JP2015223786A - Apparatus for producing resin-coated steel tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for producing a resin-coated steel tube capable of easily and stably providing a resin-coated steel tube of good surface quality.SOLUTION: The apparatus for producing a resin-coated steel tube of the present invention is an apparatus for producing a resin-coated steel tube by coating the outer circumferential surface of a steel tube with a thermoplastic resin. The apparatus includes a conveying roller for conveying the steel tube along the longitudinal direction, a die head which the steel tube penetrates and which extrudes the resin concentrically with the steel tube, a water-barrier member that is arranged upstream of a location where the resin contacts the outer circumferential surface of the steel tube in the steel tube conveying direction and elastically contacts the outer circumferential surface of the steel tube, and a water cooling device that is arranged downstream of the water-barrier member in the steel tube conveying direction and ejects water toward the resin so that water cooling of the resin starts upstream of the location where the resin contacts the outer circumferential surface of the steel tube in the steel tube conveying direction.

Description

  The present invention relates to an apparatus for manufacturing a resin-coated steel pipe in which a thermoplastic resin is coated on the outer peripheral surface of a steel pipe.

  A resin-coated steel pipe whose outer peripheral surface is coated with a resin has high corrosion resistance. Therefore, resin-coated steel pipes are widely used for crude oil line pipes, city gas supply pipes, plant pipes, water pipes, and the like.

  The outer peripheral surface of the steel pipe is coated with a thermoplastic resin by extrusion from a die (die head). When the steel pipe is conveyed by a roller while the coated resin is still soft, wrinkles such as roller indentations are generated on the surface of the resin. Therefore, for example, as described in Patent Documents 1 to 3, the resin-coated steel pipe is water-cooled and hardened before reaching the conveyance roller. Here, “curing of the resin” means that the resin softened by heating is cooled and hardened.

  In Japanese Patent Publication No. 63-20695 (Patent Document 1), a ring-shaped water cooling device is disposed at a position 700 mm downstream of the steel pipe in the conveyance direction from the position where the extruded resin contacts the steel pipe. A method is described in which a plurality of nozzles for injecting water from above and below the steel pipe toward the steel pipe are arranged and water-cooled.

  Japanese Patent Application Laid-Open No. 6-23826 (Patent Document 2) describes a method of injecting mist-like cooling water from a diagonally upward direction and a diagonally downward direction of a steel pipe toward a steel pipe coated with a resin.

  Japanese Patent No. 5187435 (Patent Document 3) describes a method of injecting cooling water into a steel pipe coated with a resin only from above.

Japanese Patent Publication No. 63-20695 Japanese Patent Laid-Open No. 6-23826 Japanese Patent No. 5187435

  In any of the above-described conventional techniques, the resin is water-cooled after the resin contacts the outer peripheral surface of the steel pipe. Due to this, the surface properties of the resin may not always be good.

  This invention is made | formed in view of such a situation, and it aims at providing the manufacturing apparatus of the resin coated steel pipe which can obtain the resin coated steel pipe with favorable surface property stably and easily. .

  A resin-coated steel pipe manufacturing apparatus according to the present invention is a resin-coated steel pipe manufacturing apparatus that coats an outer peripheral surface of a steel pipe with a thermoplastic resin, and includes a transport roller that transports the steel pipe along a longitudinal direction, and the steel pipe. A die head for penetrating and extruding the resin concentrically with the steel pipe, and a position where the resin contacts the outer peripheral surface of the steel pipe upstream of the steel pipe conveying direction and elastically contacts the outer peripheral surface of the resin The water shielding member and the water shielding member are arranged on the downstream side in the steel pipe conveying direction, and the water cooling of the resin is started from the upstream side in the steel pipe conveying direction from the position where the resin contacts the outer peripheral surface of the steel pipe. A water-cooling device that ejects water toward the resin.

  In the apparatus for manufacturing a resin-coated steel pipe, when the distance from the position of the downstream end portion of the die head in the steel pipe transport direction to the position where the resin contacts the outer peripheral surface of the steel pipe is L, the water shielding member is , A position of (2/3) × L downstream from the position of the downstream end of the die head in the steel pipe conveying direction, and a position upstream of the steel pipe conveying direction from the position where the resin contacts the outer peripheral surface of the steel pipe It is preferable to arrange | position in the range between the positions of 20 mm.

  In the apparatus for producing a resin-coated steel pipe, the water cooling device is preferably a nozzle that ejects a water flow from at least the upper side and the lower side. The water shielding member is preferably a sponge made of polyurethane.

  According to the apparatus for producing a resin-coated steel pipe of the present invention, a resin-coated steel pipe having a good surface quality can be obtained stably and easily.

FIG. 1 is a diagram showing a configuration of a resin-coated steel pipe manufacturing apparatus according to the present invention. FIG. 2 is a perspective view of the water shielding member.

  The present inventors examined a method for suppressing fine irregularities on the surface of the resin due to uneven cooling, and wrinkles during conveyance due to a delay in cooling. This study was conducted noting that the cooling of the resin was started after the resin was coated on the steel pipe, but that the cooling of the resin was started before the resin was coated.

  As a result of the examination, in the resin-coated steel pipe manufacturing apparatus, a water shielding member that elastically contacts the outer peripheral surface of the resin is disposed at a position immediately before the resin contacts the outer peripheral surface of the steel pipe. It was found that by starting water cooling from a position immediately before contact, a resin-coated steel pipe having good surface properties can be obtained stably and easily, and the present invention has been completed.

  FIG. 1 is a diagram showing a configuration of a resin-coated steel pipe manufacturing apparatus according to the present invention. The apparatus for producing a resin-coated steel pipe includes a die head 1 and a water cooling device 2. The die head 1 includes a cylindrical through hole 1a, and can extrude the film-like resin 3 concentrically with respect to the through hole 1a. The steel pipe 4 is penetrated concentrically through the through hole 1 a, and the resin 3 is extruded concentrically with the steel pipe 4. The water cooling device 2 includes a plurality of cooling water nozzles 2 a and ejects cooling water 2 b toward the resin 3.

  By transporting the steel pipe 4 in the extrusion direction of the resin 3 and passing the steel pipe 4 through the through-hole 1a of the die head 1 that extrudes the resin 3, the outer periphery of the steel pipe 4 can be coated with the resin 3. The steel pipe 4 is transported using a transport roller (not shown) and transported along the longitudinal direction of the steel pipe 4. The resin 3 extruded from the die head 1 approaches the outer peripheral surface of the steel pipe 4 while being reduced in a conical shape, and comes into contact with the outer peripheral surface of the steel pipe 4. An adhesive may be applied to the outer peripheral surface of the steel pipe 4 before the resin 3 is coated. As the resin 3, for example, polyolefin such as low density polyethylene, high density polyethylene, and polypropylene can be used.

  FIG. 2 is a perspective view of the water shielding member. The apparatus for manufacturing a resin-coated steel pipe includes a water shielding member 5. The water shielding member 5 has a circular through hole 5a. The water shielding member 5 is disposed so that the steel pipe 4 passes through the through hole 5a. The water shielding member 5 is made of a plate-like elastic material. As a result, the inner peripheral surface of the water-impervious member 5 (the inner edge formed by the through hole 5 a) elastically contacts the outer peripheral surface of the resin 3.

  The water-impervious member 5 is disposed upstream of the position B where the resin 3 contacts the outer peripheral surface of the steel pipe 4 in the steel pipe conveyance direction. The water-impervious member 5 is movable in the steel pipe conveyance direction. At the start of operation, the water shielding member 5 is disposed downstream of the position B in the steel pipe conveyance direction, and the water shielding member 5 is moved to a predetermined position after the operation is stabilized.

  Cooling water nozzles 2 a are arranged above and below the steel pipe 4 on the downstream side of the water shielding member 5 in the steel pipe conveyance direction. The cooling water nozzle 2a is arranged such that the cooling water 2b ejected from the cooling water nozzle 2a needs to cool the downstream side in the steel pipe conveying direction of the resin 3 from the position C where the water shielding member 5 contacts the outer peripheral surface of the resin 3. A position corresponding to a predetermined range up to the position to be set.

  The cooling water nozzle 2a is also movable. As described above, the water-impervious member 5 is disposed downstream of the position B in the steel pipe conveyance direction from the start of operation until the operation is stabilized. Meanwhile, the cooling water nozzle 2a is retracted to a position where it does not collide with the water shielding member 5. After the operation is stabilized and the water shielding member 5 is moved to a predetermined position, the cooling water nozzle 2a is moved to a predetermined position.

  The diameter of the through hole 5 a of the water shielding member 5 is set so that the entire circumference is in contact with the outer peripheral surface of the resin 3. The through hole 5a elastically contacts the outer peripheral surface of the resin 3 without applying an excessive load, and expands when contacting the outer peripheral surface of the resin 3. Therefore, the diameter of the through hole 5a is equal to that of the outer peripheral surface of the resin 3. The diameter is set to be equal to or smaller than the diameter of the resin 3 in the contact portion.

  The cooling water nozzle 2 a is arranged so that the cooling water 2 b hits the contact position C between the water shielding member 5 and the resin 3. Further, the water shielding member 5 is disposed upstream of the position B where the resin 3 contacts the outer peripheral surface of the steel pipe 4 in the steel pipe conveyance direction. Thereby, the cooling of the resin 3 can be reliably started from the position C upstream of the position B in the steel pipe conveyance direction. That is, the contact position C between the water shielding member 5 and the outer peripheral surface of the resin 3 is the cooling start position of the resin 3.

  Since the water shielding member 5 is disposed upstream of the position B where the resin 3 contacts the outer peripheral surface of the steel pipe 4 in the steel pipe conveying direction, the resin 3 is sandwiched between the steel pipe 4 and the water shielding member 5 and is pressed down. There is nothing. Therefore, the steel pipe 4 can be covered without generating irregularities, wrinkles and wrinkles on the surface of the resin 3. Further, even if the cooling water 2 b jumps, the cooling water 2 b is shielded by the water shielding member 5 and does not reach the die head 1. Therefore, the temperature fluctuation of the die head 1 can be suppressed, and the resin 3 can be extruded stably. Thus, according to the apparatus for producing a resin-coated steel pipe of the present invention, a resin-coated steel pipe having a good surface property can be obtained stably.

  Here, let L be the distance from the position A at the downstream end of the die head 1 in the steel pipe conveying direction to the position B at which the resin 3 extruded from the die head 1 contacts the outer peripheral surface of the steel pipe 4. At this time, the position C where the water-impervious member 5 and the resin 3 are in contact is a position (2/3) × L on the downstream side in the steel pipe conveying direction of the position A, and a position of 20 mm on the upstream side in the steel pipe conveying direction of the position B. It is preferable to arrange the water-impervious member 5 so as to be between b.

  When the water shielding member 5 is arranged so as to be in contact with the outer peripheral surface of the resin 3 on the upstream side in the steel pipe conveying direction from the position a, the resin 3 is in contact with the outer peripheral surface of the steel pipe 4 because the cooling start time of the resin 3 is too early. Since it hardens | cures excessively before doing, wrinkles generate | occur | produce in the axial direction of the steel pipe 4 in the resin 3 coat | covered with the steel pipe 4. FIG.

  In order to improve the surface quality of the resin 3, the water-impervious member 5 is located as close as possible to the position B where the resin 3 contacts the outer peripheral surface of the steel pipe 4 on the upstream side in the steel pipe conveyance direction. preferable. However, it is difficult to stabilize the position where the resin 3 contacts the outer peripheral surface of the steel pipe 4 at a certain position during operation. The position b is set to a position of 20 mm upstream of the position B in the steel pipe conveyance direction in consideration of the influence of fluctuations in the position where the resin 3 comes into contact with the outer peripheral surface of the steel pipe 4.

  The water shielding member 5 is preferably a sponge made of polyurethane. By making the water-impervious member 5 into a sponge, the shielded cooling water 2b is temporarily held in the water-impervious member 5 and then supplied to the entire circumference of the resin 3, so that the resin 3 is more evenly distributed. It can cool from the position (position C) which contacts with, ie, the position where the resin 3 contacts the outer peripheral surface of the steel pipe 4, from the upstream side in the steel pipe conveying direction. Moreover, generation | occurrence | production of the wrinkle in the surface of the resin 3 by contact with the water-impervious member 5 can be suppressed by making the water-impervious member 5 into sponge.

  As shown in FIGS. 1 and 2, the water shielding member 5 preferably has a shape that gradually becomes thinner from the outer peripheral portion to the through hole 5 a. By adopting such a shape, while maintaining the strength of the water shielding member 5, the strength of the portion that contacts the resin 3 is reduced, and damage to the resin 3 due to contact and generation of wrinkles on the surface of the resin 3 are suppressed. can do.

  In order to confirm the effect of the production apparatus for the resin-coated steel pipe of the present invention, the following production tests were conducted and the results were evaluated.

1. Test conditions The apparatus shown in FIG. 1 was used as a resin-coated steel pipe manufacturing apparatus. The dimensions of the steel pipe used were an outer diameter of 89.1 mm, a wall thickness of 4.2 mm, and a length of 5500 mm. An asphalt adhesive was applied to the surface of the steel pipe in advance so that the thickness was 0.3 mm. The resin coated on the steel pipe was low density polyethylene, and the target thickness at the time of coating was 0.6 mm. The conveyance speed of the steel pipe was 15 m / min. The distance L shown in FIG. 1 was 450 mm.

  The cooling start position was as shown in Table 1 based on the position (position B) where the resin contacts the outer peripheral surface of the steel pipe. The cooling start position with the cooling water in Test Nos. 1 to 4 coincides with the position (position C) at which the water shielding member and the resin contact. As the water shielding member, a sponge made of polyurethane was used.

  Test numbers 1, 2 and 4 are comparative examples. In test number 1, the cooling start position was set at a position 300 mm downstream of the position B in the steel pipe conveyance direction.

  In test number 2, the cooling start position was closer to position B than test number 1 and was 20 mm downstream from the position B in the steel pipe conveyance direction. In Test No. 4, the cooling start position was 300 mm upstream from the position B in the steel pipe conveyance direction and a position close to the die head.

  Test number 3 is an example of the present invention, and the cooling start position was set to a position 20 mm upstream of the steel pipe conveyance direction from position B that satisfies the provisions of the present invention.

2. Test results The evaluation of the test results was the surface state of the resin observed visually. The evaluation is shown in Table 1 together with the cooling start position. In all the comparative examples, the surface condition of the resin was unsatisfactory. In test number 1, since the cooling start time was late and contacted with the transport roller before the start of cooling, wrinkles were generated on the surface of the resin due to contact with the transport roller, and streaks were formed in the circumferential direction of the steel pipe due to the pulsation of the cooling water. Unevenness occurred.

  In Test No. 2, since the uncooled resin was sandwiched between the steel pipe and the water-impervious member, the resin was subjected to a reduction by the steel pipe and the water-impervious member due to the vibration of the steel pipe, and indentations were locally generated. In test number 4, since the cooling start time was too early, the resin hardened excessively before coming into contact with the outer peripheral surface of the steel pipe, and after the contact with the outer peripheral surface of the steel pipe, wrinkles in the steel pipe axial direction occurred.

  On the other hand, in the test number 3 of the present invention example, the surface condition of the resin was good. Further, the cooling water was not applied to the die head, and the resin could be extruded stably.

  According to the apparatus for producing a resin-coated steel pipe of the present invention, a resin-coated steel pipe having a good surface quality can be obtained stably and easily.

1: die head, 1a: through hole of die head, 2: water cooling device,
2a: Cooling water nozzle, 2b: Cooling water, 3: Resin, 4: Steel pipe, 5: Water shielding member,
5a: Through-hole of water shielding member

Claims (4)

An apparatus for producing a resin-coated steel pipe for coating a thermoplastic resin on the outer peripheral surface of a steel pipe,
A transport roller for transporting the steel pipe along the longitudinal direction;
A die head that penetrates the steel pipe and extrudes the resin concentrically with the steel pipe;
A water-impervious member disposed on the upstream side of the steel pipe conveyance direction from a position where the resin contacts the outer peripheral surface of the steel pipe, and elastically contacts the outer peripheral surface of the resin;
It is arrange | positioned in the steel pipe conveyance direction downstream of the said water-impervious member, and toward the said resin so that water cooling of the said resin is started from the steel pipe conveyance direction upstream rather than the position where the said resin contacts the outer peripheral surface of the said steel pipe. An apparatus for producing a resin-coated steel pipe, comprising: a water-cooling device that ejects water. In the manufacturing apparatus of the resin-coated steel pipe according to claim 1,
When the distance from the position of the end of the die head on the downstream side in the steel pipe conveyance direction to the position where the resin contacts the outer peripheral surface of the steel pipe is L,
The water shielding member has a position (2/3) × L from the position of the end of the die head on the downstream side in the steel pipe conveyance direction to the downstream side in the steel pipe conveyance direction, and the resin is located on the steel pipe. An apparatus for producing a resin-coated steel pipe, which is arranged so as to be within a range between a position in contact with the outer peripheral surface and a position of 20 mm upstream of the steel pipe conveyance direction. In the manufacturing apparatus of the resin-coated steel pipe according to claim 1 or 2,
The said water cooling apparatus is a manufacturing apparatus of the resin coated steel pipe which is a nozzle which ejects a water flow from the upper direction and the downward direction at least from the said resin. In the manufacturing apparatus of the resin-coated steel pipe according to any one of claims 1 to 3,
The apparatus for manufacturing a resin-coated steel pipe, wherein the water shielding member is a sponge made of polyurethane.

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