contracted by adjusting the turnbuckles 24 to align the rotating shaft 10 with the axis of the steel pipe 1.

Next, when the handle 11A is rotated, the conical body 14 begins to move horizontally due to the threaded engagement formed on the other end of the rotating shaft 10, and the support rod that is in contact with the conical surface of the conical body 14 moves horizontally. 1
The tip of 6A approaches the inner surface of the steel pipe 1 while its position is restrained by the guide tube 15.

Since the support plate 18A is fixed to the tip of the support rod 16A in a "T" shape, the target strip 6 is placed like an endless belt in the groove carved on the support plate 18A. Rotation of the handle 11 brings the strip 6 close to the inner surface of the steel pipe 1, brings it into contact, and roughly presses it into close contact.

As mentioned above, each support rod forms an independent block and can move independently, so the restraining force is small and movement is smooth, and minute differences in movement between each block can be compensated for by installing a structure around the bottom of the support rod. This can be absorbed by the action of the elastic body 17, and in the end, the strip 6 is pressed against the inner surface of the steel pipe 1 with an even force, and there is no risk of damaging the strip 6 due to excessive pressure if the handle operation is controlled. This desired effect can be achieved.

A second embodiment of the device invention of the present application will be described based on FIG. 8 (front sectional view) and FIG. 9 (side sectional view, AA cross section in FIG. 8).

One end of the horizontal axis (non-rotating) 26 is a handheld handle 1
1B, the other end is fixed to the center of the side surface of the cylindrical body 9B.

The circumferential surface of the cylindrical body 9B is divided at equal angles (6 in this example).
A cylinder 27 with an electromagnetic valve is installed in each circular hole radially toward the inner surface of the steel pipe.

As in the previous embodiment, the support plate 18B, which has a groove carved on its upper surface into which the strip 6 is fitted, is divided into a number of curved sections each having a curvature slightly smaller than the inner diameter of the steel pipe 1.
The tip of a cylinder 27 with a solenoid valve abuts B as a support rod 16B.

The support plate 18B is welded in an rTJ shape except for the position of the cylinder by a reinforcing plate 19B, and the reinforcing plate 19B is fitted into mounting grooves 20B divided at equal angles on the circumference of the cylindrical body 9B, so that they are independent of each other. It was constructed so that it could expand and contract around the axis.゛This cylindrical body 9B is equipped with an air hose 2 for operating a cylinder 27 with a solenoid valve as shown in Fig. 8.
8 and an electric wire 29, the end of which runs along a horizontal shaft 26 and reaches a handle 11B for operation.

Note that the legs and wheels attached to move the cylindrical body and the centering device for aligning the horizontal axis 26 of the device with the axis of the steel pipe 1 are the same as those in the first embodiment.

In this second embodiment, in order to press the flexible, heat-resistant strip 6 from the inner surface of the bottom of the welding groove of the steel pipe 1, it is necessary to move the divided support plate and the plate independently. A cylinder with a solenoid valve is used.

After setting the device at a predetermined position inside the steel pipe as in the previous embodiment, when the power source of the handle 11B at hand is turned on and the solenoid valve is activated, the pressure moves through the air hose, causing the piston in the cylinder to move. Push up, this push up is support plate 1
8B and presses it roughly to bring the strip 6 into close contact with the inner surface of the steel pipe 1.

[Effects of the Invention] The method and apparatus for welding steel pipes according to the present invention can protect the coating layer of the on-site welded portion from burnout and peeling, and in principle does not require repainting after welding.

Compared to the conventional technique shown in FIG. 10, which was developed for the same purpose, a stainless steel welded part is not required during welding, so the difficulty and complexity of welding work is significantly improved.

Furthermore, there is no risk of economic deterioration in terms of quality, and the service life of the water supply channel is increased.

Furthermore, by using the apparatus according to the invention described in claim 2, the above-mentioned welding method can be carried out easily and reliably, and there are few defects during welding, and the diameter is small so that the mulch worker cannot sneak into the pipe. In this case, the effect on quality and work efficiency is significant.

[Brief explanation of the drawing]

1 and 2 are partial front sectional views showing different embodiments of the present invention, FIGS. 3 and 4 are side sectional views and partial front views of the embodiment of FIG. 1, 5 to 7 are examples (front sectional view, side sectional view, partial perspective view) of the apparatus used in the embodiment shown in FIG. 2, and FIGS. 8 and 9 are examples of the device used in the embodiment shown in FIG. 2. Another example of the device used for (front sectional view, side sectional view),
FIG. 10 is a front sectional view showing the prior art.

Claims (1)

[Claims] 1. A ceramic coating 3 is applied to the pipe body surface near both ends of the steel pipe 1, and a predetermined paint 2 is applied to the pipe body surface excluding these parts to form a predetermined slope 4 on the pipe end surface. Two ceramic coated tubes are connected so that their axes coincide, and a flexible heat-resistant strip 6 is wound around the abutting end surfaces of the tubes.
is pressed evenly to make it adhere tightly to the tube body, and the gaps on both end faces formed by the above-mentioned slopes 4 and 4 in a "V" shape are welded. After construction, the pressure on the strip 6 is released and the strip is removed from the tube body. How to connect the steel pipe to be removed. 2. Divide the outer periphery of the cylinder into equal angles, attach at least three support rods that protrude outside the cylinder in a telescopic manner, and attach a curved plate with a curvature slightly smaller than the inner diameter of the steel pipe to the tip of the support rod.
A steel pipe connecting device for use in carrying out the method according to claim 1, in which a flexible heat-resistant strip 6 is supported and pressed onto the curved plate.