JPS5812845B2 - Nimen lining information - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for lining the inner surface of a welded joint of a steel pipe whose inner surface is resin-lined for use in slurry transport piping, chemical industry piping, or the like.

The inner surface of the inner-lined steel pipe is lined by using centrifugal force or by injecting resin into the gap between the inner and outer tubes formed by inserting thin-walled tubes concentrically into the inner surface.

Highly reliable welded joints are often used to connect such inner-lined steel pipes, but the inner surface of the joint, which is affected by the heat of welding, is lined with resin after welding at the piping site, for example, with a partition plate on the inner surface of the pipe. A method is used in which the inner surface of the joint is lined by placing and pressing it in the radial direction with an expander or the like to define a ring-cylindrical gap on the inner surface of the joint, and then injecting resin into this gap.

However, with this method, it is difficult to insert or remove the expander from the inner surface of the long pipe at the piping site, and this difficulty increases particularly when piping is performed using bent pipes.

As a result of various experimental studies aimed at solving the drawbacks of conventional methods, the present invention has developed a method for lining the inner surface of welded joints that can be easily implemented not only for straight pipes but also for curved pipes. Inner lining of a steel pipe with a through hole for resin injection or exhaust perforated at the unlined joint end.A core body made of an inorganic compound with heating wires embedded inside the butt welded joint of a steel pipe is concentrically placed inside the butt weld joint of the steel pipe. An annular cylindrical gap with both ends sealed is defined in the unlined part of the inner surface of the joint by inserting and arranging, and after welding the steel pipe abutting portion, resin is injected and filled into the annular cylindrical gap through the through hole to line the inner surface of the joint. The core is lined and the through hole is sealed, the lining layer is hardened by applying electricity to the heating wire, and then the core body is disintegrated or removed by pouring water and dissolving it.

Embodiments of the method of the present invention will be described with reference to the accompanying drawings.

Figure 1 is a longitudinal sectional front view of a joint of inner-lined steel pipes. 1 and 1' are inner-lined steel pipes (hereinafter referred to as steel pipes) to be joined, and an inner lining layer 2 made of resin or the like is applied except for a part of the joint end. .

3 is a core body formed into a cylindrical body made of an inorganic compound having a melting point of 150° C. or higher and a water solubility of 5 g/100 CC or higher (at 20° C.) as described later.

4 is a water-soluble packing that includes a core body 3 and an inner lining layer 2.
Airtightness is maintained on both sides of the annular cylindrical gap 5 interposed at the end and defined on the inner surface of the joint.

6. 6' is a resin injection hole and an exhaust hole drilled at the ends of the steel pipes 1 and 1', 7 is a welded part, and 8 is a plurality of wires, such as nichrome wires, embedded at regular intervals in the thick part of the core body 3. A plurality of branch heating wires 8' are provided in the thickness direction.

It is preferable to avoid providing the branched heating wires 8' at both ends of the core body 3 as much as possible in order to prevent thermal deterioration of the lining layer.

The extended end of the heating wire 8 is connected to a power source (not shown) outside the end of the steel pipe.

To line the inner surfaces of the joint ends, insert the core body 3 into the inner surfaces of the joint parts of the steel pipes 1, 1', and connect the steel pipes 1, 1' by welding 7 the outer periphery of the attached successor part as shown in the figure. If resin is injected from the resin injection hole 6 into the annular gap 5 defined on the inner surface of the joint part, the air etc. in the annular gap 5 will be discharged to the outside of the tube through the exhaust hole 6', which is equivalent to the annular gap. A thick resin lining layer is formed on the inner surface of the joint.

Therefore, if the branch heating wire embedded in the thick part of the core body 3 is energized to raise the temperature of the core body 3, the resin lining layer will quickly harden, and after the resin lining layer has solidified, the power supply will be turned on. Either pull the separated heating wire 8 to collapse the core body 3, or
Alternatively, the core body 3 is dissolved by pouring water.

Further, the resin injection hole 6 and the exhaust hole 6' are closed by driving a pin or the like.

FIG. 2 shows a modification of FIG. 1, in which a thick wall portion 2 is provided at the end of the lining layer 2 at the ends of the steel pipes 1 and 1' in place of the water-soluble packing 4, thereby defining an annular-cylindrical gap 5. There is.

In this case, the heating wires 8 and branch heating wires 8' are not shown in the core body 3, but are arranged in the same manner as in FIG.

Further, if necessary, an adhesive may be used instead of using the water-soluble packing 4 or forming the thick portion 2' at the end of the lining layer 2.

Table 1 shows the inorganic compounds used in the core body 3.

To form the core body 3, water glass is added to the inorganic compounds shown in Table 1 alone or in combination, or in combination with water-insoluble SiO2, etc., and kneaded, and this is mixed with, for example, As illustrated in the figure (longitudinal sectional view), a base plate 11, a core 12, and a split mold 13 are filled into an assembled mold, and a cylindrical core body is formed by blowing carbon dioxide gas.

It is best to use the water-soluble compound in an amount of 1% or more, but it is effective even if the amount is less than 1%.

That is, the inorganic compound filled in the mold is bonded using Na2CO3, which is a combination of water glass and carbon dioxide gas, as a medium, so that the core body 3 is formed.

During this molding, heating wires 8 made of a plurality of nichrome wires or the like are embedded in the thick part of the core body 3 as shown in the figure.
It is possible to heat up the core body on the inner surface or easily disintegrate the core body.

Inorganic compounds need to have no risk of melting even under the influence of heat during welding of steel pipes 1 and 1', and must be able to be dissolved in ordinary water at a water temperature of around 20°C. Melting point is 150℃ or higher, water soluble 5g/100c
The purpose of this method can be achieved by selectively using inorganic compounds having properties of c or higher.

Next, an example of implementing the present invention will be described.

Outer diameter 406.4mm, wall thickness 6. Omm, length 5.5mm
Polyurethane lining is applied to the inner surface of the steel pipe to a thickness of 4 mm, leaving 100 mm at both ends, and the length is 300 mm and the outer diameter is 3.
A core body of 84 mm and wall thickness of 40 mm is inserted into one end of the steel pipe.

In this case, positioning protrusions are provided in advance on the lining surface of the steel pipe.

Furthermore, one end of another steel pipe is butted with the steel pipes so that the core body is inserted, and after butt welding, an electric current is passed through the nichrome wire embedded in the core body to preheat it to 80 ° C. 1 at 120℃ after injection of polyurethane resin.
Vulcanization cured for hours.

After the resin had hardened, a nichrome wire was pulled out from one end of the steel tube to destroy the core, but approximately 80% of the core was destroyed.
These fragments were taken out of the tube using a vacuum cleaner, and those adhering to the tube were immersed in water for 3 hours to be removed by natural dissolution, and the inner surface of the welded joint was completely lined.

The composition of the core body used in this example is as follows.

Silica sand 50wt%, salt 45wt%, water glass 5%, CO
2 blowing for 5 minutes, packing: soda fiber grease #150 (consistency 150, dropping point > 170℃, mineral oil content > 15%, flash point > 200℃, viscosity 55R (100℃)
Free Na2O 0.3%, ash 8.0%, moisture 2.0%
]50, 25% of silica sand and 25% of common salt were mixed together as a liquid packing, and an average of 0.5mm was applied to 50mm of both ends of the core body.
It was applied to the factory lining of the steel pipe to an average thickness of 1 mm.

As explained above, the present invention can easily and easily line the inner surface of a welded joint at the piping site of inner-lined steel pipes, and the core body that defines an annular-cylindrical gap on the inner surface of the joint. By embedding a heating wire in the thick part and passing a current through it, the core can be heated up, making it possible to quickly harden the resin lining layer.

In addition, the core body can be easily disintegrated or dissolved by water injection, and can be easily drained by water supply inside the pipe, so it can be used not only for welded joints of straight pipes but also for curved joints. Even in the case of welded pipe joints, it is possible to easily and reliably line the inner surface of the joint.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view of a steel pipe joint showing an embodiment of the present invention, FIG. 2 is a same view showing another embodiment, and FIG. 3 is a longitudinal sectional view showing an example of a mold for forming a core body. be. In the figure, 1: steel pipe, 2: inner resin lining layer, 3: core body, 4: water-soluble packing, 5: annular gap, 6: resin injection hole, 6': exhaust hole, 7: welded part, 8: Heating wire.

Claims (1)

[Claims] 1 A core body made of an inorganic compound with heating wires embedded is concentrically placed on the inner surface of a butt welded joint of an inner-lined steel pipe with a through hole for resin injection or exhaust bored at the unlined joint end of the steel pipe. A ring-cylindrical gap with both ends sealed is formed in the unlined part of the inner surface of the joint, and after welding the steel pipe abutting parts, resin is injected into the ring-cylindrical gap through the through hole to complete the joint. A welded joint for an internally lined steel pipe, characterized in that the inner surface is lined and the through hole is sealed, the lining layer is hardened by applying electricity to the heating wire, and then the core body is disintegrated or removed by pouring water and dissolving it. Inner lining method.