JPH01295825A - Method and apparatus for manufacturing corrosion-resistant coated steel pipe - Google Patents

Abstract

PURPOSE:To manufacture a corrosion-resistant coated steel pipe, by providing a process for winding a strip like thermoplastic synthetic resin sheet around the outer peripheral surface of a preheated steel pipe in such a state that the adjacent side end surfaces of said sheet are brought into contact with each other in an abutted state and a bonding process for thermally welding both adjacent side end surfaces of the resin sheet under pressure. CONSTITUTION:A steel pipe 1 is placed on a drive roll 110 and rotated around its axis at a constant speed in the direction shown by an arrow (a). The outer peripheral surface 1A of the steel pipe 1 is preheated to about 200 deg.C by the gas burner 108 inserted on the inner surface side thereof and a thermoplastic synthetic resin sheet 2 is supplied to the steel pipe 1 to be wound therearound while the adjacent side end surfaces of said sheet are mutually brought into contact with each other in an abutted state. Since the resin sheet 2 is thermally expanded, the abutted seam 2A thereof is softened while built up to begin to melt. When the part of the seam 2A is pressed by the roller 42 of a seam press means 40, the air between the built-up part and the surface of the steel pipe is expelled, and the abutted seam 2A, the resin sheet 2 and the outer peripheral surface 1A of the steel pipe are respectively welded in a closely bonded state.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is directed to an anti-corrosion coated steel pipe that has a thermoplastic synthetic resin coating layer formed on the outer peripheral surface of the steel pipe and is used as foundation piles in civil engineering works. The present invention relates to a manufacturing method and a manufacturing device.

[Conventional technology]

For example, in the case of structures such as bridges built on the sea, steel pipe supports are welded to steel pipe piles driven into the seabed and protrude above the sea surface. This steel pipe support is most likely to corrode in the tidal zone of the sea surface and the so-called splash zone above it (the part most likely to be hit by splashes from waves). Therefore, corrosion protection for the portion of the steel pipe support that extends from the tidal zone to the splash zone is particularly important. Conventionally, this type of anti-corrosion steel pipe has been manufactured by: ■ Applying a thick layer of urethane or epoxy paint, or ■ Continuously extruding molten polyolefin resin to coat the outer circumferential surface of the steel pipe.
(Polyethylene melt extrusion coated) anti-corrosion coated steel pipes have been used.

In contrast, JP-A-61-40925 proposes another anti-corrosion coated steel pipe pile and its manufacturing method. This tape is made by wrapping a heat-shrinkable polyolefin tape, which has an adhesive layer made of heat-adhesive polyolefin with adhesive functional groups, around the circumferential surface of a steel pipe pile in a spiral shape, with the side edges partially overlapping. The area between the steel pipe pile and the tape and the overlapping part of the tape are anti-corrosion coated steel pipe piles that are thermally bonded by the adhesive layer, and the peripheral surface of the preheated steel pipe pile is A heat-shrinkable polyolefin tape having an adhesive layer made of heat-adhesive polyolefin having an adhesive functional group is wound spirally under tension so that the side edges thereof are partially overlapped. The method for manufacturing an anti-corrosion coated steel pipe pile includes thermally bonding the tape to the circumferential surface of the steel pipe pile using the adhesive layer, and fusing or joining the overlapped portions of the tape using the adhesive layer.

[Problem that the invention seeks to solve]

However, each of the above conventional devices has the following problems.

■The cost of painting materials is high.

For the polyethylene melt extrusion coating method described in (2), the manufacturing equipment is very expensive, the transportation cost of the steel pipe after anti-corrosion treatment is high, and it also gets damaged due to handling during transportation, which requires a lot of effort to repair. .

6, a void E remains at the overlapping side edge portion of the heat-shrinkable polyolefin tape C having adhesive NB wrapped around the circumferential surface of the steel pipe pile A, and this void Intrusion of moisture into portion E causes rust and eventually peeling of the polyolefin tape C.

In particular, regarding the above point (2), since a void E remains along the spiral overlapping portion, this void E continues spirally in the longitudinal direction of the steel pipe, so the occurrence of rust etc. There is a risk that the corrosion will proceed simultaneously throughout the length of the steel pipe.

Therefore, the present invention solves the above-mentioned conventional problems by providing a method for manufacturing an anti-corrosion coated steel pipe and a manufacturing apparatus for the same, in which a thermoplastic synthetic resin film is wrapped around the outer peripheral surface of a preheated steel pipe without leaving any air. It is intended to.

[Means for solving problems]

The method for producing an anti-corrosion coated steel pipe of the present invention which achieves the above object is a method for producing an anti-corrosion coated steel pipe in which a band-shaped thermoplastic synthetic resin sheet is spirally wound and fused around the outer peripheral surface of a preheated steel pipe. The winding process involves bringing the adjacent side end surfaces of the sheets into butt contact, and at the point when the adjacent sheets whose side end surfaces are brought into contact with each other start to melt together, both adjacent sheets are simultaneously pressed by a pressing means. The method includes a joining step of thermally fusing the sheets together.

Furthermore, the apparatus for manufacturing an anti-corrosion coated steel pipe of the present invention spirally wraps a band-shaped thermoplastic synthetic resin sheet around the outer peripheral surface of a preheated steel pipe that is rotating at a constant speed while moving relative to the pipe axis direction. An apparatus for manufacturing an anti-corrosion coated steel pipe, comprising: a sheet supplying means for supplying the thermoplastic synthetic resin sheet from an oblique direction with respect to the longitudinal direction of the steel pipe so that side end surfaces of the sheet are butted against each other; and a butt joint pressing means for pressing the butt joint portion of the sheet side end that has started to melt on the outer peripheral surface of the steel pipe against the outer peripheral surface of the steel pipe.

[Effect]

According to the present invention, when a belt-shaped thermoplastic synthetic resin sheet is spirally wound and fused around the outer peripheral surface of a preheated steel pipe, the adjacent side end surfaces of the sheet supplied from the sheet supply means are Contact the butt. Then, when the adjacent sheets brought into contact begin to melt together, both adjacent sheets are thermally fused together while simultaneously pressing the joint portion of the two sheets using a pressing means. Therefore, there is no need to form overlapping portions of anticorrosive coatings as in the past, and there are no voids. Therefore, phenomena such as rust caused by moisture intrusion into the voids and peeling of the anticorrosive coating due to this do not occur at all.

Note that the thermoplastic synthetic resin used in the present invention is a normal resin that has not been treated to have heat shrinkability.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the method and apparatus for manufacturing anti-corrosion coated steel pipes of the present invention will be described below with reference to the drawings.

1 to 4 show an embodiment of the anti-corrosion coated steel pipe manufacturing apparatus of the present invention. For example, a spiral steel pipe 1 with an outer diameter of 660 mm is coated with 2 to 4 fins (for example, 311 mm thick) on the outer circumferential surface IA of the spiral steel pipe 1. ), width approximately 100 to 1009 mm (for example, 50
It is configured such that a thermoplastic synthetic resin sheet 2 (0n) can be wound spirally.

For example, a polyethylene sheet is used as the thermoplastic synthetic resin sheet 2 in consideration of weather resistance. The polyethylene sheet 2 has an outer surface made of ordinary polyethylene,
2 whose inner surface is made of modified polyethylene with adhesive properties.
The layer is polyethylene. The latter modified polyethylene having adhesive properties is preferably one obtained by reacting low-density or high-density polyethylene with maleic anhydride or the like. However, it is also possible to introduce a known adhesive functional group other than maleic anhydride groups. Furthermore, as the thermoplastic synthetic resin, polyolefins other than polyethylene, copolymers with vinyl acetate, etc. can also be used.

Further, additives and fillers such as antioxidants and carbon black may be contained as necessary.

This manufacturing apparatus includes sheet supply means 10. In this system, a thermoplastic synthetic resin sheet 2 attached to a horizontal rotating shaft 11 or wound around a coil 12 is continuously supplied from an oblique direction with respect to the longitudinal direction of a steel pipe 1.

The rotating shaft 11 is rotatably supported on a support frame 13, and a brake device 14 is provided at the end of the shaft. This brake device 14 applies appropriate resistance to the feeding of the thermoplastic synthetic resin sheet coil loaded on the reel 12,
This is to tension the thermoplastic synthetic resin sheet 2 to the extent that it does not loosen. For example, a simple type of friction brake that can adjust the tightening strength of the nut may be used.

Reference numeral 15 denotes a guide roll that is suspended and attached to the tip of the support frame 13 via an arm 16.

The sheet supply means 10 is attached to a horizontal support base 17, and can be rotated in a horizontal plane about a pivot shaft 18 by turning a handle (not shown).

On the lower surface side of the horizontal support stand 17, a sheet supply means 10 is provided.
A sheet crimping means 20 having a plurality of sheet crimping rolls 19 for pressing the thermoplastic synthetic resin sheet 2 sent out from the steel pipe onto the outer circumferential surface IA of the steel pipe is attached by an arm 21. This sheet pressure roll 19 is formed to be horizontally rotatable in conjunction with the sheet supply means 10 via a connecting arm 22.

Furthermore, in order to adjust the winding angle and winding pitch of the thermoplastic synthetic resin sheet 2 that is spirally wound around the steel pipe 1, the sheet feeding means 10 and the sheet pressing means 20 are connected to each other via a horizontal support 17. A horizontal slide means 30 is provided for integrally moving the tube horizontally and linearly in the tube axis direction.

In this embodiment, by operating the feed handle 31 of the horizontal slide means 30, the thermoplastic synthetic resin sheet 2 supplied from the sheet supply means 10 is wound around the steel pipe 1 in a spiral manner. The side end surfaces are adjusted in advance so that they are in butt contact with each other.

However, the horizontal slide means 30 is not necessarily necessary to wrap the side end surfaces of adjacent sheets so that they are in butt contact with each other. However, by providing the horizontal slide means 30, it is possible to Since the crimping means 20 can be shifted, the steel pipe 1
It has the advantage of being able to immediately respond to changes in the shape and dimension of the thermoplastic synthetic resin sheet 2, as well as changes in the dimensions of the thermoplastic synthetic resin sheet 2.

A butt joint pressing means 40 is further attached to the lower surface side of the horizontal support base 17.

The butt joint pressing means 4° of this embodiment includes, for example, a pair of rollers 42 attached to a bracket 41 in accordance with the curvature of the outer surface of the steel pipework, and a pressing means 43 such as an air cylinder (or a spring mechanism). We are prepared. As shown in FIG. 2, in order to press the butt joint 2A of the thermoplastic synthetic resin sheet 2 spirally wound around the steel pipe 1, this roller 42 is adjusted to the winding angle of the sheet.
It is arranged along the butt seam 2A.

Each means such as the sheet supply means 10, the sheet pressure bonding means 20, and the butt seam pressing means 40 is disposed on a base 100 via a main column 101, and the base 100 is connected to the track 1.
A bogie 104 that runs on 02 through the transfer of wheels 103
It is placed on. The trolley 104 of this embodiment has a base 1
A long cantilever beam 10 that is inserted into the inside of the steel pipe 1 is driven by a chain wheel (not shown) that is powered by a traveling motor 105 mounted on the trolley 104.
7 is fixed, and a gas burner 108 for heating the steel pipe 1 from the inner side is attached to the tip of the cantilever 107.

The steel pipe I is placed on a drive roll 110 disposed in a space above the track 102, and supported so as to be rotatable at a constant speed about the pipe axis.

Note that 114 is the sheet supply means 10 and the sheet pressure bonding means 3.
0, a worm jack for retracting the butt joint pressing means 40 and the like above the steel pipe 1.

Next, the action will be explained.

The steel pipe 1 is placed on a drive roll 11O and rotated at a constant speed in the direction of arrow A. The steel pipe 1 is heated by a gas burner 108 inserted into the inner surface to preheat the outer circumferential surface IA of the steel pipe to about 200°C.

This preheating temperature was determined experimentally as follows.

That is, in order to prevent the coating polyethylene from peeling off over a long period of time in seawater, it is preferable to apply a primer to the outer peripheral surface of the steel pipe 1 as a pretreatment.

For this purpose, for example, an epoxy primer is applied in advance.

However, both one-component and two-component epoxy primers contain volatile components, so it is difficult to heat-melt polyethylene. L degree (140~
Gas is generated at 240'C), causing blisters and wrinkles in the polyethylene film. To remove that force in advance,
It is necessary to heat the polyethylene to a temperature higher than the thermal fusion temperature to drive out the volatile components and dry it in advance.

Therefore, an experiment was conducted to determine the drying preheating temperature of the epoxy primer. The temperature for applying epoxy primer to steel pipes is 80°.
It was set as C. (2) When the coating was dried at 160°C and then heat-sealed at 190°C, blistering occurred on the negative side. (2) After coating, drying at 200°C and then heat-sealing at 190°C did not cause any blistering. (2) After drying at 250°C after coating and then heat-sealing at 190°C, no blistering was observed, but adhesive strength decreased.

From the above results, the optimal preheating temperature is 200°C, which is 10°C higher than the heat fusion temperature of the polyethylene resin sheet, 190°C.
It turned out to be C.

The thermoplastic synthetic resin sheet 2 is continuously applied to the outer circumferential surface IA of the preheated hot steel pipe 1 from the sheet supply means IO via the guide roll 15 from an oblique direction to the tube axis, that is, at a predetermined angle. Let and supply. This supply drives the traveling motor 105 to drive the bogie 104 on the track 102.
This is performed while the sheet feeding means 10 is moved at a constant speed along the tube axis.

The supplied thermoplastic synthetic resin sheet 2 is crimped and wound around the outer circumferential surface IA of the steel pipe by a sheet crimping roll 19. The winding is performed while the adjacent side end surfaces of the sheets are brought into butt contact with each other. Since the thermoplastic synthetic resin sheet 2 thermally expands, the butt joint 2A on the side end surface bulges as shown in FIG. 3, softens, and begins to melt. The raised butt seam 2A
The sections are pressed by rollers 42 of butt seam pressing means 40. As a result, the air between the raised portion and the steel pipe surface is expelled, and the butt eyelet 2A and the thermoplastic synthetic resin sheet 2 and the outer circumferential surface IA of the steel pipe are fused in a tight state (Fig. 4). . In this manner, the thermoplastic synthetic resin sheet 2 is wound in a spiral manner, and the thermoplastic synthetic resin sheet 2 is firmly heat-sealed to the outer circumferential surface IA of the steel pipe without any gaps. After wrapping the thermoplastic synthetic resin sheet 2 to a predetermined length, the thermoplastic synthetic resin sheet 2 is cut with a cutter.

In this way, a good anti-corrosion coating layer with no overlapping portions of the thermoplastic synthetic resin sheets 2 and no residual air is formed on the outer circumferential surface IA of the steel pipe.

FIG. 5 shows another embodiment.

This embodiment includes the sheet feeding means 10, the aforementioned sheet pressing means, butt seam pressing means, and a gas burner 108 attached to a cantilever beam 107.
, a cooling device 109 for cooling the inner surface of the steel pipe l after heat fusion.
etc. are fixed to the fixed frame 120. On the other hand, a drive roll 110 is mounted on a carriage 104 (two units are connected by a rod 104A) running on a track 102 together with a steel pipe rotation drive motor (not shown). The trolley 104 is driven by a built-in travel motor.

The steel pipe 1 is placed on the drive roll 110, rotated at a constant speed about the pipe axis, and simultaneously transported at a constant speed in the direction of the pipe axis by the cart 104.

This embodiment has the advantage that workers can work at the same location without having to move.

In each of the above embodiments, two-layer polyethylene was used as the thermoplastic synthetic resin sheet, but other thermoplastic synthetic resins may also be used.

Further, it goes without saying that the outer circumferential surface of the steel pipe may be subjected to well-known pretreatment such as rust removal treatment and anticorrosion treatment.

Further, cooling after the formation of the anticorrosive coating may be performed by blowing air onto the outer surface of the steel pipe. In addition, for preheating steel pipes,
In addition to gas burners, electric heating and high-frequency heating can be used.

〔Effect of the invention〕

As explained above, according to the method for producing an anti-corrosion coated steel pipe of the present invention, a strip-shaped thermoplastic synthetic resin sheet is brought into contact with the outer peripheral surface of the steel pipe heated to a predetermined temperature, with the adjacent side end surfaces butting together. Wrap it in a spiral. Then, while pressing the butt joint portion with a pressing means, both adjacent sheets and the sheet and the outer circumferential surface of the steel pipe are thermally fused together.

Therefore, there is no risk of air remaining and causing rust and peeling of the anti-corrosion coating, unlike in conventional stacking techniques.

Furthermore, compared to the coating method, it can be provided at a lower cost.

Furthermore, the apparatus for manufacturing anti-corrosion coated steel pipes of the present invention has a much simpler structure and is cheaper than the conventional polyethylene melt extrusion coating apparatus. Moreover, since no special installation foundation is required, it is easy to transport and install, and if it is brought to the construction site and installed, it is possible to manufacture anti-corrosion coated steel pipes on site, so it is possible to use anti-corrosion coated steel pipes produced in factories. This has the effect of significantly reducing the cost of transporting it to the site.

[Brief explanation of the drawing]

FIG. 1 is a side view showing one embodiment of the manufacturing apparatus for anti-corrosion coated steel pipes of the present invention, FIG. 2 is a schematic front view of the main parts of FIG. 1, and FIG.
The figure is an enlarged sectional view of the sheet butt joint before being pressed by the butt seam pressing means, FIG. 4 is an enlarged sectional view of the sheet butt joint after being pressed by the butt seam pressing means, and FIG. 5 is the corrosion protection of the present invention. FIG. 6 is a side view schematically showing another embodiment of the coated steel pipe manufacturing apparatus, and FIG. 6 is an enlarged sectional view of a sheet joint portion of a conventional anti-corrosion coated steel pipe. 1 is a steel pipe, IA is the outer peripheral surface of the steel pipe, 2 is a thermoplastic synthetic resin sheet, 2A is a butt joint, 10 is a sheet supply means,
40 is a butt joint pressing means. Patent applicant: Kawasaki Steel Corporation Representative Patent attorney: Tetsuya Mori

Claims (2)

[Claims] (1) A method for manufacturing an anti-corrosion coated steel pipe in which a band-shaped thermoplastic synthetic resin sheet is spirally wound around the outer peripheral surface of a preheated steel pipe and fused, the adjacent side end surfaces of the sheet being brought into butt contact. and a joining step of heat-sealing both adjacent sheets while simultaneously pressing them with a pressing means when the adjacent sheets whose side end surfaces are in contact with each other start to melt together. A method for manufacturing an anti-corrosion coated steel pipe characterized by: (2) An apparatus for manufacturing an anti-corrosion coated steel pipe in which a band-shaped thermoplastic synthetic resin sheet is spirally wrapped around the outer peripheral surface of a preheated steel pipe that is rotating at a constant speed while moving relatively in the pipe axis direction, a sheet supply means for supplying the thermoplastic synthetic resin sheet from an oblique direction with respect to the longitudinal direction of the steel pipe so that the side end surfaces of the sheet are butted together; An apparatus for producing an anti-corrosion coated steel pipe, comprising: butt joint pressing means for pressing the butt joint portion of the sheet side end that has started to melt against the outer circumferential surface of the steel pipe.